| Summary: | 碩士 === 靜宜大學 === 食品營養學系 === 102 === Milk products have to be pasteurized or sterilized. In this study, milk proteins-lactose model systems were used to investigate the effects of heat treatments on the structure, immunoreactivity, and antioxidant capicity of proteins. The changes of protein composition and immunoreactivity on heated raw milk and commercial milk products were also investigated. Precipitation at pH 4.6, Native-PAGE, reducing and non-reducing SDS-PAGE, Western blot analysis, and ELISA were used to elucidate the changes and the interactions among milk proteins. In model systems, the antioxidant capacity was analyzed by ABTS radical scavenging ability, ferrous ion chelating ability and reducing power methods. The results of electrophoresis and Western blot showed that the interactions and degree of polymerization increased among β-Lg, α-La and casein as the heating temperature increased. The immunoreactivity of β-Lg and α-La increased, measured with ELISA using β-Lg and α-La antibodies, as the temperature increased, indicating the protein unfolding and exposure of more epitopes. At temperatures above 80 ℃, the antioxidant properties increased significantly. However, only reducing power followed the above trend for model systems containing casein. The changes of protein composition and immunoreactivity for heated raw milk were similar to those in model systems. Combining electrophoresis and immunoassay could differentiate different heat-treated commercial milk products.
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