Proteolysis, cheese ripening methods

Contents I. Introduction 168 II. Sampling Techniques 168 III. Compositional Analysis 169 A. Moisture and total solids 169 B. Fat 171 C. Protein 171 D. Ash 172 E. Salt and chloride content 172 F. Acidity and pH 172 G. Calcium and phosphorus 173 IV. Monitoring Cheese Ripening 173 A. Assessment of lactose, lactate, and citrate metabolism 174 B. Assessment of lipolysis 178 C. Assessment of proteolysis 180 D. Assessment of smaller breakdown products 194 V. Novel and Rapid Instrumental Methods 196 VI. Concluding Remarks 200 References 201... 

Formol titration is a method that estimates amino groups by titration with NaOFI and a phenolphthalein indicator (Vakaleris et ah, 1960). Addition of formaldehyde to the neutralized mixture reduces the pFI by making the amino groups less basic. The amount of NaOFI required to retitrate the mixture has been used as an indicator of proteolysis. Another titrimetric method relies on the increase in buffering capacity of the cheese during ripening and has been applied to study proteolysis in Swiss cheese (Lucey et ah, 1993). 

On the assumption that proteolysis is the rate-limiting event in cheese ripening, there has been interest for several years in adding exogenous proteinases to cheese curd. The first problem encountered is the method of enzyme addition. Direct addition of the proteinase to the cheesemilk ensures its uniform distribution throughout the curd but since most proteinases are water-soluble, most of the added enzyme is lost in the whey, which is economically undesirable, and significant proteolysis may occur prior to coagulation with consequent loss of peptides in the whey and a reduction in cheese yield. 

The progress of proteolysis can be followed by electrophoretic and chromatographic methods, e. g., via the peptide pattern obtained with the help of RP-HPLC (Fig. 10.29) and via changes in concentration of individual peptides which correspond to certain casein sequences (Table 10.33) and can serve as an indicator of the degree of cheese ripening. 

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