Body of Thesis

1

CHAPTER 1

INTRODUCTION

1.1Review of the Literature

1.1.1 Wheat

Wheat is one of the world's most important food crops. Historic documents confirm

that wheat is the earliest field crop used for human food processing. It also became the

leading grain used for human consumption due to its nutritive profile and relatively

easy harvesting, storing, transportation, and processing, as compared to other grains.

The earliest varieties, grown 12,000-17,000 years ago in the Near East, were Triticum

monococcum (einkorn) and Triticum dicoccum (emmer). Continued breeding resulted

in the development of new varieties around the world that often became adapted to

areas previously unsuited for the cultivation of wheat.

The main wheat varieties grown today are Triticumaestivum, subspecies vulgare,

which is a hexaploid and this species includes hard red winter, hard red spring, soft

red winter, and white wheat. Another wheat durum (Triticum durum) is a tetraploid

wheat specices

Wheat (Triticum) categorizes under the grass family, Poaceae, which include the

cereal grains such as rice, corn. All of these grains can be milled into flour, but only

wheat flour has the ability to be transformed into glutinous dough, together with water

and other ingredients (Hoseney, 1998; Matz, 1989; Cauvain, 2001).

2

1.1.2 Types of Wheat

• Hard wheat –“Strong whets of Canada (Manitoba) and the similar hard red spring

(HRS) whets of the US. They yield excellent bread-making flour because of their high

quantity of protein ranges 12–15 % mainly in the form of Wet gluten (29-39%)”.

• Medium type –“used for general purposes like bun, rolls and Donuts having protein

9-12 % with wet gluten 27-30 %”.

• Soft wheat –“less attractive bread than that achieved from strong wheat. The loaves

are generally smaller, and the crumb has a less pleasing structure. Soft wheat,

however, possess excellent characteristics for the production of flour used in cake &

biscuit manufacture”

•Durum – Very hard, translucent, light-colored grain used to make semolina flour for

pasta

1.1.3 Wheat Flour

Wheat flour is the resultant product of wheat grains after milling. Wheat grains or

kernels are dry, one-seeded fruits, which is member of the grass family Gramineae

(Pomeranz and Shellenberg, 1971; Hoseney, 1998). The kernel is surrounded by the

pericarp within which the germ (or embryo) and the endosperm are enclosed. About

5% of the kernel consists of the pericarp, which is mainly made up of cellulose. The

germ comprises approximately 3% of the kernel and is rich in protein, B vitamins and

enzymes. Flour is mainly made up from the remainder of the kernel, which is the

starchy endosperm Starch, at about 65%, makes up the biggest portion of the flour. It

consists of linear structures namely amylose and branched structures called

amylopectin. Amylose is linked by a-1,4 glycosidic bonds, while amylopectin is

linked by both a-1,4 and a-1,6 glycosidic bonds. (Stauffer, 1998).

Protein is the second most abundant nutrient in the endosperm (Pomeranz and

Shellenberg, 1971; Kent and Evers, 1994; Hoseney, 1998).

Approximately 80 -90% of the total wheat proteins are storage proteins and they play

a major role in bread production because of its essential function in bread structure.

The gluten network forms when flour is combined with water and with some energy

3

input (Kent and Evers, 1994; Cauvain, 1998a; Hoseney, 1998; Cauvain and Young,

2000). It is crucial for the retention of air and carbon dioxide during bread making and

thus gives bread its structure.

The two major components of the gluten storage proteins are glutenins and gliadins.

Glutenin is known to give elasticity and gliadin viscosity to the gluten network

(Hoseney, 1998, Stauffer, 1998). About 2-3% of the total flour proteins comprise of

the water-soluble proteins. These include albumins, globulins and the water- soluble

pentosans. Other minor constituents of wheat flour are the lipids, the inorganic

compounds i.e. ash and the non-starch polysaccharides i.e. pentosans (Stauffer, 1998).

Pentosans is important because of their high water absorption capacity (Michniewicz,

et aI, 1991; Michniewicz, et aI, 1992). They occur in wheat flour at about 2.5% on a

dry flour basis (Rouau, et aI, 1994). Other beneficial effects of pentosans include

increased loaf volumes and a better crumb structure (Delcour, et al, 1991; Rouau, et

al, 1994; Qi Si, 1997) Lipids. another minor constituent of wheat flour, occur at levels

around 2% (Stauffer, 1998). Although they only account for a fraction of the flour,

they are essential in bread making. They contribute to the final texture of the baked

product and influence the flavour and the mouth feel of a product (Charley,1982).

Figure 1.1; Wheat kernel

4

Country Annual Wheat Consumption (tons)

*103

China 104500

India 69000

Russia 35500

U.S.A 33203

Pakistan 18750

Srilanka 860

Table 1.1: Annual wheat consumption patterns

1.1.3.1 Types of Wheat Flour

1. All-purpose flour is white flour milled from hard wheat or a blend of hard and soft

wheat. It gives the best results for many kinds of products, including some yeast

breads, quick breads, cakes, cookies, pastries and noodles. All-purpose flour is usually

enriched and may be bleached or unbleached. Bleaching will affect nutrient value.

Different brands will vary in performance. Protein varies from 8 to 11 percent.

2. Bread flour is white flour that is a blend of hard, high-protein wheat and has greater

gluten strength and protein content than all and in some cases conditioned with

ascorbic acid, bread flour is milled primarily for commercial bakers, but is available

at most grocery stores. Protein varies from 12 to 14 percent.

3. Cake flour is fine soft wheat with low protein content. It is used to make cakes,

cookies, crackers, quick breads and some types of pastry. Cake flour has a greater

percentage of starch and less protein, which keeps cakes and pastries tender and

delicate. Protein varies from 7 to 9 percent.

4. Pastry flour has properties intermediate between those of all- purpose and cake

flours. It is usually milled from soft wheat for pastry-making, but can be used for

cookies, cakes, crackers and similar products. It differs from hard wheat flour in that

it has a finer texture and lighter consistency. Protein varies from 8 to 9 percent.

5. Semolina is the coarsely ground endosperm of durum, a hard spring wheat with a

high-gluten content and golden color. It is hard, granular and resembles sugar.

Semolina is usually enriched and is used to make couscous and pasta products such as

spaghetti, vermicelli, macaroni and lasagna noodles. Except for some specialty

products, breads are seldom made with semolina.

5

6. Durum flour is finely ground semolina. It is usually enriched and used to make

noodles.

7. Whole wheat, stone-ground and graham flour can be used interchangeably; nutrient

values differ minimally. Either grinding the whole-wheat kernel or recombining the

white flour, germ and bran that have been separated during milling produces them.

Their only differences may be in coarseness and protein content. Insoluble fiber

content is higher than in white flours.

1.1.4 Bread

Bread is one of the most popular yeast leavened product all over the world as well as

in Sri Lanka which made by wheat flour. The uniqueness of wheat flour to be

transformed into cohesive, viscoelastic mass is due to the hydration of gluten proteins

in the wheat together with the application of mixing energy. After the dough is

formed, the gluten structure entraps the gasses produced during the fermentation

stage. This allows the dough mass to expand and to be baked into a soft, light and

palatable product, which is known as bread (Hoseney, 1998; Matz, 1989; Cauvain,

2001).

Bread has been around for thousands of years, although its exact time of discovery

cannot be pinpointed (Pomeranz and Shellenberger, 1971; Cauvain, 1998). According

to Pomeranz and Shellenberger (1971), the history of bread is almost as old as the

history of mankind, since it has long been used as a sacred symbol in religious

ceremonies. In ancient times, the Egyptians used it as both a sacrifice and a tribute to

their gods. Today Christians portray the body of Christ at Communion with bread.

History also implies that bread has been used in a political context causing the fall of

Rome and the French Revolution to name a few. Bread has many variations

depending on the shape, size, texture, colour and taste (Cauvain, 1998a; Hoseney,

1998). The origin of the variations can be traced to the various parts of the world, for

example, baguettes from France and flat breads from the Middle East.

According to Cauvain (1998a), bread making most likely began in the Middle East,

because that is where cereal farming originated.

All over the world, bread has been regarded as a staple food (Pomeranz and

Shellenberger, 1971; Cauvain, 1998a) for the past millennia. As a single food source,

bread supplies the most nutrients (Pomeranz and Shellenberger, 1971) when

6

compared to food from other cereal grains. For sliced white bread, typical values are

7.6% protein; 1.3% fat and 46.8% carbohydrates. This is in comparison with the

typical values for cooked brown rice with a protein content of 2.6% and 1.5%; a fat

content of 1.1% and 1.1% and a carbohydrate content of 32.1% and 9.0%,

respectively (Kent and Evers, 1994).

In this twenty-first century with our busy lifestyles, people often opt for convenient

alternatives with ingredients of a more natural origin, of which bread is a good

example.

1.1.5 Additives for wheat Flour

“Food additives can be defined as substances added in small amounts to something

else to improve, strengthen, or otherwise alter it”. Additives are used for Wheat flour

because of they offer many advantages such as improved volume, water absorption,

texture, crumb, shelf life & slicing characteristics, aroma, shape size of the bread, the

baker could adjust the timing of fermentation and mixing, as well as proofing and

baking conditions, to adjust for variations in flour properties, yeast activity. These

adjustments are necessary to obtain the desired quality of finished baked products.

Other advantage of additives is greater when either the desired quality flour is not

available or bakery products are made from composite. Mostly weak wheat flour is

less suitable for bread making it is there for desirable to use some additives to

improve the quality of bakery product.

In the last years, diverse treatments have been applied for improving the quality of

bakery products. (Rosell, Wang, Aja, Bean & Lookhart, 2003; Aja, Wang & Rosell,

2003). Mainly use additives for improve those characteristics mentioned above.

Recently, consumers do not want artificial or synthetic additives to be used for bread

making. Therefore, the use of enzymes is very important as improvers for breamaking

(Harada, Lysenko, & Preston, 2000; Morita, Arishima,Tanaka, & Shiotsubo, 1997)

7

1.1.5.1 Enzymes as an additive

Enzymes are biological compounds, usually proteins, which expedite the conversion

of one substance into another. Their presence accelerates the rate of a chemical

reaction and they are often specific and act upon only one substrate, or catalyze only

one kind of reaction, in different, but related, substrates. Basically enzymes can

hydrolyse a polymeric substrate in two ways. Exo-enzymes remove a single polymer

unit from the end of the polymer chain, whereas endo-enzymes can rupture the

internal bonds in a random manner at any point along the chain. The activity of

enzymes is dependent upon temperature. Enzymes used in baking are usually stable at

room temperature and the rate of enzyme activity doubles with each 10°C increase up

to the temperature of denaturation, at which the enzyme is inactivated. Most enzymes

are inactivated above 60°C.

For decades, enzymes such as malt and fungal alpha-amylases have been used in

bread-making. Rapid advances in biotechnology have made a number of exciting new

enzymes available for the baking industry. The importance of enzymes is likely to

increase as consumers demand more natural products free of chemical additives. For

example, enzymes can be used to replace potassium bromate, a chemical additive that

has been banned in a Sri Lanka.

The dough for bread products consists of flour, water, yeast, salt and possibly other

ingredients such as sugar and fat. Flour consists of gluten, starch, non-starch

polysaccharides, lipids and trace amounts of minerals. As soon as the dough is made,

the yeast starts to work on the fermentable sugars, transforming them into alcohol and

carbon dioxide, which makes the dough rise. The main component of wheat flour is

starch. Gluten is a combination of proteins that forms a large network during dough

formation. This network holds the gas in during dough proofing and baking. The

strength of this gluten network is therefore extremely important for the quality of all

bread raised using yeast. Enzymes such as amylase, xylanases, lipases and oxidases

can directly or indirectly improve the strength of the gluten network and so improve

the quality of the finished bread the strength of the gluten network and so improve the

quality of the finished bread

8

1.1.6 Major Enzymes used in bakery industry and their functionality

1.1.6.1 Amylases

Amylase is added to dough for two purposes: (1) to aid in formation of maltose and

glucose as substrates for yeast fermentation, and (2) to interfere with starch

retrogradation and the thus enhance the shelf life of the baked product. These two

aims are accomplished at different stages of production, the first during fermentation

and the second in the oven. The amylopectin component of starch is depicted, and the

sites at which the different kinds of amylase hydrolyze the glucosidic links.

The yeast substrate produced by amylase action is maltose. Yeast uses glucose and

fructose more readily than maltose, because it must synthesize the enzyme maltose

(which hydrolyzes maltose to glucose) before it can metabolize maltose (sanderson et

al. 1983).In addition amylase requires time to hydrolyze starch, to taking these two

facts together readily shows that the use of amylase to provide yeast nutrition is

effective only in dough which receive a relatively long fermentation time and which

contain little or no added sugar. About the only bakery product today that meets these

criteria is saltine cracker dough, and the addition of diastatic malt syrup (a

concentrated water extract of malted barley and/or wheat that contains ά-amylase and

β-amylase activity) is common in the industry. In most other bakery dough, sugar is

routinely included both for yeast fermentation and for flavor in the finished product.

The use of ά-amylase has been suggested to increase loaf volume (Beck, Johnson, and

Miller 1959; Rubenthaler, Finney,and pomeranz 1965;Berger and Grandvoinnet

1974).In the absence of added sugar, this increase does occur, but the effect appears to

be directly related to the stimulation of yeast fermentation by the sugars released from

starch (Berger and Grandvoinnet 1974).amylases improve the grain of the finished

bread crumb, probably because they decrease dough consistency and improve

machinability (Bernett 1975). The other reason for adding ά_amylase to dough is to

retard staling in the baked product (Conn,Johnson,and Miller

1950;Miller,Johnson,and Palmer 1953;Zobel and Senti 1959;Waldt 1968;Dragsdorf

and Varriano-Marston 1980)

9

1.1.6.2 Xylanase

Wheat flour contains 2-3% pentosans. which are polysaccharides that are not

starch.about half of these are water soluble & half are insoluble. about 3/4are of these

pentosans are xylans. the significant fact about flour xylans are extremely hydrophilic,

accounting for almost one fourth of the water absorption requirement of a wheatflour

dough & loaf volume (kulp 1968;Shelton and Apolina 1985).It means that xylans

contribute to the consistency (viscosity) of dough. Xylans have an important role in

bread quality due to their water absorption capability and interaction with gluten. The

hydrolysis of pentosans using some enzymes like hemicellulase or pentosanase at the

optimal level improves the dough properties, leading to a greater uniformity in quality

characteristics. The application of xylanolytic enzymes has increased for the last few

decades owing to their potential effectiveness in breadmaking. Starch and non-starch

carbohydrate- hydrolyzing enzymes are commonly used in the breadmaking industry

as bread improvers. Enzymatic hydrolysis of non-starch polysaccharides leads to the

improvement of rheological properties of dough, bread specific volume, and crumb

firmness. Xylanase transforms water-insoluble hemicellulose into soluble form, which

binds water in the dough, therefore decreasing dough firmness, increasing volume and

creating finer and more uniform crumbs. It significantly improves manufacturing

conditions: dough is made more 'machine-friendly' as it does not stick to the

machinery parts .During gluten-starch separation process, gluten is formed first as a

result of breakdown of the gliadin-glutelin structures during mixing, followed by their

re-agglomeration. To study their effect, pentosans, enzymes,etc. can be added after

the mixing step by simple modification of Glutomatic System. It has been observed

that re-aggregation of gluten protein starts immediately after the first mixing step

during the dough dilution phase. Addition of pentosans or xylanase during this phase

can strongly affect gluten formation. The addition of xylanase prior to dough mixing

can lead to overdose effects. This is not observed when xylanase is added later during

the agglomeration phase. Pentosans and xylanase act mainly during the re-

agglomeration of gluten, following the breakdown of gluten structures during mixing,

which ultimately affects both gluten yield and gluten rheological properties. Effects of

pentosans and xylanase on gluten are paralleled by effects on dough, especially on

dough extensibility

10

Enzymes are proteins and that they are substrate specific. This means that a given

enzyme only will work on a certain substrate and only do a very particular action.

Although they take part in a chemical (enzymatic) reaction, they do not change during

that reaction. That accelerates or facilitates chemical reactions. Because they are

proteins, they are heat sensitive and all enzymes have an optimum temperature and

pH for activity. Within that range, activity increases with temperature until the

denaturation point is reached. At that point the enzyme will lose its functionality.

Apart from temperature and pH, enzymes are also dependent upon the availability of

water, amount of enzyme used, the availability of the substrate and the time allowed

for the reaction

1.1.6.3 Glucose Oxidase

Protein crosslinking or the formation of covalent bonds between polypeptide chains is

a way of modifying the protein functionality and simultaneously increasing its

applications in different processes. Oxidation induces the formation of disulfide

bonds by coupling of two cysteine residues that are adjacent within a food protein

matrix, and dityrosine crosslinks (Tilley,Benjamin, Bagorogoza, Okot-Kotber,

Prakash & Kwen, 2001; Rasiah, Sutton, Low, Lin & Gerrard, 2005), it results the

covalent crosslinking of proteins. This reaction on bread dough induces the formation

of a protein network with improved viscoelastic and structural properties, and

therefore, betters performance for breadmaking (Wikström & Eliasson, 1998;

Fayle,Gerrard, Simmons, Meade, Reid & Johnston, 2000). Glucose Oxidase catalysis

the oxidation of β-D- glucose to gluconic acid and hydrogen peroxide.(Rosell et al.,

2003; Aja et al., 2003; Hoseney & Faubion, 1981; Haarasilta, Pullinen & Vaisanen,

1991; Nakai, Takami Yanaka & Takasaki, 1995; Primo- Martin, Valera & Martinez-

Anaya, 2003; Gujral & Rosell, 2004) indicate that hydrogen peroxide produced

during GO reaction causes the oxidation of the free sulfhydryl units from gluten

protein giving disulfide linkages and the gelation of water soluble pentosans,

changing rheological properties of wheat flour dough. This hypothesis was confirmed

by Velmulapalli and Hoseney (1998a), who found that free thiol groups of the water

soluble proteins of flour or dough decreased in presence of GO. The addition of GO

leads to an increase in the elastic of wheat flour dough (Gujal et al., 2004;

Vemulapalli et al., 1998b; Dunnewind, Van Vliet & Orsel, 2002) and also gives less

stiff dough than control and its addition have a strengthening effect (Martinez-Anaya

11

& Jimenez, 1997). Primo-Martín et al (2003) concluded that pentosanase/GO

combination resulted in dough with improved extensibility yielding better gluten

quality. An improvement in the wheat bread loaf volume and crumb grain has been

obtained by adding GO (Vemulapalli et al., 1998b; Xia, Jin & Liang, 1999), Van Oort

(1996) found this improved bread volume. The functional properties of bread dough

mainly depend on the proteins forming the gluten network.

1.1.6.4 Lipase

Lipases are used for their dough conditioning properties (Qi Si, 1997; Poldermans and

Schoppink, 1999) where they significantly retard bread staling. Lipase-treated flour

has an increase in gluten strength, which results in good dough conditioning ability.

Polderrnans and Schoppink (1999) reported that lipases hydrolysed triglycerides into

mono- and diglycendes. The monoglycendes interact with starch and thus reduce its

ability to retrograde, which leads to a softer crumb. Lipase also has a positive effect

on crumb colour and structure (Poldernians and Schoppink, 1999), even without

added fat. Qi Si (1997) reported a 20-30% increase in the loaf volume with the

addition of 500-2000 lipase units per kilogram (LU/kg) of flour. Too high values lead

to a negative effect on loaf volume as well as a too dry and stiff dough. A study done

by Si and Hansen (1994) in Gélinas (1998 also reported lipase to be involved in

dough bleaching, though the exact mechanism is not yet fully understood. However, it

is postulated that after lipase has hydrolysed the triglycerides, the free fatty acids

generated are then oxidized by lipoxygenase according to Castello et aI (1998) in

Goesaert et al(2005).

1.1.7 The synergetic effects of enzymes

Each of the enzymes mentioned above have its own specific substrate in wheat flour

dough. For example, lipases work on the lipids, xylanase works on the pentosans, and

amylases work on the starch. Because the interaction of these substrates in dough and

bread is rather complex, the use of enzyme combinations can have synergistic effects

that are not seen if only one enzyme is used, not even at high dosages. Quite often an

overdosage of enzymes will have a detrimental effect on either the dough or the

bread. For instance, an overdose of fungal alpha-amylase or hemicellulase / xylanase

may result in dough that is too sticky to be handled by the baker or baking equipment.

It is therefore beneficial for some types of bread formulation to use a combination of

12

lower dosages of alpha-amylase and xylanase with low dosages of lipase or glucose

oxidase to achieve optimum dough consistency stability and bread quality. Another

example is to use maltogenic alpha-amylase in combination with fungal alpha-

amylases and xylanase or lipase to secure optimum crumb softness as well as

optimum bread quality in terms of crumb structure, bread volume, Color

1.1.8 Other ingredients in bread making

1.1.8.1 Yeast

Saccharomyces cerevisiae is the scientific name for Bakers‟ yeast, which is generally

used in the baking industry (Jay, 1992). It is a living organism that multiplies by

multilateral budding to produce spherical spores. It comes in a number of physical

forms, namely compressed, liquid and dried yeast (Brown, 1993;Kent and Evers,

1994; Gould, 1998). Hoseney, 1998, gives the following simplified chemical reaction

for the action of yeast: This process is anaerobic and the gas (CO2) produced leavens

the bread (Kent and Evers, 1994; Williams and Pullen, 1998). Besides gas production

and leavening, yeast in baking also affects dough rheology and flavour of the bread

(Kent and Evers, 1994). The way in which dough rheology is affected can be

explained by means of the spread test. Bread dough has both viscous-flow properties

and elastic properties. Dough with higher viscous-flow properties has a larger spread

ratio and one with higher elastic properties has a smaller spread ratio. When yeast is

added to a flourwater dough with a large spread ratio, the rheology changes in that the

spread ratio becomes smaller. This means that the dough has higher elastic properties

(Hoseney, 1998). Yeast fermentation produces reducing sugars, which interact with

the dough proteins on the surface, under the influence of heat. This process is known

as the Millard reaction, which causes browning of the bread crust and contributes

greatly to bread flavour (Brown, 1993; Kent and Evers, 1994).

13

1.1.8.2 Fat / Shortening

Initially fat was only incorporated into bread formulas subject to rapid processing

(Kent and Evers, 1994; Williams and Pullen, 1998). However, even in long

fermentation bread formulas, fat has a considerable improving effect on the quality of

the bread (Hoseney, 1998; William s and Pullen, 1998). Bread with fat stays softer for

longer periods because of the antistaling properties of fat (Hoseney, 1998). Lipase that

occurs naturally in bread flour hydrolyses fats into monoglycerides and diglycerides

(Qi Si, 1997; Poldermans and Schoppink, 1999). Monoglycerides form an insoluble

complex with the amylose portion of starch, resulting in the reduction of

retrogradation (Fig. 1) and hence a softer crumb.

Figure 1.2: The effect of shortening and mono-glycerides on the firming rate of Bread

(Hoseney, 1998).

1.1.8.3 Water

After flour, water is the second most abundant ingredient in breadmaking, but Its

importance is often overlooked (Gould, 1998; Cauvain and Young, 2000). Water is of

great significance for both quality and economic concerns. From a quality

perspective, water plays a two-fold role. Firstly, water acts as a solvent during the

formation of bread dough. When all the ingredients are mixed together for dough

formation, water hydrates the flour proteins and forms the water phase, in which the

soluble solids are dissolved and the yeast is dispersed (Brown, 1993; Cauvain and

Young, 2000,). Secondly, water acts as a plasticiser during mixing and after baking

(Hoseney, 1998; Matz, 1989;Cauvain and Young, 2000). With the aid of energy

14

during mixing, the gluten proteins are transformed into the gluten network. Post-

baking it continues its role as a plasticiser when it plays an important part in texture

determination of the final product (Cauvain and Young, 2000). Consumers determine

the freshness of baked bread by means of the „squeeze test‟, therefore the higher the

amount of water remaining in the bread, the softer and the more acceptable the

bread (Gould, 1998; Cauvain and Young, 2000). UK bakers have gained a reputation

for adding excess water (Gould, 1998), which happens to be solely for economic

reasons. Increasing the amount of added water will lead to an increase in yield and

hence a cost saving for the manufacturer (Cauvain and Young, 2000). Apart from that,

increased water absorption can also provide a softer, fresher product which has an

increased shelf life.

1.1.8.4 Salt

Sodium chloride (salt) is included at levels of about 2% in breadmaking (Kent and

Evers, 1994; Cauvain, 1998b; Hoseney, 1998). The main reasons for adding salt are

to: Develop flavour –without salt bread is tasteless. Salt also intensifies the bread

flavour developed by other ingredients (Kent and Evers, 1994;Cauvain, 1998b).

Retard fermentation-salt is used to control fermentation (Kent, 1994, Williams and

Pullen, 1998). Bread without salt has excessive proof and on the brink of collapse

with an uneven surface. Strengthen the gluten – by suppressing the repulsion charges

and increasing the molecular interaction between protein chains (Kent and Evers,

1994; Hoseney, 1998;Stauffer, 1998). Affect the crust colour–in controlling yeast

activity, salt ensure that sufficient sugar is available for the browning reactions to take

place (SA Chamber of Baking, 1995).

1.1.8.5 Ascorbic Acid

Ascorbic acid acts as an oxidising agent in the dough at levels of <200ppm of flour

weight (Williams and Pullen, 1998). It is chemically classed as a reducing agent

(Williams and Pullen, 1998; Cauvain, 2001), but in the presence of atmospheric

oxygen oxidises to dehydroascorbic acid (Kent and Evers, 1994; Williams and Pullen,

1998). The beneficial consequence of ascorbic acid comes into play during mixing of

the dough. Here the gluten network experiences disulphide-sulphydryl interchange i.e.

weakening of the gluten network due to breaking of disulphide bonds (Fig. 3).

Williams and Pullen (1998) suggested that ascorbic acid works by either oxidising –S

15

– H groups to SOH making it impossible for 3 disulphide-sulphydryl interchange

disulphide-sulphydryl interchange to occur or by forming new crosslinks between the

protein chains. Secondary benefits as a result of the strengthened gluten include better

gas retention leading to improved loaf volume (Kent and Evers, 1994).

Figure1.3: Representation of disulphide-sulphydryl interchange (William and

pullen,(1998)

16

1.1.9 Water Absorption

Water absorption in baked products can be defined as the amount of water addition

required to produce a dough optimum for processing. Increasing the amount of added

water will lead to an increase in yield and consequently a cost reduction. (Cauvain

and Young (2000),)

Water is a major constituent in most food products and accounts on average for

approximately 70% of the weight of a food product (Potter, 1995). In bread

formulations water accounts for about 60%, depending on the type of processing

method used (Cauvain, 1998a). Apart from processing parameters, intrinsic

parameters (Kent and Evers, 1994) as well as additional ingredients (Cauvain and

Young, 2000) can influence the amount water addition. These intrinsic parameters

have an important role toplay in dough rheology and the characteristics of the baked

bread (Cauvain and Young, 2000)

1.1.10 Summary

The use of enzymes instead of chemical is a very interesting option to improve bread

making performance of dough and bread, because they are perceived as natural and

non-toxic food components.

•Amylase; Maximizes the fermentation process to obtain an even crumb structure and

a high loaf volume Improves shelf-life of bread and cakes

•Glucose oxidase; Oxidative reaction with gluten to make weak doughs stronger, drier

and more elastic

•Lipase; Modifies the natural lipids in flour to strengthen the dough

•Xylanase; Dough conditioning. Easier dough handling and improved crumb structure

17

1.2 Objectives

1.2.1 Main objective

The major objective was this study determined the Optimum levels of

Enzymes for chosen proportion of hard and medium wheat flour and

determined the relationship between the effect of concentrations of Enzymes

on the bread quality and dough rheology.

1.2 2 Specific objectives

Replace artificial or synthetic additives which are using for improve bread

Flour

Increase the soft wheat proportion in current baker‟s flour which is produce by

the company.

18

CHAPTER 2

MATERIALS AND METHADALOGY

2.1 Flour

The Flour was got from serandib flour Mills. Two types of milled wheat Flour were

used for this study. Which was containing Chosen proportion of Hard & medium

Wheat flour and current bakers flour produce by the company. It was properly packed

into bags Stored at normal room temperature.

2.2 Enzymes

Commercial source of Amylase, Glucose oxidase, Xylanase, Lipase in ppm levels

were used for this study

2.3 Ingredients

Commercial sugar, salt, yeast, improvers use as other ingredients

2.4 Analysis of flour samples

Current bakers flour (Reference), new blend of flour which containing hard and soft

wheat and enzyme supplemented flour were analyzed as below procedures

19

2.4.1 Moisture (AACC-44.19)

Amount of free water in sample was Determined using this method.

Moisture content of the flour was determined by using Rapid Moisture method this

was done in a moisture analyzer at a temperature of 135°C.for 5g of flour.

2.4.2 Protein (AAcc-46.12)

Amount of protein of the flour was determined using this method.

1.00 g of sample was transferred on kjeldhal digestion tube. Catalyst powder and 25

ml of conc. H2SO4 were added to the tube. Then the tube was connected to fume trap

and attached to the pump. Sample was allowed to digest for two hours. Then the

sample was cooled. Sample was transferred to kjeldhal distillation apparatus which

has been previously conditioned by passing steam for several minutes. Then

distillation was done. Obtained ammonia trapped solution in to titration flask and it

was titrated with standard HCl solution. The endpoint is pink colour. Same procedure

was applied to a blank sample as well.

Protein % was calculated using following Formula

Protein % = (Sample titre – Blank titre) x Molarity of HCl x 5.8 x100

Weight of sample taken

2.4.3 Wet gluten (ICC.13.7; AACC-38.12.A)

Wet gluten is the plastic-elastic substance. The gluten content of the flour was

determined by using glutomatic system

10g of flour +0.01g was weighted and put into the washing chambers then added

4.8ml of 2% NaCl solution after that chambers fixed in to the machine This was then

washed to isolate the wet gluten, which was weighed after the residual adherent water

was removed by centrifugation.

20

2.4.5 Ash (AACC-8.12)

Overall mineral content of the wheat flour was determined using this method 2.00g

Flour samples was weighed in to crucible and heated in muffle furnace at 600 C for 2

hours the residue was cooled to room temperature and then weighed.

Ash content was calculated by below formula

Ash%= 100 (final weight-initial wt.) *100

Sample Wt. (100-Moisture content)

2.4.6 Falling number

The time allowed for a viscometer stirrer to fall through an aqueous flour gel, was

measured in seconds. The falling number is an indication of the amylase activity

7.00g Flour samples was weighed in to viscometer tubes for 14% moisture basis.

Then 25ml of distilled water was added in to the each tube. Then dry stoppers were

fixed and shake vigorously 25 times for homogenization. Replaced the stirs in to tubes

and kept in the machine

2.4.7 Farinograph (AACC-54.21)

The Brabender Farinograph was used as a tool to measure shear (fluid) and viscosity

of a mixture of flour and water. Using this method the resistance of dough during

mixing (consistency) was measured.

Consistency in terms of the Farinograph refers to the resistance of the dough,

measured in torque and expressed in Farinograph Units (FU).

Water absorption, Stability, Development time, Breakdown time. Degrees of

softening was analyzed using this method

21

2.4.8 Extensograph (ICC Standard No. 114/1).

The extensograph determines the resistance and extensibility of dough by measuring

the force required to stretch the dough with a hook until it breaks

Dough was formed from flour, water and salt and mixed under standard condition.

From this dough, a test piece 150g was balled and then put through a molder. After a

fixed period of time (45, 90 and 135min) the dough was stretched and the force was

recorded.

22

2.6 Methodology

Each two flour samples (current bakers flour reference and new blend of flour which

containing hard and soft wheat were analyzed for moisture content, ash, protein,

farinograph, extensograph, wet and dry gluten ,gluten index, falling number

In order to have general over view of enzyme effect on flour,

Enzymes were chosen in different concentration levels (low, medium, high) and

supplemented with flour. As Table 02

Enzyme Concentration (ppm)

Amylase 5 10 15

G:oxidase 10 20 30

Lipase 10 20 30

Xylanase 10 30 60

Table 2.1: Enzymes concentration levels supplemented with flour

The effect of different enzymes in different levels on, gluten quality, gluten amount,

gluten index, dough rheology, water absorption, falling number and final quality of

bread was investigated.

The effect of enzymes on gluten quality was evaluated concerning amount of wet and

dry gluten.

Water absorption, stability, development time, was analyzed using farinograph test.

Dough rheology (extensibility, resistance) was analyzed using extensograph

23

In order to find optimum levels of enzymes combination for chosen proportion of

hard and medium wheat flour blend, flour was treated with enzymes in recommended

dosage levels.

Four Enzymes combinations were prepared according to recommended range and

appropriate dosage levels.

Each enzyme was weighed out in ppm levels for 1 kg of flour basis.

Four Enzymes premixes were prepared, enzyme premixes were supplemented with

1kg of flour (four samples), and then those were sent to the mixer in order to be

properly dispersed.

Enzyme combinations activity was evaluated by the measurement of loaf volume and

in addition to that sensory analysis was done for evaluate bread quality with reference.

Enzyme Reference

239

Treatment1

230

Treatment

233

Treatment3

235

Treatment4

237

Amylase

M1 M2 M3 M4

G-oxidase

lipase

Xylanase

Table 2.2: Enzyme combination for Bread preparation

24

2.6.1 Bread making procedure

Fermented dough procedure was done for this study

Ingredients Quantity

Ratio %

Flour 1000 g 100

Sugar 20 g 2.0

Salt 18 g 1.8

Fat 20g 2.0

Yeast 3g 0.3

Ascorbic acid+

Improvers

3g 0.3

Water 610g 61.0

Table 2.3: Bread formulation

Flour (supplemented with enzymes), water, salt, yeast, fat, improvers were mixed in

above ratios and kneaded for 7minutes: Development of the gluten structure.

Then dough was kept for 90min: Incorporation of air bubbles within the dough and

Development of flavor compounds of the dough.

After that dough was divided into 450g mass pieces and kept for 10min. Then those

pieces were moulded and put into trays.

Moulde dough were kept in proofer for 2.5 hours for Fermentation and expansion of

the shaped dough pieces

Finally those were kept in oven for 25min in 185 centigrade: Further expansion of the

dough pieces and fixation of the final bread structure

25

2.6.2 Loaf volume

Loaf volume was measured by using laboratory scale

2.7 Sensory Attributes

Sample preparation for sensory evaluation

The bread/sliced bread samples were labeled with a randomly assigned 3 digit code.

Sensory parameters were assessed on reference and enzyme combination treated

bread samples.

2.7.1 Sensory Evaluation of bread

Trained Panel

10 Trained Panelists who were staff members in the Serandib flour mill used for

sensory. (Male and female). Panelists were given bread samples and asked to overall

appearance, crust colour. Symmetry of form, texture, grains, mouth feel and overall

acceptability. The panelists were asked to evaluate above characteristic using a proper

questionnaire with 5 point hedonic scale where 5 represented the highest order of

preference and 1 the least order of preference.

26

Chapter 3

RESULTS AND DISCUSSION

Table 3.1 below shows the difference in each attribute of current bakers flour which is

producing by the company and chosen proportion of hard and medium wheat flour

blend (without additives)

Parameter Reference

(without additives)

New Bakers Flour

(without additives)

Moisture % 13.8 13.5

Ash %(as is) 0.47 0.51

Protein %(as is) 12.5 11.8

Wet Gluten % 32.5 31.7

Gluten Index % 80 80

Falling Number 530 630

Water absorption 65 64

Table 3.1: Test results of current bakers flour and chosen proportion of hard

and medium wheat flour blend

Table 3.1 was explained the differences between current bakers flour and chosen

proportion of hard and medium wheat flour blend (without additives)

It was observed in new bakers flour ash and falling number higher than reference and

lower wet gluten, water absorption values.

27

60

61

62

63

64

65

66

contol Amylase 5ppm Amylase 10ppm Amylase 15ppm

Enzyme Level water absorption (FU)

Control 64

Amylase

5ppm 63.2

10ppm 62.4

15ppm 61.8

Glucose oxidase

10ppm 65.5

20ppm 65.8

30ppm 66.5

Lipase

10ppm 65.4

20ppm 65.8

30ppm 66.0

Xylanase

10ppm 65.2

30ppm 65.5

60ppm 66.3

Table 3.2: water absorption of flour for each enzyme in different level

Graph 3.1: water absorption of flour with amylase enzyme in different levels

According to graph water absorption of flour was decreased with amylase

concentration

28

64

64.5

65

65.5

66

66.5

67

contol Glucose oxidase10ppm

Glucose oxidase20ppm

Glucose oxidase30ppm

64.4

64.6

64.8

65

65.2

65.4

65.6

65.8

66

66.2

contol Lipase 10ppm Lipase 20ppm Lipase 30ppm

Graph 3.2: water absorption of flour with G:O enzyme in different levels

According to graph when increasing concentration of glucose oxidase enzyme water

absorption of flour was increased

Graph 3.3: water absorption of flour with lipase enzyme in different levels

According to graph water absorption of flour was increased with adding lipase

enzyme

29

64

64.5

65

65.5

66

66.5

contol Xylanase 10ppm Xylanase 30ppm Xylanase 60ppm

Graph 3.4: water absorption of flour with xylanase enzyme in different levels

According to graph when increasing concentration of glucose oxidase enzyme water

absorption of flour was increased

Table 3.3: Farinograph development time and stability for each enzyme

concentration level with flour

Enzyme Level

Development

Time (min) Stability (min)

Control 9.5 12.1

Amylase

5ppm 9.3 12

10ppm 2.2 11.7

15ppm 1.9 8.6

Glucose oxidase

10ppm 9.5 20

20ppm 23 20.8

30ppm 14.2 17.3

Lipase

10ppm 6.3 11.5

20ppm 5.5 9

30ppm 6.0 11

Xylanase

10ppm 9.5 11.9

30ppm 5.2 6.5

60ppm 4.8 5.4

30

0

5

10

15

20

25

contol G.O 10ppm G.O 20ppm G.O 30ppm

DevelopmentTime (min)

Stability (min)

0

2

4

6

8

10

12

14

contol Amylase5ppm

Amylase10ppm

Amylase15ppm

Development Time(min)

Stability (min)

Graph 3.5: development time and stability of flour with amylase enzyme in

different levels

According to graph development time and stability was reduced compare to control

when increasing amylase concentration

Graph 3.6: development time and stability of flour with G:O enzyme in

different levels

According to graph development time and stability was increased compare to control

when increasing Glucose oxidase concentration

31

0

2

4

6

8

10

12

14

contol Lipase10ppm

Lipase20ppm

Lipase30ppm


Stability (min)

0

2

4

6

8

10

12

14


Stability (min)

Graph 3.7: development time and stability of flour with xylanase enzyme in

different levels


when increasing xylanase concentration

Graph 3.8: development time and stability of flour with lipase enzyme in

different levels


when increasing lipase concentration

32

Enzyme Level Extensibility (mm) Resistance (BU)

45

min

90

min 135min 45

min

90

min

135

min

Control 162 153 149 364 512 553

Amylase

5ppm 178 169 163 358 486 574

10ppm 174 171 164 394 503 528

15ppm 175 170 161 390 481 518

Glucose

oxidase

10ppm 157 160 136 414 568 630

20ppm 163 152 150 357 492 636

30ppm 158 152 143 438 568 716

Lipase

10ppm 191 192 176 258 298 278

20ppm 193 187 195 228 299 299

30ppm 165 167 156 342 390 416

Xylanase

10ppm 180 165 164 362 474 489

30ppm 202 203 195 224 256 238

60ppm 217 219 218 196 204 218

Table 3.4: extensograph results for (45min, 90min, and 135min) Extensibility and

resistance of flour with each enzyme concentration

33

140

145

150

155

160

165

170

175

180

5ppm 10ppm 15ppm

Control Amylase

Extencibility (mm) 45min



140

145

150

155

160

165

10ppm 20ppm 30ppm

Control Glucose oxidase




Graph 3.9: Extensibility of flour with Amylase enzyme in different levels

According to graph extensibility was increased compare to control when increasing

amylase concentration

Graph 3 10: Extensibility of flour with G: Oxidase enzyme in different levels

According to graph extensibility was decreased compare to control when increasing

glucose oxidase concentration

34

140

150

160

170

180

190

200

10ppm 20ppm 30ppm

Control Lipase




140

150

160

170

180

190

200

210

220

230

10ppm 30ppm 60ppm

Control Xylanase




Graph 3 11: Extensibility of flour with Lipase enzyme in different levels


lipase concentration up to 20 ppm, but in 30ppm it was decreased

Graph 3 12: Extensibility of flour with Xylanase enzyme in different levels


xylanase concentration

35

Enzyme Level Wet Gluten% Dry Gluten% Gluten

index %

Control 31.7 10.3 80.44

Amylase

5ppm 31.4 10.0 81.21

10ppm 31.6 10.2 80.70

15ppm 31.2 10.0 81.73

Glucose

oxidase

10ppm 31.4 10.1 81.21

20ppm 31.6 10.3 80.70

30ppm 30.6 10.0 83.33

Lipase

10ppm 31.6 10.3 80.70

20ppm 31.2 10.0 81.73

30ppm 31.6 10.3 80.70

Xylanase

10ppm 31.4 10.2 81.21

30ppm 31.7 10.4 80.44

60ppm 31.6 10.3 80.70

Table 3.5: Amount of wet and dry gluten for each enzyme level

According to table 3.4, amount of wet gluten and dry gluten was not showed

significant difference compare to control with each enzyme level; it was showed

enzymes not effect for gluten amount on flour

Enzyme Level Falling Number

Control 630

Amylase

5ppm 570

10ppm 530

15ppm 505

Glucose oxidase

10ppm 594

20ppm 580

30ppm 585

Lipase

10ppm 585

20ppm 569

30ppm 596

Xylanase

10ppm 540

30ppm 452

60ppm 431

Table 3.6: Falling number for each enzyme level and control sample

36

Graph 3.13; falling number for each enzyme levels

It was showed when increasing amylase enzyme and xylanase enzyme reduce the

falling number

Sensory characteristic

According to the results, panelist found no difference (p>0.05) with respect to the

Overall appearance, crust color, symmetry of foam, mouth feel of the samples

(Appendix 02)

However panelist was found significant difference (p<0.05) with respect to texture,

grain and overall acceptability

0

100

200

300

400

500

600

700

5p

pm

10

pp

m

15

pp

m

10

pp

m

20

pp

m

30

pp

m

10

pp

m

20

pp

m

30

pp

m

10

pp

m

30

pp

m

60

pp

m

Control Amy: G:O. Lipase Xylanase

Falling Number

FallingNumber

37

CHAPTER 4

CONCLUSIONS AND RECOMMENDATION

Enzymes had positive effect on wheat flour by dough strengthening, conditioning

dough rheology and water absorption. Regarding the effect on final baked product,

enzymes improve the quality of bread by improving volume and other characteristics

Except treatment1 all other enzyme treatments were shown no significant difference

from the reference. So that according comparison cost of enzyme treatments it was

found that amylase 6ppm, glucose-oxidase 15ppm, lipase 25ppm and xylanase 40ppm

combination was the cheapest and best enzyme treatment for chosen proportions of

hard and medium flour blend

Enzymes can use for bakery products are made from composite flour or weak wheat

flour which are less suitable for bread making

38

References

Anjum, F.M. ,Khan, M.I.,Butt, M.S., Hussain, S.and Abrar, M.,(2006).Functional

properties of soya hulls supplemented wheat flour. Nutrition and Food Science

Atwell, W.A.,(2001).Wheat flour. Eagan Press handbook series,

Bilgin, B., Daglioglu, O. and Konyali, M.,(2006). Functionality of bread made with

pasteurized whey and/or buttermilk. Italian Journal of Food Science

Brown, J.,(1993).Advances in bread making technology. In: Kamel, B.S. and

Stauffer, C.E., Advances in baking technology. Blackie Academic and Professional,

New York,85-145

Catteral, P., (1998). Flour milling. In: Cauvain, S.P. and Young, L.S.,Technology of

Breadmaking. Blackie Academic and Professional, New York,

Cauvain, S.P.,(1998a). Bread – the product. In: Cauvain, S.P. and Young, L.S.

Technology of Breadmaking. Blackie Academic and Professional, New York,

Cauvain, S.P.,(1998b). Breadmaking processes. In: Cauvain, S.P. and Young,L.S.

Technology of Breadmaking. Blackie Academic and Professional, New York,

Cauvain, S.P.,(2001).Breadmaking. In: Owens, G., Cereal processing technology.

Boca Raton, CRC Press, 204-230.

Cauvain, S.P. and Young, L.S., (2000). Bakery food manufacture and quality –Water

control and effects. Blackwell Science,

Cauvain, S.P. and Young, L.S.,(2001). Baking problems solved. Woodhead

publishing Limited, Cambridge, 54-55.

Charley, H.,(1982). Food Science. Wiley, New York.195-214

39

Cleemput, G., Booij, C., Hessing, M., Gruppen, H. and Delcour, J.A.,(1997).

Solubilisation and changes in molecular weight distribution of arabinoxylans and

protein in wheat flour during breadmaking, and the effects of endogenous

arabinoxylan hydrolyzing enzymes. Journal of Cereal Science,55-66.

Delcour, J.A., Vanhamel, S. and Hoseney, R.C.(1991). Physicochemical and

functional properties of rye non starch polysaccharided. II. Impact of a fraction

containing water soluble pentosans and proteins on gluten-starch loaf volumes.

Cereal Chemistry,72-76.

Dendy, D.A.V. and Dobraszczyk, B.J., 2001. Cereals and cereal products: chemistry

and technology. Aspen Publishers, 100-139; 182-231.

De Kock, S., Taylor, J. and Taylor, J.R.N., 1999. Effect of heat treatm ent and particle

size of different brans on loaf volume of brown bread, 349-356.

Fessas, D and Schiraldi, A., 1998. Texture and staling of wheat bread crumb: effects

of water extractable proteins and pentosans. Thermochimica Acta 323,17-26.

Fessas, D and Schiraldi, A., 2001. Water properties in wheat flour dough I: classical

thermo gravimetric approach. Food Chemistry, 237-244.

Gallagher, E., Gormley, T.R. and Arendt, E.K., 2003. Crust and crumb

characteristics of gluten free breads. Journal of Food Engineering 56,153-161.

Gélinas, P., Poitras, E., McKinnon, C.M. and Morin, A., 1998. Oxidoreductases

and lipases as dough bleaching agents. Cereal Chemistry 75, 810-814.

Goesaert, H., Brijs, K., Veraverbeke, W.S., Courtin, C.M., Gebruers, K. and

Delcour, J.A., 2005. Wheat flour constituents: how they impact bread quality, and

how to impact their functionality. Trends in Food Science and Technology, 1 – 19.

Gould, J.T., 1998. Baking around the world. In: Cauvain, S.P. and Young,

L.S.Technology of Breadmaking. Blackie Academic and Professional, New York,

197-211.

Hoefler, A.C., 2004. Hydrocolloids. Eagan Press handbook series. Minnesota,7-8.

40

Horton, H.R., Moran, L.A., Ocsh,.S., Rawn, J.D. and Scrimgeour, K.G.,(2002).

Principles of biochem istry (3ed.). Prentice Hall, USA, 493-494.

Hoseney, R.C., (1998). Principles of cereal science and technology

Kent, N.L. and Evers, A.D.,( 1994.) Kent‟s Technology of cereals: An introduction

for students of Food Science and Agriculture (4th

ed.). ElsevierScience, Oxford,

133-140.

Marsh, D.,(1998). Mixing and dough processing. In: Cauvain, S.P. and Young,L.S.

Technology of Breadmaking. Blackie Academic and Professional,New York, pp. 81-

103.

Mathewson, P.R.,(2000). Enzymatic activity during bread baking. Cereal Foods

World45, 98-101.

Michniewicz, J. Biliaderis, C.G. and Bushuk, W.,(1992). Effect of added pentosans on

some properties of wheat bread. Food Chemistry,251-257.

Morr, C.V., (1989). Whey proteins: manufacture. In: Fox, P.F. (Ed.). Developments

of dairy chemistry – 4. Elsevier science publishers Ltd., London, 245-280.

Pateras, I.M.C.,( 1998) Bread spoilage and staling. In: Cauvain, S.P. and Young,

L.S.Technology of Breadmaking. Blackie Academic and Professional, New York,

240-256.

Poldermans, B. and Schoppink, P.,( 1999). Controlling the baking processes and

product quality with enzymes. Cereal Foods World,132-135.

Pomeranz, Y.,( 1991). Functional properties of food components 2nd(ed.). Academic

Press, San Diego, California, 95-103.

Pomeranz, Y. and Shellenberger, J.A.,(1971). Bread Science and Technology. AVI

Publishing, Westport, Connecticut, 1-16

Michniewicz, J., Biliaderis, C.G. and Bushuk, W.,( 1992). Effect of added pentosans

on some properties of wheat bread. Food Chemistry,251-257.

41

Pateras, I.M.C., (1998.) Bread spoilage and staling. In: Cauvain, S.P. and Young, L.S.

Technology of Breadmaking. Blackie Academic and Professional, New York, 240-

256.

Poldermans, B. and Schoppink, P.,(1999). Controlling the baking processes and

product quality with enzymes. Cereal Foods World,132-135.

Pomeranz, Y., (1991)Functional properties of food components 2nd(ed.). Academic

Press, San Diego, California, 95-103.

Pomeranz, Y. and Shellenberger, J.A., (1971) Bread Science and Technology. AVI

Publishing, Westport, Connecticut, 1-16

Stauffer, C.E., (1989). Principles of dough formation. In: Cauvain, S.P. and Young,

L.S.,Technology of Breadmaking. Blackie Academic and Professional, New York,

262-292.

Stauffer, C.E., (2000). E mulsifiers anti-staling agents. Cereal Foods World, 106-110.

Sullivan, B. and Allison Howe, M., (1933). Lipases of wheat. Journal of the American

Chemical Society,320-324.

Vanhamel, S., Cleemput, G., Delcour, J.A., Nys, M. and Darius, P.L., (1993)

Physicochemical and functional properties of rye non-starch polysaccharides. IV. The

effect of high molecular weight water soluble pentosans on wheat bread quality

in a straight dough procedure. Cereal Chemistry, 306-311.

Wiggins,C., (1998). Proving, baking and cooling. In: Cauvain, S.P. and Young, L.S.

,Technology of Breadmaking. Blackie Academic and Professional,New York, 120 -

134.

Williams, T. and Pullen, G.,(1998). Functional ingredients. In: Cauvain, S.P.and

Young, L.S., Technology of Breadmaking. Blackie Academic and Professional,

New York, 45-79.

Yin, Y. and Walker, C.E.,(1992). Pentosans from gluten-washing wastewater:

Isolation, characterization and role in baking. Cereal Chemistry,592-596.

Body of Thesis

Documents

wheat wheat

wheat flour wheat flour

soft wheat

strong wheat

white wheat

cultivation of wheat

main wheat varieties

total wheat proteins