How to preserve pears?

Storage and preservation conditions of pears

1, temperature:

Temperature is the most important environmental condition for pear storage, and different varieties need different storage temperatures. Generally speaking, the suitable storage temperature is-1 ~ 2℃. Storage temperature should not be too low, too low fruit will produce chilling injury. The freezing point of pear is-1.8 ~ 3℃. If the temperature is below freezing point, pears will suffer from chilling injury. The storage temperature should not be lower than 0℃, but it should not be higher than 5℃. If it exceeds 5℃ for a long time, it will accelerate the senescence of fruits and increase the rot rate.

2. Humidity:

Humidity is also one of the important conditions for storing pears. After the pear fruit is harvested, water evaporates through the pores of the peel. Too much water loss will shrink the peel, which will not affect the appearance, but also affect the quality of pear fruit. Therefore, pears need suitable air humidity during storage. Generally, the relative humidity should be kept at 90% ~ 95%, and it should be kept at 85% ~ 95% in cold storage. The degree of water loss varies from pear to pear during storage.

Second, the factors affecting the storage tolerance of pears

To sum up, the factors affecting the storability of pear fruit are as follows.

1, variety characteristics

Crispy varieties, such as Yali pear, Xuehuali pear, Huangxian Changba pear, Qixia fragrant pear, the pulp is always hard, even at room temperature. Many soft meat varieties, such as western pears, are not resistant to storage. The flesh of this variety is thick and hard when it is harvested, and it can only be eaten after the fruit is ripe and softened. However, when the pulp becomes soft, it will rot quickly, and the aging can only be delayed in cold storage (8 ~ 5℃) or controlled atmosphere.

Both of them are crispy meat varieties, and the varieties with coarse pulp and relatively little juice are more resistant to storage; Juicy varieties such as Huangxian Changba Pear, Qixia Xiangli Pear and Xuehua Pear are more resistant to storage than Yali Pear, Wangli Pear and Jinfeng Pear.

Step 2: mature

Early harvest, immature fruit, low sugar and acid content, less respiratory consumption components, not resistant to storage; When the fruit is harvested too late, the pulp cells are easy to age, and the aging process of the fruit is accelerated, which is not resistant to storage. Only pears harvested at the right time can be stored for a long time. Cultivation conditions such as watering, fertilization and soil texture have important effects on the storage resistance of pears. If the chemical fertilizer is applied too much, especially when the nitrogen, phosphorus and potassium are less, the flavor of pears will become weak, the sugar content will be low, and the storage resistance will decrease.

Calcium deficiency in soil will cause pear scab. Pests and diseases were not controlled in time. Cone rot can lurk for a long time after it infects fruit, and symptoms will appear when it rains. Once it enters the storage period, it will quickly get sick and cause fruit rot. The injured part is a fruit with a dense wound, which is easily infected by Penicillium during storage and can also cause rot. Therefore, strengthening pest control is an important aspect to improve the storage resistance of pears.

In addition, the management technology in the storage process is also related to the storage tolerance. The pre-cooling degree of stored fruits, the cooling rate at the initial stage of storage, the humidity adjustment and ventilation in the warehouse will all affect the storage resistance of fruits.

Three, pear storage and preservation technology

Different varieties of pears have different storability. Among them, Yali pear, Laiyang pear, Qixia perfume, Qixia perfume, Pak Lei, Xuehuali and Dangshan crisp pear are of good quality and storability. Some pears with many stone cells, such as Shanxi stupid pear and yellow pear, have strong storage resistance. Pears such as Yali pear, Xuehua pear, Laiyang pear and Changba pear are prone to browning in the storage process, mainly because these pears are sensitive to low temperature or carbon dioxide, so attention should be paid to gradually cooling down and low or no carbon dioxide storage during storage.

There are many storage methods of pears, such as ditch storage, ridge storage, indoor storage, cold storage, modified atmosphere storage and so on.

1, ridge stacking method.

This is one of the main methods to store pears in Changba, Huangxian County. This method is also suitable for the storage of Guoguang, Red Fuji, New Jonagin and other varieties of apples, as well as apple pears, Pak Lei, Qixia perfume and Qixia perfume. Before picking pears, choose well-ventilated, cool and dry fruit trees with low water level. The boundary is built along the north-south direction with a width of 1.5 ~ 2m, and the length of the boundary depends on the storage capacity. The border is about 10 cm higher than the ground, slightly higher in the center and slightly lower on both sides, and the ridge height around it is about 15 cm. The boundary is covered with a layer of fine sand with a thickness of 5 ~ 10 cm. On the four corners and two long sides of the ridge, a wooden column is nailed every 750 mm, the height of the wooden column is 750 mm, and half of it is inserted into the soil. Inside the wooden column, a curtain made of sorghum, corn stalks or Vitex negundo is erected along the four sides of the ridge, and two layers of imperforate kraft paper are tightly attached in the curtain, and the indirect ends of the paper should be pressed and overlapped with each other. After the fruits are harvested, they are stored in ventilated and cool trees in advance, and stored in the border after the first frost. When storing, first spray water on the sandy soil with dry boundary, pick out the crushed, pricked and damaged fruits, and put pears layer by layer. Handle with care when placing, so as not to bump and stab pears during storage and cause rot. The pear tree pile top is placed in a small arc, with the periphery as high as the side hole, and the vertical height of the middle pile top is about 70 ~ 80 cm. After the fruit is shaped, cover the seal with 2 ~ 4 layers of kraft paper, and then cover it with a straw curtain.

In order to strengthen the internal ventilation, a certain number of ventilation handles are often erected in the fruit bed. The length of the inflatable handle is slightly higher than the top of the fruit pile, and one is erected every 3 meters. When the outside temperature is greater than 0℃, we should pay attention to the use of low temperature at night, that is, cover the straw curtain and kraft paper during the day and open it at night. When the outside temperature is lower than 0℃, we should strengthen the heat preservation and cold protection measures, that is, cover the fruit pile with a layer of hay or kraft paper. When the outside temperature continues to decrease, plastic film should be added continuously, and soil can be cultivated around the fruit bed. During the whole storage period, the temperature in the fruit pile should be kept at-1 ~ 1℃.

2. Indoor storage method.

Indoor storage of Laiyang pears is a common method adopted by farmers in Laiyang. Laiyang pear stored by this method for 4 ~ 5 months, the peel is bright green and the pulp does not change color. Spray a lot of Bordeaux solution (1:3:200) before fruit harvesting. After the fruits are harvested, the fruits without diseases and insect pests and mechanical damage are selected, put into fruit baskets or fruit boxes, lined with polyethylene fresh-keeping bags with a thickness of 0.06-0.07 mm, added with lime according to the weight of the fruits at 5℃, wrapped with paper into several small bags, and placed in different positions of the fruit baskets and fruit boxes respectively. In the middle and late days of June 5438+ 10, when the outside temperature drops, the precooled Laiyang pear in a cool and ventilated place will be moved to the standby room. After entering the room, if the indoor temperature is lower than the outdoor temperature during the day and higher than the outdoor temperature at night, you should hang curtains on the doors and windows during the day and open all the door curtains at night, and make full use of the convection between the outdoor low temperature and the indoor temperature to reduce the indoor temperature. When the outside temperature is lower than 0℃, the window should be sealed, and when it is cold again, a cotton curtain should be hung on the door to keep the temperature. The suitable indoor temperature is 0℃. When storing, pay attention to always open the bag mouth for ventilation.

Step 3 refrigerate.

Pears can be refrigerated. Attention should be paid to the occurrence of chilling injury during cold storage. Yali pear, Xuehua pear and Changba pear cannot be directly refrigerated at 0℃ like apples. Otherwise, pears are black-hearted Generally, it will be put into storage above 10℃, and it will drop 1℃ every week, and then drop 1℃ every three days until it drops to about 0℃. It will take about 30 to 50 days.

Under cold storage conditions, it should be combined with modified atmosphere storage. Modified atmosphere storage can be carried out in modified atmosphere or small plastic film packaging. In particular, Yali pear, Laiyang pear, Changba pear and Xuehua pear will be poisoned under low concentration of carbon dioxide, and the symptoms are browning of pulp and stone. Therefore, it is necessary to adopt the storage method of carbon dioxide less than 1% or without carbon dioxide, which can be solved by adding quicklime in bags or tents or drying them frequently.

4. Modified atmosphere storage.

Modified atmosphere storage can delay the browning of pear pulp and core, delay the fading of green, and maintain the brittleness and flavor of pear. Modified atmosphere storage can be used not only in big tents and small plastic bags, but also in controlled atmosphere warehouses and controlled atmosphere machines. Modified atmosphere storage is similar to apple, except that the concentration of carbon dioxide must be strictly controlled. Control the concentration of carbon dioxide to a minimum.

4. Modified atmosphere preservation of Yali pear

Pears are packed in wooden cases or fruit boxes, lined with 0.06 mm thick polyethylene film bags, and the fruits are packed before being tied or sealed. In this way, the respiration of pears consumes oxygen in the bag, and at the same time, carbon dioxide increases, forming an environment with low oxygen and high carbon dioxide, thus inhibiting the respiration or other metabolic effects of fruits.

In the controlled atmosphere storage environment, the concentrations of oxygen and carbon dioxide are required to be within a proper range, and Yali pear is extremely sensitive to carbon dioxide. When the carbon dioxide concentration is lower than 65,438+0%, the black heart rate is 5% after 84 days of storage. With the increase of carbon dioxide concentration, the peel color gradually turns green and the fruit gradually turns from white to brown. When the concentration of carbon dioxide exceeds 2%, the black heart rate reaches 1000. The method is to put a proper amount of deoxidizer, activated carbon, adsorbent and hydrated lime in the bag to adsorb carbon dioxide.