The Science Behind Fruit Ripening

Have you ever wondered how a hard, green fruit turns into a sweet, juicy delight? The secret is the complex science of fruit ripening. This process has intrigued scientists for years¹. A plant hormone called ethylene is at the heart of this amazing change². But, how does this gas start the ripening? And what about other factors that add to the taste and feel of the fruit?

Ethylene is a crucial plant hormone that starts the ripening process in many fruits.
Some fruits, like bananas and apples, can keep ripening after they’re picked. But others, like grapes and berries, do not.
After being picked, fruits make more ethylene. This shortens their life and makes them more open to getting sick.
By using certain technologies before and after picking fruits, we can control how much ethylene they make. This can change how they ripen.
Knowing about the science of fruit ripening can help make fruit taste better, feel better, and last longer.

What is Fruit Ripening and the Role of Ethylene?

Fruit ripening changes fruits, making them enjoyable to eat. This process increases the fruit’s respiration, making more ethylene, and softens the flesh. It also raises the sugar levels and enhances the aroma and flavor³.

Fruit Ripening Process

The rise of ethylene signals fruit to ripen. Ethylene affects color, texture, smell, and taste, influencing the fruit’s time it stays fresh after picking³. It’s made through a complex chain of enzymes. Many genes are found in tomatoes that help in making this ethylene. Plus, certain regulators, like RIN, control the process³.

This signaling works through a series of steps. Key players are EIN3/EIL1 and ERFs, which manage ripening genes. The parts that sense ethylene, like EIN2 and EIN3, are vital here. They help in responding to the ethylene signal for ripening³.

Climacteric and Non-Climacteric Fruits

Fruits fall into two main types: climacteric and non-climacteric. Climacteric fruits, like peaches, bananas, and apples, keep ripening after picking⁴. A rise in ethylene gas and faster breathing makes this happen⁴. Non-climacteric fruits, however, like cherries and grapes, do not ripen more after picking. They need to be fully ripe when harvested⁴.

Climacteric Fruits and Ethylene Production

Climacteric fruits are unique. They create ethylene that speeds up their own ripening⁴. This burst in ethylene is key for fruits to turn sweet, colorful, and soft⁵. Keeping ethylene levels in check helps keep these fruits fresh after picking⁴.

Non-Climacteric Fruits and Ripening

Non-climacteric fruits like oranges and strawberries don’t have a big ethylene burst to ripen⁴. Hormones like auxin and gibberellin instead help them ripen⁶. They change color and taste to attract animals that spread their seeds⁶. Some, like dragon fruit, ripen like berries but vary a lot in how they maturing⁶.

Knowing how climacteric and non-climacteric fruits ripen is critical. It helps determine the best time to pick and how to store them well⁵. With this knowledge, everyone from growers to shoppers can enjoy the finest fruit3.

Characteristic	Climacteric Fruits	Non-Climacteric Fruits
Ethylene Production	Autocatalytic increase during ripening	No significant peak in ethylene production
Respiration	Climacteric rise in respiration during ripening	No climacteric rise in respiration
Ripening Process	Can continue to ripen after harvest	Must be harvested at full maturity
Hormonal Regulation	Ethylene-dependent	Influenced by various hormones (auxin, gibberellin, jasmonic acid)
Examples	Peaches, bananas, apples, avocados	Cherries, grapes, strawberries, blueberries

“Understanding the ripening patterns of fruits is crucial for determining optimum harvest dates and post-harvest storage practices.”⁵

Recognizing the differences between climacteric and non-climacteric fruits helps everyone choose the best fruit. Growers, sellers, and buyers can have a great fruit experience⁶.

Measuring and Controlling Ethylene Levels

Ethylene Measurement

Ethylene plays a big role in making fruits ripe. To measure it, we often use gas chromatography. This tool can spot ethylene in tiny amounts⁷. By sealing fruits in a container, we can test the ethylene they give off. This tells us how ripe they are and how long they’ll last⁷.

Methods for Measuring Ethylene

Methods to check ethylene levels have gotten better for the fruit business. New sensors can find ethylene in amounts as small as 20-10 parts per billion⁸. These sensors are easy to move around and don’t cost much, less than €10,000. They help farmers and shippers watch ethylene as fruits move from the farm to the store⁸.

It’s important to measure ethylene carefully. Even a little bit, like less than 1 part per million, can start the ripening of certain fruits⁸. It’s key to keep measurements accurate, especially before the big ripening phase. This careful watch helps fruits stay fresh longer⁸.

Preharvest and Postharvest Ethylene Regulators

We can control how fruits ripen before or after picking them. Beforehand, we use things like Ethephon, ReTain®, and Harvista™. These help control ethylene and when fruits ripen⁷. After picking, 1-MCP (SmartFresh™) can stop fruits from ripening too fast. This keeps them good for a longer time⁹.

But, using 1-MCP might make fruits less tasty, lowering their flavor by 35% on average⁹. This shows it’s a trade-off. We need to find a balance between managing ethylene and keeping fruits and veggies tasty⁹.

There are other ways to handle ethylene besides with chemicals. Storing fruits in special air or packaging, or using devices that soak up ethylene, can also work. These methods keep the fruit fresh and their quality high⁷.

Tools like Ripe All Ethylene Generators and Mini Ripe Ethylene Generators use ethylene to help fruits ripen well. They make the ripening process more efficient. This leads to better quality fruits for us to enjoy⁷.

“Monitoring of ethylene concentration is not as common as O2 and CO2 monitoring in controlled atmosphere fruit stores, but research and development focus on implementing gas sensing systems for fruit monitoring, particularly for measuring CO2 and ethylene concentrations in containers.”⁸

Ethylene is crucial for fruit ripening. As we learn more about measuring and controlling it, we can do better in the fruit business. New tech and methods let farmers and shippers boost fruit quality and make them last longer. This means we get better fruit at the store⁸.

The Science Behind Fruit Ripening

fruit ripening science

The firmness of a fruit comes from its cell walls, made up of tough sugars. These include cellulose, hemicellulose, and pectin¹⁰. The breakdown of these cell walls makes the fruit soft. Enzymes help in this process by dissolving the sugars. The pressure inside the cell also affects how firm the fruit feels (turgor pressure)¹¹.

When fruits ripen, starch turns into simple sugars like sucrose, glucose, and fructose. This change adds sweetness to the fruit¹². The fruit also becomes less sour and bitter. At the same time, it starts to smell good because of new complex compounds.

Fruit ripening is complex and controlled by genes and other factors¹². Good changes happen during ripening, like a softer texture, more sugars, less tartness, better color, and a nice smell¹². But if the fruit ripens too much, it can spoil, leading to wasted crops¹².

Research shows plants can make ethylene. They produce more when their fruit is injured or cut¹⁰.
When a plant makes ethylene, it triggers enzymes that break down its cell walls and change its color¹⁰.
Plants make ethylene to signal important times, like when seeds start to grow or leaves change color¹⁰.
The way plants react to ethylene has evolved and is still a topic of research today¹⁰.

Some fruits, like bananas, really respond to ethylene by becoming sweeter¹¹. Ethylene helps ripe as well as some unripe fruits, called climacteric fruits, to ripen. Such fruits include tomatoes, avocados, apples, peaches, kiwis, and bananas. Ethylene triggers changes in these fruits as they ripen¹¹.

Scientists study special tomatoes that don’t ripen normally. By looking at these tomatoes, they learn about genes that control ripening¹². Genes like SlMADS-RIN and SlMADS-MC are very important for fruit to ripen properly¹². By studying these genes, we understand more about how fruits develop and ripen¹².

“The proverbial saying ‘one bad apple can spoil the whole basket’ is based on the practical effect of ethylene from a rotting apple accelerating the ripening of nearby apples.”¹¹

Mutations in genes like COLOURLESS NON-RIPENING (Cnr) stop fruits from ripening normally. This makes the fruit have less ethylene and changes how it ripens¹². The Cnr gene controls how other genes work, including TDR4, because of how it’s affected by methylation¹². Genes like SBP-box help regulate the ripening of different fruits, showing their role in the process¹².

Scientists are also looking at how to control and prevent fruit ripening for better shipping. They want to keep freshly picked fruit from ripening on its way to market¹⁰¹¹¹².

Conclusion

Fruit ripening is fascinating and complex. It includes many changes in the fruit’s look, taste, and feel. The process is driven largely by a plant hormone called ethylene, especially in some fruits¹³.

Knowing about fruit ripening lets us make better plans for after harvest. This includes how to handle ethylene, what makes fruits soft and sweet, and how their color changes. With this info, everyone from growers to sellers can offer top-quality, tasty fruit. They can also cut waste and increase their fruit’s value¹⁴.

The future looks bright for how we ripen fruit. New tech and better understanding mean we can expect more reliable, nutritious, and enjoyable fruits worldwide. This progress will enhance our fruit experience and keep well-loved fruits fresh and tasty for all to enjoy¹⁵.