Sci-Tech

Irradiated papaya has high shelf life

Some specialists feel that the terms “super fruits” and “super foods” are used by marketing gurus as promotional gimmicks. The topic became so exciting that in July 2013, the Food and Agriculture Organization organized an International Symposium on Super fruits: Myth or Truth, “to determine whether there were nutritional and agronomical evidence to support the claim of a fruit (species and varieties) being a “super fruit” and whether these were adequate to provide a definition”.

One of the papers at the symposium referred to the humble papaya as “super food for the skin”. Most super fruits, including papaya have short shelf-lives. Scientists from the Bhabha Atomic Research Centre (BARC) have developed notable processing methods to make papaya a high shelf life super-food.

They noted that papaya fruit is highly perishable resulting in around 25 per cent postharvest loss which is further enhanced during storage and transportation. They developed a novel combination technology including osmotic dehydration, blanching and infrared drying to make intermediate moisture (IM) papaya cubes to prevent these losses.

They further hygienised these cubes after packing them and exposing them to a gamma radiation dose of 2 kGy. (Gy, a unit of radiation dose, represents energy absorption of one joule per kg; kGy is 1000 Gy). In their study, they packed the intermediate moisture (IM) papaya cubes (20 pieces; approx. 50 g/packet) in low density polythene packets. Radiation processing helps to reduce the microbial load.

Believe it or not, the final product could be stored up to 60 days at ambient temperature. The unprocessed freshly cut samples get spoiled within 2 days!

Scientists secured other benefits. They demonstrated that processed IM cubes showed nearly 5-fold increase in calorific value; the per unit dry weight content of carbohydrate, protein, fibre, and functional bioactives such as ascorbic acid, carotenoids, and phenolics including flavonoids were found to increase significantly.

Researchers quantitatively demonstrated that the functional properties in terms of antioxidant capacity and antimutagenic potential were improved in the final product. Writing in Food Bioscience journal (Feb 25, 2015) they concluded that they could control the postharvest losses of this highly perishable fruit by transforming it into a more stable product.

“The developed product was found to be microbiologically safe and showed better nutrient content per unit mass with respect to the fresh fruit, and therefore enhanced functional properties.” They added.

The authors listed many interesting facts about papaya. Annual production of the fruit worldwide is about 11 million tons (t). India produces about 4.7 million tons. Our export is a measly 18,000 t! According to the scientists, the major reason for the marginal export is the highly perishable nature of the fruit, which is often susceptible to fungal attack during storage and transportation. The fruits need tender care in handling. . The softness that occurs during ripening of the fruit further accelerates the spoilage. Papaya has to be preserved at the right temperature. Storage below 10 degree Celsius causes chilling injury to the fruit.

According to the National Horticulture Board, the economic life of the papaya plant is only 3 to 4 years. Papaya plant needs heavy doses of manures and fertilizers. In one estimate, the NHB showed that the break-even point is reached in the 3 year. Such considerations do come in while evaluating the financial viability of papaya cultivation.

My queries revealed that the most important aspect in the cost effectiveness of the BARC technology is that it provides a mechanism to reduce the post–harvest losses. Secondly, it makes available a convenient ready-to-eat (RTE), ambient storable, and microbiologically safe papaya cubes to the consumers. Thirdly, the product is of high calorific and nutritional value on dry weight basis compared to the raw ripe papaya.

Evidently, these attributes can compensate for the seemingly non-negligible processing cost. Also, it can provide a useful technology which will benefit the papaya farmers in due course.

The public unhesitatingly buys the insipid noodles, pastas and pizzas; they often get carried away by telling advertisements and even endlessly long controversies! It is surprising that they do not even look benignly at the genuinely nutritious products such as the papaya cubes which could be produced by the BARC technology.

ksparth@yahoo.co.uk

(The writer is former Secretary, Atomic Energy Regulatory Board)

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Printable version | Sep 25, 2020 9:02:41 AM | https://www.thehindu.com/sci-tech/Irradiated-papaya-has-high-shelf-life/article14401260.ece

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