Volatile lipid oxidation products.

A highly characteristic and often undesirable flavor associated with soy protein materials largely explains the slower‐than‐expected progress over recent years in the development of high‐protein foods based on soya. Apart from the inherent flavor of the bean, different flavors are produced on processing and on storage. Major problems are the absence of an attractive positive flavor, the presence of off‐flavors of several kinds, the tenacious binding of such flavors to the soy protein molecules, and the difficulties of removing and/or masking these unacceptable qualities. This review provides a reappraisal of current literature evidence relating to each of these aspects and summarizes published patents of processes for soy flavor improvement.

Soy flavor and its improvement

The antioxidative activity of ethanolic extracts of canola meal at 100, 200, 500 and 1000 ppm on refined-bleached (RB) canola oil was examined and compared with commonly used synthetic antioxidants, such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), BHA/BHT/monoglyceride citrate (MGC) andtert-butyl-hydroquinone (TBHQ). Stability of RB oil was monitored under Schaal oven test conditions at 65°C over a 17-d period. Progression of oxidation was monitored by weight gain, peroxide, conjugated diene, 2-thiobarbituric acid and total oxidation values. Canola extracts at 500 and 1000 ppm were more active than BHA, BHT and BHA/BHT/MGC and less effective than TBHQ at a level of 200 ppm.

Canola extract as an alternative natural antioxidant for canola oil

The anisidine test, a measure of secondary oxidation products in glyceride oils, was applied to a number of soybean salad oils processed from sound and damaged soybeans. A highly significant correlation (-0.68) was found between the anisidine values of salad oils from sound soybeans and their flavor scores. Multiple correlations between flavor scores, anisidine, and peroxide values yielded a correlation of 0.81 and provided a method for predicting the initial flavor scores of sound soybean salad oils. Similar data for oils from damaged beans gave a highly significant, but lower, correlation (-0.65). Comparative studies indicated that sound crude oils usually contain lower levels of oxidation products than damaged crude. Oxidation in both sound and damaged etudes increased roughly in proportion to iron content. Reproducibility of the test and the effects of hydrogenation, accelerated storage, and fluorescent light on anisidine values were studied. Analysis of damaged oils before and after deodorization showed that little, if any, reduction of anisidine value occurred. Deodorization of sound oils, however, lowered anisidine values. In comparison with damaged oils, the anisidine values of sound oils were lower at comparable stages of processing. The poor quality of damaged soybean oil was substantiated by organoleptic evaluations. Flavor scores of oils given special processing treatments increased as anisidine values decreased.

http://rd.springer.com/content/pdf/10.1007%2FBF02545207.pdf

Oxidation and Quality of Soybean Oil: A Preliminary

Comparison of standard and NMR methodologies for assessment of oxidative stability of canola and soybean oils.

Means of evaluating soybean oil for flavor on a “now” basis and on a “predictive” basis are presented. Emphasis is placed on more recent objective methodology for measuring oil volatiles and using their correlation with flavor. Applications of a modified volatile technique for use with soy isolates or soy proteins is shown. The importance of sensory analysis and a summary of methodology currently being used are discussed.

H. W. Jackson

Papers

Techniques for flavor and odor evaluation of soy oil