Changes in the microflora composition of goat and sheep milk during lactation

Abstract

The aim of this work was to determine extend of microbial contamination of raw milk in individual seasons. Raw goat milk (3 farms) and sheep milk (2 farms) were analyzed. Milk was produced on farms of different way of farming and with a different number of milked animals. Samples were taken during lactation three terms in the beginning, middle and end of lactation. In milk, following groups of microorganisms were determined by standard methods: total count of microorganisms (TCM), psychrotrophic microorganisms, Enterobacteriaceae, lactic acid bacteria (lactobacilli), enterococci, aerobic and anaerobic thermoresistant microorganisms (TMRae, TMRan), micromycetes (yeast and moulds). In goat milk, the following numbers of microorganisms were detected: total count of microorganisms (TCM) from 105 to 109 CFU x mL-1, lactobacilli from 102 to 105 CFU x mL-1, bacteria fam. Enterobacteriaceae from 101 to 105 CFU x mL-1, enterococci from 101 to 105 CFU x mL-1, thermoresistant aerobic and anaerobic microorganisms (TMRae and TMRan) from units to 103 resp. 105 CFU x mL-1, psychrotrophic microorganisms from 101 to 106 CFU x mL-1, micromycets from 101 to 104 CFU x mL-1. In the sheep milk, the following numbers of microorganisms were determined: TCM from 105 to 106 CFU x mL-1, lactobacilli from 103 to 106 CFU x mL-1, bacteria fam. Enterobacteriaceae from 101 to 105 CFU x mL-1, enterococci from 101 to 104 CFU x mL-1, TMRae and TMRan from units to 105 CFU x mL-1, psychrotrophic microorganisms from 104 to 106 CFU x mL-1, micromycets from 102 to 104 CFU x mL-1. From the above mentioned results, the following conclusions can be suggested. The bacterial counts of raw goat and sheep milk are highly variable and influenced by a number of important factors in the course of lactation and year (temperature, health, secondary contamination etc.). The bacterial numbers are not affected by the stage of lactation. High numbers of microorganisms in goat and sheep milk may be primarily caused by the insufficient cleaning and sanitizing of milking equipment or low hygiene of hand milking. An important role may also act the cooling rate of milk and purity of cooling eguipment.