真空脉动干燥温度对黄花菜理化性质与微观结构的影响

The Effect of Vacuum Pulsation Drying Temperature on the Physicochemical Properties and Microstructure of Daylily

鲜黄花菜含水率较高,导致采后品质快速下降。探讨适合黄花菜的加工方法对延长黄花菜的货架期非常重要。为探究不同真空脉动干燥(PVD)工艺条件对黄花菜营养成分、色泽、风味、复水率及微观结构的影响,以便提高干制黄花菜品质,选用PVD设备干制黄花菜,研究真空保持时间(10 min)和常压保持时间(5 min)条件下不同干燥温度(65,70,75,80,85℃)对黄花菜品质的影响。采用主成分分析法和偏最小二乘法对黄花菜干燥工艺、风味组成以及特征滋味进行判别分析。结果表明,自然干燥(CK)黄花菜中游离氨基酸含量最多,为0.858 mg/g,△E值最大,为16.47,进一步表明样品整体质量较差。PVD干燥后黄花菜色泽鲜亮,复水性能较好,蛋白质和黄酮含量显著增加。当PVD 80℃时,原色保留率最大(△E=7.28),游离氨基酸含量最高(0.818 mg/g)。当PVD 75℃时,样品中蛋白质(7.331 g/L)和Ga(1072.445μg/kg)含量最高。当PVD 70℃时,黄菜样品中β-折叠和α-螺旋含量占比最多,为35%。当PVD 65℃时,黄酮含量(1.653 mg/g)和复水率最高(3.04%),并且可较好地保留无机硫化物、氮氧化合物及萜类物质。此外,通过偏最小二乘判别分析得出天门冬氨酸、组氨酸、丝氨酸、谷氨酸和丙氨酸为黄花菜特征滋味物质。结论:不同PVD干燥温度导致黄花菜的理化性质和营养成分不同,研究结果可为满足不同质量属性要求和消费者接受度提供适合的工艺参数。

Because the water content of fresh daylily is high,the quality of fresh daylily decreases rapidly after harvest.It is very important to explore the suitable processing methods for extending the shelf life of daylily.The effects of different vacuum pulsating preventive technology(PVD)conditions on nutritional composition,color,flavor,rehydration rate and microstructure of daylily were investigated,so as to improve the quality of dried daylily.The effects of different drying temperatures(65,70,75,80℃ and 85℃)on the quality of daylilies were studied under the conditions of vacuum holding time(10 min)and atmospheric holding time(5 min)using PVD equipment.Furthermore,principal component analysis and partial least squares method were used to discriminate the drying process,flavor composition and characteristic taste of daylily.The results showed that the content of free amino acids in naturally dried(CK)daylily was the highest,at 0.858 mg/g.The △E value was the highest,at 16.47,further indicating that the overall quality of the sample was poor.After PVD drying,daylily has a bright and vibrant color,good rehydration performance,and significantly increased protein and flavonoid content.When PVD was 80℃,the primary color retention rate was the highest(△E=7.28),and the free amino acid content was the highest(0.818 mg/g).When PVD was 75℃,the protein(7.331 g/L)and Ga(1072.445μg/kg)content in the sample was the highest.When PVD was 70℃,the proportion of β-fold and α-helix content in the daylily sample was the highest,at 35%.When PVD was 65℃,the flavonoid content(1.653 mg/g)and rehydration rate are the highest(3.04%),and inorganic sulfides,nitrogen oxides,and terpenoids can be well retained.In addition,partial least squares discriminant analysis revealed that aspartic acid,histidine,serine,glutamic acid,and alanine are characteristic taste substances of daylily.Conclusion:Different PVD drying temperatures lead to differences in the physicochemical properties and nutritional components of daylily.The research results can provide suitable process parameters to meet different quality attribute requirements and consumer acceptance.