Postharvest treatments to improve quality and postharvest life of table grapes

The main objective of this study was to assess the effectiveness of putrescine (Put) (1 and 2 mM for 10 min) and ultrasound treatments (32 kHz for 10 min) alone or in combination on changing biochemical compounds and extending postharvest life of grape. After treatments, clusters were packed in boxes with modified atmosphere packaging and stored at 1-2 ?C with 90-95% relative humidity for 60 days. The weight loss, total soluble solids, titratable acidity, total anthocyanins, total phenolic content, antioxidant capacity, stem browning, decay rate and visual appearance at 0, 20, 40 and 60 days after harvest were recorded. Statistically significant differences were observed between different treatments in all measured parameters except for weight loss and total soluble solids. The data showed that individual Put or ultrasound treatment had a positive response in maintaining grape quality during storage, but conjugation of Put with ultrasound treatments showed better effects. Combination treatments maintained higher levels of anthocyanins, total phenolic content, antioxidant capacity and reduced the loss of sensory acceptability and decay incidence compared to control. At the end of the storage, control grapes markedly lost their quality, reaching below the critical marketable level while all the treatments preserved better the visual quality. These results demonstrated that the combined treatments of Put and ultrasound could be a promising approach to maintain postharvest storage quality of grapes. Grapes are highly perishable commodities and thus length of storage is limited. Major factors limiting grape storage and shelf life and causing important economic losses to the industry are cluster dehydration (berry water loss and rachis browning), skin colour changes, accelerated softening and microbial spoilage, especially gray mould decay caused by the pathogen Botrytis cinerea (Soylemezoglu, 2001). Appropriate environmental conditions during storage or transportation and the use of sulphur dioxide (SO2) technologies have successfully alleviated these problems. Despite its efficacy, the SO2 technology may compromise fruit taste and can cause damage to the grape which is manifested as cracks and bleaching. In addition, hypersensitivity reaction was reported in humans justifying the search for alternative technologies (Lichter et al., 2006). Several preservation technologies have been suggested to enhance the postharvest life of fresh horticultural produce. Recently, biologically active natural products have started to become an effective alternative to synthetic fungicides in maintaining fruit quality during storage (Tripathi and Dubey, 2004). Polyamines (PA) are small aliphatic amines, having low molecular weight that are ubiquitous in living organisms and have been implicated in a wide range of biological processes, including plant growth, development and response to stress (Smith, 1985). In plants, they have been implicated in a wide range of biological processes, including growth, development and abiotic stress responses. The most common polyamines are Put, spermidine (Spd) and spermine (Spm) found in every plant cell (Asrey and Barman, 2015). Reddy et al. (2008) reported that Put was the major polyamine followed by spermidine and spermine in grapes. Postharvest application of polyamines has been demonstrated to influence the shelf life and quality of various fruits of both climacteric and nonclimacteric nature. The polyamines concentrations commonly used vary between 0.01 and 2 mM (Champa, 2015). Postharvest application of Put, by immersion or vacuum infiltration, has been reported to delay fruit ripening and extend shelf life in some climacteric or nonclimacteric fruits such as lemon (Valero et al., 1998), apricot (Martinez-Romero et al., 2001), mango (Malik and Singh, 2005), strawberry (Khosroshahi et al., 2007), sweet cherry (Bal, 2012), plum (Serrano et al., 2003; Davarynejad et al., 2013) and peach (Bal, 2013). Champa et al. (2014) reported that prestorage dip treatment of 0.5 mM Put or 0.5 mM Spd or 1.0 mM Spm for 5 min maintained the quality and extended the shelf life of grape cv. Flame Seedless for up to 60 days in cold storage. Further, postharvest Put-treated berries (1 and 2 mM) exhibited higher total phenolic content, catechin, total quercetin and antioxidant activity (Shiri et al., 2012). Ultrasound (sonication) treatment, which is an emerging technology that is considered to be inexpensive, simple, reliable and environmentally friendly, has been studied for use in several applications including fruit processing (Lagnika et al., 2017). Frequency of 20 kHz to 100 MHz, which is beyond the audible range of human hearing Ultrasound effects on liquid systems are mainly related to the cavitation phenomenon (Kate et al., 2016). Ultrasound is also one of the newest nonthermal methods to extend shelf life of fresh fruits during storage (Bal, 2013). Due to the elimination of microorganisms and enzymes without destroying nutrients of foods, ultrasound can be used as an alternative method (Ercan and Soysal, 2013). Although many studies have been done by applying ultrasound during food processing and preservation, there are few published reports on the effect of ultrasound treatments on postharvest horticultural physiology. In the studies, postharvest ultrasound treatments have been shown to extend shelf life and maintain quality in strawberries (Cao et al., 2010), litchis (Chen et al., 2012), plums (Chen and Zhu, 2011; Bal, 2016) and peach (Yang et al., 2011; Bal, 2013). But, effectiveness of postharvest ultrasound application on fruit quality has not been studied in table grapes. The present study was conducted to investigate the potential utilization of Put alone or in combination with ultrasound as a postharvest tool to maintain quality and extend the postharvest life of grapes cv. Michelle Palieri in cold storage (1-2 ?C and 90-95% RH) conditions Access to document 'Postharvest putrescine and ultrasound treatments to improve quality and postharvest life of table grapes (Vitis vinifera L.) cv. Michele Palieri'?(1) BAL, Erdinc; KOK,Demir / (2) TORCUK, Ali Izzet (1) Department of Horticulture, Faculty of Agriculture, University of Namik Kemal, Tekirdag, Turkey, correspondence: ebal@nku.edu.tr (2) Tekirdag Viticulture Research Institute, Tekirdag, Turkey