Physico-chemical qualities of selected potato (solanum tuberosum l.) cultivars and their suitability for product diversification in Rwanda

Abstract

Potato (Solanum tuberosum L.) is bulky and perishable with up to 50% of losses in 3-5 months of storage. Losses can be reduced through processing into less bulky and more stable products. The aim of this study was to investigate morphological and biochemical factors which affect potato quality, effect of potato cultivars and fermentation on quality of French fries and crisps as well as starch characteristics. Cultivars used included vartieties like Gikungu, Kigega, Kinigi, Kirundo, Mabondo, and Sangema and clones such as CIP399075.22, CIP392617.54, CIP 393251.64 and CIP399062.115. Laboratory experiment was Completely Randomised Design (CRD) with three replications. The skin colours were red, white, yellow, pink or purple, while the flesh was yellow or white. Specific gravity was 1.075-1.099, dry matter (DM) 20.45-25.93%, starch 14.33-19.28% on Fresh Weight Basis (FWB). Reducing sugars were 0.10-0.20%, non-reducing sugars 0.16-0.35%, and total sugars 0.26-0.55% FWB. Kinigi, Kirundo, Mabondo, Sangema and CIP393251.64 were selected for processing suing discriminant analysis. Discriminant analysis did not distinguish these cultivars for crisps and French fries. Internal oil was higher than surface oil and lower for French fries than crisps. Total oil was 11.97-18.48% for French fries and 33.49-42.84% for crisps. Fermentation increased acidity 0.01-0.02%, reduced pH 7.30-4.31, acrylamide 629.6-267.73 μg/kg for French fries and 855.30-339.59 μg/kg for crisps. Potato flour had high water absorption capacity (WAC) 265.39-303.11%, oil absorption capacity (OAC) 99.21-123.14%, foaming capacity (FC) 6.27-18.05% and emulsification capacity (EC) 30.00-44.17%. Rapidly digestible starch was 0.82-2.00% for raw potatoes, 46.71-50.87% for French fries, 69.66-70.31% for crisps; slowly digestible starch was 5.89-14.40% for raw potatoes, 37.35-38.58% for French fries, and 23.50-27.21% for crisps; resistant starch was 83.61-93.30% for raw potatoes, 10.25-14.53% for French fries, 2.91-8.20% for crisps; glycemic index (GI) was 59.44-68.37% for French fries, 66.23-70.23% for crisps; glycemic load (GL) was 9.91-13.36% for French fries and 11.05-13.57% for crisps. High DM and low reducing sugars are indicators of good quality potato for fried and dehydtared products. Oil absorption reduced with increase of DM. Reduction of acrylamide increases safety of the products. High WAC of flour is an indicator for use in food as thickening agent and where bulk is needed and high OAC is good for flavour retention which inceases food palatability. GI and GL were medium for both as a crisps and French fries and they can be used for control of metabolic disorders. Therefore, potato in this study can be used