| This paper studies the precook technology of the three kinds of kidney beans,and rice cooked thoroughly at the same time,through this process the kidney bean has a complete appearance.First we optimized the process of the three kinds of kidney beans,and got the best precook process parameters of three kinds of kidney beans.And then study the effect of precook treatment on three kinds of kidney beans of main nutritional components,texture characteristics,shape and chroma.By enzyme hydrolyzation,amylase content,resistant starch,visible light absorption spectrum,X-ray diffraction,SAXS,infrared spectrum scanning,microscopic scanning microscopy and differential scanning calorimetry analysis,analyzes the effect of the precook treatment on the three kinds of kidney beans' starches.Experimental research conclusions are as follows:(1)The best precook process of three kinds of kidney beans were obtained.Purple speckled kidney bean: constant temperature 50 ? for 30 min,low pressure cooking 50 kPa for 5 min.Black kidney bean: constant temperature 50 ? for 30 min,microwave cooking 1600 W for 6min,the ratio of material to water were 1:2,hot air drying 80 ? for 1.5 h,microwave drying 600 W for 3min.White kidney bean: constant temperature 50 ? for 40 min(the ratio of material to water were 1:3),high pressure cooking 121 ? for 15 min(the ratio of material to water were 1:2),hot air drying 60 ?.(2)Nutrients,chroma and texture characteristics analysis shows that the difference between raw kidney beans and precooked kidney beans of nutrients are not obvious,the general trend was that the protein content and fat content were decreased,the starch content was increased.After cooked with rice,the hardness of three kinds of precooked kidney beans were lower than the raw kidney beans.Among them,the hardness of precooked purple speckled kidney beans and precooked black kidney beans were lower than rice after cooked together,while the hardness of precooked black kidney beans was close to rice after cooked together,but slightly larger than rice.The chewiness of three kinds of precooked kidney beans were lower than raw kidney beans after cooked with rice.Among them,the chewiness of precooked black kidney beans was the half of rice,the chewiness of precooked purple speckled kidney beans was lower than rice,while the chewiness of white kidney beans was two times of rice.This shows that the precooked purple speckled kidney beans and black kidney beans could cooked very well with rice,but the curing effect of precooked white kidney beans was not very good.After precook,the appearance of three kinds of kidney beans remained intact.Among them,the coat of purple speckled kidney beans was slightly faded.The value of L* and a* were decreased,the value of b * was increased,it shows that the kidney beans became darker and red.There is few of precooked black kidney beans has cracks,and the appearance of grain became darker.The value of L* decreased,the value of a* and b* increased,it shows that the lightness of precooked black kidney beans decreased,the redness increased and became yellowness.(3)By microscopic examination of the polarized light microscopy,found that the appearance of raw material of purple speckled kidney beans' starch was smooth and the polarization cross is obvious and complete.After precook,the appearance of purple speckled kidney beans' starch became rough,and some granules had porous surface.The polarization cross was unclear and incomplete.This shows that the appearance and center of starch were damaged.Through amylose kits,amylose content of precooked purple speckled kidney beans starch is reduced;the maximum absorption peak shift to the left and visible light absorption spectrum scanning,the combination of starch and iodine capacity variation;it shows that the amylose content was reduced,it was consistent with the determination results of the kit.After precook,the enzymatic hydrolysis of starch was increased,which was easy to digest and absorb.The content of resistant starch was slightly increased,it might be due to that the starch catch cold during precook process,the retrogradation of starch,and the resistant starch content increased.Starch of X-ray diffraction results show that the precook treatment can't change the crystal type,but the relative crystallinity was decreased,starch structure becomes unstable.Starch of SAXS diffraction results show that the intensity of the scattering peak decreases at 0.6~0.8 nm-1,it showed that the precook destroyed the crystalline regions of starch,and made the semi-crystalline growth lamellae layered disorder,and the thickness of the crystalline layer decreased,which indicates that the crystallinity decreases,which is consistent with the results of X diffraction.Infrared spectrum analysis showed that the bands height ratio between 1047 and 1022 cm-1 was increased,it shows that the ordered structure of the surface of the starch granules increased.DSC analysis showed that the enthalpy of starch was increased,this may be related to ambient temperature,humidity and temperature.By microscopic examination of the polarized light microscopy,found that the appearance of raw material of black kidney beans starch was smooth and the polarization cross is obvious,brightness and complete.After precook,the appearance of most black kidney beans starch became rough,and most of the granules had porous surface.The polarization cross of most starch granules was disappearing.This shows that the appearance and center of starch were damaged,and the extent of the damage is much greater than purple speckled kidney beans.Through amylose kits,amylose content of precooked black kidney beans starch is reduced;the maximum absorption peak shift to the left and visible light absorption spectrum scanning,the combination of starch and iodine capacity variation;it shows that the amylose content was reduced,it was consistent with the determination results of the kit.After precook,the enzymatic hydrolysis of starch was increased,which was easy to digest and absorb.The content of resistant starch has a sharp drop.Starch of X-ray diffraction results show that the precook treatment can't change the crystal type,but the relative crystallinity was decreased,starch structure becomes unstable.Starch of SAXS diffraction results show that the Bragg layer spacing of precooked black kidney beans starch was decreased,and the intensity of the scattering peak was also decreased,and the thickness of the crystalline layer decreased,which indicates that the crystallinity decreases,which is consistent with the results of X diffraction.Infrared spectrum analysis showed that the bands height ratio between 1047 and 1022 cm-1 was decreased,it shows that the ordered structure of the surface of the starch granules decreased.DSC analysis showed that the enthalpy of starch was decreased,it is easy to digest in human body.By microscopic examination of the polarized light microscopy,found that the appearance of raw material of white kidney bean starch was smooth and the polarization cross is obvious and complete.After precook,the appearance of some white kidney bean starch became rough,and some granules had porous surface.The polarization cross was unclear and incomplete.This shows that the appearance and center of starch were damaged.Through amylose kits,amylose content of precooked white kidney bean starch is increased;the maximum absorption peak shift to the right and visible light absorption spectrum scanning,the combination of starch and iodine capacity variation;it shows that the amylose content was increased,it was consistent with the determination results of the kit.After precook,the enzymatic hydrolysis of starch was increased,which was easy to digest and absorb.The content of resistant starch was slightly decreased.Starch of X-ray diffraction results show that the relative crystallinity of precooked white kidney bean starch was decreased,starch structure becomes unstable.Starch of SAXS diffraction results show that the average thickness of the lamellar structure in the semi crystalline region was decreased,and the thickness of the crystalline layer decreased,which is consistent with the results of X diffraction.Infrared spectrum analysis showed that the bands height ratio between 1047 and 1022 cm-1 was slightly increased,it shows that the ordered structure of the surface of the starch granules increased.DSC analysis showed that the enthalpy of starch was increased. |
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