Botulism challenge studies of a modified atmosphere package for fresh mussels: inoculated pack studies

Seafood spoilage microbiota and associated volatile organic compounds at different storage temperatures and packaging conditions

Seafood comprising of both vertebrate and invertebrate aquatic organisms are nutritious, rich in omega-3 fatty acids, essential vitamins, proteins, minerals and form part of healthy diet. However, despite the health and nutritional benefits, seafood is highly perishable. Spoilage of seafood could be as a result of microbial activity, autolysis or chemical oxidation. Microbial activity constitutes more spoilage than others. Spoilage bacteria are commonly Gram negative and produce off odours and flavours in seafood as a result of their metabolic activities. Storage temperature, handling and packaging conditions affect microbial growth and thus the shelf-life of seafood. Due to the complexity of the microbial communities in seafood, culture dependent methods of detection may not be useful, hence the need for culture independent methods are necessary to understand the diversity of microbiota and spoilage process. Similarly, the volatile organic compounds released by spoilage bacteria are not fully understood in some seafood. This review therefore highlights current knowledge and understanding of seafood spoilage microbiota, volatile organic compounds, effects of storage temperature and packaging conditions on quality of seafood.

Inability of non-proteolytic Clostridium botulinum to grow in mussels inoculated via immersion and packaged in high oxygen atmospheres

A series of botulism challenge studies were conducted to determine if botulinum toxin would be produced in mussels (Mytilus edulis) inoculated with non-proteolytic Clostridium botulinum spores and held under modified atmosphere (MA) packaging conditions at normal (4 °C) and abusive (12 °C) temperatures. Spore mixtures of six strains of non-proteolytic C. botulinum were introduced into live mussels through immersion in a seawater solution with cultured algae. Mussels were packed in a commercial high-oxygen (60-65% O2) MA-package with a buffer, and also packed under a vacuum. Feeding live mussels cultured algae (10(4) cells/ml) with a C. botulinum spore suspension (10(3) spores/ml) in seawater at 4 °C for 6 h resulted in the uptake of spores into mussel tissue (500/g) and the mussel GI tract (100/g). Under all of the experimental conditions evaluated, none of the fresh mussels became toxic, even after spoilage and in the absence of oxygen. However, control samples using tuna or cooked mussel meats became toxic in the absence of oxygen. Botulinum toxin was not produced in fresh mussels packaged under the MA-packaging conditions evaluated, even at an abusive storage temperature (12 °C) for at least 12 days or at normal storage temperate (4 °C) for at least 21 days, which is beyond their shelf life.

Review of the inhibition of biological activities of food-related selected toxins by natural compounds

There is a need to develop food-compatible conditions to alter the structures of fungal, bacterial, and plant toxins, thus transforming toxins to nontoxic molecules. The term 'chemical genetics' has been used to describe this approach. This overview attempts to survey and consolidate the widely scattered literature on the inhibition by natural compounds and plant extracts of the biological (toxicological) activity of the following food-related toxins: aflatoxin B1, fumonisins, and ochratoxin A produced by fungi; cholera toxin produced by Vibrio cholerae bacteria; Shiga toxins produced by E. coli bacteria; staphylococcal enterotoxins produced by Staphylococcus aureus bacteria; ricin produced by seeds of the castor plant Ricinus communis; and the glycoalkaloid α-chaconine synthesized in potato tubers and leaves. The reduction of biological activity has been achieved by one or more of the following approaches: inhibition of the release of the toxin into the environment, especially food; an alteration of the structural integrity of the toxin molecules; changes in the optimum microenvironment, especially pH, for toxin activity; and protection against adverse effects of the toxins in cells, animals, and humans (chemoprevention). The results show that food-compatible and safe compounds with anti-toxin properties can be used to reduce the toxic potential of these toxins. Practical applications and research needs are suggested that may further facilitate reducing the toxic burden of the diet. Researchers are challenged to (a) apply the available methods without adversely affecting the nutritional quality, safety, and sensory attributes of animal feed and human food and (b) educate food producers and processors and the public about available approaches to mitigating the undesirable effects of natural toxins that may present in the diet.