Spoilage bacteria pseudomonas - production of hydrolytic enzymes and ability to grow at 5°C

Abstract

Microbial growth and metabolism in food leads to organoleptic spoilage through altering colour, odour and texture of food, and slime or liquid production on the surface. In the dynamics of organoleptic spoilage, initial microbial contamination and storage temperature of food play an important role. Bacteria Pseudomonas are known as the most common spoilage bacteria. Aim of this study was to evaluate the ability of selected Pseudomonas strains to grow at 5°C in different food models, and to evaluate their spoilage potential as the ability to produce different hydrolytic enzymes at 5°C. This was determined through monitoring the number of bacterial cells in food models at 5°C, over 9 days of incubation, and on agars for detection of proteolytic and lipolytic activity. Of the four selected Pseudomonas strains (P. fragi CC151, P. fragi CC275, P. psychrophila CC291, P. lactis CC194), all were capable of producing lipolytic and proteolytic enzymes. When monitoring Pseudomonas growth in different food models (minced meat, pasteurized milk, apples) as compared to broth, the best growth was achieved in minced meat model, and the lowest in apple model. Thereby, the importance of the nutrients availability and the use of hydrolytic enzymes to exploit more complex nutrient molecules, especially proteins, has been confirmed. Selected Pseudomonas strains are able to grow in a variety of food media, and have the ability to produce hydrolytic enzymes, confirming their universality as refrigerated food spoilers, with high potential of persisting in the food storage environment.

Keywords

• food spoilage
• pseudomonas
• psychrotrophic
• lipolysis
• proteolysis