真空微波干燥对草莓脯品质的影响

Effect of Vacuum Microwave Drying on Quality of Candied Strawberry

为了研究真空环境下不同微波干燥条件对草莓脯质地和营养品质的影响,本文以热风干燥为对照,对3种真空微波处理条件(2.5 w/g-1.5 h、3.5 w/g-1 h、4.5 w/g-0.5 h)获得的草莓脯的水分迁移特性、质构特性、微观结构、色泽及花色苷和酚类物质进行了测定。结果显示,真空微波干燥将草莓脯干燥至含水量20%±2%所需时间显著低于热风,微波功率越大,干燥时间越短。另外,干燥后获得的草莓脯中水分主要呈现结合水与不易流动水2种状态。真空微波干燥获得草莓脯的弛豫时间T2随微波功率增加而增大,说明水分自由度增加;横截面显微观察发现,真空微波干燥使细胞壁发生破裂,微波功率越大,裂隙形成部位越靠近髓芯,裂隙越大,孔隙率越小,而热风干燥的样品细胞完整性、孔隙率高于微波干燥。另外,真空微波干燥的草莓脯硬度、粘力、a^(*)值均低于热风干燥的样品,但L^(*)值、总糖、花青素以及酚类物质的含量均较高。综上所述,真空微波干燥具有更高的干燥效率,并能更好保留草莓脯中花色苷等营养物质。

To investigate the effects of different microwave drying conditions on the texture and nutritional quality of candied strawberries in a vacuum environment.This study investigated the effects of three different vacuum microwave treatment conditions(2.5 w/g-1.5 h,3.5 w/g-1 h,4.5 w/g-0.5 h)on moisture migration characteristics,texture,microstructure,color,anthocyanins,and phenolics of candied strawberries,which were evaluated by hot air drying.The results showed that the time required for vacuum microwave drying to dry candied strawberries to 20%±2%moisture content was significantly lower than that of hot air,and the higher the microwave power,the shorter the drying time.In addition,the water in the candied strawberries obtained after drying mainly appeared in two states,namely,bound water and water not easy to flow.The relaxation time T2 of strawberry candied strawberries obtained by vacuum microwave drying increased with the increase of microwave power,which indicated that the degree of freedom of water increased.Cross-sectional microscopic observation found that vacuum microwave drying caused cell wall rupture,and the higher the microwave power,the closer the site of fissure formation to the medullary core,and the bigger the fissure,and the smaller the porosity,whereas the cellular integrity and the porosity of the samples dried by the hot air were higher than that of microwave drying.In addition,the hardness,viscosity,and a^(*)value of vacuum microwave-dried dried strawberry preserves were lower than those of hot air-dried samples,but the L^(*)value,total sugar,anthocyanin,and phenolic content were higher.In conclusion,vacuum microwave drying had higher drying efficiency and could better retain the nutrients such as anthocyanins in candied strawberries.