Common pretreatment methods for preserved fruit production? . What problems should be paid attention to in temperature management in preserved fruit production? thank you

1. Slicing: Cut the fully mature fresh apricots in half, remove the core, put them in wooden pallet, put the apricot bowl up, and then send them to the sulfur fumigation room for sulfur fumigation. The drying boards are all made of wood, with short edges around them, and the bottom is put together with wooden boards, leaving no gaps. There are two cross bars at the bottom of the tray, which is convenient for ventilation when stacked. Wooden pallet is 90 ~ 100 cm in length and 60 ~ 80 cm in width.

2. Sulphur fumigation: when the sulfur is ignited, the indoor SO2 concentration is kept at 2-3%, and the sulfur continues to burn and does not go out, and it is fumigated for 12 hours until the fruiting body is transparent and seedless. The sulfur fumigation room can be built of masonry and cement and treated by trucks, each truck is equipped with 20-25 drying trays. During sulfur fumigation, the indoor humidity is kept at 40 ~ 50℃. Fresh apricots can play an important role after absorbing a certain amount of SO2. In addition, it can promote drying, prevent products from becoming sour and deteriorating, and contribute to future preservation. A ton of cutting materials needs about 20 ~ 40 kilograms of sulfur.

Sulfur should be of good quality, pure and easy to burn, and its impurity content should not exceed 1%, in which arsenic (arsenic) content is 0.0 15%. There is no oil. When in use, 5% potassium nitrate or sodium nitrate is added to sulfur powder to make particles to help combustion.

3. Sun drying: move the sulfur-smoked apricot bowl to the threshing floor and expose it in the sun for 1 ~ 2 days. When dried to 570%, the dried plates are stacked and covered together, and they are allowed to air-dry in the shade for about 10 days until the water content is 15% (for example, direct drying), and then the dried apricots are stored as processing raw materials. When drying, don't pour the juice out of the apricot bowl, so that the fruit can absorb the sugar in the juice and become fuller.

4. Processing method: soak dried apricots in water for 2-4 hours, remove impurities on the surface of dried apricots when drying, and soak dried apricots to absorb water. Take it out and put it on a tile tray with the apricot bowl facing up, and send it to sulfur fumigation. Then air-dried until the water content is about 20%, the product is more transparent. The content of SO2 in the finished product should not exceed 2000ppm(0.2%).

Production method (foreign candied pears) 1. Raw material requirements: eggplant pear, stored in the warehouse for a week, is completely mature, or filled with ethylene gas to ripen until it is mature enough to pull off the pear handle by hand.

2. After peeling and coring, cut it into two halves, put it on a drying tray for 48-72 hours, dry it for 2-3 days, then stack the drying trays and air dry them, and the water content is 13- 15%.

3. Soak the dried pears in 2% sugar solution at 40℃ for 6 hours, then put them on a tray, fumigate them with sulfur, and dry them until the water content is about 20%. [ 1]?

Take sugar-free preserved fruit as an example: the sugar content of traditional preserved fruit is as high as 50%, and the production process is complicated, or the workshop production can not guarantee the hygienic quality; Or the equipment investment is too large, increasing the cost. More importantly, with the development of society and the continuous improvement of people's living standards, high-sugar foods are becoming more and more unpopular, especially for patients with hypertension, heart disease, diabetes, obesity and dental caries, who can hardly eat sugar. Many fruits, such as hawthorn, are most beneficial to these people, but the traditional hawthorn products are almost untouchable, and candied sugar (sugarcane) is not developed, which has the lowest cost and the simplest technology.

Production method:

1. Select fresh and complete fruits (varieties that can be dried in the sun) to remove calyx, pedicel, pit or barrel pit (such as hawthorn), cut them in half, slice them, and dry them in the air (different processing methods such as drying in the shade, drying in the sun, oven drying, etc.). ) Keep the original flavor and proper size and shape of the fruit as much as possible. The dried product is stored for later use.

2. Prepare impregnation solution and auxiliary materials. The impregnating solution is mainly composed of sweetener and a small amount of potassium sorbate, and the auxiliary materials are composed of compound thickener, citric acid or malic acid, sweetener and potassium sorbate.

3. Soak the dried fruit in soaking solution for 2-3 hours. After the dried fruit is fully absorbed, take it out, drain the water and dry it properly.

4. Boil the soaked dried fruit in the auxiliary materials until it boils, take it out and drain it. Stainless steel or enamel products of boiling pot can also be heated by steam or open flame.

5. Spread the fished dried fruit in a single layer and put it into the drying room, keep it at 60-70℃ during drying, and dry it at constant temperature for about 1 hour, and turn it over 1-2 times.

6. Dried preserved fruit has moderate hardness, water content of about 20-25%, bright appearance and moderate sweetness.

process flow

Pay attention to picking, the fruit should be mature enough to be separated from the pulp, and immediately pick it and send it to the factory for processing. Fresh apricots are pitted and divided into two petals, and boiled with white sugar solution, or the sugar soaking solution is pumped out of the fruit with a vacuum compressor.

Different from the traditional production method of preserved fruit, the new technology can produce "fresh-flavored preserved fruit" and "low-sugar preserved fruit". In addition, the technology of making preserved fruit abroad is also different from the traditional technology in China. 1. Comparison between traditional preserved fruit production methods and new technology Most traditional preserved fruit products are "heavy sugar" products, with the appearance of candied fruit, the sugar content is above 70 ~ 75%, and the surface of preserved fruit is sticky.

Process flow (traditional preserved fruit) raw material selection → fresh fruit processing pretreatment (including peeling, coring, dicing and sulfur fumigation, etc.). ) → Boiling in sugar solution (once or many times) → Soaking in sugar solution → Drying (sun drying or drying) → Finished product.

Physical and chemical analysis and comparison of heavy sugar preserved apricot, light sugar preserved apricot, fresh fragrant preserved apricot and American preserved apricot;

Physical and chemical indicators Product variety Total sugar (%) Reducing sugar (%) SO2 (%) Moisture (%) Acidity (%) (calculated by malic acid)

Dried apricot with heavy sugar 70.2 6 1.00.096 20.00.56

Low-sugar preserved apricot 64.055.00.1119.20.88

Fresh preserved apricots 60.5 39.2 0.05 24.0 0.62

American preserved apricot 55.155.10.12210.50.43

As can be seen from the above table, the total sugar content of American preserved apricots is completely equal to the reducing sugar content. Its reducing sugar (including fructose, glucose and other monosaccharides) is not produced by hydrolysis and transformation of sucrose, but comes from the sugar in the juice of fresh apricot itself, which is different from the traditional preserved fruit production with white sugar as raw material in China. At the same time, the sweetness of American preserved apricots is low, the original fruit is thick, sweet and sour, and the taste is similar to that of dried fruits. Its raw materials are fresh dates and apricots with good varieties, high maturity and rich sugar content. This product has the characteristics of preserved fruit: orange color, soft and transparent fruiting body, etc.

2. Delicious candied fruit Delicious candied fruit is also called "raw" candied fruit, and the traditional unheated candied fruit cooking method is replaced by vacuum sugar infiltration process.

The basic principle of vacuum sugar infiltration is that there is air in the intercellular space of fruit, which hinders the penetration of sugar solution. The gas in the pulp is exhausted under the action of vacuum. After the vacuum is released, the sugar solution can enter the space originally occupied by air through the external atmospheric pressure, so as to achieve the transparency of the fruit and complete the requirement of sugar infiltration. When cooking preserved fruit, heat to let the air out. When cooking, the steam between fruit cells condenses to form a vacuum, and the sugar solution is infiltrated into the fruit by external atmospheric pressure (called eating sugar).

Process flow (preserved peach): raw material selection → cleaning → cutting → coring → vacuum control of →0.25%NaHSO3 solution for 40 minutes (vacuum degree is 700 mm Hg) → slow degassing for 20 minutes → stock solution soaking 12 hours → first stage vacuum sugar solution soaking 12 hours →

Production method 1. Selection of raw materials: choose peaches with maturity of 7-8 as raw materials.

2. Preparation of sugar solution: The content of invert sugar in sugar solution should be about 50% to prevent fresh preserved fruit from returning to sand and crystallizing.

3. Packaging: Because the fresh preserved fruit is not heated during processing, the enzyme activity is not destroyed, and the SO2 content is low, which leads to serious discoloration during storage. The solution is to need vacuum, airtight and deoxygenated packaging conditions.

There is a question of 1 The packing conditions are very strict. If tinplate packaging is used, the cost is high and it is difficult to popularize and apply.

2. Because of the low sugar content, the fresh and fragrant preserved fruit consumes more raw materials, which leads to an increase in cost. For example, raw materials (fresh peaches) are about 400 kilograms per 100 kilograms of ripe peaches, while raw preserves consume more than 500 kilograms.

3. Light sugar candied fruit Light sugar candied fruit is based on the traditional production technology, which changes "heavy sugar" into "light sugar" by taking measures to reduce the sugar content of candied fruit, such as light sugar preserved apricot, light sugar preserved peach and light sugar preserved pear.

In the cooking process, light candied fruit is cooked with low concentration sugar solution, and the three-time cooking method is changed into the secondary cooking method, and the "sugar frying" process is cancelled (which means that the dried candied fruit is heated and fried again with 30-32 Baume concentrated sugar solution, and then dried again to obtain the finished product). The technological processes of heavy sugar preserved apricots and light sugar preserved apricots were compared:

Process flow (preserved apricots with heavy sugar) → Cut apricots in half → Core removal → Sulphur impregnation → First boiling (sugar concentration 20%)→ Second boiling (sugar concentration 40%)→ Out of the can → Out of the drawer → Drying → Third boiling (sugar concentration 60%)→ Setting → Drying → Finished product.

Process flow (preserved apricot with light sugar) → Cut apricot into two halves → Core removal → Sulfur soaking → Primary boiling (sugar concentration is 20-25%) → Secondary boiling (sugar solution concentration is 45%)→ Discharge → Placing drawer → Drying → Re-drying → Finished product.

Another method to reduce the sweetness of preserved fruit is to change the traditional method of making preserved fruit with only white sugar and replace 40 ~ 50% sucrose with starch syrup. The preserved fruit cooked in this way is still full of sugar, but it tastes sweet.

Starch syrup is a mixture of glucose, oligosaccharides and dextrin. Its nature is that it can't crystallize, which can prevent sucrose from crystallizing. Replacing part of sugar with starch syrup can simplify the production process, and there is no need to transform the sugar solution during cooking, and the effect is very good. Starch syrup has low sweetness, which can dilute the sweetness of sucrose and make preserved fruit sweet and sour. In addition, starch syrup does not contain fructose, and its hygroscopicity is lower than that of invert sugar, which makes the preserved fruit better. For example, a preserved fruit factory in Shanxi uses glucose instead of white sugar to produce light sugar preserved apples, and the products are welcomed by foreign businessmen such as Japan. In the past, preserved apples were only sweet, lacking the fruit flavor and taste that apples should have.

Four. Vacuum cooking technology of preserved fruit At present, vacuum cooking technology has been used to produce light sugar preserved fruit in China.

The technological process is as follows: fresh fruit raw materials → processing (including peeling, coring, dicing, sulfur soaking, etc. ) → preparing sugar solution → vacuum cooking → soaking 12 hours → drying → finished product.

When cooking in vacuum, the sugar solution will boil at 50 ~ 60℃ when the concentration is 40 ~ 50% and the vacuum degree is 620 ~ 660 mm Hg. Because the preserved fruit is cooked at low temperature, it can maintain the fragrance of the original fruit, lose less vitamin C, and evaporate water, so the sugar solution can be recycled. The cooking time is about 20 minutes. When the preserved fruit is cooked until the fruit is transparent, it can be taken out of the pot and soaked in sugar solution 12 ~ 24 hours. At the same time, adding about 40% starch syrup to the prepared sugar solution can not only prevent the preserved fruit from returning to sand and crystallization, but also reduce the sweetness, so that the preserved fruit has the characteristics of low sweetness and strong fruit flavor.

Verb (abbreviation of verb) foreign candied fruit In recent years, some countries such as the United States and Australia have adopted mechanized and continuous production lines in the production of candied fruit, which is characterized by high mechanization and large output, with a daily output of more than dozens of tons. However, some small and medium-sized enterprises adopt manual operation and semi-mechanized production methods.

Raw materials require that preserved fruits are made of foreign raw materials, and there are particularly strict requirements for varieties. For example, there are four requirements for raw materials for making preserved apricots:

1. High maturity. Apricots should be more than 90% ripe (a pit can collapse when pressed by hand), and soft but not hard, which is just the opposite of the requirement for raw materials in China traditional technology.

2. Raw materials need less water, that is, "meat tires" rather than "water tires".

3. Nucleated varieties.

4. More sugar.

Preserved apricots, peaches, plums and pears produced abroad are not very sweet, and belong to the type of light sugar preserves in China. Its technological characteristics are that it does not need to be cooked (thoroughly) in a pot or vacuumized, and it is mainly smoked with sulfur, so as to achieve the purpose of transparent preservation of fruits.

Process flow (preserved apricots abroad) Apricot → Rinse → Cut and core → Plate → Sulfur fumigation → Sun drying, air drying → Soaking → Sulfur fumigation → Sun drying → Finished product.

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