Raw milk composition and sanitary quality after summer in semi-arid region

Abstract

The purpose of the present study was to evaluate physicochemical characteristics, milk coagulation properties and microbiological contents afterward the hot season to understand the impacts on raw milk quality. Fifty milk samples were collected in autumn season from the bulk tank of dairy collectors delivering milk to three major dairy industries in Setif, a semi-arid region in Algeria. Milk composition analysis showed that means of fat, solid-not-fat, protein, lactose, freezing point, total minerals, titrable acidity, density and heat stability rate were 2.66%, 8.54%, 3.18%,4.65%, –0.46°C, 0.67%, 1.89 g lactic acid/l, 1028.64 g/l and 92% respectively. Most milk samples were coagulated (78%). All physicochemical parameters were close or within the threshold values, only the point freezing was higher than the standard value. Mineral content was significantly different between dairy industries 1 and 3 (P<0.01), otherwise milk composition is similar in all dairy industries. Regarding microbiological content, means of total aerobic bacteria count, coagulase-positive Staphylococcus, fecal coliform and Salmonella presence were 3.87 CFU/ml, 1.36 CFU/ml, 2.74 CFU/ml and 0% respectively; however, a significant difference was observed in the microbiological contents between the dairy industries (P<0.05-0.01). In conclusion, physicochemical composition and sanitary quality of raw milk collected in autumn were acceptable. However, although clotting properties indicated that milk is suitable for cheese making, milk quality remains insufficient to reach requirement and demand of dairy processors of high milk quality. Further efforts are requested from the whole dairy chain to improve milk quality.