Preliminary analysis of the lipasi gene (gehM) expression of Staphylococcus xilosus in vitro and during fermentation of naturally fermented sausages (in situ)

Coagulase-negative catalase-positive cocci (CNCPC) play a very important role during the fermentation of sausages. In particular, they are involved in the aroma formation of the final product, because they release lipases that are able to free short-chain fatty acids that are contributing to the sensory characteristics of the fermented sausage. Few studies have been undertaken to elucidate the regulation of lipase gene expression in Staphlococcus xylosus by substrate molecules or products of lipolysis. The aim of this study was to analyze the gehM gene expression of S. xylosus DSMZ 6179 in vitro with growth media containing different concentrations of lipids and in situ during the maturation of fermented sausages. The results obtained suggest that a concentration that increases in triglycerides in the growth medium suppresses the expression of the lipase gen

Effect of TiO2 photocatalytic activity in a HDPE-based food packaging on the structural and microbiological stability of a short-ripened cheese.

A high density polyethylene (HDPE)/calcium carbonate (CaCO3) film containing TiO2 was prepared via blown film extrusion process. The photocatalytic properties of this film were evaluated by voltammetric, UV-Vis spectrophotometric and gas chromatographic measurements following the decomposition rate of suitably selected molecular probes, such as 4-hydroxybenzoic acid and methylene blue. The film containing 1 % w/w of TiO2 displayed a profitable and reproducible photoinduced degradation activity towards target organic compounds. The effect of packaging photocatalytic activity on the structural and microbiological stability of a short ripened cheese was studied. Cheese structure was assessed by dynamic, small deformation rheological tests. A container consisting of a multilayer material, where the layer brought in contact with the food was made by the HDPE+CaCO3+TiO2 composite matrix, was able to perform a greater maintenance of the original cheese structure than a rigid container currently used mainly due to the inhibition of lactic acid bacteria and coliforms