Psychrotrophic bacterial flora of raw ewes' milk, with particular reference to gram negative rods

Area of Science:

• Microbiology
• Food Science
• Dairy Science

Background:

• Raw ewes' milk is a valuable dairy product.
• Understanding its microbial flora is crucial for safety and quality.
• Psychrotrophic bacteria can impact milk shelf-life and characteristics.

Purpose of the Study:

• To characterize the microbial flora of raw ewes' milk.
• To assess the impact of refrigeration on microbial composition.
• To identify dominant psychrotrophic bacteria and their resistance patterns.

Main Methods:

• Analysis of 141 raw ewes' milk samples.
• Microbial enumeration before and after 72-hour storage at 4°C and 7°C.
• Isolation and identification of psychrotrophic bacteria, including antibiotic resistance profiling.

Main Results:

• Penicillin-resistant bacteria constituted approximately 61% of psychrotrophic isolates.
• Pseudomonas fluorescens and related strains dominated (86%) the Gram-negative psychrotrophic microflora.
• Leuconostoc dextranicum was the most prevalent Gram-positive psychrotrophic species.

Conclusions:

• Raw ewes' milk contains a substantial population of psychrotrophic bacteria.
• Refrigeration conditions favor the growth of specific resistant strains, notably Pseudomonas.
• The prevalence of penicillin-resistant bacteria highlights potential challenges in milk processing and safety.