Psychotrophic Bacteria In Milk

Psychrotrophs and Milk Quality

Introduction

Psychrotrophic bacteria are bacteria that are capable of surviving in a cold environment which are not usually ideal bacterial conditions. They also provide an estimation of shelf life and are largely responsible for the spoilage of refrigerated foods. The most common psychrotrophic bacteria are in the genus Pseudomonas. The psychotrophic bacteria isolated from milk are Gram-positive or Gram-negative. Bacteria and other microorganisms may enter milk from an udder infection in a cow, from the environment around us, or from unsanitary conditions in the milking process. Milk provides a perfect medium for microorganisms to grow in due to its almost neutral pH. These microorganisms are meant to be destroyed by the process of pasteurization, but may psychrotrophic bacteria may still occur in milk from contamination after pasteurization. The majority of psychrotrophic bacteria have the ability to form hydrolytic thermostable enzymes, which allow them to survive, and in turn, break down the main constituents of milk which are fats, protein and lecithins. With these broken down, the quality of milk is degraded.

Psychrotrophic Bacteria

and Pseudomonas fluorescens are part of a heterogenous group of microorganisms from the Pseudomonadacae group containing pervasive amounts of Gram-negative, Gram-positive, aerobic, non fermentative, catalase and oxidase positive, mesophilic and psychrotolerant, non-spore forming rods (Janda and Abbott, 2007). Pseudomonas micro-organisms are able to adapt to different environments due to their complex enzyme systems. This is the primary reason why psychrotrophic bacteria are associated with the spoilage of milk products (L.Caldera, L. Franzetti et. al. 2015). Gram-positive and gram-negative bacterial micro organisms can be detected in milk by farmers themselves at the milking process or microbiologists assessing milk quality by using simplified culture systems (Silva et, al.