Using plastic packaging in retort operations
Food packaging is evolving, conventional cylindrical cans are changing shape and becoming thinner and so more susceptible to damage by inappropriate differential pressure during retorting. Retortable plastics are becoming commonplace and a growing number of new products are appearing in heat sealable semi-rigid plastic containers with multi-layer plastic lids or multi-layer, heat-sealed flexible pouches. Consequently, retort technology is evolving to match. Process styles and process control...
Regulatory and safety issues
In the European community, the legal basis for organic acids as food additives is the directive 87 107 EEC. Lactic acid European designation E270 , acetic acid E260 , and acetates, such as potassium acetate E261 , calcium acetate E263 and sodium acetates E262 are generally permitted food additives under EC directive 95 2 EC. Sodium lactate E325 , potassium lactate E326 and calcium lactate E327 are food additives, which may be added on a quantum satis basis to foods Directive 92 5 EC annex 1 ....
Heat shocks improve thermal death
In most studies, the determination of heat resistance involves the addition of a small volume of microbial suspension to large volumes of a heating medium. Cells are then removed at desired intervals and cooled. This means that, at the laboratory scale, the kinetics of temperature variation during a thermal process are often not considered as a technological variable. As a result, contrary to temperature level and exposure time, literature dealing with the influence of the temperature variation...
Preservation Of Food Through Osmotic Method
BARAT, J, CHIRALT, A and FITO, P 2000 'Structural change kinetics in osmotic dehydration of apple tissue', Proceedings of the 12th International Drying Symposium, Elsevier Science, Amsterdam. BOGH-SORENSEN, L 2000 'Maintaining safety in the cold chain', in Kennedy, C ed. , Managing Frozen Foods, Woodhead Publishing Limited, Cambridge. BOWATER, F J 2001 'Rapid chilling plant compared to conventional systems', in Rapid Cooling of Food, Meeting of IIR Commission C2, Bristol UK . BOWLING, R A,...
Water activity microbial growth death and survival
The optimum aw for growth of the majority of microorganisms is in the range 0.99-0.98. Every microorganism has limiting aw values below which it will not grow, form spores, or produce toxic metabolites Beuchat, 1987 . Considering aw in relation to microbial stability, the minimum aw values that permit microbial growth for different types of microorganisms are of great concern. Table 8.1 presents the aw values of various foods and their associated microbial spoilage, showing also the...
Ultrasound as a preservation technology
T. J. Mason and L. Paniwnyk, University of Coventry, UK and F. Chemat, University of R union, France 16.2 Principles acoustic cavitation 16.3 Ultrasound as a preservation technology 16.4 Ultrasonic inactivation of microorganisms, spores and enzymes 16.5 Ultrasound in combination with other preservation techniques
Low temperatures enhance resistance to dehydration
Experiments in our laboratory with S.cerevisiae help to clarify the role played by cell membranes in the combined effects of temperature and hydration Beney et al., 2001 . The extent of S.cerevisiae survival by exposure to osmotic stress of 100 MPa was increased by a factor of 2.5 after cooling of cells from 250C to 10 C prior to osmotic stress Fig. 10.10 . Such enhancement of yeast osmoresistance was attributed to the fact that that the cooling step at 10 C reduced the osmotic destabilisation...
Natural antioxidants
J. Pokorny, Prague Institute of Chemical Technology, Czech Republic 3.2 Classifying natural antioxidants 3.3 Antioxidants from oilseeds, cereals and grain legumes 3.4 Antioxidants from fruits, vegetables, herbs and spices 3.5 Using natural antioxidants in food 3.6 Improving antioxidant functionality 3.7 Combining antioxidants with other preservation techniques 3.9 Sources of further information and advice
Cereal products
The baking process destroys vegetative micro-organisms and mould spores, but not bacterial spores. In some wheat breads prepared without dough acidification, the combination of the hurdles pH 5.4-6.0 and aw 0.94-0.97 may still permit growth of some Bacillus strains. To prevent this, acetate is sometimes added to the flour to give a level of about 1-2 mmoles of undissociated acetic acid in the bread. Sourdoughs have pH values around 4.0, brought about by fermentation of maltose and glucose to...
The concept of water activity
A review of basic and applied thermodynamics is required to understand the aw concept Robinson and Stokes, 1965, Welti and Vergara, 1997 . The concept of 'activity', assuming thermodynamic equilibrium, states that aw is equal to f fa, where f is the fugacity of water in the system i.e., the escaping tendency of water from solution and o is the fugacity of pure water at the same temperature. For an ideal gas in a mixture, the fugacity is coincident with its partial pressure. For a real gas, the...
Food preservation techniques
Peter Zeuthen and Leif Begh-Serensen Boca Raton Boston New York Washington, DC Published by Woodhead Publishing Limited Abington Hall, Abington Cambridge CB1 6AH England Published in North America by CRC Press LLC 2000 Corporate Blvd, NW Boca Raton FL 33431 USA First published 2003, Woodhead Publishing Limited and CRC Press LLC 2003, Woodhead Publishing Limited The authors have asserted their moral rights. This book contains information obtained from authentic and highly regarded sources....
Filtration equipment 1431 Membranes
The development of membranes is often described in terms of first-, second- and third-generation. The first membranes to be used successfully on a large scale were composed of cellulose acetate. These are prepared as a thin 0.1-1.0 m 'skin' on a much thicker porous support. Their application, however, is limited to a narrow pH range 2-8 at most and limited temperature lt 40 C , which places a severe restriction on their use, especially on cleaning operations, which are vital to food processing....
Sources of further information and advice 981 Batch retort system suppliers
The following list of batch retort suppliers is intended as a guide and is not exhaustive. Breedstraat 3 B-9100 Sint Niklaas Belgium Tel 32 3 780 1398 http www.fmcfoodtech.com Breedstraat 3 B-9100 Sint Niklaas Belgium Tel 32 3 780 1398 http www.fmcfoodtech.com H G Molenaar amp Co Ltd Water immersion PO Box 5, Paarl 7622 South AfTica Tel 27 21 868 2210 Hermann Stock Maschinenfabrik GmbH Rendsburger Strasse 93, D - 24537 Neumunster Germany Tel 49 4321 1880 http www.stocksterilisation.com Water...
References Vez
BANK, H.L., SCHMEHL, J.J. and DRATCH R.J. 1990. Bactericidal effectiveness of modulated UV light. Appl. Environl. Microbiol. 56 3888-3889. BARBOSA-CANOVAS, G.V., PALOU, E., POTHAKAMURY, U.R. and SWANSON, B.G. 1997. Application of light pulses in the sterilization of foods and packaging materials. Nonthermal Preservation of Foods. Ch. 6, 139-161. Marcel-Dekker. New York. BARBOSA-CANOVAS, G.V., SCHAFFNER, D.W., PIERSON, M.D. and ZHANG, Q.H. 2000. Pulsed Light Technology. J. Food Safety Suppl....
Methods for reducing spoilage in fruits
The dependence of climacteric fruits on ethylene to regulate the ripening rate have made them the focus of much biotechnological research aimed at Fig. 13.1 Ethylene biosynthetic pathway Yang and Hoffmann, 1984 . Met, methionine SAM, S-adenosyl methionine ACC, 1-aminocyclopropane-1-carboxylic acid. increasing the shelf life while not affecting other quality characteristics. Most of the approaches have been aimed at controlling the amount of ethylene synthesised by the fruits or the sensitivity...
Allium
Onion Allium cepa and garlic Allium sativum have been shown to inhibit growth and toxin production of many microorganisms including B. cereus, C. botulinum type A, E. coli, Lactobacillus plantarum, Salmonella, Shigella, and S. aureus, and the fungi A. flavus, A. parasiticus, Candida albicans, and species of Cryptococcus, Rhodotorula, Saccharomyces, Torulopsis and Trichosporon Saleem and Al-Delaimy, 1982 Conner and Beuchat, 1984 Beuchat, 1994 Gonzalez-Fandos et al., 1994 . Cavallito and Bailey...
Weaknesses
Whilst the batch nature of retorts is one of their biggest strengths, it is also one of their biggest weaknesses the stop start arrangement of a retort process and the constant need to move from one environment to another inside the pressure vessels that comprise a bank of retorts will never reach the steady state efficiency of a continuous process in which an environment can be allowed to reach optimum stability as a constant procession of containers moves through. This implies both thermal...
Other lytic enzymes
Apart from lysozyme, two other types of hydrolytic enzymes may work bacterio-lytically. Firstly, as already covered above, the N-acetylmuramoyl-L-alanine amidases catalyse cleavage of the junction between the peptidoglycan polysaccharide backbone and the peptide crosslinks additionally certain endopep-tidases are known to catalyse the hydrolysis of the peptide sidechains. Knowledge is lacking on enzymatic cleavage of the interpeptide bridges in peptidoglycan, however. Streptomyces spp. express...
The control of pH
F.-K. L cke, University of Applied Sciences Fulda , Germany 7.2 The effect of pH on cellular processes 7.3 Combining pH control with other preservation techniques 7.4 The effect of pH on the growth and survival of foodborne pathogens 7.5 The use of pH control to preserve dairy, meat and fish products 7.6 The use of pH control to preserve vegetable, fruits, sauces and cereal products
Spices and their essential oils
Spices and their essential oils have varying degrees of antimicrobial activity. Among the spices, cloves, cinnamon, oregano, thyme, sage, rosemary, basil and vanillin have the strongest antimicrobial activity. The major antimicrobial components of clove Syzygium aromaticum and cinnamon Cinnamomum zeylanicum essential oils are eugenol 2-methoxy-4- 2-propenyl -phenol and cinnamic aldehyde 3-phenyl-2-propenal , respectively. Smith-Palmer et al. 1998 determined that the 24 hr minimum inhibitory...
The control of pH 1
F.-K. L cke, University of Applied Sciences Fulda , Germany The pH is the negative logarithm of the hydrogen ion activity where activity approximates concentration if the solution becomes more dilute . It is evident that pH is an important factor affecting growth of micro-organisms in food because it affects i microbial energy metabolism involving the build-up of gradients of hydrogen ions across membranes, and ii microbial enzyme activity and stability of cellular macromolecules. Moreover, pH...
Other ways of improving antioxidant functionality
During food storage, oxygen penetrates into food material by diffusion from air and therefore food lipids are oxidized from the surface. In some cases it is sufficient to apply antioxidants, especially spices, only on the surface. The process is particularly useful in the case of oxylabile sensitive to oxidation material, such as fish muscle. Food may be packaged, e.g. vacuum packed in plastic materials with a low or very low Oxygen Transmission Rate 0-TR thus reducing or inhibiting oxygen...
Using membranes in food preservation
Membranes were first developed commercially as a means of purifying water by RO, and for purifying waste water. Applications in food processing have since widened considerably. Membrane techniques can contribute to food preservation in two ways. Firstly, membranes reject all micro-organisms within the retentate and thus the permeate will be sterile on production. Hence, provided that the relevant components of the food fluid permeate the membrane, then membrane processing can be used per se as...
Cryoprotectants
Cryoprotectants are compounds that improve the quality and extend the shelf-life of frozen foods. A wide variety of cryoprotective compounds are available. These include sugars, amino acids, polyols, methyl amines, carbohydrates, some proteins and even inorganic salts, such as potassium phosphate and ammonium sulphate. A newer area of cryoprotection is the use of antifreeze proteins AFPs Hedges, 2002 . The addition of AFPs to meat has been shown to control ice crystal size, reducing drip loss...
Applications of natural antioxidants for the stabilization of essential oils
Essential oils are not lipids because they do not contain bound fatty acids, but they are as easily oxidized as lipids are and their oxidation proceeds along similar lines. Many essential oils contain components resistant to oxidation or even possessing antioxidant properties, but other essential oils are very sensitive to oxidation, especially citrus essential oils. During their oxidation, citrus odour notes disappear, and intensities of woody, acidic and heavy odour notes develop Pokorny et...
Prediction of water activity in practical applications
aw can be influenced in at least three ways during the preparation of dried, intermediate and high moisture foods 1. Water can be removed by a dehydration, evaporation or concentration process. 2. Additional solute can be added. The impregnation of solute can be performed by moist infusion or by dry infusion. Moist infusion consists in soaking the food pieces in a water-solute solution of lower aw while dry infusion involves direct mixing of food pieces and solutes in required proportions. When...
A historical view of edible coatings
Wax was the first edible coating used on fruits and vegetables. The Chinese applied wax coatings to oranges and lemons in the twelfth and thirteenth centuries Hardenburg, 1967 . Although the Chinese did not realize that the full function of edible coatings was to slow down respiratory gas exchange, they found that wax coated fruits could be stored longer than non-waxed fruits. In the 1930s hot-melt paraffin waxes became commercially available as edible coatings for fresh fruits such as apples...
The effect of pH on the growth and survival of foodborne pathogens
With respect to their capabilities to grow at acid pH, micro-organisms of relevance to foods may be subdivided into five groups Group 1 comprises virtually all species of yeasts and moulds. The minimum pH for their growth is outside the range of the pH of foods as acid as lemon juice. Hence, pH as a single hurdle will not be able to preserve a food from spoilage by these organisms. Group 2 comprises bacteria that are still able to grow in acid foods with pH values between 3 and 4. These...
Edible coatings
6.1 Introduction the development of edible coatings 6.2 How edible coatings work controlling internal gas composition 6.4 Gas permeation properties of edible coatings 6.5 Wettability and coating effectiveness 6.6 Determining diffusivities of fruits 6.7 Measuring internal gas composition of fruits
References Ups
ASTM 1987 Annual Book of ASTM Standards, Philadelphia, American Society for Testing and Materials. AYDT T P, WELLER C L and testin R F 1991 'Mechanical and barrier properties of edible corn and wheat protein films', Trans ASAE, 34 1 207. BANKS n h 1984 'Some effects of TAL Pro-long coating on ripening bananas', J Exp Bot 35 127. BANKS N H and KAYS S J 1988 'Measuring internal gases and lenticel resistance to gas diffusion in potato tubers', J Am Hortic Sei, 113 4 577. BEN-YEHOSHUA S 1969 'Gas...
Factors that influence the efficiency of the lactoperoxidase system
Addition of nisin together with lactoperoxidase and glucose glucose-oxidase to pre-sterilised milk inoculated with L. monocytogenes was demonstrated to exert a pronounced synergistic and lasting bacteriocidal effect on L. monocytogenes as no cells were detected in the inoculated milk during 15 days of incubation of the milk at 250C Boussel et al., 2000 . Likewise, designed additions of nisin and bacteriocin-producing lactic acid bacteria in conjunction with activation of the lactoperoxidase...
Natural antimicrobials from microbial sources 241 Natamycin Pimaricin
Natamycin C33H47NO13 MW 665.7 Da or pimaricin is an antifungal agent. It was first isolated from Streptomyces natalensis, a microorganism found in soil from Natal, South Africa Anonymous, 1991 . Natamycin is active against nearly all molds and yeasts, but has little or no effect on bacteria or viruses. Most molds are inhibited by 0.5 to 6 ug ml natamycin while some species require 10-25 g ml. Most yeasts are inhibited by 1.0 to 5.0 ug ml natamycin. Natamycin inhibits the production of...
References
ALIGIANNIS N, KALPOUTZAKIS E, MITAKU S and CHINOU IB 2001 , 'Composition and antimicrobial activity of the essential oils of two Origanum species', J Ag Food Chem, 49, 4168-70. ANONYMOUS 1991 , 'Delvocid Technical Bulletin', Gist-brocades Food Ingredients Inc. King of Prussia, PA. AYRES JC and DENISEN EL 1958 , 'Maintaining freshness of berries using selected packaging materials and antifungal agents', Food Technol, 12, 562. AYRES JC, WALKER HW, FANELLI MJ, KING AW and THOMAS F 1956 , 'Use of...
Effects of lysozyme in real food product trials
The presence of egg white lysozyme inhibits the outgrowth of C. tyrobutyricum in ripened, yellow cheeses such as Edam or Gouda Bester and Lombard, 1990 Wasserfall and Teuber, 1979 . When the lysozyme is added just before the addition of rennet in cheese making, lysozyme both kills resting vegetative C. tyrobutyricum cells, delaying the outgrowth of spore cells into vegetative cells, and retards proliferating vegetative cells Wasserfall and Teuber, 1979 . As discussed in more detail in section...
Conclusion
Natural antimicrobial agents are present both during meat production and meat processing and also may be introduced as an 'additional line of defence'. With good hygiene practice strictly observed, application of 1-3 lactic or acetic acid on carcasses and meat cuts allows for an additional microbial reduction of 1,5 or more log10 units, with observed prolonged antibacterial effects. Hot water washes of carcasses may give similar immediate microbial reduction, but lack prolonged effects the same...
High hydrostatic pressure technology in food preservation
Indrawati, A. Van Loey, C. Smout and M. Hendrickx, Katholieke Universiteit Leuven, Belgium 19.2 Principles and technologies 19.3 Effects of high pressure on microorganisms 19.4 Effects of high pressure on quality-related enzymes 19.5 Effects of high pressure on nutritional and colour quality 19.6 Effects of high pressure on water-ice transition of foods 19.8 Sources of further information and advice
Antibacterial efficiency of glucose oxidase in model systems and real foods
Addition of glucose and a commercial enzyme preparation containing glucose oxidase as well as catalase was shown to suppress significantly the growth of Pseudomonas fragi, a common fish spoilage organism, in both nutrient broth and in a fish extract medium inoculated at ambient temperature 260C Yoo and Rand, 1995 . Dosage of more than 2.0 Enzyme Units mL of the glucose oxidase preparation with 16 mg mL glucose in the fish extract medium lowered the pH to approximately pH 4 due to gluconic acid...
Applications fully dehydrated intermediate and high moisture foods
Improved knowledge of the relation of water in foods led to the rediscovery and optimization of old preservation techniques and to a renewed interest in foods that are shelf-stable by control of water activity. This applies for fully dehydrated, intermediate and high moisture traditional foods with inherent empiric hurdles, and also for novel products, especially high water activity foods, for which the hurdles are intelligently selected and intentionally applied. Traditional fully dehydrated...
Selecting edible coatings
If a coating is too thick, detrimental effects can result because the internal oxygen concentration is below a desirable and beneficial level and there is an associated increased carbon dioxide concentration which is above a critical tolerable level. These conditions lead to anaerobic fermentation. This can be remedied by 1 developing several edible coatings, 2 controlling wettability of edible coatings, 3 measuring gas permeation properties of selected coatings, 4 measuring diffusion...
Intervention strategies
The conversion of fresh meat cuts to meat products is characterised by a the introduction of non-meat compounds or additives, some of which may have antimicrobial potential, b the production process and associated risks for microbial contamination and simultaneously applied physical measures with a more or less microbicidal effect, as heat treatment. Hygiene is the primary factor for controlling the initial microbial contamination of fresh meat surfaces. The likelihood of contamination with...
References Okp
ACUFF G R, VANDERZANT C, SAVELL J W, JONES D K, GRIFFIN D B and EHLERS J G 1987 , 'Effect of acid decontamination of beef subprimal cuts on the microbiological and sensory characteristics of steaks', Meat Sci, 19, 207-229. ANDERSON M E and MARSHALL R T 1989 , 'Interaction of concentration and temperature of acetic acid solution on reduction of various species of microorganisms on beef surfaces', J Food Prot, 52, 312-315. BARANYI J 2000 , 'Predictive microbiology for the meat industry', Proc....
The use and effect of enzymes as antibacterial agents
Enzymes may exert antibacterial activity by a number of different mechanisms Table 4.1 . Lysozymes and other antimicrobial, lytic enzymes mainly elicit their antibacterial activity by inducing bacteriolysis via catalytic cleavage of cell-surface polymers or cell-wall junctions. As will be discussed later in this chapter, lysozyme may also work bacteriocidally by mechanisms that are independent of its catalytic activity. Lactoperoxidase, and other peroxidase systems, work antimicrobially via...
Isothiocyanates
Mustard seed has as a primary pungency component the compound allyl isothiocyanate AIT . Isothiocyanates R N C S are derivatives from glucosinolates in cells of plants of the Cruciferae or mustard family cabbage, kohlrabi, Brussel sprouts, cauliflower, broccoli, kale, horseradish, mustard, turnips, rutubaga . These compounds are formed from the action of the enzyme myrosinase thioglucoside glucohydrolase EC 3.2.3.1 on the glucosinolates when the plant tissue is injured or mechanically...
Bacteriocins and culture products
Bacteriocins with potential for use in foods are produced by strains of Carnobacterium, Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, and Propionibacterium Montville et al., 2001 Chikindas and Montville, 2002 . Many of these compounds could potentially be used as food antimicrobials but, at the present time, few are approved by regulatory agencies to be added to foods in their purified form. One approach to using these compounds has been to grow bacteriocin-producing starter cultures in...
Lysozyme
Lysozyme is an enzyme that catalyzes hydrolysis of the -1,4 glycosidic bonds between N-acetylmuramic acid and N-acetylglucosamine of the peptidoglycan of bacterial cell walls. It is present in avian eggs, mammalian milk, tears and other secretions , insects and fish. In hypotonic solutions, the enzyme causes lysis of bacterial cells. The enzyme is most active against gram-positive bacteria because the peptidoglycan of the cell wall is more exposed. It inhibits the foodborne bacteria Bacillus...
Antioxidants from oilseeds cereals and grain legumes
Most oilseeds contain tocopherols, which are extracted from seeds with triacylglycerols so they are present in crude oil during oil processing. About a third of the amount originally present is lost during oil refining, mainly deodorization, but synthetic a-tocopherol is sometimes added to refined oils, usually bound as acetate as it is more resistant against oxidation than tocopherol. Corn, soybean and rapeseed oils are particularly rich in 7-tocopherol, contributing to relatively good...
Lactoperoxidase system
Lactoperoxidase is an enzyme that occurs in raw milk, colostrum, saliva and other biological secretions. Bovine milk naturally contains 10 to 60mg of lactoperoxidase per liter Ekstrand, 1994 . This enzyme reacts with thiocyanate SCN in the presence of hydrogen peroxide and forms antimicrobial compound s . This is termed the lactoperoxidase system LPS . Fresh milk contains 1 to 10 mg of thiocyanate per liter, which is not always sufficient to activate the LPS. Hydrogen peroxide, the third...
Natural antioxidants 1
J. Pokorny, Prague Institute of Chemical Technology, Czech Republic Foods containing fats and other lipids, terpenes and branched hydrocarbons are not stable on long storage or intensive heating. Unsaturated, and particularly, polyunsaturated fatty acids bound in lipids are oxidized following different mechanisms with formation of free radicals, which are further converted into hydroperoxides. Hydroperoxides are odourless and tasteless, but they decompose with formation of volatile compounds,...
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 monocytogenes, Micrococcus species, E. coli and Klebsiella species Oram and Reiter, 1968 Korhonen, 1978 Reiter, 1978 Mandel and Ellison, 1985 Payne et al., 1990 . The compound has no activity against Salmonella Typhimurium, Pseudomonas fluorescens...