Food and Beverage Stability and Shelf Life

David Kilcast, Persis Subramaniam

• Publisher: Woodhead Publishing
• Year: 2011
• eBook ISBN: 9780857092540
• Topic: Technology & Engineering
• Subtopic: Food Industry
• Index: Technology & Engineering

Ensuring that foods and beverages remain stable during the required shelf life is critical to their success in the market place, yet companies experience difficulties in this area. Food and beverage stability and shelf life provides a comprehensive guide to factors influencing stability, methods of stability and shelf life assessment and the stability and shelf life of major products.Part one describes important food and beverage quality deterioration processes, including microbiological spoilage and physical instability. Chapters in this section also investigate the effects of ingredients, processing and packaging on stability, among other factors. Part two describes methods for stability and shelf life assessment including food storage trials, accelerated testing and shelf life modelling. Part three reviews the stability and shelf life of a wide range of products, including beer, soft drinks, fruit, bread, oils, confectionery products, milk and seafood.With its distinguished editors and international team of expert contributors, Food and beverage stability and shelf life is a valuable reference for professionals involved in quality assurance and product development and researchers focussing on food and beverage stability.- A comprehensive guide to factors influencing stability, methods of stability and shelf life assessment and the stability and shelf life of major products- Describes important food and beverage quality deterioration processes exploring microbiological spoilage and physical instability- Investigate the effects of ingredients, processing and packaging on stability and documents methods for stability and shelf life assessment

Part I

Deteriorative processes and factors influencing shelf life

1

Microbiological spoilage of foods and beverages

G-J.E. Nychas and E. Panagou, Agricultural University of Athens, Greece

Abstract:

Food spoilage may be defined as a process or change which renders a product undesirable or unacceptable for consumption. This complex ecological phenomenon is the outcome of the biochemical activity of microbial chemical processes which will eventually dominate according to the prevailing ecological determinants. To ensure the safety and quality of foods and beverages, the effective monitoring of the chill chain through production, transportation, distribution and storage in retail cabinets and home refrigerators is essential. Currently, a variety of different methodologies are used for assessing food spoilage, in which microbiological methods play a decisive role. Recently, the relationship between microbial growth and the chemical changes occurring during food storage has been recognised as a potential indicator which may be useful for monitoring freshness and safety. For this purpose, interesting analytical approaches have been developed for rapid and quantitative assessment of food spoilage. These are based on biosensors, sensor arrays and spectroscopy techniques in tandem with chemometrics. Various processes have been utilised to prevent the microbiological spoilage of foods and beverages, amongst which low temperature storage and heat treatment seem to be the most effective. The application of a rich carbon dioxide atmosphere as part of a modified atmosphere packaging system is also effective in suppressing spoilage micro-organisms.

Key words

chill chain

ephemeral spoilage organisms

metabolomics

microbial inhibition

modified atmosphere packaging

shelf life

1.1 Introduction

Despite the technological progress made in recent decades, changes in consumer lifestyles have made it necessary for the food industry to fulfil seemingly contradictory market demands. Consumers now expect food products of superior sensory quality and increased functional and nutritional properties, combined with a traditional, wholesome image and guaranteed safety. However, there is also a demand for less heavily preserved or processed foods, for fewer additives and technological interventions, as well as for increasingly competitive prices. At the same time, consumers expect an extended product shelf life (i.e. inhibition or control of spoilage which is mainly microbiological) and a high level of convenience in preparation and use.

In a recent consumer survey, ‘fresh/not spoiled’ and ‘quality’ were the second and third most important criteria with 37% and 33%, respectively, while ‘price’ was the most important purchase criterion for food (mentioned by 66% of respondents) (Röhr et al., 2005). This is a straightforward message as to the importance of the successful management of spoilage. To date, there are no food spoilage management systems per se, food spoilage control being linked with many other safety and hygiene systems, processes and practices, the majority of which are commonplace within the food industry.

1.2 Spoilage of foods and beverages; a microbiological approach: microbes vs indigenous enzymes

It must be emphasised that the contribution of indigenous food enzymes to spoilage is negligible when compared to the activity of microbial flora. This is mainly the case in food of animal origin (e.g., meat, fish and dairy) (Nychas and Tassou, 1997; Tsigarida and Nychas, 2001). For example, in meat and fish, the post-mortem glycolysis, caused by indigenous enzymes, ceases after the death of the animal when the final pH reaches a value of 5.4–5.5.

On the other hand, the indigenous proteolytic and lipolytic enzymes are not sufficient to affect food spoilage. However, these enzymes or other chemical or mechanical means are utilised in the artificial tenderising of meat (Nychas et al., 2007). As far as spoilage due to proteolysis is concerned, the soluble sarco-plasmic proteins probably form the initial substrate for proteolytic attack (Hasegawa et al., 1970a,b; Jay and Shelef, 1976). The proteolytic activity of bacterial action on meat and its impact on spoilage has been clearly demonstrated (Schmitt and Schmidt-Lorenz, 1992a,b; Nychas and Tassou, 1997). Proteolytic bacteria may gain an ecological advantage through penetration which gives them access to newly available resources (e.g., nutrients) which would not be accessible or available to non- or less proteolytic bacteria (Nychas et al., 2007).

There is no doubt that microbiological activity is by far the most important factor influencing the changes which cause spoilage in a food system (Nychas et al., 1998). However, it is microbial activity (growth) per se, rather than the activity of microbial enzymes and the accumulation of metabolic by-products that identifies food spoilage (Braun and Sutherland, 2004). In the context of meat spoilage, therefore, it is important to include interactions between microbial growth and its respective enzymatic activity.

1.3 Factors affecting the rate of microbiological spoilage of foods and beverages

Generally, food spoilage may be considered to be an ecological phenomenon which encompasses changes in the available nutrients (e.g., low molecular compounds) during proliferation of the bacteria which constitute microbial processes in the product regardless of its origin (e.g., animal or plant). The dominance of a particular microbial process on these products depends upon factors which persist during processing, transportation and storage. It is a well-established fact that any food ecosystem includes five categories of ecological determinants: intrinsic, processing, extrinsic, implicit and the emergent effect. These influence the establishment of particular microbial processes and determine the rate at which a maximum population is attained. This is known as ‘ephemeral/specific spoilage micro-organisms’ (E(S)SO), i.e., those which are able to adopt various ecological strategies (Koutsoumanis and Nychas, 2000; Nychas et al., 2007). These ecological strategies, developed by the ESO, are the consequence of environmental determinants (e.g., stress, the limitation or availability of nutrients and oxygen) and allow them to proliferate in all available niches. In fact, all the determinants mentioned above constitute a virtual ecological niche (n-dimensional) in which an organism is influenced in (micro) space and time (Boddy and Wimpenny, 1992). This ecological approach is pertinent to the understanding of the changes that occur in products throughout the food chain, from farm to fork. In practice, scientists and technologists involved in food industries should attempt to control or modify some or all of the parameters (e.g., temperature) noted above in order to extend the shelf life of these products.

In this chapter, emphasis will be placed on implicit (intrinsic biotic parameters) as well as extrinsic factors.

1.3.1 Implicit (intrinsic biotic parameters) factors

Ephemeral spoilage organisms (ESO)

Among the different types of spoilage, the microbial contributes greatly to the huge amount of food which is wasted and to the associated financial losses (Kantor et al., 1997). As mentioned above, a vast number of studies in food microbiology have established that spoilage can be attributed to a relatively small group of micro-organisms existing in the microbial processes within foods (for a review, see Nychas et al., 1998). This concept has contributed significantly to our understanding of food spoilage. Microbiological spoilage of foods and beverages is caused by a great variety of bacteria, moulds and yeasts.

The latter group of micro-organisms, yeasts and...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Woodhead Publishing Series in Food Science, Technology and Nutrition
• Preface
• Part I: Deteriorative processes and factors influencing shelf life
• Part II: Methods for shelf life and stability evaluation
• Part III: The stability and shelf life of particular products
• Index