Influence Of Common Processing Treatments On Oxidative Stability Of Rich-fat-milk

Froment du Léon is the special race of milk breeds in the Bretagne region inFrance. Its milk fat content is much higer,46g/kg in average. Because of its feature,it’s very easy to be oxidized, particularly in summer (from May to August) the speedof oxidation is more quick.In the experiments of content of fat and protein in different month, although thecontent was not the same, there was no big difference. So we could say the milk webrought in different time could be seen as the same. The fat content is4.47±0.07g/100g in average, the protein content is3.39±0.04g/100g in average.In the experiment of determination of TBA method, reaction temperature,reaction time, pH and centrifugation time were compared to see how they affect theconcentration of MDA. The optimum situation of reaction is100℃/30min, pH<3,3000r/min centrifuge15min. This TBA method is shortened reaction time andimproved the efficiency.In the experiments of researching on the lipid oxidation under differentthechnological treatments,4common technological treatments in dairy industry werechosen: heat treatment, acid treatment, homogeneization and concentration(ultrafiltration). The niveaux of each factors were: heat treatment: raw milk,heat-treated milk (60°C/20s）, pasteurized milk (90°C/20s), UHT (125°C/20); acidtreatment：pH6.8and pH4.6; Ultrafiltration：FRV1,2,3and4；homogeneization:non homogeneization and homogeneize at7MPa.We used peroxide value method andTBA method to evalue the lipid oxidation. The optimum technological parameterswere:90°C/20s, homogeneized, pH4.6in condition of storaging at4°C for13days.The results of this study optimized the TBA method and provided a certainamount of theoretical and methodological basis for the liquid rich-fat-milk products.But the oxidation‘s mechanism in view of molecular and orther affecting factors needalso to be studied continuly in future.