Cut fruits and vegetables are also called semi-processed fruits and vegetables, which are in the category of net dishes. However, they require a higher technological content than ordinary net dishes. It is a comprehensive technical project that combines vegetable preservation and processing techniques. It refers to the steps of cleaning, refurbishing, peeling, and dividing the fresh fruit and vegetable raw materials. Finally, it is packed in plastic film bags or plastic trays and covered with plastic film for consumption by consumers or the food and beverage industry. product.
I. Anti-browning of cut fruits and vegetables In terms of fruits and vegetables, the main quality issue is browning, and browning causes poor appearance. Browning is not only a fruit and vegetable, but also a common discoloration phenomenon in the whole food. There are two types of browning reactions: one is oxidation of polyphenols catalyzed by oxidases and oxidation of ascorbic acid; the other is browning without enzymes.
Enzyme browning must have three conditions at the same time: polyphenols, polyphenol oxidase, and oxygen. These three conditions are indispensable. To prevent the occurrence of enzymatic browning, these conditions must be controlled.
It is more effective to prevent the enzymatic browning of fruits and vegetables from inhibiting the activity of polyphenols, and secondly, to prevent the contact between raw materials of fruits and vegetables and oxygen. The phenolase and all other enzymes can usually be deactivated by proper heating methods, so the raw material blanching method is often used to inactivate enzymes in fruit and vegetable production. Chemical treatment can also be used to inhibit the enzyme activity by adding a strong inhibitor of polyphenol oxidase. In addition, adjusting the pH can also achieve the effect of aprotinin. The optimum pH range for phenolase-induced oxidation is between 6 and 7, so reducing the pH of the medium inhibits the catalytic action of the enzyme. The final deoxygenation method can isolate fruits and vegetables from oxygen, and browning can be suppressed.
Non-enzymatic browning is much more complex, such as the Maillard reaction, ascorbic acid oxidation, pheophytin browning, and the like.
The main method to avoid the non-enzymatic browning of fruits and vegetables is to use color-keeping and anti-browning agents and low-temperature storage to control browning. Maillard reaction is the main reaction of non-enzymatic browning in food processing. Almost all foods have the possibility of this reaction. Traditionally, sulfites are generally used to inhibit browning, but the use of sulfites can have some adverse effects on the human body. The combination of citric acid and ascorbic acid can become a sulfite substitute.
Second, the color protection of cut fruits and vegetables In addition to enzymatic browning and non-enzymatic browning, there are mainly tannin substances and pigments will cause discoloration of fruits and vegetables.
Discoloration caused by tannins is one of the most common discoloration phenomena in the processing of fruits and vegetables.
The pigments contained in fruits and vegetables are classified as water-soluble and water-insoluble. General water-soluble pigments are broad-spectrum flavonoids, including anthocyanins and xanthin, and water-insoluble pigments are carotenoids and chlorophyll. These pigments are unstable in nature and can easily change color or fade.
1. When the anthocyanin changes from acidic to neutral, it will gradually shift from red to purple. Anthocyanin will turn grayish purple when it encounters iron and purple when it encounters tin.
2. Chrysin produces chalcones in alkaline conditions and appears yellow to brown. Flora is changed to green or blue in the presence of iron ions under acidic conditions. Floranthine also has the effect of chelating with aluminum, causing the color to darken. If aluminum equipment is used in the production of asparagus and onion products, this darkening may occur. 3. Carotenoid-induced discoloration. Beta-carotene is unstable in acidic conditions and relatively stable in weak alkaline conditions. It is orange to yellow at low concentrations and orange-red at high concentrations. Heavy metal ions, especially iron ions, can make them fade.
In the process of processing, packaging and distribution, an effective means to prevent changes is to eliminate the causes of discoloration and discoloration. The most effective method is the use of a natural pigment color-protection partner, the "Color Protection Agent F" type. It has a wide range of color protection and adaptability to the natural pigment in the food in the environment and the stability of different natural pigments. It is especially suitable for the protection of natural pigments under high temperature sterilization and shelf-life lighting conditions.
Third, several issues that must be noticed in the production of fruits and vegetables
1. Peeling: Mechanical, steam peeling and caustic peeling can severely damage the cell walls of fruits and vegetables, causing a large amount of cell juice to flow out, increasing the possibility of microbial growth and enzyme browning, thus impairing the quality of the product; Jian Ying The peeling agent takes this factor into account in the experimental design and increases the protection of the cell wall. However, the ideal method is to use a sharp cutting tool for manual peeling.
2. Blanching and Preservation: The objective of scalding is to inhibit its enzyme activity, soften fibrous tissue, remove spicy and astringent tastes, etc. for cooking and processing. Blanching temperature is generally 90-100 °C, product temperature should reach 70 °C or more. The blanching time is usually 1-5 minutes. After blanching, it should be quickly picked up. Immediately put it in a 0.1% solution of vegetable fresh fruit crisps and cool it for a few seconds, and let the product temperature drop to 10-12°C.
3. Brown color protection: The fruit and vegetable pieces are put into a 0.4% solution of fruit color protection anti-brown solution for boiling in 3-5 minutes or soaked in this aqueous solution for 2-3 hours. Remove and soak for 30 minutes in an aqueous solution of a natural pigment color-protecting partner at a concentration of 0.05%.
4. Preservation: Vegetable fresh-keeping agent has a strong bactericidal anti-corrosion ability. The solution is dissolved in cold water to a solution of about 0.2%, and the pH of the solution is adjusted to 5-5.5 with tartaric acid, citric acid or hydrochloric acid, and the fruits and vegetables are soaked for 1-2 hours. Drain the water and remove the water. More than 1% of water is usually removed by a centrifugal dehydrator.
5. Package storage: When preparing fresh fruits and vegetables, the most used packaging method is MAP. That is, a gas environment with a composition of 2%-5% of carbon dioxide, 2%-5% of oxygen, and the balance of nitrogen is obtained. The storage temperature must be ≤ 5°C, which can effectively inhibit the metabolism and microbial activity of fruits and vegetables to obtain sufficient shelf life and ensure food safety.
I. Anti-browning of cut fruits and vegetables In terms of fruits and vegetables, the main quality issue is browning, and browning causes poor appearance. Browning is not only a fruit and vegetable, but also a common discoloration phenomenon in the whole food. There are two types of browning reactions: one is oxidation of polyphenols catalyzed by oxidases and oxidation of ascorbic acid; the other is browning without enzymes.
Enzyme browning must have three conditions at the same time: polyphenols, polyphenol oxidase, and oxygen. These three conditions are indispensable. To prevent the occurrence of enzymatic browning, these conditions must be controlled.
It is more effective to prevent the enzymatic browning of fruits and vegetables from inhibiting the activity of polyphenols, and secondly, to prevent the contact between raw materials of fruits and vegetables and oxygen. The phenolase and all other enzymes can usually be deactivated by proper heating methods, so the raw material blanching method is often used to inactivate enzymes in fruit and vegetable production. Chemical treatment can also be used to inhibit the enzyme activity by adding a strong inhibitor of polyphenol oxidase. In addition, adjusting the pH can also achieve the effect of aprotinin. The optimum pH range for phenolase-induced oxidation is between 6 and 7, so reducing the pH of the medium inhibits the catalytic action of the enzyme. The final deoxygenation method can isolate fruits and vegetables from oxygen, and browning can be suppressed.
Non-enzymatic browning is much more complex, such as the Maillard reaction, ascorbic acid oxidation, pheophytin browning, and the like.
The main method to avoid the non-enzymatic browning of fruits and vegetables is to use color-keeping and anti-browning agents and low-temperature storage to control browning. Maillard reaction is the main reaction of non-enzymatic browning in food processing. Almost all foods have the possibility of this reaction. Traditionally, sulfites are generally used to inhibit browning, but the use of sulfites can have some adverse effects on the human body. The combination of citric acid and ascorbic acid can become a sulfite substitute.
Second, the color protection of cut fruits and vegetables In addition to enzymatic browning and non-enzymatic browning, there are mainly tannin substances and pigments will cause discoloration of fruits and vegetables.
Discoloration caused by tannins is one of the most common discoloration phenomena in the processing of fruits and vegetables.
The pigments contained in fruits and vegetables are classified as water-soluble and water-insoluble. General water-soluble pigments are broad-spectrum flavonoids, including anthocyanins and xanthin, and water-insoluble pigments are carotenoids and chlorophyll. These pigments are unstable in nature and can easily change color or fade.
1. When the anthocyanin changes from acidic to neutral, it will gradually shift from red to purple. Anthocyanin will turn grayish purple when it encounters iron and purple when it encounters tin.
2. Chrysin produces chalcones in alkaline conditions and appears yellow to brown. Flora is changed to green or blue in the presence of iron ions under acidic conditions. Floranthine also has the effect of chelating with aluminum, causing the color to darken. If aluminum equipment is used in the production of asparagus and onion products, this darkening may occur. 3. Carotenoid-induced discoloration. Beta-carotene is unstable in acidic conditions and relatively stable in weak alkaline conditions. It is orange to yellow at low concentrations and orange-red at high concentrations. Heavy metal ions, especially iron ions, can make them fade.
In the process of processing, packaging and distribution, an effective means to prevent changes is to eliminate the causes of discoloration and discoloration. The most effective method is the use of a natural pigment color-protection partner, the "Color Protection Agent F" type. It has a wide range of color protection and adaptability to the natural pigment in the food in the environment and the stability of different natural pigments. It is especially suitable for the protection of natural pigments under high temperature sterilization and shelf-life lighting conditions.
Third, several issues that must be noticed in the production of fruits and vegetables
1. Peeling: Mechanical, steam peeling and caustic peeling can severely damage the cell walls of fruits and vegetables, causing a large amount of cell juice to flow out, increasing the possibility of microbial growth and enzyme browning, thus impairing the quality of the product; Jian Ying The peeling agent takes this factor into account in the experimental design and increases the protection of the cell wall. However, the ideal method is to use a sharp cutting tool for manual peeling.
2. Blanching and Preservation: The objective of scalding is to inhibit its enzyme activity, soften fibrous tissue, remove spicy and astringent tastes, etc. for cooking and processing. Blanching temperature is generally 90-100 °C, product temperature should reach 70 °C or more. The blanching time is usually 1-5 minutes. After blanching, it should be quickly picked up. Immediately put it in a 0.1% solution of vegetable fresh fruit crisps and cool it for a few seconds, and let the product temperature drop to 10-12°C.
3. Brown color protection: The fruit and vegetable pieces are put into a 0.4% solution of fruit color protection anti-brown solution for boiling in 3-5 minutes or soaked in this aqueous solution for 2-3 hours. Remove and soak for 30 minutes in an aqueous solution of a natural pigment color-protecting partner at a concentration of 0.05%.
4. Preservation: Vegetable fresh-keeping agent has a strong bactericidal anti-corrosion ability. The solution is dissolved in cold water to a solution of about 0.2%, and the pH of the solution is adjusted to 5-5.5 with tartaric acid, citric acid or hydrochloric acid, and the fruits and vegetables are soaked for 1-2 hours. Drain the water and remove the water. More than 1% of water is usually removed by a centrifugal dehydrator.
5. Package storage: When preparing fresh fruits and vegetables, the most used packaging method is MAP. That is, a gas environment with a composition of 2%-5% of carbon dioxide, 2%-5% of oxygen, and the balance of nitrogen is obtained. The storage temperature must be ≤ 5°C, which can effectively inhibit the metabolism and microbial activity of fruits and vegetables to obtain sufficient shelf life and ensure food safety.
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