Bacterial fermentation of meats

Abstract

As with all dead organic matter, muscles from slaughtered animals, as a whole or in particulate form, may be modified by microorganisms during prolonged storage. Environmental conditions and storage time greatly influence the sort and extent of modification. For foods, there can be desirable and undesirable microorganisms, which bring about desirable and less-desirable changes. Desirable modifications are improvements in flavour, aroma, palatability, appearance and storage characteristics. Microbial activities that result in off-odours, strange taste, health- threatening metabolites, colour deterioriation, loss of consistency, and the growth of pathogenic and toxinogenic bacteria generally spoil the food and thus make it unsuitable for human consumption. Changes in microbial abundance, water activity (aw), pH, pO2 and concentration of chemical compounds may be due to real fermentation processes, i.e. incomplete anaerobic oxidations of organic substrates, or to aerobic microbial metabolism. However, it is common to call a food ‘fermented’ if microorganisms, be they truly fermenting or not, or enzymes had contributed significantly to its final characteristics (Campbell-Platt, 1987). Several meat enzymes are known to remain active in dead muscles, e.g. the glycolytic sequence, lipases and proteases. Dead or non-growing microorganisms may release or provide active enzymes, e.g. nitrate reductase and catalase.