Studies on protein, fat to improve flavor, safety of fermented meats.

The breakdown products of protein and fat are important to product flavor. A better understanding of these components will allow scientists to develop guidelines for improving and standardizing the flavor and safety of fermented meat products. Toward this end, investigators are determining the relative role of muscle and bacterial (starter) enzymes in the hydrolysis and metabolism of protein and fat during the fermentation of meats.

Scientists have evaluated the importance of bacterial and meat enzymes in lipolysis (fat breakdown) and carbonyl production (flavor compounds) during dry sausage ripening. They found that the meat enzymes were more involved in this process than the bacterial lipases. In the case of protein breakdown in fermented sausages, the muscle enzyme cathepsin D, activated by a decline in pH, was responsible for nearly all myosin and actin breakdown. However, up to 70% additional metabolism of peptides to amino acids was achieved by bacterial enzymes.

The production of biogenic amines, such as tyramine and histamine, by more than 30 starter culture bacteria is also under examination, as these amines are highly undesirable in dry sausage. The production of histamine was between 0 mg/ml and 20 mg/ml. Tyramine production is still being evaluated. High-pressure liquid chromatography procedures are being utilized to improve the separation and quantification of the amines.

Model systems are being used to evaluate bacteria strains as producers of volatile flavor components from amino acids. Preliminary results on two strains show specific differences. For example, strain A degrades isoleucine to 2-methylbutanal, and the production of ethanol is stimulated. Strain B gives 2-methylbutanal and 2-methylbutanol from isoleucine. In general, strain B produces more volatile compounds than A and is more active than a commercial starter. Further information. Ir. D. Demeyer, University of Ghent, Department of Animal Production, Proefhoevestraat 10, 9090 Melle, Belgium; phone: [phone]; fax: [phone].