Growth and location of bacterial colonies within dairy foods using microscopy techniques: a review.

Cian D Hickey,Jeremiah J Sheehan,Martin G Wilkinson,Mark A E Auty

doi:10.3389/fmicb.2015.00099

Abstract

The growth, location, and distribution of bacterial colonies in dairy products are important factors for the ripening and flavor development of cheeses, yogurts, and soured creams. Starter, non-starter, spoilage, and pathogenic bacteria all become entrapped in the developing casein matrix of dairy foods. In order to visualize these bacterial colonies and the environments surrounding them, microscopy techniques are used. The use of various microscopy methods allow for the rapid detection, enumeration, and distribution of starter, non-starter and pathogenic bacteria in dairy foods. Confocal laser scanning microscopy is extensively utilized to identify bacteria location via the use of fluorescent dyes. Further study is needed in relation to the development of micro- gradients and localized ripening parameters in dairy products due to the location of bacteria at the protein–fat interface. Development in the area of bacterial discrimination using microscopy techniques and fluorescent dyes/tags is needed as the benefits of rapidly identifying spoilage/pathogenic bacteria early in product manufacture would be of huge benefit in relation to both safety and financial concerns.

Highlights

BACTERIA WITHIN DAIRY PRODUCTS Bacteria are naturally present and are used extensively across all areas of dairy and food fermentation, either as natural microflora, or as starter cultures added under controlled conditions (Yang et al, 2012)
This review focuses on microscopy methods allowing for the visualization of bacterial colony location and distribution
The use of microscopy has made the visualization of bacteria in food matrices possible and allows for the enumeration, location, and distribution of starter lactic acid bacteria (LAB), Non-starter lactic acid bacteria (NSLAB), spoilage, and pathogenic bacteria via non-destructive methods

Summary

Introduction

BACTERIA WITHIN DAIRY PRODUCTS Bacteria are naturally present and are used extensively across all areas of dairy and food fermentation, either as natural microflora, or as starter cultures added under controlled conditions (Yang et al, 2012). Fermented dairy products are often not manufactured under sterile conditions or with sterile milk (unpasteurized) and this can allow non-starter LAB as well as spoilage or pathogenic bacteria access to the fermenting food system (Montville and Matthews, 2005). The use of starter bacteria is needed in order to acidify the cheese milk before and during dairy food production.

Results

Conclusion