干燥方法对印度块菌(Tuber indicum)品质的影响

为了解不同干燥方法对印度块菌干后品质及微观结构的影响,本研究采用热风干燥、真空冷冻干燥方法对印度块菌进行处理,以感官品质(色泽、质构)、复水特性、营养成分(还原糖、总蛋白、维生素C、总黄酮)及微观结构为评价指标,评价干燥方法对印度块菌品质的影响,并利用低场核磁共振技术研究干燥处理期间水分的迁移率和分布。结果表明,与热风干燥比,真空冷冻干燥产品L*高,a*低,能够较好维持产品色泽,热风干燥产品褐变严重,且真空冷冻干燥产品硬度低,脆性高。真空冷冻干燥产品复水比及复水速率显著高于热风干燥产品(P<0.05),干燥10 min后,冷冻干燥复水比值为3.00,显著高于热风干燥(2.26)(P<0.05),冷冻干燥复水速率(0.30 min-1)显著高于热风干燥(0.22 min-1)(P<0.05)。与新鲜样品比,两种干燥产品中总蛋白含量无显著变化,维生素C、还原糖及总黄酮保留量显著降低(P<0.05);与热风干燥产品比,真空冷冻干燥产品维生素C、还原糖及总黄酮保留量显著高于热风干燥产品(P<0.05)。低场核磁共振分析表明,冷冻干燥组T₂₃水分信号强度衰减速率高于热风干燥组,说明真空冷冻干燥效率更高。扫描电镜观察微观结构发现热风干燥产品细胞组织收缩、塌陷且结构很致密,真空冷冻干燥产品呈现多孔结构。综合分析,干燥对印度块菌干制品的营养及品质影响较大,真空冷冻干燥更适合印度块菌产品的干燥加工,本研究为提高印度块菌干制品加工品质提供理论依据。

Effects of Different Drying Methods on Quality of Tuber indicum

In this research,hot air drying and vacuum freeze drying were used to dry fresh Tuber indicum slices,and the effects of different drying methods on qualities and microstructure of Tuber indicum were investigated. Then sensory quality(color,texture),rehydration characteristics,nutritional ingredients(reducing sugar,total protein,vitamin C,total flavonoids)and microstructure were used as evaluation indexes to study the impact of drying methods on the quality of Tuber indicum. After that,the mobility ratio and distribution of moisture during the drying were studied by low field MRI. The results showed that L* was higher and a* was lower in the vacuum freeze drying products,the color of which could be well preserved. The browning degree of the hot air drying products was higher. Vacuum freeze drying products had lower hardness and high fragility. Hot air drying products had high hardness and low fragility. Besides,the rehydration ratio and speed of vacuum freeze drying products were significantly higher than those of hot air drying products. After 10 min of drying,the rehydration ratio of vacuum freeze drying was 3.00,which was significantly higher than that of hot air drying(2.26)(P<0.05).The rehydration speed of freeze drying was 0.30 min-1 and significantly higher than that of hot air drying(0.22 min-1)(P<0.05). No significant change was found in the total protein content of the Tuber indicum after drying,the retaining quantity of vitamin C,reducing sugar and total flavonoids of drying products were significantly lower than fresh Tuber indicum. The retaining quantity of vitamin C,reducing sugar and total flavonoids in vacuum freeze drying products was significantly higher than that in hot air drying products(P<0.05).The low field MRI was found that T₂₃ signal intensity attenuation rate of vacuum freeze drying products was higher than those of hot air drying products,vacuum freeze drying had higher efficiency. SEM observation of the microstructure showed that the cell tissue of hot air drying products was contracted and collapsed,and the structure was very dense,while the vacuum freeze drying products showed porous structure. The aggregate analysis shows that vacuum freeze drying is more suitable for drying and processing of Tuber indicum products. This research provides a theoretical basis for improving the processing quality of Tuber indicum drying products.