干燥方法对山芋全粉微观结构和品质的影响

Effects of Drying Methods on Microstructures and Quality of Sweet Potato Flours

以新鲜山芋及经熟化的山芋为原料,分别采用热风干燥(Hot air drying,HAD)、远红外干燥(Far infrared drying,FID)、真空冷冻干燥(Vacuum freeze drying,VFD)、真空干燥(Vacuum drying,VD)法制备山芋生、熟全粉,比较各干燥方式得到的山芋全粉微观结构,并利用主成分分析法评价山芋全粉品质。结果表明,HAD和FID制备的山芋全粉颗粒表面凹凸不平,有许多裂纹和孔洞;VFD和VD制备的山芋全粉微观结构保持度较好,表面结构较光滑,表面附着的小颗粒也较少。经熟化处理后,山芋粉体颗粒体积膨胀,折叠起皱。VFD制备的山芋全粉亮度较大且色泽较白,持水性、持油性、复水能力较佳,总酚和VC含量最高。根据主成分分析法得到综合评分,其中,VFD山芋生粉得分最高,品质最好。综上,不同干燥方法对山芋全粉的微观结构和品质有较大影响,要综合考虑生产需求和成本来选择制备山芋全粉的最佳方法。

Fresh and cooked sweet potatoes were used as raw materials to prepare raw and ripe sweet potato flours using four drying methods including hot air drying(HAD),far infrared drying(FID),vacuum freeze drying(VFD)and vacuum drying(VD),then the microstructures of sweet potato flours were compared,and the qualities were evaluated by principal component analysis.The results showed that the surface of sweet potato flours prepared by HAD and FID was uneven with many cracks and holes.The microstructures of sweet potato flours prepared by VFD and VD were maintained well with smoother surface and fewer small particles attached to the surface.After cooking treatment,the sweet potato flour particles showed volume expansion and folding wrinkles.The sweet potato flour prepared by VFD presented higher brightness and white color,better water holding capacity,oil holding capacity and rehydration ability,and the highest contents of total phenol and VC.According to the comprehensive scores obtained by principal component analysis,sweet potato flour prepared by VFD had the highest score with the best qualities.In summary,different drying methods had significant impacts on the microstructures and qualities of sweet potato flours,and the best method for preparing the sweet potato flour should be selected by considering the production demand and cost.