关键词: 核桃青果, 薄膜包装贮藏, 采后生理, 品质

Abstract:

The effect of modified atmosphere packaging (MAP) with three different thicknesses of PE films, PE30 (30 μm),
thk-PE (45 μm) and PE50 (50 μm), or mulch plastic film (6 μm) as control was examined on the postharvest physiology and
preservation of green walnut fruit (cultivar Xifu No. 2) during storage at 0–1 ℃. Gas concentrations in the sealed bags and
respiration rate, ethylene production rate and decay index of the fruit were measured at regular intervals. Acid value, peroxide
value and free fatty acid content of the kernel as well as water content of the peel and kernel were also determined after 0 and
60 days of storage. Results showed that all three PE films delayed the first respiratory peak and restrained the second one as
well as ethylene production peak, and gas concentrations in all the bags reached equilibrium after 15 days. Among them, PE50
had the strongest capability of automatic atmospheric modification, providing 4.5%–5.0% O2 and 5.3%–5.7% CO2. After 60
days of storage, the peel and kernel of walnuts packaged with the three PE bags showed a significantly lower water content
than those packaged with the control film (P ＜ 0.05), in addition to a significant decrease in decay index as well as kernel acid
value and peroxide, with the increasing order for all these indicators: PE50 ＜ thk-PE ＜ PE30. However, kernel free fatty acid
contents followed the decreasing order: PE50 ＞ thk-PE ＞ PE30. From this study, it is concluded that PE50 is more effective at
delaying the decay of MAP packaged green walnut fruit than thk-PE and preserving the quality and nutrients of walnut kernel.

Key words: green walnut fruit, film packaging and storage, postharvest physiology, quality traits