Effects of CO2 pretreatment on the volatile compounds of dried Chinese jujube (Zizyphus jujuba Miller)

Abstract The aim of this study was to investigate whether anaerobic metabolites could induce volatile compounds and improve aroma of dried jujube (Ziziphus jujuba Miller). Jujube fruits were incubated in a polyvinyl chloride bag containing 5% CO2 and 95% N2 for up to 168 h at 25 °C and 3 samples were randomly removed every 6 h and oven dried to a moisture content of ≅ 20%. The volatile compounds of control and 5% CO2-pretreated Chinese jujube fruits were extracted by simultaneous distillation extraction and identified by gas chromatography-mass spectrometry(GC-MS). The acetaldehyde and ethanol contents were determined by gas chromatography (GC). The results indicated that a large accumulation of acetaldehyde and ethanol caused changes in aroma composition of dried jujube products and 5% CO2 pretreatment led to an increase in the levels of some compounds, particularly esters, acetaldehydes, and ethanol, whereas the amount of acids were decreased significantly. Principal component analysis showed that integrative scores of 5% CO2 pretreatment at 120 h were the highest, and aroma quality was better than that of the control. Relatively low concentrations of anaerobic respiration metabolites are good for jujube fruit aroma composition.

摘要
本研究旨在探讨厌氧代谢物是否可诱导挥发性化合物生成并改善干燥枣（Ziziphus jujuba Miller）的香气品质。将枣果置于充有5%二氧化碳（CO₂）与95%氮气（N₂）的聚氯乙烯袋中，于25℃条件下培养至多168小时；每隔6小时随机取出3份样品，经烘箱干燥至含水量约为20%。采用同时蒸馏萃取法提取对照组与5% CO₂预处理枣果的挥发性化合物，并通过气相色谱-质谱联用（GC-MS）进行定性鉴定；采用气相色谱（GC）测定乙醛与乙醇的含量。结果显示，乙醛与乙醇的大量积累会改变干燥枣制品的香气组成；5% CO₂预处理可提升部分化合物的含量，尤以酯类、乙醛及乙醇最为显著，而酸类物质的含量则显著下降。主成分分析结果表明，5% CO₂预处理120小时的样品综合得分最高，其香气品质优于对照组。厌氧呼吸代谢物的适宜低浓度有助于优化枣果的香气组成。