Rapid Detection of Psychrotrophic Bacteria In Manufacturing Grade Raw Milks

Area of Science:

• Food Microbiology
• Dairy Science
• Analytical Chemistry

Background:

• Assessing raw milk bacteriological quality is crucial for food safety and shelf-life prediction.
• Traditional methods like plate counts can be time-consuming, necessitating rapid assessment techniques.
• Psychrotrophic bacteria significantly impact milk quality during refrigerated storage.

Purpose of the Study:

• To investigate rapid methods for assessing raw milk's bacteriological quality.
• To evaluate the effectiveness of pre-incubation in enhancing bacterial count accuracy.
• To develop a predictive model for psychrotrophic bacterial growth in raw milk.

Main Methods:

• Comparison of direct microscopic count, modified psychrotrophic plate count, and direct epifluorescent filter technique (DEFT).
• Optimization of raw milk sample pre-incubation conditions (temperature and time).
• Application of the "square root" equation to model bacterial growth and develop a predictive equation.

Main Results:

• Initial methods showed poor correlation with initial psychrotrophic counts.
• Pre-incubation significantly improved the correlation between tested methods and bacterial counts.
• Optimal pre-incubation conditions included 30°C/6h, 21°C/10h, 13°C/15h, 13°C/20h, and 7°C/37h.
• A predictive model using DEFT after 21°C/10h pre-incubation accurately estimated initial and stored psychrotroph counts.

Conclusions:

• Pre-incubation is essential for accurate rapid assessment of raw milk bacteriological quality.
• The optimized DEFT method provides a reliable tool for predicting raw milk psychrotrophic bacterial load.
• This approach enhances the ability to manage milk quality throughout the supply chain.