Food Uses and Nutritional Benefits of Sweet Potato
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® Fruit, Vegetable and Cereal Science and Biotechnology ©2012 Global Science Books Food Uses and Nutritional Benefits of Sweet Potato G. Padmaja* • Jaffer T. Sheriff • Moothandassery S. Sajeev Central Tuber Crops Research Institute, Thiruvananthapuram-695017, India Corresponding author : * [email protected] ABSTRACT Sweet potato (Ipomoea batatas (L.) Lam.) has high ability to convert solar energy in to carbohydrates and store it in the bulky roots that are recognised as one of the energy godowns of nature. Sweet potato is next to cassava (Manihot esculenta Crantz) in acreage, widespread cultivation, diversified uses etc., among the tuber crops in the world. With rapidly changing lifestyle and urbanization, the significance of sweet potato as a food is getting diminished. Nevertheless, its importance as a health food is being increasingly realised now. A number of novel food products with functional value are being developed worldwide. Sweet potato tubers with their low glycaemic index have additional value as a food for diabetics. There are a range of primary food products that could be made from sweet potato like chips, flakes, frozen products, French fries, puree, etc., while it is also the raw materials for a host of secondary products like noodles, sugar syrups, alcohol, pasta etc. The potential of sweet potato as a promising food crop is discussed. _____________________________________________________________________________________________________________ Keywords: chips, canning, frying, noodles, pasta Abbreviations: DSF, defatted Soy Flour; fwb, fresh weight basis; MJ, Mega Joules; RSS, restructured sweet potato sticks; RTE, ready to eat; RWF, refined wheat flour CONTENTS INTRODUCTION...................................................................................................................................................................................... 115 PRIMARY FOOD PRODUCTS ................................................................................................................................................................ 116 DEHYDRATED CHIPS AND FLOUR ..................................................................................................................................................... 117 CANNED SWEET POTATOES................................................................................................................................................................. 117 FROZEN SWEET POTATOES.................................................................................................................................................................. 117 FRIED SWEET POTATO PRODUCTS..................................................................................................................................................... 117 SWEET POTATO PUREE......................................................................................................................................................................... 118 SWEET POTATO FLAKES....................................................................................................................................................................... 118 SECONDARY FOOD PRODUCTS .......................................................................................................................................................... 119 Noodles and other extruded foods ......................................................................................................................................................... 119 SUGAR SYRUPS ...................................................................................................................................................................................... 119 COMMODITY CHEMICALS FROM STARCH ...................................................................................................................................... 119 NON-ALCOHOLIC AND ALCOHOLIC BEVERAGES.......................................................................................................................... 120 Alcoholic beverages .............................................................................................................................................................................. 120 FLOUR-BASED FOOD PRODUCTS....................................................................................................................................................... 120 NOVEL FOOD PRODUCTS FROM SWEET POTATO........................................................................................................................... 120 INTERMEDIARY FOOD PRODUCTS .................................................................................................................................................... 121 SWEET POTATO LEAVES AS HUMAN FOOD...................................................................................................................................... 121 FUTURE PERSPECTIVES ....................................................................................................................................................................... 121 REFERENCES........................................................................................................................................................................................... 122 _____________________________________________________________________________________________________________ INTRODUCTION crops of man due to the health contributing principles in the tubers and leaves. Despite the fact that it is one the highest Sweet potato (Ipomoea batatas (L.) Lam.) is cultivated energy producing crops (152 MJ ha-1 day-1), it seldom finds throughout the tropics and warm temperate regions of the use as a starchy staple in countries other than China and world for its starchy roots, which can provide nutrition, Japan. The latter two countries have developed several besides energy. The edible tuberous root is either long and value added products from sweet potato tubers and leaves, tapered, ovoid or round with a skin colour ranging from realising its nutritional attributes as well. Unlike the South- white, brown, purple or red and the flesh colour ranging east Asian countries and India, China, which is the largest from white, pale cream, orange or purple. Besides, the plant producer of sweet potato, also utilizes a major part of its is also much valued for its green tops, which are a con- production for animal feed purposes. With the introduction centrated source of many essential vitamins and minerals. of a large number of orange fleshed varieties having high - Although China is the largest producer of sweet potatoes, carotene content ranging even up to 20-30 mg 100 g-1, there accounting for more than 80% of the world supply, only is a recent upsurge of interest in including sweet potato 40% of the production is used for human consumption and roots as a part of the food-based strategy to compensate industrial uses, while, the rest goes as animal feed. Sweet vitamin A deficiency, especially in African countries and potatoes are considered as one of the most important food Bangladesh. Received: 1 November, 2011. Accepted: 1 November, 2012. Invited Review Fruit, Vegetable and Cereal Science and Biotechnology 6 (Special Issue 1), 115-123 ©2012 Global Science Books PRIMARY FOOD PRODUCTS hury 1992). It was found that the high starch sweet potato varieties could be incorporated only up to 60% (Padmaja Sweet potato is cultivated and utilized extensively in Asia and Premkumar 2002). and South east Asian countries, although processed prod- Sweet potato pickles have been made from orange ucts are more common in countries like Indonesia, Philip- fleshed varieties in Bangladesh and Philippines and white pines, Thailand, Malaysia and Vietnam. The tubers are variety in India (Chaudhury 1992; Padmaja and Premkumar eaten after boiling or baking and increase in sugars during 2002; Tan et al. 2005). Blanched sweet potato cubes were these processes makes the tubers sweet after cooking. The used in Philippines, while lightly fried cubes were used in ‘dry’ type of tubers will be dry and firm but mealy after Bangladesh (Chaudhury 1992; Golder et al. 2005). In India, cooking, while the ‘moist’ type will be soft and watery as the cubes were treated with 1.0% acetic acid solution for 1 well as sticky after cooking (Rao et al. 1974). h to prevent browning and then used for pickling. Golder et A major problem in the utilization of sweet potato is the al. (2005) found that the best formula for sweet potato jam post harvest damage often triggered by the pathogen entry was sweet potato pulp (52.22%), sugar (46.90%), citric acid through cut surfaces. Curing at a relative humidity of 85% (0.53%) and pectin (0.26%). Microbe aided lactic acid fer- and temperature of 29-30°C is often practiced in the South mentation of sweet potato for pickling purpose was also Asian countries and India, which facilitates wound- healing attempted in India. The sweet potato cubes, after blanching and enhances the shelf life of the roots. Curing has been in boiling water for one minute were put to salt solution reported to induce the amylolytic enzymes in sweet potato, (10% w/w) and starter culture of Lactobacillus plantarum leading to the production of sugars and development of was added to this (Ray et al. 2005). sweetness. Studies have been made by various researchers Sweet potato based composite flours have been used in in India to develop