Effect of Okara on the Sensory Quality of Cake

Research in Health and Nutrition (RHN) Volume 2, 2014

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Effect of Okara on the Sensory Quality of Cake Li Wang1,2,3,4, Chenjie Wang1,2,3,4, Tong Chang1,2,3,4, Liu Shi1,2,3,4, Hong Yang1,2,3,4*, Min Cui5 College of Food Science and Technology, Huazhong Agriculture University, Wuhan, Hubei 430070, China.

Key Laboratory of Environment Correlative Dietology, Huazhong Agricultural University, Ministry of Education, Wuhan, Hubei, 430070, China.

3National R&D Branch Center for Conventional Freshwater Fish Processing (Wuhan), Wuhan, Hubei, 430070, China.

4Aquatic Product Engineering and Technology Research Center of Hubei Province, Wuhan, Hubei, 430070, China.

5State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei 430070, China.

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* yangh@mail.hzau.edu.cn Received 13 Jun, 2013; Accepted 10 Nov, 2013; Published 10 Jan, 2014 Š 2014 Science and Engineering Publishing Company

Abstract Soy food industry produces approximately 20 million tons wet residue (okara) per year in China. The okara is full of protein and dietary fiber, which has significant benefits for human health. The objective of this study was to evaluate the sensory properties of cakes by adding the okara.

Hedonic sensory method was used to evaluate cakes with the okara: 0%, 5%, 10%, 15% and 20% substitution. Results showed that the crumb color and the taste of cakes were not affected significantly by the okara. The flavor of cakes could be influenced when the wheat flour was replaced 15% and 20% by the okara. The overall likeness of cakes could only be affected when the wheat flour was replaced 20% by the okara. Cakes with the substitution of 5% okara obtained the highest sensory scores. Therefore, the okara could be used to improve the nutritional values of cakes.

Keywords Cake; Soy; Okara; Fiber; Sensory Evaluation

Introduction The food industry is facing the challenge of developing new food products with special wealthenhancing characteristics. China is the largest market for soy products in the world, especially for tofu. Soy contains approximately 40% of proteins, essential amino acids, calcium, phosphorus, vitamins A and B (Genta & Alvarez & Santana, 2002). Due to its rich nutrition, there is an increasing trend to add soy into foods either as entire or portion replacement (Godfrey, 2002). The Food and Drug Administration (FDA) in

the United States has announced that 25 g of soy protein per day, as part of a diet low in saturated fatty acid and cholesterol, may reduce the risk of heart disease (Genta & Alvarez & Santana, 2002). With growing number of health-conscious consumers, soybased products are becoming mainstream in the functional food industry (Xie & Huff & Hsieh & Mustapha, 2008).

The okara is a byproduct from tofu and soymilk production. It is estimated that soy food industry produces approximately 20 million tons wet okara per year (Zhang & Ye & Li & Wang, 2004). It is an excellent source of amino acids while it contains 20%27% protein, 52%-58% dietary fiber (Katayama & Wilson, 2008), minerals and vitamins (Van der Riet an der Riet & Wight & Cilliers & Datel, 1989; Mastuo, 1991).

Cellulose, one of major compounds in okara, has significantly physiological functions. For example, it can absorb endogenous cholesterol, which stays in the duodenal bile as well as exogenous cholesterol intake with other foods. Such effect can greatly reduce plasma and liver cholesterol levels, which can prevent arteriosclerosis and control high blood pressure (Zhang & Ye & Li & Wang, 2004). The cellulose can also change the time of food through the small intestine, delaying the absorption of sugar and inhibiting the rapid rise of postprandial blood glucose, which is conducive to the treatment of diabetes

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Research in Health and Nutrition (RHN) Volume 2, 2014

(Zhang & Ye & Li & Wang, 2004).

However, the okara consists of 80% moisture and is highly susceptible to microbial spoilage (Van der Riet & Wight & Cilliers & Datel, 1989). In China, okara is mainly used as animal feed or simply discarded. Since the okara has such high dietary fiber content, it could potentially be used as the ingredient in foods to improve their nutrition values, especially fiber content.

In China, western style baking products is gradually accepted by the consumers. The objective of this study was to evaluate the sensory properties of cakes with adding the okara.

Materials and Methods Materials The cake ingredients were wheat flour (Jiazhu Inc., Wuhu, Anhui, China), sugar (Sijia Food Co., Wuhan, Hubei, China), fresh whole eggs (local market, Wuhan, Hubei, China) and whipped cream (Hangzhou Seafood Ingredients Co., Hangzhou, Zhejiang, China).

The okara was obtained from a local soybean milk vendor (Wuhan, Hubei, China).

Cake Preparation The formula of cakes at five different okara levels was shown in Table 1. The okara was dried at 60°C in a forced air drying oven (Shanghai Constant Temperature Equipment Co., Shanghai, China) for 10 hours. Then the desiccative okara was crushed by a crusher (DFT-200, Linda Machinery Co., Wenling, Zhejiang, China) and the powder was to pass through an 80-mesh screen (GB6003.1-1997). Egg, whipped cream and sugar were mixed with a whisk attachment in a mixer (B15, Linshunli Inc., Guangzhou, Guangdong, China ) on speed 2 (high speed ) for 10 minutes. Wheat flour, okara and water were gradually poured into the mixer on speed 1 (low speed) for 4 minutes. When the foam volume was nearly three times than before, the cake batter was immediately poured into baking pans. The cake batter was baked at 180°C-220°C for 12 minutes in the preheated oven (CK-3, Guangzhou Dewei Thermal Equipment Co., Guangzhou, Guangdong, China).

TABLE 1 FORMULATION FOR CAKES WITH THE OKARA.

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Ingredients(g)

0%

5%

10%

15%

20%

Wheat flour Okara Sugar Egg Whipped cream Water

500 0 500 700 40 200

475 25 500 700 40 200

450 50 500 700 40 200

425 75 500 700 40 200

400 100 500 700 40 200

Then cakes were allowed to cool for half hour at room temperature and removed from the pans. Cakes were cut into dice (3×3×3 cm) and packed in polypropylene bags.

Sensory Evaluation Hedonic sensory test was used to determine the sensory properties of cakes with the okara. For this study, untrained consumers were recruited from students, staffs and faculties at Huazhong Agriculture University who were interested volunteers and informed of evaluating cakes. All samples were coded with random three-digit number before presented to the panelists, and then placed on the paper plates.

Four attributes were crumb color, flavor, taste, and overall likeness of each sample using a seven-point hedonic scale ranging from 1 (dislike extremely) to 7 (like extremely). Cakes were considered acceptable if their mean scores for overall likeness were above 4 (neither like nor dislike). All samples were evaluated in the same condition.

Statistical Analysis The sensory evaluation data were statistically processed using MATLAB7.8 R2009a (The MathWorks, Inc., Natick, MA, US). All results reported were mean values and the data were analyzed using the analysis of variance (ANOVA). Duncan’s multiple range test was used to separate the mean and statistical significance was determined at P<0.05.

Result and Discussion There were no significant differences in overall likeness of cakes among 0, 5% and 10% okara treatments (OT) (P>0.05) (Fig. 1). There were no significant differences in overall likeness between 0% and 15%, but there were significant differences among 5%, 10%, and 15%. It indicated that cakes with 5%, 10%, and 15% OT were accepted as cake with 0% OT, while panelists preferred cakes with 5% and 10% OT much more than those with 15% OT, which suggested that cakes had no notable change when the replacement is lower than 15%. The rating for the 5% and 10% OT was significantly higher than that of the 20% OT. There were no significant differences between 15% and 20% OT (P>0.05). However, overall likeness ratings for all treatments were above 4 (neither like nor dislike). It showed that all cakes were accepted by panelists. Results showed that the overall likeness of cakes was not affected when up to 15% wheat flour was replaced by the okara. It implied that consumers

Research in Health and Nutrition (RHN) Volume 2, 2014

might still accept the cakes with some amount of the okara. When edible wheat, oat, or rice bran was used to replace wheat flour for preparing cakes, these cakes had bitter/nutty/husky aftertaste, granular mouthfeel, and poor appearance and therefore their overall acceptability scores were lower than cakes without adding the bran (Lebesi & Tzia, 2011). When 15% and 20% cladodes flour as a source of dietary fiber were substitutionally added into cakes, respectively, cakes were not acceptable (Ayadi & Abdelmaksoud & Ennouri & Attia, 2009). Therefore, the okara might be a great potential to improve the quality of cakes or other food products. Moreover, if consumers were adequately informed with fiber-enriched food products, the overall likeness or acceptance could be increased (Baixauli & Salvador & Hough & Fiszman, 2008) and the consumers might pay more for fiberenriched products (Ginon & LohĂŠac & Martin & Combris & Issanchou, 2009).

There were no significant differences in the crumb color of cakes with/without the okara (P>0.05) (Fig. 2).

It indicated that there were no color differences when up to 20% wheat flour in cakes was replaced by the okara. Normally, the crust color of cakes is affected by Maillard reactions, but the crumb color highly depends on the raw materials since the increase in temperature is not high enough to cause Maillard or caramelization reaction. Protein/amino acids in the okara were not enough to significantly influence the crumb color while the fiber did not involve Maillard reaction during the baking. The crumb color of 5% OT received the highest raking. The crumb color ratings for all treatments were above 4 (neither like nor dislike). Due to the color of edible wheat, oat or rice bran, the crumb color of cakes with adding the bran was significantly affected (Lebesi & Tzia, 2011). The crumb color of cakes with adding the cladodes flour was changed remarkably (Ayadi & Abdelmaksoud & Ennouri & Attia, 2009). However, the okara did not changethe crumb color of cakes significantly.

Fig.3. showed that there were no significant differences in the flavor of cakes among 0%, 5% and 10% OT (P>0.05). Their rakings were above 4.

However, when more than 10% okara was added into cakes, the rakings of the flavor were significantly reduced lower than 4. Some of panelists indicated that there was off-cake flavor or soybean flavor in cakes when the content of the okara was over 10%. The flavor of cakes was significantly influenced by adding edible wheat, oat, rice bran (Lebesi & Tzia, 2011) or cladodes flour (Ayadi & Abdelmaksoud & Ennouri &

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Attia, 2009), due to their own flavor. However, when up to 10% wheat flour was substituted by the okara, panelists still accepted these cakes (Fig. 3).

There were no significant differences in the taste of cakes between 0% and okara-adding cakes (P>0.05) (Fig. 4). Cakes with 5% OT were much preferred by panelists, while the taste rakings for all cakes were above 4. The raking for the taste gradually decreased along with the increasing of the replacement of the okara. The taste of cakes was significantly altered by adding edible wheat, oat, rice bran (Lebesi & Tzia, 2011) or cladodes flour (Ayadi & Abdelmaksoud & Ennouri & Attia, 2009). Fig. 4 showed that the taste of cakes was not significantly changed even when 20% wheat flour was replaced by the okara.

FIG.1. OVERALL LIKENESS RATING OF CAKE WITH ADDING OKARA (DIFFERENT LETTERS INDICATE SIGNIFICANT DIFFERENT (P<0.05).

FIG.2. COLOR RATING OF CAKE WITH ADDING OKARA (DIFFERENT LETTERS INDICATE SIGNIFICANT DIFFERENT (P<0.05).

FIG.3. FLAVOR RATING OF CAKE WITH ADDING OKARA (DIFFERENT LETTERS INDICATE SIGNIFICANT DIFFERENT (P<0.05).

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Research in Health and Nutrition (RHN) Volume 2, 2014

making.” Industrial Crops and Products 30 (2009): 40-47.

Baixauli, R., Salvador, A., Hough, G., & Fiszman, S.M. “How information about fiber (traditional and resistant starch) influence consumer acceptance of muffins.” Food Quality and Preference 19 (2008): 628-635.

Godfrey, P. “Soy products as ingredients--farm to the table.”

Innovative Food Technology 14 (2002): 10-13.

FIG.4. TASTE RATING OF CAKE WITH ADDING OKARA (DIFFERENT LETTERS INDICATE SIGNIFICANT DIFFERENT (P<0.05).

Conclusions There were no significantly differences in the crumb color and the taste of cakes even when there was 20% okara substitution. The cakes with 5% and 10% OT produced the similar flavor as the control, but cakes with 15% and 20% OT failed. When up to 15% wheat flour was substituted by the okara, the overall likeness of cakes was not affected, compared with the control.

Furthermore, it was remarkable the highest sensory score obtained in cakes with the okara (5% OT).

Therefore, the okara could be used to improve the nutritional value of cakes containing higher fiber content and lower in calories, which is important to our healthy.

Genta, H.D., Genta, M.L., Alvarez, N.V., & Santana, M.S. “Production and acceptance of a soy candy.” Journal of Food Engineering 53 (2002): 199–202.

Ginon, E., Lohéac, Y., Martin, C., Combris, P., & Issanchou, S. “Effect of fiber information on consumer willingness to pay for French baguettes.” Food Quality and Preference 20 (2009): 343-352.

Lebesi, M. & Tzia, C. “Effect of the addition of different dietary fiber and edible cereal bran sources on the baking and

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Mastuo, M. “Effects of “okara tempe” on fat digestion and cholic acid metabolism in vitro.” Journal of Japanese Society for Horticultural Science 44 (1991): 399-402.

Katayama, M. & Wilson, L.A. “Utilization of okara, a byproduct from soymilk production, through the

ACKNOWLEDGEMENTS

development of soy-based snack food.” Journal of Food

The authors would like to thank for the financial support by the Fundamental Research Funds for the Central Universities (Project 2013PY096), the Ministry of Scientific and Technology China (Grant No. 2012BAD28B06) and National Science Foundation, China (Grant No. 31172294).

Science 73 (2008): S152-157.

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