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â—† International process and equipment are mature There are two kinds of foreign edible paper. One is based on vegetables as the main raw material, the vegetables beaten, dried after molding; the other is the refinement of starch, sugar, and then add other food additives, and take the papermaking process similar method. From the perspective of application and development prospects, green products based on vegetables have more potential for development.
Vegetable paper was first developed by Japan and was also called paper dish. The common characteristic of vegetables and foods is that they are rich in dietary fiber, vitamins and minerals, of which dietary fiber is quite stable in processing and production. Therefore, the nutritional loss of processed paper products is very small, and the product moisture content is small (about 10%). Easy to transport and store. This not only increases the added value of vegetables but, more importantly, solves the problem of vegetables that are perishable and difficult to store.
At present, only Japan has achieved large-scale production of paper and vegetables, and its processing technology and equipment have entered the fourth generation. The maximum daily output is up to 30,000 per day for each production line. Japan's Sakai Chemical Research Institute has successfully extracted protein and lipid from bean dregs to make pure dietary fiber, which is then processed into edible paper. Others include fruit paper, vegetable paper and seaweed paper.
As far as the production process is concerned, there are mainly two methods. The first method is a compression molding method in which the slurry is laid flat on a forming plate and formed by two baking steps. Another method is a roll forming method, that is, the slurry is directly pressed into a paper shape via two counter-rotating press rolls, and is dried after being sliced ​​to obtain a finished product. Due to the great potential of the market, countries are actively conducting research on vegetable paper and its products. Edible paper is a research hotspot not only in Japan but also globally. Its products are mainly used by the United Nations for disaster relief and US military operations. It can also be used in many fields such as convenience food and edible packaging. It can be predicted that this new type of convenience food will have great market potential.
â—† Domestic technology and equipment just started in China. Research on vegetable paper products began several years ago. The relevant universities, research institutions, and enterprises and institutions have already done a lot of work in this area. On the basis of foreign research, many new ideas and methods have been proposed for the research of the process and molding equipment. However, the overall level of research is still not high, especially the study is limited to the design of the process test and equipment, but did not really take into account all aspects of industrial production. Therefore, the industrialization process of vegetable paper has been lagging behind in our country. Recently, there have been many media reports on the availability of paper and vegetable products in China, but small-scale, workshop-style production simply cannot drive the development of the industry. At present, the state has given great support to the development of deep processing of agricultural and sideline products. At this opportunity, various research units and enterprises are also actively preparing to explore a new path for the production of vegetable paper.
â—† two forming process options Roll forming. Roll forming is the earliest method of forming paper. This method is based on the processing of seaweed transplanted over. The process is:
Raw materials → Cleaning → Dicing → Fixing → Cooling → Beating → Seasoning → Rolling → Drying → Finished products This method is a traditional processing method. It is characterized by a large amount of vegetables in the finished product, a flat product appearance, and good sensory indexes; but The process is first formed and then dried, the drying process takes a long time, the nutrient loss is large, and it is difficult to achieve continuous scale production. Chen Jie and others used microwave drying technology instead of traditional drying, which greatly shortened the drying time and prevented excessive loss of nutrition. At present, most of the research on vegetable paper products in China is based on this method.
2. Roller forming.
Roll forming is a new type of forming method that is based on drum drying technology in food drying technology. The main process of this forming method is:
Raw materials → Cleaning → Dicing → Fixing → Beating → Seasoning → Drum drying and forming → Finished products This process uses a raw vegetable to be slurried. After the homogenization, the slurry is sent to the drum for coating, so that the slurry The drum is pressed into a sheet to form a roll, and the product is dehydrated after the drum is dried. It can be seen that this method is simultaneous drying and forming, forming efficiency is high, appearance quality is good, drying time is short, so the nutrient loss of vegetables is small; and in this way, we can adapt to different materials by controlling the rotation speed and heating rate of the drum. Processing. Roller drying forming method is currently more advanced forming method, because of its continuity, very suitable for industrial production, is a very promising way.
â—† The color protection and sulfur treatment methods require strict protection of the color treatment and the temperature treatment and the ambient temperature immersion treatment. There are many methods currently used for color protection. They are generally treated in alkaline solutions in the presence of NaHCO3. The basic principle is that the color of chlorophyll-containing vegetables will become dark after heating and blanching, while under alkaline conditions, the chlorophyll will form a stable sodium salt, thus playing a role in color protection. Sometimes under alkaline conditions, adding ZnCl or zinc acetate solution 牗 Zn + about 200mg/L ç‰ to replace the magnesium ions in chlorophyll to form a more stable zinc salt, this method can better prevent browning, better Maintain the original color.
Sulfur treatment is a process in which vegetables are treated with NaHSO3 (about 3%) or other sulfites, that is, vegetables are soaked in a sulfite solution for a period of time (usually 1 to 2 minutes) and then washed out. There is also a sulphur fumigation method, that is, in the confined conditions, burning sulphur powder, fumigation of vegetables, this method requires very strict conditions, generally do not use. The role of sulfur treatment is to use the strong reducibility of sulfite to destroy oxidase activity, thereby preventing oxidative discoloration in vegetable tissues when dried and heated, killing bacteria and microorganisms at the same time, and preventing deterioration during subsequent processing; in addition, it is an important point. The role is to increase the permeability of the cell membrane and accelerate the evaporation of water, so that the subsequent drying time is greatly shortened, which is critical for the entire process.
â—†Be careful when choosing binders. The main ingredients of vegetables are vitamins and dietary fiber. If no binder is added, the pulped vegetables will not be able to be formed. Especially when the roll forming process is used, the requirements for forming are relatively high. The choice of binder is especially important.
The types of binders currently used are mainly CMC, sodium alginate, modified starch or the like and used in combination. The choice of adhesive depends on the process. For example, for the roller compaction process, the optimal binder formulation for the CMC, sodium alginate, etc. is mixed by a certain proportion from the orthogonal test; and for the roll forming process, only certain food additives and vegetables are added. Can not be formed on the roller, it is also difficult to separate from the roller. Therefore, for this forming process, it is necessary to first prepare a slurry composed of a certain base material, and then mix the vegetables with this slurry to form a film on the drum. For example, the ratio of slurry in green vegetable paper processing is: the ratio of green vegetables, wheat flour, millet flour, and water is 4:6:1:9.
When selecting the type and amount of binder, not only the requirements of forming in the processing process but also the quality of the product must be taken into account. The appearance of the product requires that the surface of the product be smooth and uniform; the taste should be sticky and smooth, and the original flavor of the vegetables should be maintained as much as possible, without the feeling of sticking teeth.
â—† Homogenization process to be scrutinized At present, the homogenization process is rarely used in the research on paper and vegetables in the country. However, after the paper is beaten, it is coated or drum-formed. The homogenization process can further refine the fibers in the vegetable pulp, thereby improving product quality. For this highly viscous, but also contains a lot of fiber materials, the use of colloid mill for homogenization effect is not very good, according to the author's test, the colloid mill after the homogenization twice, the slurry fineness is still below 20 mesh. The effect of the shearing homogenizer is very obvious. The author used the QDL3-15 high shear homogenizer produced by Wuxi Qingda Food Equipment Co., Ltd. to conduct tests. The test results showed that 85% of the materials passed through 50 mesh.
Due to its high nutritional value, paper and vegetable products are easy to store and transport, and it is a good snack food and high-grade food packaging material, which must have great market demand. Once the research and development of paper and vegetable industry form an industrial scale, it will certainly have a major impact on the development of healthy food in China.
Edible packaging is one of the important development directions of modern food packaging, especially healthy food packaging. Although China's packaging industry has recognized the important environmental and economic value of such packaging, and its great market potential, but due to the limited technology and equipment, this packaging product is still very rare, the new packaging materials of the process and equipment There are fewer studies. To this end, we particularly review the research and development of edible packaging at home and abroad for the food industry, especially those engaged in the development of healthy foods.