Influence of coryneform cultures isolated from the surface of a farmhouse smear-ripened cheese on the ripening of cheddar cheese

Abstract EN

Smear-ripened cheeses are characterized by a layer of yeasts and bacteria on cheese surfaces.

The microbial composition of smear of these cheeses is dominated by salt-tolerant yeasts and Gram-positive bacteria, particularly coryneforms and Staphylococci.

Cheddar cheeses were manufactured using four strains of faculatively anaerobic co-ryneform bacteria (Corynebacterium casei, C.

flavescens, C.

mooreparkense and Microbacterium gubbeenense), these bacteria isolated from the surface of an Irish farmhouse smear-ripened cheese.

Five experimental cheeses (containing isolated cultures in addition to the control cheese) were manufactured in two trials at inoculum levels of 107 cfu / g. In the experimental cheeses, counts of isolated cultures decreased from 107 to 106 cfu / g in two trials, while numbers of starter bacteria decreased from 109 cfu / g to 106-107 cfu / g at the end of ripening, on the other hand non-starter lac-tic acid bacteria started growing after 4 months of ripening and reached105 -106 cfu / g.

Proteolysis during ripening, measured by urea-polyacrylamide gel electrophoresis and levels of water-soluble nitrogen.

The results showed no differences between the control and experimental cheeses in both trials.

However, the experimental cheeses had higher levels of total free amino acids than did their corresponding controls throughout ripening, as well as differences in profiles of individual free amino acids.

Reverse-phase (RP)-HPLC of the 70 ml 100ml-1 ethanol-soluble and -insoluble fractions showed dif-ferences between control cheese and experimental cheeses.

Principal component analysis of chromatographic data from ethanol soluble and insoluble fractions of the cheeses after 4 and 6 months of ripening clearly differentiated between the control and experimental cheeses in first and second batches.