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Slow digestible colored rice flour as wall material for microencapsulation: Its impacts on gut bacterial population and metabolic activities

Wattananapakasem, Isara, Costabile, Adele, Suwannaporn, Prisana
Food research international 2018 v.103 pp. 182-191
Lactobacillus, amylose, biochemical pathways, color, crystal structure, fermentation, fluorescence in situ hybridization, gastric juice, glutinous rice, gum arabic, hydrolysis, ingredients, microencapsulation, molecular weight, mortality, pasting properties, prebiotics, probiotics, pullulanase, rice flour, scanning electron microscopy, short chain fatty acids, starch granules, thermal properties
Black waxy and red jasmine rice flour (6.5% and 18.7% amylose content, respectively) were modified using pullulanase followed by heat-moisture treatment (Hydrolyzed-HMT) to produce microcapsules that entrapped L. plantarum TISTR 1465. Hydrolyzed-HMT of colored rice flours showed restricted pasting properties, lower breakdown and higher thermal properties than native flour (p<0.05). Hydrolysis treatment was able to promote a low molecular weight starch that easily formed a crystalline structure after HMT. As a consequence, a significant increase in slowly digestible starch was observed (from 23.7% to 37.0% in waxy type and 22.2% to 34.6% non-waxy type). The survival of L. plantarum TISTR 1465 after simulated gastric fluid (90min) and simulated intestinal fluid (120min) of the Hydrolyzed 36h-HMT black waxy rice was higher (8.07±0.13logCFU/g and 7.48±0.12logCFU/g) than gum arabic (6.12±0.11 and 4.72±0.28logCFU/g) and no carrier (3.34±0.23 and 0.43±0.75logCFU/g) respectively. Moreover, these microcapsules also obtained the highest survival (8.67±0.20logCFU/g) after storage for 90days at 4°C. Under scanning electron microscopy, starch granules of the hydrolyzed 36h-HMT were seen as polyhedral shapes in the spherical aggregates that carried the microorganisms and reduced their injury and mortality. Short-chain fatty acids of the hydrolyzed 36h-HMT were much higher than positive control at every fermentation time (p<0.01). The fluorescence in situ hybridization result showed that the prebiotic property of hydrolyzed 36h-HMT black waxy rice can better aid the beneficial probiotic Lactobacillus spp. growth after 24h fermentation than the negative control (from 8.40±0.48 to 7.03±0.21logCFU/g, p<0.05) and commercial prebiotic Orafti®Synergy1 (8.40±0.48 to 7.47±0.08logCFU/g, p<0.01). Microencapsulation of hydrolyzed black waxy rice flour followed by HMT is proposed as a synbiotic ingredient to apply in synbiotic foods.