Isolation and Structure Investigations of Square Banana (Musa balbisiana) Starch

Starch was isolated from unripe square banana (Musa balbisiana) fruit and characterized physically and chemically. Isolation was done with a 23 factorial design using five replicates in the central trial. Evaluated factors were: flour: solvent ratio (1:6 ‐ 1:10, w/v); sodium bisulfite concentration (0.1 ‐ 0.3%); and soaking time (30 ‐ 60 min). Optimum starch isolation in an alkaline medium was obtained with: 1:5 (w/v) flour: solvent ratio; 0.1% sodium bisulfite concentration; and 60 min soaking time. Starch yield under these conditions was 69.8% with 94.5% purity. Starch granules had an oval‐elongate shape, a size range of 24‐68 μm, and average size of 24.6 μm. Amylose content was 22.2% and amylopectin content 77.8%. Granules had a C‐type ‐ray diffraction pattern and a degree of polymerization (DP) of 3‐20 for lengths of branch chains.