71A-36 |
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W. WANG-NOLAN, G. Mattas, and P. S. Tong. Dairy Products Technology Center, California Polytechnic State Univ., One Grand Ave., San Luis Obispo, CA 93407 Heat stability is an important attribute in concentrated dairy products. A large change in viscosity after heating is usually an indication of poor heat stability. The factors affecting the viscosity in concentrated dairy products such as milk composition, process temperature, heating duration, and other processing conditions are not well understood. The objective of this study was to determine the effects of skim milk powder (nonfat dry milk) protein to lactose ratio (P/L) adjustment on rheological properties and age thickening rate of concentrated dairy products, specifically recombined sweetened condensed milk (RSCM). The skim milk powder used in this study contained 36% protein, 52% lactose, and 3.2% moisture. The P/L was varied between 0.54 and 0.69. Skim milk powder was blended with lactose powder or milk permeate to adjust P/L. Factorial experimental design was used in this study. The variables were: two lactose sources (edible fine lactose powder and milk permeate) and three levels of P/L (0.69, 0.61, and 0.54). The experiment was replicated three times. The heat treatment used to process RSCM remained the same throughout the study—85 °C for 2 min. The results showed that using lactose powder decreased the initial viscosity of freshly made RSCM and decreased age thickening rate during storage. Mean viscosity of RSCM at 0.69 P/L was 22 ± 5% higher than mean viscosity at 0.61 P/L. Lower protein to lactose ratio in RSCM also reduced the rate of age thickening by 36 ± 7% during the first four-wk storage. In addition to varying P/L, milk permeate also increased minerals and nitrogen content in skim milk powder compared to lactose powder. Similar trends were observed when milk permeate was used in the study. Downward standardization of U.S. skim milk powder would make U.S. powder more consistent in composition and functionality, as well as more competitive in price.
Session 71A, Dairy Foods: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |