14A-7 |
Influence of whey protein concentrates on yogurt texture and rheology |
I. M. SODINI1, J. W. Montella2, and P. S. Tong2. (1) Centre de reserche de Versailles-Grignon, Institut National de la Recherche Agronomique, Thiverval-Grignon, 78850, France, (2) Dairy Products Technology Center, California Polytechnic State Univ., 1 Grand Ave., San Luis Obispo, CA 93407 Contradictory results have been reported on the effect of whey protein concentrate (WPC) on yogurt texture and rheology. One possible reason for these conflicting results is variability in WPC among suppliers. The objective of the present work was to quantify the rheological and textural properties of stirred yogurt manufactured with different commercial sources of 34% protein WPC. Stirred yogurts were produced with a milk base enriched to 45 g kg -1 protein content with one of five different commercial WPC samples, or with skim milk powder (SMP) as a control. Two commercial starter cultures were used: a ropy culture (which produces exopolysaccharides), and a non-ropy culture (which does not produce exopolysaccharides). Rheological behavior (viscoelastic properties and apparent viscosity), brookfield viscosity, firmness, and water holding capacity of resulting yogurts were measured. Results were evaluated statistically by analysis of variance and multiple comparisons of treatment means. Our results showed that replacement of SMP by WPC decreased yogurt viscosity, but increased water holding capacity. The mean complex viscosity and the mean apparent viscosity for the five WPC enriched yogurts were 14 to 24 Pa.s, and 0.38 to 0.88 Pa.s respectively. In other words, there was a 50% decrease between the most viscous and the least viscous yogurt. However, mean water holding capacity was the same for the five WPC enriched yogurts (63% +/- 2% ). It was higher than for the SMP enriched yogurt (53% +/- 1%). The yogurt produced with ropy starter was significantly more viscous (higher apparent viscosity) and less firm (lower complex viscosity) than yogurt produced with non-ropy starter for all treatments studied (P<0.01). These results demonstrate that source of WPC does affect the rheological and textural properties of yogurt. Subsequent work will attempt to relate these observed effects to differences in processing conditions during WPC manufacture.
Session 14A, Dairy Foods: General developments in dairy technology I
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