A comparison of the vitamin C content of vegetable stew when prepared on a large scale in open and pressure cookers.

In the large compound kitchens of the gold mines of the Witwatersrand, where food is prepared for over a quarter of a million Bantu workers, there is a present trend to replace open cooking by pressure cooking. Of the food consumed, the vegetable stew is the chief, and sometimes the sole, source of vitamin C; however, since scurvy occurs infrequently, the amount of the vitamin provided up to now must have been adequate for protection. All the same, it is desirable that any change in the coolung procedure shall not lower the vitamin C content of the stew. A few investigations of the comparison between retention of the vitamin by both methods of cooking have already been reported in the literature, but they were carried out with relatively small quantities of vegetables. In a stew, in which both vegetable and cooking water are consumed, only the total vitamin content is of importance. In this connexion Noble 8c Hanig (1948) showed that, during the cooking of the six vegetables examined, the total amount retained averaged about 80 yo , though it depended more on the kind of vegetable than on the method of cooking. Chappell & Hamilton (1949), who used a popular type of household pressure cooker, found that for the ten vegetables studied the total retention averaged just under 80 % ; the average for the open cooker was about 2 yo higher than for the pressure cooker. In the compound kitchens the scale of cooking is very large, and the nutritional implications of the changeover to pressure cooking may be far reaching; the Chief Medical Officer of the Union Corporation group of mines therefore decided that a direct comparison should be made between the retention occurring (a) when the stew is cooked in the usual manner in the open container, and (b) when it is cooked under pressure in a container identical with those it is proposed to introduce in the future.