Physico-Chemical Changes in Popular Kenyan Processing Potato Varieties as Influenced by Storage Condition

G. O. Abong^1*,  M. W. Okoth¹, J. N. Kabira², J. Ogolla¹, J. Ouma¹,  C. W. Ngunju¹ and K. Oded³

¹Department of Food Science, Nutrition and Technology, University of Nairobi, P.O. Box 29053-00625, Nairobi (Kangemi), Kenya

²National Potato Research Centre (KALRO), Tigoni, P.O. Box 338, Limuru. Nairobi, Kenya

³Sygenta East Africa Ltd., P.O. Box 30393-00100, Nairobi, Kenya.

corresponding Author: Email: georkoyo@yahoo.com

The current study sought to establish the physico-chemical changes in popular Kenyan potato varieties, Shangi, Dutch Robijn, Kenya Mpya, Asante and Tigoni, under different storage conditions.  Tubers were harvested at maturity and stored at varied relative humidity (82-92 %) and temperature (20-24 ^oC, 12-14 ^oC, 8-10 ^oC and 4-6 ^oC).The tubers were monitored for reducing sugars content, dry matter content, ascorbic acid content, greening, weight loss and sprouting. Results indicated that reducing sugars significantly (p<0.05) increased with time with the increase being pronounced at lower temperatures. At harvest, for instance, reducing sugars were 0.17 % in Shangi, this increased after 10 weeks of storage to 0.21 %, 0.31 %, 0.68 % and 0.89 % at ambient, 12-14 ^oC, 8-10 ^oC, 4-6 ^oC, respectively. The scenario was similar for Dutch Robijn, Asante, Kenya Mpya and Tigoni where increases were noted after a month of storage. Reduced ascorbic acid (vitamin C) in tubers decreased significantly (p<0.05) with storage time irrespective of storage temperature. Dry matter content varied significantly (p<0.05) with storage temperature and time. Prevalent ambient storage seemed to have higher increase in dry matter compared to lower temperature storage. The increase in dry matter content was more pronounced (p<0.05) in Asante and Kenya Mpya than in Dutch Robijn and Tigoni varieties. Weight loss was minimal in all the storage conditions being less than 5% while sprouting increased significantly (p<0.05) with storage time and with increased storage temperature. At ambient temperature and 12-14 ^oC, sprouts emerged in Shangi after 2 weeks and increased steadily with time reaching 43 mm after 10 weeks. Sprouts emerged after 2 months of storage in Dutch Robijn, Kenya Mpya and Asante being pronounced at 12-14 ^oC and ambient storage. Lower storage temperatures inhibited sprout growth and weight loss but significantly increased reducing sugars beyond processing requirements.

storage temperature; Sprouts; reducing sugars; potato varieties; reduced ascorbic acid

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