β-carotene content in sweet potato varieties from China and the effect of preparation on β-carotene retention in the Yanshu No. 5

To compare the beta-carotene contents in different Chinese sweet potato (SP) varieties and to choose a variety of SP rich in beta-carotene for the study of the effect of processing methods on beta-carotene retention, beta-carotene in thirteen varieties of sweet potato from China was measured by HPLC. The results showed that beta-carotene contents were significantly correlated with SP flesh colours, with the orange-red fleshed SP varieties being higher in beta-carotene. beta-carotene contents in SP were affected by many factors, and this was demonstrated using the variety of Yanshu No.5, showing that the beta-carotene contents in SP grown in different farming sites in the same area ranged from 53.2 to 84.3 mg kg(-1) fresh weight. Moreover, beta-carotene distributes unevenly in one SP root, with highest concentrations in the core. The beta-carotene content was positively related to the root size. Five processing methods including boiling, steaming, microwave cooking, frying, and post steam-drying were simulated in the study to check their effects on the true retention of beta-carotene in SP. Compared to boiling, steaming resulted in much more loss of beta-carotene and microwave cooking resulted in the biggest loss of carotene among the five processing methods. Industrial relevance: Orange-fleshed sweet potato can be prepared for sale and consumption, using methods that protect the beta-carotene content. This can aid in promoting sweet potato as a staple food as well as a snack food for supplying vitamin A for both rural and urban populations. Prepared orange-fleshed sweet potato can contribute to alleviating vitamin A deficiency in China as well as other low-income countries. (C) 2008 Elsevier Ltd. All rights reserved.