Bamboo shoots are traditional foods of our country and are nutritious
Vegetables that people love. Bamboo shoots contain 18 kinds of amino acids, some of which are essential for the human body. In 100g fresh shoots, the total amount of amino acids is about 2g. Bamboo shoots also contain various trace elements necessary for the human body, such as Se and Ge. In view of the fact that bamboo shoots have high protein, low fat, selenium-containing trace elements, and their rich dietary fiber, they have been hailed as "health foods." Bamboo shoots are used for the processing of clear water bamboo shoots as well as for the production of various seasoned bamboo shoots, except for vegetable fresh food. However, the use and processing of bamboo shoots are faced with the problem of preservation, which is mainly reflected in the following aspects: (1) The shoots are concentrated, and the production of bamboo shoots is short, resulting in the processing and processing of bamboo shoots and processing plants during the peak season, and no supply of raw materials during the off-season. Therefore, it is necessary to solve the problem of storage and transportation through preservation. (2) Fresh bamboo shoots with good quality bamboo shoots (such as sweet bamboo shoots, etc.) have a good flavor and must be preserved by fresh-keeping treatment. (3) Some varieties of bamboo shoots have good flavor after being cooked, but after being made into clear water, the quality of flavor decreases. Therefore, it is necessary to study the preservation technology of cooked bamboo shoots. 1 Review of storage techniques for bamboo shoot preservation 1.1 Traditional storage and preservation of bamboo shoots Research on the preservation of traditional bamboo shoots has focused on the storage of mature bamboo shoots. This is different from the strict preservation, but it is adaptable to the needs of the bamboo shoot processing factory and is easy to be used. The bamboo shooter operates and receives, and can well preserve the color, crispness and freshness of bamboo shoots. The main storage methods are as follows. 1.1.1 Use of Chemical Additives Storage The use of chemical additives (ie, preservatives) for fresh-keeping of cooked bamboo shoots is currently the most widely used method. The main research results are: (1) Preservatives developed by Yalin Institute of Chinese Academy of Forestry in the 1980s (Patent No.), whose main component is potassium sorbate, but the acidity of cooked bamboo shoots after preservative treatment is defective in terms of brittleness. (2) In the early 1990s, Xuping, Simao, Yunnan Province, used sodium benzoate and sodium metabisulfite as chemical additives to preserve bamboo shoots and won the National Invention Award (Patent No.). However, due to the toxicity of these additives, the promotion was limited. (3) The results of Ding Xingcui et al. of the Bamboo Research and Development Center of the Ministry of Forestry used potassium sorbate 800 mg/kg + lactic acid 3500 mg/kg + citric acid 1750 mg/kg as preservatives. 1.1.2 Fresh shoots of mature bamboo shoots and fresh water are cooked by high temperature heating. The microorganisms on the bamboo shoots are killed. They also stop the activity of enzymes and reduce the physiological activity. Then they are placed in flowing streams and can be preserved. For a time without deterioration. 1.1.3 Preservation of cooked bamboo shoots salt Use of preserved salt pickled bamboo shoots to form a high osmotic pressure environment around the shoots, thereby inhibiting microbial activity and stopping the activity of enzymes. This preservation method adapts to the needs of the processing plant, but salted and pickled After the formation of sour, so that the flavor of bamboo shoots has declined. 1.1.4 Other methods Traditional bamboo shoot preservation techniques include: preservation of sulfur preparations, preservation at a low temperature, preservation of bags, and the like. 1.2 Strictly speaking, the preservation technology of bamboo shoot preservation research is strictly to preserve freshness, that is, to use all feasible means and technical measures to postpone and delay the change of crop quality to adverse changes. At the same time, due to the continuous improvement of storage and packaging conditions, the demand for fresh products from the society is expected to reach, so compared with traditional preservation methods, the current research on bamboo shoots preservation is reflected in: (1) Fresh-keeping materials are fresh bamboo shoots; (2) Preservation work is a systematic project that includes the control of the harvesting process and the use of various preservation measures. In recent years, research on the preservation of fresh bamboo shoots has yielded the following results. (1) Physical Preservation: Liu Yaorong, etc. of the Yalin Institute of the Chinese Academy of Sciences, through the quick-freezing and refrigerating of the air-suction, the fresh bamboo shoots with shells can be stored for more than 3 months. (2) Chemical preservation: The solid antistaling agent developed by Xu Jinsen of Xiamen University (concentration: Na2SO3 25% + NaHCO3 30% + CaO 10% + 35%
Garlic extract) is applied to bamboo shoots with mane trees at room temperature (10- 15°C) can be stored for 5 weeks. Liquid preservatives (content of 2,4? D 1500mg/kg + BHT 700mg/kg + NaHCO3 10% and sodium benzoate 700mg/kg), stored at room temperature with bamboo shoots bamboo shoots up to 7 weeks. (3) Chemical preservatives combined with water storage: Su Yunzhong, Gutian, Fujian, selected for preservatives and ethylene preservatives, and fully crushed, with moisture content of 55%-65%, no mixed humus and organic matter, no pollution The soil of yellow earth or earth under the soil layer is used as buffer soil to store fresh bamboo shoots, and the moisture and temperature of the storage environment are adjusted at the same time. This method can be stored in a constant temperature refrigerator at (10.5)°C, and the storage time can reach 50 to 80 days. The rate is 98.9%. 2 Basic issues affecting the preservation and storage of bamboo shoots The basic problems of the preservation and storage technology of bamboo shoots and their effects on preservation and storage can be summarized as follows. 2.1 Shoot Characteristics of Bamboo Shoots Among 500 kinds of bamboos in China, most of the bamboo shoots are edible, such as bamboos distributed in the mid-subtropical zone and southern bamboo in the subtropical zone. Among them, bamboo shoots have winter and spring (such as bamboo shoots) and summer and autumn (such as bamboo shoots). Bamboo shoot characteristics have a great influence on fresh bamboo shoots. 2.2 Physiological activity Strictly speaking, bamboo shoots are edible buds. As the most vigorous part of physiological activities in plant organs, the measures for preservation and storage are relatively high. After bamboo shoots were harvested, shelled bamboo shoots were isolated for 2 hours, and the respiratory intensity was 47.38 CO2mg/(kgh). After 5 hours in vitro, the respiratory peak reached 277.84 CO2mg/(kgh), and the peeled bamboo shoots were isolated from the body for 2 hours. The respiratory intensity was 399.96 CO2mg/ (kgh) was 1178.08 CO2mg/(kgh) in 5 h in vitro, and softening and decay from the wound surface was observed on the appearance. At the same time, winter bamboo shoots at 10-15 °C, the natural water loss rate of 20% within 2 weeks, while the South subtropical Ma bamboo shoots, production of bamboo shoots for the summer season, the loss of water faster. 2.3 Cultivated harvest characteristics Bamboo shoots are extensively managed, which makes their storage fresh and has its own characteristics: (1) The size of the harvested wounds is different, especially the wounds are large, resulting in strong traumatic breathing; (2) Bamboo shoots own fiber The degree of diversity; (3) Bamboo shoots of different sizes; (4) acquisition of bamboo shoots mixed with good diseases, which have brought certain difficulties to the preservation of bamboo shoots. 2.4 Causes of Preservation and Storage Difficulty of Bamboo Shoots Caused by Microbial Infestation In addition to its strong physiological activity, microbial infestation is also one of the main causes of spoilage. Unlike the controlled fine harvesting of fruits, bamboo shoots come into contact with soil and there are secondary microorganisms. Infection. In addition, other harvesting measures, such as knives and piles, can cause the shoots to be infected by microorganisms. 2.5 Segmentation characteristics Fresh-keeping storage, especially before entering the supermarket, must split the bamboo shoots quantitatively. In the segmentation, the factors affecting storage are: 1 If the wound surface is smooth, the damaged cells are few, and the wounded breath is low; Different choices also affect breathing. 3 The key technology for preservation and storage of bamboo shoots is a systematic project for the preservation and storage of bamboo shoots. The adoption of controlled harvesting techniques is a prerequisite. Based on this, it is necessary to focus on two issues: First, to prevent bacteria from infecting and cause rot. Metamorphism; Second, to reduce its physiological activity, delay the peak of breath, avoid loss of water due to physiological activities, tissue structure aging, in order to maintain the bamboo shoots of color, smell, taste, brittle fresh storage purposes. 3.1 Controlled harvesting technology research When harvesting bamboo shoots, it is highly susceptible to microorganisms, which is the main reason for its spoilage during preservation and storage. At the same time, due to its large wound surface, it reaches a respiratory peak within about 5 hours after harvest, resulting in a decline in quality. The following aspects should be studied and technical standards established. (1) Degree of fibrosis of shoots: Grasp the degree of fibrosis of the shoots, ensuring both their flavor and storage. (2) Control of cutting surface: Select the cutting plane to reduce the damage of the injured breath and perform bamboo shoot harvesting operations. (3) Harvesting method: Select sharp tools to reduce cell strain of bamboo shoots. (4) Water conservation measures: stacking methods after harvesting should ensure that the water loss of bamboo shoots is minimal. (5) Fractionation of bamboo shoots: To study the grading standards for different types of bamboo shoots, to carry out the classification and purchase according to their respective standards, and to uniformly maintain freshness. 3.2 Antibacterial and anti-mildew technology The main microorganisms that affect the storage and storage of bamboo shoots come from the soil, the pests and the air of the bamboo shoots, and the first part of the infection is the wound surface. Therefore, the main antibacterial and anti-mildew measures should be based on the wound surface. At the same time, it is very important to sterilize bamboo shoots before storage and preservation. Because the bamboo shoots can be eaten directly, the selected reagents must be safe and non-toxic, so care must be taken. 3.2.1 Coating Technology The coating technology is to apply a layer of polymer liquid film on the wound surface of bamboo shoots, and to form a thin and uniform film after drying, which can reduce traumatic breathing of bamboo shoots and reduce the consumption of nutrients. Prolong the shelf life of bamboo shoots; in addition, it can also reduce evaporation and water loss of bamboo shoot body water and keep it fresh and plump; at the same time, it can reduce the decay caused by the infection of microorganisms. At present, the membrane technology has been widely used in the preservation of fresh fruits and vegetables, such as citrus, apples, tomatoes, sweet peppers, etc., Xu Jinsen in the study of fresh bamboo shoot storage, paraffin coated wounds, combined with other methods, the effect is very good. There are many coating materials, mainly composed of hydrophobic substances, water, surface active substances and water-soluble high-molecular substances, which are obtained through emulsification, dispersion and heat sterilization. The ideal membrane material should have the following characteristics: a certain viscosity, easy to film; forming a film uniform, continuous, with good preservation; non-toxic, edible, no odor. For example, the three components of Semper’s coating preservatives in the United Kingdom are sucrose esters, sodium carboxymethyl cellulose, monoglycerides of fatty acids and diglycerides, which are all natural substances and are safe and non-toxic. Japan uses a polymer solution made of starch, protein, and vegetable oils to make mixed paints. It has a good effect on citrus and apples. Yuan Yihua, Fan Mingtao, and others used chitosan to study fresh-keeping coatings on tomatoes, sweet peppers, and cucumbers. The results showed that fresh-keeping effects were good. However, if the membrane technology is not properly applied, it will have the opposite effect on fresh storage, such as insufficient disinfection of the environment, or bamboo shoots, because sucrose, chitosan, and starch are all good media for microorganisms, often causing coating materials. First of all, it leads to pollution, and then leads to decay of the bamboo shoots. 3.2.2 Preservation of Fungicides In the world, after the fruits and vegetables are harvested, fungicides are generally used to control their decay. Due to the extensive harvesting operations of bamboo shoots, the chance of microbial infection is more than that of other fruits and vegetables. Therefore, the use of fungicides is essential in the preservation and transportation of bamboo shoots. The selection principle of antisepsis and mildewproof reagents must first be aimed at a specific type of disease that occurs after harvesting. Therefore, it is necessary to conduct research on the isolation and identification of the major pathogens of post-harvest bamboo shoots spoilage; secondly, the residual amount of selected reagents must be used. Meet the requirements of food hygiene. In addition, we must pay attention to the rapid emergence of pathogenic bacteria resistance problems. Several major anti-corrosion and anti-mold agents are introduced. (1) Organic acids: including sorbic acid, lactic acid, citric acid, etc. The solution at a certain pH, can better inhibit the growth of bacteria. Patent No. is the preservation agent. (2) Chlorine and Hypochlorite: These fungicides are mainly used for the disinfection of water to reduce the microbial content of bacteria in water. In Japan, 100 mg/kg of sodium hypochlorite solution is used to disinfect the cabbage lettuce and then sold directly to the supermarket. (3) Sulfur dioxide and sulfite: The main application of SO2 to control post-harvest crops is not easy to rot, its application has a long history, such as the use of a large number of grapes in the storage and transportation process; Zhou Yun, etc. using S treatment for longan storage better Effect; Xu Jinsen using Na2SO3 for bamboo shoot preservation also has better results. (4) Other bactericides: There are many commercial bactericides currently available for fruit and vegetable preservation, such as o-phenyl phenol, sec-butylamine, teicotin, imazalil, beta-aluminum, and acetaminophen. The key lies in the selective application, on the one hand, against pathogens that cause corruption, and on the other, requiring low toxicity and low residue. 3.2.3 Methods of physical sterilization Sterilization is currently used by many isotopes, and 60Co is used as a radiation source. The proper dose of radiation can not only sterilize the surface of bamboo shoots but also delay the physiological activity of bamboo shoots to a certain extent. However, due to the large investment in capital construction using this approach, the use of bamboo shoots for fresh storage is limited. Others include microwave preservation and ozone preservation. 3.3 Techniques for retarding physiological activity If the physiological activity of fresh bamboo shoots can be retarded during the fresh-keeping storage of bamboo shoots, the formation of their respiratory peaks can be delayed, and ethylene formation that promotes respiration can be reduced, and excessive shoots caused by high-intensity traumatic breathing can be avoided. Body fibrosis avoids breeding of microorganisms due to increased temperature of the storage environment caused by respiratory heat. The main measures for delaying physiological activity include: low temperature treatment, hormone treatment, modified atmosphere treatment and heat treatment. 3.3.1 The temperature range required for the normal life of low-temperature treatment plants is 15-35°C. The higher the temperature, the stronger the enzyme activity in the plant and the greater the respiration. The temperature increases by 10°C and the respiratory intensity increases by 1 to 1.5. Times. Lowering the temperature can reduce its respiratory intensity and delay the arrival of its respiratory peak. Simultaneously, low temperatures can reduce the production of ethylene in fruits and vegetables. At low temperatures, the physiological role of ethylene in promoting aging is strongly inhibited. Therefore, in the preservation of fruits and vegetables Each type of fruit and vegetable has its own suitable storage temperature, that is, suitable temperature for storage. For bamboo shoots, storage temperature is the temperature at which the physiological activity of post-harvest bamboo shoots is reduced to a minimum without causing physiological disorders. There are many studies on the optimum storage temperature of other fruits and vegetables. Bamboo shoots have not been systematically studied. Su Yunzhong's temperature is (10.5)°C combined with other methods. The average bamboo shoots are stored for 50-80 days. Liu Yaorong combines rapid freezing in a constant temperature library at 1°C ( -18°C) The bamboo shoots can be stored for up to 3 months. 3.3.2 Physiological activities of hormones treated with bamboo shoots are all regulated by endogenous hormones. Endogenous hormones are very low in plants, but their physiological activity is very strong. Phytohormone can be used to delay physical activity if appropriate concentrations of hormones are applied to plants in vitro. effect. (1) Auxins: If the pineapple fruit is soaked with a 500 mg/kg NAA solution, the ripening of the fruit can be delayed and the sale time of the fresh fruit can be prolonged. Other auxins are 2,4? D, etc., such as Xu Jinsen's liquid preservative contains 2,4? D (500mg/kg). (2) Gibberellins: The use of gibberellin (trade name “920â€) can significantly delay the maturation of bananas, mangoes, etc., and its role is to reduce the respiratory intensity and postpone the occurrence of respiratory peaks. (3) Cytokines: Commonly used BA (6 benzyl adenine), which has a certain effect on longan and litchi storage, but it is expensive and not widely used in production. (4) Growth inhibitors: include natural growth inhibitors such as abscisic acid and salicylic acid; synthetic inhibitors such as triiodobenzoic acid, schizophylline, chlormequat, chlorpyrifos, and qingsin. For example, treatment of mango with Qingshui 10-20ml/L can delay ripening later. There is no more report on the application of hormones outside bamboo shoots for the preservation of bamboo shoots. In view of the low use of hormonal products and better safety, they can be tested and used in combination with other methods to preserve bamboo shoots. 3.3.3 Atmosphere conditioning after harvesting bamboo shoots, ie by reducing the ratio of O2/CO2 within the storage environment of the bamboo shoots, in order to reduce the ethylene content that promotes aging, thereby reducing the aerobic respiration of bamboo shoots and avoiding The emergence of oxygen breathing. At present, this kind of treatment is widely used in commercial fresh-keeping storage of fruits and vegetables. (1) Ambient air conditioning: In a closed storage space (such as a cold storage or high-density airtight packaging film), increase the concentration of CO2 and reduce the concentration of O2. In terms of equipment, CO2 and O2 are pumped separately by two air pumps. In storage. For example, in Japan, lettuce is stored in a cold storage at 0-5°C, with an O2 concentration of 5-30 ml/L and a CO2 concentration of 60-100 ml/L. In addition, the storage environment of N2 has also been applied commercially. In the adjustment of the environmental gas, there are several processing methods that can also achieve the purpose of fresh-keeping: (a) high-concentration short-time CO2 treatment, Japan uses 20% -60% of high-concentration CO2 to treat lettuce with lettuce for 12-48 hours, and then Stored in cold storage, the effect of storage on vegetables is quite good; (b) storage under reduced pressure, reduce the pressure in the storage (bag) to 1/5-1/10 air pressure (1atm =Pa); (c) vacuum Package storage; (d) Gas replacement (air evacuation filled with CO, etc.). Due to equipment and other reasons, environmental gas regulation has just started in China, but it has formed better commercial applications in Japan and abroad. Research in this field should have good prospects for the preservation of large quantities of bamboo shoots. (2) Gas regulators: Gas regulators are substances that can absorb O2, C2H4, CO2, or CO2, and apply them to bamboo shoots to form a low-O2, high-CO2, and low-C2H4 environment. So as to delay the breathing of the bamboo shoots and achieve the purpose of fresh keeping and storage. Specifically, there are: (a) Ethylene absorbents: These include physisorption absorbents and oxidative absorption absorbents. Physisorption type absorbents mainly include: zeolite, calcium silicate, activated carbon; oxidized adsorbents mainly use the characteristics of ethylene oxidation, and more use of oxidants, such as KMnO4, peroxides such as calcium peroxide, sodium peroxide and so on. In the production of a mixture of more than two adsorbents, such as: calcium silicate 20% + KMnO4 80% (weight ratio), after mixing, can absorb decomposition of low-density ethylene in the storage environment in parts per million. (b) Deoxidizers: Deoxidizers mainly use reducing substances such as Fe powder, Zn powder, hydrosulfite, and sulfite as the main agent, together with a synergist, and are mainly used to reduce the storage environment. O2 content, thus retarding bamboo shoots breathing, such as iron powder 78g + NaCl 1g + Ca (OH) 2 6g + activated carbon 15g fully mixed, sealed with fruit into a container, placed in a 1000ml container, all O2 removed after 4 days The preservation effect is good. 3.3.4 Heat treatment In fresh-keeping storage of fruits and vegetables, after a short period of high-temperature treatment, kill or passivate pests or pathogens on the fruit to reduce decay, while changing some of the metabolic processes of fruits and vegetables after harvest to achieve the purpose of preservation and storage, known as heat treatment. Heat treatment is a kind of quarantine method. In recent years, it has been used in fresh-keeping because of its antibacterial and anti-mildew properties, its slowing of physiological activity, and its non-chemical residue. The heat treatment methods include: hot water immersion, hot saturated steam and hot air treatment, etc. It is also possible to try infrared or microwave technology for heat treatment. Such as Gao Yuanjun, using 30-35 °C, 24-36 h conditions to deal with hawthorn, room temperature storage for 200d, good fruit rate of 91.7% -94.6%; Europe and other applications of hot air banana, 45 °C, 12min conditions It can delay banana ripening and aging. After hot air treatment, the respiratory and ethylene release peaks appeared later and peaked smaller, and the cell membrane integrity of the peel remained well. Research on preservation and storage technology of bamboo shoots should break through the limitations of single-technology research that was only aimed at a certain link in the past. It should begin with studies on controlled harvesting measures, conduct comprehensive research on antibacterial and mildew-relief and delay physiological activities, etc. Technology to facilitate the promotion of applications. Bamboo shoots are scattered in origin and are distributed in some remote mountainous areas, making it difficult to conduct controlled unified acquisitions. In response to these characteristics, the problems in the division and research of the various aspects of technical treatment in bamboo shoot preservation are summarized as follows: (1) Harvest period: From harvesting to acquisition, the research focuses on the short-term preservation technology of bamboo shoots for preservation and preservation of water. (2) Acquisition period: Processing technology at the time of unified acquisition. (3) Transport period: Reasonable transportation conditions. (4) Factory storage: Storage conditions for a large number of bamboo shoots. (5) Supermarket processing: Handling and storage conditions of bamboo shoots as vegetables before entering supermarkets
Walnut
Xianfeng Agricultural And Forestry Products Co., Ltd. , http://www.sx-honey.com