Microbial Toxins in Dairy Products

Adnan Y. Tamime

• Publisher: Wiley-Blackwell
• Year: 2016
• Print ISBN: 9781118756430
• eBook ISBN: 9781118823149
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

Food-borne diseases, including those via dairy products, have been recognised as major threats to human health. The causes associated with dairy food-borne disease are the use of raw milk in the manufacture of dairy products, faulty processing conditions during the heat treatment of milk, post-processing contamination, failure in due diligence and an unhygienic water supply. Dairy food-borne diseases affecting human health are associated with certain strains of bacteria belonging to the genera of Clostridium, Bacillus, Escherichia, Staphylococcus and Listeria, which are capable of producing toxins, plus moulds that can produce mycotoxins such as aflatoxins, sterigmatocytin and ochratoxin.

Microbial Toxins in Dairy Products reviews the latest scientific knowledge and developments for detecting and studying the presence of these toxins in dairy products, updating the analytical techniques required to examine bacterial and mould toxins and the potential for contamination of milk as it passes along the food chain, i.e. from 'farm-to-fork'.

This comprehensive and accessible collection of techniques will help dairy processors, food scientists, technologists, researchers and students to further minimise the incidences of dairy food-borne illnesses in humans.

1
Microbial Toxins – An Overview

R. Early and A.Y. Tamime

1.1 Introduction

Microbial toxins can be and often are troublesome to human health and well‐being. History records numerous occurrences of death and suffering caused by disease organisms, such as Yersinia pestis, of bubonic plague or Black Death fame, Corynebacterium diptheriae and Vibrio cholerae, the causative organism of diptheria and cholera respectively, as their names suggest, Bordetella pertussis, which causes whooping cough, and Salmonella enterica subsp. enterica serotype Typhi, which causes typhoid. Although these bacterial pathogens exhibit very different aetiologies in terms of vectors and modes of infection, they are all similar in that they cause disease by means of toxins. The word ‘toxin’ is derived from the ancient Greek language, and refers to poison produced by living cells or organisms; although today it has a wider application, and can apply to synthetic compounds.

Modern medicine, linked with improvements in sanitation and other public health measures, has reduced the incidence of many bacterially mediated diseases, particularly in technologically developed societies. Since the nineteenth century, our scientific understanding of the mechanisms by which these organisms proliferated and caused disease has increased greatly. Our ability to treat the diseases by means of vaccines and antibiotics has meant that for many people today, the spectre of the once common illnesses and death that the organisms represented no longer hovers close to society. This is not to say, however, that illness and disease caused by micro‐organisms and their toxins are no longer problematic. While diseases, such as diptheria, cholera and typhoid are relatively uncommon today, modern consumers all too often encounter the actions and consequences of microbial toxins, particularly bacterial toxins. When they consume food products that have been contaminated and/or mismanaged, often during production, a consequence can be affliction with food‐borne disease, commonly referred to as food poisoning.

All food businesses engaged in the production, processing, manufacture, distribution and sale of food products to consumers have to be concerned about food safety and the problem of food‐borne disease. The dairy industry is no exception. Although dairy products are amongst the safest of food products, because of the exceptionally high standards of general management, and specifically hygiene and food safety management, employed throughout the dairy chain, from farm to supermarket, the potential exists for dairy products to be involved in the occurrence of food‐borne disease. The food safety management strategies of dairy farmers, milk processors and milk products manufacturers are designed and implemented precisely to safeguard consumers. An important part of the strategies concerns understanding the nature of the food‐borne disease organisms that may be associated with dairy products, and how to minimise the risk of their occurrence in products.

The purpose of this chapter is to review the issue of toxins associated with dairy products and specifically those of microbial origin, thereby setting the scene for the rest of the book.

1.2 Microbial toxins: modes of action

Toxigenesis is the ability to produce toxins and the sources of microbial toxins that may be associated with dairy products are two‐fold: (a) those produced by bacteria, and (b) those produced by fungi (or moulds). Bacterial toxigenesis is very significantly of greater concern to the dairy industry and consumers of milk products than are toxins produced by fungi, although the latter are not unimportant.

Bacterial toxins are commonly designated as endotoxins and exotoxins. Most gram‐negative bacteria and all Enterobacteriacea produce endotoxins (Lüderitz et al., 1966). These toxins are commonly components of bacterial cell walls in the form of lipopolysaccharides, and are compounds composed of three units: (a) the lipid A component, which is hydrophobic in nature, (b) the core oligosaccharide (consisting of an inner and outer core), the structure of which varies diversely according to bacterial species and subspecies, and (c) the O polysaccharide, or O antigen as it is also known. The somatic antigen is located in the cell wall of both gram‐positive and gram‐negative bacteria. However, the somatic O antigen is exhibited by many organisms, including salmonellas and the well‐known Escherichia coli O157:H7, of which the letter O is at times erroneously reproduced as the numeral zero. Like the core oligosaccharide, the structure of the ...

Table of contents

• Cover
• Title Page
• Table of Contents
• List of Contributors
• Preface to the Technical Series
• Preface
• 1 Microbial Toxins – An Overview
• 2 Incidences of Mould and Bacterial Toxins in Dairy Products
• 3 Bacterial Toxins – Structure, Properties and Mode of Action
• 4 Biogenic Amines in Dairy Products
• 5 Contamination of Raw Milk
• 6 Milk Product Contamination After the Farm Gate
• 7 Techniques for Detection, Quantification and Control of Bacterial Toxins
• 8 Techniques for Detection, Quantification and Control of Mycotoxins in Dairy Products
• 9 Approaches to Assess the Risks/Modelling of Microbial Growth and Toxin Production
• 10 Regulatory Measures for Microbial Toxins
• Index
• End User License Agreement