Synthesis of resistant starch in three Rwandese cassava varieties and its applicability in yoghurt processing

Abstract

 Starch is the most plentiful granular polysaccharide in plants where it is found in the chloroplast of leaves and the amyloplast. Based on digestibility starch is classified into three types: rapidly digestible starch, slowly digestible starch and resistant starch. Resistant starch (RS) is defined as the sum of starch and products of starch breakdown which are not absorbed in the small intestine of humans. In  bowel, RS serve as a substrate for microbial fermentation that produce carbon dioxide, methane and short chain fatty acids known to prevent colon diseases. Cassava   is a staple food crop in Rwanda where it is mainly utilized as flour for paste (Ugali) or consumed raw, boiled, fried or roasted and its leaves are consumed as vegetables. Differences in amounts of RS present in popular cassava varieties in Rwanda and effects of applying different heat treatments on cassava starch is not yet known. On the other hand, popular products such as yoghurt rely heavily on imported relatively expensive corn starch, pectin and gelatin for their production in Rwandan context. Application of cassava starch with good component of beneficial healthy RS in their processing as a thickening agent is yet to be tested.  There is also a wide gap in cassava value addition in Rwanda where its industrialization is solely limited to manufacturing of packaged flour. The current proposed project seeks to determine the levels of RS in popular cassava varieties in Rwanda and to demonstrate opportunity in adding value to cassava starch by synthesizing RS and testing its applicability in processing acceptable yoghurt. This study will provide scientific information on which cassava variety and treatment can produce large amount of RS and will demonstrate the opportunity for cassava product diversification as well as providing yoghurt rich in probiotics and prebiotics (RS) as a preventive measure against colon cancer.

Key words: Resistant starch, Cassava, yogurt