POTATO PROCESSING RESEARCH IN THE UNIVERSITY OF NAIROBI Michael W. Okoth Department of Food Science, Nutrition and Technology University of Nairobi Paper presented at the East Africa Potato Research and Knowledge Exchange Forum, Nairobi, June 28, 2016
1. INTRODUCTION The mandate of the University of Nairobi is teaching, research, consultancy and outreach. Potato processing research in the University of Nairobi is done in the Department of Food Science, Nutrition and Technology that has been in existence for about 45 years. Potato processing research execution is mainly done by food science and technology as well as food safety and quality postgraduate students. An appreciable quantity of research work on potato processing has been done over the years and its outcome exists in students theses/dissertations and published scientific papers.
2. SITUATION ANALYSIS Adequate supply of fresh (ware) potato is essential for successful operation of processing enterprises. Abong, et al, (2010a) evaluated the characteristics of fresh (ware) potato traders in Nairobi and Nakuru towns, Kenya. They found that the potato varieties sold by most sellers were Cangi (42%) and Tigoni (34%). The average daily sales per trader was 200 kg. Abong et al. (2010b) studied the characteristics of the Kenyan potato crisps industry as well as the constraints in processing and marketing of potato crisps. They found that: the industry relied on one potato variety (Dutch Robyjn). Constraints included raw potato price fluctuations, scarcity and poor quality of potatoes, and lack of facilities, skills and information on raw potato storage. Miriti (2015) determined the quality characteristics (moisture content, oil content and colour) of French fries consumed in Nairobi. The oil content was 12.14 27.74% while the moisture content was 33.92 63.67%. 3. POTATO FLOUR PRODUCTION AND UTILIZATION Kabira (1990) showed that it was technically and economically feasible to dry potato slices for flour production in a simple solar drier utilizing natural air flow that he designed and constructed. He demonstrated that this flour could be incorporated into common local foods, for example to reduce the quantity of wheat flour in bread and other baked or fried products. 4. PRODUCTION OF FRENCH FRIES (CHIPS) Abong et al. (2009a) determined the influence of potato cultivar and stage of maturity on oil content of French fries (chips) made from eight Kenyan potato cultivars. The potato cultivar had a significant influence on oil uptake, with Dutch Robyjn having the lowest oil uptake. Harvesting at 90 days after planting resulted in a significantly higher oil content than harvesting at 120 days after planting.
Abong et al. (2009b) compared the nutrient contents of French fries from fresh potatoes and those from frozen potato chips and concluded that processing from frozen potato chips does not adversely affect the nutritional content of French fries. Evaluation of Kenyan potato cultivars by Abong et al. (2009c) for suitability for processing into fresh and frozen French fries established that five varieties ( Tigoni, Desiree, Dutch Robyjn, Kenya Karibu and Kenya Sifa) and clone 391691.96 were suitable for processing into French fries. Wekesa (2014) studied the influence of diffused light seed storage (DLSPS) and production location on physico chemical characteristics and suitability of selected Kenyan potato varieties for processing into French fries. DLSPS and production location affected physico chemical characteristics and suitability for processing into French fries, DLSPS having a positive influence. 5. PROUCTION OF POTATO CRISPS Abong et al. (2010c) evaluated the suitability of 24 Kenyan potato cultivars (18 varieties and 6 clones) for some physico chemical properties and suitability for processing into crisps. Dutch Robyjn, Tigoni and Kenya Baraka varieties and 4 clones were found sutable for processing into potato crisps. Abong et al. (2010d) determined consumption patterns, diversity and characteristics of potato crisps in Nairobi. They found that potato crisps are mostly consumed by children, youth and women. With the exception of thickness, most brands had characteristics (colour, size, moisture content, salt and oil content) that conformed to the local crisps standards. Abong et al. (2011a) evaluated the influence of frying temperature, packaging and storage temperature on ascorbic acid content of crisps from four potato cultivars. They found that low frying temperature, aluminium package and storage at temperatures below 30 o C resulted in optimum retention of reduced ascorbic acid. The effects of frying temperature and slice thickness on oil uptake and sensory quality of potato crisps processed from four Kenyan cultivars were studied by Abong et al. (2011b). They found that the oil content of potato crisps increased with decrease of slice thickness, frying temperature and fresh potato dry matter content. Abong et al. (2011b) conducted research on the effect of frying temperature and slice thickness on texture, colour and organoleptic properties of crisps from four Kenyan potato cultivars. There was a significant increase in texture with increase in frying temperature and slice thickness. Colour scores significantly decreased with increase in slice thickness. Potato cultivar significantly influenced L*a*b* colour scores and sensory scores.
Wekesa (2014) determined the influence of diffused light seed storage (DLSPS) and production location on physico chemical characteristics and suitability of selected Kenyan potato varieties and their suitability for processing into crisps, DLSPS having a positive influence. 6. CHEMICAL SAFETY OF FRENCH FRIES AND POTATO CRISP Ogolla (2013) studied acrylamide contamination in commercial potato crisps in Kenya; acrylamide content, levels of intake and effect of processing parameters on the content of acrylamide in crisps from local cultivars. The levels and intake varied with the market brands and potato variety and significantly increased with frying temperature and slice thickness. Miriti (2015) also determined the level of acrylamide in French fries consumed in Nairobi and found levels varying from non-detectable to 2309 µg/kg, these levels were much higher in low-end outlets than in high-end outlets. Miriti (2015) also carried out quantitative risk assessment of exposure to acrylamide through consumption of French fries in Nairobi. For those who consume French fries from the low-end outlets, she found exposure levels that warrant investigation and implementation of the most suitable mitigation measures. 7. CONCLUDING REMARKS Potato processing research in the University of Nairobi that started in the 1980s accelerated in the last decade. The research that has been completed has covered a number of areas including situation analysis, evaluation of potato varieties for suitability for processing, process development, product development, and product safety. New research is in progress and there is no doubt there is still considerable room for scientific investigations on potato processing and related issues. 8. REFERENCES ABONG, G.O.., OKOTH, M.W., KARURI, E.G., KABIRA, J.N. AND MATHOOKO, F.M. (2009a). Influence of potato cultivar and stage of maturity on oil content of French fries (CHIPS) made from eight Kenyan potato cultivars. African Journal of Food, Agriculture, Nutrition and Development 9 (8): 1667 1682. ABONG, G.O., OKOTH, M.W., KARURI, E.G., KABIRA, J.N AND MATHOOKO, F.M. (2009b). Nutrient contents of raw and processed products from Kenyan potato cultivars. Journal of Applied Biosciences 16: 877-886 (Available online at: http//ww.biosciences.elewa.org/japs)elewa. org/jabs).
ABONG, G.O., OKOTH, M.W., KARURI, E.G., KABIRA, J.N. AND MATHOOKO, F.M. (2009c). Evaluation of selected Kenyan potato cultivars for processing into French fries. Journal of Animal and Plant Sciences 2(3): 141-147. (Available online at: http://www.biosciences,elewa.org/japs). ABONG, G.O., OKOTH, M.W., KARURI, E.G., KABIRA, J.N. (2010a). Characteristics of fresh (ware) potato traders in Nairobi and Nakuru towns, Kenya. In: Mwangi M. (Editor). Contributions of agricultural sciences towards achieving the Millenium Development Goals. FaCT Publishing, Nairobi. 160pp. ABONG, G.O., OKOTH, M.W., KARURI, E.G., KABIRA, J.N. (2010b). Characteristics of the industry, constraints in processing, and marketing of potato crisps in Kenya. Journal of Animal & Plant Sciences 8(1): 936 943. ABONG, G.O., OKOTH, M.W., IMUNGI, J.K. AND KABIRA, J.N. (2010c). Evaluation of selected Kenyan potato cultivars for processing into potato crisps. Agriculture and Biology Journal of North America 1(5):886-893. ABONG, G.O., OKOTH, M.W., IMUNGI, J.K. AND KABIRA, J.N. (2010d). Consumption patterns, diversity and characteristics of potato crisps in Nairobi, Kenya. Journal of Applied Biosciences 32:1942-1955. ABONG, G.O., OKOTH, M.W., IMUNGI, J.K. AND KABIRA, J.N. (2011a). Losses of ascorbic acid during storage of fresh tubers, frying, packaging and storage of potato crisps from four Kenyan potato cultivars. American Journal of Food Technology 6(9):772-780. ABONG, G.O., OKOTH, M.W., IMUNGI, J.K. & KABIRA, J.N. (2011b). Effects of cultivar, frying temperature and slice thickness on oil uptake and sensory quality of potato crisps processed from four Kenyan potato cultivars. Journal of Agricultural Science and Technology A 1: 156-163. ABONG, G.O., OKOTH, M.W., IMUNGI, J.K. AND KABIRA, J.N. (2011c). Effect of slice thickness and frying temperature on color, texture and sensory properties of crisps made from four Kenyan potato cultivars. American Journal of Food Technology 6(9):753-762. OGOLLA, J.A. (2013). Acrylamide contamination in commercial potato crisps in Kenya: Levels of intake and effect of processing parameters on local cultivars. M.Sc. Dissertation, University of Nairobi. KABIRA, J.N. (1990). Feasibility of small scale production of solar dried potato (Solanum tuberosum) flour and its potential food uses in Kenya. PhD Thesis, University of Nairobi. MIRITI, J.W. (2015). Quality characteristics and quantitative risk assessment of exposure to acrylamide associated with consumption of French fries (chips) in Nairobi, Kenya. M.Sc. Dissertation, University of Nairobi.
WEKESA, M.N. (2014). Influence of diffused light seed storage and production location on physico chemical characteristics and processing suitability of selected Kenyan potato (Solanum tuberosum) varieties. M.Sc. Thesis, University of Nairobi.