JIA-2019-11

Journal of Integrative Agriculture 2019, 18(11): 2514–2520 RESEARCH ARTICLE Available online at www.sciencedirect.com ScienceDirect Pre-harvest spraying of oxalic acid improves postharvest quality associated with increase in ascorbic acid and regulation of ethanol fermentation in kiwifruit cv . Bruno during storage Maratab Ali, LIU Meng-meng, WANG Zhen-e, LI Sheng-e, JIANG Tian-jia, ZHENG Xiao-lin College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, P.R.China Abstract The kiwifruit trees ( Actinidia deliciosa cv . Bruno) were sprayed with 5 mmol L –1 oxalic acid (OA) or water (as control) at 130, 137 or 144 d after full-blossom, and then the fruit were harvested at commercial maturity and stored at room temperature (20±1)°C for 13 d. The effect of pre-harvest spraying of OA on postharvest quality of kiwifruit was evaluated during storage. The OAspraying slowed the increase in soluble solids content (SSC) and decrease in titratable acid (TA), as well as increased contents of ascorbic acid (AsA) and total-AsA accompanied with higher AsA/DHA ratio in kiwifruit during storage. Moreover, the OA spraying significantly reduced the contents of acetaldehyde and ethanol in kiwifruit, along with significant decrease in activities of enzymes involved in ethanol fermentation metabolism during the later period of storage, which was beneficial to control off-flavor associated with over accumulation of ethanol during postharvest. It was suggested that pre-harvest spraying of OA might maintain the postharvest quality of kiwifruit in relation to delay in fruit ripening, AsA maintenance and regulation of ethanol fermentation. Keywords: ethanol metabolism, kiwifruit, oxalic acid, pre-harvest spraying, postharvest quality under various atmospheric factors, i.e., high CO 2 /low O 2 , low temperature and long-term storage duration; such changes may accelerate quality deterioration during postharvest, among which over-accumulation of ethanol fermentation metabolites including acetaldehyde and ethanol results in off-flavor formation (Lee and Kader 2000; Pesis 2005). In particular, a cultivar Bruno of kiwifruit ( Actinidia deliciosa ) is once regarded as one of the most significant cultivars in New Zealand, and has also become a main cultivar introduced in Zhejiang Province, China. However, the fruit cv . Bruno is prone to accumulate ethanol sharply after respiratory climacteric during storage at ambient conditions without stress, which causes quality deterioration of the fruit associated with off-flavor of alcohol (Li et al . 2016). Ethanol fermentation metabolism is a two-step process, including the decarboxylation of pyruvate into acetaldehyde and conversion of acetaldehyde to ethanol by the pyruvate Received 18 November, 2018 Accepted 23 August, 2019 Correspondence ZHENG Xiao-lin, Tel: +86-571-28008959, Fax: +86-571-28008900, E-mail: zheng9393@163.com © 2019 CAAS. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/) . doi: 10.1016/S2095-3119(19)62791-7 1. Introduction Kiwifruit, as one of subtropical fruit, is most cherished by consumers due to rich in L-ascorbic acid (AsA; i.e., vitamin C) and other health nutrients (Razavi and BahramParvar 2007; Garcia et al . 2012). However, kiwifruit, as one typically climacteric fruit, is susceptible to physiological disorders