Changes in bacterial populations in refrigerated raw milk collected from a semi-arid area of Algeria
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Date
2015-10-14
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Springer
Abstract
Abstract Most of the studies on milk microbiota have
been performed on cows’ milk from animals reared in temperate
and humid areas. In this work, changes in the bacterial
consortium of refrigerated raw milk collected from
cows grazed in a semi-arid area of Algeria were studied
during 21 days of refrigerated storage. Twenty bacterial
morpho-physiotypes were selected among 150 isolates from
milk at different times over storage and identified by partial
16S rRNA gene sequencing. The dominant bacterial populations
were characterized by a few species. Stenotrophomonas
rhizophila, S. maltophilia and Chryseobacterium indologenes
were predominant during the first 7 days, Lactobacillus
pentosus and L. plantarum were isolated only after the 10th
day, while Acinetobacter spp. was isolated at the end of storage.
Compared to the current literature on milk from temperate
zones, sluggish and incomplete microbial growth was observed
with a long incubation phase ranging from 6.7 to
10.5 days and a maximum growth not exceeding 5.3 log
colony-forming units (CFU)·mL−1. The composition of milk
microbiota and its evolution over refrigeration suggest a biogeographical
characterization due to environmental factors. In
particular, the possible presence of antimicrobial molecules
coming from plants grazed in the semi-arid zone around the
farm may account for the presence of selected microbial species
and the extended milk shelf-life. Despite this being a
preliminary work, these results encourage the use of arid herbs
in animal feed and motivate scientists to focus their efforts on
the study of biochemical composition of plants from arid areas
and their antimicrobial activity