声热联合杀菌对NFC橙汁低温贮藏营养和感官品质的影响

为了探究声热联合杀菌（thermosonication，TS）对非浓缩还原（not from concentrate, NFC）橙汁品质的影响，研究比较了传统巴氏杀菌（70 ℃，15 min）和TS（600 W，60 ℃，13 min）对贮藏期间NFC橙汁的微生物、色泽、柠檬苦素、诺米林、维生素C (vitamin C, Vc)、总酚、总黄酮含量，以及抗氧化活性的影响，并采用GC-MS分析评价2种杀菌方式对NFC橙汁风味的影响。结果表明，在贮藏期间，2种杀菌方式下NFC橙汁中菌落总数以及霉菌和酵母菌均符合国家标准，糖酸成分稳定，TS处理不影响NFC橙汁的酸甜口感。与传统巴氏杀菌处理NFC橙汁相比，TS处理提高了NFC橙汁的浊度稳定性和色泽，褐变指数降低了12.50% ～16.67%，Vc的损失率减少了10.52%，总酚和总黄酮含量是传统巴氏杀菌组的1.00～1.06倍，柠檬苦素含量和诺米林含量分别降低了17.37%～56.62%和9.32%～63.85%，DPPH自由基清除能力和铁离子还原能力分别是巴氏杀菌的1.09～1.21倍和1.11～1.70倍。通过GC-MS分析共鉴定出49种挥发性风味物质。NFC橙汁经传统巴氏杀菌处理后产生1-辛烯-3-醇、2-辛炔-1-醇、丁酸乙酯、反-2-辛烯醛、反-2-壬烯醛、反-2-庚烯醛、水芹醛、6-甲基-5-庚烯-2-酮以及丁酸9种挥发性成分，导致NFC橙汁产生热异味；而TS处理能够有效抑制NFC橙汁产生这些成分，从而避免NFC橙汁产生热异味。因此，声热联合杀菌是一种优于或可代替NFC橙汁传统巴氏杀菌的杀菌方式，该研究为声热联合杀菌技术在NFC橙汁的应用提供理论依据和技术参数。

Effects of thermosonication on the nutritional and sensory quality of NFC orange juice during storage at low temperature

Not from concentrate (NFC) orange juice is processed directly from the fresh orange after cleaning, sterilized and aseptically filled, because it does not go through the process of concentration, reduction and preparation, so as to maintain the original flavor and nutrition of the fruit. Sterilization is the most significant processing step in juice production, which can effectively prolong the shelf life of citrus juice through killing microorganisms. Currently, pasteurization is a kind of widely used thermal sterilization techniques in the industry and is also widely used in the manufacture of liquid foods. However, high temperatures inevitably have some negative effects, such as causing deterioration of color and even odor, changing the physicochemical properties, and reducing the heat-sensitive nutritional and functional components in the juice, which may be detrimental to the health of consumers. Therefore, there is an urgent need to systematically compare the influences of different sterilizations on the quality of NFC orange juice and select suitable sterilization methods for processing high-quality NFC juice. Thermosonication (TS) technology, as a low heat sterilization technology, has been widely concerned in the sterilization of liquid food. In order to evaluate the efficiency of TS on the quality of NFC orange juice, the effects of TS (600 W, 60 ℃, 13 min) on the microorganisms, color, limonin, nomilin, vitamin C, total phenol, total flavonoid content and antioxidant activity of NFC orange juice were investigated during storage at low temperature for 35 days compared to the traditional pasteurization (70 ℃, 15 min), and the changes in volatile compounds of NFC orange juice with traditional pasteurization and TS were also analyzed by GC-MS. The results showed that both treatments effectively ensure the microbiological safety of NFC orange juice during storage. The sugar and acid components of NFC orange juice were stable during storage, and TS treatment did not affect the taste of NFC orange juice. Compared with the traditional pasteurization group of NFC orange juice, TS treatment improved the turbidity stability of orange juice. With the extension of storage time, TS treatment increased the L*, a* and b* values. However, the ΔE* values were all less than 1.00, the color difference could not be perceived, and the BI value decreased by 12.50% ～16.67%. The loss rate of Vc in NFC orange juice was reduced by 10.52% of TS group. The contents of total phenol and total flavone of TS group were 1.00-1.06 times of those in the traditional pasteurization group. The limonin content decreased by 17.37%～56.62% and nomilin content decreased by 9.32%～63.85%, respectively. The DPPH free radical scavenging ability and FRAP total antioxidant capacity were 1.09～1.21 times and 1.11～1.70 times that of pasteurization, respectively. GC-MS analysis identified 49 volatile compounds. The traditional pasteurization process produced 1-octene-3-ol, 2-octene-1-ol, 2-octyne-1-ol, ethyl butyrate, (E)-2-octenal, (E)-2-nonenal, (E)-2-heptenal, creinaldehyde, 6-methyl-5-heptene-2-ketone and butyric acid in the NFC orange juice, which were the mainly volatile components that caused the hot odor of NFC orange juice, but TS effectively inhibited to produce these volatile components in NFC orange juice, thus avoiding the hot odor of the juice. Therefore, TS was better than traditional pasteurization for preserving the nutritional and sensory quality of NFC orange juice. It was suggested that TS might be a promised and alternative sterilization for NFC orange juice. The research can provide theoretical basis and technical parameters for further improving the application of NFC orange juice.