| Summary: | 碩士 === 國立屏東科技大學 === 熱帶農業暨國際合作研究所 === 94 === The deficiency of Vitamin A is an endemic public health problem which increases the mortality of children under the age of five in many developing countries, especially in Africa. Among the alternatives to alleviate this problem, food-based approaches are agreed to be the most sustainable measures.
Plant origin provitamin A, carotenoids are the most accessible to the poor and represent 80% of the vitamin A intake in developing countries. However, these plants in most developing countries occur seasonally. Moreover, carotenoids are very sensitive to light, heat and oxygen.
The main objective of this study was to develop appropriate processing and storage conditions of sweet potatoes that would concentrate and preserve the β-carotene, for a better availability of vitamin A year round; thus contributing to the improvement of vitamin A intake in needy areas.
Orange-fleshed sweet potato roots were dried under open sun-drying, closed-type drying, and hot-air drying conditions. Fresh roots were washed, sliced at 2, 4 and 6 mm, then blanched in boiling water for 2, 4, and 6 min; then after drained on paper toweling prior to drying. The resulting chips from optimized drying conditions were fried using a home electric fryer, with temperature settings at 150, 160, and 170 °C for 60, 75, and 90 sec. Three categories of oil; including red palm oil (RPO), peanut oil (PO), and a blend of these two (BO) at 20% RPO were used. Sweet potatoes and PO were purchased from a local market in Pintung city, Taiwan, and RPO was obtained from West Africa (Burkina Faso, and Senegal). We used a Taguchi orthogonal array [L9(34)] for the drying, and the frying and storage experiments. The β-carotene content was monitored using HPLC
Our results using the signal to noise ratio (S/N) analysis indicated that 2 mm sweet potato slice, blanched in hot for four min, and dried in hot-air dryer at 45 °C was the best combination of control factors. A confirmation run yielded a 45% β-carotene increase as compared to the best predefined treatment. Blanching pretreatment appeared to be the most influential factor that determined the β-carotene retention in dried chips. Conversely, the drying efficiency was found to be governed by sweet potato slice thickness and drying temperature. Based on the S/R ratio at base-line, 20% RPO blend oil, heated at 150 to 160 °C for a 75 sec frying time, retained more β-carotene during the frying process. However storage at room temperature and 4 °C showed different trends after 4 weeks. It appeared that, the 4 weeks storage time favored cis to trans isomerization that increased the all-trans-β-carotene content. However, 4 weeks were likely not long enough to stabilize the reactions and to determine a definite trend to the change of β-carotene in fried chips. The color components (L*, b*), and hue angle and chroma were positively and highly correlated (p < 0.0001) to β-carotene content.
|
|---|
