HORT 111 T7

• Storage


  A value-adding activity, to wait for the appropriate time to transport, market, and utilize or consume the produce
• Storage at farm


  1. Start of temperature management (e.g. avoid heat exposure)

  2. Sort, clean, & store only quality produce

  3. Storage usually temporary & non-refrigerated, if no cold facility

  4. Observe proper Environment (temperature, etc.), Sanitation and Product (ESP) management during storage

  5. Temporary (non-refrigerated/refrigerated) or long-term (refrigerated)
• Storage in packinghouse


  1. Non-refrigerated and refrigerated storage

  2. Observe ESP
• Storage in markets


  Non-refrigerated and refrigerator
• Cold/refrigerated storage


  Most effective method of maintaining fresh produce quality, enabling high flexibility in distribution & marketing at optimum time
• "Without refrigeration (cold storage), development and modernization of a country will not take place." (IIR)
• Temperature


  Most important factor determining produce quality. Low temperature management in refrigerated system is very vital.
• Cold storage


  1. Maintaining constant temperature

  2. Precooling is removing field heat and is important before cold storage
• Cold room (cool store)


  A large, thermally insulated box, with doors for entry and a system of cooling the interior

  
• A farmer who can cool and store produce has greater market flexibility – no need to market immediately after harvest. For small farmers, the problem is set-up cost.
• Setting up a cold storage facility

  1. Can be constructed in commercial packinghouses, at produce collection points, trucking stations, dry ports or in close proximity to airports or harbors

  2. Critical considerations: Drainage, Electricity, Water, Adequate waste water disposal

  
• Size and design of a cold storage facility

  • Determined based on volume of produce to be stored, produce container, volume required per container, aisle space needed, lateral & head space appropriate to height of stored produce, available site space
• Cold room construction


  1. Must have sufficient insulation in walls, ceiling and floor to maintain heat flows of <0.3 kJm-2h-1

  2. Vapor barrier of thick polyethylene or other equivalent material on warm side of insulation

  3. Common method is to use sandwich panels, polystyrene foam clad with thin sheet of steel or aluminium, for the walls and ceiling, erected on an insulated concrete slab laid on a vapor barrier of thick polyethylene film

  4. Foamed in polyurethane, which includes a fire retardant, is another modern insulating material

  5. Insulation thickness: Polyurethane - 7 cm, Polystyrene panels - 10 cm, Rockwool bats - 13 cm, Softwood sawdust - 25 cm, Hardwood sawdust - 57 cm, Solid concrete - 660 cm
• Cold room construction


  1. Must be constructed in covered structure to reduce heat load

  2. Insulated doors should be large enough to allow easy entry and exit of largest single loads in & out of cold room

  3. Provide air or plastic curtains in doors to reduce warm air infiltration

  4. Closed loading docks should be used for loading and unloading refrigerated trucks to prevent cooled produce coming in contact with warm air

  5. Closed docks also prevent reinfestation of produce that has undergone a quarantine disinfestation treatment
• Cooling/refrigeration system


  • Direct and indirect expansion system

  
• Direct expansion refrigeration system (induced draft)


  • Most commonly used
• Temperature and RH requirement

  • Temperature in cold room must be kept within 1oC of desired level
  • To prevent temperature variation, cold room must be well insulated and adequately refrigerated with good air circulation
  • Alternating cold/warm temperatures result to sweating on product surface, which may hasten decay

  
• Temperature and RH management

  1. Use thermometers for temperature measurement, thermostats to control the operation of refrigeration units, and manual temperature controls that must be periodically checked

  2. RH in cold room can be controlled using a humidistat and monitored with a recording hygrometer

  3. RH in cold rooms can be increased by adding moisture, regulating air movement and ventilation, maintaining temperature of refrigeration coils, providing moisture barrier insulate walling, wetting the floor

  
• Recommended storage temperature and RH for selected fruit


  • Source: Yaptenco et al., 2007
• Proper storage practices


  1. Temperature and RH control

  2. Proper air circulation

  3. Maintenance of space between containers for adequate ventilation

  4. Avoidance of incompatible mixes of produce

  5. Managing the in flow and out flow of produce

  6. Product inspection to sort out decayed produce

  
• First in First Out (FIFO) system


  Should be used in management of produce within cold room
• Precooling before loading cold room


  If not pre-cooled, daily intake of produce in cold room should not exceed 10% of cooling capacity
• Proper storage practices include: temperature and RH control, proper air circulation, maintenance of space between containers for adequate ventilation, avoidance of incompatible mixes of produce, managing the in flow and out flow of produce, product inspection to sort out decayed produce
• Cold storage


  Produce must be sorted and only produce of marketable quality should be stored
• Cold room preparation

  1. Appropriate temperature for 3d before loading produce

  2. Rooms without floor insulation may take a week to equilibrate
• Failure to pre-cool the cold room

  • May cause slow cooling and excess water loss from produce

  
• Packaging of produce in cold room


  1. Gaps of 1 cm between adjacent packages

  2. Even distribution of cool air throughout the room and around packages

  3. Minimum gaps: 8 cm between stacks of produce & walls and between floor & stack; 20 cm between drip trays under the evaporator and top of stack
• Bulk bins containing 200-500 kg of produce


  • Should have air gaps in the floor of 8-10% of base area
• Inventory information


  • Type and quantity of produce
  • Harvest date
  • Packing date
  • Pre-cooling method used
  • Storage entry date
  • Any special handling procedures
• Cold storage infrastructures


  • Cold rooms in a covered structure (building) with receiving/dispatching area, packinghouse, storage room for packages and other implements, closed loading docks, and workers' washing and preparation area
  • Forklifts, pushcarts
  • Pallets, storage racks
  • Temperature/RH monitoring devices
  • Sanitation equipment/apparatus

  
• Precooling


  Rapid cooling of a commodity to the required transit or storage temperature
• Need for precooling


  • To remove field heat and slow down physiological processes
  • To reduce load in the refrigeration system
  • To slow down the rate of decay or inhibit microbial growth
  • To inhibit water loss
• Air or Room Cooling


  • Uniform air distribution
  • Spaced stacking
  • Adequate ventilation
  • Slowest cooling rate

  
• Forced Air Cooling


  • Forces cool air to move through containers
  • Faster than room cooling
  • Sufficient vent areas in containers (5-6% of area perpendicular to direction of air flow)

  
• Forced Air Cooling


  1. Cold rooms

  2. Pallets

  3. Tarpaulin

  4. Mobile or fixed auxiliary fan

  5. 6-10 times faster than room cooling

  
• Forced Air Cooling


  Gaps/Spaces to be maintained for air movement: 0.6-1.2 m, 0.6-1.0 m, 0.3-0.6 m

  
• Hydrocooling


  • Water is a very efficient medium
  • 2-4 times faster than forced air cooling
  • Commodities should not be sensitive to wetting
  • Requires water-resistant containers
  • Water should be chlorinated
• Hydrocooling methods


  • Batch
  • Immersion
• Vacuum Cooling


  • Water boils at lower temperature under vacuum
  • Very rapid cooling
  • 6ºC cooling per 1% weight loss
  • Very costly, need technical skills, continuous use to be economical
• Vacuum Cooling


  • Requires air-tight chamber, pump, large volume of produce to be precooled