Decrease of activity of antioxidant enzymes, lysozyme content, and protein degradation in milk contaminated with heavy metals (cadmium and lead).

The aim of this study was to evaluate the effect of added Cd and Pb to milk on its stability by determining antioxidant enzymatic activities, lysozyme content, and protein degradation. Antioxidant enzymatic activities were spectrophotometrically determined by superoxide dismutase, catalase, xanthine oxidase, and glutathione peroxidase assays; lysozyme was identified and quantified by HPLC-UV analysis, and protein degradation was investigated by spectrophotometric analysis of advanced oxidation protein products (AOPP) and dityrosine content. In this study, contaminated milk samples showed a significant reduction in activity of all studied enzymes compared with control milk. The contamination of milk also led to a significant reduction in the lysozyme content; lysozyme content was decreased about 22% and 18% in Pb milk and Cd milk, respectively, compared with control milk. The presence of the contaminants in the milk resulted in a significant increase of both dityrosine concentration and AOPP compared with the control milk. Moreover, between types of contaminated milk, dityrosine and AOPP values were significantly higher in the Pb milk than in the Cd milk. Therefore, it is important to monitor the presence of these toxic elements in milk for the damage they cause to consumer health both directly due to their ingestion and indirectly due to loss of milk stability.

Effects of genetic type, stage of lactation, and ripening time on Caciocavallo cheese proteolysis.

The objective of this experiment was to evaluate the effects of genetic type, stage of lactation, and ripening time on proteolysis in Caciocavallo cheese. One hundred twenty Caciocavallo cheeses made from the milk of 2 breeds, Italian Brown and Italian Holstein and characterized by different stages of lactation were obtained and ripened for 1, 30, 60, 90, and 150d. Cheese proteolysis was investigated by ripening index (ratio of water-soluble N at pH 4.6 to total protein, %) and by the study of degradation of the protein fractions (αS1-, ß-, and para-κ-casein), which was determined by densitometric analysis of isoelectric focusing results. The statistical analysis showed a significant effect of the studied factors. Ripening index was higher in Italian Brown Caciocavallo cheese and in cheeses made with early lactation milk, whereas casein solubilization was greater in the first 2mo of ripening. Isoelectric focusing analysis of cheese samples during ripening showed extensive hydrolysis of caseins. In particular, the protein fraction that underwent major degradation by proteolytic enzymes was αS1-casein, followed by ß-casein, whereas para-κ-casein was less degraded. Italian Brown cheese showed a lower residual quantity of ß- and para-κ-casein, whereas Italian Holstein cheese showed a lower residual quantity of αS1-casein. In addition, significant interactions of both first and second order were found on both ripening index and degradation of protein fractions. This study demonstrated that the analyzed factors influenced proteolysis of Caciocavallo cheese, which forms the basis of new knowledge that could lead to the production of a pasta filata cheese with specific characteristics.

Effect of genetic type and casein haplotype on antioxidant activity of yogurts during storage.

The aim of this work was to investigate the antioxidant activity of yogurt made from the milk of 2 breeds-Italian Brown and Italian Holstein-characterized by different casein haplotypes (αS1-, ß-, and κ-caseins) during storage up to 15 d. The casein haplotype was determined by isoelectric focusing; antioxidant activity of yogurt was measured using 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid). The statistical analysis showed a significant effect of the studied factors. Antioxidant activity increased during storage of both yogurt types, but yogurt produced with Italian Brown milk showed higher antioxidant activity than those produced with Italian Holstein milk. A high scavenging activity was present in yogurts with the allelic combination of BB-A(2)A(2)-BB. The results of this study suggest that the genetic type and the haplotype make a significant contribution in the production of yogurts with high nutraceutical value.

Processing cereal straws by steam explosion in a pilot plant to enhance digestibility in ruminants.

Wheat, barley and oat straws were treated by steam explosion (SE) and then washed with 50g/l NaOH solution. The SE treatment was optimized at batch scale on the basis of carbohydrate recovery. Stocks of fodder (300kg) were produced at 198 degrees C for 2.5min by a continuous reactor and used for in vivo digestibility tests carried out on sheep. The flow-sheet and the mass balances were obtained for the entire process. For the three straws, the water consumption has been 7.3kg/kg of straw. To delignify and improve the digestibility of the straws, 20g of NaOH/kg straw was used. The yield of fodder, lignin and hemicellulose is dependant on the nature of the starting straw. Delignified fodder (insoluble fraction) can be produced with a yield of 0.64, 0.59, 0.55, respectively, from wheat, barley and oat straw. SE improved the digestibility of the straw by 25%; alkaline washing further increased it by 9%. Balanced rations containing, on a DM basis, 1/4 of treated straw, had digestibility coefficients similar to those of commercial rations based on alfalfa.