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In order to explore the effect and the corresponding physiological mechanisms of UV-C irradiation on browning of fresh-cut apples, both whole and sliced apple were irradiated with UV-C (254 nm) for 5 min before or after processing. The browning index (BI) of slices was immediately measured, while other relevant physiological parameters were evaluated on quick-frozen samples during refrigerated storage. Results indicated that both pre-and post-processing UV-C treatments effectively delayed browning of apple slices; nevertheless, post-processing UV-C treatment was more efficient. BI significantly negatively correlated with non-enzymatic capacities, and activities of catalase, ascorbate peroxidase, and glutathione reductase (GR). BI was positively correlated with the contents of H 2 O 2 and malondialdehyde (MDA). These findings suggested that UV-C treatment delayed browning of apple slices during cold storage by improving the antioxidant system. Post-processing UV-C treatment was more efficient than pre-processing. Practical applicationsUV-C treatment is a technique of preservation for fresh-cut fruits. It is widely applied in food processing and many other fields due to its convenience, safety, low cost, etc.In the present study, both pre-and post-processing UV-C (254 nm) irradiation for 5 min could (1) delay the browning of fresh-cut apple, (2) improve the polyphenol oxidase activity and reduce the phenylalanine ammonia-lyase (PAL) activity and total phenolic content (TPC), and (3) reduce the accumulation of H 2 O 2 and malondialdehyde, and increase the antioxidant activities of fresh-cut apples. Thus, UV-C treatments maintain the fresh-cut quality of fresh-cut apple slices and extend their shelf life.

Apple juice that is designated ‘Not from concentrated’ (NFC) is now increasingly popular with consumers due to its unique taste and rich nutritional value. However, layered precipitation and instability have emerged as serious technical problems that restrict the viability of the NFC apple juice industry. This study researched the influence of water-cored ‘Fuji’ apple fruit storage under different temperatures (0, 20 °C) and times (0, 9, 18, 30, 60 days) on the turbidity stability of NFC apple juice. Changes in the physicochemical properties (juice yield, pH, total soluble solids and titratable acid), turbidity stability (turbidity and particle size) and precipitation sensitive substances (insoluble starch, total phenolics, soluble protein and pectin) of NFC apple juice were determined, combined with the respiratory rates and ethylene release of apples, in order to study post-harvest regulation and control of processed fruit. Results indicated that fruit storage temperature and time significantly guided the turbidity stability of NFC apple juice. As a typical respiratory climacteric fruit, apple fruit stored 45 days at 0 °C and 15 days at 20 °C gained the best juice stability, respectively. This is basically consistent with the respiratory peak of fruit when processing raw materials. During the post-ripening process, the insoluble starch in apple gradually hydrolyzed into fructose and glucose, while total phenolics diminished and water-soluble pectin content increased. On the other hand, the amounts of pectin, soluble protein and phenolics in fruit juice declined as the fruit aged in the late storage period (stored 75 days at 0 °C and 40 days at 20 °C). Meanwhile particle size became larger and the turbidity stability of cloudy juices also decreased. This study’s results will provide a sound theoretical basis for improving the turbidity stability of NFC apple juice by regulating the physiological state of processed raw materials.

The purpose of this work was to elucidate the influence of TF (5 ± 5 °C, and 5 ± 1 °C) and CT (5 ± 0.1 °C served as an isothermal state) storage environment on the antioxidant ability and energy metabolism in post-harvest apple fruit during storage. Specifically, compared with fruit in TFs groups, the quality attributes of apples in the CT group, including firmness, fresh weight, contents of SSC, and TA were maintained at a higher level. In addition, fruit stored in the CT environment revealed a suppressed respiration rate and EL, lower MDA, O2·−, and H2O2 accumulation but increased the activities of SOD, CAT, APX, and GR. At the end of storage, the SOD, CAT, APX, and GR activities of fruit in the CT group were 38.14%,48.04%, 115.29%, and 34.85% higher than that of the TF5 group, respectively. Fruit in the CT environment also revealed higher AsA, GSH, total phenols, and total flavonoid content. In addition, fruit stored in the CT environment maintained higher ATP content, EC, and more active H+-ATPase, Ca2+-ATPase, CCO, and SDH. At the end of storage, the SDH and CCO activities of fruit in the TF0.1 group were 1.74, and 2.59 times higher than that in the TF5 group, respectively. Taken together, we attributed the fact that a constant temperature storage environment can retard the fruit senescence to the enhancement of antioxidant capacities and maintaining of higher energy status in apple fruit.