Peroxidase is one of the most, if not the most, heat resistant enzyme found in plant tissues. Guyer and Holmquist (7) summarized data for evaluating the use of high-temperature-short-time sterilization (HTST) principle for canned peas. The times at these temperatures were such that the calculated sterilization values were well above those necessary for sterilization. However, it was noted that off-flavor and odors developed in most samples.Farkes et al. ( 4 ) reported that between 212 and 300' F. (100 to 148.8' C.), the heat inactivation curve for peroxidase in green peas indicated that 6 minutes at 250" F. were required to inactivate the enzyme. Esselen and Anderson (3) found that in the temperature range of 215" to 290" F. (101.6' to 132.2' C.), the degree of heat required to prevent regeneration of peroxidase activity in vegetable tissues was 2 to 4 times greater than that required to destroy the enzyme on the basis of tests made immediately after heating.The present investigation is a continuation of studies carried on in this laboratory on the thermal destruction of peroxidase. E X P E R I M E N T A L P R O C E D U R EA 10-pound portion of fresh green beans was trimmed, cut in one-inch pieces, packed in one-pound polyethylene bags, and frozen overnight. The frozen green beans were then thawed and placed in a Waring blender and comminuted for 5 minutes. The blended green bean puree was strained through 4 layers of cheese cloth. A 15-pound portion of cut and trimmed raw white turnips was frozen overnight and then thawed and sliced. The slices were placed in a Waring blender, mixed with an equal weight of distilled water and blended for 5 minutes. The mixture was strained through 4 layers of cheese cloth.Method of heating. Samples were heated in a thermoresistometer as described by Pffug and Esselen (12) and Esselen and Anderson (3). For operation of the thermoresistometer, at temperatures below 215°F. (101.6"C.), a vacuum pump was connected, Read and Esselen (14), to the side of the stcam chamber of the thermoresistometer. No variation in the temperatures 6f the different pistons was obtained at temperatures as low as 180°F. (822°C.).Quantitative procedure for determination of peroxidase activity. The qualitative test for checking the destruction and survival points of peroxidase in aluminum thermoresistometer cups containing a disc of filter paper (3) is a clear test. However, for quantitative analysis, using the method described by Reddi et al. (15) which is a modification of Hussein and Cruess (S), it was found that when the cup was rinsed several times with water or buffer (pH 6) and the liquid was transferred to a volumetric flask, the enzyme activity measured was very low. Another method was tried in which the paper disc was transferred to a 10 ml. measuring flask containing 2 ml. buffer of pH 6 but the activity was still low and sometimes absent.I n order to overcome this difficulty, the following method was adopted. A thin layer of glass wool was placed on the hottom of the cup instead of the paper dis...

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Effect of ice and cold storage at 4°C on the chemical and technological characteristics of one of red local Egyptian crab (Carcinw meanas) has been studied. Such studies involved the determinations of pH values, moisture, total nitrogen, protein nitrogen, ether extract, acid value, thiobarbituric acid value (TBA) and total bacterial count (TC). It has been found that the shelf life of ice stored crabs was 2 days. Raw crabs stored at 4°C can be kept without any deterioration for 8 days. Dipping of raw crab in 20 ppm chlorotetracycline (CTC) for 20 min raised the keeping period at 4°C up to 11 days. Cooked crabs can be stored at 4°C without any spoilage for 14 days. However, dipping of cooked crabs in 20 ppm of CTC for 20 min increased the keeping period to 17 days.