不同预处理方式对热风干燥黄花菜褐变及干燥特性的影响

Effects of Different Pretreatment Methods on Browning and Drying Characteristics of Hot Air-Dried Daylily Buds

本实验探究不同护色液(0.1 g/100 mL柠檬酸、0.2 g/100 mL柠檬酸、0.2 g/100 mL碳酸氢钠、1.0 g/100 mL氯化钠溶液,浸泡45 min)对烫漂(蒸汽和热水,处理2 min)处理后黄花菜成品褐变抑制及干燥特性的影响,对其干制品外观色泽、营养成分和微观结构进行表征,同时采用傅里叶变换红外光谱法比较不同预处理对其结构的影响,并通过主成分分析获取具有较高商品价值的黄花菜干燥预处理条件。结果表明,抑制褐变效果方面:蒸汽烫漂>热水烫漂;0.2 g/100 mL柠檬酸溶液>0.1 g/100 mL柠檬酸溶液>1.0 g/100 mL氯化钠溶液>0.2 g/100 mL碳酸氢钠溶液。干燥处理效果方面:采用0.2 g/100 mL柠檬酸溶液进行护色处理的黄花菜干燥速率最快且复水效果较好;综合考量,以蒸汽烫漂(2 min)+0.2 g/100 mL柠檬酸溶液浸泡(45 min)条件进行预处理后,黄花菜干制品的外观色泽、黄酮与多酚含量及微观结构等品质较佳。经主成分分析可知,多酚含量、5-羟甲基糠醛含量与色差、褐变度高度相关,咀嚼性与硬度相关性最高。从8个主成分中提取出的2个主成分(第1主成分包括多酚含量、褐变度与色差,第2主成分包括硬度、5-羟甲基糠醛含量)能较好地反映黄花菜品质的综合信息。本研究可为黄花菜深加工提供一定的理论和技术参考。

This experiment investigated the effects of soaking treatment(for 45 min) with different color fixatives(0.1 g/100 mL citric acid,0.2 g/100 mL citric acid,0.2 g/100 mL sodium bicarbonate,and 1.0 g/100 mL sodium chloride solution) after blanching for two minutes on the browning inhibition and drying characteristics of daylily buds during hot air drying.The color,nutrient composition and microstructure of dried products were characterized,and the chemical structure was analyzed by Fourier transform infrared(FTIR) spectroscopy.The pretreatment conditions for dried daylily buds with improved commodity value were determined using principal component analysis(PCA).Results showed that the browning inhibitory effect of steam blanching was better than that of hot water blanching.The decreasing order of the browning inhibitory effects of color fixatives was 0.2 g/100 mL citric acid solution 0.1 g/100 mL citric acid solution 1.0 g/100 mL sodium chloride solution 0.2 g/100 mL sodium bicarbonate solution.Daylily buds pretreated with 0.2 g/100 mL citric acid solution showed the highest drying rate,and the dried product had high rehydration ratio.Collectively,the dried product prepared by steaming followed by soaking with 0.2 g/100 mL citric acid solution had good quality with respect to color,flavonoid and polyphenol contents and microstructure.PCA indicated that the contents of polyphenols and 5-hydroxymethylhydrate were highly correlated with color and browning degree,and chewiness had the highest correlation with hardness.Out of the eight principal components,two(the first one included polyphenol content,browning degree and color difference,and the second one included hardness and 5-hydroxymethylfurfural content) were extracted,which could well reflect the comprehensive information on the quality of dried daylily buds.This study can provide theoretical and technical references for the deep processing of daylily buds.