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Extended storage of cold raw milk on yogurt manufacturing
Fagnani, Rafael Schuck, Josiane Botaro, Bruno Garcia Santos, Fernando Cesar dos
Fagnani, Rafael
Schuck, Josiane
Botaro, Bruno Garcia
Santos, Fernando Cesar dos
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2017-02
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Fagnani, R., Schuck, J., Botaro Garcia, B., & Cesar dos Santos, F (2017). Extended storage of cold raw milk on yogurt manufacturing. Pesquisa Agropecuária Brasileira, 52(2), 104-112. https://dx.doi.org/10.1590/s0100-204x2017000200004
Abstract
The objective of this work was to evaluate the effect of the extended cold storage of raw milk
on the kinetics of fermentation on yogurt production, as well as on the product’s microbiological and
physicochemical properties during shelf life. Three treatments were evaluated: yogurts made with raw milk
stored for 4, 72, and 168 hours. Kinetics of fermentation was assessed through the lactic acid production rate,
growth rate of Streptococcus thermophilus and Lactobacillus bulgaricus, and time to reach pH 5.0 and 4.5.
The physicochemical and microbiological characteristics of raw milk and yogurts were also analyzed during
cold storage at 4°C. The microbial quality of raw milk was affected by the storage time of 168 hours, with a
decreasing tendency in the mesophiles:psychrotrophs ratio. Extended storage of raw milk beyond 72 hours
negatively affects yogurt production, despite the low initial bacterial count, decreasing lactic acid production,
S. thermophilus growth rate, pH, and protein content. Therefore, to optimize fermentation and yogurt shelf
life, the maximum storage time for raw milk at 4o
C should not exceed 72 hours.