**High Pressure Treatments of Soybean and Soybean Products**

Kashif Ghafoor1, Fahad Y.I. AL-Juhaimi1 and Jiyong Park2 *1Department of Food and Nutrition Sciences, King Saud University, Riyadh, 2Department of Biotechnology, Yonsei University, Seoul 120-749, 1Saudi Arabia 2South Korea* 

#### **1. Introduction**

66 Recent Trends for Enhancing the Diversity and Quality of Soybean Products

O'Brien, R.D. (2004). *Fats and Oils Formulating and Processing for Applications*, CRC Press,

Orthoefer, F.T. (1978). Processing and utilization. In: *Soybean: physiology, agronomy and* 

Padín, S.; Bello, G.D. & Fabrizio, M. (2002). Grain loss caused by *Tribolium castaneum*,

Ramalho, V.C. & Jorge, N. (2006). Antioxidantes utilizados em óleos, gorduras e alimentos gordurosos. *Química Nova*, Vol.29, No.4, (July 2006), pp. 755-760, ISSN 0100-4042 Saio, K.; Nikkuni, I.; Ando, Y.; Osturu, M.; Terauchi, Y. & Kito, M. (1980). Soybean quality

Santos, C.M.R.; Menezes, N.L. & Villela, F.A. (2004). Alterações fisiológicas e bioquímicas

Silva, F.A.M.; Borges, M.F.M. & Ferreira, M.A. (1999). Métodos para avaliação do grau de

Silva, J.S.; Berbert, P.A.; Rufato, S. & Afonso, A.D.L. (2008). Indicadores da qualidade dos

Sinclair, J.B. (1995). Reevaluation of grading standards and discounts for fungus-damaged

Sinha, R. N. & Muir, W.E. (1973). *Grain storage: part of a system,* Avi Pub. Co., ISBN

Vieira, R.D.; Penariol, A.L.; Perecin, D. & Panobianco, M. (2002). Condutividade elétrica e

Wilson, R.F.; Novitzky, W.P. & Fenner, G.P. (1995). Effect of fungal damage on seed

Zadernowski R.; Nowak-Polakowska H. & Rashed, A.A. (1999). The influence of heat

teor de água inicial das sementes de soja. *Pesquisa Agropecuária Brasileira*, Vol.37,

composition and quality of soybeans. *Journal of the American Oil Chemists' Society*,

treatament on the activity of lipo and hydrophilic components of oat grain. *Journal of Food Processing and Preservation*, Vol.23, No.3, pp. 177-191, (September 1999), ISSN

 http://www.usda.gov/gipsa/reference-library/brochures/soyinspection.pdf USDA. (March 2011). *U.S. soybean inspection,* 14.03.2011, Available from

*utilization*, A.G. Norman, (Ed.)., 219-246, Academic Press, ISBN 0-12-521160-0, New

*Sitophilus oryzae* and *Acanthoscelides obtectus* in stored durum wheat and beans treated with *Beauveria bassiana. Journal of Stored Products Reseach*, Vol.38, No.1,

changes during model storage studies. *Cereal Chemistry*, Vol.57, No.2, (March 1980),

em sementes de feijão envelhecidas artificialmente. *Revista Brasileira de Sementes*,

oxidação lipídica e da capacidade antioxidante. *Química Nova,* Vol.22, No.1,

grãos. In: *Secagem e Armazenagem de Produtos Agrícolas*, J.S. Silva. (Org.), 63-108,

soybean seeds. *Journal of the American Oil Chemists' Society*, Vol.72, No.12,

ISBN 0849315999, Boca Raton, United States

(January 2002), pp. 69-74, ISSN 0022-474X

(January 2006), pp. 94-103, ISSN 0100-4042

Vol.26, No.1, (July 2004), pp. 110-119, ISSN 0101-3122

ISBN 9788562032004, Aprenda Fácil, Viçosa, Brasil

(December 1995), pp. 1415-1419, ISSN 0003-021X

USDA. (May 2006). *U.S. soybean inspection,* 31.05.2006, Available from

http://www.usda.gov/oce/commodity/wasde/latest.pdf

No.9, (September 2002), pp. 1333-1338, ISSN: 0100-204X

Vol.72, No.12, (December 1995), pp. 1425-1429, ISSN 0003-021X

087055123X, Westport, United States

0145-8892

York, United States

pp. 77-82, ISSN 0009-0352

Soybean (*Glycine max*) is an industrial crop extensively cultivated for its oil and protein content. The global demand for soybean has increased dramatically over the last few years. Since the application of high hydrostatic pressure (HHP) to different food systems in the late 1800s (Bridgman, 1914), many researchers today are again applying this promising technology to the processing of foods. There is increasing worldwide interest in the use of HHP because of the advantages of this technology over other methods of processing and preservation. HHP offers homogeneity of treatment at every point in the product due to the fact the applied pressure is instantaneously and uniformly distributed within the HHP chamber. Therefore, processing time is not a function of sample size. Important advantages in using this technology are (1) significant or total inactivation of microorganisms (Knorr, 1993), and (2) better functional and nutritional retention of ingredients in the processed products, with improved food quality parameters (Hayashi, 1989). In addition, there is significant energy economy in comparison to thermal stabilization techniques, because once the desired pressure is reached, it can be maintained without the need for further energy input. Recently, processing of foods with HHP and low to moderate temperatures (less than 70 °C) was introduced as an alternative to thermal preservation. However, it was not until the late 1980s that researchers began investigating ways to commercialize high pressure treatment of foods (Hayashi, 1989).

The main uses of soybeans can be categorized into three groups: industrial, human food and livestock feed. Soybeans for human consumption are processed in many forms. Of major importance in Asian countries are soy foods such as tofu, soy sauce, miso, soy sprouts, and soymilk. These soy foods were recently introduced to the American market as were soy flour and soymilk previously. Soy flour is often mixed with other flours to increase the protein content, and soymilk provides an alternative source of protein for people allergic to the protein in cow's milk (Riaz, 1988). In addition to its versatility, the soybean is a commodity of unique chemical composition. On a mean dry matter basis, soybeans contain about 40% protein and 20% oil. Soybeans contains the highest protein content among food crops, and are second highest with respect to oil content among all the food legumes. Thus, the composition of soy products range in protein content from about 40% for full-fat flours to 95% or more for protein isolates (Wolf & Cowan, 1975).

High Pressure Treatments of Soybean and Soybean Products 69

Fig. 1. Viable aerobic mesophilic population in tofu after treatment at 400 MPa and 5 °C for

Food constituents such as sucrose, fructose, glucose, and salts affect the baro-resistance of microorganisms present in food (Oxen & Knorr, 1993). This effect is often observed since food constituents appear to protect microorganisms from the effects of high pressure. Therefore, a non-nutritive solution can reduce the microorganism's baro-tolerance. The presence of microorganisms such as *Hafnia halvei* and *Bacillus cereus* that remained active after HHP treatment could explain the baro-protective effect that food components exert

Unlike allergenic proteins in cereals such as rice, soybeans contain a large number of proteins with important functional properties (Wolf & Cowan, 1975). Eighty percent of the proteins in soybeans are glycinin and β- and γ-conglycinin, which are globular salt-soluble proteins. On the basis of their sedimentation constants at pH 7.6 and ionic strength buffer of 0.5, the globulins are characterized as 11S or glycinin and 7S or β- and γ-conglycinin (Fukushima, 1991), with other less abundant globulins including 2S or α-conglycinin, 9S globulins, and 15S globulins. Functional properties associated with these kinds of soybean

3. Interfacial properties identified as surface tension and related foam/emulsion stability

Therefore, the method of processing intact soybeans is important since the retention of proteins in the soybean seed is of special interest because of the high-quality vegetable protein, which also contains most of the essential amino acids (Steinke et al., 1992). When soybeans are immersed in hot water at 50–60 °C for 1 h, a considerable amount of protein solubilized from the soybean seeds is released to the surrounding water (Asano et al., 1989). Later studies identified these solubilized proteins as 7S globulins, which accounted for

5, 30, and 45 min (from Prestamo et al., 2000).

**2.2 Proteins** 

proteins:

(Utsumi et al., 1998).

over the extent on microbial reduction (Prestamo et al., 2000).

1. Hydration properties such as swelling, solubility, and viscosity. 2. Protein–protein interactions resulting in precipitation and gelling.

about 3% of the total protein in mature soybean seeds (Hirano et al., 1992).
