Five microstructural parameters of goat cheese curd (number of pores, their area and perimeter, strand thickness, and porosity) were studied by scanning electron microscopy and image analysis. Image analysis was used to characterize and quantify differences in all parameters and to provide a procedure for the measurement of strand thickness. The micrographs provided visual evidence of differences in the protein matrix and were quantified by image analysis at 3 production times: 34 ± 1 min (cutting), 154 ± 6 min (before molding), and 293 ± 35 min (after pressing). The data showed that this procedure is an adequate tool for quantifying differences in the parameters analyzed in industrial samples despite their natural heterogeneity. The procedure was reproducible and repetitive for the first 2 production times because no significant intragroup differences were observed. Significant differences were found when comparing the values of the microstructure parameters analyzed at 34 ± 1 min and those corresponding to 154 ± 6 min and 293 ± 35 min, but no significant differences between samples analyzed at 154 ± 6 min and 293 ± 35 min were found. All microstructure parameters analyzed were related at a significance level of at least 95%. This procedure enables the characterization of the microstructure of industrial goat cheese curd.
The aim of this study was to evaluate the effect of feeding goats with distilled and non-distilled thyme leaves (Thymus zygis subsp. gracilis) on the physicochemical composition and technological properties of pasteurised goat milk, and on the physicochemical composition, phenolic content, oxidative stability, microbiology, sensory and texture profile of Murcia al Vino goat cheese. One group of goats was fed the basal diet (control), the second and third groups were fed with different levels of distilled (10 and 20%) or non-distilled (3·75 and 7·5%) thyme leaves. Goat milk physicochemical composition was significantly affected by the substitution of 7·5% of basal goat diet with non-distilled thyme leaves (increase in fat, protein, dry matter and PUFA content), while goat milk clotting time was increased significantly by the introduction of 20% distilled thyme leaves, which reduces its technological suitability. Microbiology, sensory and texture profiles were not affected by the introduction of distilled thyme leaves. The introduction of distilled and non-distilled thyme leaves as an alternative feed to diet can lead to an inhibition of lipids oxidation. The introduction of distilled and non-distilled thyme leaves into goat's diet can be successfully adopted as a strategy to reduce feeding costs and to take advantage of the waste from the production of essential oils, minimising waste removing costs and the environmental impact.
An optical sensor designed to measure whey fat concentration was tested on whey samples from a cheese processing plant. Whey samples were collected to determine syneresis kinetics at different times after gel cutting. Normalized spectral sidescatter intensity was measured by mean of a fiber optic spectrometer (300-1100 nm). A sidescatter waveband ratio (S 875/425) was calculated by dividing intensity at 875 by that at 425 nm. Whey fat concentrations were predicted by using the power low type equation previously developed by the above authors, [Fat] = b 0 ln (b 1 S 875/425 + b 2). Predicted whey fat concentrations were compared to actual concentrations measured by the Gerber method. The change in whey fat concentration with time after gel cutting was used to estimate the syneresis reaction rate. Results confirmed that fat dilution in whey followed a first order response. The light sidescatter technology for determining syneresis kinetics was considered to have potential but requires additional work to improve measurement accuracy.
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