The Importance of Endospore-Forming Bacteria Originating from Soil for Contamination of Industrial Food Processing

Marc Heyndrickx

doi:10.1155/2011/561975

Abstract

Specific endospore formers have become important contaminants in industrial food processing. The direct or indirect soil route of contamination or dispersal is the start of events or processes in the agrofood chain that eventually leads to important problems or concerns for food safety and/or quality. Three important food sectors are discussed in this paper. In the dairy sector,Bacillus cereus, the most important pathogen or spoilage organism in this sector, andClostridium tyrobutyricum, the most important spoiler in certain cheeses, both contaminate pasteurized milk through the faecal and/or (at least forB. cereus) the direct soil route. In the fruit juice industry,Alicyclobacillus acidoterrestris, present on raw fruits, has become a major quality-target organism. In the ready-to-eat food sector,B. cereusand other aerobic endospore formers are introduced via vegetables, fruits, or herbs and spices, while anaerobic spore formers like nonproteolyticClostridium botulinumandClostridium estertheticumpose safety and spoilage risks in chilled packaged foods, respectively.

Highlights

There is a clear association between soil-borne endospore forming bacteria and food contamination
In the readyto-eat food sector, B. cereus and other aerobic endospore formers are introduced via vegetables, fruits, or herbs and spices, while anaerobic spore formers like nonproteolytic Clostridium botulinum and Clostridium estertheticum pose safety and spoilage risks in chilled packaged foods, respectively
Some of them seem even to be of more recent concern, which might be the result of increasing tolerance, adaptation, or resistance of spores or vegetative cells of particular spore-forming species to conditions or treatments that were previously presumed either to stop growth or to inactivate all living material (ultrahigh heat treatment (UHT) and commercial sterilization)

Summary

Introduction

There is a clear association between soil-borne endospore forming bacteria and food contamination. Several reasons can be proposed to explain this phenomenon, and most are related to some general characteristics of the spores, which are formed at the end of the growth phase within the vegetative mother cell acting as sporangium (endospores) and released in the environment as survival structures (Figure 1). These are (1) their ubiquitous presence in soil, (2) their resistance to heat in common industrial processes such as pasteurization, (3) the adhesive characters of particular spores that facilitate their attachment to processing equipment, and (4) their ability to germinate and grow in favorable conditions [1]. Recent data revealing the role of soil as primary contamination source for spore formers in food (B. cereus, Alicyclobacillus acidoterrestris, Clostridium tyrobutyricum) or extending our knowledge on specific soil-borne spore formers in food (several Clostridium spp. such as C. estertheticum) are discussed

Bacillus cereus

Alicyclobacillus acidoterrestris

Clostridia

Findings

Conclusions