India is the largest producer of fruits and second largest producer of vegetables in the world. In spite of that, per capita availability of fruits and vegetables is quite low because of post-harvest losses, which account for about 25% to 30% of production. Besides, quality of a sizable quantity of produce also deteriorates by the time it reaches the consumer. Most of the problems relating to the marketing of fruits and vegetables can be traced to their perishability. Perishability is responsible for high marketing costs, market gluts, price fluctuations and other similar problems.
At low temperature, perishability is considerably reduced and the shelf life is increased and thus arises the importance of cold storage or refrigeration. The first cold store in India was reported to have been established in Kolkata (then Calcutta) in 1892. However, significant progress in the expansion of the cold storage industry in the country has been made only after independence. This has been done with a view to ensuring the observance of proper conditions in the cold stores and to providing for development of the industry in a scientific manner, cold storage facility accessible to farmers. It will go a long way in removing the risk of distress sale to ensure better returns.
Storage of Foods and Storage Conditions
Foods and many other commodities can be preserved by storage at low temperature, which retards the activities of micro-organisms. Micro-organisms are the spoilage agents and consist of bacteria, yeasts and molds. Low temperature does not destroy those spoilage agents as does high temperature, but greatly reduces their activities, providing a practical way of preserving perishable foods in their natural state – which otherwise is not possible through heating. The low temperature necessary for preservation depends on the storage time required often referred to as short- or long-term shortage and the type of product.
In general, there are three groups of products:
- Foods that are alive at the time of storage, distribution and sale e.g., fruits and vegetables,
- Foods that are no longer alive and have been processed in some form e.g., meat and fish products, and
- Commodities that benefit from storage at controlled temperature e.g., beer, tobacco, khandsari, etc.
Living foods such as fruits and vegetables have some natural protection against the activities of micro-organisms. The best method of preserving these items is to keep the product alive and at the same time retard the natural enzyme activity that will retard the rate of ripening or maturity.
Preservation of non-living foods is more difficult since they are susceptible to spoilage. The problem is to preserve dead tissues from decay and putrefaction. Long-term storage of meat and fish products can only be achieved by freezing and then by storing them at a temperature below -15°C. Only certain fruits and vegetables can benefit from freezing. However, for fruits and vegetables one should be very careful about the recommended storage temperature and humidity — a deviation from which will have adverse effect on the stored product leading to even loss of the entire commodity.
Products such as apples, tomatoes, oranges, etc., cannot be frozen and close control of temperature is necessary for long term storage. Some products can also be benefited by storing under controlled atmosphere and modified atmosphere conditions. Dairy products are produced from animal fats and therefore non-living foodstuffs. They suffer from the oxidation and breakdown of their fats, causing rancidity. Packaging to exclude air and hence oxygen can extend storage life of such foodstuffs.
Heat load factors normally considered in a cold storage design are:
- Wall, floor and ceiling heat gains due to conduction
- Wall and ceiling heat gains from solar radiation
- Load due to ingression of air by frequent door openings and during fresh air charge.
- Product load from incoming goods
- Heat of respiration from stored product
- Heat from workers working in the room
- Cooler fan load
- Light load
- Aging of equipment
- Miscellaneous loads, if any
Cold Storage Cooling Technology
A cold storage unit incorporates a refrigeration system to maintain the desired room environment for the commodities to be stored. A refrigeration system works on two principles:
- Vapour absorption system (VAS), and
- Vapour compression system (VCS)
VAS, although comparatively costlier, is quite economical in operation and adequately compensates the higher initial investment. Wherever possible such a system should be selected to conserve on energy and operational cost. However, it has its own limitations when temperature requirement is below 10°C and many of the fruits and vegetables except seeds, mangoes, etc. require lower than 10°C for long storage.
VCS is comparatively cheaper than VAS. There are three types of VCS systems available depending upon the cooling arrangements in the storage rooms, i.e., diffuser type, bunker type and fin coil type. Diffuser type is comparatively costlier and is selected only when the storage room heights are low. The operational cost of such units is also higher. Bunker type is the cheapest and is preferred when storage room heights normally exceed 11.5 m. Its operational cost is also low. Fin coil type, although about 5% costlier than the bunker type, is very energy efficient with low operational cost and higher space availability for storage of produce. Such system is used for units with room heights of 5.4m onwards.
In a refrigeration system, refrigerants are used to pick up heat by evaporation at a lower temperature and pressure from the storage space – and give up the heat by condensation at a higher temperature and pressure in a condenser. Freon was being used to be a common refrigerant – but as it causes environmental degradation, its use was banned by the year 2008. Therefore, Ammonia is being increasingly used and preferred for horticultural and plantation produce in cold storage units.
Status of Cold Storage and Its Potential in India
Cold storage solutions emerge as a critical bridge between changing consumer needs, supply chain optimisation, and decreasing food waste in India’s dynamic food environment. The growth of organised retail, increasing consumer tastes, and rising demand for processed foods highlight the importance of effective cold storage systems (Figure 1). Cold storage facilities help solve problems by preserving perishable items, decreasing food waste, boosting agricultural diversity, and assisting with food processing and exports. Technological improvements, energy efficiency, and adherence to hygiene requirements are all important factors in optimal cold storage architecture. As India’s population grows and demand for food items rises, cold storage facilities become not just a need but also a critical component of food security and economic prosperity. The sector has enormous potential, with chances to improve the whole food ecosystem while maintaining a steady supply of high-quality products for customers.
The estimated annual production of fruits and vegetables in the country is about 130 million tonnes. This accounts for 18% of our agricultural output. Due to diverse agro climatic conditions and better availability of package of practices, the production is gradually rising. Although, there is a vast scope for increasing the production, the lack of cold storage and cold chain facilities are becoming major bottlenecks in tapping the potential. The cold storage facilities now available are mostly for a single commodity like potato, orange, apple, grapes, pomegranates, flowers, etc., which results in poor capacity utilization.
The cold-chain industry in India is still at a nascent stage and despite large production of perishable produce, the cold-chain potential remains untapped due to high share of single commodity cold storage. For instance, about 60% of the cold storage capacity is concentrated in the states of West Bengal, Uttar Pradesh and Bihar, wherein storage of potatoes accounts for 85-90% of the capacity. The other reasons are: high initial investment (for refrigerator units), lack of basic infrastructure (roads, water supply, power supply, drainage, etc.), lack of awareness for handling perishable produce and lapse of service either by the storage provider or the transporter leading to poor quality produce.
Latest Trends in Cold Storages Technologies
India’s cold chain logistics industry has expanded significantly in recent decades. There is rising demand for effective and dependable cold chain solutions across the nation. The use of cutting-edge technologies like Internet of Things (IoT), Automated Guided Vehicles (AGVs), Automated Storage or Retrieval Systems (As/Rs), Advanced Sensors and Vision Systems, Enhanced Visibility and Communication Systems etc., is quite prevalent these days.
Conclusion
There is growing importance of the cold chain. As mentioned above, cold chain infrastructure is a critical tool to reduce post-harvest losses and is of utmost importance to the overall food security of India. This requires ensuring food security by increasing production and eliminating wastage of food and livestock in the entire supply chain. This will not only increase food security but also create more employment opportunities and increase producers’ income and exports.
Dr. (Prof.) D.B. Jani received Ph.D. in Thermal Science (Mechanical Engineering) from Indian Institute of Technology (IIT) Roorkee. Currently he is a recognized Ph.D. Supervisor at Gujarat Technological University (GTU). He has published more than 180 Research Articles in reputed International Conferences and Journals. He has also published 5 reputed books in the area of thermal engineering. Presently, he is an Associate Professor at GEC, Dahod, Gujarat Technological University, GTU, Ahmedabad (Education Department, State of Gujarat, India). His area of research is Desiccant cooling, ANN, TRNSYS, and Exergy.
