The Effect of Freezing on Different Bacterial Counts in Raw Milk

Nizar Issa Alrabadi


This study had investigated the effect of freezing on the bacterial counts in raw milk. In specific, we estimated the total bacterial counts and the counts of total coliform, Salt tolerant bacteria, Staphylococcus spp., Thermopilic Lactobacilli, Mesophilic Lactobacilli, Leuconostoc spp., Lactococci and Streptococci. Thirty samples of raw cow milk were frozen at -18-20°C for eight weeks and tested on a weekly basis. The results showed that the bacterial counts had significantly decreased as the freezing period increased. Thus, the total count had significantly decreased from (6.5*105 cfu/ml) in fresh milk to (5.0*103 cfu/ml) in frozen milk after eight weeks (P1%). The decrease in the bacterial counts was different between the different bacterial groups. The highest decrease was for Salt tolerant bacteria from (9.8*105 cfu/ml) to (7.6*103 cfu/ml), while the lowest decrease was for Staphylococcus spp from (3.6*103cfu/ml) to (8.2*101cfu/ml). The study recommends freezing as an important storage method for raw milk.

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International Journal of Biology   ISSN 1916-9671(Print)   ISSN 1916-968X  (Online)   Email:

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