Abstract:
This research investigated the production of banana starch. Three varieties of Thai bananas ( Kluai Hak Muk, Kluai Nam Wa Kom, and Kluai Ta Nee), and three extracting solutions (sodium hydroxide, sodium bisulfite, and water) were studied. The yield of starch was 11-34% (db); the starch composed of 0.25-1.73% (db) protein, and the while index was 84.41-96.26, depended on verities of banana and extracting solution. Sodium hydroxide (0.05 N) was the most suitable solution for isolation of banana starch. The physicochemical properties of starches were different. Banana starches were composed of 11.47-11.76% moisture content, 0.22-0.93% (db) protein content, 0.07-0.17% (db) ash content, 0.016-0.025% (db) phosphorus content, and 95.68-99.46% (db) of starch content. Amylose content of starches were 30.90-31.98% on a dry weight basis. The shape and size of starch granules were different among verities. Swelling power and solubility of starches in water were a two-stage pattern. The initial gelatinization temperature (To) obtained by DSC of Kluai Nam Wa Kom starch and Kluai Ta Nee starch were 71.97 ํC and 71.67 ํC respectively, and were higher than Kluai Hak Muk starch (70.96 ํC). X-ray powder diffraction technique indicated that Kluai Hak Muk starch and Kluai Nam Wa Kom starch were B-type starch while that of Kluai Ta Nee starch was mixed b-type and C-type starch. Brabender viscoamylograph of the three starch pastes (6% db) in distilled water (pH 6.9) showed restricted-swelling patterns. Apparent viscosity and pasting temperature of starch paste decreased with decreasing pH from 7.0 to 3.5. Breakdown of the starch pastes markedly increased as pH was decreased from 4.5 to 3.5. Kluai Nam Wa Kom and Kluai Ta Nee starch pastes were highest setback at pH 4.5, but Kluai Hak Muk starch paste decreased with decreasing pH from 7.0 to 3.5. Retrogradation of the cold starch paste, held at temperature 4+-1 ํC for 1 to 3 days, were also examined by Texture Profile Analysis (TPA).