The contribution of microbial ecology to management and monitoring of the safety, quality and acceptability (SQA) of foods

Contribution of Gal- lactic acid bacteria to Saccharomyces cerevisiae metabolic activity in milk

The contemporaneous presence of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus affected the growth kinetics of Saccharomyces cerevisiae PZ2 and the metabolic products of their growth were quantitatively and qualitatively different from those produced by single strains inoculated alone. S. cerevisiae can grow in milk without using lactose or galactose. In particular, the presence of peptides seems to be sufficient to ensure its growth. The growth of S. cerevisiae with lactic acid bacteria is characterised by stimulatory effects that involve both yeast and bacteria. However, the release of galactose by lactic acid bacteria does not seem to be the core metabolic event of these stimulatory effects on S. cerevisiae.

Identification, assessment and management of food-related microbiological hazards: historical, fundamental and psycho-social essentials

Microbiological risk assessment aimed at devising measures of hazard management, should take into account all perceived hazards, including those not empirically identified. It should also recognise that safety cannot be "inspected into" a food. Rather hazard management should be the product of intervention strategies in accordance with the approach made mandatory in the EU Directive 93/43 and the USDA FSIS Pathogen Reduction HACCP system; Final Rule. It is essential too that the inherent variability of the biological attributes affecting food safety is recognised in any risk assessment. The above strategic principles may be conceptualised as a four-step sequence, involving (i) identification and quantification of hazards; (ii) design and codification of longitudinally integrated ("holistic") technological processes and procedures to eliminate, or control growth and metabolism of, pathogenic and toxinogenic organisms; (iii) elaboration of microbiological analytical standard operating procedures, permitting validation of "due diligence" or responsible care, i.e. adherence to adopted intervention strategies. This should be supported by empirically assessed reference ranges, particularly for marker organisms, while the term "zero tolerance" is refined throughout to tolerable safety limit; (iv) when called for, the need to address concerns arising from lay perceptions of risk which may lack scientific foundation. In relation to infectious and toxic hazards in the practical context the following general models for quantitative holistic risk assessment are presented: (i) the first order, basic lethality model; (ii) a second approximation taking into account the amount of food ingested in a given period of time; (iii) a further adjustment accounting for changes in colonization levels during storage and distribution of food commodities and the effects of these on proliferation of pathogens and toxin production by bacteria and moulds. Guidelines are provided to address: (i) unsubstantiated consumer concern over the wholesomeness of foods processed by an innovative procedure; and (ii) reluctance of small food businesses to adopt novel strategies in food safety. Progress here calls for close cooperation with behavioural scientists to ensure that investment in developing measures to contain risk deliver real benefit.

Control of food-borne infections and intoxications

Most food-borne diseases are caused by microorganisms that initially contaminate the living plant or animal or recontaminate the food during handling or processing. Control measures are intended to (1) prevent microorganisms from contaminating food and involve all hygienic production measures (raw material, premises, equipment, cleaning and disinfection, personnel); (2) prevent microorganisms both from growing or forming toxins, e.g. through chilling, freezing or other processes that do not destroy microbes, such as reduction of aw or pH; (3) eliminate microorganisms, e.g. through thermal processing. Integrated systems for control of the microbiology and hygiene of foods aim at a gradual or stepwise reduction of health hazards at all stages of production and processing until final operations. As a further development of HACCP (Hazard Analysis Critical Control Point), other systems such as the LISA (Longitudinally Integrated Safety Assurance) concept, include also the primary stages of harvesting. With respect to food animals, this clearly involves veterinary control of the livestock as an initial stage of food production. As with salmonellosis, the implementation of control systems is helpful in reducing risks at particular critical points. However, isolated measures do not solve the problem as a whole and cannot meet the demands of consumer protection. At least in the case of salmonellosis a global strategy of control is needed which requires political decisions from the relevant public health bodies.