Bamboo shoot is a traditional food in China, which is rich in nutrition and people's favorite vegetable. Bamboo shoots are not only used as fresh vegetables, but also used to process canned bamboo shoots with clean water, or to produce various flavored bamboo shoots after fermentation. Due to the concentrated production period and short season, bamboo shoots often rot before being processed in the peak season, but there are no bamboo shoots in the off-season. Therefore, it is necessary to use fresh-keeping storage technology to regulate the market supply of bamboo shoots.
1. Harvesting of bamboo shoots: mainly winter bamboo shoots harvested in winter and bamboo shoots harvested around Tomb-Sweeping Day. Bamboo shoots are harvested when the shoot heads are just exposed to the soil. They are harvested too late, with much fiber and bitter taste. When harvesting, the soil around the bamboo shoots is peeled off to expose the bamboo whip, the base of the bamboo shoots is cut off with a knife, the bamboo shoots are taken out, and then the pit is covered and filled with soil, which will not affect the continuous growth of the mother bamboo.
2. Storage of winter bamboo shoots: The storage temperature of winter bamboo shoots should be 0 ~ 65438 0℃ and the relative humidity should be 90% ~ 95%. ① Burying: Strictly select and remove damaged, shriveled and frozen soft bamboo shoots. For short-term storage, it can be stacked in the cool outdoor place with a wet sand layer, with a pile height of about 1m, covered with sand 10cm, and covered with straw to prevent sun and rain. When winter bamboo shoots are buried, they must be placed vertically in a damp sand pile with shells, which can be stored for more than 1 month. If it needs to be stored for a long time, we should dig it outdoors, then pile the selected winter bamboo shoots and sand in the pit, and finally cover it with a thick layer of soil and straw. Don't cover it with plastic film, splash water to keep it moist to prevent deterioration and rot. (2) Salt water storage: put the whole winter bamboo shoots into a pickle jar (or pond) and soak them in concentrated salt water, and they can be stored for about 2 months, with the meat quality and shell color of the bamboo shoots unchanged. When eating, be sure to soak it in clear water for desalination. (3) Fresh-keeping treatment and storage: firstly, 25% sodium sulfite, 30% sodium bicarbonate, 10% calcium oxide and 40% garlic extract are used to prepare a preservative, and then bamboo shoots with smooth cut on the shell are selected, soaked with the preservative, and then the cut is coated with liquid paraffin, packed in plastic net bags and placed indoors, so as to prevent mildew and reduce water loss. It can be stored at 1 ~ 5℃ for more than 1 month.
3. Storage of bamboo shoots: Bamboo shoots are harvested when the temperature is high, and they are in a vigorous growth and development period, so they need to be refrigerated at low temperature to control rot. The specific method is to put the selected newly harvested spring bamboo shoots into a cold storage rack or basket, stack them for pre-cooling, then put them into polyethylene plastic bags with a thickness of 0.02~0.03mm, seal them, and put them into a cold storage rack, keeping the cold storage constant of 0 ~ 1℃ and the relative humidity of 90%-95%, which can keep fresh for more than 1 month.
Processing and fresh-keeping method of bitter bamboo shoots
Fresh bitter bamboo shoots have the characteristics of white meat, crisp and tender, slightly bitter and slightly sweet, fragrant and delicious, and are delicious food with table. The emergence period of bitter bamboo shoots is from April to July, and the emergence period is only 4 months. In order to eat fresh and delicious bitter bamboo shoots all year round, bamboo shoot farmers in Emei Mountain have created a variety of new preservation methods for bitter bamboo shoots in long-term practice, which are introduced as follows:
1. Buy fresh and high quality bamboo shoots. Fresh and tender bitter bamboo shoots have smooth shells, golden yellow, no obvious wormholes, and the ear leaves at the tip of the shells are green and tender and do not fall off. If the ear leaves are dull and easy to fall off, it means that the bamboo shoots in the shell have rotted and deteriorated. The big head of bitter bamboo shoots is solid and there is no hole. It's pulling bamboo shoots instead of hoes, so it's easy to get in with nails. Generally, the length of bamboo shoots with a diameter of 2 cm to 4 cm is 30 cm to 40 cm, and the length of bamboo shoots with a diameter of 4 cm to 6 cm is 40 cm to 50 cm. If it is too long, the bamboo shoots are too old and the quality is poor.
2. Steamed and refrigerated preservation method Bitter bamboo shoots should be shelled and processed as soon as possible. Cut off one side of the shell with a sharp knife, and be careful not to cut off the bamboo shoots. Then gently peel off all the shells by hand, cut off the tender shells of bamboo shoots with a sharp knife and clean them for use. After the water in the steamer is boiled, put the bamboo shoots into the steamer to steam/kloc-0.5 to 20 minutes, and then take them out to cool. Sprinkle a little salt on the surface of bamboo shoots, and then press 1 ~ 2 hours with a wooden board to remove excess water from bamboo shoots. Take out bamboo shoots to dry the surface moisture, put them into clean food preservation bags in turn, and seal them. Each bag 1kg ~ 2kg, put it in refrigerator or freezer, and keep it below 0℃. When eaten, it can be taken out and thawed for cooking, which can maintain the fragrance and rich flavor.
3. Fried and refrigerated preservation method: peel off the shell of fresh bitter bamboo shoots, scrape off the tender shell meat, wash and slice. Small bamboo shoots with a diameter less than 4 cm are obliquely cut into oval slices with a thickness of1.5 mm ~ 2 mm; Bamboo shoots with a diameter of more than 4 cm are cut in half first, and then obliquely cut into semi-circular thin slices. Put bamboo shoots into containers such as tanks and pots, sprinkle with appropriate amount of salt and mix well. After standing for 1 ~ 2 hours, the water was filtered out. Heat the wok, add high-quality lard (50g lard per kilogram of bamboo shoots), fry the bamboo shoots, spread them out of the wok, cool them in a spacious vessel, dry the excess water, put them in a clean food fresh-keeping bag, and seal them. Packed into small bags of 0.5 kg ~ 1 kg, and put them in refrigerator or freezer for cold storage. Delicious and delicious as new, the shelf life is over 18 months.
4. Canned storage preservation method Families without refrigerators can use canned storage method. Pickle jars, jars, bottles and other containers with a sink at the neck are selected, and the most suitable capacity is 5 kg ~ 1.0 kg. Make bitter bamboo shoots into bamboo shoots or bamboo shoots, put them into washed cans, press them while loading, and reserve appropriate space at the mouth of the cans. Then, fill the jar mouth with washed bamboo shoots, palm leaves, grass braids, etc. , and cover it. Finally, slowly fill the sink with water to cover the edge and isolate the air. If you use a container without a water tray, you can choose another sink, put the canned bamboo shoots upside down in the sink, and then fill the tank with water to cover the tank mouth, and the water depth should not exceed the filler at the tank mouth. Pay attention to adding fillers after each feeding, and often change water, inject water and check to prevent bamboo shoots from deteriorating due to water leakage. This method can last 12 months.
Bamboo shoots and their preservation techniques
Bamboo shoots are delicious, often eaten as vegetables, and have certain medicinal value. Bamboo shoots are sweet, slightly cold and non-toxic, and have the effects of quenching thirst, diuresis, clearing away lung heat and resolving phlegm. The cellulose contained in bamboo shoots can promote the peristalsis of intestinal wall, promote the secretion of digestive glands, facilitate digestion and excretion, reduce the retention of harmful substances in the intestine, and play a role in preventing and treating intestinal cancer. Therefore, bamboo shoots have become a favorite traditional food in people's daily life because of their rich nutrition.
Bamboo shoots are easy to lignify at room temperature, which greatly affects the nutrition and quality of bamboo shoots. After bamboo shoots are picked and stored at room temperature for 24 hours, 60% of them are lignified, and almost lose their edible value after 48 hours. Because bamboo shoots are mostly produced in mountainous or hilly areas with inconvenient transportation, it often takes some time from picking to selling, which further intensifies the lignification of green bamboo shoots. The annual output of bamboo shoots in China is 265,438+10,000 tons, ranking first in the world, and the output is on the rise. According to the prediction of relevant parties, the output of bamboo shoots in China will reach 3 million to 3.2 million tons in 20 10. Therefore, it is of great significance to study how to keep green bamboo shoots fresh. China commonly used preservation technology are:
(1) Coating treatment Coating treatment is to coat a film on the surface of bamboo shoots after shell removal, bottom removal and root removal, so as to delay the breathing intensity of bamboo shoots and thus slow down the loss of nutrients in the body. The main coatings are chitosan coating and konjac glucomannan coating. The general technological process of film coating is as follows:
Bamboo shoots → cleaning → removing the root shell at the bottom → color protection (8 minutes) → inactivation → coating → drying → plastic packaging → weighing → storage.
When coating, chitosan coating is about 1.5%, and konjac glucomannan coating is about 0.2%. The specific concentration should be based on the composition of the coating solution and the coating process.
The above-mentioned coating treatment involves the process of water fixation, and its main purpose may be to inactivate enzymes at the bottom of bamboo shoots and kill microorganisms. Generally speaking, the higher the inactivation temperature, the longer the time, and the more thorough the inactivation of enzymes and inhibition of microorganisms. However, some bamboo shoots will be cooked and softened during storage after long-term high-temperature enzyme inactivation, resulting in the loss of bamboo shoot juice and shortening the storage time of bamboo shoots. Therefore, different bamboo shoots will have different inactivation temperature and time. It is reported that the temperature used for inactivation is about 60℃ and the time is 30 ~ 60 seconds.
(II) Chemical Reagent Preservation There are mainly two kinds of chemical reagents for preservation: (1) adding chemical reagents that can release sulfur dioxide and carbon dioxide. The released carbon dioxide increases the concentration of carbon dioxide in the packaging system, thus inhibiting the respiratory intensity of bamboo shoots; Sulfur dioxide is used to inhibit microorganisms and enzymes, so as to achieve the purpose of preservation. Commonly used sulfur reagents are sodium sulfite, sodium pyrosulfite and sodium dithionite. (2) preservatives. Sodium benzoate, potassium sorbate and sodium chloride are mainly used. For example, Xu Ping in Simao, Yunnan, used sodium benzoate and sodium metabisulfite as chemical additives to keep bamboo shoots fresh, and achieved success (national patent 90 10909 1). However, due to the increasing demand for food, the use of preservatives has been controlled to a certain extent. Therefore, when using preservatives, we must pay attention to the scope of use of different preservatives and their maximum dosage.
(3) Cold storage: put the processed bamboo shoots into a breathable plastic basket and put them into a cold storage. The temperature is generally controlled at 3 ~ 6℃ and the humidity is 85% ~ 95%. Proper cooling can effectively reduce the respiratory intensity of bamboo shoots, delay the emergence of respiratory peak, and greatly delay the decomposition of protein, fat, starch and other substances in bamboo shoots.
(4) Film packaging is sealed with plastic bags filled with bamboo shoots, and some are vacuum sealed. Commonly used plastic bags are mainly PE bags. However, this treatment can easily lead to anaerobic respiration of bamboo shoots and make the quality of bamboo shoots worse. Therefore, this method is often combined with other methods, such as low-temperature storage, adding solid buffer release agent and activated carbon that can release sulfur dioxide and carbon dioxide into the packaging bag.
Storage and processing method of winter bamboo shoots
Winter bamboo shoots are delicious and nutritious, and they are the top grade with meals. With low water content, it is easy to transport and store, and it is a good raw material for processing canned winter bamboo shoots, which is well received by consumers, especially the canned winter bamboo shoots processed and exported are very popular in Japan and the United States, and the export is high.
First, the storage of winter bamboo shoots
1. Indoor yellow mud storage method. Choose a house with a concrete wall around the mud. First, spread yellow mud with a thickness of about 10cm on the ground (water content is 50-70%), and then pile the winter bamboo shoots horizontally, with a layer of yellow mud and a layer of winter bamboo shoots covering the yellow mud with a thickness of 10- 15cm. For a small amount of household storage, wooden boxes can also be used, with 5-8cm sand mud at the bottom, winter bamboo shoots lying flat, covered with 1cm thick sand mud, and then covered with winter bamboo shoots. The top sand mud is 3cm away from the box, cover the box cover and store it in a cool place. This storage method can be stored for about 1 month in spring and summer, and it can still keep fresh.
2. Dig a hole for outdoor storage. You can dig a hole in the south-facing ditch slope or at the foot of the mountain. The depth of the hole is 2 ~ 2.5 meters, which means that the stomach is small and easy to keep warm and moisturize. Spread wet sand with a thickness of 10 ~ 15 cm (water content 50 ~ 70%) at the bottom, evenly arrange the roots of winter bamboo shoots downward and the tips upward, and cover them with sand. The practice of the second floor is the same as that of 1 floor, that is, the floor is placed 5 ~ 60 cm away from the ceiling to facilitate air exchange, and 20 cm of mud is covered with wooden boards or cement boards. There are many storage methods, and the fresh-keeping time in spring and summer can be as long as 6 months.
Second, the processing of winter bamboo shoots
1. Bamboo shoots in soy sauce. Peel and wash the bamboo shoots, and cut them into bamboo rings with a thickness of 3-4 cm. According to the proportion of bamboo shoots 100 kg, soybean oil 10 kg, salt 13 kg, sugar 2.5 kg and wine 300 g. Mix the weighed soybean oil, salt and sugar as ingredients. Choose a pot with a big belly and a small mouth, wash it and dry it for later use. Sprinkle a layer of ingredients on the bottom of the jar, then put the bamboo shoots into the jar layer by layer until they reach the mouth of the jar, sprinkle a little salt on them, and then cover them. After a few hours, when the volume of bamboo shoots in the jar is slightly reduced, bamboo shoots and ingredients should be added, a layer of ingredients should be sprinkled on the surface, rice wine should be poured, then sealed, and stored in a ventilated and cool place. The jar can be opened in about half a year. The superior sauce bamboo shoots are soft, light yellow-brown, moderately salty and unique in flavor.
2. dried bamboo shoots. Peel the bamboo shoots, remove the mud, wash them and put them in the pot. For every 100 kg of bamboo shoots, add 3-5 kg of salt and 30 kg of water at one time and cook for 6-8 hours. Turn the pot several times in the middle, and turn the bamboo shoots at the bottom of the pot to the surface of the pot. The cooking time of bamboo shoots should be flexibly controlled according to the firepower, and it is forbidden to cook bamboo shoots too badly for too long. When the bamboo shoots are not rotten, take them out of the pot, drain them and spread them in the drying room. During the drying process, keep the temperature at 40 ~ 60℃ and turn the dried bamboo shoots frequently until the color of the bamboo shoots is Huang Liang and the bamboo shoots are not greasy. When baking, the temperature should not be too high, otherwise the quality of dried products will be seriously reduced.