Understanding Artificial Fruit Ripening

Artificial ripening of fruits is a process where chemicals or gases are used to speed up the natural ripening process. This is often done to transport green, unripe fruits over long distances without spoilage and then ripen them at the destination market.

Common Gases Used in Artificial Ripening

Naturally, the ripening of climacteric fruits (fruits that ripen after harvesting, like bananas, mangoes, apples) is controlled by a plant hormone called ethylene (${C_2H_4}$). Ethylene is a gas that promotes changes in color, texture, flavor, and aroma.

While ethylene is the natural ripening agent and is often used commercially in controlled environments, other substances have been used or considered for artificial ripening. One such substance is calcium carbide (${CaC_2}$). When calcium carbide reacts with moisture in the air, it produces acetylene gas (${C_2H_2}$).

Analyzing the Options for Artificial Ripening

Let's look at the given options and their relation to artificial fruit ripening:

• Ethane (${C_2H_6}$): Ethane is a saturated hydrocarbon and is not known to be used for artificial fruit ripening.
• Hydrogen (${H_2}$): Hydrogen is a highly flammable gas used in various industrial processes, but it has no role in fruit ripening.
• Acetylene (${C_2H_2}$): Acetylene is an unsaturated hydrocarbon. As mentioned, it is produced from calcium carbide and has been historically used for artificial ripening. Acetylene has a physiological effect similar to ethylene, inducing ripening, although it is not as effective as ethylene and its use can be problematic due to impurities.
• Nitrogen (${N_2}$): Nitrogen is an inert gas that makes up a large portion of the Earth's atmosphere. It is often used in controlled atmosphere storage to *slow down* ripening and extend shelf life, not to induce ripening.

Why Acetylene is Considered for Artificial Ripening

Acetylene is considered for artificial ripening primarily because it is produced from calcium carbide, which is relatively inexpensive and easy to transport. The chemical reaction is:

\[ {CaC_2} + 2{H_2O} \rightarrow {C_2H_2} + {Ca(OH)_2} \]

This reaction occurs when calcium carbide is exposed to the moisture present in the fruit or the atmosphere. Acetylene triggers the ripening process in fruits similar to how ethylene does.

However, the use of calcium carbide (and thus acetylene) for fruit ripening is banned in many countries due to health concerns. Commercial grade calcium carbide often contains impurities like arsenic and phosphorus hydride, which can be harmful to health upon consumption of the treated fruit.

Comparing Ripening Agents

Here is a brief comparison of ethylene and acetylene:

Conclusion on Artificial Fruit Ripening Gas

Based on the options provided and the historical use of ripening agents, acetylene, produced from calcium carbide, is a gas that has been used for artificial ripening of green fruits, despite the associated safety concerns and regulations.

Revision Table: Key Points on Fruit Ripening Gases

Additional Information: Artificial Ripening Concerns and Alternatives

While artificial ripening helps in transportation and marketing, the methods used can have implications. The use of calcium carbide is problematic because impurities like arsenic hydride (${AsH_3}$) or phosphine (${PH_3}$) can be present, which are toxic. These substances can affect the nervous system and digestive system. Safer alternatives include using ethylene gas in controlled ripening chambers, which allows for uniform ripening without the risk of toxic residues. Ethylene is a naturally occurring plant hormone and is generally considered safe when used properly for ripening purposes.