Food Preservation and Biodeterioration

Gary S. Tucker

Food Preservation and ­Biodeterioration

Food Preservation and Biodeterioration

Biodeterioration is the breakdown of food by agents of microbiological origin, either directly or indirectly from products of their metabolism. Preservation on the other hand is the process by which food materials are maintained in their original condition or as close to this as possible.

This second edition of Food Preservation and Biodeterioration is fully updated and reorganised throughout. It discusses how the agents of food biodeterioration operate and how the commercial methods available to counteract these agents are applied to produce safe and wholesome foods. With this book, readers will discover traditional methods and major advances in preservation technology. Both microbiological and chemical pathways are analysed.

This topic being important to all producers of food, the readership spans food scientists across the industry and academia, particularly those involved with safety and quality.

1
Control of Biodeteriorationin Food

1.1 OVERVIEW

All food undergoes deterioration to some degree once harvested or slaughtered. The deterioration may include loss of nutritional value, organoleptic and colour changes, and most importantly, safety may become compromised. It is the challenge of the food industry to control this deterioration and maintain the safety of the food, while making sure that the food is as convenient, nutritious and available as it can possibly be.

Biodeterioration is defined as any undesirable change in the property of a material caused by the vital activities of organisms [1]. It is applicable to many materials for example food, wood, paper, leather, fuels, cosmetics, building materials and building structures. Biodeterioration may be a result of the metabolic processes of one of many microorganisms, or it can be caused by insect, rodent or bird damage. As an incredibly broad and diverse field, all biodeterioration has as a common theme in that it affects materials and substances that we need and value, and that it can largely be controlled by proper understanding of the materials and the possible spoilage organisms and their mechanisms of decay.

Biodeterioration is also specifically different from biodegradation in that the changes are ‘undesirable’. Biodegradation occurs when complex materials are broken down by microorganisms to form simple end-products. Within a biological ecosystem, there are microorganisms that produce a host of enzymes that can biodegrade natural as well as some synthetic products; this is very important for maintaining the stability of the ecosystem and is extremely important for water purification and sewage treatment. It is also widely used in the food industry. The main differences between biodeterioration and biodegradation are the undesirability and uncontrollability of the former [2].

Another important feature of biodeterioration is that it is caused by organisms. According to the definition, it is not the degradation that occurs naturally in some organic materials or foods caused by intrinsic enzymes. These enzymes are present in the product and cause degradation or decay after death. Loss of food quality by intrinsic enzymes is an important topic as it can cause quality deterioration and render food unacceptable. Reactions due to these enzymes will not be considered in detail in this text, but are important to bear in mind as their activities can make nutrients from the product available and accessible to microorganisms so that biodeterioration reactions can follow [2, 3].

1.2 A SUMMARY OF THE DIFFERENT KINDS OF BIODETERIORATION

1.2.1 Chemical biodeterioration

There are two modes of chemical biodeterioration. Both have a similar result, that is the material becomes spoilt, damaged or unsafe (see Table 1.1 and Fig. 1.1), but the cause or biochemistry of the two is quite different [2, 4]:

• Biochemical assimilatory biodeterioration – the organism uses the material as food or an energy source. Growth of mould on bread is an example of this type of biodeterioration.
• Biochemical dissimilatory biodeterioration – the chemical change in the food is as a result of waste products from the organisms in question. Examples of this are pH changes in food that arise from acids generated from the metabolic action of microorganisms such as bacteria, yeast and mould.

Table 1.1 Examples of the diversity of biodeterioration.

Affected material	Example	Type of biodeterioration
Stone, marble, concrete	Deterioration of stone monuments	Chemical assimilatory: where calcium and other minerals are used as a food source Chemical dissimilatory: where acid by-products dissolve the surfaces Mechanical: where root damage can undermine and weaken structures Fouling: where biofilms can affect the aesthetics of the structure
Wood	Rotting of wooden floorboards and timber structures	Chemical assimilatory: where the cellulose and lignin in the wood are used as food by fungi and other organisms Dissimilatory: where acid and other by-products result in breakdown of the structure
Leather	Loss of strength and structure of leather objects	Chemical assimilatory: by proteolytic bacteria, which break down the proteins
Paper	Degradation of books	Chemical assimilatory: most commonly by fungi
Paint	Water-based paints	Chemical assimilatory: by bacteria and fungi, results in thinning of the paint and production of off odours
Museum artefacts	Discoloration and degradation of valuable relics	Chemical assimilatory and chemical dissimilatory: by bacteria and mould, resulting in weakening of structures and discol...

Table of contents

• Cover
• Title Page
• Table of Contents
• Preface
• 1 Control of Biodeteriorationin Food
• 2 Principles of HACCP: The Importance of HACCP Systems in Food Manufacturing
• 3 Thermal Processing
• 4 Chilling
• 5 Freezing
• 6 Drying
• 7 Modified Atmosphere Packaging
• 8 Preservatives
• 9 Hurdle Techniques
• 10 Novel Commercial Preservation Methods
• Index
• End User License Agreement