The fruit ripening process

Fruit ripening is the final stage of fruit development where it becomes one of the most important determinants of fruit quality and consumer acceptability⁵. Ripeness brings out the best flavours and texture as the fruit becomes sweet, coloured, soft, and develops an appetizing aroma⁷. Fruit ripening is also associated with ethylene, a phytohormone that can lead to the initiation of the ripening and senescence process³. Fruit ripening can be divided into two groups: climacteric and non-climacteric fruits. In climacteric, the fruit continues to ripen after harvesting while in non-climacteric, the fruit does not continue to ripen once it’s been picked^5,10. However, if these fruits are exposed to an external ethylene source, such as a ripening climacteric fruit, they can still ripen¹³.

Source:  Apeel, 2020

Why control fruit ripening?

• Extends the storage and shelf life of fresh fruits, especially during shipping and handling.
• Prevent fruit deterioration and maintain visual appeal, as the fruit ripens or enters senescence, it becomes susceptible to fungal and fruit-pathogen resulting in spoilage.
• Dramatically reduce wastage in transit to maximize the yield from the crop.
• Reduce the inherent risk of damaged fruit adversely affecting an entire batch.
• Maximise returns by accessing the markets that most value your fruit.
• Enhance reputation as a supplier of high-quality produce.

Source: Figueroa, 2021; Its Fresh, 2022; Payasi & Sanwal, 2010

How do we control fruit ripening?

1. Controlling the level of ethylene

As fruits and vegetables mature, they produce increasing amounts of ethylene. This ethylene initiates ripening-associated activities such as increased respiration and softening of the fruits even when the fruit is packaged⁸. By controlling the level of ethylene, the ripening process is slowed down and fruits can be transported or stored for a longer period without becoming overripe or spoiled. Hence, delivering it to the customer in the best possible condition^3,10. Ethylene inhibitors are used to extend storage life in fruits by using synthetic compounds such as 1-methylcyclopropene (1-MCP)⁸.

Source:  Gamrasni et al., 2020

• Lowering the temperature

Storage temperature plays a pivotal role in fruit metabolism during long-term storage, causing changes in physical and chemical attributes and in the aroma composition of various fruits^8,11. The fruit industry utilizes a cold storage temperature of 0–4°C to slow down the ripening process and extend fruit life⁸. Low temperatures generally inhibit microbial growth and slow down respiration, thus maintaining fruit quality during storage¹. This is important because it allows the product to be shipped further distances and arrive in better condition⁶.

• Modified atmosphere packaging (MAP)

Another way to slow down ripening is by controlling or modifying the atmosphere around the fruit in the packages, primarily by increasing carbon dioxide (CO₂) and reducing oxygen (O₂) levels, thereby extending the shelf-life⁹. Consequently, exposure of fruits to high CO₂ affects respiratory metabolism. This is because fruit needs oxygen to ripen, so if there is less oxygen in the atmosphere, the fruit will ripen more slowly. Furthermore, the combination of N₂O with low O₂ in a controlled atmosphere also gives a synergic effect in delaying the ripening process due to its anti-ethylene activity¹⁰.

• Edible surface coating

The edible surface coating has also been used as a strategy to delay fruit ripening. Sucrose esters, hydroxypropyl methylcellulose (HPMC), nanoemulsions, and chitosan-based coating have been effective in prolonging the shelf life and quality of fruits¹⁰. This is due to the layer from the coating agent will reduce the respiration rate and improve the water barrier in fruits^2,12. According to a study, the shelf life of coated fruit was extended by 12 days when compared to untreated controls which ripened within seven days and lost marketability after day 6¹².

Source:  de Oliveira Filho et al., 2021²

Conclusion

Consumers tend to choose their fruits based on its ripeness at the supermarket. However, once the fruits are ripe, they tend to spoil quickly. Thus, by controlling the ripeness of fruit not only helps the grower to save on postharvest losses, but also brings benefits in terms of retained fruit freshness for a longer period and results in value addition to the fruit¹⁰.

References

¹Abilasha, R. (n.d.). Fruit Ripening: Meaning, Factors, and Controls | Plant Physiology increasing carbon dioxide levels and reducing oxygen levels.

²de Oliveira Filho, J. G., Miranda, M., Ferreira, M. D., & Plotto, A. (2021). Nanoemulsions as edible coatings: A potential strategy for fresh fruits and vegetables preservation. Foods, 10(10), 2438. https://doi.org/10.3390/foods10102438

³Figueroa, C. R., Jiang, C.-Z., Torres, C. A., Fortes, A. M., & Alkan, N. (2021). Editorial: Regulation of fruit ripening and senescence. Frontiers in Plant Science, 12. https://doi.org/10.3389/fpls.2021.711458

⁴Gamrasni, D., Feldmesser, E., Ben-Arie, R., Raz, A., Tabatznik Asiag, A., Glikman, M., Aharoni, A., & Goldway, M. (2020). Gene expression in 1-methylcyclopropene (1-MCP) treated tomatoes during pre-climacteric ripening suggests shared regulation of methionine biosynthesis, ethylene production and respiration. Agronomy, 10(11), 1669. https://doi.org/10.3390/agronomy10111669

⁵ISAAA. (2020, March). Pocket K no. 12: Delayed ripening technology. Delayed Ripening Technology.  Retrieved February 21, 2023, from https://www.isaaa.org/resources/publications/pocketk/12/default.asp

⁶It’s Fresh. (2022). Control the ripening of kiwis in transit, reducing defects and delivering great quality to the market. https://itsfresh.com/ethylene-control-applications/kiwi/

⁷Maduwanthi, S. D., & Marapana, R. A. (2019). Induced ripening agents and their effect on fruit quality of banana. International Journal of Food Science, 2019, 1–8. https://doi.org/10.1155/2019/2520179

⁸Olubero Asiche, W., Witere Mitalo, O., Kasahara, Y., Tosa, Y., Gituma Mworia, E., Ushijima, K., Nakano, R., & Kubo, Y. (2017). Effect of storage temperature on fruit ripening in three kiwifruit cultivars. The Horticulture Journal, 86(3), 403–410. https://doi.org/10.2503/hortj.okd-028

⁹Park, M. H., Sangwanangkul, P., & Choi, J. W. (2018). Reduced chilling injury and delayed fruit ripening in tomatoes with modified atmosphere and humidity packaging. Scientia Horticulturae, 231, 66–72. https://doi.org/10.1016/j.scienta.2017.12.021

¹⁰Payasi, A., & Sanwal, G. G. (2010). Ripening of climacteric fruits and their control. Journal of Food Biochemistry, 34(4), 679–710. https://doi.org/10.1111/j.1745-4514.2009.00307.x

¹¹Pholoma, S. B. (2020). Is ethylene the ripening hormone. Journal of Experimental Agriculture International, 42(5), 1–7. https://doi.org/10.9734/jeai/2020/v42i530510

¹²Thakur, R., Pristijono, P., Bowyer, M., Singh, S. P., Scarlett, C. J., Stathopoulos, C. E., & Vuong, Q. V. (2018). A starch edible surface coating delays banana fruit ripening. LWT. https://doi.org/10.1016/j.lwt.2018.10.055 

¹³Xamélie Fauché, Abdulsami Hanano, Demetrio Marcianò, Meirav Leibman-Markus. (n.d.). How do fruits ripen? Frontiers for Young Minds. Retrieved February 21, 2023, from https://kids.frontiersin.org/articles/10.3389/frym.2018.00016#:~:text=The%20second%20group%20is%20called,and%20citrus%20fruits%20%5B3%5D.