| Poria cocos,as the dried sclerotic of polyporacea is a kind of traditional medicinal and edible Chinese herbs due to the nutritional and functional components,including polysaccharide and triterpenoid.Poria cocos has remarkable pharmacological activities,such as regulation of immune function,anti-tumor,antiviral,hypoglypidemic and hypolipidemic,anti-inflammatory,diuretic and so on.About 80% Chinese medicine prescriptions and more than 300 Chinese patent medicine contain poria cocos.The annual consumption of Poria cocos is nearly200000 tons for medicine,food or export.At presentt,the development of poria cocos food is limited because of insolublepolysaccharides.Therefore,improving the processing adaptability of Poria cocos has become the key technology of deep processing.Due to the effects of high temperature,pressure and shear force,the application of extrusion and recombination are used widely in improving material properties(starch gelatinization and degradation,protein spatial structure rupture,fat partial hydrolysis and then formed complex with amylose and protein).Few reports with regard to the influences of extrusion on water-soluble polysaccharide and triterpene of poria cocos are available.Meanwhile,poria cocos is hard to expand individually due to lack of starch and fiber.In order to provide a scientific basis for the development of high-valued Poria cocos food,this paper researched on quality characteristics and expected glycemic response of Poria cocos compound nutrition powder and extruded rice,which made from Poria cocos,adlay,tartary buckwheat,red rice and broken rice.1.The results of the dispersibility property and sensory of Poria cocos compound nutrition powder showed that,two principal components were extracted according to the principal component analysis of nine quality indexes,and the cumulative variance contribution rate was 92.241%.The optimal dosage of Poria cocos was 20%on the basis of the comprehensive score model.Under the condition,the dispersibility properties(gelatinization degree,extrusion degree,water solubility index(WSI),water absorption index(WAI),viscosity,nasogastric feeding liquidity,dispersion time and dispersion stability time),and sensory index of compound nutrition powder were relatively better.2.Poria cocos(optimal dosage of 20%)was mixed with four grains including adlay,red rice,broken rice and tartary buckwheat,respectively,and then extruded rice was prepared by twin-screw extrusion.The results showed that: compared with four raw grains,the gelatinization degree of the extruded rice of Poria cocos compound grain increased by 230.81%,202.13%,206.82% and 215.72%,rehydration time reduced by 1.04,0.76,0.83 and 0.82 times,and rehydration rate increased by 15.88%,19.45%,17.97% and 19.94% respectively,suggesting that the digestibility and rehydration of four grains were improved.Compared with the extruded rice without Poria cocos,the color of the extruded rice compound of Poria cocos was improved,while the hardness increased,and the mastication,resilience,adhesion,cohesion declined.In addition,the moisture existed in the forms of bound water and immobilized water,and the proportion of free water was zero.It was noteworthy that the retrogradation of starch increased,and the diffraction peak intensity of V-type crystal strengthened.3.The results of nutritional and functional components of Poria cocos compound nutrition powder and extruded rice showed that:(1)the loss of polyphenols and flavonoids by extrusion was less than recombinant granulation.Compared with raw red rice(32.16 mg/g),the polyphenol content of nutrition powder and extruded rice of red rice without Poria cocos decreased by 17.66% and 8.14%,respectively and the flavonoid content of nutrition powder and extruded rice of Poria cocos compound red rice decreased by 34.28% and 27.30%,respectively.Compared with raw tartary buckwheat(17.21 mg/g),the flavonoid content of the tartary buckwheat nutrition powder and extruded rice without Poria cocos decreased by 18.93% and 6.67%,respectively.(2)The two processing methods had less effects on the content of coixenolide,and any difference in coixenolide content was not significant(P<0.05)in all samples.(3)The two processing methods had certain effects on improving the water solubility of polysaccharides,but had little effects on three terterpene content of Poria cocos.Compared with raw Poria cocos,the water-soluble polysaccharide content from Poria cocos in nutrition powder and extruded rice(7.94mg/g-8.38mg/g)increased by 52.57%-61.07%.The difference of three terterpenes in Poria cocos was not significant(P<0.05).4.The contents of different types of starch and expected glycemic response in nutrition powder and extruded rice were evaluated.The results showed that: compared with raw grains,the rapid digestible starch(RDS)and resistant starch(RS)in nutrition powder and extruded rice without Poria cocos increased by 6.78%-24.12% and14.97%-68.14% respectively,while the slowly digestible starch(SDS)decreased by21.72%-41.44%.The dosage of 20% Poria cocos had no significant effects on the content of RDS and SDS(P<0.05),whereas it had significant effects on starch hydrolytic index(HI)and evaluate glycemic load(EGL)(P<0.05).The HI and EGL decreased by 4.81%-34.23% and 32.44%-41.82%,respectively..The lower HI and EGL were beneficial to maintain the postprandial blood glucose stabilization and reduce the glycemic load. |
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