1,721,013 research outputs found
Use of Experimental Design to optimize the performances of the volatile compounds extraction by using dynamic headspace technique followed by TCT/GC
No full textStudy on the effects of supplemental dietary fat on milkfat composition: a chemometrical approach
No full textUse of experimental design to optimize the performances of the volatiles compound extraction by using dynamic headspace techniques followed by TCT/GC
No full textDirectly resistively heated column gas chromatography for the evaluation of cow milk fat purity
No full textCow milk fat purity is currently evaluated by triacylglycerol (TAG) analysis. The method is based on the gas chromatographic analysis of TAG according to their total number of carbon atoms, followed by the application of formulae deriving from multiple linear regressions. The original procedure was set up by using a packed column, but different successive works showed its suitability also with the adoption of more modern adjustments. Recently, the use of high-speed gas chromatography has been spreading. In this work, the suitability of the directly resistively heated-column gas chromatography [Ultrafast module (UFM)-GC] for the evaluation of milk fat purity by the Official EU method was tested. Pure milk fat, together with mixtures of milk fat containing two levels of four foreign fats (coconut fat, sunflower oil, lard and beef tallow), were analyzed by both the conventional capillary GC method and UFM-GC. Sheep, goat and buffalo milk fats were also analyzed. The reference material CRM-519 was used for calibration. Repeatability and reproducibility values were always below the limits reported in the Official method, demonstrating the suitability of UFM-GC for the evaluation of milk fat purity. The investigation on sheep, goat and buffalo milk fat confirmed that the S ranges, calculated for cow milk fat, are not applicable to the evaluation of genuineness of non-bovine milk fats
Lipolisi nel latte di cavalla : valutazione dell’influenza delle basse temperature
No full textThe chemical composition of mare's milk is more similar to human milk than to mammary secretion from other species and it is characterised by interesting nutritional properties. As there's a lack of mare's milk for a human diet and it is difficult to guarantee a continual supply, freezing technologies could be used to preserve the nutritional properties of this product. Samples of mare's milk, obtained from Haflinger breed, were frozen and stored for 60, 120 and 180 days at -20°C and -80°C, to evaluate the effect of the temperature on the activity of lipoprotein lipase (LPL) naturally present in this product. The amount of free fatty acids, monoglycerides and diglycerides was measured. The composition of fatty acids and triglycerides was also determined. The milk stored at -20°C, in the first period of storage, showed a greater amount of monoglycerides, diglycerides and free fatty acids than the milk samples stored at -80°C. During the rest of the storage period lipolysis didn't increase at either the temperatures. It would seem that the reduction of lipolytic phenomena could occur not only by applying low temperatures but also by increasing the speed of the freezing process
Content of conjugated linoleic acid in neutral and polar lipid fractions of milk of different ruminant species
No full textThe aim of this research was to investigate the distribution of conjugated linoleic acid (CLA) in the neutral and polar milk lipid fractions of samples of bovine, ovine and caprine milk. Lipids were fractionated by thin-layer chromatography to obtain triglyceride, diglyceride and monoglyceride fractions. Phospholipids were separated by solid-phase extraction. The CLA content was quantitatively determined after transmethylation and addition of internal standard. As expected, 95-97% of the CLA was found in the triglyceride fraction. The main differences between the species were observed in CLA content of the diglyceride and phospholipid fraction, while the amount of CLA in the monoglycerides fraction was negligible. Cows' milk showed comparable contents of CLA in both diglyceride and phospholipid fractions (4.2 and 5.5 mg 100 g-1 of lipids, respectively). The level of CLA in phospholipids of ewes' (38 mg) and goats' (20 mg) milk lipids was four times higher than the level of CLA in diglycerides (7 and 5 mg, respectively). In terms of the phospholipid content, CLA accounted for 2-4% (calculated as a percentage of total fatty acids esterified in phospholipids) in caprine and ovine and less than 1% in bovine milk
Efficacia della tecnica Ultrafast GC nella valutazione della genuinità del grasso di latte
No full textThe evaluation of the purity of cow milk fat is currently performed by the official EU method, that is based on the gas chromatographic (GC) analysis of triglycerides according to their total number of carbon atoms and the application of formulae deriving from multiple linear regressions. The high-speed GC is one of the recent innovations in the das chromatographic analysis. In this work the GC analysis with ultrafast module and PTV injection system was tested for the evaluation of milk fat purity. The most suitable analytical conditions were set up and then the reference material CRM-519 was analysed for the calibration. Afterwards, two mixtures of cow milk fat with two levels of beef tallow and lard were analysed by both the UFM-GC and the conventional gc technique in use in the laboratory. Lastly, samples of water buffalo, goat and sheep milk fat were analysed as well. UFM-GC technique showed to be a valid and suitable method for the evaluation of cow milk fat purity, meeting the requirements of gas chromatographic separation and repeatability reported in the official method. Moreover, the reproducibility values obtained from the conventional analysis and UFM-GC were always below the limits reported by the law. Finally, the investigation on the milk fats of different species proved the inapplicability of the bovine milk fat s ranges for the evaluation of purity of non bovine milk fat
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