Effects of Cow's Milk Processing on MicroRNA Levels

Area of Science:

• Biochemistry
• Molecular Biology
• Food Science

Background:

• MicroRNAs (miRNAs) are key gene regulators resistant to harsh conditions, making them potential biomarkers.
• Variations in milk miRNA levels are linked to dairy production systems, diet, and management.
• The impact of food processing on miRNA stability and their utility as biomarkers in dairy products is not well understood.

Purpose of the Study:

• To investigate the effect of common dairy processing techniques (microwaving, yogurt fermentation, cheesemaking) on the levels of specific microRNAs in cow's milk.
• To determine if microRNA concentrations in raw milk can be extrapolated to derived dairy products.
• To assess the potential of microRNAs as stable biomarkers across different dairy product types.

Main Methods:

• Sampling of raw milk from 10 dairy farms in Asturias, Spain.
• Processing of milk samples via microwave heating, yogurt production, and cheese production.
• Isolation of total RNA from raw milk and processed products.
• Quantification of seven selected microRNAs using reverse transcription quantitative polymerase chain reaction (RT-qPCR).

Main Results:

• All tested processing methods (microwaving, fermentation, cheesemaking) led to a decrease in the levels of the studied microRNAs.
• Cheesemaking appeared to increase the concentration of microRNAs in the final product compared to yogurt and microwaved milk.
• Raw milk and cheese exhibited potentially similar, higher concentrations of microRNAs than yogurt and microwaved milk.
• The concentration of specific microRNAs in raw milk does not directly correlate with their concentration in processed dairy products.

Conclusions:

• Technological and culinary treatments significantly alter microRNA levels in milk-derived products.
• MicroRNA concentrations vary considerably between raw milk, yogurt, cheese, and microwaved milk.
• The findings suggest that while microRNAs show promise as biomarkers, their stability across different dairy products requires careful consideration, and direct extrapolation from raw milk is not advisable.