Retention of Xanthophylls in Green Foliar Vegetables after Different Food Preparations

Green leafy vegetables (GLV) are rich sources of micronutrients, which have many health benefits and have the potential to combat the problem of malnutrition. However, domestic processing and cooking alter the nutrient contents. To study the retention of xanthophylls after processing, ten different GLV which are commonly available and regularly consumed, were analysed for total carotenoids, lutein, zeaxanthin and violaxanthin in both raw and cooked forms. In the unprocessed GLV, the lutein content on dry basis ranged from 341 mg/kg in Murraya koenigii to 959 mg/kg in Spinacia oleracea while zeaxanthin ranged from traces in Coriandrum sativum and Rumex acetosa to 15.45 mg/kg in Basella alba. In the case of violaxanthin, while it was not detectable in Hibiscus cannabinus, Amaranthus viridis had 794 mg/kg. The total carotenoids, lutein, zeaxanthin and violaxanthin in the processed GLV varied based on the variety of leafy vegetable cooked and the method of cooking. Microwave cooking followed by steaming were the most recommended method, while deep frying drastically reduced the total carotenoids and xanthophyll content followed by sautéing with oil. Overall, different methods of cooking resulted in changes in the phytochemical composition which are due to various factors such as leaf matrix, cooking method, cooking time and temperature.