3 Edible packaging materials
Edible packaging materials are rich in raw materials, can be eaten, harmless and even beneficial to the human body, have a certain strength, and have achieved rapid development in recent years. Edible packaging materials are now widely used in the packaging of foods and pharmaceuticals. The methods used are: the edible packaging material is made into a film and used as an inner package and an outer package of the product: wrapping candy; as a liner for sticky pastries; as a packaging bag for sealing packaged foods; dipping the goods and packaging the goods In the shell; made of disposable beverage cups or fast food containers and other rigid and semi-rigid containers; made of casings, fruit clothing and capsules.
The raw materials of edible packaging materials mainly include lakes, proteins, plant fibers and other natural substances.
Among the edible packaging materials based on corn, wheat, potatoes, beans, potatoes and other crops, the modification of corn starch into edible packaging materials is the most typical, and the processing technology and practical application are more mature. According to the additive, acid and alkali treatment, enzyme treatment or oxidation treatment method they add, they can be made into film, and can also be extruded to form film clothing for small food, and can also be made into a cup that is both waterproof and oil-proof. And fast food boxes and so on.
Using proteins to make edible packaging materials, there are animal protein and vegetable protein. Animal protein is derived from animal skin, bone, cartilage tissue, etc. This type of edible material has very good strength, water resistance, and oxygen permeability, and is particularly suitable for the packaging of meat foods, and plant proteins extracted from soybeans, etc. The film is processed and packaged, has good moisture-proof and oxygen-blocking ability, and has a certain antibacterial property, and is suitable for the packaging of fat-containing food, not only improving the shelf life but also maintaining the original flavor of the oily food.
Plant fiber edible packaging materials are mainly agricultural and sideline products such as wheat bran, bean dregs, and marine plants such as seagrass and seaweed. Although this kind of material has low nutritional value, it has a lot of weight loss and health care effects, such as alginic acid. Sodium, it is not absorbed by the body, but it has hypoglycemic, regulate the physiological role of the stomach, and can make cholesterol out of the body and have the effect of slowing poisoning. The plant fiber can be made into various containers, and be eaten together with the food after being cooked; or when used for packaging instant noodles seasoning, when the heat is applied, the water can be instantly dissolved without having to unpack, and the fresh-keeping packaging paper for fruit and vegetable can also be made The edible material with sodium alginate as the main component is impervious to lipid and vegetable oils, and is a good material for oil-resistant packaging.
Edible packaging materials can also be used as the main raw material of edible shellfish, such as shrimp and crab, and have abundant reserves in nature. The output is second only to cellulose. Chitin can be extracted from chitosan under alkaline conditions. After modification, chitosan has excellent film formation, good oil resistance, good moisture resistance from water, and transparency. This type of edible packaging material is now widely used in the packaging of fruits, bread, ice cream and other foods.
Edible packaging materials are a kind of very promising green packaging materials. The research in this field is also very active. The direction of development in the future is to use some of the above-mentioned main raw materials for blending modification in order to better meet the performance requirements for packaging. For example, an edible wrapping paper made of various vegetables and starch, a water-soluble edible wrapping material for packaging instant noodles seasoned with edible gelatin, honey, hydroxymethyl cellulose, and the like.
4 Natural Plant Fiber Packaging Materials
Paper made from wood pulp and straw pulp is the most familiar and widely used fiber packaging material. It has a wide range of raw materials. Waste can be used to recycle recycled paper and is easily corrupted in the natural environment. It is the most widely used green packaging material. material. In recent years, some new types of green paper packaging materials have been developed. Typical types are pulp molding and honeycomb paperboard products. Pulp molded products use waste paper and vegetable fibers as raw materials, and mold certain shapes of products from special molds on a molding machine. It is a three-dimensional papermaking technology, and its products are used as a substitute for foamed plastic EPS products. In tableware, poultry egg trays, fruit trays, industrial trays, food and semi-finished product packaging, medical device packaging. Northwest Agricultural University of China has conducted a lot of research in this area, researching and developing fruit and vegetable packaging linings, poultry egg trays, supermarket trays, corrugated paper, disposable tableware and other products. Its production process has matured and it has been widely marketed. Honeycomb paperboard is composed of upper and lower two face papers and hexagonal honeycomb core paper. It has the advantages of light weight, high strength, high stiffness, good cushioning, heat insulation, and sound insulation. It is a wood substitute and EPS replacement. Ideal as an environmentally friendly material for cushioning pads.
In particular, natural plant fibers refer to the natural plants other than trees, such as bagasse, cotton stalks, husks, corn stalks, rice straw, wheat straw, and waste paper fibers. The natural plant is a very rich source. Renewable natural resources. According to the survey, China's annual agricultural crops are more than 500 million tons. The orange stalk of plants has many advantages as a packaging material, such as good easing, medium performance, non-toxic, odorless, good ventilation performance, and completely natural degradation after use. In recent years, a series of green packaging products have been developed using natural plant fibers such as reeds, rice straw, wheat husks, bagasse, and bamboo forests. Take bamboo as raw material to produce bamboo plastic packing box and silk bundle box for packaging of mechanical and electrical products and heavy machinery. Bamboo, straw and other plant fibers are pressed into fiberboard after high-temperature sterilization, and then they are crushed and filled. Materials, adhesives, etc., after extrusion molding, can be made disposable fast food equipment, such as the expansion of the foam can also be made of slow; in the pad. Xi'an University of Architecture has applied natural plant cellulose materials such as straws and rice straw as main materials, developed safe and non-toxic substances, and developed a fully degradable cushioning packaging material. The product is small in size, light in weight, high in compressive strength, and somewhat flexible. Sex, can be fully degraded into organic fertilizer in the natural world in one month.
5 Genetically modified plant packaging materials
As mentioned earlier, although breakthroughs have been made in the research and development of microbial biodegradable biodegradable packaging materials, the following problems still exist: low production efficiency, low temperature difference between melting point and degradation, slow crystallization rate, and processing Difficult, expensive, practical applications are limited. Therefore, the cultivation of transgenic plants to produce fatty polyesters such as PHB and PHAs has become a hot topic in the research and development of biodegradable plastics.
With the rapid development of plant genetic engineering, the production of PHB for microbial fermentation is expensive, and some large companies have successively developed PHB and other packaging materials that use genetically modified plants as reactors. The long-term goal set by the UK's ICI/Zeneca Seed Company is to introduce the pathway for bacterial biosynthesis of PHB into appropriate crops to use large scale production of PHB/V packaging materials from transgenic plants: Monsanto launched a major project in 1996 with the aim of establishing Technology system for producing packaging materials using genetically modified rapeseed.
Monsanto company Houmile et al. reported that they used a key enzyme gene involved in the biosynthesis of PHB isolated from microorganisms such as Alacaligenes eutrophus to construct a gene containing four genes (IlvA446IbklB/ph-Ba, phbBtphbC). In the plant expression vector, each target gene is fused with a chloroplast-transmitting peptide (ctp) and a Lesguerella carboxylase promoter (P-Lhr), and the target gene is fused to the E93′ sequence terminator of the pea bcSE9 gene (E93′). ) The target gene phbB was used to transmit peptides on the small subunit of PeaBubisco. This multi-gene expression vector was introduced into Brassica napus by Agrobacterium-mediated method, and the transgenic plant seeds contained 7.7% of fresh PHB. Further changing the flow of intermediates in the biosynthesis of fatty acids and amino acids, the research team obtained genetically modified rapeseed that can accumulate PHB/V copolymers and demonstrated that the accumulation of the copolymers does not affect the synthesis and production of oil in rape seeds.
According to reports, two key enzyme genes (phbB and phbC) synthesized by PHB have also been cloned from Alcaligenes eutropha in China. The prokaryotic vector was constructed and introduced into E. coli for expression. The gene was also successfully introduced into potato. In order to increase the production of PHB, they completed the cloning of the phbA gene and constructed a seed-specific expression vector for the transformation of rapeseed. The gene product will be located in the rapeseed on-demand plastids. (Wen / Dai Hongmin Dai Peihua) (To be continued)
Edible packaging materials are rich in raw materials, can be eaten, harmless and even beneficial to the human body, have a certain strength, and have achieved rapid development in recent years. Edible packaging materials are now widely used in the packaging of foods and pharmaceuticals. The methods used are: the edible packaging material is made into a film and used as an inner package and an outer package of the product: wrapping candy; as a liner for sticky pastries; as a packaging bag for sealing packaged foods; dipping the goods and packaging the goods In the shell; made of disposable beverage cups or fast food containers and other rigid and semi-rigid containers; made of casings, fruit clothing and capsules.
The raw materials of edible packaging materials mainly include lakes, proteins, plant fibers and other natural substances.
Among the edible packaging materials based on corn, wheat, potatoes, beans, potatoes and other crops, the modification of corn starch into edible packaging materials is the most typical, and the processing technology and practical application are more mature. According to the additive, acid and alkali treatment, enzyme treatment or oxidation treatment method they add, they can be made into film, and can also be extruded to form film clothing for small food, and can also be made into a cup that is both waterproof and oil-proof. And fast food boxes and so on.
Using proteins to make edible packaging materials, there are animal protein and vegetable protein. Animal protein is derived from animal skin, bone, cartilage tissue, etc. This type of edible material has very good strength, water resistance, and oxygen permeability, and is particularly suitable for the packaging of meat foods, and plant proteins extracted from soybeans, etc. The film is processed and packaged, has good moisture-proof and oxygen-blocking ability, and has a certain antibacterial property, and is suitable for the packaging of fat-containing food, not only improving the shelf life but also maintaining the original flavor of the oily food.
Plant fiber edible packaging materials are mainly agricultural and sideline products such as wheat bran, bean dregs, and marine plants such as seagrass and seaweed. Although this kind of material has low nutritional value, it has a lot of weight loss and health care effects, such as alginic acid. Sodium, it is not absorbed by the body, but it has hypoglycemic, regulate the physiological role of the stomach, and can make cholesterol out of the body and have the effect of slowing poisoning. The plant fiber can be made into various containers, and be eaten together with the food after being cooked; or when used for packaging instant noodles seasoning, when the heat is applied, the water can be instantly dissolved without having to unpack, and the fresh-keeping packaging paper for fruit and vegetable can also be made The edible material with sodium alginate as the main component is impervious to lipid and vegetable oils, and is a good material for oil-resistant packaging.
Edible packaging materials can also be used as the main raw material of edible shellfish, such as shrimp and crab, and have abundant reserves in nature. The output is second only to cellulose. Chitin can be extracted from chitosan under alkaline conditions. After modification, chitosan has excellent film formation, good oil resistance, good moisture resistance from water, and transparency. This type of edible packaging material is now widely used in the packaging of fruits, bread, ice cream and other foods.
Edible packaging materials are a kind of very promising green packaging materials. The research in this field is also very active. The direction of development in the future is to use some of the above-mentioned main raw materials for blending modification in order to better meet the performance requirements for packaging. For example, an edible wrapping paper made of various vegetables and starch, a water-soluble edible wrapping material for packaging instant noodles seasoned with edible gelatin, honey, hydroxymethyl cellulose, and the like.
4 Natural Plant Fiber Packaging Materials
Paper made from wood pulp and straw pulp is the most familiar and widely used fiber packaging material. It has a wide range of raw materials. Waste can be used to recycle recycled paper and is easily corrupted in the natural environment. It is the most widely used green packaging material. material. In recent years, some new types of green paper packaging materials have been developed. Typical types are pulp molding and honeycomb paperboard products. Pulp molded products use waste paper and vegetable fibers as raw materials, and mold certain shapes of products from special molds on a molding machine. It is a three-dimensional papermaking technology, and its products are used as a substitute for foamed plastic EPS products. In tableware, poultry egg trays, fruit trays, industrial trays, food and semi-finished product packaging, medical device packaging. Northwest Agricultural University of China has conducted a lot of research in this area, researching and developing fruit and vegetable packaging linings, poultry egg trays, supermarket trays, corrugated paper, disposable tableware and other products. Its production process has matured and it has been widely marketed. Honeycomb paperboard is composed of upper and lower two face papers and hexagonal honeycomb core paper. It has the advantages of light weight, high strength, high stiffness, good cushioning, heat insulation, and sound insulation. It is a wood substitute and EPS replacement. Ideal as an environmentally friendly material for cushioning pads.
In particular, natural plant fibers refer to the natural plants other than trees, such as bagasse, cotton stalks, husks, corn stalks, rice straw, wheat straw, and waste paper fibers. The natural plant is a very rich source. Renewable natural resources. According to the survey, China's annual agricultural crops are more than 500 million tons. The orange stalk of plants has many advantages as a packaging material, such as good easing, medium performance, non-toxic, odorless, good ventilation performance, and completely natural degradation after use. In recent years, a series of green packaging products have been developed using natural plant fibers such as reeds, rice straw, wheat husks, bagasse, and bamboo forests. Take bamboo as raw material to produce bamboo plastic packing box and silk bundle box for packaging of mechanical and electrical products and heavy machinery. Bamboo, straw and other plant fibers are pressed into fiberboard after high-temperature sterilization, and then they are crushed and filled. Materials, adhesives, etc., after extrusion molding, can be made disposable fast food equipment, such as the expansion of the foam can also be made of slow; in the pad. Xi'an University of Architecture has applied natural plant cellulose materials such as straws and rice straw as main materials, developed safe and non-toxic substances, and developed a fully degradable cushioning packaging material. The product is small in size, light in weight, high in compressive strength, and somewhat flexible. Sex, can be fully degraded into organic fertilizer in the natural world in one month.
5 Genetically modified plant packaging materials
As mentioned earlier, although breakthroughs have been made in the research and development of microbial biodegradable biodegradable packaging materials, the following problems still exist: low production efficiency, low temperature difference between melting point and degradation, slow crystallization rate, and processing Difficult, expensive, practical applications are limited. Therefore, the cultivation of transgenic plants to produce fatty polyesters such as PHB and PHAs has become a hot topic in the research and development of biodegradable plastics.
With the rapid development of plant genetic engineering, the production of PHB for microbial fermentation is expensive, and some large companies have successively developed PHB and other packaging materials that use genetically modified plants as reactors. The long-term goal set by the UK's ICI/Zeneca Seed Company is to introduce the pathway for bacterial biosynthesis of PHB into appropriate crops to use large scale production of PHB/V packaging materials from transgenic plants: Monsanto launched a major project in 1996 with the aim of establishing Technology system for producing packaging materials using genetically modified rapeseed.
Monsanto company Houmile et al. reported that they used a key enzyme gene involved in the biosynthesis of PHB isolated from microorganisms such as Alacaligenes eutrophus to construct a gene containing four genes (IlvA446IbklB/ph-Ba, phbBtphbC). In the plant expression vector, each target gene is fused with a chloroplast-transmitting peptide (ctp) and a Lesguerella carboxylase promoter (P-Lhr), and the target gene is fused to the E93′ sequence terminator of the pea bcSE9 gene (E93′). ) The target gene phbB was used to transmit peptides on the small subunit of PeaBubisco. This multi-gene expression vector was introduced into Brassica napus by Agrobacterium-mediated method, and the transgenic plant seeds contained 7.7% of fresh PHB. Further changing the flow of intermediates in the biosynthesis of fatty acids and amino acids, the research team obtained genetically modified rapeseed that can accumulate PHB/V copolymers and demonstrated that the accumulation of the copolymers does not affect the synthesis and production of oil in rape seeds.
According to reports, two key enzyme genes (phbB and phbC) synthesized by PHB have also been cloned from Alcaligenes eutropha in China. The prokaryotic vector was constructed and introduced into E. coli for expression. The gene was also successfully introduced into potato. In order to increase the production of PHB, they completed the cloning of the phbA gene and constructed a seed-specific expression vector for the transformation of rapeseed. The gene product will be located in the rapeseed on-demand plastids. (Wen / Dai Hongmin Dai Peihua) (To be continued)