3. CHEMICAL AGENTS USED FOR ARTIFICIAL RIPENING Ethylene is the major ripening agent produced naturally within the fruits which initiates the process of ripening. There are multifarious uses of many ripening agents to release ethylene in order to speed up the ripening process. Chemicals like ethanol, methanol, ethylene glycol, Ethephon, calcium carbide are used to ripen fruits and vegetables artificially. The use of calcium carbide is much widespread in many regions of south Asia including India, Bangladesh, Nepal and so forth for its cheaper market price despite its ban due to its harmful feats. Ethylene: A very small concentration (1 ppm) of ethylene in air is sufficient to promote the fruit ripening process. Externally applied Ethylene is likely to trigger or initiate the natural ripening process of apple, avocado, banana, mango, papaya, pineapple and guava, and therefore, can be marketed before the predicted time. Calcium Carbide: Calcium Carbide is widely used in different parts of the world [10]. Once applied on the fruits Calcium Carbide comes into contact of the moisture and releases acetylene, which has fruit ripening characteristics similar to ethylene.
The reaction is: CaC2 + 2H2O = Ca (OH) 2 + C2H2
Industrial grade calcium carbide contains traces of arsenic and phosphorus hydride, which are hazardous for human health in direct contact. Ethephon: Ethephon is another agent which is used to artificially ripen fruits. Ethephon is often considered better than calcium carbide because pineapple, banana and tomato treated with 1000 ppm of ethephon required less time for ripening (48, 32 and 50 h, respectively) than other treated fruits as well as compared with the nontreated fruits. The fruits ripened with ethephone have more acceptable colour than naturally ripened fruits and have longer shelf life than fruits ripened with CaC2. Ethephon is decomposed into ethylene, bi-phosphate ion and chloride ion in aqueous solution. The released ethylene further fastens up the ripening process.
4. Possible Health Hazards Calcium Carbide releases acetylene which almost works like ethylene in terms of speeding up the ripening process. Direct consumption of acetylene has been found to be detrimental as it reduces oxygen supply to the brain and can further cause prolonged hypoxia [6]. Calcium Carbide is alkaline in nature and irritates the mucosal tissue in the abdominal region. Cases of stomach upset after eating carbide-ripened mangoes has been reported recently [9]. Even though eating the carbide-ripened fruit does not lead to any allergic reaction instantly, seizure headache, sleepiness may be faced while applying these chemicals on the fruits. Impurities like arsenic and phosphorus found in industrial grade calcium carbide may cause serious health hazards when workers are in direct contact with these chemicals while applying the ripening agents. This may cause dizziness, frequent thirst, irritation in mouth and nose, weakness, permanent skin damage difficulty in swallowing, vomiting, skin ulcer, and so forth [9]. Higher exposure may cause undesired fluid buildup in lungs (pulmonary edema).
6. Critical Analysis on Fruit Quality and Nutrition Values Researchers from different disciplines are working to assess the health hazards associated with fruit ripening agents. To evaluate the relevant health hazard it is critical to quantify the toxic concentration within the chemically-ripened fruit skin and flesh. In different studies, sample fruits are collected from local market rinsed in water and analyzed rinsed water to identify the presence of ripening agent(s) on the fruit skin; this methodology may not confirm or quantify the presence of chemicals within fruit-flesh. There are few studies reported the presence of chemicals within fruit-flesh and have addressed the changes of biochemical and nutritional properties of fruits because of treating with fruit ripening agents. Wills et al (2007) have reported the ethylene concentration in a wide range of artificially ripened fruits: apple, pear, peach, avocado, banana, lemon, pineapple, orange, and lime. Hakim et al (2012) have collected Pineapple and Banana samples from different Bangladeshi local markets and compared to the naturally ripened and lab treated (using Ethephone) Pineapples and Bananas. They have found that chemically ripened Pineapples and Bananas have higher sugar content than nontreated samples; other fruit nutrition values like Vitamin C and ß-carotene are higher in naturally ripened fruits. They also have reported the presence of Lead (Pb) in chemically ripened (market and lab treated) pineapples and bananas, and Arsenic (As) in pineapples collected from market). The daily permissible intakes of Pb and As for adults are 600 μg/day and 16.7-129 μg/day, respectively. The average daily consumption of fruits for an adult is in between 100 to 150 gm. Therefore, the possible daily intake of Pb and As from fruits would be 12-50 and 2.5- 3.75 μg/day respectively, which is within the acceptable limit for an adult. Nonetheless, further studies must be conducted regarding the effects of long term consumption of such elements in fruits. Besides, in many developing countries, the potential sources of chemical contamination of fruits and vegetables include the usage of pesticides during the harvesting process, preservatives at the post-harvesting process. Therefore, to correctly assess the health hazards related with ripening agents, it is not only essential to consider their effects on the fruit’s quality, but also the qualitative and quantitative analysis of the impurities associated with ripening agents, other possible sources of chemical adulteration, and their aftereffects on the nutrition value, taste and shelf life.