How does Hydrocooling extend the Shelf-life of Vegetables

How hydrocooling improves the physicochemical properties and extends the shelf-life of vegetables

What is postharvest loss?

The losses that are started after harvesting and remain until consumption are called postharvest losses, or the qualitative and quantitative loss of food in different post-harvest operations are known as postharvest losses. Postharvest operations include harvesting, handling, storage, processing, packaging, transportation, and marketing. Postharvest losses in vegetables result in poor shelf life, and nutritional and sensory quality decay, which affect the consumers’ acceptance of the product. Mechanical damage, microbial degradation, and physiological changes are the major causes of postharvest losses. Nowadays, postharvest losses are one of the major constraints on the farmer’s success. Globally, around 30% of cereal crops, 40–50% of fruit and vegetables, 20% of oilseeds, meat & dairy products, and 35% of fish losses and waste every year, especially tubers and roots are in the highest position of losses compared to all other groups (Sawicka and Barbara 2019). According to FAO, in Africa, nearly 40 percent of fruits and vegetables losses every year due to a lack of proper harvesting, handling, and storage facilities.

How does hydrocooling work to reduce postharvest losses?

There are different methods for improving vegetables’ shelf life and protecting them from nutritional decay, viz; forced air, cold water, ice and vacuum cooling (Teruel 2008). Rapid cooling is considered one of the best and most efficient methods among the various methods because it is very cost-effective, rapid and increases shelf life. Hydrocooling is a rapid cooling method using ice or cold water. After harvesting vegetables through their natural respiration process they still alive and reacts to oxygen to form carbon dioxide, water and heat. Hydrocooling removes heat from freshly harvested vegetables in the field as well as it reduces microbial activity, respiratory, transpiration, senescence, and the production of ethylene (Kalbasi-ashtari 2004). It is a simple, practical, and efficient method before packing and refrigeration of vegetables (Philosoph-Hadas et al., 1993, Franca 2015). Several experiments have been found on hydrocooling. It has been shown efficient in increasing shelf life lots of fruits and vegetables, like lychee, peach, asparagus, sweet corn, tomato, eggplant, cherry, lettuce and parsley (Becker and Fricke 2002; Alique et al. 2006; Del Aguila et al. 2009).  It ensures lower respiratory rate, lower weight losses, slowing tissue senescence, higher chlorophyll contents during storage, greater relative water content, extended shelf life, and keeping physiological aspects of the product (Moreira et al. 2019, Guimaraes et al. 2018, Franca et al. 2015, Rivera et al. 2006). Hydrocooling associated with the use of plastic bags was found very effective in several research which resulted in a lower rate of loss of fresh mass and an increased shelf life (Barbosa et al. 2015).

Hydrocooling application:

Water may be either cooled with ice, a refrigeration system, or a hydrocooling system specifically for hydrocooling produce. At first, the hydrocooling machine should be filled with fresh tap water and kept to reach 5 ± 0.5 °C water temperatures or the water tank should be filled with fresh water of the desired temperature (5 ± 0.5°C). Then the vegetables should be dumped into hydrocooled water for 05-10 minutes to apply hydrocooling treatment where reducing the initial temperature of vegetables, water is absorbed into the sample through the wall of the cell, providing a desirable firmness, crispness and turgidity (Kalbasi-ashtari, 2004; Kochhar and Kumar, 2015). In the case of manual cooling of water like; cooling water by adding ice, it is essential to maintain the water temperature (5 ± 0.5 °C). A thermometer must be used in the container to monitor the water temperature during the application periods and the addition of water and ice should be done to maintain the temperature. After the application of hydrocooling the vegetable should be dry at room temperature to reduce the excess water. After reducing the excess water, vegetables should be packaged for storage and transportation.

Benefits of hydro cooling system:

1. It is a simple and quick method of cooling after harvesting
2. It reduces microbial activity and increases shelf life
3. It allows the combination of both cooling and cleaning operations
4. Reduce losses of vegetables and farmers can get premium price
5. It preserves flavor, aroma, appearance and texture
6. It maintains the nutritional qualities of vegetables
7. A convenient method of postharvest cooling on a large scale
8. Strengthen cell wall which allows better transportation

Conclusion

Hydrocooling is one of the easiest ways of pre-cooling the vegetables after harvesting. It is economically viable and it allows lower microbial activity, extends shelf life, preserves nutritional and sensory quality, better transportation as well as reduces the losses of vegetables. Vegetables with better quality and shelf life become more attractive to consumers and farmers can gain a premium price for their hydrocooled produce.

If you want read the relevant research paper: Effect of Hydrocooling and Storage Condition on Postharvest Quality of Coriander Leaf

References:

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5. 2019. FAO partnerships working for the Sustainable Development Goals. https://www.fao.org/3/ca6344en/ca6344en.pdf
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