Influence of pasteurization,brining conditions and production environment on the microbiota of artisan Gouda-type cheeses

To monitor the effect of the indigenous milk microbiota and of technological and environmental parameters on the microbiota established in ripened cheese, the diversity and dynamics of the predominant microbial communities in artisan Gouda-type cheeses produced under different conditions was studied. A total of 22 cheese types differing in milk source, milk treatment, production environment and brining conditions were analyzed by PCR-denaturing gradient gel electrophoresis (PCR-DGGE) using total DNA extracts as well as DNA extracted from culturable fractions. Through band position analysis and band sequencing, the majority of DGGE bands could be attributed to lactic acid bacteria (LAB), although a few bands also belonged to staphylococci and gamma-Proteobacteria. Aided by principal component analysis (PCA) and multivariate analysis of variance (MANOVA), cheeses produced at different locations could clearly be differentiated. The same approach also allowed to distinguish raw and pasteurized milk cheeses, the former showing a more diverse microbiota in terms of a higher species richness and number of DGGE bands. No substantial differences were found between cheeses brined at two different locations. In conclusion, the combined PCR-DGGE approach relying on both total DNA extracts and culturable fractions proved its value for analyzing the effect of technological and environmental parameters on the diversity and dynamics of the microbiota in Gouda-type cheeses.     

Species diversity and metabolic impact of the microbiota are low in spontaneously acidified Belgian sausages with an added starter culture of Staphylococcus carnosus

Quality of fermented sausages is affected by acidifying lactic acid bacteria (LAB) and colour- and flavour-promoting coagulase-negative staphylococci (CNS), whether or not used as starter culture. Artisan fermented sausages are often perceived as superior to industrial variants, partially because of the specific microbiota due to spontaneous acidification, which may be considered as an artisan characteristic. Therefore, two kinds of spontaneously acidified Belgian sausages were prepared (Belgian-type salami and Boulogne sausage), but with addition of a Staphylococcus carnosus culture. The Belgian-type salami was made from pork and beef, whereas the Boulogne sausage contained pork and horse meat. In all cases, Lactobacillus sakei was the dominant LAB species present on the raw materials and during fermentation, whereas enterococci remained present in the background. Enterobacteriaceae vanished after fermentation. The CNS species diversity on the raw materials was large and differed between the pork, beef, and horse meat. Nevertheless, this species diversity was annihilated during fermentation by the added S. carnosus culture. The volatiles fraction was mainly composed of aldehydes that originated from lipid oxidation and spices-derived compounds. Aromatic compounds that are typically associated to CNS activity, such as end-products from the metabolism of branched-chain amino acids, were not present in the Belgian-type salami and only marginally present in the Boulogne sausage. In conclusion, spontaneous acidification of Belgian-type fermented sausages leads to dominance of L. sakei and is no guarantee for bacterial contribution to the aroma profile when S. carnosus is added as a starter culture.     

Screening of native S. cerevisiae strains in the production of Pajarete wine: a tradition of Atacama Region,Chile

Pajarete is a Chilean wine with an appellation of origin. Although it has organoleptic properties, intensive utilization of Saccharomyces cerevisiae commercial yeast through the years has presumably produced the loss of native strains that may be associated with Pajarete oenologic uniqueness. In order to evaluate the effect of re-incorporation of indigenous strains into Pajarete winemaking, native S. cerevisiae strains were isolated and selected based on their properties shown during small and large laboratory scale fermentation, and then evaluated in industrial bioreactors. From an initial set of 312 isolates, a single native strain was selected based on taxonomy, fermentation performance, aroma, residual sugars, and production of alcohol for incorporation into market scale.     

Biochemical and microbiological characterization of artisan kid rennet extracts used for Cabrales cheese manufacture

Four samples of artisanal kid rennet extracts from four different Cabrales cheese producers were biochemically and microbiologically characterized. Most samples had a very acidic pH (around pH 4.0), which may condition their biochemical and microbial variables. The milk-clotting activity of the extracts was assessed using a Formagraph apparatus. The properties of these artisanal rennets were found to be comparable to a 1/10 dilution of 1:10,000 commercial calf rennet; their enzymatic potentials, measured with a semi-quantitative commercial system (API ZYM), showed only very slight differences. A large population of lactobacilli was found in all artisanal kid rennet samples, whereas coliforms, enterococci, staphylococci and leuconostocs were only occasionally encountered. Sixty-four representative colonies were classified by PCR amplification and the sequencing of a stretch of their 16S rDNA genes. Strains of Lactobacillus plantarum completely dominated one of the extracts. In all others samples, strains of this homofermentative species and of the heterofermentative Lactobacillus brevis were present in similar amounts.     

职业技术教育需要培养过硬的动画“匠人”

动画职业技术教育需要在培养专业技术上下功夫,扎实技术。社会需要大量的技术人才而不是创作人才,创作在学会、学好技术之后自然就会向前发展。     

Microbial, chemical and sensorial variables of the Spanish traditional blue-veined Cabrales cheese, as affected by inoculation with commercial Penicillium roqueforti spores

This paper reports the technological effects of inoculating Cabrales cheese (a traditional, Spanish, blue-veined cheese) with Penicillium roqueforti spores. Three batches of inoculated Cabrales cheese were manufactured and a number of their microbial and biochemical variables recorded. The results were compared with those obtained for three batches of control cheese made using traditional technology (i.e., adding neither starter cultures nor fungal spores). Although mould and yeast populations grew more quickly in the inoculated cheeses, their normally dominant and representative microbial populations were not affected neither was their gross biochemical composition changed. The variations observed were thought to be caused by the uncontrolled environmental conditions of manufacture and ripening. The development of free amino acids and volatile compounds was significantly increased at 30 days in the inoculated cheeses, although the values for both types of cheese were almost identical at 90 days. The inoculated cheeses obtained higher scores in a hedonistic sensorial evaluation. Thus, inoculation improved the standardization and quality of the cheese.