Mould starter cultures for dry sausages-selection, application and effects.

The use of moulds on sausage surfaces can lead to both desirable and undesirable effects. The pursued effects are mainly related to successful production or consumer appeal. The undesirable effects are usually connected to growth of undesirable moulds. Most importantly, moulds may produce highly toxic secondary metabolites and β-lactams. Inoculations of sausages with moulds were traditionally done with the indigenous flora of the processing plants, the so-called houseflora, which was mainly composed of penicillia and aspergilli. The gradual shift in sausage production from small local producers to large-scale factories and increasing awareness of the risks for consumer safety has paved the way for industrialised procution of mould starter cultures. The industrialized starter cultures are carefully selected among hundreds of candidates going through multi-stage concepts including several analytical and biochemical investigations. While the technological aspects of mould inoculations are fairly resolved, its influence on prodution of secondary metabolites is yet emerging. Moulds produce enzymes for the degredation of lipid- and protein-matter, but studies show that the proteolytic and lipolytic capabilities differs significantly both between strains and is highly dependent on media, pH and temperature. Only few studies have addressed the aroma impact of mould growth on sausages, but information from related areas like milk based systems or sausage models still gives a quite clear picture of which components are important and their possible routes of information. One example is that methyl ketones play significant roles in the flavour of Blue cheeses. Here the presence and production of methyl ketones is ascribed to the β-oxidation activities of moulds and therefore investigations in sausages flavour have successfully focused on confirming this relationship and its aroma influence. Sausage producers are interested in using the established knowledge on aroma formation in sausages for improving aroma and texture but also for shortening ripening periods or even expanding shelf life. Addition of concentrates of enzymes have yielded some positive results but it is clear that the use of enzymes as additives in sausages production is not straightforward. To ensure optimal consumer safety starter cultures should be applied to achieve maximal controll over the mould population. Starter strains should under no circumstances show pathogenic or toxigenic signs in neither chemical or biological test. Additionally they should not be able to produce antibiotics.