J.P. Smith

Spoilage and shelf-life extension of fresh fish and shellfish.

Fresh fish and shellfish are highly perishable products due to their biological composition. Under normal refrigerated storage conditions, the shelf life of these products is limited by enzymatic and microbiological spoilage. However, with increasing consumer demands for fresh products with extended shelf life and increasing energy costs associated with freezing and frozen storage, the fish-processing industry is actively seeking alternative methods of shelf life preservation and marketability of fresh, refrigerated fish and at the same time economizing on energy costs. Additional methods that could fulfill these objectives include chemical decontamination, low-dose irradiation, ultra-high pressure, and modified atmosphere packaging (MAP). This review focuses on the biochemical and microbiological composition of fresh fish/shellfish, the spoilage patterns in these products, factors influencing spoilage, and the combination treatments that can be used in conjunction with refrigeration to extend the shelf life and keeping quality of fresh fish/shellfish. The safety concerns of minimally processed/MAP fish, specifically with respect to the growth of Clostridium botulinum type E, is also addressed.

Aflatoxins in food: Occurrence, biosynthesis, effects on organisms, detection, and methods of control

Aflatoxins are secondary metabolites produced by species of Aspergilli, specifically Aspergillus flavus and Aspergillus parasiticus. These molds are ubiquitous in nature and grow on a variety of substrates, thereby producing aflatoxins. Aflatoxins are of great concern due to their biochemical and biological effects on living organisms. In this article, the occurrence of aflatoxins, their biosynthesis, factors influencing their production, their effects on living organisms, and methods of detection and control in food are reviewed. Future areas of research involving mathematical modeling of factors influencing aflatoxin production and alternative methods of control, such as modified atmosphere packaging, are also discussed.

Shelf life and safety concerns of bakery products--a review.

Bakery products are an important part of a balanced diet and, today, a wide variety of such products can be found on supermarket shelves. This includes unsweetened goods (bread, rolls, buns, crumpets, muffins and bagels), sweet goods (pancakes, doughnuts, waffles and cookies) and filled goods (fruit and meat pies, sausage rolls, pastries, sandwiches, cream cakes, pizza and quiche). However, bakery products, like many processed foods, are subject to physical, chemical and microbiological spoilage. While physical and chemical spoilage limits the shelf life of low and intermediate moisture bakery products, microbiological spoilage by bacteria, yeast and molds is the concern in high moisture products i.e., products with a water activity (a w ) >0.85. Furthermore, several bakery products also have been implicated in foodborne illnesses involving Salmonella spp., Listeria monoctyogenes and Bacillus cereus, while Clostridium botulinum is a concern in high moisture bakery products packaged under modified atmospheres. This extensive review is divided into two parts. Part I focuses on the spoilage concerns of low, intermediate and high moisture bakery products while Part II focuses on the safety concerns of high moisture bakery products only. In both parts, traditional and novel methods of food preservation that can be used by the bakery industry to extend the shelf life and enhance the safety of products are discussed in detail.

Shelf-life extension and microbiological safety of fresh meat. A review

Fresh meat is a highly perishable product due to its biological composition. Under normal, aerobic packaging conditions, the shelf life of refrigerated meat is limited by the growth and biochemical activities of aerobic, psychrotropic strains of bacteria. Additional control methods which can be used to extend the shelf life of fresh meat include modified atmosphere packaging, chemical decontamination prior to packaging and low dose irradiation after packaging. This review focuses on the biochemical and microbiological composition of fresh meat, the spoilage patterns in fresh meat and the combination treatments which can be used by the meat processor to extend the shelf life and keeping quality of meat at refrigerated storage temperatures. The review also addresses safety concerns of MAP/irradiated fresh meat specifically with respect to growth of, and toxin production by C. botulinum types A and B and other pathogens, particularly under mild temperature abuse conditions.

Developments in food packaging technology. Part II. Storage aspects

Abstract The shelf life of many perishable foods, such as meat, eggs, fish, poultry, fruits, vegetables and baked products, is limited in the presence of atmospheric oxygen due to three important factors: the chemical effect of atmospheric oxygen, the growth of aerobic spollage microorganisms and attack by insect pests. Each of these factors, alone or in conjuction with one another, results in changes in colour, flavour and odour, and leads to an overall deterioration in food quality. In Part I of this two-part series, recent developments in packaging technology, with reference to selected processing methods, such as aseptic packaging and packaging innovations related to microwavable foods, were discussed. Part II reviews modified atmosphere packaging (MAP) and sous-vide (vacuum cooking) processing. Both of these preservation techniques are used extensively for the extension of food shelf life in Europe, and are now gaining acceptance as preservation techniques in the USA and Canada.

High pressure (HP) destruction kinetics of Listeria monocytogenes Scott A in raw milk

Abstract Raw milk containing the natural microflora (NM) and an inoculated 24 h culture of Listeria monocytogenes Scott A (10 6 cfuml −1 each) were heat sealed in dual peel sterilization pouches and subjected to high pressure (HP) treatment at 150 to 400 MPa for selected holding times of up to 120 min. HP destruction of NM and L. monocytogenes were evaluated based on first order kinetics, pressure destruction time (PDT) and Arrhenius type models. Results showed a dual effect pressure destruction of microorganisms consisting of (i) an instantaneous pressure kill effect (IPK) with the application of a pressure pulse (no holding time) and (ii) a subsequent first order rate of destruction during the pressure holding time. In general, both IPK and rate constants (k-values) increased with an increase in pressure while the corresponding decimal reduction times (D-values) decreased. The IPK was more pronounced with L. monocytogenes than NM. However, the kinetic parameters indicated a larger pressure resistance for L. monocytogenes . Pressure dependency of kinetic parameters was well described by both pressure destruction time (PDT) and Arrhenius models ( R 2 >0.95). The z p values (PDT) were 266 and 244 MPa and ΔV ≠ (Arrhenius) values were −2.11 and −2.30 × 10 −5 m 3 mol −1 for L. monocytogenes Scott A and NM, respectively.

High-Pressure Destruction Kinetics of Listeria monocytogenes on Pork

Packaged fresh pork chops (30-g samples) containing an indigenous bacterial population of approximately 10(7) CFU/g were inoculated with 10(7) CFU of Listeria monocytogenes Scott A per g, heat sealed, and subjected to high-pressure processing at 200 to 400 MPa for up to 90 min. Total counts and the number of surviving L. monocytogenes cells were determined by a spread plate technique on tryptic soy agar and modified Oxford medium, respectively. The pressure destruction was characterized by a dual-behavior, consisting of a step change in the number of survivors (Pk0) with the application of a pressure pulse and a first-order rate drop in the number of survivors during the pressure hold period. Higher pressures resulted in higher rates of microbial inactivation, as indicated by their associated lower D values (and higher k values). The pressure sensitivities of the kinetic parameters were evaluated on the basis of Arrhenius and pressure death time (PDT)-type models. The results suggested that L. monocytogenes was more resistant to pressure inactivation than the indigenous microflora (the volume change of activation, deltaV* [Arrhenius model]), and Zp values (PDT model) were -4.17 x 10(-5) m3 mole(-1) and 134 MPa for indigenous microflora and -3.43 x 10(-5) m3 mole(-1) and 163 MPa for L. monocytogenes respectively.

Shelf life extension of a bakery product using ethanol vapor

Studies to determine the effect of ethanol vapor on growth of Saccharomyces cerevisiae , the spoilage isolate of gas packaged apple turnovers were undertaken. Ethanol vapor was generated from a commercially available preparation Ethicap which releases a controlled amount of ethanol vapor into package headspace. The effectiveness of ethanol vapor against S. cerevisiae in an agar model system was a function of a w of test medium and concentration of ethanol vapor. While a reduction of a w alone failed to inhibit growth of S. cevevisiae , growth was completely suppressed at a w 0·9 and 1·52% (v/v) ethanol vapor and at a w 0·85 and 0·56% or 1·1% ethanol vapor. Apple turnovers, with a w of 0·93 and pH of 5 had a shelf life of 14 d when packaged in air or a CO 2 : N 2 (60 : 40) gas mixture and stored at ambient temperature. Packages were visibly swollen due to growth of S. cerevisiae and additional CO 2 production. However, when Ethicap was incorporated into packaged product, yeast growth was completely suppressed and all packages appeared normal at the end of the 21d storage period. This study has demonstrated the usefulness of ethanol vapor for shelf life extension of a fruit filled bakery product.

A hazard analysis critical control point approach (HACCP) to ensure the microbiological safety of sous vide processed meat/pasta product

Abstract Increasing consumer demands for microwaveable, convenience foods with extended shelf life yet retaining ‘closer to fresh’ characteristics, has resulted in the growth of sous vide or vacuum cooking processing technology. However, this new generation of minimally processed sous vide products are not shelf stable and pose a potential public health risk if subjected to temperature abuse at any stage of the products production, storage, distribution and marketing. To ensure the microbiological safety of sous vide products, a Hazard Analysis Critical Control Point (HACCP) approach is recommended at all stages of sous vide processing and distribution of end product. The HACCP approach is a preventive approach to microbiological quality control and is intended to prevent problems before they occur rather than finding them in the finished product. Hazard Analysis identifies the microbiological hazards and potential entry points of these hazards in the sous vide process. Critical Control Points to control the identified microbiological hazards include quality of raw ingredients, time/temperature relationship, sanitation and packaging control and incorporation of additional barriers, such as pH and water activity (aω) reduction, in the formulated product. The practical application of HACCP to ensure the microbiological safety of a sous vide processed meat/pasta product are given.

Inactivation of Escherichia Coli O157:H7 in Liquid Dialyzed Egg Using Pulsed Electric Fields

Pulsed electric field (PEF) pasteurization may be used either to replace or supplement conventional processing of heat-sensitive products such as liquid egg. The objective of this study was to investigate inactivation characteristics of Escherichia coli O157:H7 in liquid egg products at low temperature using square waveform pulsed electric fields. Dialyzed liquid egg products, namely whole egg, egg white and egg yolk, were exposed to an electric field of lSkVcm −1 at a low temperature of 0°C. The square voltage fields were generated across parallel plate treatment chambers. A pulse frequency of 1 Hz was used. Up to 500 pulses were applied. Product temperature during the PEF treatment was controlled using a water cooling system. About 1, 3 and 3.5 log reductions were obtained for the dialyzed egg white, egg yolk and whole egg products, respectively. The results showed that microbial inactivation rate increased with increasing number of pulses, especially for the egg yolk and whole egg products. The inactivation kinetics was exponential with some tailing. A new kinetic model for the bacteria inactivation was proposed.