Discussion on Preservation, Storage and Transportation of Flower after Harvest (7)

(2) Gas storage and preservation

Including air-conditioned storage (MA) and air conditioning storage (CA) two. CA storage refers to adjusting the ratio of the gas components of the storage compartment to a desired ratio. This storage method is based on the theory that when the product is stored, its metabolic process can be slowed down by lowering the O2 concentration and increasing the CO2 concentration. Atmosphere changes mean changing the atmospheric composition around the plant to make it different from the natural atmospheric composition (78.08% N2, 20.95% O2 and 0.03% CO2). It is usually to reduce the O2 concentration and increase the CO2 concentration. There are various ways to regulate the atmosphere around the storage product, and the ideal gas concentration can be obtained when CA is stored. MA storage, that is, the product is placed in an environment where the gas is not free to flow (package or room), and the composition of the air has changed due to the breathing of the product.

MA and CA storage must maintain proper temperature and relative humidity. The use of MA is either beneficial or harmful depending on the species, breed, physiological age, atmospheric composition, type of packaging film, temperature and storage period, which helps to explain why there are often very large differences in the storage results for a given product. MA can be used in the transportation of horticultural products, short-term storage and long-term storage for fresh sales and processing.

Storage in various types of plastic bags (different materials, labels, individually sealed packages), and low pressure storage are other types of MA storage.

For CA storage, the room must be isolated as it must be sealed during cooling to maintain the desired atmospheric composition. By adjusting, the product can maintain its ideal atmospheric composition, or change the composition of the atmosphere through an atmospheric generator (the latter is faster, only 1 to 2 days, and the former needs 14 to 20 days, depending on the amount of the product and the size of the room). Today, CA storage can be done by removing O2, replenishing liquid N2, or replenishing N2 from a separator (N2 generator). There are various ways to remove CO2 (eg, water available, lime hydrate or a mixture of potassium carbonate and potassium bicarbonate, molecular sieves and activated carbon). On the contrary, if the increase of dry ice can increase the CO2 concentration, CO2 and liquid nitrogen are used together for the long-distance transportation of perishable products, which can achieve the dual purposes of cooling and MA storage. By controlling the content of oxygen and carbon dioxide stored in cut flowers, the purpose of reducing the respiratory rate, reducing nutrient consumption, inhibiting ethylene production, and prolonging cut flower life can be achieved. Due to different varieties of cut flowers, the amount of CO2 is controlled at 0.35% to 10%, and the content of O2 is controlled at 0.5% to 1%, which can achieve good preservation effect. Nitrogen also has a good effect of keeping fresh, daffodil is 10% nitrogen, temperature 4.5 °C, storage for 3 weeks after the flower is still bright, branches and tall and straight.

The atmospheric composition in the CA room is harmful to humans. Without proper breathing equipment, working in a CA room is life-threatening. Danger warnings should be posted on the door. When entering the room, there should be at least 2 persons carrying respiratory equipment at all times.

Another simple method of air-conditioning storage is air-conditioned storage in plastic films. Plastic bags of various thicknesses and sizes are used for commercial packaging of products. It is both beautiful and protects the product, prolongs the storage period of MA, does not have comprehensive plastic raw material or thickness, and can be widely used in various packaging. The most suitable film depends on the purpose of the packaged product. A common problem with plastic bag storage is the loss of quality due to the occurrence of microorganisms (mostly fungi). At the same time, when products are stored in plastic bags, various physiological disorders occur. Therefore, for various products, it should be considered whether it is really necessary to use plastic bags for short-term or long-term storage.

(3) Storage under vacuum

When the atmospheric pressure around agricultural products is reduced, the content of various gases in the atmosphere is also reduced. This means that by reducing the atmospheric pressure, eg, to half of normal atmospheric pressure, the level of O2 in the air is also reduced to approximately 10.5%, the effect of CA storage can also be obtained by the low pressure storage method, and the ethylene content is lowered. Studies on low-pressure storage (LPS) of avocados have shown that although low-pressure storage results in a longer shelf life of fruits, they still have a negative effect. For example, when stored at 50 mmHg, avocados lose moisture and harden. The most important factor for the inapplicability of this method of application is the economic factor. The cost of establishing a storage room is large, and there are many technical problems. Moreover, the advantages of this method worth investing are not great, and the maintenance is also more complicated.

Reducing the atmospheric pressure below the standard atmospheric pressure can delay the ageing process of cut flowers in the storage room, and its life span is much longer than that under atmospheric pressure. Experiments have shown that Gladiolus can be stored for 7 to 8 days under atmospheric pressure at 0°C, but can be stored for 30 days at 60 mmHg and stored at -2°C to 1.7°C.

(4) Radiation preservation

Irradiation of roses, chrysanthemums, dahlias, and other cut flowers with 2-10 GyCO 60 y rays has an effect on preservation. If 10Gy-irradiated rose cut flowers, the fresh-keeping rate reached 75% after 15 days.

(to be continued)