Zeuthen / Bøgh-Sørensen Food Preservation Techniques

1. Auflage 2003
ISBN: 978-1-85573-714-3
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 400 Seiten

Reihe: Woodhead Publishing Series in Food Science, Technology and Nutrition

Extending the shelf-life of foods whilst maintaining safety and quality is a critical issue for the food industry. As a result there have been major developments in food preservation techniques, which are summarised in this authoritative collection. The first part of the book examines the key issue of maintaining safety as preservation methods become more varied and complex. The rest of the book looks both at individual technologies and how they are combined to achieve the right balance of safety, quality and shelf-life for particular products. - Provides an authoritative review of the development of new and old food preservation technologies and the ways they can be combined to preserve particular foods - Examines the emergence of a new generation of natural preservatives in response to consumer concerns about synthetic additives - Includes chapters on natural antimicrobials, bacteriocins and antimicrobial enzymes, as well as developments in membrane filtration, ultrasound and high hydrostatic pressure

Autoren/Hrsg.

Zeuthen, Peter

Bøgh-Sørensen, Leif

Inhaltsverzeichnis

1;Front Cover;1
2;Food Preservation Techniques;4
3;Copyright Page;5
4;Table of Contents;6
5;Contributor contact details;14
6;Chapter 1. Introduction;20
7;Part I:
Ingredients;22
7.1;Chapter
2. The use of natural antimicrobials;24
7.1.1;2.1 Introduction;24
7.1.2;2.2 Natural antimicrobials from animal sources;26
7.1.3;2.3 Natural antimicrobials from plant sources;29
7.1.4;2.4 Natural antimicrobials from microbial sources;34
7.1.5;2.5 Evaluating the effectiveness of antimicrobials;37
7.1.6;2.6 Key issues in using natural antimicrobials;38
7.1.7;2.7 Future trends;42
7.1.8;2.9 References;42
7.2;Chapter
3. Natural antioxidants;50
7.2.1;3.1 Introduction;50
7.2.2;3.2 Classifying natural antioxidants;51
7.2.3;3.3 Antioxidants from oilseeds, cereals and grain legumes;53
7.2.4;3.4 Antioxidants from fruits, vegetables, herbs and spices;54
7.2.5;3.5 Using natural antioxidants in food;56
7.2.6;3.6 Improving antioxidant functionality;60
7.2.7;3.7 Combining antioxidants with other preservation techniques;62
7.2.8;3.8 Future trends;63
7.2.9;3.9 Sources of further information and advice;64
7.2.10;3.10 References;64
7.3;Chapter
4. Antimicrobial enzymes;68
7.3.1;4.1 Introduction;68
7.3.2;4.2 Lysozymes and other lytic enzyme systems;70
7.3.3;4.3 Lactoperoxidase;75
7.3.4;4.4 Glucose oxidase and other enzyme systems;78
7.3.5;4.5 Combining antimicrobial enzymes with other
preservation techniques;80
7.3.6;4.6 Future trends;83
7.3.7;4.7 Sources of further information and advice;85
7.3.8;4.8 References;85
7.4;Chapter 5.
Combining natural antimicrobial systems with other preservation techniques: the case of meat;90
7.4.1;5.1 Introduction;90
7.4.2;5.2 Microbial contamination of meat;91
7.4.3;5.3 Using organic acids to control microbial contamination;94
7.4.4;5.4 Regulatory and safety issues;99
7.4.5;5.5 Combining organic acids with other preservation techniques;101
7.4.6;5.6 Conclusion;103
7.4.7;5.7 References;104
7.5;Chapter
6. Edible coatings;109
7.5.1;6.1 Introduction: the development of edible coatings;109
7.5.2;6.2 How edible coatings work: controlling internal gas composition;111
7.5.3;6.3 Selecting edible coatings;111
7.5.4;6.4 Gas permeation properties of edible coatings;111
7.5.5;6.5 Wettability and coating effectiveness;114
7.5.6;6.6 Determining diffusivities of fruits;116
7.5.7;6.7 Measuring internal gas composition of fruits;119
7.5.8;6.8 Future trends;119
7.5.9;6.9 References;121
8;Part II:
Traditional preservation technologies;126
8.1;Chapter
7. The control of pH;128
8.1.1;7.1 Introduction;128
8.1.2;7.2 The effect of pH on cellular processes;129
8.1.3;7.3 Combining pH control with other preservation techniques;131
8.1.4;7.4 The effect of pH on the growth and survival of foodborne pathogens;132
8.1.5;7.5 The use of pH control to preserve dairy, meat and fish products;133
8.1.6;7.6 The use of pH control to preserve vegetables, fruits,
sauces and cereal products;137
8.1.7;7.7 Future trends;140
8.1.8;7.8 References;141
8.2;Chapter
8. The control of water activity;145
8.2.1;8.1 Introduction;145
8.2.2;8.2 The concept of water activity;146
8.2.3;8.3 Water activity, microbial growth, death and survival;148
8.2.4;8.4 Combining control of water activity with other
preservation techniques;153
8.2.5;8.5 Applications: fully dehydrated, intermediate and high
moisture foods;154
8.2.6;8.6 Measurement and prediction of water activity in foods;161
8.2.7;8.7 Future trends;168
8.2.8;8.8 Sources of further information and advice;168
8.2.9;8.9 References;168
8.3;Chapter
9. Developments in conventional heat treatment;173
8.3.1;9.1 Introduction;173
8.3.2;9.2 Thermal technologies: cookers;173
8.3.3;9.3 Thermal technologies: retorts;176
8.3.4;9.4 Using plastic packaging in retort operations;181
8.3.5;9.5 Dealing with variables during processing;186
8.3.6;9.6 The strengths and weaknesses of batch retorts;192
8.3.7;9.7 Future trends;194
8.3.8;9.8 Sources of further information and advice;195
8.3.9;9.9 References;197
8.4;Chapter
10. Combining heat treatment, control of water activity and pressure to preserve foods;198
8.4.1;10.1 Introduction;198
8.4.2;10.2 The thermal destruction of microorganisms;198
8.4.3;10.3 The effects of dehydration and hydrostatic pressure on
microbial thermotolerance;201
8.4.4;10.4 Temperature variation and microbial viability;206
8.4.5;10.5 Combining heat treatment, hydrostatic pressure and
water activity;210
8.4.6;10.6 Conclusions;216
8.4.7;10.7 References;217
8.5;Chapter
11. Combining traditional and new preservation techniques to control pathogens: the case of E. coli;223
8.5.1;11.1 Introduction;223
8.5.2;11.2 Pathogen growth conditions: the case of E. Coli;224
8.5.3;11.3 The heat resistance of E. coli;228
8.5.4;11.4 Problems in combining traditional preservation
techniques;231
8.5.5;11.5 Combining traditional and new preservation techniques;235
8.5.6;11.6 Conclusions and future trends;238
8.5.7;11.7 References;240
8.6;Chapter
12. Developments in freezing;247
8.6.1;12.1 Introduction;247
8.6.2;12.2 Pre-treatments;248
8.6.3;12.3 Developments in conventional freezer technology;251
8.6.4;12.4 The use of pressure in freezing;252
8.6.5;12.5 Developments in packaging;253
8.6.6;12.6 Cryoprotectants;254
8.6.7;12.7 References;255
9;Part III:
Emerging preservation techniques;260
9.1;Chapter
13. Biotechnology and reduced spoilage;262
9.1.1;13.1 Introduction: mechanisms of post-harvest spoilage in
plants;262
9.1.2;13.2 Methods for reducing spoilage in fruits;263
9.1.3;13.3 Methods for reducing spoilage in vegetables;268
9.1.4;13.4 Enhancing plant resistance to diseases and pests;270
9.1.5;13.5 Future trends;274
9.1.6;13.6 Sources of further information and advice;275
9.1.7;13.7 References;276
9.2;Chapter
14. Membrane filtration techniques in food preservation;282
9.2.1;14.1 Introduction;282
9.2.2;14.2 General principles of membrane processing;283
9.2.3;4.3 Filtration equipment;290
9.2.4;14.4 Using membranes in food preservation;295
9.2.5;14.5 Future trends;300
9.2.6;14.6 Sources of further information and advice;301
9.2.7;14.7 References;301
9.2.8;14.8 Acknowledgement;302
9.3;Chapter
15. High-intensity light;303
9.3.1;15.1 Introduction;303
9.3.2;15.2 Process and equipment;306
9.3.3;15.3 Microbial inactivation;308
9.3.4;15.4 Inactivation of pathogens and spoilage bacteria;311
9.3.5;15.5 Applications, strengths and weaknesses;315
9.3.6;15.6 Sources of further information and advice;318
9.3.7;15.7 References;320
9.4;Chapter
16. Ultrasound as a preservation technology;322
9.4.1;16.1 Introduction;322
9.4.2;16.2 Principles: acoustic cavitation;324
9.4.3;16.3 Ultrasound as a preservation technology;330
9.4.4;16.4 Ultrasonic inactivation of microorganisms, spores and enzymes;336
9.4.5;16.5 Ultrasound in combination with other preservation techniques;342
9.4.6;16.6 Ultrasonic equipment;347
9.4.7;16.7 Conclusions;351
9.4.8;16.8 References;352
9.5;Chapter
17. Modified atmosphere packaging (MAP);357
9.5.1;17.1 Introduction;357
9.5.2;17.2 The use of MAP to preserve foods;358
9.5.3;17.3 MAP gases;363
9.5.4;17.4 Packaging materials;366
9.5.5;17.5 Quality assurance;367
9.5.6;17.6 Using MAP and other techniques to preserve fresh and
minimally processed produce;368
9.5.7;17.7 Using MAP and other techniques to preserve processed meat, bakery and other products;370
9.5.8;17.8 Future trends;373
9.5.9;17.9 References;374
9.6;Chapter
18. Pulsed electric fields;379
9.6.1;18.1 Introduction;379
9.6.2;18.2 Principles and technology;380
9.6.3;18.3 Mechanisms of microbial inactivation;389
9.6.4;18.4 Critical factors determining microbial inactivation;396
9.6.5;18.5 Combinations with other preservation techniques;407
9.6.6;18.6 Effects on enzymes;413
9.6.7;18.7 Effects on food proteins;420
9.6.8;18.8 Effects on vitamins and other quality attributes of foods;422
9.6.9;18.9 Strengths and weaknesses as a preservation technology;425
9.6.10;18.10 Applications;430
9.6.11;18.11 Acknowledgements;434
9.6.12;18.12 References;434
9.6.13;18.13 Patents;444
9.7;Chapter
19. High hydrostatic pressure technology in food preservation;447
9.7.1;19.1 Introduction;447
9.7.2;19.2 Principles and technologies;448
9.7.3;19.3 Effects of high pressure on microorganisms;452
9.7.4;19.4 Effects of high pressure on quality-related enzymes;453
9.7.5;19.5 Effects of high pressure on nutritional value and colour
quality;456
9.7.6;19.6 Effects of high pressure on water-ice transition of foods;457
9.7.7;19.7 Future trends;459
9.7.8;19.8 Sources of further information and advice;460
9.7.9;19.9 Acknowledgements;460
9.7.10;19.10 References;460
10;Part IV:
Assessing preservation requirements;468
10.1;Chapter
20. Modelling food spoilage;470
10.1.1;20.1 Introduction: spoilage mechanisms;470
10.1.2;20.2 Approaches to spoilage modelling;471
10.1.3;20.3 Developing spoilage models;472
10.1.4;20.4 Measurement techniques;477
10.1.5;20.5 Constructing models;481
10.1.6;20.6 Applications of spoilage models;483
10.1.7;20.7 Limitations of models;484
10.1.8;20.8 Future trends;486
10.1.9;20.9 Sources of further information and advice;488
10.1.10;20.10 References;489
10.2;Chapter
21. Modelling applied to foods: predictive microbiology for solid food systems;494
10.2.1;21.1 Introduction;494
10.2.2;21.2 Microbial growth in solid food systems: colony dynamics;495
10.2.3;21.3 Factors affecting microbial growth;497
10.2.4;21.4 Microbial growth dynamics: cell level;501
10.2.5;21.5 Microbial growth dynamics: colony level;505
10.2.6;21.6 Evaluating types of model;508
10.2.7;21.7 Selecting the right modelling approach;515
10.2.8;21.8 Conclusions and future trends;518
10.2.9;21.9 Sources of further information and advice;520
10.2.10;21.10 References;521
10.3;Chapter
22. Modelling applied to processes: the case of thermal preservation;526
10.3.1;22.1 Introduction;526
10.3.2;22.2 Understanding thermal inactivation;528
10.3.3;22.3 Modelling microbial death and survival;529
10.3.4;22.4 Simulating thermal processes;532
10.3.5;22.5 Using models to improve food safety and quality;536
10.3.6;22.6 Conclusions;540
10.3.7;22.7 References;541
10.4;Chapter
23. Food preservation and the development of microbial resistance;543
10.4.1;23.1 Introduction;543
10.4.2;23.2 Methods of food preservation;546
10.4.3;23.3 Preservation techniques and food safety;550
10.4.4;23.4 Understanding microbial adaptation to stress;553
10.4.5;23.5 Future trends;559
10.4.6;23.6 Sources of further information and advice;562
10.4.7;23.7 Acknowledgements;563
10.4.8;23.8 References;563
10.5;Chapter
24. Monitoring the effectiveness of food preservation;571
10.5.1;24.1 Introduction;571
10.5.2;24.2 HACCP and other monitoring systems;572
10.5.3;24.3 Instrumentation for monitoring the effectiveness of food preservation during processing;575
10.5.4;24.4 Monitoring the effectiveness of food preservation during storage and distribution;578
10.5.5;24.5 Future trends;584
10.5.6;24.6 References;584
11;Index;586

Leseproben

2

The use of natural antimicrobials

P.M. Davidson; S. Zivanovic    University of Tennessee, USA

2.1 Introduction

Food antimicrobials are chemical compounds added to or present in foods that retard microbial growth or kill microorganisms. The functions of food antimicrobials are to inhibit or inactivate spoilage microorganisms and pathogenic microorganisms. The latter function has increased in importance in the past 10–15 years as food processors search for more and better tools to improve food safety (Davidson, 2001). Prior to recent approvals of certain compounds to control foodborne pathogens by worldwide regulatory agencies, one of the only uses of antimicrobials to control a pathogen was nitrite or nitrate against Clostridium botulinum in cured meats.

A number of compounds are approved by international regulatory agencies for use as direct food antimicrobials (Table 2.1). The question arises as to why, with so many compounds already approved for use in foods, would the food processing industry need a greater number of food antimicrobials? The primary incentive for searching for effective antimicrobials among naturally occurring compounds is to expand the spectrum of antimicrobial activity over that of the regulatory-approved substances. Most of the traditional, currently approved food antimicrobials have limited application due to pH or food component interactions. For example, organic acids function at low concentrations only in high acid foods (generally less than pH 4.5–4.6). This is because the most effective antimicrobial form is the undissociated acid which exists in majority only at a pH below the pKa of the compound. All regulatory-approved organic acids used as antimicrobials have pKa values less than 5.0 (Table 2.2) which means their maximum activity will be in high-acid foods. For food products with a pH of 5.5 or greater, there are very few compounds that are effective at low concentrations. Another factor leading to reduced effectiveness among food antimicrobials is food component interactions. Most food antimicrobials are amphiphilic. As such, they can solubilize in or be bound by lipids or hydrophobic proteins in foods making them less available to inhibit microorganisms in the food product.

Table 2.1

Current regulatory-approved compounds for use as direct addition food antimicrobials

Compound or group of compounds

Alkyl esters of p-hydroxybenzoic acid (Parabens; methyl, ethyl, propyl, butyl and heptyl)

Acetic acid and acetate salts, diacetates, dehydroacetic acid

Benzoic acid and benzoate salts

Dimethyl dicarbonate, diethyl dicarbonate

Lactic acid and lactate salts

Lysozyme

Natamycin

Nisin

Nitrites and nitrates

Phosphates

Propionic acid and propionate salts

Sorbic acid and sorbate salts

Sulfite derivatives

Table 2.2

pKa of regulatory-approved organic acids

Compound or group of compounds

pKa

Acetic acid

4.75

Benzoic acid

4.19

Lactic acid

3.79

Propionic acid

4.87

Sorbic acid

4.75

Interest in natural antimicrobials is also driven by the fact that international regulatory agencies are generally very strict about requirements for toxicological evaluation of novel direct food antimicrobials. In many parts of the world, toxicological testing of new synthetic compounds could take many years and many millions of dollars to obtain approval. For some types of food additives a payback may be possible (e.g., artificial sweeteners), but for food antimicrobials it is less likely that obtaining approval would be profitable.

An argument often used to justify natural antimicrobials is that they will produce ‘green’ labels, i.e., one with few or no ‘synthetic’ additives in the ingredient list. While this rationale may be true, it must be remembered that many of the antimicrobial compounds approved for use in foods today come from natural sources (Table 2.3). If a truly effective antimicrobial was discovered from a natural source, it may be more economically feasible to synthesize it than to extract it from a natural source. This justification also leads consumers to the mistaken belief that food additives currently in use are potentially toxic and should be avoided.

Table 2.3

Natural sources for antimicrobials

Compound or group of compounds

Natural source

Acetic acid

Vinegar

Benzoic acid

Cranberries, plums, prunes, cinnamon, cloves, and most berries

Lactic acid

Lactic acid bacteria

Propionic acid

Swiss cheese (Propionibacterium freudenreichii ssp. shermanii)

Sorbic acid

Rowanberries

In addition to potential benefits associated with natural antimicrobials in foods, there are a number of potential concerns that need to be examined with respect to food safety. For example, if an antimicrobial is to be used exclusively to inhibit a pathogenic microorganism, it must be uniformly effective, stable to storage, and stable to any processes to which it is exposed. Standardized assays for activity need to be developed to ensure that the antimicrobial compounds retain potency. Finally, producers and users of natural antimicrobials that make claims for efficacy of use will be likely to be liable for any claims they make. In short, natural antimicrobials have excellent potential but probably will not produce miracles.

2.2 Natural antimicrobials from animal sources

Naturally occurring antimicrobials may be classified by source. There are compounds from animal, plant and microbial sources. As stated above, some naturally occurring antimicrobials have been approved for direct addition into foods by regulatory agencies including lactoferrin, lysozyme, natamycin and nisin.

2.2.1 Chitosan

Chitosan, (1 ? 4)–2-amino-2-deoxy-ß-D-glucan, is a natural constituent of fungal cell walls (Ruiz-Herrera, 1992). It is produced commercially from chitin, a by-product of shellfish processing, by alkaline deacetylation. Chitosan is the designated name for the series of polymers with different ratios of glucosamine (GlcN) and N-acetyl glucosamine (GlcNAc). Most commercial chitosans have less than 30% acetylated units (referred to as degree of acetylation less than 30%) and molecular weights between 100 and 1,200 kDa (Li et al., 1997; Onsoyen and Skaugrud, 1990).

Chitosan inhibits growth of foodborne molds, yeasts and bacteria including Aspergillus flavus, Saccharomyces cerevisiae, Zygosaccharomyces bailii, Mucorracemosus, Byssochlamys spp., Botrytis cinerea, Rhizopus stolonifer and Salmonella, Staphylococcus aureus, Escherichia coli, Yersinia enterocolitica, Listeria monocytogenes and Lactobacillus fructivorans (Roller and Covill, 2000; Sudarshan et al., 1992; Papineau et al., 1991; Wang, 1992). However, reported minimum inhibitory concentrations for both bacteria and yeasts vary widely from 0.01–5.0% depending on polymer characteristics and pH, temperature, and presence of interfering substances such as proteins and fats (Chen et al., 1998; Rhoades and Roller, 2000; Roller and Covill, 1999; Sudarshan et al., 1992; Tsai and Su, 1999; Tsai et al., 2000). Chitosan may directly affect the microbial cell by interaction with the anionic cell wall polysaccharides or components of the cytoplasmic membrane resulting in altered permeability or prevention of transport (Tsai and Su, 1999; Fang et al., 1994).

Darmadji and Izumimoto (1994) showed that 1% chitosan was necessary for reduction of only 1–2 logs of Pseudomonas, staphylococci, and total bacteria count in minced beef patties and lower concentrations (0.2 and 0.5%) had no effect on the microflora. In contrast, fresh strawberries and bell peppers dipped in acidic chitosan solutions and inoculated with B. cinerea or R. stolonifer were reported to have a shelf life equivalent to that of fruit treated with conventional fungicide (El-Ghaouth et al., 1991; El-Ghaouth, 1997). Roller and Covill (1999) reported that 0.1 to 5 g/l of chitosan glutamate inhibited growth of eight yeast species in apple juice at 25 °C. The most sensitive strain was Z. bailii, which was completely inactivated by chitosan glutamate at 0.1 g/l. For S. cerevisiae, the minimum inhibitory concentration was 0.4 g/l and no resumption of growth was observed after 32 days.

2.2.2 Lactoferrin

In milk and colostrum, the primary iron-binding protein is lactoferrin. Lactoferrin has two iron binding sites per molecule. Lactoferrin is inhibitory by itself to a number of microorganisms including Bacillus subtilis, B. stearothermophilus, Listeria...