| Low glycemic index(GI)foods are effective on postprandial glycemic control thus diabetes subjects can be benefitted by low GI foods.But there are little reports about low GI foods.In vitro digestibility of 12 species cereals and 8 species legumes were investigated and relative low eGI(expected glycemic index,eGI)cereals and legumes were selected.The effects of protein and lipid on the in vitro digestibility and physicochemical properties of 3 selected cereals and 2 selected legumes were investigated.The influences of different processing on cereals and legumes eGI were studied.The product formula was designed with reference to the amino acid pattern recommended by FAO.Optimized parameters were obtained.The in vivo glycemic response to product was also measured.The results of in vitro digestibility indicated that the eGI of black millet,oat,rye and adly were between 55-70 when white bread was set as reference food.Therefore,black millet,oat,rye and adly are medium eGI foods and other cereals are high eGI foods with higher eGI(>70).The eGI of red bean,mung bean and red kidney bean were high(>70)thus they are high eGI foods.And the rest of legumes are medium eGI foods with lower eGI(55-70).Compared with the original cereal flour and legume flour,the removal of fats,protein caused significant differences in the eGI and chemical composition of adlay,oat,rye,colored kidney bean and chickpea.The differences included the decrease of partical size and gelatinization temperature,solubility and swelling properties.The protein content and protein/starch of cereals were negative with eGI(p<0.05).The protein content and protein/starch of legumes were significantly negative with eGI(p<0.01).Fat content and fat/starch of both cereals and legumes had no significant correlation with eGI.The effects of different processing methods(steaming,extruding and roller-drying)on eGI of adlay,oat,rye,colored kidney bean and chickpea were investigated.The results showed that the eGI of steamed samples were in the following order: rye>adlay>oat> colored kidney bean>chickpea.The eGI of extruded samples were in the following order: adlay>rye>oat>colored kidney bean>chickpea.The eGI of roller-dried samples were in the following order:adlay > rye > oat > colored kidney bean > chickpea.By different processing methods,the eGI of oat,colored kidney bean and chickpea were lower among five samples.Therefore,oat,colored kidney bean and chickpea were selected as main material of mixing powder.With lysine,threonine and methionine as balanced amino acid to designe formula,and the optimal ratio of raw materials was as follows,oat: chickpea: colored kidney bean = 16.43:76.35:7.22.The eGI of mixing powder under streaming,extruding and roller-drying were: 59.43,60.35,68.04,respectively.The DSI(drying-matter solubility index,DSI)of mixing powder under streaming,extruding and roller-drying were: 14.51%,18.72%,20.11%,respectively.To prepare high DSI and low eGI mixing power,extruding was selected as processing method.The effects of temperature,water content and screw speed on DSI and e GI of products were studied by single factor test.Optimized parameters were obtained: terminal barrel temperature program 60-80-100-120°C,25% water content,screw speed 100r/min.DSI of mixing powder achieved 16.45%,eGI was 57.41.The GI(glycemic index,GI)of mixing power was 52.13 with glucose as the reference food(glucose GI = 100),so the product was low GI food. |
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