Abstract

The effects of combined humid-convective drying (CHCD) on quality attributes of shiitake mushrooms regarding surface color, microstructure, texture, volatile compounds, and polysaccharides were investigated. Initially, mushrooms were subjected to various hot air drying (HAD) procedures, and the influential parameters (initial temperature, relative humidity [RH], and time) were optimized based on highest yield of polysaccharides. Among them, nonuniform drying was selected to design CHCD, with final parameters—initial temperature: 40 °C, maximum temperature: 60 °C, RH: 30%, and time: 28 h. CHCD produced shiitake mushrooms with less surface color changes (p < 0.05), softer texture, and less shrinkage (47.1 ± 1%) than conventional HAD. Scanning electron microscopy results showed a honeycomb-like pore-network in CHCD samples. The yield of polysaccharides, predominantly β-glucans as detected by MALDI-TOF and CP-MAS NMR, was 12.3 ± 0.5 g/100g in CHCD samples, significantly higher than conventional HAD (p < 0.05). A total of 51 significant volatile compounds were detected with higher concentration in CHCD compared with HAD samples using GC × GC-QTOF. Along with increasing shelf-life, CHCD process produces dry mushrooms with lower surface color changes, good preservation of internal structure, softer texture, lesser shrinkage, increased rehydration, increased content of polysaccharides, and volatile compounds compared with conventional HAD.

摘要

研究了湿对流联合干燥 (CHCD) 对香菇表面颜色、微观结构、质地、挥发性化合物和多糖等品质属性的影响。最初，蘑菇经过各种热风干燥 (HAD) 程序，并根据多糖的最高产量优化影响参数（初始温度、相对湿度 [RH] 和时间）。其中，选择不均匀干燥设计CHCD，最终参数——初始温度：40℃，最高温度：60℃，相对湿度：30%，时间：28h。CHCD 生产的香菇表面颜色变化较少（p < 0.05)，质地更柔软，收缩率比传统 HAD 更小 (47.1 ± 1%)。扫描电子显微镜结果显示 CHCD 样品中存在蜂窝状孔隙网络。通过 MALDI-TOF 和 CP-MAS NMR 检测到的多糖产量，主要是 β-葡聚糖，在 CHCD 样品中为 12.3 ± 0.5 g/100g，显着高于常规 HAD ( p  < 0.05)。与使用 GC × GC-QTOF 的 HAD 样品相比，在 CHCD 中检测到的总共 51 种重要的挥发性化合物的浓度更高。随着保质期的延长，CHCD 工艺生产的干蘑菇与传统的 HAD 相比，表面颜色变化更小、内部结构保持良好、质地更柔软、收缩更小、补水增加、多糖含量和挥发性化合物含量增加。