Chapter V Storage technology and management of horticultural crops 第五章园艺产品的贮藏技术和管理 Ye Xia College of Horticulture Henan Agricultural University

The goals of storage Slow biological activity of the product by maintaining the lowest temperature and by controlling atmosphere composition; Slow biological activity of the product by maintaining the lowest temperature and by controlling atmosphere composition; Slow the growth and spread of microorganisms by maintaining low temp. and minimizing surface moisture on the product; Slow the growth and spread of microorganisms by maintaining low temp. and minimizing surface moisture on the product; Reduce product moisture loss and the resulting wilting ; Reduce product moisture loss and the resulting wilting ; Reduce product susceptibility to damage from ethylene gas. Reduce product susceptibility to damage from ethylene gas.

Section I Refrigeration 第一节 冷藏

1. Storage consideration 1. Storage consideration (1)Temperature The temperature in a storage facility normally should be kept within about ±1 °C of the desired temperature for the commodities being stored. Temperature variation is minimized with adequate air circulation.

(2) Humidity For most perishable commodities, the RH in a long-term storage facility should be kept at %. Partially dried products such as garlic, ginger, and dry onion are held at 65-65% RH. Dried nuts and fruits should be kept at 55 to 65 % RH. For most perishable commodities, the RH in a long-term storage facility should be kept at %. Partially dried products such as garlic, ginger, and dry onion are held at 65-65% RH. Dried nuts and fruits should be kept at 55 to 65 % RH.

2. Refrigeration ( 冷藏 ) Refrigeration equipment for storage facilities is generally not designed to remove much field heat from the product, since a large capacity would be required: a separate cooling facility is used for this purpose. Refrigeration equipment for storage facilities is generally not designed to remove much field heat from the product, since a large capacity would be required: a separate cooling facility is used for this purpose.

Evaporimeter Compressor Condensator Evaporimeter Compressor Condensator A schematic diagram of mechanical refrigeration 机械制冷原理示意图 Liquid receiver Regulating valve

Schematic of a typical vapor recompression, or mechanical, refrigeration system

Principle of mechanical refrigeration Principle of mechanical refrigeration 5 ． Condensers 6. Liquid storage device (refrigerant) 7. compressor 8 ． Regulating valve (expansion valve)9. evaporator 5 ． Condensers 6. Liquid storage device (refrigerant) 7. compressor 8 ． Regulating valve (expansion valve) 9. evaporator

(1) Mechanical refrigeration Most storage facilities use a refrigeration system to control storage temperature. Most storage facilities use a refrigeration system to control storage temperature. (2) Expansion valves Small mechanical refrigeration systems are controlled primarily by an expansion valve, which regulates the pressure of the refrigerant in the evaporator.

(3) Evaporators Modern cold storages usually use finned tube evaporators. Air form the storage is forced past the tubes by fans, which are a part of a complete evaporator unit.

The most common types of refrigeration compressors are reciprocating and rotary screw. (4) Compressor

(5) condensers Condensers are categorized as air-cooled or water- cooled. Small systems usually use an air-cooled unit. (6) refrigerants The choice of which refrigerant to use in a vapor recompression system is based on cost of refrigerant, compatibility, toxicity, flammability.

3. The storage building The storage building should ideally have a floor perimeter in the shape of a square. Entrances, exits, and storage areas should be arranged so that products generally move in one direction through the facility.

(1) Site selection Be available for the facility; Extending roads and energy utilities; Three-phase electrical power; Enough water to supply the evaporative condensers; Good drainage; Enough space for smooth movement of large highway trucks.

(2) Building layout Room layouts with an interior corridor offer better operating conditions for cold storages and better control of controlled atmosphere storages than designs that allow room access only through exterior doors. Room layouts with an interior corridor offer better operating conditions for cold storages and better control of controlled atmosphere storages than designs that allow room access only through exterior doors.

mechanical storage

Mini Cold Storage

The design and construction of cold storage 机械冷库的构造和设计 ① The supporting system ② The thermal insulation system ③ moisture proof system ③ The moisture proof system

① The supporting system ① The supporting system 冷库的支撑系统 The supporting system is the skeleton of cold storage and the outer structure of cold storage. The main part of insulation system are usually concrete. The supporting system is the skeleton of cold storage and the outer structure of cold storage. The main part of insulation system are usually concrete.

② The thermal insulation system ② The thermal insulation system 冷库的保温系统 Walls are insulated with fibergalsss, batts, rigid urethane foam board, or sprayed-on foam Walls are insulated with fibergalsss, batts, rigid urethane foam board, or sprayed-on foam

Insulation materials 绝缘材料

The internal structure of thermal insulation layer 保温层内部构造 Small sample panelsRoof and bottom panel Angle panel Wall boardInsulation board Cold storage insulation board

③ ③ The moisture proof system 防潮系统 A vapor barrier is installed to prevent moisture from moving through the floor, and rigid insulation is sometimes placed above the barrier and below the concrete.

Typical layouts of cold storage facilities 冷库的建筑示意图 : Storage room ； 2: Corridor; 3: Finishing room ； 4: Road Station 5: Management room ； 6: Refrigeration room; 7: Switch board room ； 8; Transformer room; 9: Pump house ； 10: Recycling pool

2 、 Principle of mechanical refrigeration 机械制冷原理 Principle of mechanical refrigeration Principle of mechanical refrigeration Refrigerating medium Refrigerating medium Pool cooling system Pool cooling system

Section II Controlled atmosphere storage 第二节 气调贮藏

Controlled atmosphere storage Controlled atmosphere (CA) storage use oxygen and carbon dioxide concentrations of about 1 to 5% for each gas in most applications. Controlled atmosphere (CA) storage use oxygen and carbon dioxide concentrations of about 1 to 5% for each gas in most applications.

CA storage conditions of some fruits and vegetables

1. Simple CA system Controlled atmosphere storage has all the design requirements of conventional refrigerated storage plus gas-tight rooms, equipment to create the desired gas concentrations, and equipment to measure and control atmospheric composition. Controlled atmosphere storage has all the design requirements of conventional refrigerated storage plus gas-tight rooms, equipment to create the desired gas concentrations, and equipment to measure and control atmospheric composition.

2. Atmosphere modification The least expensive but slowest method of modifying the storage room atmosphere is to let the product do it through natural respiration. The least expensive but slowest method of modifying the storage room atmosphere is to let the product do it through natural respiration.

3. Permanent CA facilities (1) Room size CA storages are single-story designs, with individual rooms often tall enough to allow fruit to be stacked 10 bins high, including enough height between the bins and the ceiling to allow air from the evaporator coils to mix with the room air and travel easily to the far end of the room.

Gas-tight seal using urethane foam insulation

(2) Walls and ceiling Three main types of interior wall and ceiling construction are used in recently built CA storage: foamed-in-place urethane over concrete or steel walls, plywood-covered stud walls with fiberglass insulation, and insulated, metal-covered panels. Three main types of interior wall and ceiling construction are used in recently built CA storage: foamed-in-place urethane over concrete or steel walls, plywood-covered stud walls with fiberglass insulation, and insulated, metal-covered panels.

(3) Floor Floors can be made gastight using layered or single-slab designs. An insulated floor is usually a sandwich design, with board insulation placed between two layers of concrete. Floors can be made gastight using layered or single-slab designs. An insulated floor is usually a sandwich design, with board insulation placed between two layers of concrete.

(4) Doors Most doors are 2.4 to 3 m wide and tall enough to allow a lift truck with two bins to pass through. Most doors are 2.4 to 3 m wide and tall enough to allow a lift truck with two bins to pass through. Each door should also have an access door that is 60*75 cm to allow for entry for checking fruit and making repairs without opening the main door. Each door should also have an access door that is 60*75 cm to allow for entry for checking fruit and making repairs without opening the main door.

CA storag e door

(5) Pressure relief A water trap is usually used to allow pressures to equalize. A water trap is usually used to allow pressures to equalize. Small changes in pressure can be relieved by using breather bags Small changes in pressure can be relieved by using breather bags Breather bags

(6) Pressure test The overall gas-tightness of a CA room can be tested by pressurizing it and measuring the rate of pressure drop. Pressure drops after 30 mins: Pressure >147Pa: excellent gas-tightness Pressure >147Pa: excellent gas-tightness ～ 147Pa: good gas-tightness ～ 147Pa: good gas-tightness Pressure >39.2Pa: tighter more than standards Pressure >39.2Pa: tighter more than standards Pressure < 39.2Pa: tighter less than standards Pressure < 39.2Pa: tighter less than standards

(7) Refrigeration equipment Refrigeration equipment for CA facilities is the same as for any other cold storage operation. Refrigeration equipment for CA facilities is the same as for any other cold storage operation. Most storages are designed to maintain 0 °C at 95% RH. Most storages are designed to maintain 0 °C at 95% RH.

(8) Monitoring equipment Oxygen and carbon dioxide levels must be monitored daily or more frequently to ensure that they are within prescribed limits. Oxygen and carbon dioxide levels must be monitored daily or more frequently to ensure that they are within prescribed limits. Operators have used an Orsat gas analyzer, a wet chemistry system that is fairly time- consuming to use. Operators have used an Orsat gas analyzer, a wet chemistry system that is fairly time- consuming to use. Temperature should also be monitored regularly. Temperature should also be monitored regularly.

(9) Safety consideration The atmosphere in CA rooms will not support human life, and people have died of asphyxia while working in CA rooms without breathing apparatus. The atmosphere in CA rooms will not support human life, and people have died of asphyxia while working in CA rooms without breathing apparatus. A danger sign should be posted on the door. A danger sign should be posted on the door.