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-oven1 on vitamin content of chicken, lamb chops, fish, cassava, taro and palusami 2 were 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%).