有机苹果贮藏

Storage of Organic Apples

Written by Marcella Galeni, Washington State University–Irrigated Agriculture Research and Extension Center and Carolina Torres, Washington State University–Tree Fruit Research and Extension Center, Wenatchee.

由华盛顿州立大学灌溉农业研究与推广中心的Marcela Galeni和华盛顿州立大学果树研究与扩展中心的Carolina Torres撰写，Wenatchee

Organic apple production in Washington represented 13% of the total harvest of apples in 2022 (Fruit Growers News, 2022). One of the biggest challenges for success and profitability is being able to store the fruit for more than eight months. In the absence diphenylamine (DPA) and 1-methylcyclopropene (1-MCP) to prevent superficial scald and slow down ripening, the use of controlled atmosphere (dynamic, low oxygen, and ultra-low oxygen) is the only chemical-free alternative to achieve it. Below we present a brief description of storage systems, including the use of low-pressure storage, which could become commercial in the future, as well as some results from a project conducted in ‘Honeycrisp’ and ‘Fuji’ apples, both of which are second and third in volume in Washington (Granatstein and Kirby, 2021).

华盛顿的有机苹果产量占2022年苹果总产量的13%（Fruit Growers News, 2022）。成功和盈利的最大挑战之一是能够将水果贮藏八个月以上。在没有二苯胺（DPA）和1-甲基环丙烯（1-MCP）来防止浅表烫伤和减缓成熟的情况下，使用气调（动态、低氧和超低氧）是实现这一目标的唯一无化学物质的替代方案。下面我们简要介绍了贮藏系统，包括低压存储的使用，它可能在未来商业化，以及在“Honeycrisp”和“Fuji”苹果中进行的一个项目的一些结果，这两种苹果在华盛顿的产量分别为第二和第三（Granatstein和Kirby，2021）。

Controlled Atmosphere Storage

Controlled atmosphere (CA) storage is a storage system widely used for storage of apples. In apples, 1%-3% O2 and 0.5%-2.5% carbon dioxide levels are commonly used, allowing long-term preservation through the decrease of ethylene production, slowing down ripening and senescence processes (Thompson et al., 2010). This system can also induce the development of physiological disorders associated with carbon dioxide toxicity (Figure 1) and internal browning (Prange and DeLong, 2006).

控制气调（CA）贮藏是一种广泛用于苹果贮藏的贮藏系统。在苹果中，通常使用1%-3%的O2和0.5%-2.5%的二氧化碳水平，通过减少乙烯产量来实现长期保存，减缓成熟和衰老过程（Thompson等人，2010）。该系统还可以诱导与二氧化碳毒性（图1）和内部褐变相关的生理障碍的发展（Prange和DeLong，2006）。

The recommended levels of oxygen and carbon dioxide in CA storage of apples can fluctuate according to where the fruit was cultivated showing differences among growing areas. In Washington State, ‘Honeycrisp’ is generally stored at 2%-4% oxygen and 0.8%-1% carbon dioxide at 37°F and ‘Fuji’ at 1%-2% oxygen and less than 1.0% carbon dioxide at 33°F commercially.

苹果CA贮藏中建议的氧气和二氧化碳水平可能会根据果实的种植地点而波动，这表明不同的生长区域存在差异。在华盛顿州，“Honeycrisp”在商业上通常储存在37°F下2%-4%的氧气和0.8%-1%的二氧化碳中，而“Fuji”在33°F下储存在1%-2%的氧气中，二氧化碳含量低于1.0%。

DYNAMIC CONTROLLED ATMOSPHERE STORAGE

Dynamic controlled atmosphere storage refers to the CA system where the oxygen level in managed dynamically throughout the storage season, according to the low oxygen level (LOL), which is the level of oxygen in storage before fermentation occurs. LOL can be determined by different methods directly or indirectly measuring the anaerobic compensation point (ACP) (Mditshwa et al., 2018). The anaerobic compensation point (ACP) is the level of oxygen where the metabolism of the fruit reaches a level that leads to fermentation. The commercial systems available to do DCA are chlorophyll fluorescence, respiratory quotient and ethanol concentration (Mditshwa et al., 2018). In our study, initial low oxygen stress (10 days prior CA conditions) and respiratory quotient storage systems decreased the incidence of soft scald after nine months of storage in comparison to standard CA storage, but the results varied amount seasons (Figure 2).

动态控制气调贮藏是指在整个储存季节，根据低氧水平（LOL）动态管理氧气水平的CA系统，低氧水平是发酵发生前储存中的氧气水平。LOL可以通过不同的方法直接或间接测量厌氧补偿点（ACP）来确定（Mditshwa等人，2018）。厌氧补偿点（ACP）是水果新陈代谢达到发酵水平的氧气水平。可用于进行DCA的商业系统是叶绿素荧光、呼吸商和乙醇浓度（Mditshwa等人，2018）。在我们的研究中，与标准CA储存相比，初始低氧应激（CA条件前10天）和呼吸商储存系统在储存9个月后降低了软烫伤的发生率，但结果随季节变化而变化（图2）。

Chlorophyll Fluorescence

The HarvestWatch® using a FIRM sensor measures the chlorophyll fluorescence (CF) on the fruit surface non-destructively during cold storage. This parameter correlates to low oxygen and high carbon dioxide stress that fruit is experiencing during this time (Prange et al., 2003) (Figure 3). The chlorophyll fluorescence (Fα) will increase when fermentation occurs indicating the LOL was detected.  The increase in chlorophyll fluorescence allows the operators to monitor the fruit and increase the oxygen level above the LOL to prevent fermentation (Zanella et al., 2005).

HarvestWatch®使用FIRM传感器在冷藏期间无损地测量水果表面的叶绿素荧光（CF）。这一参数与水果在此期间经历的低氧和高二氧化碳胁迫有关（Prange等人，2003年）（图3）。当发酵发生时，叶绿素荧光（Fα）将增加，表明检测到LOL。叶绿素荧光的增加使操作员能够监测水果，并将氧气水平提高到LOL以上，以防止发酵（Zanella等人，2005）。

Respiratory Quotient

The respiratory quotient (RQ) systems monitor the ACP through the ratio of carbon dioxide produced and oxygen consumed by the stored produce (Mditshwa et al., 2018). A RQ value above 1.0 indicates a transition from aerobic to anaerobic or fermentative metabolism (Weber et al., 2020). SafePod (Storage Control Systems Inc., Sparta, MI, USA) is a RQ system commercially available (Figure 4).

呼吸商（RQ）系统通过储存农产品产生的二氧化碳和消耗的氧气的比例来监测ACP（Mditshwa等人，2018）。RQ值高于1.0表示从有氧代谢到厌氧或发酵代谢的转变（Weber等人，2020）。SafePod（Storage Control Systems Inc., Sparta, MI, USA）是一种商用RQ系统（图4）。

Ethanol Concentration

Another method to monitor anerobic respiration when low oxygen levels are used in storage, is through the measurement of ethanol concentration. Initial low oxygen stress (ILOS) prior to the establishment of CA storage has shown benefits by reducing superficial scald and firmness loss in apples (Wang and Dilley, 2001; Zanella, 2003). This system consists of lowering oxygen levels immediately after harvest for 1-2 weeks to induce ethanol accumulation in the fruit Wright et al., 2015). Performing ILOS before CA storage at 1kPa O2 can be an alternative for DPA use against superficial scald for ‘Granny Smith’ apples (Zanella, 2003).

当储存中使用低氧水平时，监测无氧呼吸的另一种方法是通过测量乙醇浓度。在建立CA贮藏之前的初始低氧胁迫（ILOS）已显示出减少苹果表面烫伤和硬度损失的益处（Wang和Dilley，2001；Zanella，2003年）。该系统包括在收获后立即降低氧气水平1-2周，以诱导乙醇在果实中积累（Wright等人，2015）。在1kPa O2的CA储存前进行ILOS可以作为DPA的替代方案，用于防止“Granny Smith”苹果的浅表烫伤（Zanella，2003）。

Hypobaric or Low-pressure Storage

Hypobaric or low-pressure storage is a system that stores horticultural commodities by ventilating air at less than atmospheric pressure, extending the useful life of perishable commodities past that attained by CA storage at the same oxygen levels (Wang and Dilley, 2000). Hypobaric storage works by not only decreasing ethylene, but also removes other gaseous such as carbon dioxide within the stored produce, thereby delaying the ripening process (Burg, 2004). Hypobaric storage involves the use of a vacuum pump, which constantly removes air from the store to retain the desired oxygen level since the stored commodity is continuously respiring (Thompson, 2016). However, the removal of air from the storage reduces the respiration rate and leads to rapid water loss by the commodity; therefore, the commodity needs to be maintained at a humidity closest to saturation (100% RH) to limit the loss of water in storage. In our study, respiration rate is lower in low pressure storage than in CA storage for both seasons (Figure 5).  The low-pressure storage chambers were provided by Ripelocker, LLC. The system dynamically manage pressure, oxygen and carbon dioxide inside the chambers. The system is commercially available for blueberries, cut flowers, and hops, but further research needs to be performed in Apples. Our objective in the study was to modulate chilling injury disorders such as soft scald and soggy breakdown in ‘Honeycrisp’ apples (Figure 6). For this reason, we chose to store ‘Honeycrisp’ apples under 33°F instead of 37°F, which is the recommended temperature for the cultivar. Prolong shelf-life after storage as well as delay softening, decrease decay and control of physiological disorders are some of the advantages of storing apples stored under hypobaric conditions (Thompson, 2016). While hypobaric storage has many advantages over CA storage, the system is not widely used in the United States because of cost associated with the technology (Paskus et al., 2021). No commercial hypobaric or low-pressure storage is currently available for growers and packers.

低压或低压储存是一种通过在低于大气压的条件下通风来储存园艺商品的系统，将易腐商品的使用寿命延长到相同氧气水平下CA储存的使用寿命之后（Wang和Dilley，2000）。低压储存不仅可以减少乙烯，还可以去除储存农产品中的其他气体，如二氧化碳，从而延缓成熟过程（Burg，2004）。低压储存涉及使用真空泵，该真空泵不断地从储存中排出空气，以保持所需的氧气水平，因为储存的商品不断地呼吸（Thompson，2016）。然而，从储藏室中去除空气会降低呼吸速率，并导致商品快速失水；因此，商品需要保持在最接近饱和的湿度（100%RH），以限制储存中的水分损失。在我们的研究中，在两个季节，低压储存的呼吸速率都低于CA储存的呼吸率（图5）。低压储存室由Ripelocer有限责任公司提供。该系统动态管理储存室内的压力、氧气和二氧化碳。该系统可用于蓝莓、切花和啤酒花，但还需要在苹果中进行进一步的研究。我们在这项研究中的目的是调节“Honeycrisp”苹果的冷害障碍，如软烫伤和湿分解（图6）。因此，我们选择将“Honeycrisp”苹果储存在33°F下，而不是37°F，这是该品种的推荐温度。在低压条件下储存苹果，可以延长储存后的保质期，并延迟软化、减少腐烂和控制生理障碍（Thompson，2016）。虽然低压存储比CA存储有许多优势，但由于与该技术相关的成本，该系统在美国没有得到广泛使用（Paskus等人，2021）。目前没有可供种植者和包装商使用的商业低压或低压储存。

Figure 5. Respiration rate of ‘Honeycrisp’ apples after nine months of CA storage plus four weeks in Air storage plus seven days at room temperature. Abbreviations: CA (controlled atmosphere storage), LP (low-pressure storage). The data into graph is displayed as average and standard error.

References

Burg, S.P., 2004. Origins of the LP concept, In: Postharvest Physiology and Hypobaric Storage of Fresh Produce. CABI Wallingford, Oxon, UK, Cambridge, MA, USA, pp. 9–17. https://doi.org/10.1079/9780851998015.0000

Granatstein, D., Kirby, E., 2021. Recent Trends in Certified Organic Tree Fruit. Wenatchee, WA. https://s3-us-west-2.amazonaws.com/tfrec.cahnrs.wsu.edu/wp-content/uploads/sites/9/2021/03/WA_OrgTreeFruit_ann_rev_2020.pdf

Fruit Growers News, 2022. Washington’s fresh apple crop is smaller, but growers optimistic. https://fruitgrowersnews.com/news/washingtons-fresh-apple-crop-is-smaller-but-growers-optimistic/

Mditshwa, A., Fawole, O.A., Opara, U.L., 2018. Recent developments on dynamic controlled atmosphere storage of apples—A review. Food Packaging and Shelf Life 16, 59–68. https://doi.org/10.1016/j.fpsl.2018.01.011

Paskus, B., Abeli, P., Beaudry, R., 2021., Hypobaric Storage of Representative Root, Leaf, Fruit, and Flower Tissues: Comparisons to Storage at Atmospheric Pressure and Normoxia. HortScience 56, 780–786. https://doi.org/10.21273/HORTSCI15786-21

Prange, R.K., DeLong, J.M., 2006. Controlled-atmosphere related disorders of fruits and vegetables. Stewart Postharvest Review. 5(7), 1-10.

Prange, R.K., DeLong, J.M., Harrison, P.A., Leyte, J.C., McLean, S.D., 2003. Oxygen concentration affects chlorophyll fluorescence in chlorophyll-containing fruit and vegetables. J. Am. Soc. Hortic. Sci. 128, 603–607. https://doi.org/10.21273/jashs.128.4.0603

Thompson, A.K., 2010. CA Technology, In: Controlled Atmosphere Storage of Fruits and Vegetables. CABI, Wallingford, UK. pp. 26-44. https://doi.org/10.1079/9781845936464.0000

Thompson, A.K., 2016. Hypobaric Storage, in: Fruit and Vegetable Storage: Hypobaric, Hyperbaric and Controlled Atmosphere. Springer, Huddersfield, UK, pp. 37–92. https://doi.org/10.1007/978-3-319-23591-2

Wang, Z., Dilley, D.R., 2000. Initial low oxygen stress controls superficial scald of apples. Postharvest Biol. Technol. 18, 201–213. https://doi.org/10.1016/S0925-5214(00)00067-3

Wang, Z., Dilley, D.R., 2001. Initial Low Oxygen Stress (ILOS) Controls Scald of Apples Without Using Postharvest Chemical Treatments. Acta Horitculture 21, 261–266.

Weber, A., Neuwald, D.A., Kittemann, D., Thewes, F.R., Both, V., Brackmann, A., 2020. Influence of respiratory quotient dynamic controlled atmosphere (DCA – RQ) and ethanol application on softening of Braeburn apples. Food Chem. 303, 125346. https://doi.org/10.1016/j.foodchem.2019.125346

Wright, A.H., Delong, J.M., Arul, J., Prange, R.K., 2015. The trend toward lower oxygen levels during apple (Malus × domestica Borkh) storage – A review. J. Hortic. Sci. Biotechnol. 90, 1–13. https://doi.org/10.1080/14620316.2015.11513146

Zanella, A., 2003. Control of apple superficial scald and ripening—a comparison between 1-methylcyclopropene and diphenylamine postharvest treatments, initial low oxygen stress and ultra low oxygen storage. Postharvest Biology and Technology, 27(1), 69–78. https://doi.org/10.1016/S0925-5214(02)00187-4

Zanella, A., Cazzanelli, P., Panarese, A., Coser, M., Cecchinel, M., Rossi, O., 2005. Fruit fluorescence response to low oxygen stress: Modern storage technologies compared to 1-MCP treatment of apple. Acta Hortic. 682, 1535–1542. https://doi.org/10.17660/ActaHortic.2005.682.204

Contact

Marcella Galeni

Scientific Assistant, Stone Fruit Breeding & Genetics
WSU Irrigated Agriculture Research and Extension Center

Prosser, WA

phone: 509-786-9306
email: m.galenisoaresrafae@wsu.edu

Carolina Torres
Endowed Chair Postharvest Systems, Horticulture
WSU Tree Fruit Research & Extension Center
Wenatchee, WA
phone: 509-293-8808
email: ctorres@wsu.edu

Funding and acknowledgements

Washington Tree Fruit Research Commission

Project Title: Postharvest system optimization for organic apple storage (2019-2021)

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