Department of Science Technology, Federal Polytechnic, Ado-Ekiti. Nigeria. Abstract: The effect of some processing methods on the Vitamin C content of sweet ...
Research Journal of Agriculture and Biological Sciences, 6(6): 981-982, 2010 © 2010, INSInet Publication
The Effect of Some Processing Methods on the Vitamin C Content of Sweet and Irish Potato Babalola O.O, Adubiaro H.O and Ikusika O. Department of Science Technology, Federal Polytechnic, Ado-Ekiti. Nigeria. Abstract: The effect of some processing methods on the Vitamin C content of sweet and Irish potatoes were investigated. Processing methods employed were, cooking, frying and baking. Raw sweet and Irish potatoes contained 160mg/100g and 79.3mg/100g of Vitamin C respectively. The highest loss of 114mg/100g (71.25%) was observed when sweet potato was cooked followed by frying 99.1mg/100g (61.93%) while baking produced a loss of 82.50mg/100g (51.50%). The trend of loss of Vitamin C in Irish potato was the same with sweet potato. Cooked Irish potato lost 50.30mg/100g (63.43%), fried, 43.30mg/100g (54.60%) and baked, 41.30mg/100g (52.08%). Thus, different processing methods resulted in appreciable loss of Vitamin C with the highest loss observed when the potatoes were boiled and the least loss when they were baked. Key words: Vitamin C, Sweet potato, Irish potato, Processing methods. a mortar. The extract was quantitatively transferred with distilled water into a 50ml volumetric flask and made up to the mark with distilled water. This was followed by filtration into a conical flask. The filtrate was run from a burette into a conical flask containing one drop dilute acetic acid and 1ml of 2,6dichlorophenol indophenol solution. The volume required to decolourize the dye was noted. The titration was repeated using standard ascorbic acid solution (1mg pure vitamin per 100ml) in place of the samples. Hence the amount of ascorbic acid per 100g of the samples was determined[5].
INTRODUCTION Potato is a tuberous dicotyledonous crop grown all over the world because of the special role that it plays in our diet. It is a source of raw material for the cook, can be eaten as vegetable and are cheap and nutritious. Irish potato, Solanum tuberosum named after the Irish who were among the first to accept the potato, proved to be a source of protein as well as substantial amount of Vitamin C[1]. Sweet potato, Ipomea batata are irregularly shaped oblong tubers that have sweet taste. Potatoes can be boiled, steamed, braised, baked, roasted, fried or grilled[2]. Vitamin C is required for the growth and repair of tissues in the body. It is necessary to form collagen, an important protein used to make skin, scar tissue, tendon, ligament and blood vessel. It is also essential for healing of wounds and for the repair and maintenance of cartilage, bones and teeth[3].The recommended daily allowance for adult men and women is 75mg/day[4]. The different processing methods pose various threats to the retention of Vitamin C in the processed tubers. The present study therefore investigates the extent of loss of the vitamin during cooking, frying and baking.
RESULTS AND DISCUSSION From the result presented in Table 1, raw sweet potato contains 160mg/100g Vitamin C. The highest loss of 114mg/100g (71.25%) was observed when it was cooked in water while baking produced the least loss of 82.5mg/100g (51.50%). The result presented in Table 2 for Irish potato revealed the same trend of loss as that obtained for sweet potato. Raw Irish potato contained 79.3mg/100g Vitamin C. Boiling in water produced a loss of 50.3mg/100g (63.43%) while baking produced the least loss of 41.3mg/100g (52.08%). Sweet and Irish potatoes are examples of root crops that are not easily digested in their natural state and should be processed before they are eaten. Processing improves their keeping quality as well as making the roots safe to eat. The heat used during processing can be dry as in an oven or wet heat as when boiling, steaming or frying[6].
MATERIALS AND METHODS The potato samples were freshly purchased from Bisi market in Ado-Ekiti, Ekiti State, Nigeria. The different processing methods were employed as described by Hampson,[2]. 10g of each sample was weighed and ground with a little glacial acetic acid in
Corresponding Author: Babalola O.O, Department of Science Technology, Federal Polytechnic, Ado-Ekiti. Nigeria.
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Res. J. Agric. & Biol. Sci., 6(6): 981-982, 2010 Table 1: Vitamin C content of raw and processed sweet potato Processing method Amount of Vitamin C (mg/100g) Loss of Vitamin C (mg/100g) % loss of Vitamin C Raw 160.0 ± 3.12 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Baked 77.5 ± 2.03 82.5 51.50 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Fried 60.9 ± 1.87 99.1 61.93 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Boiled 46.0 ± 1.64 114.0 71.25 Mean of 3 determinations ± standard deviation Table 2: Vitamin C content of raw and processed Irish potato Processing method Amount of Vitamin C (mg/100g) Loss of Vitamin C (mg/100g) % loss of Vitamin C Raw 79.3 ± 2.14 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Baked 38.0 ± 1.42 41.3 52.08 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Fried 36.0 ± 1.58 43.3 54.60 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Boiled 29.0 ± 1.23 50.3 63.43 Mean of 3 determinations ± standard deviation
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The values obtained above for sweet potatoes are higher when compared with the values reported by Sinder et al.,[7] who obtained losses of 65%, 57% and 45% respectively when the potatoes were boiled, fried and baked. Aidoo,[8] also obtained losses of 58%, 50% and 49% respectively when Irish potatoes were subjected to the same processing method as above. He also reported losses of 93%, 85% and 75% respectively when yam was subjected to the same treatment as the potatoes. These loses were higher than that obtained for sweet and Irish potatoes. In both products, percentage losses in Vitamin C content occur in two ways during processing, first by degradation which can occur by destruction or by other chemical changes such as oxidation and secondly by leaching into the cooking medium. In all the processing method employed, baking seems to retain more Vitamin C than the other methods. It is therefore recommended that potatoes should be eaten baked and if other processing methods should be employed, for optimum intake of Vitamin C, raw vegetables and fruits that supply enough Vitamin C should be combined in the diet.
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REFERENCES 1.
Hamilton, C., A. Andy and W. Dave, 2004. Importance and usefulness of potato. Advanced Agricultural Science, 2nd edition, Pp. 614-625. Plenum Publisher, New York/London.
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Hampson, H., 1957. Food and drinks, potato and vegetable and their preparation. Food and Nutrition. 2nd Edition, pp: 490-499. Press publisher, New York/London. Sweetman, J., 2007. Importance of Vitamin C in the body. Advance Food Biochemistry, 2: 283-321. Plenum Press Publisher, New York/London. Schoental, A., 2006. Daily recommendation of Vitamin C. Journal of food and Nutrition board institute of Medicine, 15(8): 23-34. Sadasivam, S. and A. Manickam, 1996. Biochemical Methods for Agricultural Sciences. Second Edition, pp: 184-185. New Age International (P) Limited, Publishers. Allison, R., 1993. Effect of variety, storage and locality on the ascorbic acid content of potato tuber. Journal of Food and Agriculture, 14(16): 155-221. Sinder, A., J. Watson and S. Stevenson, 1973. Food processing method. Potato recipe. 3rd edition, pp: 740. Aidoo, A., 1966. The effect of processing methods on tuberous dicotyledonous crops. Advanced Food Biochemistry, 3rd Edition, pp: 113-125. Plenum Press Publisher, New York/London.
