Control of Salmonella and Other Bacterial Pathogens in Low-Moisture Foods

Richard Podolak, Darryl G. Black, Richard Podolak, Darryl G. Black

• Publisher: Wiley-Blackwell
• Year: 2017
• Print ISBN:
  9781119071082
• eBook ISBN:
  9781119071075
• Edition: 1
• Topic: Tecnologia e ingegneria
• Subtopic: Scienze dell'alimentazione

The first and only comprehensive reference/solutions manual for managing food safety in low-moisture foods 

The first book devoted to an increasingly critical public health issue, Control of Salmonella and Other Bacterial Pathogens in Low-Moisture Foods reviews the current state of the science on the prevalence and persistence of bacterial pathogens in low-moisture foods and describes proven techniques for preventing food contamination for manufacturers who produce those foods.

Many pathogens, such as Salmonella, due to their enhanced thermal resistance in dry environments, can survive the drying process and may persist for prolonged periods in low-moisture foods, especially when stored in refrigerated environments. Bacterial contamination of low-moisture foods, such as peanut butter, present a vexing challenge to food safety, and especially now, in the wake of widely publicized food safety related events, food processors urgently need up-to-date, practical information on proven measures for containing the risk of contamination. While much has been written on the subject, until now it was scattered throughout the world literature in scientific and industry journals. The need for a comprehensive treatment of the subject has never been greater, and now this book satisfies that need.

• Discusses a wide variety of foods and evaluates multiple processing platforms from the standpoint of process validation of all food safety objectives for finished food products
• Takes a practical approach integrating the latest scientific and technological advances in a handy working resource
• Presents all known sources and risk factors for pathogenic bacteria of concern in the manufacturing environment for low-moisture/water activity products
• Characterizes the persistence and thermal resistance of bacterial pathogens in both the environment and most low-moisture food products

Control of Salmonella and Other Bacterial Pathogens in Low-Moisture Foods is a much-needed resource for food microbiologists and food industry scientists, as well as managers and executives in companies that produce and use low-moisture foods. It also belongs on the reference shelves of food safety regulatory agencies worldwide. 

Chapter 1
Introduction and Overview

Richard Podolak¹ and Darryl G. Black²

¹Grocery Manufacturers Association, Washington, DC, USA

²Food and Drug Administration, Bedford Park, IL, USA

1.1 Introduction

Low water activity (a_w) is a barrier to growth for many vegetative pathogens, including Salmonella spp. A product's water activity is used as a quantitative measure of the free moisture in foods available to microorganisms. Water in food that is not bound to food molecules can support the growth of bacteria, yeasts, and molds. The terms water activity and low moisture have been used interchangeably by food safety professionals even though they are quite different by definition. A variety of foods may have similar moisture content values but significantly different water activities. Of particular interest are the low-moisture foods, with water activity 0.85 and below. Processed products such as powdered milk, chocolate, peanut butter, infant foods, cereal, and bakery products are characteristically low water activity foods. While these products do not support the growth of Salmonella, all have been implicated in outbreaks of salmonellosis. Although some die-off occurs in low-moisture foods during storage, the degree of reduction depends on factors such as storage temperature and product formulation. Many other bacterial pathogens, such as toxin-producing Staphylococci, verotoxigenic E. coli (VTEC), Cronobacter sakazakii and aflatoxin-producing molds should also be considered in low-moisture foods. Due to its enhanced thermal residence in dry environments, Salmonella can survive for long periods in low-moisture food products. The heat resistance of Salmonella and other microorganisms of concern is affected by many factors, mostly by strain and serotypes tested, previous growth and storage conditions, the physical and chemical food composition, test media and the media used to recover heat damaged cells. The heat resistance of Salmonella generally increases with reducing moisture and this fact must be taken into account as a significant risk. Finally, from a quality standpoint, many spoilage organisms have been associated with low-moisture products; references will be provided in this book to aid the processor in finding the appropriate information concerning target organisms for specific low-moisture foods.

1.2 Definition of Low-Moisture Foods (LMF) and Water Activity Controlled Foods

Manipulation of the water content of foods is a classical method for food preservation and has been used by people for centuries. Salting, curing, drying, and the addition of sugars are examples of several traditional preservation methods that have been practiced over the ages. Of particular interest are the low-moisture foods and food ingredients that are naturally low in moisture or that have been subjected to a drying process and resulted in reducing the water content, for example, as in traditional sun-dried foods. Processed products such as milk-based powders, chocolate, peanut butter, powdered infant foods, seeds, herbs and spices, cereal and bakery products, and animal feeds are the examples of this type of food. Low-moisture foods have a reduced water activity (a_w), which is a growth barrier for many vegetative pathogens, including Salmonella spp.

Both moisture content and water activity are key parameters in predicting the stability of low-moisture food products. The terms water activity and low moisture have been used interchangeably in the processing industry and by food safety professionals even though they are quite different by definition. Moisture content represents a measure of the quantity of water in a product, providing information about yield and texture, but it does not provide reliable information about microbial safety. However, water activity, which was originally applied by the pharmaceutical and food industries, can be used as a quantitative measure to determine the shelf-life of product. Water activity can be defined as the ratio of the vapor pressure of water in a food matrix compared to that of pure water at the same temperature (Labuza, 1980). Therefore, a water activity of 0.80 means the vapor pressure is 80% of that of pure water. Water activity can be also defined as the equilibrium relative humidity (expressed as a percentage) above the food in a closed container dived by 100. For example, an equilibrium relative humidity of 70% would be an equivalent to a water activity of 0.7. The water activity scale extends from 0 (bone dry) to 1.0 (pure water) but most foods have a water activity level in the range of 0.2 for very dry foods to 0.99 for very moist fresh foods.

In the food system, total water is present i...

Table of contents

• Cover
• Title Page
• Copyright
• Table of Contents
• List of Contributors
• Chapter 1: Introduction and Overview
• Chapter 2: Regulatory Requirements for Low-Moisture Foods – The New Preventive Controls Landscape (FSMA)
• Chapter 3: Potential Sources and Risk Factors
• Chapter 4: Persistence of Salmonella and Other Bacterial Pathogens in Low-Moisture Foods
• Chapter 5: Best Industry Practices to Control Salmonella in Low-Moisture Foods
• Chapter 6: Heat Resistance of Salmonella and Other Bacterial Pathogens in Low-Moisture Foods
• Chapter 7: Validation Requirements in Heat-Processed Low-Moisture Foods
• Chapter 8: Test Methods for Salmonella in Low-Moisture Foods
• Chapter 9: Techniques to Determine Thermal Inactivation Kinetics for Pathogenic Bacteria and their Surrogate Organisms in Low-Moisture Foods
• Chapter 10: Modeling and Statistical Issues Related to Salmonella in Low Water Activity Foods
• Chapter 11: Spoilage Microorganisms in Low-Moisture Foods
• Index
• End User License Agreement