Utilization of a Variety of Additives and Plasticizers to Produce Biodegradable Plastic Films From Cassava Starch for Food Packaging

1.0 Introduction

1.1 Background Of The Study

Packaging using plastic materials has rapidly increased in recent times. Its use covers a wide area of application from automobile parts, food, drinks, water, snacks, cloths, fresh and sea foods, farm products, vmedicals and pharmaceuticals, to mention but a few. The use of such bombastic amount of schematic plastics and its advantage over other packaging materials is due to its diverse and advance properties of longevity. The properties include resistance to chemical reaction, thermal strength, mechanical and its tensile strength, especially enzymatic reactions (Ezeoha and Ezenwanne, 2013.).

For example it will take a very long time say a hundred years to degrade just a piece of plastic film (polyethene) used to package snacks (gala) at standard environmental conditions. Basically, two challenges have been cited with the of conventional polyethene use its dependence on petroleum and the problem of waste disposal. Most of today’s conventional synthetic polymers are produced from petrochemicals that are not biodegradable. These stable polymers are significant source of environmental pollution, harming organic nature when they are dispersed in the environment, changes the carbon dioxide cycle, problem associated with increased toxic emission. The sources of synthetic polymers such as fossil fuel and gas are now stimulated by environmental concerns. Scientists are researching different methods of improving plastics that can be used more efficiently such that they could be recycled, reused and to possibly degrade after use.

Alternation is towards greener agricultural sources, which also would lead to the reduction of CO2 emissions (Narayan, 2001). According to the Biodegradable Products Institute (BPI), a biodegradable plastics is one in which degradation results from the action of naturally occurring micro-organisms such as bacteria, fungi or algae. Degradable plastics are classified by American Society for Testing and Materials (ASTM) into four these are:

1. Photodegradable plastics; Degradation of the plastic results from natural daylight.
2. Oxidative degradable plastics; A degradation of plastics as a result of oxidation.
3. Hydrolytically degradable plastics; The degradability results from hydrolysis, and
4. Biodegradable Plastics: Degradable plastics in which there is breakdown of long chain polymer molecule into smaller or shorter lengths. It undergoes oxidation which is triggered by heat, ultraviolent light (UVlight), and mechanical stress. It occurs in the presence of moisture and actions from naturally occurring microorganisms such as bacterial, fungi and algae (ASTM Standards, 1998)

The various degradable plastics definitions classified above offers the only products which are naturallyvdegradable. Starch is been discovered amongst all biopolymers as a high potential material for biodegrable films. Starchvconsists of two types of polysaccharides, amylose and amylopectin depending on the sucrose (10-20%) amylase and (80-90%) amylopectin. The hydrophlicity of starch can be used to increase the biodegrability of starch-based plastics. Amylose is a linear molecule with a few branches, whereas amylopectin is a highly branched molecule. Therefore, amylose content is an important factor to biodegrable plastic film strength. Branched structure of amylopectin generally leads to film with low mechanical properties.

To improve the flexibility of plastics, plasticizers are added to reduce internal hydrogen bond between polymer chains while increasing molecular space. The most commonly used starch plasticizers are polyols, sorbitol and glycerol. The key emphasis in biodegrability is that biopolymer materials breakdown into smaller compounds, either chemically or by organisms sooner than synthetic plastics (Bastioli, 2005).

Biodegradable packaging materials are materials that degrades back to the earth surface harmlessly when disposed. This help largely in reducing the amount of packaging materials that goes back into landfills and furthermore, saves energy, as the biodegrable route requires little or no external source of energy its endothermic.

Biodegrable polymer sources are from replaceable agricultural feed socks, animal sources, marine food processing industries waste, or microbial sources. In addition to replenshiable raw agricultural ingredients, biodegrable materials breakdown into environmental friendly products such; as carbon dioxide, water and quality compost.

Biodegradation takes place in two-steps: degradation / defragmentation initiated by heat, moisture, or microbial enzymes, and second step — biodegradation — where the shorter carbon chains pass through the cell walls of the microbes and are used as an energy source. Biodegrable plastics are made from cellulose-based starch and has been in existence for decades, with first exhibition of a cellulose-based starch (which initiated the biodegradable plastic industry in 1862).

Cellophane is the most cellulose-based biopolymer. Starch-based biopolymer, which swell and deform when exposed to moisture, include amylose, hydroxyalkanote (PHA), polyhydroxybuterate (PHB), and avcopolymer of PhB and valeric acid (PhB/V)These are made from lactic acid formed from microbial fermentation of starch derivatives, polylactide does not degrade when exposed to moisture (Auras.et al, 2007) PHA, PHB, andvPHB/V are formed by bacterial actions on starch (Krochta, 1997). In addition, biodegrable films can also be produce from chitosan, vwhich is derived from chitin of crustacean and insect exoskeletons. Chitin is a biopolymer similar to cellulose structure.

There are various ways starch can be used for biodegrable polymer production;

1. Starch compost containing more than half by mass of the plasticizers.
2. Biodegrable polymers preparation using the extrusion process of mixtures of granular starch.
3. Composition of starch with other plastics of little quantity of agricultural based material to enhance the biodegrability of conventional synthetic polymer.

Synthetic polymers can also be made partially degradable by blending with biopolymers, incorporating biodegrable components such as starch, or by adding bioactive compounds. The bio compounds are degraded to break the polymer into smaller chains. Bioactive compounds work through diverse mechanisms. For example, they may be mixed with swelling agents to increase the molecular structure of the plastic which upon exposure to moisture allow the bioactive compounds to breakdown the plastics.

1.2 Statement Of The Problem

There is basically, two harms connected to the wide application of synthetic polymer plastics for packaging since its invention in the 1930s: They are total reliance on petrochemical product as its main feed stock and the problemvof waste disposal. Most of today’s conventional synthetic polymers are produced from petrochemicals and are not biodegradable. These stable polymers are significant source of environmental pollution, harmful to organic nature when they are dispersed in the environment.

The raw materials such as fossil fuel and gas could be replaced by greener agricultural sources, which contribute to the reduction of Co2 emissions (Narayan, 2001). Based on the above it becomes of value to produce plastics that are biodegradable,in excess of the past few years synthetic polymer users have been introducing various forms of biodegradable plastics. The alternative raw materials are now from plants products, the main among many others is corn starch.

1.3 Justification Of The Study

Bio plastics were too expensive for consideration of replacement for petroleum based plastics. The lower temperature needed for the production of bio plastics and the more sTable supply of biomass combined with the increasing cost of crude oil make bio plastics prices more competitive with regular plastics.

Starch is inexpensive and abundance in nature, Nigeria being the world largest producer of cassava (FAO, 2009) and being a root crop that can be grown in every part of the nation, Starch is totally biodegradable in a wide range of environments and can be used in the development of biodegrable packaging products for various market uses. Incineration of starch product is a way of recycling, the atmospheric CO2 trapped by starch-producing plant during growth, thus closing the biological carbon cycle (Ceredav et al.).

1.4 Aim and Objectives of the Study

The aim of this research is to produce biodegrable plastic films from cassava starch used in food packaging, using various additives and plasticizers.

This will be achieved via the following objectives.

1. To extract the starch from fresh cassava.
2. To improve the extracted starch with addition of plasticizers and various additives,
3. To determine the biodegrability and tensile strength of the produced biodegradable products and comparing with that of synthetic polyethene.
4. To test the validity of the produced biodegradable film.

1.5 Scope Of The Study

The scope of theses work is strictly limited to:

1. Extraction of starch from cassava.
2. Physical and chemical properties of plasticizers and additives in resumption.
3. Cost estimation.
4. Biodegrability test, and the characterization of the produced film.