Effect of Psychrotrophic Growth on the Milk Fat Fraction at Different Temperatures of Storage

Authors

  • Thiago Braga Izidoro,

    1. School of Veterinary Medicine and Animal Science, Sao Paulo State Univ., Botucatu Campus, Caixa Postal 572, Sao Paulo, Brazil
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  • Juliano Gonçalves Pereira,

    Corresponding author
    • School of Veterinary Medicine and Animal Science, Sao Paulo State Univ., Botucatu Campus, Caixa Postal 572, Sao Paulo, Brazil
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  • Vanessa Mendonça Soares,

    1. School of Veterinary Medicine and Animal Science, Sao Paulo State Univ., Botucatu Campus, Caixa Postal 572, Sao Paulo, Brazil
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  • José Paes de Almeida NogueiraPinto

    1. School of Veterinary Medicine and Animal Science, Sao Paulo State Univ., Botucatu Campus, Caixa Postal 572, Sao Paulo, Brazil
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Direct inquiries to author Pereira (E-mail: julianopereira@veterinaria.com.br).

Abstract

The use of cooling, without using adequate hygienic practices in primary milk production, allows for the growth of psychrotrophic microorganisms that produce the thermoresistant lipases that give milk a rancid flavor. This study aimed to verify how the variation in temperature influences the lipolytic metabolism of the psychrotrophic organisms. Samples of raw milk were collected and submitted to laboratorial analysis as follows: psychrotrophic bacteria count, lipolytic bacteria count, and free fatty acids dosage. Each sample was divided into 3 aliquots and then incubated at 4, 8, and 12 °C, respectively. For each temperature, analyses were repeated after 12, 24, and 48 h of storage. Despite the psychrotrophs growth increase, according to temperature rise, the lipolytic metabolism was not consistent and presented the lower index at 8 °C, suggesting an intensification of the proteolytic compensatory activity at this temperature.

Practical Application

As the psychrotrophic microbiota is the most important in the process of lipolytic milk spoilage, the study and quantification of this metabolic activity is crucial for the development of control strategies, increasing the sensory quality and the milk shelf life.

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