Making Artificially Ripened Fruits Safe To Eat

Summer is at its peak in most parts of the globe and fruit fervor is high. From serene yellow mangoes and papayas to juicy grapes with green and purple hues, from luscious red litchi to blushing red watermelon, fruits platters are now adorned and buffets are worth the wait. Fruit colour which normally speaks volumes about its flavour and freshness may not always reflect challenges concealed within. Artificial ripening of fruits is one such area of food safety concern in Nepal and speculations around it needs clarity.   

It is a common practice to mass harvest mature but unripe fruits in orchards to avert losses arising from handling ripe products. Technological interventions have helped accelerate or delay fruit ripening to control market supply. The strategy is also adopted to quickly introduce seasonal fruits in the market and take advantage of the premium prices it carries. Use of banned chemical like calcium carbide is however a matter of grave concern. Published media reports in 2008 had notified the use of calcium carbide for fruit ripening in the outskirts of Kathmandu Valley and Pokhara in Nepal. In June 2022 and recently in June 2024, Department of Food Technology and Quality Control issued a public notice prohibiting the use of calcium carbide in fruit ripening and warning consumers about its health impacts. 

Ripening mechanism 

Fruit attains maturity by a natural ripening process, wherein it develops sweetness, ripe colour, softness and edibility. Ethylene, produced from methionine, an amino acid in fruit, increases intracellular levels of enzymes like amylase that hydrolyze starch yielding simple sugar. Pectinase enzyme breaks down pectin and softens the fruit. Chlorophyll is slowly replaced by red or yellow pigments like anthocyanins and carotene. Ripening however is unpredictable and is impacted by ambient humidity, heat and underlying physiological conditions. Nonuniform ripening limits its commercial prospects hence many organic and inorganic ripening substitutes are used to ensure ripening consistency. 

Research publication of a study conducted at Prithu Technical College, Dang, Nepal in 2021 compares impact of organic ripening agents and chemical ripening agent, ethephon 1000 ppm in banana. Locally available ripening agents like sun dried leaves of local plants like ashuro and dhurshilo, apple, tomato, paddy straw was used. Chemical ripening agent exhibited quickest ripening but lowest shelf life. Apple exhibited similar ripening action but contributed better shelf life. Paddy straw has been recommended for long term storage of banana. 

Artificial ripening is a mechanism wherein chemicals are used to replicate the natural process of ripening. Chemically synthesized ethylene, ethephon, ethylene glycol and methyl jasmonate are commercially used. Calcium carbide, a cheaper alternative often reported to be used, is carcinogenic in nature. Carbide reacts with moisture in fruit and releases acetylene gas which has similar ripening effect like ethylene. Commercial grade carbide is often contaminated with arsenic and phosphorous residues with toxic traits. Its impact ranges from gastrointestinal complications to peptic ulcer and neurological disorders. Ethylene glycol impacts kidney function. Direct consumption of acetylene causes prolonged hypoxia. 

In Nepal, Chapter 7, Rule (19 d) of Food Rules 2027 BS prohibits use of carbide (acetylene) for fruit ripening. In India, Prevention of Food Adulteration (PFA) Rules, 1955 prohibits the use of carbide gas for fruit ripening. Food Safety and Standards Authority of India (FSSAI) permits the use of ethylene for fruit ripening up to a concentration of 100 ppm, however, source of gas should not be in direct contact with the fruit. Is there a way to externally identify an artificially ripened fruit? A fool proof indication doesn’t exist; however, such fruits would seemingly be uniform in colour. The innate fruity flavour is often masked and shelf life is visibly shorter. Arrival of fruits in the market months before its season starts is a matter to reflect. 

Powder traces and dark blotches on fruit skins indicate chemical ripening as chemicals are often sprinkled on inner lining materials, commonly banana leaves, within wooden fruits boxes. This however, should be verified in laboratories. It is advisable to soak whole fruits in potable water and peel skin before use. Purchasing fruits from organic markets or directly from farmers is another way out. Ethylene ripening chambers normally used for large scale ripening of fruits like mango, banana and papaya are safer alternatives. 

Way forward

Consumers today have easy access to choiciest of fruits. From cycle vendors to fruit carts, shops to marts, purchasing was never so convenient. Ignorance is bliss, as the brunt of any malpractice including indiscriminate use of chemicals or use of banned chemicals can be fatal. Market monitoring by authorities and screening of imported fruits at quarantine check posts would discourage fraudulent practices. Monitoring of ripening protocols and emphasis on organic ripening agents is the way forward.  At a time when focus on healthy eating is unprecedented, assurance of food safety is a crucial prerequisite. Collaboration among stake holders including government agencies, traders, farmers, scientists and consumer forums is pivotal. Afterall, cost of human health can never surpass any amount of commercial gains.

(The author is a Food Technologist and can be contacted at monicakpg@yahoo.com.)