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Ten strains of Pediococcus spp. causing ropiness were isolated from Basque Country spoiled ciders and characterized with regards to growth at different pHs, temperatures, and ethanol and SO2 concentrations. They grew well at pHs above 3.7 and failed to grow at temperatures over 37°C. In addition, they were tolerant to 10% ethanol and to 15, 25, and 50 mg/l total SO2 (pH 3.8). A selected ropy strain was used to carry out plasmid DNA analysis; the agarose gel pattern showed the presence of 6 bands of plasmid DNA. Plasmid-curing experiments with ethidium bromide and novobiocin suggested that the ropy phenotype was encoded by plasmid DNA. In addition, this nonropy strain lost its resistance to oleandomycin after curing trials.

Abstract:The antimicrobial activity against E. coli, St. aureus and A. niger of zinc oxide when blended with polymers has been measured by an applied dynamic method. Two polymers: poly(amide) 6 (PA6) and low density poly(ethylene) (LDPE) have been used as matrix. ZnO nanoparticles content as low as 1% w/w in the polymers showed great antibacterial activity but no antifungal activity. The results of bacterial slaying capability of these nanocomposites was also found to be better when zinc oxide was dispersed in PA6, where the efficiency is similar to pure ZnO particles. The composites have been investigated by means of scanning electron microscope (SEM) and differential scanning calorimeter (DSC).

Ropy strains of heterolactic Lactobacillus spp. were isolated from bottled spoiled ciders produced in the Basque Country. The isolates were able to produce slime experimentally on glucose containing medium and apple must. The production of ropy slime occurred during exponential growth and the increase in viscosity was correlated with production of polysaccharide. They were characterized with regards to growth at different pH, sulfur dioxide (SO2), ethanol and temperatures and showed similar behavior. All ropy strains grew in the presence of high ethanol concentrations (15%) and at low temperatures (10 and 15°C). In addition, these were tolerant to 10, 25 and 50 mg/l of total SO2 (pH 3.8), but with longer lag times as the concentration of SO2, increased. However, the ropy lactobacilli studied were affected by the pH of the medium and in general pH below 3.7 limited their growth seriously.

The evolution of yeasts and lactic acid bacteria was examined during two methods of cider making: the traditional employed unwashed apples of different varieties and the modified used a sole washed acidic apple variety with temperature control during the cider making process. The alcoholic fermentation was carried out mainly by KIoeckeru apiculatu and Sucharomyces cerevisiue species, and their distributions were similar in the two methods. In the traditional, the malolactic fermentation proceeded at the same time as alcoholic fermentation and the "piqiire lactique" occurred. In the modified method, no malolactic fermentation took place. In all musts, a fundamentally heterofermentative lactic flora was found, with Lactobacihs species most abundant in the traditional process.

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This work studied the addition of an adequate lipase to enhance lipolysis reactions and the development of piquant flavour and sharp odour in Idiazabal cheese, as an alternative to the use of lamb rennet paste. Cheeses were manufactured from bulk raw ewes' milk in 50 l vats with commercial bovine rennet and 80 lipase units of pregastric or 180 lipase units of fungal lipase and ripened for 180 days. A higher lipolytic activity was induced by lipase addition promoting strong changes in odour and flavour attributes. Both fungal and pregastric lipases increased the content of total free fatty acids (FFA), but the fungal lipase released mainly medium-and long-chain FFA. In contrast, the pregastric lipase preferably released short-chain FFA. Diglyceride (DG) content was considerably higher in cheeses made with added pregastric lipase compared with those made with fungal lipase or with no lipase. Monoglycerides (MG) were detected only in cheeses made with either lipase added, reaching comparable concentrations after ripening for 180 days. The cheeses made with pregastric lipase had the highest scores for odour and flavour intensity, and sharp and rennet odours, desirable attributes for the Idiazabal cheese made with lamb rennet paste. None of the texture attributes were significantly influenced by the concentrations of MG and DG in the cheeses made with either lipase. Thus, the pregastric lipase was more appropriate than the fungal lipase to develop a more traditionally-flavoured Idiazabal cheese.

The influence of temperature (10°C and 25°C) on the survival and growth of Saccharomyces cerevisiae and Kloeckera apiculata was examined in mixed and pure cultures during fermentation in apple juice. The growth reached by S. cerevisiae did not seem to be affected by temperature and the presence of K. apiculata. However, the growth and survival of K. apiculata, both in single and mixed cultures, were substantially enhanced at 10°C. The highest amount of ethyl acetate was produced by K. apiculata in pure culture at 10°C. Nevertheless, this concentration was lowest when both yeasts were fermented together at 10°C and 25°C.