2.2. Film preparation
Rice starch and rice flour films were prepared by a casting
technique. Glycerol and sorbitol were used as plasticizers at
concentrations of 0.20 and 0.30 g/g dry raw material (starch or
flour). Aqueous solutions containing 5% of raw material (starch or
flour) were prepared and stirred for 15 min at 4000 rpm. Plasticizer
was added to the aqueous solution and the mixture was heated to
85 C in a thermal bath under constant stirring during 1 h to
promote the starch gelatinization, and poured homogeneously onto
plexiglass plates and dried at 30 C for 14 h in an oven with
circulating air. For preparation of rice flour films, the pH of the
aqueous solution was adjusted to 10.0 with NaOH solution (0.1 N),
in order to promote protein solubilization. Films plasticized with
glycerol were codified as SG (starch based films) and FG (flour
based films), and the ones plasticized with sorbitol were codified as
SS (starch based films) and FS (flour based films), followed by the
corresponding amount of plasticizer. For example, SG20 and FS30
were the formulations with rice starch film with 0.20 g glycerol/g
starch and rice flour film with 0.30 g sorbitol/g flour, respectively
2.2. Film preparationRice starch and rice flour films were prepared by a castingtechnique. Glycerol and sorbitol were used as plasticizers atconcentrations of 0.20 and 0.30 g/g dry raw material (starch orflour). Aqueous solutions containing 5% of raw material (starch orflour) were prepared and stirred for 15 min at 4000 rpm. Plasticizerwas added to the aqueous solution and the mixture was heated to85 C in a thermal bath under constant stirring during 1 h topromote the starch gelatinization, and poured homogeneously ontoplexiglass plates and dried at 30 C for 14 h in an oven withcirculating air. For preparation of rice flour films, the pH of theaqueous solution was adjusted to 10.0 with NaOH solution (0.1 N),in order to promote protein solubilization. Films plasticized withglycerol were codified as SG (starch based films) and FG (flourbased films), and the ones plasticized with sorbitol were codified asSS (starch based films) and FS (flour based films), followed by thecorresponding amount of plasticizer. For example, SG20 and FS30were the formulations with rice starch film with 0.20 g glycerol/gstarch and rice flour film with 0.30 g sorbitol/g flour, respectively
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