Prestorage Temperature and Ultra-Low Oxygen Treatments Affect
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| POSTHARVEST BIOLOGY AND TECHNOLOGY HORTSCIENCE 53(10):1475–1481. 2018. https://doi.org/10.21273/HORTSCI13323-18 antioxidants, and ventilation, all of which are extensively reviewed in Lurie and Watkins (2012). Prestorage Temperature and Ultra-low Organic production has increased steadily in the last two decades in the United States Oxygen Treatments Affect Incidence of and has particularly expanded in the apple market. Apples are among the top three most Physiological Disorders in Organic preferred products purchased by consumers of organic foods, with ‘Granny Smith’ being the fifth most produced organic apple (U.S. ‘Granny Smith’ Apples Department of Agriculture Economic Re- Juan Pablo Zoffoli1, Valentina Sanguedolce, Paulina Naranjo, search Service, 2011). Organic production and Carolina Contreras has also recently become important in Chile, í í where, during 2016, the exported volume Facultad de Agronom a e Ingenier a Forestal, Pontificia Universidad rose sharply by 40%. Organic apples in Chile Catolica de Chile, Santiago, Chile account for 1200 planted hectares, with ‘Granny Smith’ the third most-produced Additional index words. superficial scald, bitter pit, lenticel blotch pit, 1-MCP organic cultivar (ODEPA, 2017). In the Abstract. The physiological disorders superficial scald, bitter pit, and lenticel blotch pit southern hemisphere, organic apple harvest severely compromise the commercial value of ‘Granny Smith’ apples. A number of chemical starts in March and export of fruit to the treatments are available to alleviate these disorders but they are unacceptable in the northern hemisphere extends to June. Super- expanding organic market. The objective of this research was to study the effectiveness of ficial scald limits the extent of this export prestorage treatments—delayed cooling and elevated temperature under ultra-low market window, as the opportunity for com- oxygen (ULO) atmospheres—as organic-friendly strategies to control these disorders. mercialization of organic ‘Granny Smith’ is ‘Granny Smith’ apples were exposed to four different treatments: 1) conditioning limited to 90 d of storage before the appear- temperature treatments (CTemp): 10 days at 3 8C or 30 days at 3 8C or 10 days at 20 8C, in ance of the symptoms of the disorder. air; 2) the same conditioning temperature treatments combined with an ultra-low oxygen The organic market is highly restrictive in (ULO) conditioning treatment of 0.2–0.5 kPa O2 and <0.5 kPa CO2; 3) 1-methylcyclo- terms of the use of chemicals, which makes propene (1-MCP) treatment as a commercial control; and 4) untreated control fruit. the storage of organic apples a particular After the prestorage treatment, fruit were stored for 90 or 150 days at 0 8C, and then held challenge. Products frequently used in con- poststorage for 8 days at 20 8C before quality analysis. A combination treatment of ventional apples, such as DPA and 1-MCP, temperature conditioning and ULO for 30 days at 3 8C achieved the best control of are not allowed for organic apples. Addition- superficial scald, bitter pit, and lenticel blotch pit. The use of ULO with CTemp for 10 ally, 1-MCP may increase bitter pit and days at 20 8C offered the same control but induced high concentrations of ethanol and lenticel blotch pit (Calvo and Cardan, 2010; acetaldehyde that affected the organoleptic acceptability of the fruit and reduced its Gago et al., 2015). Likewise, the traditional commercial value. The use of 1-MCP offered 100% control of superficial scald but bitter concentrations of O2 and CO2 of CA (1.5 kPa pit and lenticel blotch pit disorder incidences were similar or higher than in the control O2; 1 kPa CO2) are not sufficient for the fruit. All ULO conditioning treatments resulted in high ethanol and acetaldehyde control of superficial scald (Lau, 1990). This concentrations during the first 90 days of storage, but fruit exposed to ULO conditioning situation means researchers must look for treatment for 30 days at 3 8C showed similar organoleptic acceptability to control fruit alternative non-chemical interventions. after 150 days. Therefore, ULO conditioning is a potentially useful treatment for the Organic-friendly strategies for the control organic apple industry. of superficial scald include ULO and ILO, DCA and, recently, the combination of low oxygen and high temperature for short pe- ‘Granny Smith’ is the most common tolerance of 0.1 ppm (EU Pesticides Data- riods (Pesis et al., 2010). However, few studies green apple cultivar in the world. However, base, 2012), apple commerce in global export have investigated the interaction between low it is highly susceptible to physiological dis- markets has been affected, particularly in the oxygen and different temperatures. In the orders such as superficial scald and bitter pit EU (Rickard et al., 2016). Some alternative search for non-chemical alternatives to extend (Mitcham et al., 1996). These disorders re- strategies that have been explored to replace the storage life of organic apples by control- duce the effective storage time and make DPA include 1) the use of 1-methylcyclopro- ling superficial scald, bitter pit, and lenticel ‘Granny Smith’ production highly dependent pene (1-MCP), which substantially reduces blotch pit, we investigated interactions be- on the use of chemical treatments. Bitter pit is or eliminates superficial scald during storage tween different conditioning temperature and a physiological disorder associated with (Rupasinghe et al., 2000; Watkins, 2006); 2) low oxygen treatments. low calcium concentration in the fruit. Cur- ultra low oxygen (ULO; 0.7 kPa O2), a con- rently, the only effective method for con- trolled atmosphere (CA) storage technology Materials and Methods trolling bitter pit consists in several preharvest which reduces superficial scald (Wang and and postharvest calcium spray applications Dilley, 2000) and its variants initial low Plant material and treatments (Ferguson and Watkins, 1989). In many parts oxygen (ILO) (Wang and Dilley, 1999; On 29 Mar. 2016, ‘Granny Smith’ apples of the world, superficial scald has been con- Zanella, 2003) and dynamic atmosphere stor- were selected for uniformity and freedom trolled or alleviated commercially with di- age (DCA) (Zanella et al., 2005); and 3) from blemishes from a group of five 350 kg phenylamine (DPA) applications (Little et al., delayed cooling treatments (also known as plastic bins in a packhouse. This was done as 2000). prestorage conditioning treatments), such as soon as the fruit arrived from harvest from With the recent ban on the use of DPA by warming before or during cold storage a commercial organic orchard in Quinta the European Union (EU), with a maximum (Alwan and Watkins, 1999), or stepwise Tilcoco in the Central Valley, Chile cooling (Moggia et al., 2009). All of these (34°22#11.84$S, 70°50#59.20$W). technologies either greatly reduce a-farne- A total of 5680 fruit (600 kg) were sene synthesis and accumulation (1-MCP and transported 300 km to the Postharvest Labo- Received for publication 21 June 2018. Accepted a for publication 8 Aug. 2018. ULO) or prevent -farnesene oxidation ratory of the Catholic University of Chile. We gratefully acknowledge the partial financial (DPA and ULO). Many other technologies Fruit was stored overnight at 20 °C before support of Copefrut Export. have been reported, such as ethanol vapor treatments were applied. Initial fruit maturity 1Corresponding author. E-mail: [email protected]. treatment, intermittent warming, coatings, was assessed on 80 randomly-selected fruit HORTSCIENCE VOL. 53(10) OCTOBER 2018 1475 and the remainder were grouped randomly boxes with perforated plastic liner bags, 175 Fruit chemical analyses into four sets of 2100, 2100, 700, and 700. fruit in each, and left as controls and stored a-farnesene and conjugated trienol These fruit sets were then treated differently. directly at 0 °C for the same period of time. concentrations in the apple peel tissue. The One set of 2100 fruit was ‘‘prestorage’’ treated in an air atmosphere at one of three conditioning temperatures (CTemp) (700 fruit at each temperature). The three CTemp treatments were 1) 10 d at 3 °C, 2) 30 d at 3 °C, or 3) 10 d at 20 °C. The second set of 2100 fruit was conditioned at the same three temperatures (700 fruit at each) while under an ULO conditioning treatment with a partial pressure of oxygen of 0.2–0.5 kPa and a CO2 partial pressure of <0.5 kPa. One set of 700 fruit was treated with 1-MCP and one set of 700 fruit served as the untreated control. ULO conditioning treatments were placed in open 200 L plastic containers for 24 h to reach the desired temperature (3 °Cor20°C), then containers were sealed and the desired partial oxygen pressure was obtained by replacing the air (initially 21 kPa) with 100 kPa N2, dispensed from a nitrogen cylinder (Indura S.A., Santiago, Chile). Each ULO conditioning treatment was applied using four replications of 175 fruit, each in separate container. The oxygen partial pressure was adjusted manually by flushing with nitrogen (to lower it) or with air (to raise it). On one occasion, two independent con- tainers leaked, but the partial pressures of O2 and CO2 were rapidly restored. Meanwhile, the CO2 partial pressure was maintained low (<1 kPa) using hydrated lime. Each container was provided with a sampling port with a septum attached. During the ULO condition treatments, a sample of 200 mL was obtained with a syringe, and the O2 and CO2 in the free space of the containers were determined every two days. The CO2 and O2 were checked with a portable MAP 4000 analyzer (Hitech In- struments Ltd., Luton, UK) with zirconia and katharometer sensors, respectively. For the 1-MCP treatment, four boxes with 175 fruit in each were exposed to 625 nL·L–1 1-MCP (1 g·m–3, powder 0.14%, SmartFresh; AgroFresh, Collegeville, PA) for 24 h at 20 °C in a closed chamber.