Protein Solubility as Quality Index for Processed Soybean
Keywords:
soybean meal, urease index, protein dispersibility index, protein solubility, nitrogen solubility indexAbstract
Protein quality of soybean meal (SBM) is linked to both the reduction of antinutritional factors (ANFs), and the optimization of protein digestibility. Both insufficient- and over-heating result in poor quality SBM. Inadequate heating fails to completely destroy the ANFs, which may have a detrimental impact on animal performance, while excessive heating reduces the availability of lysine via the Maillard reaction and possibly, to a lesser extent, of other amino acids. The objective of our study was to compare some biochemical laboratory procedures for assessing quality of SBM: urease index (UI), protein dispersibility index (PDI), KOH protein solubility (PS), and nitrogen solubility index (NSI). The experimental data reveal that UI is not useful to determine excessive heat treatment since additional heating has no effect on the urease index. KOH protein solubility remains high, during initial heat treatment. In marked contrast, the PDI and NSI decreased incrementally from 78% to 20% and from 97% to 60%, respectively, when heating 0 to 30 minutes. Combing the PDI test with the urease test could be useful to monitor soybean quality. SBM containing low UI (0.3 or below) and high PDI (40 to 45%) may indicate that the sample is definitely high quality because it has been adequately heat processed, but not overprocessed.
References
Nelson, A. I., Wei, L. S., Steinberg, M. P., Foods from whole soybeans, Proceedings of World Soybean Research Conference, ed. F. T. Corbin, West View Press, Boulder, CO, 1980, 745-762.
Liener, I. E., 1994, "Implications of antinutritional components in soybean foods", Critical Reviews in Food Science and Nutrition, 1994, 34, 31-67.
Oshodi, A. A., Ipinmoroti, K.O., In vitro multi-enzyme digestibility of protein of six varieties of African yam bean flours, Journal of Science Food and Agriculture, 1995, 69, 373-377.
Liu, K., Chemistry and nutritional value of soybean components, In: Soybeans, Chemistry, Technology and Utilisation, Chapman and Hall, 1997, pp. 36-95.
Maforimbo, E., Nguyen, M., Skurray, G.R., The effect of l-ascorbic acid on the rheological properties of soy-wheat dough: a comparison of raw and physically modified soy flours, Journal of Food Engineering, 2006, 72, 339-345.
Badley, R. A., Atkinson, D., Hauser, H., Oldani, D., Green, J. P., Stubbs, J. M., The structure, physical and chemical properties of the soybean protein glycinin, Biochimica et Biophysica Acta, 1975, 412, 214-228.
Hashizume, K., Watanabe, T., Influence of heating temperature on conformational changes of soybean proteins, Agricultural and Biological Chemistry, 1979, 43, 683-695.
Del Valle, F. R., Nutritional qualities of soya protein as affected by processing, Journal of the American Oil Chemists’ Society, 1981, 58, 419-429.
Skrede, A., Krogdahl, A., Heat affects nutritional characteristics of soybean meal and excretion of proteinases in mink and chicks, Nutrition Reports International, 1985, 32, 479-489.
Araba, M, Dale, N. M., Evaluation of protein solubility as an indicator of over processing soybean meal, Poultry Science, 1990, 69, 76-83.
Batal, A. B., Douglas, M. W., Engram, A. E., Parsons, C. M., Protein dispersibility index as an indicator of adequately processed soybean meal, Poultry Science, 2000, 79, 1592-1596.
Căpriţă, R., Principii si tehnici in biochimie, Mirton, Timisoara, 2001, pp. 125-126.
Lee, H., Garlich, J. D., Effect of overcooked soybean meal on chicken performance and amino acid availability, Poultry Science, 1992, 71, 499-508.
Soybean Growers for Feed Industry, Info Source 2009. http://www.soymeal.org/infosource/august09/09
augustinfosource.pdf
