Fruit and Vegetable Paper, so named because of its shape and nature similar to paper sheets, is a kind of leisure food made from fresh fruits and vegetables through deep processing, as the name suggests, it can also be used as food packaging materials.
Unlike other fruit and vegetable crisps or dried vegetables, fruit and vegetable paper is thin and soft, can be torn by hand, can also be folded, and can be melted after chewing in the mouth. Fruit and vegetable paper can retain the original flavor of fruits and vegetables, color, moisture content is low (6% to 8%), compared with fresh fruits and vegetables, has a long shelf life, easier storage and transportation and other advantages.
In recent years, fruit and vegetable paper food and edible wrapping paper development and development and related research has been the hot spot of food research at home and abroad, in improving the comprehensive utilization of fruits and vegetables is of great significance.
Fruit and vegetable paper in addition to meet the packaging material of the protection, unit concentration and convenience of the three basic characteristics, but also through the compounding to enrich its nutritional types and content, so that it can be formulated and production process changes to meet the nutritional needs of special populations (such as children, the elderly, soldiers, etc.).
Fruit and vegetable paper can be made from a wide variety of ingredients, including single fruits and vegetables, or a variety of fruits and vegetables can be blended (Table 1).
As the moisture content of the main material of fruits and vegetables are generally more than 90%, the colloidal material content is low, is not conducive to drying after molding, so adhesives are often used as the main auxiliary material added to the processing of raw materials to improve the physical properties of the pulp, thereby increasing the viscosity to facilitate the molding, and at the same time, the addition of adhesives to the gloss of the product, lubrication palatability is regulated.
In order to improve the elasticity and ductility of fruit and vegetable paper as food packaging materials and other characteristics, while also using thickeners. Commonly used thickeners include sodium carboxymethyl cellulose (CMC-Na), ammonium alginate, pectin, soluble starch, corn starch and gelatin.
The total amount of thickener added is generally 0.1% to 5%, add too little will lead to paper is not easy to mold, easy to break; add too much will lead to paper toughness, taste is not crispy, add to combine different fruit and vegetable substrates and different thickener characteristics of the adjustment. For example, purple kale vegetable paper thickener selection of 0.5% soybean isolate protein, 0.5% carrageenan, 0.5% starch, 0.6% pectin compound, played to maintain the bright colors of vegetable paper, molding effect is better; and fungus fruit and vegetable paper thickener selection of 0.3% CMC-Na, 4% corn starch, 0.3% agar compound, to achieve the product flat, easy to uncover the slice, chewing, non-stick teeth Effect.
In addition, adjusting the proportion of chitosan or plant fiber in fruit and vegetable pulp can also improve the performance of fruit and vegetable paper packaging. Zi Mingyang et al. studied the effect of the ratio of chitosan and high straight chain starch in the composite film on the mechanical properties of the composite film, and found that with the increase in the proportion of chitosan, the elongation at break of the composite film gradually increased and reached a maximum at the ratio of the two masses of 1:1, which indicates that chitosan can be used to improve the ductility and flexibility of the composite film of fruits and vegetables.
In addition, ultrasonic treatment also helps to improve the paper properties of fruit and vegetable paper. Jiang Yan et al. found that after 2% of cabbage pulp was treated with 120W ultrasonic waves for 20 min, the degree of fine fibrillation of cabbage fibers increased, and the number of free hydroxyl groups in the fiber molecules increased, which facilitated cross-linking with other macromolecules, formed strong molecular hydrogen bonds, and played the role of providing backbone support for fruit and vegetable paper.