Transcript
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CHAPTER 1
INTRODUCTION
1.1 Background The oyster mushroom, Pleurotus ostreatus is a common edible mushroom from the Kingdom
Fungi, Phylum Basidiomycota, Class Agaricomycetes, Order Agaricales and Family
richolomataceae. It was first cultivated in Germany during the year 1917 as a subsistence
measure during World War I and is now grown commercially around the world for food. Total
mushroom production worldwide has increased more than 18-fold in the last 32 years, from
about 350,000 metric tons in 1965 to about 6,160,800 metric tons in 1997. The bulk of this
increase has occurred during the last 15 years. A considerable shift has occurred in the composite
of genera that constitute the mushroom supply.
Oyster mushrooms are also known as Pleurotte. These oyster mushrooms get their name from
their oyster shell-like shape. They are white, light tan or ivory colored with a large, fan-like cap
and a smooth stem. Since these tender mushrooms have a delicate flavor, it is best to prepare
them simple so that the flavor is not overpowered. They usually grow on trees and fallen logs in
spring, summer, fall and during warm spells in winter. Oyster mushroom (P. ostreatus) contains
23.5 % Protein, 2.6 % Lipid, 39.4% Carbohydrate, 27.0 % Fiber and 7.4 % Ash. It is a rich
source of protein.
Dry matter of mushrooms is very low, usually in the range of 60–140 g/kg. Commonly, dry
matter content of 100 g/kg has been used for calculations if the factual value is unknown. Such
high water content and water activity affect the texture and participate in the short shelf life of
fruiting bodies. Mushrooms are rich in essential nutrients like vitamins, minerals, fiber,
antioxidants and water. They also boast the following properties: Mushrooms have little sodium
and fat and zero cholesterol. They are rich in vitamins of the B group: riboflavin, niacin, folate,
pantothenic acid, thiamin and B 6. The mushroom is the only vegetarian source of vitamin D in
edible form. Antioxidants in mushrooms include ergothioneine. Mushrooms are a powerhouse of
minerals, including potassium, copper, zinc, selenium, iron, magnesium, phosphorus and
calcium. A medium mushroom has more potassium than a glass of orange juice or a banana. A
serving of mushrooms supplies 40-60% of the daily copper requirement. Selenium is mainly
found in animal proteins, so the mushroom is the best source of selenium for vegetarians. The
source of the antibiotic penicillin, mushrooms have natural antibiotics with anti-fungal and anti-
microbial properties.
The combination of low fat and carbohydrates and zero cholesterol with high proteins, vitamins,
minerals, water and fiber makes mushrooms ideal for diabetics. Moreover, mushrooms contain
natural insulin and enzymes which break down the starch and sugar in food. Finally, certain
compounds stimulate the endocrine glands and the formation of insulin. Mushrooms are
beneficial for patients of hypertension, as they control the blood pressure. They are known to
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control migraines and even some mental disorders. Niacin helps to prevent Alzheimer's and other
cognitive disorders. Natural antibiotics in mushrooms guard against infections and hasten healing
of wounds. Mushrooms are good for weight loss, while helping to build muscle mass.
Mushrooms not only have their own flavor which intensifies during cooking, but can absorb the
flavor of other ingredients. They can be used as appetizers, added to salads, soups, stews and
sandwiches. However, it is essential to identify mushrooms correctly, as the poisonous species
look similar to the edible kind. Moreover, some edible ones can be poisonous, depending on
where they are grown. One must buy mushrooms from trusted vendors. Mushrooms are rich in
vitamins, minerals, amino acids, fiber and antioxidants. They have curative and preventive
properties and contribute to all round good health.
Finger millet is important millet grown extensively in various areas of India and Africa. It is
nutritionally important because of its high calcium, iron and dietary fibre, compared to cereals
such as barley, rice, maize and wheat. Although fat content is low, ragi is high in polyunsaturated
fatty acids. Since finger millet is processed as a whole grain (i.e. without dehusking), it retains
the fiber, minerals, vitamins and phenolics present in the outer layer of grain, which are
nutritionally beneficial (Pednekar et al, 2009).
Barley (Hordeum vulgare vulgare L.) is an ancient and important cereal grain crop. It ranks fifth
among all crops in dry matter production in the world today (129 M mt, 2002–2005 mean)
behind maize (Zea mays, 605 M mt), wheat (Triticum spp., 549 M mt), rice (Oryza sativa, 424 M
mt), and soybean (Glycine max, 175 M mt), and ahead of sugar cane (Saccharum spp., 92 M mt),
potato (Solanum tuberosum, 60 M mt), and sorghum (Sorghum bicolour, 50 M mt), (FAO,
2007). Barley was presumably first used as human food but evolved primarily into a feed,
malting and brewing grain due in part to the rise in prominence of wheat and rice. In recent
times, about two-thirds of the barley crop has been used for feed, one-third for malting and about
2% for food directly. However, throughout its history, it has remained a major food source for
some cultures principally in Asia and northern Africa. Barley is arguably the most widely
adapted cereal grain species with production at higher latitudes and altitudes and farther into
deserts than any other cereal crop. It is in extreme climates that barley remains a principal food
source today, e.g., Himalayan nations, Ethiopia, and Morocco.
The mixed linkage (1→3)(1→4)-β-D-glucans (β-glucan) from the endosperm of cereal grains are
valuable industrial hydrocolloids and have been shown to be important, physiologically active
dietary fiber components. β-glucans are water-soluble, linear, high molecular-weight
polysaccharides. They give viscous, shear thinning solutions even at low concentrations. The
viscosity is related to the molecular weight and is strongly dependent on concentration (Lyly et
al, 2004). The good viscosity forming properties make β-glucans potential alternatives as
thickening agents in different food applications, e.g. ice creams, sauces and salad dressings.
Barley flour can be used as an ingredient for the preparation of soup powder.
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Extrusion cooking is an important and popular food processing technique. Cereals are common
ingredients in extruded products and barley flour has been incorporated into some extruded
human. Extrusion cooking has been used for processing breakfast cereals, pasta products,
dextrinized flour, etc. Some of the advantages that have been attributed to this technique include
low cost, high productivity, versatility and unique product shapes. Depending on the intended
final product, various temperatures, moisture, shear and screw speed combinations can be used.
Extrusion cooking of starchy grain flours causes gelatinization of starch among other physico-
chemical and functionality changes the grain components undergo.
Mushroom soups available in the market contain not more than 2% dry mushroom. Since
mushroom is rich in protein (23.2±0.5%), an increased amount of mushroom powder also adds
high nutritional values to the soup. In an addition, Barley and Ragi flour can also enhances crude
fiber content in food materials.
In this study, Oyster mushrooms were used to prepare for extruded product rich in protein and
crude fiber. Barley and Ragi flour were also used in order enhance the nutritional attributes in the
final product. The product was rich in protein and also, due to gelatinization of starch, the
properties of Barley flour, Ragi flour and mushroom powder was changed.
1.2 Objectives:
Based on above considerations the present investigation was undertaken with the following
objectives:
1. To develop protein enriched ingredient for the preparation of mushroom soup powder using
twin screw extruder.
2. To optimize the process parameters for the preparation of the mushroom soup ingredient.
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CHAPTER III
REVIEW OF LITERATURE
This chapter reviews the research work carried out by various researchers in related areas viz.
extrusion cooking, extruded characteristics like hardness and water solubility index, response
surface methodology in process variable optimization and sensory evaluation.
2.1 Principle of Extrusion Cooking
Extrusion cooking is a versatile process that combines several unit operations including mixing,
shearing, conveying, heating, puffing and partial drying, depending on the extruder design and
process conditions. Extrusion cooking plays an important role in the production of snack foods
as well as breakfast cereals, modified flours and sweets. Extrusion is a cooking and shaping
process designed to give unique physical and chemical functionality to food materials. High
pressures and temperatures are common in cooking extruders, thereby causing changes in the
physical and chemical properties of extruded starch. The effects of extrusion on water solubility
and water absorption of starch have been studied extensively (Anderson et al., 1969). Food
extrusion is a process in which food ingredients are forced to flow, under one or several
conditions of mixing, heating and shear, through a die that forms and puff dries the ingredients
(Rossen and Miller, 1973). Extrusion cooking has some unique features compared to other heat
processes, because the material is subjected to intense mechanical shear. It is able to break
covalent bonds in biopolymers, and the intense structural disruption and mixing facilitate
reactions otherwise limited by dilution of reactants and products. The nutritional value in
vegetable protein is usually enhanced by mild extrusion cooking conditions, due to an increase in
digestibility. This may be due to protein denaturation, and inactivation of protease inhibitors
present in the raw plant foods. Extrusion cooking, as a heat treatment affects and alters the nature
of many food constituents, including starches and proteins, by changing physical, chemical and
nutritional properties. It has become a mature process for many applications in the food industry.
In the food industry, high temperature–short time extrusion cooking is used to produce direct
expanded products such as snacks, breakfast cereals and pet foods.
2.2 Advantages of Extrusion Cooking
a) It is versatile.
b) It facilitates high productivity.
c) It gives high quality products.
d) There is a possibility of giving different product design and shape.
e) There is absence of effluents during processing
f) It improves the functional characteristics of protein source without losing the protein quality
provided if right sets of process variables used.
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g) From the nutritional point of view protein from by-products like waste of traditional food
industry or new agronomics species of several grains that have not been consume because of
their acceptability. It can be reversed by extrusion through extruder.
2.3 Extruders
Extruder is primarily a screw pump, and is capable of performing mixing, heating, cooking and
shaping. In principle, it is a high-temperature short-time reactor based on mechanical and
thermal energy input, and usually combined with a structuring and shaping step at the die exit.
Feed ingredients during their movement inside the screw are transformed to continuous plastic
dough. The barrel is externally heated by either steam or electric heaters. Upon heating and
working during extrusion process, macromolecules in food ingredients lose their native,
organized tertiary structure and form continuous viscous dough. The laminar flow within the
channels on the extrusion screw and the die aligns the large molecules in the direction of the
flow, exposing bonding sites which leads to cross-linking and formed, expandable structure that
creates the crunchy texture in fabricated foods. Food extruders can be visualized as devices that
can transform variety of raw ingredients into intermediate and finished products. Food extruders
can perform one or several functions at the same time while processing food or feed: mixing,
homogenization, grinding, shearing, starch cooking, protein denaturation, texture alteration,
enzyme inactivation, pasteurization and sterilization, cooking, shaping products, expansion and
puffing, agglomerating ingredients dehydration and unitizing (Riaz, 2000).
2.4 Characteristics of Extruded Products
a) Degree of expansion on exit from the extruder.
b) Bulk density.
c) Mechanical Properties.
d) Internal Microstructure.
e) Protein quality.
f) Starch characteristics.
g) Degree of cook.
Altan et al. (2008) evaluated effect of extrusion parameters on the quality of tomato pomace-
Barley blend. The results showed that varying levels of tomato pomace could be incorporated
into an extruded barley snack depending on the desired texture of the final product. Extrudates
with 2% and 10% tomato pomace levels extruded at 1600C and 200 rpm had higher preference
levels for parameters of color, texture, taste and overall acceptability. Such extrusion would also
provide another avenue for tomato pomace utilization.
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2.5 Mushrooms
Adejumo and Awosanya (2004) determined the proximate and mineral composition of four
edible mushroom species from South Western Nigeria. Results of proximate analysis of four
edible species of mushroom indicate that Termitomyces mammiformis was a very good source
of crude protein (37%), crude fiber (7%), ash (10%), calcium (216 g/kg dry weight) and
manganese (136 mg/kg dry weight (dw)). Russula vesca was the richest in carbohydrate (71%)
and magnesium (14 g/kg), while Lactarius triviralis was richest in moisture content (37%), iron
(1230 mg/kg) and copper (8 mg/kg). It is also a good source of carbohydrate (64%), calcium
(210 g/kg) and manganese (120 mg/kg). Lentinus tigrinus was, however, the richest in dry matter
(94%), and is also rich in carbohydrate (62%), magnesium (11 g/kg) and copper (6 mg/kg). It
was observed that lipids, sodium and phosphorus contents of the four species were generally
very low.
Tons of wild growing mushroom species have been widely consumed as a delicacy by part of the
European population. The credible evaluation of their nutritional value has so far been limited,
due to the fragmentary knowledge of their composition and mainly due to the poor information
on the bioavailability of their constituents. Dry matter content is very low, commonly about 100
g/kg. A low proportion of lipid and glycogen results in a low energy value. Relatively high
proportion of insoluble fiber, comprised of chitin and other structural polysaccharides, seems to
be nutritionally profitable. The proportion of essential amino acids is contributive, while that of
�n 3 fatty acids is nutritionally negligible. The contents of potassium and phosphorus are higher
than in most vegetables. Relatively high ergosterol content could be of significance for
individuals with a low intake of ergocalciferol. Some mushroom species have relatively high
antioxidant capacity. Specific b-glucans have been studied for pharmacological use (Kalac,
2009).
2.5 Drying of Mushroom
Chen and Chen (1974) studied the effects of dehydration on the volume contraction of
Muahrooms. The experimental results showed that the the volume shrinkage of the sliced
mushrooms was a linear function of moisture content in the range from an initial moisture
content of 15.66 g/g of dry solid (or 94% moisture content) down to about 0.1 g/g (or about 9%
moisture content). The shrinkage curve was made based on the experimental data and it was
compared with the computed data. The model fitted reasonably well. The empirical equation was
substantiated by a recent theoretical derivation.
Brennan et al. (2000) studied the effect of post-harvest treatment with citric acid or hydrogen
peroxide on the Shelf Life of Fresh Sliced mushrooms. In this study, whole fresh mushrooms
were soaked for 10 min in solutions of citric acid or hydrogen peroxide, then sliced, packed and
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stored at 40C for up to 19d. Both treatments reduced the number of pseudomonad bacteria and
improved the keeping quality of the sliced mushrooms when compared to control (water soaked)
slices. A specification of 75 Hunter L units was established to quantify sliced mushroom shelf
life and this showed that the treatments extended the shelf life by about 50%. Treatment
effectiveness varied with mushroom batch, with first and third flush mushrooms from phase III
compost responding better than mushrooms from phase II compost and second flush. The citric
acid treatment had no deleterious effect on the sensory properties of sliced mushrooms
Bergstrom (2006) studied wheather enzymatic pretreatment of Shiitcake Mushroom enhance the
extraction process of valuable substance eritadenine. The results obtained with enzymatic pre-
treatment showed deterioration compared to extraction without enzyme treatment.
Giri and Prasad (2007) evaluated Microwave-vacuum dehydration characteristics of button
mushroom (Agaricus bisporus) in a commercially available microwave oven (0–600 W)
modified to a drying system by incorporating a vacuum chamber in the cavity. The effect of
drying parameters, namely microwave power, system pressure and product thickness on the
drying kinetics and rehydration characteristics were investigated. The drying system was
operated in the microwave power range of 115–285 W, pressure range of 6.5–23.5 kPa having
mushroom slices of 6–14 mm thickness. Convective air drying at different air temperatures (50,
60 and 700C) was performed to compare the drying rate and rehydration properties of
microwave-vacuum drying with conventional method. Microwave-vacuum drying resulted in
70–90% decrease in the drying time and the dried products had better rehydration characteristics
as compared to convective air drying. The rate constants of the exponential and Page’s model for
thin layer drying were established by regression analysis of the experimental data which were
found to be affected mainly by the microwave power level followed by sample thickness while
system pressure had a little effect on the drying rate. Rehydration ratio was significantly affected
by the system pressure. Empirical models were also developed for estimating the drying rate
constant and rehydration ratio as a function of the microwave-vacuum drying process
parameters.
Srivastava et al. (2009) explained the effects of blanching methods on the drying kinetics of
Oyster mushroom. In this study, Oyster mushroom was treated with hot water and steam
blanching prior to drying in cabinet dryer. A hot air cabinet dryer was used for drying mushroom
at 40, 50, 60, 70 and 80°C temperatures. Solid loss was observed to be 25.46% and 3.32% (wb)
during hot water and steam blanching, respectively. Highest drying rate was observed for hot
water blanched mushroom followed by unblanched and steam blanched mushroom. This leads to
more drying time for the steam blanched mushroom followed by the unblanched and hot water
blanched mushroom for the same level of drying. The drying data was modeled for exponential
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and Page's drying model. Page's model was found to be better than the exponential model for the
prediction of drying rate. The value of the model parameters of the exponential model was found
to be higher than that of Page's model. The effective moisture diffusivity (De) was determined at
different temperatures and found to be maximum for the hot water blanched mushroom and
minimum for the steam blanched mushroom. The effective moisture diffusivity (De) increased
with increase in temperature. The activation energy of hot water blanched, unblanched and steam
blanched mushroom was estimated to be 25.324, 17.113 and 21.165 kJ/mol, respectively.
Lombrana et al. (2010) studied the drying of sliced mushroom by microwave energy for different
operational conditions related to temperature control position and pressure and their effects on
drying kinetics and quality. Thinly sliced mushrooms were dried in a guide cavity by applying
microwave energy at 2.45 GHz. The influence on the quality of the dehydrated mushrooms was
studied by two different techniques: sorption isotherms (Halsey and B.E.T. equations) and
scanning electron microscopy (SEM). Drying kinetics was also analyzed through the
determination of diffusivity by applying a mathematical model that takes into account changes in
moisture on the product surface during the process. Thus, the results of SEM observations and
quality can be linked with diffusivity values in each experiment. As a rule, the operational
conditions imposed result in contrary tendencies in quality and drying kinetics. High heat levels
usually lead to unfavorable quality results in the dehydrated product if not corrected with a
favorable inverse temperature gradient characteristic of microwave heating.
Zecchi et al. (2011) studied on the modeling and minimizing of the combined convective and
vacuum drying process of Parsley and Mushroom. The highest temperature assayed in this study,
at which drying could be performed without appreciable visual damage was 450C for parsley and
550C for mushrooms. For parsley, an important reduction of process time was achieved when
convective and vacuum drying at the maximum suitable drying temperature (450C) was
combined. For mushrooms, when drying was performed at the maximum temperature the most
appropriate technology was the dehydration process in a convective dryer, because the reversion
of the processes’ rates did not occur for this product and temperature.
2.6 Ragi
Nirmala et al. (2000) studied on a recently released hybrid ragi, Indaf-15. It was germinated up
to 96 h at 25 and the sprouts, drawn at 24 h intervals, were dried, devegetated, powdered and
evaluated for malting loss, reducing sugar, free sugar profile, starch content, dietary fiber and an
array of carbohydrate-degrading enzymes. Malting loss was maximum (32.5%) at 96 h. The total
reducing sugar content increased from 1.44 to 8.36%, whereas the total carbohydrate content
decreased from 81 to 58% at 96 h of germination. Analysis of 70% alcohol- soluble sugars
revealed glucose, fructose and sucrose in different proportions with respect to germination time.
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Maltose and mal- totriose were detected after 48 and 72 h, respectively. There was a linear
decrease in starch content (from 65 to 43%). Activities of amylase and pullulanase were
maximum at 72 h whereas those of a-d-glucosidase and 1,3-b-d-glucanase, were maximum at 48
h. Xylanase activity was maximum at 96 h with a concomitant decrease in arabinose to xylose
ratio from 1:1 to 1:0.38 in the dietary fiber. a-Galactosidase activity was negligible, which is in
tune with a very small amount of raffinose series oligosaccharides. The above results indicated
that Indaf-15 is a potential variety for malting purposes as it develops high levels of amylases
during germination, and its malt form is a rich source of reducing sugar.
Subba Rao, and Muralikrishna (2001) studied the nature of non-starch polysaccharides (NSP)
and bound phenolic acids from native and malted ragi using a recently- released hybrid variety of
ragi, (Indaf-15). Yields of water-soluble NSP, hemicellulose-B and cellulose polysaccharides
increased upon malting whereas a substantial decrease in the yield of hemicellulose-A was
observed. Hemicellulose-B is the most viscogenic and its relative viscosity decreased from 3.04
to 1.98 upon 96 h of malting, whereas the solubility and viscosities of the rest of the NSP
increased upon malting. The major sugars identified in all the NSP fractions were arabinose,
xylose, galactose and glucose. A one- to two-fold decrease in arabinose was observed in all the
NSP upon malting except for the alkali-insoluble residue wherein a decrease of glucose was
observed. A progressive decrease in the pentose to hexose ratio was observed, indicating mainly
pentosan degradation during malting, whereas an increase in the pentose to hexose ratio was
observed in the alkaline-insoluble residue (AIR). Ferulic, ca eic and coumaric acids were
identified as the major bound phenolic acids in native ragi and one- to two-fold decrease was
observed in their contents after 4 days of malting.
2.7 Barley
Lyly et al. (2004) studied the effect of concentration and molecular weight of two oat and one
barley b-glucan preparation on the perceived sensory quality of a ready-to-eat soup prototype
before andafter freezing. Oat1 was a bran-type preparation containing high molecular weight b-
glucan; Oat2 and Barley were more processed and purified preparations with lower molecular
weight. Nine soups containing 0.25–2.0 g b-glucan/100 g soup and one reference soup thickened
with starch were profiled by a sensory panel and their viscosity and molecular weight of b-
glucan was analyzed. Freezing had no notable effects on the sensory quality of the soups. At the
same concentration, soups made with the bran-type preparation were more viscous and had
higher perceived thickness than soups made with processed, low molecular weight preparations.
Barley soups had mainly higher flavour intensities than oat soups. Good correlations were
obtained between sensory texture attributes and viscosity (r=0.70–0.84; Pp0.001) and moderate
correlations between flavour attributes and viscosity �(r= 0.63–�0.80; Pp0.001).
Technologically, b-glucans are feasible thickening agent alternatives in soups. Preparations with
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lower molecular weight and viscosity are easier to add into a food product in higher quantities,
but the role of high molecular weight b-glucan in physiological functionality has to be kept in
mind.
2.8 Extrusion process
Rinaldi et al. (1995) found that okara is the residue left after soymilk or tofu production and used
either as animal feed, fertilizer, or landfill. The purpose of this study was to use wet okara to
produce and enrich extruded cereal products and to study the effects of extrusion on the dietary
fiber and isoflavone contents. Wet okara was combined with soft wheat flour to produce two
different formulations (33.3 and 40% okara) and extruded using four combinations of two screw
configurations and two temperature profiles. Various physicochemical properties were analyzed.
The radial expansion ratio decreased as fiber content increased. On the other hand, both bulk
density and breaking strength increased as fiber content increased. Combining okara with soft
wheat flour resulted in increased protein, dietary fiber, and isoflavone contents compared with
soft wheat flour alone. Extrusion of the formulations resulted in decreased insoluble fiber and
increased soluble fiber contents of extrudates. Extrusion decreased the total detectable
isoflavones and altered the distribution of the six detected isoflavones. The overall results
indicate that by using a novel twin-screw extrusion process to cook, sterilize, and remove the
major portion of water, wet okara can successfully be used to make and enrich extruded
products.
Pansawat et al. (2008) concluded that increasing feed moisture and screw speed decreased
pressure at the die. Increased screw speed increased product temperature at the die but
increased feed moisture lowered it. Increased barrel temperature, feed moisture and screw
speed decreased motor torque. Increased screw speed increased specific mechanical energy,
while increased feed moisture reduced it. Longer mean residence times were observed at lower
screw speeds. Product density increased as feed moisture increased, but decreased with screw
speed. Increased feed moisture decreased radial expansion.
Valentina et al. (2009) investigated the effect of different levels of feed moisture (12-17%)
during extrusion cooking; using a co-rotating twin-screw extruder on selected nutritional and
physical properties of extruded products. Four different formulations were used based on wheat
flour and corn starch with the addition of 10% brewer’s spent grain (BSG) and red cabbage (RC)
trimming reducing the flour and starch. The samples were: wheat flour + BSG (WBSG), corn
starch + BSG (CBSG), wheat flour + red cabbage (WRC) and corn starch + red cabbage (CRC).
Process conditions utilized were: constant feed rate of 25 kg/h, screw speed 200 rpm and barrel
temperature of 80 and 120° C. The results indicated that increasing the water feed to 15%
increased the level of total dietary fiber (TDF) in all the extrudates. Extrusion cooking increased
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the level of total antioxidant capacity (TAC) and total phenolic compounds (TPC) in WRC and
CRC. In addition to water feed level affecting the TDF of the extrudates, also affected were the
expansion ratio, bulk density, hardness, WSI, SME and colour. The protein level of the products
and hardness of extrudates were related to the different formulations.
Kumar et al. (2010) investigate with rice flour in different proportions (10-30%) to dehydrated
carrot pomace and pulse powder (CPPP) mixture having equal ratio. The formulation was
extruded at different moisture content (17-21%), screw speed (270-310 rpm) and die temperature
(110-130° C). The lateral expansion, bulk density, water absorption index, water solubility index,
hardness and sensory characteristics were measured as responses. Significant regression models
were established with the coefficient of determination, R2 greater than 0.72. The results indicated
that CPPP proportion and moisture content significantly influenced (P<0.10) lateral expansion;
temperature for water absorption index; screw speed and temperature for hardness and screw
speed for sensory score. The compromised optimum condition obtained by numerical integration
for development of extrudates were: CPPP mixture of 16.5% in rice flour, moisture content
19.23%, screw speed 310 rpm and die temperature 110°C. Sensory evaluation revealed that
carrot pomace could be incorporated into ready-to-eat expanded products upto the level of
8.25%.
2.9 Response Surface Method and Optimization Technique
RSM is a statistical procedure frequently used for optimization studies. It uses quantitative data
from an appropriate experimental design to determine and simultaneously solve multivariate
problems. RSM designs help in quantifying the relationships between one or more measured
responses and the vital input factors. The response surface method produces a mathematical
model that can be used to predict a response. The model equation describes the effect of the
test variables on the responses, determine interrelationships among test variables and represent
the combined effect of all test variables in the response. This approach enables an experimenter
to make efficient exploration of a process or system. Optimization of any process is searching
for a combination of factor levels that simultaneously satisfy the requirements of each of the
responses and factors. Simultaneous optimization of multiple responses can be performed
graphically or numerically.
Response surface methodology (RSM) explores the relationships between several explanatory
variables and one or more response variables. The method was introduced by Box and Wilson
(1951). RSM (Box and Hunter, 1957) is used to optimize the parameters based on several
responses.
Rotatable Central composite design (RCCD) is a response surface methodology for fitting a
second order model to a data set without the use of a complete 3k factorial experiment (Myers,
1971). After the necessary experimental data is created, multiple linear regressions are
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performed. Coded variables are to be used in this method.
Ainsworth (2004) used Response surface methodology to analyze the effect of screw speed
(220–340 rpm), feed moisture (11.0–15.0%, wet basis) and feed rate (22.0–26.0 kg/h, wet
basis) on the physical properties (i.e., bulk density, expansion, porosity) of a nutritionally
balanced extruded snack food. Regression equations describing the effect of each variable on
the responses were obtained. Responses were most affected by changes in screw speed
followed by feed moisture and feed rate (P<0.05).Expansion and porosity increased with screw
speed and feed moisture whereas the opposite was observed for bulk density. Radial expansion
was found to be a better index to measure the extent of expansion than the axial and overall
expansions, indicated by a higher correlation coefficient.
Ozer et al. (2004) used response surface methodology (central composite design) to analyze the
effect of screw speed (220-340 rpm), feed moisture (11-15% wb) and feed rate (22-26 kg/h) on
the physical properties (i.e., bulk density, expansion, porosity) of a nutritionally balanced
extruded snack food. Regression equations describing the effect of each variable on the
responses were obtained.
Pansawat et al. (2008) used RSM to study the effects of extrusion conditions (temperature,
screw speed and feed moisture) on secondary extrusion variables (product temperature,
pressure at the die, motor torque, specific mechanical energy input and mean residence time
and physical properties of the extrudate. Fractional factorial design was used in RSM study.
RSM is an empirical statistical modeling technique employed for multiple regression analysis
using quantitative data obtained from properly designed experiments to solve multivariable
equations simultaneously.
The main idea of RSM is to use a sequential experimental procedure to obtain an optimal
response. An easy way to estimate a first-degree polynomial model is to use a factorial
experiment or a fractional factorial design. This is sufficient to determine which explanatory
variables have an impact on the response variables of interest. Once it is suspected that only
significant explanatory variables are left, and then a more complicated design, such as a central
composite design can be implemented to estimate a second-degree polynomial model, which is
still only an approximation at best. However, the second-degree model can be used to optimize
(maximize, minimize, or attain a specific target for) a response.
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CHAPTER III
MATERIALS AND METHODS
In this chapter the description of raw materials used and the methodology adopted for conducting
various experiments for the extrusion of mushroom powder using twin screw extruder are
presented.
3.1 Raw Materials
3.1.1 Mushroom:
Raw oyster mushrooms were collected from the local market. It was washed with distilled water
and the extra water was drained. The surface moisture was soaked by wrapping the mushroom
with blotting paper. The stem parts were removed.
3.1.2 Hot Water Blanching of Mushroom
The washed mushrooms were hot water blanched. Hot water blanching method was chosen for
pretreatment because this process minimizes the drying time for mushrooms (Srivastava et al,
2009). At first, the washed mushrooms were wrapped in a Maslin cloth. Then the cloth was
immersed in the boiling water (100±5oC) and hold for 2 minutes. Then it was immediately
immersed in the chilled water. The extra water was drained by spreading on perforated
containers. The hot water blanching process of raw mushroom is shown in Fig 3.1
3.1.3 Drying of the mushrooms:
The drying of the mushroom was done in an convective hot air oven. The known quantities of
sample was loaded in perforated trays covered with filter papers in the oven by noting initial
weights and subjected to drying at 55±2oC. The initial temperature was maintained at 55oC for 1
h and then gradually was raised to maintain at 60±2oC till complete drying. The desired moisture
content of the dried sample was 10-12%. The hot air oven is shown in Fig 3.2.
3.1.4 Preparation of Powder:
The dried mushrooms were taken out from the dryer. Then the dried mushrooms were ground in
a laboratory mixer grinder. Then the yield was taken out from the mixer grinder and manually
ground in a hand mortar. The product was treated in a BS 25 sieve. The yield was approximately
80-85%. The powder thus obtained was packed in LDPE pouches and stored at 4oC.
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(a) (b)
(c)
Fig 3.1 Hot water blanching process of mushroom (a) Raw mushrooms
(b) Hot water blanching and (c) immersing in cold water
3.1.4 Ragi and Barley Flour
The ragi and Barley flour were purchased from the local market. They were treated in the same
sieve (BS 25). The yield was approximately 80-85% for both flours. Then each flour was packed
in LDPE pouches and stored at 4oC for future use.
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Fig 3.2 Hot Air Oven Drier for drying of Oyster Mushrooms
3.2 Sample preparation
The mushroom powder and ragi and barley flour mixture were mixed in desired proportion in a
food processor with mixer attachment. The moisture content of the formulation was estimated by
hot air oven method (Ranganna, 1997). The moisture was adjusted by sprinkling distilled water
in dry ingredients. The mixture was then passed through a 2 mm sieve to reduce the number of
lumps formed due to addition of moisture. After mixing, samples were stored in LDPE pouches
at room temperature for 24 h. The whole process has been shown in Fig 3.3
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3.3 Determination of Proximate Composition
Proximate compositions and nutritional properties of final products namely, moisture content,
protein, fat, crude fir content, carbohydrates, ash content required for the present investigation
were determined.
3.3.1 Moisture content
The moisture content of the final product was determined by hot air oven method as descrid by
Ranganna (1997). Weighed test sample (5g approx.) was kept in duplicate in hot air electric
oven at a temperature of 100±5°C for 24 h, after which it was kept inside a desiccators for
cooling to ambient temperature and the change in weight was noted. The moisture content was
expressed either in percent (wet basis) or kg moisture/kg dry matter (dry basis).
3.3.2 Fat content
Fat soluble material in a food was extracted from an oven-dried sample using a Soxhlet
extraction apparatus. The either or hexane was evaporated and the residue weighed.
Wt. of fat soluble materialFat content 100
Wt.of sample
3.3.3 Ash content and Crude Fiber content
It was determined according to AOAC (1984) method.
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Fig 3.3 Flow chart of the Process.
Raw Mushrooms
Washed under
Flowing Water
Hot Water
Blanching at
100±5 0C
Drying at 55 0C
Preparation of
Mushroom Powder
Preparation of
Mushroom Powder
Blend Preparation
with Ragi and
Barley Flour
Extrusion of Blend
Measurement of
Responses
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3.3.4 Protein content determination
Protein content was estimated from the crude nitrogen content of the sample determined by the
Kjeldahl method (N ×6.25), (AOAC, 1984).The digester, scrubr and dwastillation unit are shown
in Fig. 3.4 and Fig. 3.5 respectively.
Fig. 3.4 IR Digester Unit K-435 and Scrubr B-414.
Fig. 3.5 Dwastillation units (K-360).
3.3.5 Carbohydrates (by difference method)
The carbohydrate content was estimated by subtracting the values of moisture, protein, ash,
crude fat and crude fiber from 100.
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3.4 Extruder
The extruder used for this experimental purpose was BTPL make laboratory co-rotating twin-
screw extruder (EB-10 model) having L/D ratio of 14.4:1. The extruder was pre-assembled and
skid-mounted and placed on 3” raised platform. Raised platform helps cleaning beneath the
extruder. The extruder has shown in Fig. 3.6.
Fig.3.6 BTPL Lab Model (EB-10) Twin Screw Extruder.
1.Temperature sensor, 2.Heater, 3.Cutter motor, 4.Cutter casing, 5.Water circulation
pipe, 6.Feeder hopper, 7.Feeder motor, 8.Extruder motor, 9.Gear box, 10.Inching
and emergency stop button, 11.Barrel
3.4.1 Drive system
The main drive was provided with 10 hp motor (400 V, 3 ph, 50 Hz). It was provided with
SIEMENS / ABB. Frequency drive to control the rpm precisely according to the need of the
process. The output shaft of worm reduction gear was provided with a torque limiter coupling
consisting of torque limiter and roller chain type coupling. The torque limiter was a protective
device that limits torque transmitted by output shaft of worm reduction gear.
3.4.2 Extruder barrel
The barrel of extruder receives feed from co-rotating feeder fitted with Siemens make
frequency controller for obtaining variable speed. The barrel consists of two parallel co-
6.
7.
8.
9.
10.
11.
1.
2.
3.
4.
5.
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rotating screws driven by drive assembly. These screw lead material form feeding zone to die.
The co-rotating screws were of intermeshing types and as they rotate in the same direction, it
helps in self cleaning of screws. The twin screw assembly has shown in Fig. 3.8.
Fig. 3.7 Control panel for Twin screw extruder.
Fig. 3.8 Twin screw in head assembly. Fig. 3.9 Extruder die assembly.
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3.4.3 Feeder
The barrel of extruder receives the feed from a co-rotating feeder. The rated capacity of the
feeder was controlled by knob on control panel. The calibration chart was prepared for reading
feed rate in terms of flow rate in kg/h.
3.4.4 Heating arrangement
The extruder barrel was provided with three electric band-heaters (just fore die section,
kneading section and feeding section). The temperature sensors were fitted at each of three
sections, which were connected to temperature controller and digital output on control panel.
3.4.5 Extruder die
The die plate of die (either solid or split) fixed by a screwed nut tighten by a special wrench
provided. Extruder die has shown in Fig. 3.9.
3.4.6 Cutting knife
The automatic cutting knife was fixed on a rotating shaft of knife drive assembly. The cutter
was drive by a variable speed AC motor and it was controlled by frequency controller through
a knob provided on control panel. The automatic cutter assembly was covered by a hinged
safety guard.
3.4.7 Panel board
The extruder was provided with stand-alone type control panel. The control panel controls and
shows the extruder screw speed, barrel temperature, feed rate and cutter rpm. An electric
supply main switch (3 ph, 60 A, 400 V, 50 Hz AC) supply with neutral line had provided to
control panel. Control panel has shown in Fig. 3.7.
3.4.8 Water circulation
Three water jackets were connected to extruder barrel with water supply through solenoid
valve controlled through PID controllers. The outlets were connected to a delivery line leading
to outside drain. The water circulation starts when temperature of heaters exceeds desired limit.
3.4.9 Inching
Since, drive system in this extruder generates torque gradually, a bypass switch (installed at the
side of the desk) was provided to directly apply the drive from the motor which gives the
sudden application of torque necessary to clean the barrel from burn-out products. It was
imperative to remove dies fore applying direct drive from motor for inching device from motor
for inching device. This was essentially required to clean jamming in barrel which was a
special feature in this model.
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3.4.10 Emergency stop
The panel board was provided with an emergency stop switch. It should switched-off in case of
emergency such as entry of foreign object inside barrel.
3.5 Water Absorption Index (WAI) and Water Solubility Index (WSI)
The water absorption index (WAI) an indicator of the sample to absorb water, depends on the
availability of hydrophilic group which bind water molecules and on the gel forming capacity
of macromolecules measures the volume occupied by the granule or starch polymer after
swelling in excess of water. While water solubility index (WSI) was used as a measure for
starch degradation; it means that at lower WSI there was minor starch degradation of starch
and such condition leads to less numbers of soluble molecules in the extruded.
WAI and WSI were determined by the method of Anderson (1982). The extruded products
were milled to a mean particle size of 200–250 µm. A 2.5 g sample was dispersed in 25 g
distilled water, using a glass rod to break up any lumps and then stirred for 30 min at room
temperature. The dispersions were rinsed into tarred centrifuge machine, made up to 32.5 g and
then centrifuged at 2740 g (4000 rpm) for 15 min. The supernatant was decanted for
determination of its solid content and sediment was weighed. WAI and WSI were calculated
as:
Weight gain by gel
WAI = Dry weight of extrudte
WSI = X 100
3.8 Texture (Hardness)
The texture characteristics of extruded mushroom products and hardness were measured using
a stable micro system TA-XT2 texture analyzer (Texture Technology corp., UK) fitted with a
25 mm cylinder probs. The studies were conducted at a pre test speed of 1.0 mm/s, test speed
of 0.5 mm/s post test speed of 10 mm/s, distance of 30% strain, and load cell of 5 kg.
Hardness value was considered as mean peak compression force and expressed in grams.
Average values of five replications were considered Fig.3.9 shows a typical force time curve of
Mushroom Powder based extruded products for hardness measurement.
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Fig. 3.10 A typical force-time curve of Mushroom Powder based extruded products for texture
measurement.
3.9 Experimental Procedure
Response surface methodology (RSM) was adopted in the design of experimental combinations.
The main advantage of RSM was the reduced number of experimental runs needed to provide
sufficient information for statistically acceptable results. A three-variable (five levels of each
variable) rotatable central composite experimental design was employed .The parameters and
their levels were chosen based on the literature available on extrusion process. The ingredients
used for the mushroom powder based extruded products preparation were dried mushroom
powder, ragi flour and barley flour. The five levels of the process variables were coded as -1.682,
-1, 0, +1, +1.682 (Montgomery, 2001) and design in coded form and at the actual levels are
given in Table 3.1.
3.10.1 Independent process variables
The independent variables considered during the experiment were:
1. Barrel temperature - 80o to 120o C
2. Screw speed - 200 to 300 rpm
3. Mushroom powder level – 0% to 20 %
The die size of 3 mm kept constant. Also the temperature of feeding zone and
kneading zone kept constant at 60o C and 80o C, respectively throughout the
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experiments.
3.10.2 Dependent process variables
The dependent variables considered during the experiment were:
1. Water solubility index (WSI)
2. Water absorption index (WAI)
3. Hardness (Hd)
3.10.3 Experimental design
Experiments were conducted in rotatable central composite design (RCCD) with four variable
and five levels of each variable. The process variables were barrel temperature, screw speed,
and dried mushroom powder level. With 6 numbers of central point experiment total number of
experiment was 20. Their corresponding ranges with details of actual and coded values are
given in Table 3.1.
3.11 Optimization
The Experimental design was applied after selection of the ranges. Twenty experiments were
performed according to a second order rotatable central composite design (RCCD) with three
variables and five levels of each variable. RSM was applied to the experimental data using a
commercial statistical package, Design Expert-version 8.0.2 (Stat-Ease, Minneapolwas, USA).
The twin screw extrusion process was optimized. The responses studied were Water Solubility
Index (WSI), Water Absorption Index (WAI) and Hardness (H).
The following second order polynomial response surface model was fitted to each of the
response:
2 2 2
21 1 1
k k o k i i k i i i k i j i ji i i j
Y b b X b X b X X
i=1, 2, 3; j=1,2
Where, Yk was response, bk, bki, bkii, and bkij are the constant, linear, quadratic and interaction
coefficients respectively and X1, X2 and X3 are codes of variables viz., apple pomace level,
moisture content of the raw material, screw rpm and barrel temperature respectively.
All the process variable variables were optimized for maximum water absorption index (WAI),
Minimum water solubility index (WSI) and minimum Hardness (H). The superior (optimum)
combination of the barrel temperature, screw rpm and mushroom powder level were selected
for the production of optimized mushroom powder based extruded products and the estimation
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of proximate composition viz., protein, fat, fir and carbohydrate content.
Table 3.1 Experimental combination for five different operating conditions (Actual values)
Run Barrel Temperature
(oC)
Screw Speed (rpm) Mushroom Powder
(%)
1 80.00 250 10
2 88.11 220.27 4.05
3 111.89 220.27 15.95
4 111.89 279.73 4.05
5 88.11 279.73 4.05
6 88.11 279.73 15.95
7 100.00 250.00 10.00
8 100.00 250.00 10.00
9 100.00 250.00 10.00
10 100.00 200.00 10.00
11 100.00 250.00 10.00
12 111.89 279.73 15.95
13 111.89 220.27 4.05
14 100.00 250.00 20.00
15 88.11 220.27 15.95
16 100.00 250.00 0.00
17 120.00 250.00 10.00
18 100.00 300.00 10.00
19 100.00 250.00 10.00
20 100.00 250.00 10.00
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Table 3.2 Experimental combination for five different operating conditions (Coded values)
Run Barrel Temperature
(oC)
Screw Speed (rpm) Mushroom Powder (%)
1 80.00 250 10
2 88.11 220.27 4.05
3 111.89 220.27 15.95
4 111.89 279.73 4.05
5 88.11 279.73 4.05
6 88.11 279.73 15.95
7 100.00 250.00 10.00
8 100.00 250.00 10.00
9 100.00 250.00 10.00
10 100.00 200.00 10.00
11 100.00 250.00 10.00
12 111.89 279.73 15.95
13 111.89 220.27 4.05
14 100.00 250.00 20.00
15 88.11 220.27 15.95
16 100.00 250.00 0.00
17 120.00 250.00 10.00
18 100.00 300.00 10.00
19 100.00 250.00 10.00
20 100.00 250.00 10.00
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CHAPTER IV
RESULTS AND DISCUSSION
In this chapter the results of different experiments conducted are presented under various
sections. These sections include results of proximate analyses of raw materials, and mushroom
powder based extrusion products using Twin Screw Extruder. Results of quality evaluation viz.
Water Solubility Index (WSI), Water Absorption Index (WAI) and hardness are also reported
in this chapter.
4.1 Proximate Analysis of Raw Materials
Proximate analysis of raw materials was done by the methods described in the section 3.2 of
chapter 3 and results are shown in Table 4.1.
Table 4.1 Proximate composition of ingredients of mushroom powder based extrudate products
per 100 g weight
Parameters Mushroom
Powder
Barley
Flour
Ragi
Flour
M.C. (%wb) 10.8 7.01 7.61
Protein content, (%) 23.89 9.9 6.76
Fat, (%) 2.7 2.9 1.88
Crude Fibre, (%) 29.22 12.01 2.52
Carbohydrates, (%) 41.1 67.06 78.76
Ash content, (%) 7.44 1.3 2.24
4.2 Properties of Extruded
Variation of responses (water absorption index, water solubility index, hardness) of extruded
with independent variables (mushroom powder content, screw speed and barrel temperature) is
shown in Table 4.2 and 4.3.
.
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Table 4.2 Different physical properties of extruded under different operating conditions (actual values)
Run Barrel
Temperature
(oC)
Screw
Speed
(rpm)
Mushroom
Powder
(%)
WAI
(g/g)
WSI
(%)
Hardness
(kg-f)
1 80.00 250.00 10.00 6.1 2.52 5.43
2 88.11 220.27 4.05 6.0788 6.04 6.18
3 111.89 220.27 15.95 12.443 8.8 5.9
4 111.89 279.73 4.05 7.268 4.04 4.078
5 88.11 279.73 4.05 7.268 7.417 4.23
6 88.11 279.73 15.95 13.224 5.32 6.91
7 100.00 250.00 10.00 8.172 4.9 5.93
8 100.00 250.00 10.00 4.5816 4.8 5.39
9 100.00 250.00 10.00 9.223 3.8 4.43
10 100.00 200.00 10.00 4.389 6.8 5.13
11 100.00 250.00 10.00 4.406 6.0 5.1
12 111.89 279.73 15.95 15.34 6.09 7.55
13 111.89 220.27 4.05 6.628 6.5 3.89
14 100.00 250.00 20.00 20.003 9.56 7.58
15 88.11 220.27 15.95 13.224 6.42 6.52
16 100.00 250.00 0.00 8.339 11.02 3.33
17 120.00 250.00 10.00 5.732 2.72 5.66
18 100.00 300.00 10.00 5.808 4.0 5.152
19 100.00 250.00 10.00 6.229 4.4 4.87
20 100.00 250.00 10.00 4.6632 5.1 5.21
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Table 4.3 Different physical properties of extruded under different operating conditions (actual values)
Run Barrel
Temperature
(oC)
Screw
Speed
(rpm)
Mushroom
Powder
(%)
WAI
(g/g)
WSI
(%)
Hardness
(kg-f)
1 80.00 250.00 10.00 6.1 2.52 5.43
2 88.11 220.27 4.05 6.0788 6.04 6.18
3 111.89 220.27 15.95 12.443 8.8 5.9
4 111.89 279.73 4.05 7.268 4.04 4.078
5 88.11 279.73 4.05 7.268 7.417 4.23
6 88.11 279.73 15.95 13.224 5.32 6.91
7 100.00 250.00 10.00 8.172 4.9 5.93
8 100.00 250.00 10.00 4.5816 4.8 5.39
9 100.00 250.00 10.00 9.223 3.8 4.43
10 100.00 200.00 10.00 4.389 6.8 5.13
11 100.00 250.00 10.00 4.406 6.0 5.1
12 111.89 279.73 15.95 15.34 6.09 7.55
13 111.89 220.27 4.05 6.628 6.5 3.89
14 100.00 250.00 20.00 20.003 9.56 7.58
15 88.11 220.27 15.95 13.224 6.42 6.52
16 100.00 250.00 0.00 8.339 11.02 3.33
17 120.00 250.00 10.00 5.732 2.72 5.66
18 100.00 300.00 10.00 5.808 4.0 5.152
19 100.00 250.00 10.00 6.229 4.4 4.87
20 100.00 250.00 10.00 4.6632 5.1 5.21
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Table 4.4 Minimum and Maximum values of the responses
Response Name
Units Observations Minimum Maximum
Y1 WAI g/g 20 4.389 20.003
Y2 WSI % 20 2.52 11.02
Y3 Hardness Kg-f 20 3.33
7.58
4.3 Diagnostic Checking of the Fitted Model
Based on t-statistics, regression coefficients significant at 90% level were selected for
developing the models representing the final equations in terms of coded factors. The resulting
polynomial, after removing the non-significant terms and all model term values, was calculated
and is presented in Table 4.5. Regression analyses showed that Hardness was significantly (P <
0.05) affected by linear term of C and interaction terms of (AB and BC. WSI was affected by
linear term of (B), interaction terms of (AB , AC) and quadratic terms of ( A2 and C2 ) , and WAI
was influenced by linear term of (C) and quadratic term of ( C2 ).
Table 4.4 The coded regression models for process variables and product properties: Water
Absorption Index (A), Water Solubility Index (B) and Mushroom powder level (C):
Responses Equation R2 R2 Adj.
F-value
Y1
WAI = + 6.16 + 0.093 * A + 0.52 * B + 3.41* C + 0.29 * A * B + 0.098 * A * C + 0.13 * B * C + 0.24 * A2 - 0.045
* B2 + 3.17 * C2 ……..(4.1)
0.9065
0.8224
10.78
Y2
WSI = + 4.83 + 0.042 * A - 0.70 * B + 0.013 * C - 0.68
*A * B + 0.76 * A * C - 0.34 * B * C - 0.75 * A2 + 0.23 *
B2 + 1.96 * C2 ….(4.2)
0.9392
0.8846
17.18
Y3
Hardness = + 15 - 0.15 * A + 0.023* B + 1.15 * C + 0.42 * A * B + 0.31* A * C + 0.48 * B * C + 0.19 * A2 + 0.051 * B2 + 0.16 * C2 ……….(4.3)
0.9137
0.8361
11.77
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4.4 Analysis of Variance (ANOVA)
The goodness-of-fit of the models was evaluated using the correlation coefficient R2, the R2
adjusted. (Piggot, 1986), the Fisher F test, as well as the derived P values and the results are
presented in Tables 4.5, respectively. In addition, significance of the lack of fit term was used to
judge adequacy of model fit. Regression models fitted to experimental results showed good
correlation coefficients (> 90%) for all extruded properties. For a response surface, these
correlation coefficients were quite high (Box et al., 1978). Table 4.5 shows that the F-values for
Y1, Y2 and Y3 were significant at the 95% level. However, the lack of fit was not significant for
Y1, Y2 and Y3 (P < 0.05).
Table 4.5 Analysis of variance (ANOVA) for second-order polynomial model fitted to response
surface
Response source Df.* SS MS F-
Value
P-Value
Prob>F
Y1
Model 9 309.91 34.43 10.77 0.0005
significant
A
B
C
A2
B2
C2
AB
AC
BC
1
1
1
1
1
1
1
1
1
0.12
3.70
159.04
0.69
0.077
0.14
0.86
0.029
144.26
0.12
3.70
159.04
0.69
0.077
0.14
0.86
0.029
144.26
0.037
1.16
49.78
0.22
0.024
0.045
0.27
8.936E-003
45.09
0.8519
0.306
<0.0001
0.6523
0.8796
0.8370
0.6157
0.9256
<
0.0001
Residual 10 31.95 3.20
Lack of
Fit
5 10.72 2.14 0.51 0.7642 Not
significant
Pure
Error
5 21.23 4.25
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Response source Df.* SS MS F-
Value
P-Value
Prob>F
Cor Total 341.87 19
significant
Y2
Model 9 84.65 9.41 17.18 <0.0001
A
B
C
A2
B2
C2
AB
AC
BC
1
1
1
1
1
1
1
1
1
1
0.024
6.75
2.353E-003
3.71
4.60
0.93
8.15
0.77
55.39
0.024
6.75
2.353E-
003
3.71
4.60
0.93
8.15
0.77
55.39
0.043
12.33
4.298E-003
6.77
8.40
1.70
14.88
1.40
101.16
0.8392
0.0056
0.9490
0.0264
0.0159
0.2218
0.0032
0.2633
<
0.0001
Residual 10 5.48 0.55
Lack of
Fit
5 2.78 0.56 Not
significant
Pure
Error
5 2.69 0.54
Cor Total 19 90.13
Model 9 23.09 2.57 11.77 0.0003
A
B
C
A2
B2
1
1
1
1
1
0.30
7.266E-003
17.93
1.44
0.30
7.266E-
003
17.93
1.39
0.033
82.27
6.62
0.2655
0.8588
<
0.0001
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Response source Df.* SS MS F-
Value
P-Value
Prob>F
Y3
C2
AB
AC
BC
1
1
1
1
0.76
1.81
0.54
0.037
0.38
1.44
0.76
1.81
0.54
0.037
0.38
3.48
8.29
2.47
0.17
1.73
0.0277
0.0918
0.0164
0.1469
0.6896
0.2179
significant
Residual 10 2.18 0.22
Lack of
Fit
5 0.910 0.18 0.02 0.6375 Not
significant
Pure
Error
5 1.27 0.23
Cor Total 19 25.27
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4.5 Water Absorption Index (WAI)
It is evident from Eq. (4.1) that Y1 depends on the three factors. All of the terms having positive
coefficient, viz, linear terms A, B and C, interaction terms AB, BC and AC and quadratic terms
A2 and C2 increases the WAI values. Only the quadratic term B2 having a negative coefficient
causes negligible decrease in the values of WAI. WAI measures the volume occupied by the
granule or starch polymer after swelling in excess water (Sriburi & Hill, 2000). It is visible from
the response surface graph that the WAI value increases with the mushroom content. The highest
value of WAI is 20.03 g/g which comes at 20 % mushroom powder level. It so happens due to
the fact that mushroom powder reconstitutes more rapidly. Moisture content, acting as a
plasticizer during extrusion cooking, reduces the degradation of starch granules and results in an
increased capacity for water absorption of cooked product. It is also visible from the response
surface graphs that the WAI increases with increasing screw speed level.
88.11
94.06
100.00
105.94
111.89
220.27
235.13
250.00
264.87
279.73
4.2
5.475
6.75
8.025
9.3
W
AI
A: Barrel Temperature
B: Screw Speed
Fig 4.5(a). Effect of extrusion variables barrel tempereature and screw speed on WAI
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Fig 4.5(b). Effect of extrusion variables barrel tempereature and mushroom powder on WAI
Fig 4.5(c). Effect of extrusion variables screw speed and mushroom powder on WAI
220.27
235.13
250.00
264.87
279.73
4.05
7.03
10.00
12.98
15.95
4
8.25
12.5
16.75
21
WAI
B: Screw Speed C: Mushroom Powder Level
88.11
94.06
100.00
105.94
111.89
4.05
7.03
10.00
12.98
15.95
4
8.25
12.5
16.75
21
WAI
C: Mushroom Powder Level
A: Barrel
Temperature
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4.6 Water Solubility Index (WSI)
The model equation predicting this response is given by Eq. (4.2). The positive linear coefficient
of A and C, quadratic coefficient of C2 and A2 and interaction terms of AC contributed to the
increase of Y4, whereas the negative linear coefficient of B, interaction terms of AB and Ac and
quadratic term of A2 contributed o the decrease of WSI. The highest value, i.e., 11.02% is
obtained at 0% mushroom powder level. The barrel temperature has also a significant effect on
the WSI values. It is increased with the increase of barrel temperature. The WSI determines the
amount of free polysaccharide or polysaccharide released from the granule after addition of
excess water. Moisture content for the blend was controlled to 16-17%.
.
Fig 4.6(a). Effect of extrusion variables barrel tempereature and screw speed on WSI
88.11 94.06
100.00 105.94
111.89
220.27
235.13
250.00
264.87
279.73
2.5
3.575
4.65
5.725
6.8
WSI
A: Barrel Temperature B: Screw Speed
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Fig 4.6(b). Effect of extrusion variables barrel temperatureand mushroom powder on WSI
Fig 4.6(c). Effect of extrusion variables screw speed and mushroom powder on WSI
4.05
7.03
10.00
12.98
15.95
88.11
94.06
100.00
105.94
111.89
2.5
4.675
6.85
9.025
11.2
WSI
C: Mushroom Powder Level
A: Barrel Temperature
88.11 94.06
100.00 105.94
111.89
4.05
7.03
10.00
12.98
15.95
2.5
4.675
6.85
9.025
11.2
WSI
A: Barrel Temperature
C: Mushroom Powder Level
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4.7 Hardness
It is evident from Eq. (4.3) that Y3 depends on the three factors. All the linear, interaction and
quadratic factors come with positive coefficients; so they increases the hardness values except
linear term A. It is, due to have a negative coefficient, causes a decrease in hardness values. The
response surface graphs obtained from this model show that the lowest values of hardness were
obtained at 4.05 % mushroom powder level. However, temperature has a very little effect on
hardness. It happens probably due to increase in starch degradation.
Fig 4.7(a). Effect of extrusion variables barrel tempereature and screw speed on Hardness
88.11
94.06
105.94
111.89
220.27
235.13
250.0
264.87
279.73
4.4
4.8
5.2
5.6
6
Hardness
A: Barrel Temperature B: Screw Speed
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Fig 4.7(b). Effect of extrusion variables barrel tempereature and mushroom powder on
Fig 4.7(c). Effect of extrusion variables mushroom powder and screw speed on hardness
4.05
7.03
10.00
12.98 15.95
88.11
94.06
100.00
105.94
111.89
3.3
4.375
5.45
6.525
7.6
Hardness
C: Mushroom Powder Level A: Barrel Temperature
88.11
94.06
100.00
105.94
111.89
4.05
7.03
10.00
12.98
15.95
3.3
4.375
5.45
6.525
7.6
Hardness
A: Barrel Temperature
C: Mushroom Powder Level
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4.12 Optimization and model verification performance
Numerical optimization of the process variables was carried out with the help of commercial
software (Design Expert Version, 8.0.2 trial). The optimization was carried out under certain
applied constraints. The software was used to generate optimum processing conditions and to
predict the corresponding responses as well. The applied constraints and the predicted optimum
values obtained for the various responses are reported in Table 4.6 Extrusion cooking was
carried out under the optimum processing conditions and the responses were recorded (mean of
10 measurements). Thus, establishing the suitability of the models to predict the various
responses as desired for a particular application.
Table 4.6 Optimized processing condition of the variables and responses
Name Condition Lower limit Upper limit Importance
Barrel Temperature is in range 88.11 111.89 3
Screw Speed is in range 220.27 279.73 3
Mushroom Powder
Level maximize 4.05 15.95 3
Responses
WAI maximize 4.389 20.003 3
WSI minimize 2.52 11.02 3
hardness minimize 3.33 7.58 3
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Table 4.7 Optimized values of the independent parameters
No
Barrel
Temperature
Screw
Speed
Mushroom
Powder
Level WAI WSI hardness
Desira
bility
1 88.11 257.94 15.78 12.6141 5.08604 6.476101 0.553
2 88.11 257.68 15.78 12.61421 5.08908 6.475742 0.553
3 88.11 257.26 15.8 12.63708 5.10105 6.47822 0.553
4 88.11 256.91 15.87 12.73713 5.13687 6.490993 0.553
5 88.11 255.35 15.87 12.73195
5.1285 6.488024 0.553
4.13 Proximate analysis of the optimized extrudate
The results obtained from proximate analysis of extrudate product prepare according to the
rotatable central composite design are tabulated in Table 4.8.
Table 4.8 Proximate composition of extruded product
Parameter Content (g/100g)
M.C.(g) 7.84
Protein content, (g) 10.19
Fat, (g) 2.34
Crude fiber (g) 6.19
Carbohydrates, (g) 69.54
Ash content, (g) 2.98
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CHAPTER V
SUMMERY AND CONCLUSION
Barley (Hordeum vulgare vulgare L.) is an ancient cereal grain, which upon domestication has
evolved from largely a food grain to a feed and malting grain. However, barley food use today
remains important in some cultures around the world, particularly in Asia and northern Africa,
and there is renewed interest throughout the world in barley food because of its nutritional value.
This review covers basic and general information on barley food use and barley grain processing
for food use, as well as an in-depth look at several major aspects/traits of interest for barley food
use including kernel hardness and colour, grain starch, and β-glucan contents.
Finger millet (Ragi, Eleusine Coracana) is an important staple food in the eastern and central
Africa as well as some parts of India (Majumder et al., 2006). It is rich in protein, iron, calcium,
phosphorus, fibre and vitamin content. The calcium content is higher than all cereals and iodine
content is said to be highest among all the food grains. Ragi has best quality protein along with
the presence of essential amino acids, vitamin A, vitamin B and phosphorus (Gopalan et al.,
2004). Thus ragi is a good source of diet for growing children, expecting women's, old age
people and patients.
Oyster mushroom (Pleurotus ostreatus) is one of the most widely eaten mushrooms. It is rich in
protein and other necessary nutritional components. Consumer demand is also increasing for
mushroom soup. Many mushroom soup powder are available in the market. The dry mushroom
content of these products are approximately 2-3% giving not more than 0.5% protein content in
the soup.
Hence it is intended to use the dried mushroom powder for preparation of protein enriched
product for soup powder preparation using Twin Screw Extruder. Barley and ragi flour increases
the crude fiber content and also effect the texture and solubility of the product. So, barley and
ragi were also used for the extrusion purpose.
The technology of extrusion of foods has grown rapidly in the last 15 years, mainly because it
can economically produce a variety of products with attractive texture, size and shape. The use
of twin screw extruders has rapidly increased the number of extruded products. To utilize this
Twin screw extrusion process effectively, the independent process parameters need to be
optimized on the basis of the product qualities, such as Water absorption index, water
solubility index and texture (hardness) of the final product.
Twin screw extruders have certain advantages over the single screw extruder viz., flexibility,
easy to handle, better control, variability, cheaper production cost/metric ton, almost nil survival
of microbial count.
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The response surface methodology (RSM) was used to optimize the process parameters for
developing RTE snack.
Based on the above considerations the present investigation was undertaken with the following
objectives:
1. To develop protein enriched ingredient for the preparation of mushroom soup powder
using twin screw extruder.
2. To optimize the process parameters for the preparation of the mushroom soup ingredient
A laboratory model co-rotating twin screw extruder (make: BTPL, model: EB-10) with 10 HP
motor (400V, 3 Ph, 50 Hz) was used for extrusion cooking purpose. The extruder barrel was
provided with 3 electric band heater (just before die section, kneading section and feeding
section) and a temperature sensor for each. 3 water jackets were provided to extruder barrel
with water supply through solenoid valves controlled through PID controller.
The independent variables considered during the experiment were:
4. Barrel temperature - 80o to 120o C
5. Screw speed - 200 to 300 rpm
6. Dried mushroom powder added- 0% to 20%
The die size of 3 mm kept constant. Also the temperature of feeding zone and kneading zone
kept constant at 60o C and 80o C, respectively throughout the experiments.
The experimental design was done accordingly to a second order rotatable central composite
design (RCCD) and a total of 20 experiments were performed according to with three variables
and five levels of each variable. RSM was applied to the experimental dada using a
commercial statistical package, Design Expert-version 8.0.2 (Statease Inc., Minneapolis,
USA). The relative effects of the process variable on the responses were studied and the twin
screw extrusion process was optimized in order to get best quality mushroom powder based
extruded product. The responses studied were Water Solubility Index (WSI), Water Absorption
Index (WAI), and Hardness (Hd). The second order polynomial response surface model was
fitted to each of the response.
Product was optimized for maximum Water Solubility Index (WSI), minimum Water
Absorption Index (WAI) and minimum Hardness. Quadratic model was fitted to the
experimental data for all the variables. Numerical optimization of all the responses gave final
solution in terms of variables viz., barrel temperature 88.11°C, screw rpm 257±1.0, mushroom
powder level 15.8%. The corresponding responses predicted were 12.6 g g-1, 5.08 %, and 6.47
kgf for WAI, WSI and Hd respectively. The optimum MP based extruded product having
protein content, fat content, Crude Fiber, carbohydrates and ash content are 10.19, 2.34, 6.19,
69.54 and 2.98 respectively.
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Based on results of the present investigation, following conclusions could be drawn:
1. The optimum conditions for developing protein enriched mushroom powder based
extruded product through Twin Screw Extruder are, flour mix comprised of Barley and
Ragi flour with 15.8% of dried mushroom powder; screw speed of 257±1 rpm and barrel
temperature of 88.11°C.
2. The developed mushroom powder based extruded product is enriched with high protein
content (10.19%) which eventually can increase the total protein content of soup powder.
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FUTURE WORK
1. The hardness of the extruded product can be minimized by using increased moisture
content in the blend. Hence, studies on the effect of varying moisture content during the
extrusion process on hardness can be done.
2. The extruded product developed will be used as an ingredient for the preparation of
mushroom soup powder. Experiments regarding the textural changes of the soup made at
different temperatures with different intervals from the products can be done in future.
3. The sensory evolution of the soup using varying degrees of additives and viscosity analysis
using stabilizers can be done.
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