Effects of Extrusion Temperatures on Physicochemical Properties and Starch Digestion Characteristics in Vitro of Cyperus esculentus Meal
The experiment was conducted to study the effects of different extrusion temperatures on physico-chemical properties and starch digestion characteristics in vitro of Cyperus esculentus meal(CEM).CEM was extruded using twin-screw extruder at 120,140 and 160 ℃,respectively.Then the nutrients,physicochemical properties and starch digestion characteristics in vitro of CEM before and after extrusion were determined.The results showed as follows:1)compared with unextruded CEM,the crude protein content in 120 and 160 ℃ extruded CEM was significantly decreased(P＜0.05),the starch content in 140 and 160 ℃ extruded CEM was significantly decreased(P＜0.05),and the contents of ash and amylose in all extruded CEM were significantly decreased(P＜0.05).The gelatinization degree of extruded CEM was significantly increased(P＜0.05).2)Compared with unextruded CEM,the brightness(L*)value of extruded CEM was significantly decreased(P＜0.05),and the redness(a*)and yellowness(b*)values were significantly increased(P＜0.05);the water absorption index,water solubility index and swelling power were significantly increased(P＜0.05);the hardness,chewiness and gumminess of gel were significantly decreased(P＜0.05),and the cohesiveness of gel was significantly increased(P＜0.05);the peak viscosity,trough viscosity,final viscosity,consistence viscosity and peak time were significantly decreased(P＜0.05);the crystal structure of starch in extruded CEM changed from A-type to V-type,and the relative crystallinity of starch was significantly decreased(P＜0.05).3)Compared with unextruded CEM,the contents of rapidly digestible starch and slowly digestible starch in ex-truded CEM were significantly decreased(P＜0.05),and the resistant starch content in extruded CEM was sig-nificantly increased(P＜0.05).4)With the increase of extrusion temperature,the starch content in extruded CEM gradually decreased,the color gradually deepened,the gelatinization degree,water solubility index and slowly digestible starch content in starch gradually increased,and the resistant starch content in starch showed a trend of decreasing first and then increasing.In conclusion,the extrusion can reduce the starch and crude pro-tein content in CEM,improve hydration properties,reduce gel hardness,chewiness and gumminess,improve gelatinization degree and hot paste stability,and at the same time,the starch crystal of CEM changes into V-type crystallization,the rapidly digestible starch decreases,and the resistant starch content increases;under the experimental conditions,140 ℃ is recommended as the processing temperature of extruded CEM.[Chinese Journal of Animal Nutrition,2024,36(6):4050-4061]
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