Classification and introduction of edible film - polysaccharide edible film
In our impression, most of the packaging materials are inedible, even if it is a paper material of natural origin, it is difficult to eat directly with various additives due to bleaching in the later stage, and the taste is extremely poor.
But the use of edible film in our country can be traced back to the 12th century. As early as the 12th century, our ancestors used waxing to prolong the shelf life of citrus. Edible sausage casings and glutinous rice paper are also the earliest typical edible packaging used in my country.
Unexpectedly, your favorite sausage casing is a typical edible film.
According to scientific definition, edible film refers to a composite film formed by edible materials, which is mainly composed of natural macromolecular substances such as lipids, proteins and polysaccharides. Film-forming materials can be divided into main agents (polysaccharides, proteins), hydrophobic agents (waxes, fatty acids, etc.) and plasticizers (polyols and lipids) according to their functional characteristics.
Compared with synthetic packaging materials, the edible film can be biodegraded without any pollution. It can also be used as a carrier for food flavors, nutritional fortifiers, antioxidants, and antimicrobial agents.
At present, edible coating films and edible packaging films in my country are mainly used in foods such as fruits, vegetables, candies, nuts and cakes.
According to the classification of raw materials, edible films can be roughly divided into four categories: polysaccharide edible films, protein edible films, lipid edible films and composite edible films. The following is an introduction to each type of film one by one.
Polysaccharide edible film
Polysaccharide edible film is made of starch, modified starch, edible gum, and fiber derivatives as the main raw materials. Due to the special long-chain helical molecular structure of polysaccharides, its chemical properties are stable and suitable for long-term storage and various storage environments, but they are all hydrophilic polymers, and their moisture resistance is generally very small. , Intermolecular hydrogen bonds and intramolecular hydrogen bonds play an important role.
1.Cellulose edible film
In recent years, countries around the world have attached great importance to the research and development of modified cellulose edible packaging films. The production of easily degradable composite plant fiber disposable food and diet packaging materials developed in Xinjiang has been commercialized. Liu Linwei et al. used methyl cellulose and carboxymethyl cellulose as raw materials, and used stearic acid, palmitic acid, beeswax and agar as plasticizers and enhancers to prepare translucent, soft, smooth, and melt-in-the-mouth. Packaging film with high tensile strength, low moisture permeability and breathability.
For the purpose of developing wheat gluten protein film, Li Mengqin et al. conducted research on wheat gluten protein film and its improvement in moisture resistance. Through single factor experiment and orthogonal experiment, the main factors affecting wheat gluten protein film formation and the optimal process were determined. conditions, and further improve the moisture resistance of the film by adding stearic acid and paraffin. The results show that the paraffin-added film has about 10% higher moisture resistance than the stearic acid-added film.
2.Starch edible film
Starch edible film is made of starch as the main raw material. The raw materials of starch edible film are corn, wheat, sweet potato, potato, konjac and other starches, and the adhesives used are mostly natural non-toxic vegetable glue or animal glue, such as gelatin, agar and natural resin glue.
In the late 1960s, extensive research on edible film was carried out abroad, while domestic research started relatively late. The cereal film developed by Clemson University in South Carolina, USA, uses corn, soybean and wheat as raw materials to make paper-like film, which is used for packaging of sausages and other foods, and can be eaten. Maria A Garcia et al made a preliminary discussion on the application of starch film.
The starch was modified with a dilute alkaline solution and glycerol was added as a plasticizer. Fresh strawberries were treated with this prepared coating solution and stored at a temperature of 0 °C and a relative humidity of 84.8%. The results showed that the treated strawberries were better than the control group in terms of water loss rate, hardness and spoilage rate.
3.Animal and vegetable gum edible film
In the development and application of animal and vegetable gum edible films, Japan has always been at the forefront of the world. This kind of edible film is based on animal glue (such as bone glue and shellac), vegetable glue (such as glucomannan, keratin, pectin, sodium alginate, etc.), glycerol, polyol, sorbate, etc. As a plasticizer, it is made into an edible film.
It has the characteristics of good transparency, high strength, printing, heat sealing, gas barrier and water and moisture resistance. It has been used in the packaging of food such as condiments, sweeteners, soups and oils, and can also be used for freezing. The coating of food, candy and preserved fruit, etc., to prevent adhesion.
The collagen film developed by American "Natick" is made of animal protein collagen. The film has high strength, good water resistance and gas barrier properties, and can be used to package meat food to maintain its flavor.
Polysaccharide-based biofilms have a wide range of applications in the field of medicine. For example, membranes made from regenerated cellulose can be used for hemodialysis, plasma separation, and virus removal; chitin-based membranes can be used as artificial skin or surgical threads. , for wound healing or hemostasis, the advantage is that chitin can be degraded and absorbed by the body and can promote wound healing.
4.Chitin and Chitosan Edible Films
Chitin and chitosan have good film-forming properties and biodegradability, and are very suitable for the manufacture of edible packaging materials. Caner et al. studied the effect of different kinds of acids (acetic acid, formic acid, lactic acid, propionic acid) on the properties of chitosan films, and found that lactic acid chitosan films had good oxygen barrier, moisture barrier and extensibility.
Brandenburg A H et al. added chitin and chitosan to an aqueous solution of starch substances, mixed them to make a film, and treated the film with alkali after drying to obtain a composite film of starch + chitin + chitosan, which was resistant to oil. , Insoluble in water, high tensile strength, can be used for packaging solid, semi-solid or liquid food.
Kim Y J et al. used corn starch as the base material, added chitin and chitosan respectively, and then added a certain amount of plasticizer and tackifier to process the composite packaging paper, which is mainly characterized by high tensile strength. Strength and elongation, and strong water resistance, even if immersed in boiling water for 10min, its performance has little change.
