The enzyme concentration found was independent of the weight of sample taken for color development; therefore, there are no heatstable compounds in whole-kernel corn that may lead to an error in the assay. '(2) Esselen.
To clarify the nature of muscle proteases, an atiempt was made to concentrate and purify the proteolytic enzymes in beef muscle. Purification of enzyme fractions was achieved by the preliminary use of ammonium sulfate, followed by dialysis and chromatography on diethylaminoethanol-modified cellulose. A purified enzyme preparation having an 1 8fold increase in specific activity, based on nitrogen content, was obtained. An over-all assay procedure for screening fractions was developed, employing hemoglobin in 3M urea as a substrate.The assay reaction was carried out at pH 4.4 at 37°C. for 4 hours, and the extent of proteolytic action was determined from the amount of tyrosine produced in the protein-free supernatant.
Irradiation of certain meat products produces characteristic objectionable flavors and odors. It has been assumed that the objectionable flavors are due to certain chemical changes, and a number of workers (2,3,6,8,13) have reported values for various chemical components both before and after irradiation. Recently it has been shown that the level of hydrogen sulfide, methyl mercaptan and carbonyls appear to be closely associated with the poor acceptability of irradiated beef, pork and veal (10). However, data are not available in the literature showing the influence of temperature and length of storage upon either the chemical components or panel scores.Consequently, this study was designed to ascertain the effects of length and temperature of storage upon panel scores, carbonyl compounds, hydrogen sulfide, methyl mercaptan, total glutathione, reduced glutathione and the pH of precooked irradiated meats. E X P E R I M E N T A L P R O C E D U R E Preparation and irradiation. The beef, pork and veal were prepared, cooked and irradiated at either 1.86 X 10 6 rads or 2.79 X 10 0 rads as described in a previous publication (10).All samples irradiated at 1.86 X 106 rads were stored at 2" C. in order to prevent the growth of botulinum organisms. The samples irradiated at the higher level (2.79 X 10 6 rads) were stored at 2" C. and 24" C. for the beef and at 2" C., 24" C. and 38" C. for both pork and veal. Storage for both panel and chemical testing was for 0, 1,3 and 6 months. At each of these storage periods, duplicate samples were removed and one was used for taste panel evaluation while the other was used for chemical determinations. Additional samples were available for panel ratings but not for chemical analysis at 12 months for beef and at 9 months for pork.Samples were prepared and presented to a consumer type panel of 18 judges, who rated the samples on the 9-point hedonic scale (12). Although some judges Storage.Panel ratings.
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