Rubén Oliszewski

Conjugated linoleic acid conversion by dairy bacteria cultured in MRS broth and buffalo milk

Aims:  To evaluate strains of Lactobacilli, Bifidobacteria and Streptococci for their ability to produce conjugated linoleic acid (CLA) from free linoleic acid (LA).

Influence of autochthonous adjunct cultures on ripening parameters of Argentinean goat's milk cheeses.

BACKGROUND Argentinean semi-hard goats cheeses manufactured with and without the addition of autochthonous adjunct cultures of Lactobacillus plantarum ETC17, Lactobacillus rhamnosus ETC14 and Enterococcus faecium ETC3 were analysed to evaluate the effect of these strains on ripening parameters. RESULTS Gross composition was similar among cheeses. Microbiological analysis indicated that lactic acid bacteria added to cheeses reached high levels. None of the strains assayed affected the primary proteolysis. Overall, E. faecium had a clearer effect on the peptide and lipolysis profiles of cheeses. Analysis of the volatile fraction of cheeses indicated that the levels of several compounds involved in the overall flavour of goats cheeses were affected by the presence of E. faecium. This could explain the differences detected in the global perception of cheeses made with this strain compared with control cheeses. CONCLUSION The present work represents a first contribution to knowledge of the ripening process of Argentinean goats cheeses made with the addition of autochthonous adjunct cultures. The results suggest that E. faecium ETC3 showed a significant effect during ripening, which was reflected both in the profiles of proteolysis, lipolysis and volatile compounds and in the global sensory perception of cheeses.

Assessment of beta-Glucuronidase Levels in Goat's Milk as an Indicator of Mastitis: Comparison with Other Mastitis Detection Methods

The use of somatic cell counts (SCCs) for the diagnosis of mastitis is not a well-established procedure for the caprine species, because nonleucocytic cell-like particles are normally observed as a result of the apocrine secretion process of the goat mammary gland. The infection levels of 124 goats were measured by the beta-glucuronidase test, which was compared with the SCC method and the California mastitis test (CMT). Seventy-nine of 124 samples (63.7%) showed SCCs lower than 1.3 x 10(3) cells per ml. Of these samples, 93% showed low levels of beta-glucuronidase activity (< 15 U/ml). In the remaining 36.3% of the samples, SCCs were higher than 1.3 x 10(3) cells per ml. Of these samples, 88% showed high levels of beta-glucuronidase activity (15 to 100 U/ml). The CMT gave similar results. In this study, the beta-glucuronidase test was standardized for goat milk and shown to be reliable, enabling one to count only the somatic enzyme cells in milk and avoiding the interference encountered with the SCC method.

β-Glucuronidase Method to Determine Mastitis Levels in Goat Milk

Mastitis is a general term that refers to the inflammation of the mammary gland. It is the most common illness in dairy farms and it has different causes, mainly a great number of germs that infect the gland. These infectious diseases induce gross variations in milk composition, reflected by physical, chemical, and bacteriological changes. They produce milk jellification, a decrease in important components such as lactose, casein, and fats and minerals such as calcium, phosphorus, and potassium and increases in other unimportant technological components, such as serum proteins and chlorides; all these affect the cheese efficiency and the starter culture action. Assuming that cheese making is the principal use of goat milk in industry, an evaluation of the quality of the milk used as the raw material is of fundamental importance. It is impossible to obtain quality products by using milk with an anomalous chemical composition. Somatic cell count (SCC) is the indicator most used for mastitis detection. These cells, which are contained in milk, can be grouped into three types: epithelial cells, blood cells, and cytoplasmatic particles. During an attack of mastitis, the immune defenses of the udder are activated, polynucleated leukocytes pass from the blood toward the mammary gland in large numbers, and the number of somatic cells in the milk increases. The level of somatic cells in goat milk is characterized by great variability between different countries and between regions of the same country. Different authors show averages between 750,000 and 5,400,000 cells/mL. These values differ greatly between cow and goat milk, mainly because normally nonleukocytic cell-like particles can be found as a result of the particular apocrine secretion process in the goat mammary gland. These particles are large fragments of cytoplasm originating from the distal portion of alveolar secretory cells and are of similar size (5-30 microm in diameter) to milk leukocytes. They contain abundant RNA-positive granular material (associated with dilated cisternae of the rough endoplasmic reticulum), large amounts of protein, and some lipids, but no DNA. Thus it is important to use techniques that disregard these other substances and allow only a count of somatic cells.