Frozen Vegetables Recommend Products
Frozen Vegetables Detail Introduction
What is frozen vegetables?
Frozen vegetables are frozen food made by processing fresh vegetables such as peppers, tomatoes, beans, and cucumbers and then freezing them in small packages at the lowest possible temperature and as quickly as possible.
How are frozen vegetables consumed?
Frozen vegetables are fresh vegetables that are processed and then quickly frozen for storage.
Improper consumption of frozen vegetables will not only destroy their nutrition but also damage the color, aroma, and taste. The correct way to eat is to buy now, not to store at home, not to mention the outdoor conditions. Secondly, frozen vegetables before freezing have been cleaned, washed, rinsed before bagging, so no additional washing, as long as thawing can be.
What is the process of frozen vegetables?
Fresh vegetables after processing, using modern advanced methods for quick-freezing, can maintain the original color, flavor, and various nutrients of vegetables to a greater extent and are easy to eat. At present, the quick-frozen vegetable industry has become an important part of the frozen food industry in developed countries. China is a large producer of frozen vegetables, frozen vegetables mainly sweet corn, peas, broccoli, beans, asparagus, green beans, beans, Dutch beans, potatoes, carrots and mushrooms, more than 20 varieties, the vast majority of products sold to Europe and the United States and Japan, the annual foreign exchange earnings of more than 200 million U.S. dollars.
The general process flow of quick-frozen vegetables is:
Raw material---Grading---Cooling---Washing---Pre-treatment---Scalding and bleaching---Cooling, draining---Quick freeze---Packaging---Freezing and storage
The quality of raw materials is the most important condition related to the quality of frozen vegetable products. The type and quality of vegetables are directly affecting the quality of frozen vegetable products. In addition, the picking period, picking method, climatic conditions, pests, pesticide pollution, and the best maturity are important factors affecting the initial quality. Generally speaking, vegetables containing more water and fiber are weak against freezing. The sensitivity to freezing speed is strong - some; and vegetables containing less water and more starch are strong in freezing. That is, the sensitivity to freezing speed is weak. Vegetables suitable for quick-freezing species are green peas, beans (beans, lentils), fava beans, beans, green beans, Dutch beans, cauliflower, spinach, mushrooms, taro, potatoes, carrots, asparagus, garlic, green pepper, stem cabbage, lotus root, sweet potatoes, etc.
Select raw materials, should observe its size, shape, appearance, choose a bright color, strong smell, with good organizational characteristics and uniformity of appearance of vegetable varieties, such as peas to choose fresh and sweet taste, vegetable beans to choose tender green without tendons, asparagus to choose the green top scales.
Vegetables are harvested for the respiration and metabolism of living organisms. To maximize the freshness and original quality of vegetable raw materials, we must use artificial methods to help release field heat within the shortest possible time after harvesting them so that respiration and evaporation are reduced to the lowest level that can maintain normal metabolism. Vegetable cooling methods are air cooling, water cooling, vacuum cooling.
Vegetable surfaces stained with mud, dust, and pesticides, especially the surface of root vegetables and leafy vegetables with more soil on the roots, should pay attention to the washing. Quick-frozen vegetables in the consumption of general no longer wash, direct heating cooking.
Washing clean vegetables to remove the skin, seeds, and other inedible parts, and then according to the different requirements of products, cut into various sizes and shapes. Raw materials can not directly contact copper or iron containers in the pre-treatment process. Otherwise, the product can easily discolor and change the taste, so the processing should use stainless steel appliances.
Quick-freezing will weaken the brittleness of fruits and vegetables. Raw materials can be immersed in 0.5% to 1% of calcium carbonate (or calcium chloride) solution, soak 10 ~ 20min to increase its hardness and brittleness. Some vegetables such as cauliflower, broccoli, beans, beans, etc., to be soaked in 2% ~ 3% brine for 15 ~ 30min to drive out the internal insects, soaking should be rinsed again. The mass ratio of brine to raw material is not less than 2: 1.
5.Scalding and bleaching
(1)the role of scalding and bleaching vegetables by scalding and bleaching treatment play the following aspects of the role.
First, destroy the enzyme activity, stabilize the color, improve the flavor and organization. Most fresh, non-blanching frozen vegetables in the -25 ~ -18 ° C conventional freezing temperature range can only be a short storage period. This is because the enzymes in vegetables at low temperatures still have a certain activity, thus causing changes in frozen vegetables' color, flavor, texture, and nutritional quality. These undesirable changes can be improved by heating the vegetables before freezing so that the enzymes lose activity. At present, most vegetables are scalding and bleaching process, only a few vegetables before freezing without heating treatment, such as onions, green tomato peppers, cucumbers, etc.
Second, kill some of the microorganisms attached to the vegetables to reduce the total number of bacteria and bacterial contamination.
Third, to exclude the air in the vegetable tissues and reduce the oxidation of vegetables in the storage process.
(2)scalding and bleaching scalding and bleaching are the basic method of two, namely hot water scalding and steam scalding. Hot water scalding should be in line with the standard of drinking water quality, mostly soft water, a water temperature of 80 ~ 100 ° C, commonly used in the production of 93 ~ 96 ° C. Scalding time varies according to the type of vegetables and water temperature. Due to the large heat capacity of water, heat transfer speed, and thus scalding time than the same temperature steam scalding to short, and vegetable temperature evenly rising, applicable to more varieties, simple operation, does not require a large investment in equipment and other advantages. Still, there is also a large amount of water, vegetable nutrient loss, high water loss rate, manual labor intensity, and other disadvantages. Steam blanching commonly uses high-temperature water vapor or water vapor and air mixture as a heating medium. This scalding method on the vegetable cell tissue destructive less can reduce the loss of water-soluble nutrients, the vegetable flavor also maintains better, while reducing pollution and wastewater. Still, the method also has a large heat loss. Scalding is not very uniform. Water vapor is easy to condense on the surface of vegetables, and large investment in equipment and other disadvantages.
In recent years, the blanching method has been fast, energy-saving, and easy to operate and control the direction of development, including high-temperature quick steam blanching, microwave blanching, and room temperature acid blanching the main representative. High-temperature quick steam blanching refers to high-pressure high-temperature water vapor for a short time (5 ~ the 60s) to heat vegetables to achieve blanching effect, vegetable juice loss and improve its texture, high thermal efficiency (80%), energy saving.
Microwave blanching is prefabricated fresh vegetables in the electromagnetic field of 915MHz or 2450MHz, using the thermal and biological effects of microwaves to destroy the spatial structure of enzymes so that enzymes deactivate. This method makes the vegetables heated inside and outside simultaneously, the product temperature. The rise is fast and can be the scalding and bleaching treatment of vegetables in plastic packaging.
Normal temperature acid blanching is mainly used for vegetables prone to browning, such as mushrooms, which contain a large amount of polyphenol oxidase. The mushroom is treated at pH 3.5, 0.05 moL citric acid solution for several minutes, which destroys the enzyme's tertiary structure due to the low pH and citric acid, and citric acid complexes the central metal ion polyphenol oxidase to inactivate the enzyme.
(3)the test of scalding, no matter what scalding method is used, must strictly control the time and temperature of scalding. Scalding is not enough. It did not make the enzyme completely inactivated, but it made the vegetable tissue heated and destroyed. In this case, the changes in frozen vegetables in frozen storage will be even worse. Excessive blanching, tissue destruction are serious. The texture is too soft, the green color of vegetables into olive or even brown, and a waste of energy.
The temperature and time of scalding and bleaching should be based on the type of vegetables, maturity, size, the type of enzymes and process requirements, and other conditions. The scalding degree is the degree of enzyme inactivation, which is the indicator enzyme directly related to the scalding. Bleaching after the quality of vegetables. Generally to vegetables in the peroxidase activity just about all destroyed as the degree. 1.5% guaiacol alcohol solution and 3% hydrogen peroxide mixed in equal amounts, the blanching and bleaching of vegetable specimen slices immersed in it, such as in a few minutes do not change color, that is, hydrogen peroxidase has been destroyed. Otherwise, appear brown. Fatty oxygenase and peroxidase on some vegetables have a greater sensory impact, so they are also used as blanching indicator enzymes, such as green peas.
Why is the nutritional value of frozen vegetables high?
Many people think frozen food is unhealthy, so they think frozen vegetables are not as fresh and nutritious as fresh vegetables in general. The latest research shows that the nutritional value of frozen vegetables is higher than that of fresh vegetables in general.
Once harvested, fruits and vegetables slowly degrade and lose nutrients, and when most produce reaches the market shelves, it is not as fresh and nutritious as when it was first picked.
Sometimes farmers will harvest fruits and vegetables before they are ripe to facilitate long-distance transportation or maintain a better appearance, so the time for fruits and vegetables to develop complete vitamins and minerals will be reduced. In addition, fruits and vegetables in the transport process will be exposed to a lot of heat and light, degradation of some nutrients, such as the more fragile vitamin C and vitamin B1.
But frozen vegetables are usually frozen at the peak of ripeness. When the nutritional value of fruits and vegetables is just the highest, it can lock the most nutrients and antioxidants, retain the freshness of vegetables and nutrients, and not affect its flavor.
This processing method so that the water in the vegetables quickly crystallized into regular and small ice crystals, evenly scattered in the cells, vegetable tissue will not be destroyed. In contrast, the internal biochemical processes of vegetables can not be carried out, so bacteria and mold can not develop. Quick-frozen vegetables are easy to eat, get indoors without washing, cut, and slightly thawed. Because most frozen vegetables are steamed, some may also add salt and other seasoning categories, so cooked with rapid-fire, instantly cooked, its taste, color and vitamin content, etc., and fresh vegetables are similar.
Is it healthy to eat frozen vegetables?
Frozen vegetables are considered a healthy alternative to fresh vegetables because rapid freezing keeps many vitamins and minerals intact. As a result, the nutritional content of frozen vegetables is significantly higher than that of canned vegetables. Typically, frozen vegetables have more nutrients than fresh fruits and vegetables stored at room temperature for several days because the nutrients in fruits and vegetables decrease significantly over time due to light and heat. Also, frozen foods do not need preservatives to preserve them. Some people say that frozen vegetables have less nutrition than fresh ones. Select fully cooked vegetables to freeze. These ripe vegetables are rich in the best nutritional value before they are frozen by immersing them in boiling water, followed by rapid freezing to ensure quality to avoid contamination and destruction of organisms. This treatment is called hot blanching. The role of enzymes in vegetables is to promote ripening, but these enzymes begin to destroy the vegetables and reduce their nutritional value after ripening. Hot blanching technology blunts the activity of enzymes. This technology only leads to a small amount of vitamin loss. After hot blanching, frozen vegetables can be preserved for more than a year, so thanks to the enzyme inactivation, frozen vegetable nutrition will be better preserved than on the shelves of fresh ripe vegetables.