JIA-2019-11

2516 Maratab Ali et al. Journal of Integrative Agriculture 2019, 18(11): 2514–2520 2.5. Determination of acetaldehyde and ethanol Acetaldehyde and ethanol contents were estimated according to method of Botondi et al . (2012), with some modification. A total of 5 g of powdered sample were homogenized with 10 mL of distilled water and centrifuged at 10 000×g for 25 min at 4°C. An aliquot of 5.0 mL of extract was poured into glass tubes after filtration; then caped and sealed with paraffin film. Tubes were heated at 60°C for 1 h in an incubator and 1 mL of headspace air was injected into an 7890A gas chromatograph (Agilent, USA) fitted with electronic ionization detector (at 280°C) and a glass column with 5% Carbowax on 60/80 Carbopack (at 85°C). 2.6. Determination of PDC and ADH activity The activity of PDC and ADH enzymes were measured according to method of Imahori et al . (2002), with slight modi cations: frozen powder sample (6 g) was homogenized in 25 mL of 100 mmol L –1 MES buffer solution (pH 6.5) comprising 1 % (W/V) polyvinylpyrolidone (PVP) and 2 mmol L –1 dithiothreitol. Homogenized sample was filtered by two layers of cheesecloth and then, filtrate was centrifuged at 15000 ×g for 25 min at 4°C. Measurement of the enzymatic activity was conducted by monitoring the NADH oxidation at 340 nm using a spectrophotometer. 2.7. Statistical analysis All data were the means of three replicates±SD. Statistical analysis was conducted by analysis of variance (ANOVA) and Duncan’s multiple range test for pair-wise comparison using SPSS 23.0 statistical software (IBM SPSS, Inc., Chicago, IL, USA). Differences at P ≤0.05 were considered signi cant. 3. Results 3.1. Effect of pre-harvest OA treatment on SSC, and TA in harvested kiwifruit The SSC in the control and OA pre-treated fruit increased gradually during storage, and reached to the maximum values on 13th d in both of fruit, but SSC in OA pre-treated fruit was significantly lower than that in the control in the first 7 d during storage (Fig. 1-A). The TA in the control and OA pre-treated fruit decreased during storage, but significantly lower TA showed in treated fruit from 1 to 7 d with respect to the control ( P ≤0.05) (Fig. 1-B). 3.2. Effect of pre-harvest OA treatment on AsA, DHA, T-AsA, and AsA/DHA ratio in harvested kiwifruit AsAcontent in the control increased at the first 4 d, and then decreased slightly until 13 d, while in OA pre-treated fruit it increased gradually at the first 7 d, and then decreased gradually for the remainder of the storage time. AsA in the control or treated fruit varied in the range of 28.80–32.49 or 34.29–45.86 mg 100 g –1 FW during storage, and pre- harvest spraying of OA resulted in a significantly higher AsA content at harvest and during storage compared to the control ( P ≤0.05) (Fig. 2-A). DHA content in the control and OA pre-treated kiwifruit increased gradually at the first 7 d and then remained stable to 13 d of storage, and no significant difference was observed between the control and OA pre-treatment (Fig. 2-B). * * * 0 4 8 12 16 1 4 7 10 13 SSC (%) Storage time (d) Storage time (d) A * * * 0.0 0.5 1.0 1.5 1 4 7 10 13 B CK 5 mmol L –1 oxalic acid TA (%) Fig. 1 Effect of pre-harvest oxalic acid (OA) treatment on soluble solids content (SSC; A) and titratable acid (TA; B) in kiwifruit during storage at room temperature. Data were the means of three replicates±SD. The asterisk indicates a significant difference ( P ≤0.05) between the control and pre-harvest OA treatment kiwifruit, and this specification applies to subsequent figures.