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 &#946;-carotene contents in different Chinese sweet potato (SP) varieties and to choose a variety of SP rich in &#946;-carotene for the study of the effect of processing methods on &#946;-carotene retention, &#946;-carotene in thirteen varieties of sweet potato from China was measured by HPLC. The results showed that &#946;-carotene contents were significantly correlated with SP flesh colours, with the orange-red fleshed SP varieties being higher in &#946;-carotene.<br/><br/> &#946;-carotene contents in SP were affected by many factors, and this was demonstrated using the variety of Yanshu No.5, showing that the &#946;-carotene contents in SP grown in different farming sites in the same area ranged from 53.2 to 84.3 mg/kg fresh weight. Moreover, &#946;-carotene distributes unevenly in one SP root, with highest concentrations in the core. The &#946;-carotene content was positively related to the root size.<br/><br/> 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 &#946;-carotene in SP. Compared to boiling, steaming resulted in much more loss of &#946;-carotene and microwave cooking resulted in the biggest loss of &#946;-carotene among the five processing methods. <br/><br/>Orange-fleshed sweet potato can be prepared for sale and consumption, using methods that protect the &#946;-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.