With the accelerated pace of life and the strengthening of environmental awareness and health awareness, micro-processing of fruits and vegetables as a new, nutritious and convenient new food has become the development trend of fruit and vegetable processing and production. Minimally processed fruits and vegetables, also known as fresh-cut fruits, cut fruits and vegetables, semi-processed fruits and vegetables, conditioning fruits and vegetables, and minimal processing of fruits and vegetables, means changing the physical shape of vegetables and fruits, but still maintaining A fresh fruit or vegetable or fruit and vegetable blend. The production process generally needs to be cleaned, classified, trimmed, cut (or not divided), washed, dried, packaged (or coarse pre-packaged), stored, distributed, etc., for consumers to directly consume or use in the catering industry. From the concept of micro-processing fruits and vegetables, it can be seen that the most fundamental problem of micro-processing fruits and vegetables is the quality of micro-processed fruits and vegetables. Therefore, the research and development of fruit and vegetable micro-processing should focus on how to control the quality change of micro-processed fruits and vegetables after cutting, maintain its quality, and prolong the shelf-life and storage period of micro-processed fruits and vegetables. Canned Orange Segments,Canned Pineapple in Light Syrup,Canned Yellow Peach Halves WEIFANG ARTISAN FOODS CO.,LTD. , http://www.artisanfoods-wf.com
Micro-processed fruits and vegetables are characterized by freshness, convenience, nutrition and pollution-free. Consumers who purchase such products do not need further treatment and can cook or eat directly. These characteristics meet the needs of people in pursuit of nature, nutrition, and fast pace of life, which has led to rapid growth in double digits every year in recent years. In the next five years, micro-processed products will continue to grow at an annual rate of 10-15%. Since the 1990s, China's semi-processed vegetable industry is gradually developing, especially the establishment of vegetable distribution centers throughout the country in recent years, providing favorable conditions for the development of micro-processed vegetables. 
Micro-processing consequences of vegetable quality and physiological changes
After the fruits and vegetables are processed, washed and cut, the integrity of the tissue structure, the speed and extent of nutrient loss, the intensity and direction of metabolism, the microbial infestation and the deterioration of the product are significant before the cutting. Changes have created some new problems.
â—† loss of nutrients, decreased sensory quality
There are several reasons for the loss of nutrients and the loss of sensory quality after micro-machining. First, the segmentation causes the regional distribution of enzymes and substrates in the tissues of fruits and vegetables to be destroyed, and various biochemical reactions are accelerated, especially for hydrolysis and oxidation. The change is most obvious, especially in the presence of aerobics, resulting in changes in the original color, aroma, taste and texture of the product, and the nutritional value is reduced. Second, the micro-processed fruit and vegetable production is caused by cleaning and cutting. Mechanical injuries and wounds can damage the cells of fruits and vegetables, lead to loss of juice, and accelerate the loss of nutrients in the damaged tissues, especially water-soluble and easily oxidizable components. Third, the division makes the surface area of ​​fruits and vegetables greatly increase, and the same conditions. Under the uncut fruit and vegetable, the water loss is faster, which not only directly reduces the weight of the micro-processed fruits and vegetables, but also causes direct economic loss, and the water loss leads to wilting and accelerates the aging of the product.
â—†Injury and physiological and biochemical intensification
After the fresh fruits and vegetables are cut, the tissue produces mechanical injuries, which not only affect the injured cells themselves, but also generate injury signals and quickly transmit them to neighboring cells in a short period of time (such as a few seconds) to induce intricate physiological and biochemical reactions and spread. , affecting cells away from the injury site. The injury signal formed by the segmentation may be purely physical (such as hydrostatic waves or pressure waves), biochemical (systemic, oligosaccharide, SA, ethylene and other signaling molecules induce specific synthesis of the wound response substance), or physical The result of a combination with a living being (such as a bioelectromotive force wave or current). However, it is also believed that the injury signal is not specifically formed by the injured tissue, but is a by-product of the initial injury response (such as the pectin fragment degraded by the cell wall) that damages the cell. It is worth noting that mechanical damage to fresh fruits and vegetables not only causes the above-mentioned local transient effects, but also causes overall long-term physiological effects.
â—†Injury of ethylene and breathing
After the fruit and vegetable are cut, the ethylene release rate rises rapidly, promoting tissue maturation, softening and aging. The ethylene fumes caused by the dicing are only a few minutes in some materials, but usually take several hours in most samples and reach the peak of ethylene release within 6 to 12 hours. Although the injury-induced ethylene synthesis pathway is identical to the normal and mature ethylene synthesis pathways, the ethylene produced by the injury-induced ethylene and maturation transitions is relatively independent and inconsistent in time.
The most obvious manifestation and characteristic of excision leading to increased metabolism of fruits and vegetables is respiratory enhancement. Respiratory enhancement increases the material consumption of micro-processed fruit and vegetable products, accelerates the loss of nutrients, reduces the sensory properties of products, and shortens the shelf life and shelf life of micro-processed fruits and vegetables. The amount of increased breathing is closely related to the type and variety of fruits and vegetables, the stage of development, the size of the cut, and the smoothness of the wound. Micro-processing of juice in fruit and vegetable tissues may block the passage of gas, causing the rate of gas diffusion in tissue cells to decrease, causing anaerobic respiration of internal tissues, leading to the accumulation of ethanol and acetaldehyde, which may cause micro-co-production with other volatile substances. The production of odors in processed products.
â—†Injury healing and secondary metabolism
After the fruit and vegetable tissue is cut, cork or / and lignin are produced and deposited in the cell wall of the injury site, and the response of different fruits and vegetables is different. When the peel of tomato is injured, the surface cells of the citrus are thawed, and the injured part of the citrus peel is lignified, especially on carrots, potatoes and other fruits and vegetables. The formation of cell tethering and callus pericarp is affected by the condition of the tissue itself and the surrounding environmental conditions (such as temperature, humidity, gas composition). The wound healing of the tissue can change the appearance of micro-processed products, affect commodity traits and Reduce the value of food.
Fruit and vegetable tissues can induce the synthesis of a series of secondary metabolites such as phenylpropanoids, polyketides, flavonoids, mushrooms, alkaloids, tannins, mustard oil, long-chain fatty acids and alcohols. These substances are mainly concentrated in the wound and its surrounding tissues, participating in the wound healing response and resisting the invasion of pests and diseases. Not only different types of fruits and vegetables, even different varieties of the same fruit and vegetable, there are differences in the types and quantities of sub-biomass, and the same species with different origins, the sub-biomass of injury-induced differences.
In summary, the damage signal generated by micro-processing of fruit and vegetable production will have a significant impact on the metabolism of breath, phenol and ethylene, and these metabolisms are related to each other in the metabolic system of fruits and vegetables.
â—†Microbial infection
Micro-processed fruit and vegetable processing and circulation are usually in a low acidity and high moisture content environment, and the wound caused by the cutting is not only convenient for microbial infestation, but also provides sufficient water and nutrition for microbial infection. Under such conditions, the cutting process itself also increases the chance of microbes contaminating fruits and vegetables, and thus such products are highly susceptible to contamination by external microorganisms. Rapidly multiplying microorganisms can cause product safety problems while shortening the shelf life of micro-processed fruits and vegetables. Therefore, how to control the influence of microorganisms in micro-processed fruit and vegetable production and after production is one of the key issues that need to be taken seriously.
Research Status of Quality Maintenance of Micro-Processed Fruits and Vegetables at Home and Abroad
â—†Inhibition of browning and selection of preservatives
Browning is one of the main quality problems of micro-processed fruits and vegetables. Browning can affect the color of the product and seriously affect the appearance quality. Under normal circumstances, the browning reaction of fruits and vegetables is enzymatic browning and non-enzymatic browning. Non-enzymatic browning is more complicated than enzymatic browning. Enzymatic browning is polyphenols catalyzed by oxidase. Oxidation of substances and browning under the oxidation of ascorbic acid must occur with polyphenols, polyphenol oxidase and oxygen. To prevent the occurrence of enzymatic browning, these three factors must be properly controlled. An effective method is to inhibit the activity of polyphenol oxidase, such as low temperature or blanching treatment, pH adjustment, use of a chelating agent (such as citric acid, EDTA), and the like.
â—†Storage temperature
Low temperature treatment can effectively slow down the activities of enzymes and microorganisms, inhibit the respiration rate of fruits and vegetables, reduce the speed of various biochemical reactions, delay aging and inhibit browning. The temperature coefficient Q10 of enzymatic reaction is 2-3, and the temperature drops by 10 °C. Physiological and biochemical reactions have dropped to 1/2-1/3. Therefore, low temperature is the key condition to ensure the quality of micro-processed fruits and vegetables. Most studies suggest that micro-processed fruits and vegetables are more suitable for storage at 0-5 °C. In order to ensure the quality of micro-processed fruits and vegetables, the temperature control in the processing site and the cold chain in the storage process are important factors for the success or failure of preservation.
â—† sterilization treatment
Micro-processed fruits and vegetables are susceptible to microbial infestation due to man-made mechanical damage. Therefore, micro-processed fruits and vegetables usually need to be sterilized before packaging. Common cold sterilization methods include ultraviolet sterilization, ultrasonic sterilization, ozone sterilization and radiation sterilization. At present, the most common method is to sterilize the aqueous solution containing chlorine and hypochlorous acid for a certain period of time before packaging. The application of stable chlorine dioxide bactericide on micro-processed mango showed that ClO2 had a significant bactericidal effect on mango. Within a certain concentration range, the bactericidal effect increased with the increase of ClO2 bactericide concentration. With the prolonged storage period, the antibacterial effect of high concentration of ClO2 sterilization decreased the fastest. The low temperature storage helps to maintain and enhance the bactericidal effect of ClO2. At the same time, it is found that ClO2 has better anti-browning effect, and its The browning prevention effect increases as the concentration increases.
â—† Cutting size and cutting method
The volumetric size of micro-processed fruits and vegetables also has a certain influence on the quality. The smaller the volume of cut fruits and vegetables, the larger the segmentation area. The faster the surface water transpiration is, the more serious the injury is. The phenolic substances flowing out of the cut surface are easily oxidized. Browning occurs, which affects the appearance quality and is not conducive to the preservation of the product. The bamboo shoots were cut into pieces of different sizes and stored at 4 ° C. The small-sized bamboo shoots were found to have a higher water loss rate than the bulky bamboo shoots. The comprehensive score of the quality was always lower than the latter, and the storage stability was poor. .
The difference in the cutting method will also cause the difference in the size of the wounded fruit and the amount of nutrient loss, which will affect the preservation effect of the cut fruit. The study of cutting pineapples by different cutting methods showed that the storability and quality of the cut pineapple were better than the cross cut.
â—†Edible coating
The coating film can reduce the water loss of micro-processed fruits and vegetables, prevent contact with oxygen, reduce the chance of microbial infection, prevent the volatile components from volatilizing, inhibit the breathing, delay the formation of ethylene, reduce the metabolic rate, and thus delay the aging and spoilage of micro-processed fruits and vegetables. To maintain the quality and stability of the product. The membrane itself can be used as an antibacterial agent and an antioxidant carrier. Therefore, a single coating agent or several materials can be selected for compounding, and an antibacterial agent, a preservative, and the like are added to the coating liquid to contact the enzyme with oxygen. The carrageenan, chitosan and sodium alginate were selected as the main raw materials of the coating film. The micro-processed potato was coated and treated at low temperature, and the sensory color, browning degree and PPO activity were measured respectively. The results showed that seaweed The sodium coating film can effectively inhibit potato browning and is superior to other coating materials.
â—†Air conditioning packaging
As a means of pollution-free preservation, Modified Atmosphere Preservation (MAP) has attracted worldwide attention. The air-conditioning packaging of fruits and vegetables after pre-processing can greatly extend the shelf life of fruits and vegetables. MAP combined with refrigeration is beneficial to maintain the quality of micro-processed fruits and vegetables, prolong storage period, create low O2 and high CO2 environment during storage, reduce breathing, inhibit ethylene production, delay the aging of micro-processed fruits and vegetables, and prolong storage time. ADA and other studies have found that the gas composition of stored micro-processed apples is adjusted to (2% O2, 4% ~ 12% CO2), with better color, higher fructose content and soluble solid content ratio than storage in air. The quality of micro-processed apples is high. By studying the microbial and quality changes of micro-machined tender spinach leaves under modified atmosphere packaging conditions, the results showed that the addition of overpressure oxygen in the package reduced microbial growth, reduced the damage to the tissue, and maintained the quality of the micro-processed spinach leaves.
Outlook
As an important form of modern fruit and vegetable circulation, China's micro-processing fruit and vegetable industry has entered a stage of rapid development. The main purpose of micro-processing of fruits and vegetables is to facilitate consumption. The main problem is that it is more susceptible to deterioration, and the key technology is preservation measures. Advanced techniques and methods are used to control the poor quality of micro-processed fruit and vegetable products during processing, in order to better preserve their nutrients, freshness and flavor. With the development of the food industry, micro-processed fruits and vegetables will be welcomed by the majority of consumers in China due to their convenience, hygiene and freshness, and have a broad market.