Control of yeast contaminations in food industry. Literature study

Yeast are usually known for their beneficial role in the production of fermented foods. However, yeast can also act as food spoilage agents. Abundant growth of unwanted yeasts during various stages of production can lead to production problems and quality defects in the final product. Hence, the production of microbiologically wholesome food is usually best achieved by controlling microbial contaminations throughout the whole production chain. This literature review is an extensive information package about foodborne yeasts and their control and identification methods. First, general properties and the classification system of yeasts are summarised alongside with the occurrence and effects of yeast in various types of food. The review focuses on the presentation of different factors controlling the contamination and growth of yeasts in food. Good production hygiene has a key role in the prevention of contaminations. The few published articles about the biofilms formed by foodborne yeasts and about the effects of different cleaning and disinfecting agents on yeasts are summarised, and the latest information about the effects of different physical, chemical and biological factors on yeasts is presented. Traditional and state-of-the-art food preservation methods and their effectiveness against yeast are summarised. Traditional methods, such as chemical preservatives, are often ineffective against food spoilage strains and there is a tendency to avoid their use. Recently, promising results have been obtained with the combined use of different minimal processing methods. However, much research work is still needed in this field. The solving of contamination problems and the selection of appropriate intervention measures often necessitates rapid tracing and identification of the contaminating organisms. In this publication, phenotypic and genotypic methods for the identification, typing and detection of foodborne yeasts are reviewed in detail and their practicality in routine food control is discussed. Copyright © Valtion teknillinen tutkimuskeskus (VTT) 2001.