Storage system and management for horticultural crops

Storage system for horticultural crop

1. TOPIC 9: Storage systems for horticultural crops ASSOC. PROF DR MAIZATUL AKMA IBRAHIM, Ph.D

2. INTRODUCTION Throughout the period between harvest and consumption, temperature control has been found to be the most important factor in maintaining product quality . Keeping products at their lowest safe temperature ( o C for temperate crops or 10-12 o C for chilling sensitive crops) will increase storage life by lowering respiration rate, decreasing sensitivity to ethylene gas and reducing water loss. Reducing the rate of water loss slows the rate of shrivelling and wilting, causes of serious postharvest losses. Keeping products too cool can also be a serious problem. It is important to avoid chilling injury, since symptoms include failure to ripen (bananas and tomatoes ), development of pits or sunken areas (oranges, melons and cucumbers), brown discoloration (avocados, cherimoyas, eggplant), increased susceptibility to decay (cucumbers and beans), and development of off- flavors (tomatoes ). Cooling involves heat transfer from produce to a cooling medium such as a source of refrigeration.

3. Another aspect to consider when handling fruits and vegetables is the relative humidity of the storage environment. If using mechanical refrigeration for cooling, the larger the area of the refrigerator coils, the higher the relative humidity in the cold room will remain. The best method of increasing relative humidity is to reduce temperature. Another method is to add moisture to the air around the commodity as mists, sprays, or by wetting the store room floor.

4. In general, proper storage practices include temperature control, relative humidity control , air circulation and maintenance of space between containers for adequate ventilation, and avoiding incompatible product mixes. Commodities stored together should be capable of tolerating the same temperature, relative humidity and level of ethylene in the storage environment. High ethylene producers (such as ripe bananas, apples, cantaloupe) can stimulate physiological changes in ethylene sensitive commodities (such as lettuce , cucumbers , carrots, potatoes, sweet potatoes) leading to often undesirable color , flavor and texture changes.

5. COLD STORE ROOM / WAREHOUSE Temperature management during storage can be aided by constructing square rather than rectangular buildings. Rectangular buildings have more wall a reaper square feet of storage space, so more heat is conducted across the walls, making them more expensive to cool. Temperature management can also be aided by shading buildings, painting storehouses white to help reflect the sun's rays, or by using sprinkler systems on the roof of a building for evaporative cooling . Low cost cold rooms can be constructed using concrete for floors and polyurethane foam as insulation materials.

6. Building the storeroom in the shape of a cube will reduce the surface area per unit volume of storage space, also reducing construction and refrigeration costs. All joints should be carefully caulked and the door should have a rubber seal around the edges. While cooling produce, the ventilation system should be set to create an air flow rate of 100 cfm/ton (5l/sec/ton). Once cooling is completed, air flow rates should be decreased to the lowest speed that will keep produce cool (20 to 40 cfm/ton is usually sufficient ).

7. Facilities located at higher altitudes can be effective, since air temperature decreases as altitude increases. Increased altitude therefore can make evaporative cooling , night cooling and radiant cooling more feasible. Underground storage for citrus crops is common in Southern China, while in Northwest China , apples are stored in caves. This system was widely used in the U.S. during the early 1900s. Certain commodities, such as onions and garlic, store better in lower relative humidity environments. Curing these crops by allowing the external layers of tissue to dry out prior to handling and storage helps to protect them from decay and further water loss.

8. Commercially constructed cold rooms can be quite expensive, but fortunately the small-scale operator has many choices. Cold rooms can be self-constructed , purchased as prefabricated units (new or used), or made from refrigerated transportation equipment such as railway cars, highway vans or marine containers . The air composition in the storage environment can be manipulated by increasing or decreasing the rate of ventilation (introduction of fresh air) or by using gas absorbers such as potassium permanganate or activated charcoal. Large-scale controlled or modified atmosphere storage requires complex technology and management skills H owever , some simple methods are available for handling small volumes of produce.

9. Methods in temperature control Throughout the period between crop harvest and consumption, temperature control has been found to be the most important factor in maintaining product quality.   Room cooling Room cooling is a relatively low cost but very slow method of cooling when electricity for mechanical refrigeration is available. When using room cooling, produce is simply loaded into a cold room, and cold air is allowed to circulate among the cartons, sacks, bins or bulk load. This cooling method is best suited to less perishable commodities such as potatoes, onions, apples, sweet potatoes and citrus fruits, since more highly perishable crops will deteriorate too much before being adequately cooled. Room cooling is required if handling chilling sensitive crops that need to be cooled from early morning harvest temperatures to storage temperatures of 10 to 13ºC.  

10. Forced-air cooling Forced-air cooling pulls or pushes air through the storage containers themselves, greatly speeding the cooling rate of any type of produce. Many types of forced-air coolers can be designed to move cold moist air over the commodities. A portable forced-air cooler can be constructed using a canvas or polyethylene sheet. The sheet is rolled over the top and down the back of the boxes to the floor, sealing off the unit and forcing air to be pulled through the vents of the cartons stacked against the cooler. For best results and minimum cost of operation, the warm exhaust air from the fan should be directed toward the return air inside the cold room.

11. Hydro-cooling Hydro-cooling provides fast, uniform cooling for some commodities. The commodity as well its packaging materials must be tolerant of wetting, chlorine and water beating damage. The simplest version of a hydro-cooler is a tank of cold water in which produce is immersed. A batch-type hydro-cooler can be constructed to hold entire pallet-loads of produce. Conveyors can be added to help control the time produce stays in contact with the cold water.

12. Evaporative cooling Evaporative coolers can be constructed to cool the air in an entire storage structure or just a few containers of produce. These coolers are best suited to lower humidity regions, since the degree of cooling is limited to 1 to 2 o C above the wet-bulb temperature. A cooling pad of wood fiber or straw is moistened and air is pulled through the pad using a small fan. An evaporative cooler can be combined with a forced air cooler for small lots of produce. Air is cooled by passing through the wet pad before it passes through the packages and around the produce. The air can be cooled to within a few degrees of the wet bulb temperature of ambient air.

13. Night air ventilation Storage structures can be cooled using night air if the difference in day and night temperature is relatively large. The storage facility should be well insulated and vents should be located at ground level. Vents can be opened at night, and fans can be used to pull cool air through the store room. The structure will best maintain cool temperatures during the heat of the day if it is well insulated and vents are closed early in the morning.

14. Cold storage is a commercial facility that stores goods for a long period of time at a controlled temperature. Cold storage is the most effective solution for bulk handling of perishable goods, between manufacturing and retailing. Cold storage is mainly used in the food industry and various other sectors like pharmaceuticals, art painting, biotechnology, and medical, liquor industry. In today’s world where globalization and urbanization are rising so the consumption of different products and goods are rising throughout the year.

15. There are many advantages of cold storage such as:- 1- Prevents damaging of products Keeping the products safe from any spoilage is a huge task. As most of the manufacturing companies or farming is done in the outer area of the city or in another territory, before reaching the final destination, a product may hamper or may get damaged so cold storage prevents the damaging of the products . 2- Preserve the longevity of food Keeping the food fresh is one function of cold storage. The other function is to preserve the longevity of food items. Cold storage also helps people to gain access to seasonal fruits and vegetables and crops throughout the year. Most of the food items which we consume are perishable and need to be stored for a period of time. At home, we stock dairy products, fruits, vegetables, food items, in refrigerators to consume later.

16. 3 - Eases supply chain logistics Logistics is the key to our daily life, without logistics, we can’t imagine our life, there will be no globalization and urbanization. Logistic help us by delivering the products which we need from distant locations to our neighborhood . These items are transported by cold storage freight chain. Which has a huge potential . 4 -Reduce the growth of microbes All food items contain microbes, they are responsible for the various changes that happen in the life span of fruits and veggies. Food spoils due to microorganisms that eat up the food item and decompose it. The cold decreases the growth of microorganism and increase the shelf life of the food.

17. 5 - Keep the food fresh There is a nature of cold is that it preserves things, and keep them fresh, similar with food items, like in day-to-day life we store our food items in the refrigerator, to keep them fresh, similarly, companies keep food items in cold storage to keep them fresh. 6 - Adjustable Temperature Every item has a different set of properties so they need to be stored or preserved at a set temperature, so cold storage gives this facility of adjusting the temperature. Cold storage offers easily accessible temperature controls that can be used for different kinds of products like fruits, vegetables, etc . 7 - Cost-saving One of the significant benefits of cold storage is that it saves money by increasing the life of the product, it helps in preserving the product. So by helping in reducing wastage cold storage helps in saving money and the environment.

18. Recommended storage temperatures