The Chinese bayberries (Myrica rubra Sieb. & Zucc., cv. Dongkui) fruit were harvested manually from a commercial orchard in Xianju county of Zhejiang Province, China on June 28, 2010, and then transported to the laboratory by a refrigerated car within 3 hours. Fruit were selected for uniformity of shape and color and the blemished and diseased fruit were discarded.
Fruit treatments were performed in a hypobaric storage system with storage chambers whose pressure could be set independently (Model XL-5, Xianlv Low-pressure Fresh Keeping Equipment Co. Ltd., Shanghai, China). Each replicate containing 2 kg fruits was put in a plastic basket and placed into the hypobaric chamber. The applied pressures were set to be 85±5, 55±5 and 15±5 kPa, respectively. The normal atmospheric pressure (101.3 kPa) was used as control. These fruit were stored at 1±0.5°C and 85–90% relative humidity (RH). Fruit samples were taken for analysis every 3 days in the storage period of 15 days.
Evaluations of fruit decay and skin colour
Fruit decay was visually evaluated. Fruit with visible mold growth with about 2% of the surface affected was considered rotten. The severity of fruit decay was expressed as percentage of fruit showing decay symptoms. Skin colour of 20 fruit from each replicate was measured using a colorimeter (Konica Minolta, CR-400, Japan) with a 6-mm aperture size, which provided L* and a* values according to the system established by the Commission Internationale de L’Eclairage (CIE, International Commission on Illumination). A reference white tile was used for calibration.
Measurements of respiration and ethylene production rates
Ten fruit were enclosed in 250 mL glass jars at 5°C for 2 h and then 2 mL of headspace gas were taken from each jar. CO2 amount was measured by gas chromatography (Rainbow, SP-9890, China) equipped with flame ionization detector and a packed column (GDX-502, Zhonghuida Inc., China). Ethylene concentration was analysed by gas chromatography using a flame ionization detector. Respiration and ethylene production rates were expressed as mg CO2 and μg per hour on fresh weight basis, respectively.
Measurements of total soluble solids and titratable acidity
Fifty fruit from each treatment were taken. Juice was obtained by a juicer (HR1861, Philips Co. Beijing, China), followed by filtration through cheesecloth. The juice was analyzed for total soluble solids (TSS) and titratable acidity (TA). TSS concentration was determined by a portable refractometer (Atago PAL-1, Japan) while TA content was measured by titrating 20 mL of the juice to pH 8.2 using 0.1 mol L-1 NaOH.
MDA content determination
MDA content was determined according to the method described by Li et al.  with some modification. Fruit tissues (1 g) were extracted for 2 h with 5 mL of trichloroacetic acid (10%). Three milliliters of 0.5% thiobarbituric acid (TBA) in 10% trichloroacetic acid were added to 1 mL of the extract. The solution was heated in a boiling water bath for 20 min, then immediately cooled, and finally centrifuged at 6000 × g for 10 min to clarify the solution. Absorbance was measured at 532 and 600 nm. MDA content was expressed as μmol/g FW by the method of Li et al. .
Enzymatic activity assay
Five grams of fruit tissues were homogenized in 25 mL of 100 mmol L-1 Tris-HCl buffer (pH 7.8) containing 2 mmol L-1 EDTA and 2 mmol L-1 1,4-dithiothreitol at 4°C. The homogenate was centrifuged at 15,000 × g for 15 min at 4°C, and then the supernatant was collected for the enzymatic activity assay. Protein was measured according to the method of Bradford , using bovine serum albumin (BSA) as the standard.
CAT was analyzed according to the method of Beers & Sizer  with some modifications. The disappearance of H2O2 was monitored by measuring the decrease in absorbance at 240 nm of a reaction mixture containing 100 mmol L-1 Tris-HCl buffer (pH 7.8), 25 mmol L-1 H2O2, and 0.2 mL of crude enzyme extract. One unit of enzymatic activity was defined as 0.01 change of absorbance at 240 nm per minute. Specific CAT activity was expressed as units per mg protein. POD activity was assayed according to the method described by Yang et al. . The reaction mixture (2 mL) consisted of 50 mmol L-1 sodium phosphate buffer (pH 6.5), 6 mmol L-1 guaiacol and 4.5 mmol L-1 H2O2 prior to the addation of 1 mL of crude enzyme extract. Increase in absorbance at 470 nm at intervals of 30 s was recorded. One unit of enzymatic activity was defined as the amount of enzyme that catalyzed the peroxidation of 1 mmol of guaiacol per minute. Specific POD activity was expressed as units per mg protein.
Total phenolic content determination
One gram of lyophilized fruit tissues was extracted with 25 mL of ethanol for 3 h. Total phenolic contents were estimated colourimetrically using the Folin-Ciocalteu method . The extract was appropriately diluted, and then 1 mL of the dilution was oxidized with 0.5 mL of Folin-Ciocalteau reagent. The reaction was neutralized with 5 ml of 5% Na2CO3. The solution was immediately diluted to a final volume of 25 mL with distilled water and then mixed thoroughly. The absorbance was read at 765 nm after 1 hour of incubation in dark at 25°C using a spectrophotometer (Shimadzu UV-2550, Japan). Gallic acid was used as a standard, and phenolic contents were expressed as mg gallic acid equivalents (GAE)/g FW.
The ferric reducing ability of the Chinese bayberry was measured according to the method of Benzie & Strain . To prepare the FRAP reagent, a mixture of 0.3 mol L-1 acetate buffer (pH 3.6), 10 mmol L-1 tripyridyltriazine (TPTZ), and 20 mmol L-1 ferric chloride (10:1:1, v/v/v) was made. One gram of lyophilized fruit tissues was extracted for 12 hours with 20 mL of ethanol. The FRAP reagent (3.9 mL) was added to the extract solution sample (0.1 mL) and then mixed thoroughly. The reaction was then monitored for 10 min at 37°C and the absorbance was recorded at 593 nm on the Shimadzu UV-2550 spectrophotometer. The ferric reducing ability of the Chinese bayberry fruit was expressed as mmol FeSO4 per litre crude extract.
All samples were prepared and analysed in triplicate. Statistical analysis was done with one-way analysis of variance using the SAS statistical software package.