Characterization of extra-hard cheese produced from donkeys’ and caprine milk mixture

International audienceAbstractCheese cannot be produced solely from equine or donkeys’ milk, because of the unique physico-chemical properties of these milks. The purpose of this study was to characterize a novel dairy product, cheese produced from donkeys’ and caprine milk mixture (60:40% v/v), regarding its chemical, microbiological, textural and sensory properties. Fully ripened cheese was classified as a high-fat, extra-hard cheese, with high sodium (29.97 g.kg−1), magnesium (3.07 g.kg−1) and potassium (4.70 g.kg−1) content. The characterization by lab-on-a-chip electrophoresis revealed lysozyme, α-lactalbumin, immunoglobulins and casein fractions. Palmitic (C16:0) and oleic fatty acids (C18:2 n9-cis) with 25.11 and 24.70%, respectively, were found at the highest concentrations. The medium-chain fatty acids account 18.21% of the total fatty acid content in analysed cheese samples. Escherichia coli, Salmonella spp., Enterobacteriaceae, coagulase-positive staphylococci, Listeria monocytogenes, Bacillus cereus, Clostridium perfringens as well as moulds were under the limit of detection in all analysed samples. After 6 months of cheese ripening (0.94 aw, pH 4.71), total bacterial count, the counts of lactic acid bacteria and yeasts were 6.34 ± 0.03, 4.80 ± 0.10 and 5.81 ± 0.11 log CFU.g−1, respectively. The texture of mature cheese was moderately hard and crumbly. The cheese was described as very salty with strong pronounced creamy, fatty and acidic taste. The characterized donkey/caprine cheese could position this type of cheese as a high-quality functional product, thus having a potential impact on the market

Conductometric method for determining water stability and nutrient leaching of extruded fish feed

Water stability of eight samples of extruded salmon feeds was first determined by applying two gravimetric methods developed by the authors: gravimetric static and wet sieving method. Then, the conductometric method, primarily developed for investigation of nutrient leaching of feed into the water by the authors, was used for each sample. The aim of this study was to evaluate the potential of the conductometric measurement as a technique for determining water stability of extruded fish feed. In order to find any correlation between the results of two gravimetric tests and conductometric method, correlation analysis was employed. The results of static and wet sieving method were expressed as water stability index, which was expressed as the percent of remained dry matter of sample after being disintegrated in the water. The results of conductometric method were shown as conductivity curves for each sample, giving the insight in rate of nutrient leaching during the time. The obtained values of water conductivity showed no significant (p < 0.05) correlation with the results of static water method, while there was a negative significant (p < 0.05) correlation with the results of wet sieving method during first four hours of pellets soaking in water. The highest correlation coefficients were obtained within the first hour of conductivity measurement, demonstrating that proposed conductometric method had a potential to be applied as a rapid and simple method for determination and relative comparison of salmon feed water stability.[ Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III46012 and Grant no. TR31011