Pretreatment combined with vacuum freeze-drying is an effective technique to extend the storage period of jujube fruits and reduce energy consumption and cost; however, the effects of pretreatment on the quality characteristics of jujube during vacuum freeze-drying remain unknown. In this study, the effects of cold plasma (CP), high hydrostatic pressure (HHP), ultrasound (US), high-pressure carbon dioxide (HPCD), and conventional blanching (BC) as pretreatments on the performance of vacuum freeze-dried jujube slices were investigated. The results indicated that the application of different pretreatments decreased the water activity and increased the rehydration capacity, owing to the pretreatment etching larger and more porous holes in the microstructure. Freeze-dried jujube slices pretreated with HPCD retained most of their quality characteristics (color, hardness, and volatile compounds), followed by the HHP- and US-pretreated samples, whereas samples pretreated with BC showed the greatest deterioration in quality characteristics, and hence, BC is not recommended as a pretreatment for freeze-dried jujube slices. Sensory evaluation based on hedonic analysis showed that jujube slices pretreated with HPCD and US were close to the control sample and scored highest. Compared to other pretreated samples and the control, freeze-dried jujube slices pretreated with HPCD showed the least degradation (4.93%) of cyclic adenosine monophosphate (cAMP), the highest contents of total phenol, total flavonoid, and l-ascorbic acid, and the highest antioxidant capacity. Partial least squares-discriminant analysis (PLS-DA) was performed to screen all the quality characteristic data of different pretreated samples, and 12 volatile compounds, including ethyl hexanoate and (E)-2-hexenal, along with color, l-ascorbic acid content, and cAMP content were found suitable to be used as discriminators for pretreated freeze-dried jujube slices. Therefore, non-thermal pretreatments, including HPCD, US, and HHP pretreatments, are promising techniques for the vacuum freeze-drying of jujube products.

预处理结合真空冷冻干燥是延长枣果贮藏期、降低能耗和成本的有效技术；然而，真空冷冻干燥过程中预处理对红枣品质特性的影响尚不清楚。在这项研究中，冷等离子体 (CP)、高静水压力 (HHP)、超声波 (US)、高压二氧化碳 (HPCD) 和常规漂白 (BC) 作为预处理对真空冷冻干燥性能的影响大枣切片进行了调查。结果表明，由于预处理在微观结构中蚀刻了更大和更多的孔洞，因此应用不同的预处理降低了水活度并增加了再水化能力。用 HPCD 预处理的冻干枣片保留了大部分的质量特征（颜色、硬度和挥发性化合物），其次是 HHP 和 US 预处理的样品，而用 BC 预处理的样品在质量特征上表现出最大的恶化，因此，BC不推荐作为冻干枣片的前处理。基于享乐分析的感官评价表明，经 HPCD 和 US 预处理的枣片与对照样品接近，得分最高。与其他预处理样品和对照相比，经 HPCD 预处理的冻干枣片的环磷酸腺苷 (cAMP) 降解最少（4.93%），总酚、总黄酮和总黄酮含量最高。而用 BC 预处理的样品在质量特性方面表现出最大的恶化，因此，不推荐将 BC 作为冻干枣片的预处理。基于享乐分析的感官评价表明，经 HPCD 和 US 预处理的枣片与对照样品接近，得分最高。与其他预处理样品和对照相比，经 HPCD 预处理的冻干枣片的环磷酸腺苷 (cAMP) 降解最少（4.93%），总酚、总黄酮和总黄酮含量最高。而用 BC 预处理的样品在质量特性方面表现出最大的恶化，因此，不推荐将 BC 作为冻干枣片的预处理。基于享乐分析的感官评价表明，经 HPCD 和 US 预处理的枣片与对照样品接近，得分最高。与其他预处理样品和对照相比，经 HPCD 预处理的冻干枣片的环磷酸腺苷 (cAMP) 降解最少（4.93%），总酚、总黄酮和总黄酮含量最高。基于享乐分析的感官评价表明，经 HPCD 和 US 预处理的枣片与对照样品接近，得分最高。与其他预处理样品和对照相比，经 HPCD 预处理的冻干枣片的环磷酸腺苷 (cAMP) 降解最少（4.93%），总酚、总黄酮和总黄酮含量最高。基于享乐分析的感官评价表明，经 HPCD 和 US 预处理的枣片与对照样品接近，得分最高。与其他预处理样品和对照相比，经 HPCD 预处理的冻干枣片的环磷酸腺苷 (cAMP) 降解最少（4.93%），总酚、总黄酮和总黄酮含量最高。l-抗坏血酸，抗氧化能力最高。进行偏最小二乘判别分析 (PLS-DA) 以筛选不同预处理样品的所有质量特征数据，以及 12 种挥发性化合物，包括己酸乙酯和 ( E )-2-己烯醛，以及颜色、l-抗坏血酸含量和 cAMP 含量被发现适合用作预处理冻干枣片的鉴别器。因此，非热预处理，包括 HPCD、US 和 HHP 预处理，是用于枣制品真空冷冻干燥的有前途的技术。