## 2 Materials and Methods
### Fruit Quality  
Soluble solids were determined using a hand-held explicit sugar meter PAL-1 (ATAGO Co., Ltd., Tokyo, Japan). Eight fruit were randomly selected from each group. After the fruit were transported to the laboratory, they were peeled, cut across the diameter into 3-5 g slices, and dried at 65 \({}^{\circ}\)C to a constant weight. The dry matter content was calculated as follows [38]:  
\[\text{Dry matter (\%) = fruit dry weight (g)/fruit fresh weight (g) \(\times\) 100} \tag{1}\]  
Calculations were repeated 5 times for each method.  
AsA was measured by the 2,6-dichlorophenol indophenol titration method using three replicates [39], and fruit firmness was determined by randomly selecting 5 fruit from  
Figure 1: The daily mean temperature of sampling period in Fengxin County.  
each group. Fruit were washed and the skin was dried, followed by the removal of the pericarp. The firmness was measured at the same site in each fruit. A texture analyzer SMSTA-XTPlus (Stable Micro System Co., Ltd., Surrey, UK) was employed to assess fruit firmness with the following parameters: probe size, 2 mm (diameter) \(\times\) 24.5 mm (length); drilling, 6 mm; test rate, 1 mm/s; test mode, TPA. The fruit were rotated 90\({}^{\circ}\) after every measurement and 5 fruit were measured. Based on the characteristic curve of puncture firmness, the parameters of flesh firmness and cohesiveness were calculated [40]. The soluble sugar content was detected using the improved anthrone colorimetric method [41]. The method of titratable acid referred to the report of [PERSON] et al. [42].  
Aroma substances were determined by weighing 6 g kiwifruit flesh tissues from frozen samples and grinding them into a powder with liquid nitrogen. The samples were placed in a 20 mL headspace bottle. Then, 5 mL saturated sodium chloride solution was added, and the bottle was sealed. After equilibrating in water at 40 \({}^{\circ}\)C for 10 min, 65 \(\upmu\)m PDMS/DVB (Supelco Co., Ltd., Bellefonte, PA, USA) was extracted with an extraction needle at 250 \({}^{\circ}\)C for 30 min. Then, the extraction needle was inserted into an injection port of an Agilent 7890A-5975 gas mass spectrometer (Agilent Inc., Santa Clara, CA, USA) for 5 min. The chromatographic column was a DB-WAX capillary column (30 m \(\times\) 0.25 mm \(\times\) 0.25 \(\upmu\)m) (Agilent Inc., Santa Clara, CA, USA). The condition of the gas chromatography-mass spectrometry (GC-MS) gas phase and mass spectrometry were set as previously reported by [PERSON]: the spectra of unknown compounds were searched using a computer and matched with the NIST14 mass spectrometry database to determine the chemical constituents of volatile substances (material characterization); Normal-alkane of C7-C40 was determined and analyzed in the same way as the sample, and the Kovats Index (KI) of compounds was calculated according to the results of n-alkanes and compared with the values in the reference. KI was calculated in the equation; under the same GC-MS procedure, KI was compared with the retention time of the standard materials. The relative content of each component was acquired based on the peak area normalization method (quantitative method) [43; 44].  
\[\text{KI}(x)=100\times\text{n}+\frac{\text{RT}(x)-\text{RT}(\text{n})}{\text{RT }(\text{n}+1)-\text{RT}(\text{n})}\times 100 \tag{2}\]  
In the equation, KI (\(x\)) represents the Kovats retention index of substance \(x\), RT (\(x\)) represents Kovats retention time of substance \(x\), and RT (\(\text{n}\)) and RT (\(\text{n}+1\)) represents retention time of n and n + 1 alkane carbon atoms.