There were differences (P <0.05) in viscosity, consistency coefficient and flow behaviour index among ice cream mixes (Table 3). Sharp increases were obtained in viscosity of ice cream mixes containing WPI in comparison to regular control sample (P <0.05). This represents that the addition of 4% WPI resulted in an excess thickening and gelation in ice cream mix. The composition of whey protein fractions that change depending on the processing methods are reported to influence the functionality of WPI. The WPI prepared by ion exchange technique that was used in our study, normally contains the full complement of β-lactoglobulin, but much of the α-lactalbumin and some of the immunoglobulins and other protein components are lost. The principal functionality of β-lactoglobulin is gelation and thickening.The β-lactoglobulin fraction is particularly important in forming large protein networks after heating [ 22]. In the study of Britten [ 23 ], WPI was dispersed in water (8%), pH was adjusted and ionic calcium was added. The dispersion was heated at 95 ° C for 15 min and then cooled to room temperature. Electron micrographs showed that the increse viscosity of protein dispersions after heating reflects the formation of linear polymers. Calcium is beleved to promote protein association and increase polymer length Extremely high viscosity in ice cream mixes containing WPI can be sourced from these polymers or large protein networks and also from higher molecular weight of WPI in comparison to inulin.
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