1. Selection of raw materials
The quality and maturity of fruits and vegetables are the key factors for the quality of fruit and vegetable products.
1.1 Relationship between varieties and processing
The quality of fruit and vegetable products is closely related to the processing suitability of raw material varieties. Some varieties of fruits and vegetables do not have good fresh eating characteristics, but have good processing characteristics. For example, Ruidan, Ruilin, Shanglin and other apple varieties are suitable for apple juice production; Ruiliana, Ruila, Ruixing and other varieties are suitable for the production of high acid apple juice; Xiaohuang is an apple variety for juice making and wine making; Kukaimai, Kufeigan and Meina are high tannin wine making apple varieties.
1.2 Relationship between maturity and processing.
The maturity of fruits and vegetables is one of the important indicators of raw material quality and processing suitability. The harvest maturity and harvest requirements of various fruits and vegetables shall be determined by their variety characteristics and processing requirements. For example, green peas should be harvested in the milk ripening period, and the cans made of green peas are sweet, tender, and do not mix with soup; The mushroom fruiting body should be harvested at about 1.8~4.0cm for canning; When making processed grapes, they should be harvested in the physiological maturity period.
1.3 Relationship between freshness and processing
The freshness of raw materials used in the processing is the primary choice for fruit and vegetable processing. Fruit and vegetable decay will affect the quality of products and increase production costs; The time from harvesting to processing of fruits and vegetables should be as short as possible to ensure the freshness and integrity of raw materials; After the fruits and vegetables are transported to the factory, they should be processed in time; If it is too late for processing, it should be stored under appropriate conditions to ensure freshness and integrity and reduce decay loss.
2. Pretreatment
The treatment of fruits and vegetables before processing has a great impact on the production of their products, including sorting, grading, cleaning, peeling, cutting, trimming, blanching, hardening, evacuation and other processes. Generally, fruits and vegetables need to be peeled before processing, and only the inedible parts or parts that affect the quality of the products need to be removed during peeling; If the raw materials of fruits and vegetables are rough, hard and have bad flavor, peel them (such as peaches, apricots, pears, apples and plums containing cellulose, protopectin and cutin) to improve the quality; The peel contains bad flavor substances, which have a certain impact on the flavor of the product (such as persimmon, potato, lotus root, citrus containing bitter glycosides, pineapple, banana, Chinese chestnut, kiwi, etc. are not edible, and only in certain specific processing processes do not need to peel). There are many peeling technologies for fruits and vegetables. In addition to traditional methods such as manual, mechanical, alkali, thermal and enzymatic peeling, there are also high-tech methods.
2.1 Frozen peeling
The temperature setting range of the freezing peeling device is - 23~28 ℃. The fruits and vegetables leave after contacting the surface of the freezing device for a moment. The skin is peeled when it is frozen on the freezing device. This method can be used for peeling peaches, apricots, tomatoes, etc. The freezing peeling effect is good but the cost is high.
2.2 Vacuum peeling
In order to facilitate the separation of fruit skin and flesh, the fruits and vegetables are preheated to a certain temperature and put into the vacuum chamber. The temperature of the tissue liquid under the fruit and vegetable skin rises rapidly and boils, prompting the separation of the skin and flesh of fruits and vegetables. Then the fruits and vegetables coming out of the vacuum chamber can be peeled by stirring or washing. This method is applicable to mature tomatoes, peaches, onions, etc.
