Study On The Effect And Mechanism Of Secondary Metabolism Regulator, Combination Of Modified Atmosphere And Moisture Loss On Preservation Of Green Walnut Fruit

To investigate the effect of modified atmosphere packaging on the fresh walnut(Juglans regia L.) preservation of physiological mechanism through secondary metabolism regulation. Green walnut fruits cv.Luguang were slected as meterial and accepted the treatment of ethephon, growth regulator(1-MCP, IBU, PAC), then were stored at(0±0.5)℃, RH 70-80%. Biological changes and preservation effect were measured during storage. To develop a simple and feasible method for fresh walnut preservation, fruits cv.Xifu No.2 also accepted combination treatment of moisture loss 0, 5%, 10% and modified atmosphere packaging(MAP). All the results show as following:(1) The treatments of 10, 500mg/L ethephon effectively reduced decay incidence of fresh walnut. Decay incidence of fresh walnut was 18.5%,12.5%、33.5%,respectivly, control was 26% after 42 day storage. 10, 500mg/L ethephon treatments kept a higher firmness of fresh walnut, total phenols contents, phenylalanine ammonia-lyase(PAL) activity and lower polyphenol-oxidase(PPO) and peroxidase(POD) activities of green husk than that of control. On day 18 and 36, the total phenols contents of green husk were 500mg/L ethephon>10mg/L ethephon>CK>8000mg/L ethephon. During the storage of green fresh walnut, 500mg/L ethephon treatment showed a lower oil content, acid value(AV) and peroxide value(PV) in walnut kernels than that of other treatments and control. While treatment of 8000mg/L ethephon showed an opposite effect.(2) Combination of three inhibiters(1-MCP, IBU, PAC), with MAP increased the first respiration peak of fresh walnut and made the second peaks appeared early. On day 30, the respiration of PE50+IBU treatment was 54.9mg/kg.h, and control was 9.1 mg/kg.h. Compared with the PE50, three inhibiters treatments decreased the PAL acticity and increased the PPO, POD activity and total phenols of green husk. They also increased the MDA content and LOX activity of green walnut husk in the first day 24 and decreased the Vc content and dehydroascorbate reductase(DHAR) activity of green huask after the day 24. Among the treatments and control, PE50+IBU showed the strongest effect on each above change of fresh walnut.(3) The effect of 10% moisture loss rate combined with PE50 packaging(10%+PE50) was the strongest among 6 combinations of modified atmosphere and water loss, 5%+PE30 was the second. After 80-day storage, fruit cracking rate, decay incidence and browning index of green walnut fruit from 10%+PE50 was 2.1%, 2.0%, 10%, respectively, but which of control reached 81.6%, 42.4%, 80.0%, respectively. 10%+PE50 resulted highest total phenols, flavonoids content and total antioxidant activity,the best sensory quality the lowest acid value, peroxide value, malondialdehyde(MDA) and H2O2 content in kernel. After 110-day storage, 10%+PE50 reached storage end by giving 11% decay rate. In conclusion, 10% moisture loss rate combined with PE50 was selected optimal parameters for the combination of water loss and modified atmosphere packing. It prolonged refrigeration life of green walnut to 110 d.In summary, adding the appropriate concentration of exogenous ethylene during the storage of green walnut, which can effectively increase the total phenols content, improve the disease resistance and extend the shelf life of fresh walnuts. Also, Treatments of inhibiting ethylene, jasmonic acid, salicylic acid decreased the effect of PE50 on the fresh walnut preservation. The effect of PE50+IBU was biggest among all the treatments. The study also found that 10% moisture loss rate combined with PE50 packaging can effectively maintain a better walnut kernel and extend the storage life during the prestorage of fresh walnut.