Nutrient retention in foods after earth-oven cooking compared to other forms of domestic cooking: 2. Vitamins

Effects of Pacific traditional style of cooking in an earth-oven11Traditional Pacific style of cooking, lovo as it is known in Fijian, is performed in an oven in the earth prepared by digging a smooth sloping pit on the ground. The main source of heat is provided by the stones (once or twice the size of a fist), heated in an open fire (normally 1–2 h) until extremely hot. All food to be cooked is put in the pit at once on these extremely hot and dry stones (without water being poured to generate steam for cooking) and left in the pit, covered with earth, and left to cook for 1–2 h (1 h and 15 min in this research). tamin content of chicken, lamb chops, fish, cassava, taro and palusami22A vegetable-based dish that consists of a filling, made by mixing canned meat (fish, mutton or beef) with coconut cream, wrapped by a layer of taro leaves. Depending on the taste and likings of people, onion, chilies, carrot, tomatoes and salt are also added to the filling. investigated. Retention of vitamins (retinol, β-carotenes, thiamin, riboflavin, niacin and ascorbic acid) in earth-oven cooked samples was compared with the retention in microwaved and oven-roasted chicken and lamb chops, microwave-cooked fish, boiled cassava and taro, and steamed cooked palusami, the nutrient analyses of all of which were conducted during the course of this study. Retention of retinol ranged from 20% to 91% for all cooked samples. Generally higher retention of this vitamin was observed in microwave cooked samples whereas the lowest retentions were characteristic of earth-oven cooked samples. Retention of more than 100% was observed for β-carotenes in cooked palusami. There was low retention of thiamin and riboflavin in most samples, with thiamin generally showing lower retention levels. Highest losses were usually observed with oven roasting, slightly more than the losses with earth-oven cooking. Microwave cooking caused the least loss of these two B vitamins. Niacin was quite stable to all the cooking methods with the retentions ranging from 63% to 95%. Retention values were comparable between similar samples cooked by different methods. Steam cooking was most detrimental to ascorbic acid in palusami. It caused a total loss of ascorbic acid from palusami upon cooking compared to earth-oven cooking after which 62% was retained in the palusami. Most ascorbic acid was retained in earth-oven cooked cassava (76%).