摘要：The influence of fat on heat denaturation of milk casein has been investigated. The sample of heat denaturated casein were prepared by heating both skim milk and whole milk at 132℃ for 12 minutes. Gel permeation studies of skim milk heated casein (SMH Casein) and whole milk heated casein(WMH Casein) by Sephacryl S-200 Column Chromatography in 8M urea solution show that the particle size distribution of casein in the former is larger than that of the later. Sedimentation analysis by centrifugation with Swing roter at 6500rpm and 25℃ demotrate the rate of sedimentation for SMH casein micelle is higher than that of WMH casein micelle, as illustrated in their sedimentaion cotants of 621s and 567s respectively. Ultraviolet difference spectroscopy absorbance measurement reveals that, at early stage of dilution in mild alkaline solution, SMH casein has larger peaks at 298 nm and 303 nm than that of WMH casein suggesting that the former is rather unfolding in conformation. In contrast to WMH casein, the Infrared Spectra of SMH casein at 1530 cm-1 and 1650 cm-1 has the larger absorbance than the other frequency showing that peptidelike bond may be bearing. The fact that fat containing in milk would keep their casein micelle in stable during heat treatment and no fat binding to milk casein protein after the heat treatment is found. The result of experiments is concluded that fat may execute some functio on protein leading to more tolerence in heat denaturation such as conformational changes, more apt for the reversible change to native status in case of unfolding in structure, and prevent from aggregation among them.
