71A-61 |
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V. SIKAND, Dairy Products Technology Center, California Polytechnic State University, 1 Grand Avenue, San Luis Obispo, CA 93407 and P. S. Tong, Dairy Products Technology Center, California Polytechnic State Univ., 1 Grand Ave., San Luis Obispo, CA 93407. Whey protein nitrogen index (WPNI) is a well known method of classifying nonfat dry milk powder (NFDM) based on its heat treatment. This classification scheme provides one criterion for the selection of high, medium or low heat NFDM for food applications. However, the effects of variation in NFDM composition on WPNI are not well understood. The objective of this study was to determine the effects of changing protein to lactose ratio in low heat NFDM on WPNI value. Edible spray dried lactose was used to standardize NFDM to a protein content ranging from 35% - 30% on a wet basis. These powders were analyzed for WPNI by American Dry Products Institute method. Powders were also analyzed for protein, lactose, ash, fat, and moisture by standard methods. The entire experiment was replicated twice and samples of each standardized powder were analyzed in duplicate. NFDM with 35% protein had a WPNI of 6.36 ± 0.36 mg/g, while the same NFDM standardized to a protein content of 30% with lactose had a WPNI of 5.4 ± 0.20 mg/g. Similarly, when low-heat NFDM containing 35% protein (WPNI=6.36 mg/g) was standardized with lactose to ≤ 33% protein, the WPNI value decreased to ≤ 5.8 mg/g. Using linear regression, WPNI was found to be positively related to percent protein (P<.001). A correlation coefficient of 0.83 was obtained from the equation:Y=0.057 + 0.178 X (residual error=0 .0207) where: Y=WPNI and X=% Protein. In addition, as the protein content of standardized NFDM decreased from 35% to 30%, mean values for ash, moisture, and lactose ranged from 7.66%-6.50%, 3.36%-2.79%, and 52%-55% respectively. We conclude standardization of NFDM with lactose can change its composition, WPNI value and effect its heat classification.
Session 71A, Dairy Foods: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |