By: Dr. Dra. Sri Mulijani, MS (Lecturer at the Chemistry Department of IPB and Experts Staff of LPPOM MUI)

Packaging technology is growing rapidly in line with the development of science and human civilization. The industrial revolution which has transformed the human life order towards a more modern life has also changed packaging technology to cover aspects of food protection such as the quality of nutrition, taste, contamination, and causes of food damage. 

Technology also influences marketing aspects, namely maintaining quality, improving appearance, product identification, composition information, and promotion. Today, even though natural packaging is still being used, packaging has developed in the group of synthetic packaging and modern packaging. 

Various types of synthetic packaging materials for food that circulating in the community, such as paper, glass, cans, and plastic have certain advantages and disadvantages so that their use is also based on compatibility with the nature of packaged food. Modern packaging that has been used to package food includes aseptic packaging, packaging with a variety of atmospheres in it, or packaging that is applied with low-temperature storage, both as primary packaging (direct contact with packaged materials), secondary, tertiary, and so on. 

Among these packaging materials, plastic is the most popular packaging material and is very widely used. Scientifically, the definition of plastic is organic macromolecular compounds (polymers) obtained from polymerization, polycondensation, polyaddition or the process of polymerization of molecules of lower molecular weight (monomers) or chemical changes of natural macromolecular compounds. Resistant plastic for freezing (-400C), storage (-200C), sterilization temperature (121oC), microwave temperature (100oC), heat emission (200oC).  

This plastic packaging material has various advantages, that is flexible (can be in the form of product), transparent (invisibility), not easily broken, laminated (can be combined with other packaging materials), non-corrosive and the price is relatively cheap. Furthermore, in addition to having various advantages that are not possessed by other packaging materials, plastic also has disadvantages, namely, not heat resistance, can contaminate products (migration of monomer components), thus containing the safety and health risks of consumers. Plastics include materials that cannot be destroyed quickly and naturally or are commonly called non-biodegradable materials. 

Associated with what is called plastic as packaging material, the plastic used for petroleum-based packaging materials. Various plastic base materials from petroleum such as polyethylene terephthalate (PET), high-density polyethylene (HDPE), polyvinyl chloride (PVC), low-density polyethylene (LDPE), polypropylene (PP), and polystyrene (PS) are packaging plastic components food. Since 1988, the plastic industry has begun to use the identification of resin coding for each type of plastic so that it can help inform consumers of types of recyclable plastics (thermoplastics) and those that cannot be recycled (thermoset).  

Additives and Auxiliary Materials 

In making plastic as a packaging material, several additional ingredients that will help form plastic according to its function are needed. Usually, manufacturers will make formulas (plastic compounds) with added additives that are different to improve performance and shelf life. Helper materials are used in the process of forming plastic (injection molding, extrusion, blow molding, vacuum molding, etc.) as lubricating materials, acid-binding materials, etc. 

Related to the type of thermoplastic, this plastic formula can usually be directly fabricated without any other additives, whereas for non-recyclable thermoset plastics a chemical catalyst is needed in the molding process. This is needed to strengthen the bond (crosslink) between the plastic polymer chain that is formed. 

In addition, some polymer resins or plastic ores such as polymers (polyolefins and rubber) very often contain halogen anions which can cause equipment. This anion must be neutralized by the catcher or Acid Scavenger. Polypropylene and Polyethylene are dominated by transition halogenide metals as catalysts, which are supported on carriers of inorganic materials, including metal chloride.  

During processing, halogen acids are formed due to the influence of heat and friction in the equipment. The acid formed must be removed to prevent polymer degradation or corrosion of the equipment. Usually, metals or stearic salts and/or oxides are added to polymers to prevent harm to the environment, polymers, and equipment. 

Additional ingredients commonly used for plastic formation are:

  1. Functional additives: stabilizers, antistatic agents, flame retardants, plasticizers, lubricants, slip agents, curing agents, foaming agents, biocides, etc. 
  2. Dyes: azo compounds 
  3. Filler: mica, talc, kaolin, clay, calcium carbonate, barium sulfate. 
  4. Strengthening material: glass fiber, carbon fiber. 
  5. Helper in the process: calcium stearate (E470)

Importantly, the additives in the manufacture of these plastics are not chemically bonded to plastic polymers, except for additives for fireproof plastics (usually used for firefighting clothes) will be chemically bonded to plastic polymer chains. Consequently, these additives can migrate into packaged material.

Critical Point of Halal and Thayyib in Making Plastic 

Halal and plasticity of plastic lying in the additional material that is used in the formation of plastic. Processing materials such as silica flour, sand, black carbon, limestone, talc, and synthetic polymers are used to improve the mechanical properties of plastics. Other additives are plasticizers used to strengthen the flexibility, strength, and toughness of the plastic while reducing hardness and stiffness. 

These additives are usually low molecular weight polymer liquids. Plasticizers are usually used in polymers that are brittle and easily cracked so that this plastic can be used as a wrapper. Plasticizers commonly used are phthalate derivatives such as bis (2-Ethylhexyl) phthalate (DEHP) and Bis (nbutyl) Phthalate (DBP). Both are used as plasticizers in making plastic as a wrapper. Phthalate is a chemical that contains 1,2-benzylticarboxylic acid diester (phthalate acid). 

In its function as a plasticizer, phthalate in plastic is not chemically tied to the host polymer, so that the substance can evaporate into the environment. Therefore, phthalate is not only carcinogenic, but it can also cause interference with inhalation, so it does not thayyib.  

The use of these materials has begun to be reduced and instead is a natural material that is able to form a gel so that it can be used as a plasticizer. The natural ingredients of the plasticizer are of course biodegradable, which means they are easily destroyed by bacteria in nature. The use of natural plasticizers is biodegradable, with low toxicity and good compatibility with some plastics, resins, rubber, and elastomers in conventional plastic substitution, such as phthalate and its derivatives. 

This will attract the market along with the increasing trend in the use of plastic throughout the world. Natural plasticizers developed are glycerol, sorbitol and sometimes also gelatin. In addition, plasticizers which are important and very environmentally friendly can be used, namely derivatives of citric acids such as tributyl citrate, acetyl tributyl citrate, triethyl citrate, acetyl triethyl citrate, and tri (2-ethylhexyl) citrate. Other types of plasticizers are polyol derivatives such as glycerol, ethylene glycol (EG), propylene glycol (PG), diethylene glycol (DEG), triethylene glycol (TEG), tetramethylene glycol and polyethylene glycol (PEG). 

Further related to halal plastics, usually in the polypropylene mixed formulation, the metal-fatty acid salts besides functioning to neutralize the catalyst contained in the composition of the polypropylene resin also function as filler dispersants mixed in the composition of the polypropylene resin. The salt used in this mixture is calcium stearate (E470). 

During the mixing process, calcium stearate will surround the talc particles thus forming an aggregate that will make the particles talk well dispersed and not form clots. During the melting process of the polymer, talc and calcium stearate remain solid. Because of this shape, the stearic group will not enter the talk particles but remain on the surface. The stearate group at the surface can also be a compatibilizer between the polymer matrix, namely polypropylene, with talk particles. 

In the last decade, the use of petroleum-based plastics has begun to be reduced so that plastic producers have begun to see opportunities to make biodegradable plastics. Natural ingredients that are able to be used as basic ingredients of plastic are starch flour, gelatin which is a critical point in halal (in the form of cow gelatin, pork, and fish) and also derived from bacteria lactic polyacids (PLA).

Gelatin-based natural and biodegradable plastics are thin, flexible, and transparent biodegradable materials based on biopolymers, for use in food packaging, medicine release, and other applications, especially in the pharmaceutical field. In the formation of strong plastic gelatin, plasticizers are needed to change some functional and physical properties, such as increasing flexibility, moisture sensitivity, and also other functional properties. Some plasticizers used are sorbitol, glycerol, glutarahdehyde, and nanoparticles. Adding plasticizers can improve thermal and mechanical properties and moisture resistance and moisture barrier properties. 

Plastics from cow gelatin added with d-sorbitol (30% by weight) as plasticizers and cross-linked with low amounts of glutaraldehyde (GTA, from 0 to 2% by weight) produce higher quality plastic. Besides that, plastic manufacturers also usually add anti-bacterial substances to certain packaging. The anti-bacterial substances added are silver nitrate in nanosize so that the plastic formed is called active packaging material. 

Now there have been changes in consumer demand and markets for food products, where consumers demand high-quality food products, can be prepared at home, are fresh, more reliable, better than canning, more consistent, uniform quality, and low cost. This causes plastic packaging to be the most appropriate choice because it can meet all consumer demands.

The types of plastic films on the market are very diverse, so it needs good knowledge to be able to determine the right type of plastic packaging for food product packaging. In choosing the right type of packaging, in addition to the consideration of preventing damage to packaged food, there is also a challenge to fabricate plastics in accordance with halal and hygiene. For the ease of selecting halal and quality plastics, there are already many halal-certified plastic products on the market in MUI. (***)

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