Cheeses water extraction procedure

Extraction is an essential step when analyzing solid samples. In some cases homogenization with a solvent suffices, but in others the sample must first be coimninuted. Water, solutions of acetic acid or sodium chloride, or more complex saline solutions are used as solvents. Mixtures of water and methanol or water and ethanol are also employed. The choice of solvent depends on the degree of selectivity desired in the extraction and whether the extraction yield is intended for quantitative analysis. Optimization of the extraction procedure is required in all cases, to fit the nature of the sample to be analyzed and the range of molecular weights of the peptides to be separated. For example, water has been used as the extraction solvent for cheese (33) and legumes (34). Saline solutions have been utilized to extract peptides from meat (35-38) and flour (39,40). Benedito de Barber et al. (41) examined differences in the extractability of amino acids and short peptides in various solvents (1M acetic acid, 70% ethanol, and distilled water) they concluded that extraction with 1M acetic acid yielded the maximum amino acid and peptide contents. 

Most of the methods discussed above have been used with milk but the majority can be applied to other products. Some minor variations in extraction procedures, such as the inclusion of anhydrous sodium sulphate to remove water (Deeth et al., 1983) or inclusion of an aqueous acid wash step to remove lactic acid (Chilliard et al., 1983) may be necessary. Collomb and Spahni (1995) suggested that the above International Dairy Federation reference method could be a universal method if the adaptations made by McNeill et al. (1986) for butter and McNeill and Connolly (1989) for cheese were incorporated. 

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