Right combination of temperatures lessens whey separation in yogurt.Whey whey liquid residue from milk after the removal of cheese curds in the manufacture of cheese. An excellent protein supplement but difficult to handle in the liquid form, except to pigs maintained close to the cheese factory. Dried whey is easy to handle but processing costs are high. separation is a significant defect that occurs in yogurt. It can lead to an extensive rearrangement of the gel network. We need a better understanding of the rheological and physical properties of yogurt gels in order to control whey separation. The goal of scientists at the University of Wisconsin was to understand how process variables, such as heat treatment and incubation temperature, influence the rheological, physical properties and microstructure mi·cro·struc·ture n. The structure of an organism or object as revealed through microscopic examination. microstructure Noun a structure on a microscopic scale, such as that of a metal or a cell of yogurt gels. They found that high-heat milk treatment and low incubation temperatures are less likely to lead to a rearrangement of the network. Instead, this combination would likely lead to less whey separation of the gels. The investigators heated skim milk skim milk n. The milk from which the cream has been removed. skim milk the residue from whole milk after the cream has been skimmed off. In today's usage it is the residue after the butterfat is removed. at 72 C, 75 C, 82.5 C, 90 C and 93 C for 30 minutes. The milks were incubated with a commercial starter culture at 34.3 C, 36 C, 40 C, 44 C, or 45.7 C until the pH of the milk reached pH 4.6. A central composite experimental design and response surface methodology Response surface methodology (RSM) explores the relationships between several explanatory variables and one or more response variables. The method was introduced by G. E. P. Box and K. B. Wilson in 1951. were used for data analysis. The scientists determined the rheological properties by using dynamic low-amplitude oscillation and then measuring storage modulus and loss tangent. The amount of spontaneous whey separation was quantified using a volumetric flask A volumetric flask (vol flask for short) is a type of laboratory flask (piece of laboratory glassware) used to contain or measure a very precise and accurate amount of a liquid. It is shaped like a Florence flask with a flatter bottom so as to not tip over. test. Confocal confocal see confocal microscopy. scanning laser microscopy enabled the researchers to observe the microstructures of the yogurt gels. Second-order polynomial polynomial, mathematical expression which is a finite sum, each term being a constant times a product of one or more variables raised to powers. With only one variable the general form of a polynomial is a0xn+a models predicted the effects of heating and incubation temperature on the rheological properties, permeability and the whey separation of yogurt gels. The scientists found that the storage moduli of the yogurt gels increased when there was an increase in heating temperature and a decrease in incubation temperature. The maximum loss tangent, permeability and whey separation of yogurt gels increased with a decrease in heating temperature and an increase in incubation temperature. The results indicate there is an increased potential for rearrangements of the gel network to occur. This was indicated by the presence of large pores in the microstructures of the gels. Whey separation of yogurt gels was negatively correlated with storage modulus, and was positively correlated with the maximum loss tangent and permeability. Further information. John Lucey, Department of Food Science, University of Wisconsin-Madison “University of Wisconsin” redirects here. For other uses, see University of Wisconsin (disambiguation). A public, land-grant institution, UW-Madison offers a wide spectrum of liberal arts studies, professional programs, and student activities. , 1605 Linden Dr., 10 Babcock Hall, Madison, WI 53706; phone: 608-265-1195; fax: 608-262-6872; email: jalucey@facstaff.wisc.edu. |
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