IMPACT OF PROCESSING METHODS ON RESISTANT STARCH COMPOSITION OF SOME CASSAVA BASED FOODS.

AUTHOR: OKAFOR, EDITH NWAKAEGO

DEPARTMENT: APPLIED MICROBIOLOGY AND BREWING

AFFILIATION: NNAMDI AZIKIWE UNIVERSITY, AWKA

Resistant starch (RS) is defined as that fraction of starch which escapes digestion in the small intestine and passes into the large intestine where it is fermented by the gut microflora. It is considered a functional component of food due to the health benefit it confers following its consumption. These benefits include the lowering of glycemic index of starchy foods and by the production of short chain fatty acids with a high proportion of butyric acid, which has a positive impact on bowel health. Thus, the higher the concentration of resistant starch in food, the safer it is for diabetic patients. Cassava root is a major staple food in Nigeria and Africa. The presence of toxic cyanogenic glycosides in its roots makes fermentation a compulsory step during its processing. The aim of this work is to determine the occurrence of resistant starch in cassava roots and to study how processing using traditional methods affect the concentration of resistant starch in our major cassava based foods. Six cassava varieties were used in this research; TMS 30555, TMS 117, TME 693, TMS 30572, TMS 98/0505 and TMS 4(2)1425. The concentration of RS in the tubers, during the various steps of processing and in the various foods was determined. The role of microbial growth and activity in changes in RS concentration was monitored by viable counts of the major groups of microorganisms. Specific microorganisms, which degraded RS were isolated on RS medium and identifiedusing routine methods and 16S rRNA sequence analysis. The results revealed that cassava tubers contained significant concentrations of RS which, differed among the varieties as follows; 6.96g/100g for TMS 30555, 7.07g/100g for TMS30572, 6.76/100g for TME 693, 6.95g/100g for TMS 98/0505, 5.79g/100g for TMS 4(2)1425 and 6.21g/100g for TME 117. Processing reduced the RS content in all cassava based foods studied. RS concentration was reduced by average of 70.4% in fufu, 47.68% in garri and 28.8% in abacha for the four varieties of cassava tested. All steps of cassava processing involving the activity of microorganisms such as soaking, dewatering and fermentation resulted in loss of RS. Fufu with the highest rate of microbial activity in terms of viable counts and duration of fermentation lost RS the most while abacha with lower counts and shortest duration of fermentation lost RS the least. Modifications of traditional methods of processing cassava fufu such as addition of nail to steeping water to shorten the retting time increased microbial activity resulting in higher loss of RS, while addition of bitter leaf reduced microbial activity leading to the retention of higher concentrations of RS. Addition of palm oil to cassava mash during garri production also reduced microbial activities and improved RS retention. Corynebacteriummanihotwas identified as major contributor to the loss of RS during fermentation of cassava. Cassava processing methods involving cooking (abacha) or frying (garri) on the other hand were observed to improve concentrations of RS in foods. Whereas fermentation is an important step in the processing of cassava for detoxification of cyanogenic glycosides, it reduces RS, a functional component of cassava based foods. Highest retention of RS in abacha suggests a lower glycemic index following its consumption making it the safest cassava based food for diabetics.

TO VIEW THE FULL CONTENT OF THIS DOCUMENT, PLEASE VISIT THE UNIZIK LIBRARY WEBSITE USING THIS LINK, http://naulibrary.org/dglibrary/admin/book_directory/Thesis/11607.pdf

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