17E-23 |
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K. RACICOT and G. M. Marando. U.S. Army Natick Soldier Center, U.S. Army Research, Development & Engineering Command, Food Directorate, Kansas St., Natick, MA 01760-5020 Attempts at fortification and long shelf life of novel high protein foodstuffs generally results in products that appear discolored, emit undesirable odors, negatively impact textural traits, and are sometimes bitter due to the degradation of the stored protein constituent. More importantly, essential nutritional qualities of the proteins added for fortification could be compromised. Therefore, there is a need to fortify novel high protein foodstuffs with nutritionally complete proteins. A clear understanding of protein degradation in high carbohydrate systems must first be determined. In this study, the objective was to monitor casein reactivity in glucose solutions. Aqueous sodium caseinate solutions at 80oF, 100oF, 120oF; 0%, 5%, 10% glucose; and 6.5, 7.5, 8.5 start pH were evaluated throughout a 50-day storage study. The solutions were tested for loss in digestibility using an in-vitro technique and the development of Maillard products detected spectrophotometrically at 420nm. Loss of digestibility accounts for half of the Protein Digestibility Corrected Amino Acid Score (PDCAAS). The score is the comparison of essential amino acid profiles of test protein versus a reference ideal. The limiting amino acid in the test protein is used, with digestibility, to calculate a PDCAAS. Any score of 1.0 or greater is considered high quality. The 120oF storage led to the development of browning to the greatest extent with minimal browning at 80oF and 100oF, but loss in digestibility was considerable at 100oF as well as 120oF. Therefore, there is loss in quality before browning takes place. Higher glucose concentration led to significant loss in digestibility and increased browning products. The data does suggest the retarding of browning products, but the acceleration of digestibility loss, at lower start pH. Initial “high” quality casein when stored at accelerated temperature in glucose solutions exhibits a drop in PDCAAS below 1.0 to a level not considered nutritionally adequate.
Session 17E, Food Chemistry: Proteins
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