Physicochemical characterization and sensory evaluation of yogurts incorporated with beta-carotene-loaded solid lipid microparticles stabilized with hydrolyzed soy protein isolate

Food Science and Biotechnology - Beta-carotene is an extremely interesting bioactive compound in the food industry due to its antioxidant capacity and pro-vitamin A activity. However, its...     

Use of serial ultrasound measures in the study of growth- and breed-related changes of ultrasonic measurements and relationship with carcass measurements in lean cattle breeds

The growth and breed-related changes of rib and rump characteristics in lean beef cattle and the ability of ultrasound to predict carcass traits were investigated. Three hundred bulls from three breeds were scanned monthly (6–7 times) using real-time ultrasound with final scans taken < 7 days prior to harvest. The rib and rump ultrasound measurements, except intramuscular fat content, increased (P < 0.05) with live weight. Breed affected most of traits. The 12th rib ultrasound measurements showed a weak to high positive correlation (0.131 to 0.976, P > 0.05 to P < 0.001) with 12th rib measurements in the carcass. Regression equations developed with the ultrasound measurements, explained 97% of the variation in longissimus muscle area, 88% of the variation in fat thickness and 57% of the variation in intramuscular fat content. When last ultrasound scan measurements were excluded from prediction equations, the R² significantly decreased. Ultrasound measures “in vivo” are viable options for assessing carcass attributes of lean cattle.     

Accuracy of BRT and Delvotest microbial inhibition tests as affected by composition of ewe's milk

The presence of drug residues in ewe's milk samples can be determined by microbial assays. The main limitation of these tests is the large number of false-positive results associated with them. False-positive results can be explained by the interaction of certain substances naturally existing in ewe's milk with the growth of the microorganism used in the test. In this study, milk chemical composition (fat, protein, lactose, total solids), somatic cell counts (SCCs), free fatty acid concentrations, and lactoperoxidase system components were determined in order to investigate their influence on the rate of false-positive results for the BRT and Delvotest microbiological inhibitor tests. Milk samples were obtained after morning milking of Manchega ewes at 15, 30, 45, 60, 75, 90, 105, 120, and 135 days after parturition. The animals did not receive any kind of treatment or medicated feed throughout the experiment. The false-positive rates for BRT and Delvotest were 3.75 and 2.4%, respectively. When the logistic regression model was applied, the percentages of total solids for positive samples were significantly different from those for negative samples (16.90 versus 18.42% for BRT, 16.05 versus 18.45% for Delvotest), while the SCC logarithmic transformation was significantly higher for the positive samples than for the negative samples (5.38 versus 5.11 log units for BRT, 5.32 versus 5.11 log units for Delvotest). Moreover, Delvotest-positive samples exhibited thiocyanate concentrations higher than those of Delvotest-negative samples (8.18 mg/liter versus 6.85 mg/liter). Further analyses are needed to confirm the possible presence of antimicrobial residues in this particular type of milk sample.     

Heat treatment effects on the antimicrobial activity of macrolide and lincosamide antibiotics in milk

Antibiotic residues in milk can cause serious problems for consumers and the dairy industry. Heat treatment of milk may diminish the antimicrobial activity of these antibiotic residues. This study analyzed the effect of milk processing (60 °C for 30 min, 120 °C for 20 min, and 140 °C for 10 s) on the antimicrobial activity of milk samples fortified with three concentrations of three macrolides (erythromycin: 20, 40 and 80 μg/liter; spiramycin: 100, 200, and 400 μg/liter; and tylosin: 500, 1,000, and 2,000 μg/liter) and one lincosamide (lincomycin: 1,000, 2,000, and 4,000 μg/liter). To measure the loss of antimicrobial activity, a bioassay based on the growth inhibition of Micrococcus luteus was done. The data were analyzed using a multiple linear regression model. The results indicate that treatment at 120 °C for 20 min produces inactivation percentages of 93% (erythromycin), 64% (spiramycin), 51% (tylosin), and 5% (lincomycin), while treatment at 140 °C for 10 s results in generally lower percentages (30% erythromycin, 35% spiramycin, 12% tylosin, and 5% lincomycin). The lowest loss or lowest reduction of antimicrobial activity (21% erythromycin and 13% spiramycin) was obtained by treatment at 60 °C for 30 min.     

Immunoreactivity of hen egg allergens: Influence on in vitro gastrointestinal digestion of the presence of other egg white proteins and of egg yolk

Hen egg white comprises of a complex mixture of proteins, which greatly differ in their physicochemical characteristics and relative abundance. We aimed to identify potential undiscovered egg allergens within the egg white proteome and investigated the existence of matrix effects on the proteolytic stability and resultant IgE-binding of the allergenic proteins. In addition to the main egg allergens: ovalbumin (OVA), ovomucoid (OM) and lysozyme (LYS), two minor egg white proteins, tentatively identified as ovoinhibitor and clusterin, were found to react with serum IgE from egg-allergic patients. Egg white exhibited residual immunoreactivity after gastrointestinal digestion due to the presence of intact OVA and LYS, as well as of several IgE-binding peptides derived from OVA. The presence of egg yolk slightly increased the susceptibility to hydrolysis of egg white proteins and abrogated bile salt-induced precipitation of LYS in the duodenal medium. However, the resultant immunoreactivity against IgE of egg white proteins after in vitro digestion was not significantly modified by the presence of yolk components.     

Effects of cone opening, initial moisture content and multiple extrusion on the protein quality of extruded soybean using the Brady Crop Cooker

In the present study, three cone openings (0.133; 0.106, and 0.080 cm) and three initial moisture content values (9%, 15% and 21%) were used as treatments to evaluate their effects on the protein quality of full-fat soybean flour, extruded in the Brady Crop Cooker. The specific volume, protein and oil contents as well as available lysine content characteristic of the final product, were not affected by the treatments used. Processing temperatures, however, decreased when the initial moisture content of the material was increased. The nitrogen solubility index was affected by the cone opening but not by the moisture content of the material. With respect to the trypsin inhibitors content, the increase in the initial moisture content in soybeans gave conflicting results. At the 21% moisture treatment, the amounts of trypsin inhibitors were higher than those present in the raw material; a similar effect was also observed with urease activity. At the other two moisture contents (9 and 15%) the amounts of trypsin inhibitors and urease activity were decreased by heat treatment, mainly at the 9% moisture level, which were related to the cone opening of the extruder. PER values in rats were influenced by the moisture content and were not affected by the cone opening. Results obtained in the biological assays with chicks, both for weight gain and conversion efficiency, were favored by a decrease in cone opening. Nevertheless, the increase in the moisture content induced a decrease in weight gain at the 5- and 8-week periods, without affecting the conversion efficiency. The effect of consecutive passes of the material through the extruder was also studied. The product obtained with two extrusions presented a good biological value, probably as a consequence of the low values in the trypsin inhibitors and urease activities. When the material was extruded three times, results proved to be poor, due to a reduction to significant low levels of available lysine content--which becomes limiting--, and nitrogen solubility index of the full-fat soybean flour.