Effect of extrusion cooking on the antioxidant activity of extruded half product snacks made of yellow corn and pumpkin flours

Volume 8, Issue 4 2012 Article 22

International Journal of FoodEngineering

Effect of extrusion cooking on the antioxidantactivity of extruded half product snacks made

of yellow corn and pumpkin flours

Nuria Elizabeth Rocha-Guzman, Instituto Tecnologico deDurango

Jose Alberto Gallegos-Infante, Instituto Tecnologico deDurango

Carlos Ivan Delgado-Nieblas, Instituto Tecnologico deDurango

Jose de Jesus Zazueta-Morales, Universidad Autonoma deSinaloa

Ruben Francisco Gonzalez-Laredo, Instituto Tecnologicode Durango

Veronica Cervantes-Cardoza, Instituto Tecnologico deDurango

Fernando Martinez-Bustos, CINVESTAV-QROErnesto Aguilar-Palazuelos, Universidad Autonoma de

Sinaloa

Recommended Citation:Rocha-Guzman, Nuria Elizabeth; Gallegos-Infante, Jose Alberto; Delgado-Nieblas, Carlos Ivan;Zazueta-Morales, Jose de Jesus; Gonzalez-Laredo, Ruben Francisco; Cervantes-Cardoza,Veronica; Martinez-Bustos, Fernando; and Aguilar-Palazuelos, Ernesto (2012) "Effect ofextrusion cooking on the antioxidant activity of extruded half product snacks made of yellowcorn and pumpkin flours," International Journal of Food Engineering: Vol. 8: Iss. 4, Article 22.

DOI: 10.1515/1556-3758.2284

©2012 De Gruyter. All rights reserved.Brought to you by | Universidad Autonoma de SinaloaAuthenticated | 148.227.22.70

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Effect of extrusion cooking on the antioxidantactivity of extruded half product snacks made

of yellow corn and pumpkin floursNuria Elizabeth Rocha-Guzman, Jose Alberto Gallegos-Infante, Carlos Ivan

Delgado-Nieblas, Jose de Jesus Zazueta-Morales, Ruben Francisco Gonzalez-Laredo, Veronica Cervantes-Cardoza, Fernando Martinez-Bustos, and Ernesto

Aguilar-Palazuelos

AbstractThe effect of the extrusion on the antioxidant activity of extruded half product snacks made of

pumpkin and corn flour blends was evaluated. Cehualca pumpkin and yellow corn flours were used.Pumpkin (0.5 to 15.6 %) and yellow corn flours were mixed and then extruded at a temperaturerange of 93.5–140.5°C. The total phenolic content (TPC) was determined by Folin-Ciocalteumethod. The Phenolic acid profile was obtained by HPLC analysis. The antioxidant capacity wasmeasured using DPPH*, deoxyribose, and LDL oxidation inhibition assays. A central compositerotatable design was applied. The highest value of TPC was observed at high extrusion temperatureand low pumpkin levels, and at low temperature and high level of pumpkin flour concentration. Thehighest DPPH scavenging activity was obtained at higher content of yellow corn flour. The bestresponse to OH* scavenging was observed at higher extrusion temperature and lower content ofpumpkin.

KEYWORDS: antioxidant, extrusion, half-extrusion, pumpkin flour, snack, yellow corn flour

Author Notes: AcknowledgementsThis work was supported partially by Universidad Autónoma de Sinaloa. Author CIDN thanksGraduate Scholarships from CONACyT-Mexico and DGEST-México

Brought to you by | Universidad Autonoma de SinaloaAuthenticated | 148.227.22.70


INTRODUCTION Extrusion cooking is an important processing technique in the polymer and food industry as it is considered to be an efficient manufacturing process (Anton et al., 2009). Extruded foods are composed mainly of cereals, starches and in minor proportion of fruits and vegetables. The main role of these ingredients is to give structure, texture, and mouth feel, bulk and quality characteristics to the product (Tahnoven et al., 1998). The extrusion process combines unit operations such as mixing, conveying, and heating under conditions of high shear and compression. The exposure of feed material to high temperature for a short time has a favorable effect on the destruction of microorganisms and the degradation of heat-labile antinutrients.

The growth of the extruded snack food market has been extensive. This trend is reflected globally with snack foods becoming an integral part of the diet of the world´s population (Thakur and Saxena, 2000).

A lot of work has been done about the effects of extrusion conditions on the properties of several cereal flours and starches, and tend to be low in protein and have a low biological value (Iqbal et al., 2006) (Ding et al., 2005; Ding et al., 2006). There are also few studies about the effect of extrusion process on the product antioxidant properties. Stojceska et al. (2009) showed that the use of extruded blends of wheat flour and corn starch added with several food by-products increased total antioxidant capacity and total phenolic contents. Shih et al. (2009) found that extruded sweet potatoes increased DPPH radical scavenging effect and their total phenolic content. Opposite to these results, Camire et al. (2007) showed that using fruit powders blends in extruded corn breakfast cereals did not increase the antioxidant activity of extruded cornmeal measured by the ABTS test. Delgado-Licon et al. (2009) reported that in general lower phenolic content was found in extruded blends of common bean – corn flours in comparison with a corn control.

There are several types of extruded products and most of them are ready to eat, but there are a specific type known as extruded half-products or third generation snacks. This type of products are cooked in an extruder barrel, cooled, forced through the die and shaped below 100°C to prevent puffing (Moore, 1994). Extrudates are then dried to less than 12% of moisture as half-products, which can be expanded into low-density products by frying, microwaving, etc. (Suknark et al., 1998).

Pumpkin is native from America. It is a member of the Cucurbitaceae, a wide family that includes other fruits as melon, watermelon and cucumber (Gonçalves et al., 2007). The most studied pumpkins are Cucurbita pepo called squash, Cucurbita maxima Duch., called winter squash, and Cucurbita moschata called Cehualca. Pumpkin fruits are consumed both immature and ripe. The flesh

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Rocha-Guzman et al.: Effect of extrusion on the antioxidant activity

Published by De Gruyter, 2012



of the fruit can be boiled, canned, dried or processed to obtain juice and pomace (Zawirska et al., 2009).

It is believed that pumpkin is a healthy food, because is rich in starch, free sugars, and vitamins such as B1, B2 and C, as well as several bioactive ingredients, including β-carotene. Pumpkin is also a source of polyphenols although there are very few reports about its phenolic profile. Nakamura et al. (1998) reported that wild pumpkin shows the same level of total phenolic content as commercial pumpkin.

There are many traditional foods that use pumpkin as ingredient like pumpkin cake, pumpkin congee, etc. (Incedayi et al., 2009). Pumpkin flour is currently the main processed product from pumpkin fruit because it can be easily stored for a long time and conveniently used in the manufacturing of formulated foods. The addition of pumpkin flour enhances nutrient content of several food products and improves their flavor.

Zea mays contains more total polyphenols and higher antioxidant capacity than cereals like wheat, rice and oats (Adom and Liu, 2002). The major phenolic compound is ferulic acid, which is concentrated in the grain pericarp and represents about 85% of the total phenolic content (Cabrera-Soto et al., 2009). Phenols in cereals fall into soluble and insoluble or linked category. Free phenols, glycosylated and esterified, are found in greater amounts in the peripheral layers of grain (pericarp, testa and aleurone), while their concentration is lower in the endosperm (Yu et al., 2001).

From our knowledge, there are no reports about extruded half-products of pumpkin/yellow corn flours and the effect of extrusion on their antioxidant properties. Therefore the objective of this work was to evaluate the effect of extrusion on the antioxidant activity of extruded half snacks from blends of pumpkin and corn flours.

MATERIALS AND METHODS Commercial corn starch (Industrializadora de Maíz –IMSA–, S.A de C.V., México), was obtained from a local grocery store (Culiacán, Sinaloa, México). The pumpkin flour was prepared from Cehualca pumpkins (Cucurbita moschata D.) bought at a local market (Culiacán, Sinaloa, México). Pumpkin flesh was cut in 2 mm parts and then blanched (95 ± 2°C) by 2 min. Samples were dried in a tray-dryer at 1.45 m/s of air rate, 72°C and 110 min. The samples were ground in a prototype mill (mean particle size 240 nm).

Yellow corn flour

Yellow corn grain (Zea mays) was obtained from a local food distributor at Culiacan, Sinaloa, México. The grain was ground and sieved to obtain a mean

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International Journal of Food Engineering, Vol. 8 [2012], Iss. 4, Art. 22



particle size of 231 nm. Mill and sieves were constructed at the University of Sinaloa, Mexico.

Extruded half product process

Samples of pumpkin flour, yellow corn flour and water were mixed according to conditions described in Table I. A single screw extruder Brabender (Compression rate 2:1) was used at constant screw speed of 75 rpm. At the beginning zone of barrel the temperature was 75°C. Temperature at the blend zone was ranged as described in Table I. Temperature at the end was constant (75°C). Obtained pellets were dried at room temperature (30°C) to less than 12% of moisture.

Table 1. Operating ranges of the extrusion process

Variables Extruder conditions

Extrusion Temperature

93.5 °C 117°C 137°C 140.5°C

Pumpkin flour 0.5 % 7 % 8 % 15.6 % Moisture % 21.3 % 25 % 28 % 34.7 %

Extraction procedure

Samples (80g) were extracted with 70% aqueous acetone (200mL) for 24h at room temperature in agitation. Crude extracts were concentrated under vacuum at 40°C in a rotary evaporator (Buchi, model R-200/250, Flawil, Switzerland). The resulting aqueous solutions were lyophilized to a powder and stored in dark at 4°C until analysis. Extractions were performed by duplicate. Experimental samples were always protected from light (Waterman and Mole, 1994).

Polyphenol content

Total phenolic content (TPC) in extracts from experimental samples were determined by a Folin-Ciocalteu modified method (Heimler et al., 2006), using gallic acid as standard and expressing the results as meq of catechin (mg catechin/g of sample).

High Performance Liquid Chromatography (HPLC)

A Waters 600 HPLC system equipped with a UV/ Vis detector (Waters 2487) (Milford, MA, USA) and auto-sampler (Waters 717 plus) was used for the analysis. The separation was carried out in a Phenomenex ODS-C18 column (250 X 4.6 mm, 5 µm). The binary mobile phase consisted of water containing 0.6% acetic acid (solvent A), and acetonitrile (solvent B). All solvents and samples were filtered through a 0.45 µm filter prior to use. The flow-rate was kept constant at 1.0 mL/min for a total run time of 45 min. The system was run with a

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gradient program: 0–25 min, 95% to 70% A; 25–30 min, 70% to 40% A; 30–35 min, 40% to 60% A; and 35–45 min, 60% to 95 % A. The sample injection volume was 10 µL. Peaks of interest were monitored at 280 nm and 320 nm.

Antioxidant capacity assays

The antioxidant capacity as the radical scavenging activity (RSA) was measured using the DPPH* (2,2,-diphenyl-1-picrylhydrazyl) method (Brand-Williams et al., 1995). A calibration curve at 515nm (UV/Vis Spectrophotometer, Varian, Cary 50, Varian, Palo Alto, CA, USA. Cary 50) was made to calculate the remaining DPPH* concentration in the reaction medium at several concentrations (0-1000µg/mL). A volume of 1.9mL of DPPH* in methanol was used.

Deoxy-D-ribose assay

The hydroxyl radical scavenging was evaluated using the deoxyribose degradation assay (Re et al., 1999). The assay mixtures, containing the sample at several concentrations (1, 10, 100 and 1000 µg/mL) was used at a final volume of 1mL, that is, 1mM in deoxyribose, 24mM in sodium phosphate (15mM NaCl, pH 7.4), 0.1mM in FeCl3, 0.1mM in 2-[2- (Bis (carboxymethyl) amino) ethyl-(carboxymethyl) amino] acetic acid (EDTA), 1mM in H2O2, and 0.1mM in ascorbic acid. After incubation at 37°C for 1h, color development was promoted adding 1.5mL of 28% (w/v) TCA and 1.0mL of 1% (w/v) TBA in 0.05MNaOH, followed by heating at 100°C for 15min. Inhibition of deoxyribose degradation was expressed as percent decrease in absorbance, when compared to the control (assay without sample).

LDL Oxidation inhibition

Human plasma samples from healthy volunteers were poured in plastic tubes with EDTA (1 mg/mL) and treated with a kit for low density lipoproteins (LDL) precipitation (Biosystems, Zapopan, Mexico). Isolated LDL (0.2 mg/mL) was incubated at 37°C with CuSO4 (25mM/L) and different concentrations of extracts for 3h. CuSO4 (25 mM/L) at the same conditions was taken as control. The amount of peroxides was evaluated by the thiobarbituric acid method following procedure proposed by Loy et al. (2002).The amount of protein was determined by the Bradford method.

Statistical analysis

A central composite rotatable response surface design (Owusu-Ansah et al., 1983) was used, with the overall ranges and selected variables tabulated in Table I. The general nonlinear model option of the Statistica Software (StatSoft, Tulsa, OK) was used to analyze data, and the graphs module from the same software, (three dimensional plotting graphs) was used to plot the generated regression equations.

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The moisture variable was not significant in any case, so, these variables were deleted in the final developed models.

RESULTS AND DISCUSSION Results from the evaluation of total phenolic content are described in Figure 1. It is possible to depict in the figure two zones with higher phenolic content. One distinctive zone is at high extrusion temperature and low levels of added pumpkin flour; another is at low extrusion temperatures and higher levels of added pumpkin flour. This behavior could be associated to the increased levels of TPC associated to yellow corn flour, which has been observed by Stojceska et al. (2009) and Dewanto et al. (2003) for processed corn. Similarly, several reports about influence of heat on the TPC of pumpkin and cabbages have been addressed (Azizah et al., 2009). TPC in this product is higher in function of the original TPC in yellow corn flour. TPC values for our corn samples were higher than those reported for white, yellow, red, purple and black corn extracts (Cabrera-Soto et al., 2009) (0.33–6.8 mg/g), although in the present report the yellow corn was processed two times, first at the flour production and second in the extrusion process. However, these values were lower than those reported by Lopez-Martinez et al. (2009) for unprocessed yellow corn extracts.

Phenolic compounds identified by HPLC analysis are shown in Table II. From these results is interesting to compare treatments 9 and 10, because the only difference is the temperature used, at higher temperatures (treatment 10) morin, rutin, catechin, caffeic and gallic acid were detected. At low temperature only catechin and gallic acid were identified. The compounds detected at higher temperatures could be associated to liberation of bounded polyphenols especially from yellow corn flour (Dewanto et al., 2003). This hydrolysis was improved at higher temperatures.

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Figure 1. Effect of temperature and pumpkin flour on the total phenolic content

Figure 2. Effect of temperature and pumpkin flour content on the radical scavenging activity (RSA) by the DPPH* test

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Table II. Phenolic compounds in experimental samples identified by HPLC

Temperature, °C

Pumkin flour, %

Phenolic compounds, (mg/100g)

93.5 8 Catechin (598.6) Gallic acid (1.68)

117 0.5 Morin (2367.8) Catechin (1601.0) Gallocatechin (63.7) Naringenin (9.54)

117 8 Morin (2362.6) Gallocatechin gallate (1836.3) Catechin (1599.8) Gallic acid (50.55)

117 15.6 Rutin (2199.4) Catechin (1602.0) Caffeic acid (140.3) Gallic acid (38.72)

137 7 Morin (2361.9) Caffeic acid (143.18)

140.5 8 Morin (2362.4) Rutin (2200.6) Catechin (1600.0) Caffeic acid (142.31) Gallic acid (37.68)

Raw material control Pumpkin flour Morin (2361.1) Catechin (1599.6)

Yellow corn flour Morin (2368.3) Catechin (1602.5)

Antioxidant capacity assays

Results obtained for the radical scavenging activity (RSA) of DPPH are shown in Figure 2. From these results it can be observed that at higher content of pumpkin flour, the RSA of extruded samples was lower, this behavior could be associated to a dilution effect, because corn have a higher phenolic content and good RSA activity according to Dewanto et al. (2003). The best treatment (17.46% of RSA) was obtained at higher content of yellow corn flour and the lower RSA (4.68%) was associated to the highest content of pumpkin flour extrudates. Delgado-Licon et al. (2009) found that extrusion caused a reduction in total phenolics of extruded blends of corn/bean flour, similar results were reported in extruded sweet potato samples (Shih et al., 2009), which showed the highest RSA using DPPH test in comparison with other treatments. This behavior could be associated to liberation of ferulic acid by the extrusion process (Zielinski et al., 2001). However, Grela et al. (1999) found that extrusion lowers antioxidant capacity in plant materials, similar results were described by Delgado-Licon et al. (2009), although they claim that reduction in RSA was marginal for extruded blends of bean/maize flour.

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Several authors have found that corn extracts are higher in antioxidant capacity, especially in purple-colored strains (Lopez-Martinez et al., 2009). They reported 20% of RSA for alcoholic extracts from yellow corn related to free phenolics and 40% for total phenolics. These results are similar to those found in the present work. Also, several reports indicate that pumpkin squash show a poor antioxidant quality in comparison with several fruits and vegetables (Chun et al., 2005).

Deoxy-D-Ribose

Results from the deoxy-D-ribose assay are shown in Figure 3. From this Figure is possible to observe that the highest value of OH* scavenging was obtained at higher extrusion temperatures and at low pumpkin flour content. This behavior correlates well with the DPPH test. Thus, at lower pumpkin flour level, there is more corn flour content, and the behavior could be associated to this ingredient. However, there is also a gradual increment on this activity at lower temperatures with the addition of pumpkin flour, which suggests the release of bioactive compounds such as beta-carotene and lycopene, despite the degradation of thermo labile phenolics (Azizah et al., 2009).

LDL oxidation inhibition

Results from the LDL oxidation inhibition model are shown in Figure 4. The best condition for inhibition of LDL oxidation was observed at higher extrusion temperatures with higher level of pumpkin flour. This behavior could be associated to gallic acid and catechin. The capacity of these phenolic compounds for inhibiting LDL oxidation was reported by Frankel et al. (1995) in twenty wines from California. In Table II is shown that there are higher concentrations of gallic acid, catechin and rutin. Brown et al. (1998) found that rutin prolongs the lag phase of LDL oxidation in a dose-dependent manner such as luteolin does. Rutin also decreased the propagation rate of LDL oxidation as quercetin. Thus, according to these authors, less hydrophobic compounds as quercetin and rutin decreased the propagation rate, because there is greater accessibility to the Cu2+

during the course of the LDL oxidation.

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Figure 3. Effect of temperature and pumpkin flour content on the radical scavenging activity (RSA) by the deoxy-D-ribose method

Figure 4. Effect of temperature and pumpkin flour content on the inhibition of LDL

On the other side, the higher LDL oxidation inhibition observed at low level of pumpkin flour (i.e., 100% corn flour) could be associated to the higher presence of ferulic acid in corn (Adom and Liu, 2002; Lopez-Martinez et al., 2009). However, the antioxidant effect on LDL by ferulic acid has been reported as weak by several authors (Cirico and Omaye, 2006). Cheng et al. (2007) found by

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kinetic analysis that hydroxycinnamic acid derivatives, as ferulic acid, are effective against Cu2+ induced LDL peroxidation and that molecules bearing ortho-dihydroxyl or 4-hydroy-3-methoxyl groups have significantly higher antioxidant activity. Cirico and Omaye (2006) demonstrated that ferulic acid in presence of low levels of other phenolic compounds increased significantly its antioxidant capacity. Also, higher levels of catechin and morin increased the inhibition of the LDL oxidation. Naderi et al. (2003) studied morin, finding that it has stronger inhibitory activity against LDL oxidation in comparison to biochanin A or apigenin.

CONCLUSIONS Half extruded snacks made of pumpkin/corn flours blends showed antioxidant activity in function of corn flour concentration and temperature. The influence of humidity was not significant. Response surface methodology indicates that the best condition for OH* scavenging is lower levels of pumpkin flour in the blends and higher extrusion temperatures. Also, the best condition for inhibition of LDL oxidation was using low levels of pumpkin flour and low temperature of extrusion, and using higher levels of pumpkin flour and high temperature of extrusion.

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Effect of extrusion cooking on the antioxidant activity of extruded half product snacks made of yellow corn and pumpkin flours

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