| This work was financially supported by Grant from Hi-Tech Research and Development Program of China (Grant No. 2008AA10Z308) and International Corporation Project of Jilin Provincial Science & Technology Department Development Program (Grant No. 20060717). The thesis mainly studied the edible packaging material for flavoring powder and soy powder.Edible film is defined as a free standing thin layer of edible material which can be used as a wrapper for foods. It has many advantages over the conventional non-edible wrapper, including (1) it is biodegradable and can be consumed with the packaged product, (2) it can function as a protective shell to preserve the quality of the packaged food and prolong its shelf-life, and (3) it can be a carrier for additives to enhance the sensory and nutritional properties of the food. Edible film, by regulating transfer of moisture and oxygen in food systems, can increase food shelf-life and improve quality. Edible film can also decrease amounts of synthetic packaging materials needed to preserve and protect foods, as well as improve packaging recyclability by reducing the need for laminates.Edible films from soy proteins isolate (SPI) have been investigated extensively in recent years and new products are continuously being developed. SPI is nutritional and highly functional protein and gives transparent, bland and flexible films with very good resistance to oxygen, aroma and lipid transfer at low humilities. However, the hydrophilic nature of proteins induces interactions with water, weakening resistance to moisture transfer.A more interesting approach to improve protein films'properties is to combine with other materials, such as starch and lipids. However, limited information is available on the adding vegetable fiber to protein matrix, and on their characteristic. There are a lot of fibers in fruits/vegetables and the long-chain carbohydrates can provide the structural matrix to form films and improve the films'mechanical and barrier properties. The usage of fruits and vegetables fibers allows the use of off-grade produce. Another advantage is that fruits and vegetables could be processed and held in the stable fiber form for many months.The major goal of this project is to prepare effective composite films for food products and investigate the cross linking interactions between enhancing component and film matrix. Soy protein isolate based edible film as matrix materials and Chinese cabbage fiber as reinforcing material have been prepared using the casting techniques. There was a significant improvement in mechanical properties including tensile strength (TS) and elongation (E), as well as the barrier properties including oxygen permeability (OP) and water vapor permeability (WVP) with the addition of Chinese cabbage fiber to the SPI film This is encouraging result in natural/bio fiber reinforced soy based edible composite films which strengthens the belief to developing natural fiber reinforced edible composite films for various applications.In the first study, the chemical components and structure properties of Chinese cabbage and cabbage fiber were investigated, such as the content of cellulose, hemicelluloses, and lignin, and the length and breath of the fibers. The fiber morphology of Chinese cabbage was studied using microscopy and SEM. The Chinese cabbage fibers are long and thin. The results show that the Chinese cabbage fiber is a suitable raw material to make food packaging material.In the second study, the morphology, structure and crystal performance of the original and treated Chinese cabbage fibers sample were characterized by microscopy, SEM, and XRD. The result shows that the ultrasonic decreases the crystallinity of cellulose , destroying the intermolecular hydrogen bonding effectively. The surface appearance of cellulose also changes after ultrasonic treatment. The mechanism of activation of ultrasonic was discussed. The effect of the treatment time, the power of ultrasonic and the mass fraction of the slurry on the morphology, length and width of Chinese cabbage fibers were investigated. The results show that the fibrillation of Chinese cabbage fibers occurs. With the treatment time and power increase, the length, the width of fibers and the crystallization reduce because the ultrasonic cavitation increases. At 120W and 20min, the fiber length is 0.83mm, the fiber width is 9.04μm, and the ratio of length to width is 92. The appropriate mass fraction of the slurry is 2%. The extent of structure changes increase and more S2 layer are exposed and fibrillated as the treatment time and power increase.In the third study, the treatment methods of the fibers to improve the interaction between the fibers and SPI were investigated. The pretreatment by ultrasonic results in fibrillation and conduces to the cross linking with SPI and the improvement in mechanical properties. SPI-based composites with different fiber mass fractions were prepared in this study. TS increases and E decreases as mass fraction of fiber increases. The TS of film containing fiber reaches a maximum at 2% fiber mass fraction. The E value for films containing fiber varies inversely with TS. SEM shows good dispersion and adhesion between fiber and matrix indicates that fiber surface treatment and property mass fraction are needed for composite films.Moisture sorption characteristics of the SPI and SPI-fiber composite films at 20℃were studied for water activities ranging from 0.10～0.90. The sigmoid-shape adsorption isotherm curves are typical of high protein content material and are adequately described. SPI film is found to be very hydrophilic. Equilibrium moisture content of film increases sharply with an increase in RH from 76% to 94%.Moisture adsorption and sorption isotherm data were mathematically fitted to the Brunauer–Emmett–Teller (B.E.T) or Guggenheim–Anderson–DeBoer (G.A.B) sorption isotherm models, respectively. High r2 values and low RMSE values confirm that both equations are good models for experimental data. Isotherms for the films containing fibers indicate a similar trend. By increasing the mass fraction of fibers in SPI films, the equilibrium moisture content decreases. A plasticizing effect of water related to rapid changes in the functional properties is mainly noted at the highest aw and explained by the disruptive water-polymer hydrogen bonding theory.Water absorption tests show that the moisture absorption rates of composites are lower than SPI matrix material. An obviously decreases in TS and increases in E are observed after water absorption.In the fourth study, the fiber incorporation and interpretation of temperature and relative humidity effects on permeability were discussed. OP and WVP decrease as mass fraction of fiber increases. OP decreases from 1.87×10-16cm3·m-2·s-1·Pa-1 to 0.79×10-16cm3·m-2·s-1·Pa-1 and WVP decreases from 13.6×10-14 g·cm·cm-2·s-1·Pa-1 to 8.4×10-14 g·cm·cm-2·s-1·Pa-1 as the fiber mass fraction increases from zero to 2%.The Arrhenius model was used to fit the barrier properties against oxygen and water vapor of films. For the same fiber mass fraction, the barrier properties of film decrease with relatively higher temperature or relative humidity. The tortuous network structure found in films containing fiber may have contributed to the improved moisture barrier properties of composite films.The crystal performance, surface morphologies, and IR analysis of composite films showed that chemical bond is formed between SPI and cabbage fibers. Therefore could enhance the films physical strength and barrier properties. In the last study, the heat-sealing properties of both SPI films and SPI-fiber composite films were investigated. The heat sealing mechanism and characteristic were discussed as well as the internal relation between heat sealing temperature, pressure and time, the effects of film thickness and water content on heat-seal strength.The heat-seal strength of the SPI-2%Fib films reach a maximum point, which achieving 6.64N/15mm, the heat-seal temperature 150℃, heat-seal time 2.5s, heat-seal pressure 0.25MPa. Although the heat-seal strength of composite is still less than that of polypropylene, it could be used in the inner package material rightly.The experiments and conclusions of edible film are valuable to pilot scale experiences and industrialization. The application of vegetable fiber composite with SPI can open a widely direction on edible film study, and enrich the theoretical development in edible material technique. These results show the potential for composite films to food packaging.
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