Abstract of paper presented at the 2002 Joint Annual Meeting of the American Dairy Science Association & the American Society of Animal Science

Bienvenue, Annie

Cho, Y. H.

Creamer, Lawrence K.

Havea, P.

Hong, Y. H.

Jiménez-Flores, Rafael

Manderson, G. A.

Singh, H.

English

DigitalCommons@CalPoly

199 Heat-induced reactions involving (3­lactoglobulin and other milk proteins in milk, whey, and model systems. L. K. Creamer*l, G. A. Manderson l , V-H. Hong2 , P. Havea l , V-H. Cho3 , H. Singh4 , A. Bienvenue5 , and R. Jimenez­Flores5 , 1 NZORI, Palmerston North, New Zealand, 2 Chonnam Uni­versity, Kwanju, Korea, 3 Mass. General Hospital, Boston, MA, USA, 4IFNHH, Massey University, Palmerston North, NZ, 50POc, Calpoly, San Luis Obispo, CA, USA. Heat treatment of milks is an essential step in modern dairy processing and the effects can be far-reaching in terms of product functionality and the heat-induced gelation of whey protein concentrate (WPC) solutions is important in functional food applications. Heating WPC solutions or milk beyond pasteurisation causes some of the individual whey proteins form aggregates and to aggregate with the other whey proteins. Studies using various kinds of two-dimensional polyacrylamide gel electrophore­sis (PAGE) analysis as the major tool with simple solutions of pure whey proteins confirmed that 13-lactoglobulin (I3-Lg) was the most important whey protein in these aggregations. A previously unknown group of in­termediates, the non-native ,B-Lg monomers, was of particular interest and some characteristics of these and other early heat-induced interme­diates were determined. The changes in the positions of the disulphide bonds in I3-Lg as a consequence of heat treatment were identified from mass spectroscopy-based analyses. @ Heated mixtures of a-lactalbumin (a-La) and I3-Lg were found to contain 1:1 disulfide-bonded dimers as well as non-native monomers, dimers, trimers, etc. of both a-La and I3-Lg The findings from this and other model systems were then tested in WPC solutions using one- and two-dimensional PAGE. @ In heat­treated milk the whey proteins interact to form disulfide bonds with the casein micelles and ,,-casein (,,-Cn) is the most significant casein in this reaction and I3-Lg was the most important whey protein in this reaction. In a model system, ,,-Cn and I3-Lg formed 1:1 aggregates as well as large polymeric aggregates. A heat-induced complex of I3-Lg and ,,-Cn was isolated from a heated mixture of casein micelles and 13­Lg by chromatography. Analysis of this complex identified a number of novel disulfide bonds between I3-Lg and ,,-Cn. @ These results have shown that I3-Lg is critical to the heat-induced changes in both milk and WPC, and have lead us to re-evaluate the likely mechanism for the initial changes within I3-Lg in response to heat-treatment. Key Words: I3-Lactoglobulin - ,,-casein complex, Non-native 13­lactoglobulin monomers, Heat-induced I3-Lg - a-La complex 50-51 J. Anim. Sci. Vo!. 80, Supp!. I/J. Dairy Sci. Vo!. 85, Supp!. 1 

Heat-Induced Reactions Involving β-Lactoglobulin and Other Milk Proteins in Milk, Whey, and Model Systems

https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1026&amp;context=dsci_fac

Heat-Induced Reactions Involving β-Lactoglobulin and Other Milk Proteins in Milk, Whey, and Model Systems

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