PRESERVATION OF RAW COW MILK USING NON THERMAL TREATMENTS

Abstract

This study was undertaken to evaluate the feasibility of using non thermal treatments for the preservation of raw cow milk. Samples of cow milk were incubated at 4oC as a control (C), heat treated at 80 oC for 10min (HT), activated LP-system (LPs), added soluble chitosan (CH, 0.1%), β-glucan (BG, 30mg/L) or glucomannan (GM, 30mg/L). All treated samples were incubated at 25oC, 37oC or 45oC. Ttitratable acidity (T.A%), milk stability, rennet coagulation time, starter activity, total aerobic mesophilic bacterial count (TBC), spore forming bacterial count (SC), coliform (CC) and mould & yeast (M.Y) in all samples were determined during incubation. A significant slowing down in the rate of increase in T.A% was found in all samples. Shelf-life of raw milk was of 19, 13, 12, 11, and 10 hr, during incubation at 25 oC for samples treated with HT, CH, LP, BG, and GM, respectively, with the same acidity (0.195%) in all samples. The clot on boiling and alchol stability tests of all samples are o0f the same trend of titratable acidity. The starter activity decreased significantly by adding CH, BG, GM and LPs. However HT as well as control treatments had a significant higher starter activity than other treatments. On the other side, all treatments reduced significantly rennet coagulation time, except LPs and HT treatments, which delayed coagulation time. Results showed no significant differences between all samples for TBC at the different incubation temperatures. Spore count in HT and CH treatments was significantly less than other treatments. Moreover, HT treatments had the lowest count for coliform, and M&Y. Coliform count was significantly lower by adding BG than other treatments.