Edible Film
Characterization of the Physical and Mechanical Properties of Edible Film Made from B Type Gelatin with the Addition of Glycerol as a Plasticizer.
Edible film is a thin layer made from edible ingredients that used in food components as a barrier for moisture, oxygen, carbon dioxide, flavor, lipid, etc, and or as carrier of food material and additives, and or as to increase food handling. Edible film with good mechanical characteristics can replace the use of synthetic film packaging (Krochta and Johnston, 1997). By its components, edible film can be grouped into three categories, which are hydrocolloid film, lipid film and composite film. Hydrocolloid films are edible films made from gelatin, casein, soy protein, corn protein, oat gluten, starch, alginate, pectin, Arabian gum, and other carbohydrates modifications. Lipid films are edible films made from wax, glycerol and fatty acids. Composite films are edible films made from combinations of hydrocolloids and lipids compounds.
Gelatin compound is a linear polymer of amino acids. In general, this polymer form has a repetition of glycine-prolyne-prolyne or glycine-prolyne-hydroxyprolyne. The main sources used for gelatin production are pigskins, calfskins, lambskins and bones. By its process, there are two types of gelatins which are A type and B type. A type gelatins are gelatins obtained from acid treatments such as pig skins. B type gelatins are gelatins obtained from alkali treatments such as calf skins and bones. Gelatins are edible to consumed, can form some kind of films during the drying process and dissolves in warm temperature of water. Until now, demand of gelatin in Indonesia was fulfilled by importing it from Europe and America. But mostly raw material to produce gelatin came from pig’s bones and skins. This is a problem for majority Indonesian citizen which were Moslems to use these gelatin, especially in food industry. Gelatin which yielded from by product of the hide splitting process of bovine skins in the tanning industry can replaced the use of the imported gelatin.
Glycerol is a plasticizer categorized in polyol compounds, which has three hydroxyl groups in one molecule (trivalent alcohol). The functions of glycerol are as water absorbents, crystal formation agents and plasticizers. Plasticizers are low molecular weight substances that are fuse into the polymer matrix of protein and polysaccharide to increase the flexibility of film and the ability of forming a film.
The objective of this research was to know about characterization of the physical and mechanical properties of edible film made from type B gelatin with the addition of glycerol as a plasticizer. The characteristics tested were film thickness, tensile strength (TS), water vapor transmission rate (WVTR) and oxygen transmission rate (O2TR).
Refers to the pre-research, films with the combination of 5, 7.5 and 10% gelatin with 5% glycerol formed edible films that have visual characteristics needed, such as easy to remove from the mold, not easy to brittle, not easy to rip and not easy to perforate. These visual characteristics need to be considered because they will affect the results of mechanical and physical characteristics test.
The thickness of edible films yielded in this research valued between 122.46 mm until 252.80 mm. Tensile strength test valued between 20.14 kgf/cm2 to 44.40 kgf/cm2. Elongation test valued between 251% until 348.31% while water vapor transmission rate value ranged between 724,79 g/m2/24 hours to 1.390,45 g/m2/24 hours and value of the oxygen transmission rate were zero for every films tested.
The alterations of gelatin concentration affect significantly to the value of thickness, tensile strength and elongation, but they will not affect the value of water vapor and oxygen transmission rate. The increasing of gelatin concentration would increase the thickness, tensile strength, elongation and water vapor value.
