Ethylene is a gas often referred to as the "fruit-ripening phytohormone". Ethylene production in fruits is a natural mechanism that occurs during the ripening process or may be created when a plant is harmed in some manner.
Image Credit: leonori/Shutterstock.com
How Different Fruits Respond to Ethylene
During its existence, every fruit produces a particular amount of ethylene. However, ethylene amounts in certain fruits spike as the fruit begins to mature. Fruits are categorized into two broad classes on the basis of their reaction to ethylene during ripening.
The first category is known as climacteric fruits, and their maturation is characterized by a burst of ethylene. These fruits may also increase their ripening speed in response to exogenous ethylene. Good examples are fleshy fruits such as tomatoes, avocados, apples, melon, peaches, kiwis, and bananas.
Non-climacteric fruits are those in which ethylene formation does not ramp up throughout maturation. However, if such fruits are subjected to an exogenous source of ethylene, such as a maturing climacteric fruit, they may still ripen. Grapes, strawberries, and citrus fruits are good examples.
Many variables influence ethylene's impact on fruit ripening. The fruits must be developed enough to react well to ethylene.
Ripening is instantly encouraged by ethylene in high-sensitivity fruits such as bananas and cantaloupes, but the less mature the fruit is, the higher the quantity of ethylene needed to trigger the ripening process.
In fruits with lower sensitivity, such as apples or tomatoes, ethylene administration shortens the time it takes for ripening to take place. Some species like avocados do not ripen when still connected to the tree and progressively develop their responsiveness to ethylene over time.
So, What Exactly is Ethylene?
Ethylene (C2H4) is a plant hormone that influences the growth, maturation, post-harvest condition, and storability of fruits.
Ethylene production spikes during the maturation of climacteric fruits, promoting the ripening process. As a result, ethylene discharges represent fruit maturity and induce significant changes throughout the ripening process, such as boosting fruit color shifts, enhancing fruit scent, softening, and influencing texture.
Furthermore, ethylene aids in converting starch to sugar, thereby boosting the sugar levels of fruits. The adverse impacts of ethylene on quality, on the other hand, are also centered around speeding up the normal mechanisms of fruit growth, ripening, and senescence.
Why is it Important to Monitor Ethylene Levels?
Regarded as an aging hormone, ethylene not only affects fruit maturation but can also cause plant species to die, which usually happens when the plant is injured in some way.
Other impacts of ethylene production include loss of photosynthetic pigments, abortion of plant leaves and stems, shortened stems, and stem twisting (epinasty).
Despite the fact that non-climacteric fruits do not generate autocatalytic ethylene, external ethylene has a significant impact on their preservability and freshness. As a result, it is critical to monitor and manage the ethylene emission rate throughout the fruit production line to enhance fruit quality, which has received a lot of focus across the globe.
Monitoring Ethylene Levels
Ethylene levels in the post-harvest fruit environment must first be correctly measured.
Data gathering techniques used in cold chain logistics for fruits have progressed from conventional barcode or recorder systems to advanced Internet of Things (IoT) tracking systems with wireless communication and sensory technologies, all of which possess artificial intelligence, miniaturization, and real-time analysis capabilities.
Wireless sensor network (WSN) systems, as a typical representational technology, maintain a prominent standing in precision agricultural surveillance and environmental monitoring due to their ease of implementation and adaptability.
More precisely, detecting ethylene gas in the fruit environment on a microscale is mostly based on gas chromatographic assays, electrochemical detection, and optic detection.
Electrochemical sensing, which has outstanding reproducibility, precision, and rapid response and recovery properties, is quickly becoming the standard method for ethylene tracking.
How to Regulate Ethylene Levels
Along with ethylene detection, efficient and precise ethylene management strategies for both internally and externally produced ethylene must not be overlooked. Endogenous ethylene is created within the fruit itself, discharged into the surroundings, and speeds up fruit maturation and aging, whereas exogenous ethylene is typically provided artificially.
To delay the ripening process and senescence, it is important to block internal ethylene production and limit the quantity of external ethylene in the fruit environment on a microscale. Conversely, introducing external ethylene and promoting internal biosynthesis might be used to artificially ripen the fruit.
Recent Advances in Ethylene Monitoring and Control
Wang et al. (2020) developed an electrochemical ethylene sensor system to dynamically monitor ethylene levels. In addition, the ethylene detecting properties and tracking effectiveness were investigated in the study.
The ethylene regulation technique, viable in various scenarios and settings, was evaluated and validated in a variety of fruits and situations, demonstrating its efficacy in post-harvest fruit quality control.
The purpose of this research was to provide an ethylene sensor equipped with dynamic monitoring and variable-strategy regulation for fruit cold chain storage and quality management.
The system might help stakeholders make decisions by collecting data on ethylene concentrations in the fruit microenvironment remotely, accurately, and in real-time. It could also help increase the quality of regulations.
Continue reading: How Can Edible Food Sensors Help Us?
References and Further Reading
Grant, A. (2021). What Is Ethylene Gas: Information On Ethylene Gas And Fruit Ripening. [online] General Fruit Care. Available at: https://www.gardeningknowhow.com/edible/fruits/fegen/ethylene-gas-information.htm
Moirangthem, K., & Tucker, G. (2018). How Do Fruits Ripen? [online] Frontiers for Young Minds. Available at: https://kids.frontiersin.org/articles/10.3389/frym.2018.00016
Wang, X., Li, X., Fu, D., Vidrih, R., & Zhang, X. (2020). Ethylene Sensor-Enabled Dynamic Monitoring and Multi-Strategies Control for Quality Management of Fruit Cold Chain Logistics. Sensors, 20(20). Available at: https://doi.org/10.3390/s20205830
Xing, Y., Zhu, H., Chang, G., Yu, K., & Yue, F. (2019). Metal Oxide Nanostructures-Based Gas Sensor for Ethylene Detection: A Review. IOP Conference Series: Materials Science and Engineering, 677(2). Available at: https://doi.org/10.1088/1757-899X/677/2/022082