Rennet analysis

FIG. 12 Principal component analysis similarity map defined by the principal components 1 and 2 for vitamin A excitation fluorescence spectral data. Sample coding L, R, and X stand for the GDL, rennet, and mixed systems, respectively the digits are for the time elapsed since the beginning of the kinetics. 

Dwyer, C., Donnelly, L., and Buckin, V. (2005). Ultrasonic analysis of rennet-induced pregelation and gelation processes in milk. J. Dairy Res. 72, 303-310. 

Visser, F. M. W. (1977c). Contribution of enzymes from rennet, starter baaeria and milk to proteolysis and flavour development in Gouda cheese. 3. Protein breakdown analysis of the soluble nitrogen and amino acid fractions, Neth. Milk Dairy J. 31,210-239. 

W. Sawlajow suggests for the analysis of rennet a special apparatus which ves an accurate determination of the moment of coagulation of milk. Milk, treated with rennet, flows through capillary tubes at constant temperature. At the moment of coagulation, the outflow of droplets is checked. 

The method of Blum and Fuld is especially recommended for the determination of the coagulating power of gastric juice. A normal gastric juice requires, for analysis, a dilution of between 3000 and 7000. There are very rich juices which require dilutions higher than 7000, and juices are also met which are so poor in rennet that their content is below 100. 

For some years we have had at otu disposal, for the analysis of peptonizing and coagulating enzymes, the much more delicate methods that have already been described in preceding chapters. These are for pepsin, the Fuld method, with edestin (p. 253), and that of Jacoby, with ridn (p. 255) for rennet, the method... 

Binary mixtures of bovine and ovine or bovine and caprine raw milks containing 5, 10, 20, 30, 50, 75, and 95% (v/v) of bovine milk as well as ovine and caprine milk mixtures containing 5, 10, 20, 30, 50, 75, and 95% (v/v) of ovine milk were used for cheesemaking. Cheeses were prepared with rennet whey and ripened for 4 weeks. MUk mixtures and fresh and ripened cheeses were analyzed. The whey protein fractions were obtained from the cheese samples (5 g) by extraction with water (15 ml), in a sonicator prior to centrifugation (4000 rpm, 10 min), or from 15 ml of skimmed milk. The supernatant was precipitated by addition of 1 M HCl untU pH 4.6. After centrifugation (4000 rpm, 10 min), the resultant supernatant was filtered prior to HPLC analysis. All the samples were stored at 4°C. 

The lipoproteic matrix was prepared by mixing water (63% w/w), milk powder (29.6%) and anhydrous fatty matter (7.4%) in a blender. The pH was adjusted to 6.20 by an addition of 8-glucono-lactone. Once that pH reached, the coagulation was activated by an addition of rennet. After 3h at 32°C, the preparation was kept at 4°C before NMR analysis. The water/milk powder ratio in the lipoproteic matrix equals 68/32. 

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