Proteolytic and lipolytic changes during the ripening of León raw cow's milk cheese, a Spanish traditional variety

Proteolytic and lipolytic changes were studied throughout ripening of five batches of León cow's milk cheese, a traditional variety made in the north of Spain. Total soluble nitrogen, non-protein nitrogen, oligopeptides nitrogen, amino nitrogen and ammonia nitrogen fractions increased slightly during the ripening process. The final values of these nitrogen fractions indicate that this cheese undergoes a very slight proteolysis as much in extent as in depth. This weak protein degradation is corroborated when the caseins and their degradation products were quantified by electrophoresis. β-Casein stayed practically intact throughout the ripening process and only 10% of α_s-casein became degraded. The content of total free amino acids increased progressively but in a slightly increased way during ripening, reaching final average values of 592 mg (100 g)⁻¹ of total solids. The most abundant free amino acid at the end of ripening was lysine, followed by leucine, glutamic acid, tryptophan, valine and phenylalanine. The acidity index of the fat values increased during ripening by a factor of 4.39. The final values of this parameter are in the range of those observed in other cow's milk cheeses ripened by bacteria. The content in total free fatty acids underwent an increase throughout ripening reaching final average values of 6669 ppm. The most abundant free fatty acid at the end of ripening was oleic acid followed by butyric and palmitic acids. The high content of short-chain fatty acids is outstanding, specially that of butyric acid.     

Anthocyanin composition of Tempranillo, Garnacha and Cabernet Sauvignon grapes from high- and low-quality vineyards over two years

The anthocyanin composition of Tempranillo, Garnacha and Cabernet Sauvignon grapes over two vintages was studied. Samples were obtained during berry ripening from two vineyards that differed by producing fruit of high and low quality. The proportions of the individual compounds remained practically constant within a single vineyard along the sampling period, the changes in the anthocyanin composition being principally quantitative. Different multivariate statistical methods showed that the anthocyanin profile was primarily determined by variety. This genetic dependence was particularly verified when the sums of the non-acylated glucosides, the acetates and the p-coumaryl derivatives, were analysed. The mean relative content corresponding to these three anthocyanin fractions was always the same within each variety, independently either of the vineyard or the vintage year considered. Relating to the individual compounds, several permanent qualitative differences between vineyards in each variety were also found, although the difference in the total anthocyanin concentration was always much higher.     

Evaluation of the spiral plating method for the enumeration of microorganisms throughout the manufacturing and ripening of a raw goat's milk cheese

A statistical comparison of the spiral plate count (SPLPC) and the standard plate count (SPC) methods for enumeration of microorganisms in raw goat's milk cheese throughout its manufacturing and ripening was carried out. Enumeration of mesophiles, lactic acid bacteria (presumptive lactococci, presumptive leuconostocs, and presumptive lactobacilli), Micrococcaceae, Enterobacteriaceae, and molds and yeasts was carried out for milk, curd, and 2-, 5-, 10-, 17-, and 27-day-old cheeses. Average counts for the SPLPC and SPC methods differed by less than half of a log cycle for all microbial groups studied (range of difference, -0.1386 [mesophiles] to +0.4397 [presumptive lactobacilli]). The results of the SPLPC method compared favorably with the results of the SPC procedure for mesophiles, presumptive lactococci, presumptive leuconostocs, Enterobacteriaceae, and molds and yeasts (the variance between replicate platings was close to 0.005, and correlation coefficients were >0.9). Correlation coefficients were lower for Micrococcaceae (r = 0.824) and presumptive lactobacilli (r = 0.670). Analysis of variance showed that the plating method was a significant factor (P < 0.05) for presumptive lactobacilli counts. In general, results from the SPLPC method compared favorably with results from SPC procedure in the enumeration of microorganisms in goat cheese throughout its manufacturingand ripening processes. However, the suitability of the SPLPC method depends mainly on the microbial group studied.     

Antimicrobial susceptibility of Listeria monocytogenes isolated from food and clinical cases in Navarra, Spain

The susceptibility of 440 Listeria monocytogenes strains isolated from food (n=401) and clinical cases (n=39) between 1995 and 2005 was determined by standard agar dilution and E-test methods. Antimicrobial drugs currently used in veterinary and human therapy were tested, and they included penicillin G, ampicillin, cephalothin, gentamicin, chloramphenicol, tetracycline, doxycycline, trimethoprim, erythromycin, and clindamycin. The sensitivity of strains was established using Clinical and Laboratory Standards Institute (formerly NCCLS) breakpoints and MIC50 (the MIC for 50% of the strains) to MIC90 values. In general, isolates were susceptible to the majority of the antimicrobials tested, including beta-lactamics and aminoglycosides, which are normally used in the treatment of listeriosis. Resistance to tetracycline and doxycycline was found in five strains isolated from fresh trout belonging to the same fish farm. Molecular analysis by restriction endonuclease analysis showed a similar profile, suggesting the persistence of a strain well adapted to the presence of tetracycline in the environment of a fish farm, which is frequently used in aquaculture in order to prevent infections of fish.     

Removal of oligosaccharides in soybean flour and nutritional effects in rats

The objectives of this work were to establish a safe and economically viable process for the removal of raffinose oligosaccharides (RO) from soy flour and compare the effects of RO elimination from diets with regard to nutritional parameters by testing in Wistar rats. Debaryomyces hansenii UFV-1 was cultivated in suspension of defatted soy flour (1:10 w/v). An increase in α-galactosidase activity was observed in the medium, with a consequent decrease in the RO concentration. A total reduction of RO was achieved at 36 h of incubation. The diet containing soy flour free of RO presented higher digestibility, 91.28%, in relation to the diet containing soy flour with RO, 87.14%. However, the removal of the oligosaccharides from the diet did not promote a significant improvement in the values of weight gain, and other nutritional parameters tested on rats, during the experimental period of 14 days.     

Technical note: Antimicrobial susceptibility of Portuguese isolates of Staphylococcus aureus and Staphylococcus epidermidis in subclinical bovine mastitis

To evaluate the antimicrobial resistance traits of staphylococci responsible for subclinical bovine mastitis in Portugal, the minimum inhibitory concentrations (MIC) of 7 antimicrobial agents, frequently administered for mastitis treatment, were determined for 30 Staphylococcus aureus and 31 Staphylococcus epidermidis field isolates. β-Lactamase production was detected through the use of nitrocefin-impregnated discs. The MIC that inhibited 90% of the isolates tested (MIC₉₀) of penicillin, oxacillin, cefazolin, gentamicin, sulfamethoxazole/trimethoprim, oxytetracycline, and enrofloxacin were, respectively, 4, 0.5, 1, 1, 0.25, 0.25, and 0.06 μg/mL for Staph. aureus and ≥64, 8, 1, 32, ≥64, ≥64, and 0.06 μg/mL for Staph. epidermidis. All Staph. aureus isolates showed susceptibility to oxacillin, cefazolin, gentamicin, sulphamethoxazole/trimethoprim, and enrofloxacin. β-Lactamase production was detected in 20 of these isolates (66.7%), all of which were resistant to penicillin. Of the 31 Staph. epidermidis tested, 24 (77.4%) were β-lactamase positive. All isolates were susceptible to both cefazolin and enrofloxacin. Nine Staph. epidermidis isolates were resistant to oxacillin, with MIC values ranging from 4 to 8 μg/mL. The MIC values of 5 antimicrobial agents tested were higher than those reported in other countries. Enrofloxacin was the only exception, showing lower MIC values compared with other reports. Overall, the antimicrobial agents tested in our study, with the exception of penicillin, were active against the 61 isolates studied.     

Effect of slaughter season on fatty acid composition, conjugated linoleic acid isomers and nutritional value of intramuscular fat in Barrosã-PDO veal

This paper describes the influence of slaughter season on lipid content, fatty acid composition, conjugated linoleic acid (CLA) isomeric profile and nutritional value of fat in Barrosã veal from calves reared according to the specifications of the Protected Designation of Origin (PDO). Barrosã purebred calves (n = 27) were raised in a traditional production system and slaughtered in early autumn (October) and late spring (June). Barrosã-PDO veal only presented seasonal differences in the levels of some minor fatty acids and CLA isomers, as well as in the PUFA/SFA ratio. Based on the analysed grass intake indicators, it was shown that veal-PDO has similar values to pasture-fed cattle for both slaughter seasons. From a human nutrition perspective, intramuscular fat in Barrosã-PDO veal has a high nutritional value throughout the year, since CLA contents and the percentages of the c9,t11 isomer are relatively high, and the n − 6/n − 3 ratios are within the recommended values for the human diet.     

The involvement of oxidative stress in ochratoxin A and fumonisin B1 toxicity in rats

The aim of this study was to find out whether very low doses of nephrotoxic and hepatotoxic mycotoxins ochratoxin A (OTA) and fumonisin B1 (FB1) induce oxidative stress in rat kidney and liver and whether their effect is synergistic. Rats were treated orally with OTA (5 ng/kg b.w. and 50 microg/kg b.w.) and FB1 (200 ng/kg b.w. and 50 microg/kg b.w.), or their combinations. Malondialdehyde (MDA) and protein carbonyls (PCs) concentration in kidney was affected with lower dose of OTA than in liver (p<0.05). FB1 did not affect MDA and PCs concentrations in the liver, while in the kidney both FB1 doses increased MDA concentration (p<0.05). The combination of the lower doses of OTA+FB1 increased the MDA and PCs concentration both in the liver and the kidney, compared to controls and animals treated with respective doses of mycotoxins (p<0.05). The combinations of mycotoxins reduced the catalase activity only in the kidney when compared to controls (p<0.05). In contrast to the increased kidney concentrations of MDA and PCs even with very low doses of OTA and FB1, the activity of catalase and SOD does not change. Combinations of OTA+FB1 affected almost all parameters, which indicates their potential to produce oxidative damage.     

Comparative study of the colorants monascus and cochineal used in the preparation of gels made with various gelling agents

The possibilities of using monascus to colour gels were studied by comparing it with cochineal. Gels were prepared with four gelling agents—carrageenan, gellan, gelatine and xanthan—and their colour was measured with a Hunter Lab colorimeter. The equations relating L^* and h with the concentrations of sugar [SU] and colorant [COL] were deduced, and it was found that [COL] had more influence on colour than [SU]. In general, for these four gelling agents the colour of monascus gels is orange-red and the colour of cochineal gels is purplish red. The gels made with xanthan were always the lightest, whether they were made with cochineal or with monascus.