PRODUCTION OF BIODEGRADABLE PLASTIC FILMS FROM CASSAVA STARCH USED IN FOOD PACKAGING, USING VARIOUS ADDITIVES AND PLASTICIZERS.  A RESEARCH PROJECT MATERIAL ON BIOCHEMISTRY

PRODUCTION OF BIODEGRADABLE PLASTIC FILMS FROM CASSAVA STARCH USED IN FOOD PACKAGING, USING VARIOUS ADDITIVES AND PLASTICIZERS.  A RESEARCH PROJECT MATERIAL ON BIOCHEMISTRY

1.1   Background study

   Packagingvusing plasticvmaterialsvhas rapidly increasedvin recent times. Its vusevcovers a wide area of applicationvfromvautomobile parts, food, drinks, water, snacks, cloths, fresh and sea foods, vfarm products, vmedicals and pharmaceuticals, to mention but a few. The use of such bombasticvamount of schematicvplastics and itsvadvantage overvother packaging materialsvis due tovits diversevandvadvancevpropertiesvofvlongevity.Thevproperties include resistance tovchemicalvreaction, vthermal strength, mechanical and its tensile strength, vespeciallyvenzymaticvreactions (Ezeoha and Ezenwanne, 2013.).

For example it willvtake avveryvlongvtimevsay avhundredvyears to degradevjustva piece of plastic film (polyethene) used to package snacks (gala) at standard environmental conditions. vBasically, two challenges have been cited with the of conventional polyethene usevits  dependence  on vpetroleum  and  the  problem vof  waste  disposal.  Most  of  today’s  conventionalvsynthetic  polymers vare  producedvfromvpetrochemicals  that vare  not  biodegradable.  Thesevstable vpolymers  are  a  significant vsourcevof venvironmental  pollution, vharming vorganic  naturevwhen vthey  are  dispersedvin  thevenvironment, changes thevcarbon dioxide cycle, problemvassociatedvwith increasedvtoxic emission. The sources of synthetic polymersvsuch as fossilvfuel and gas arevnow stimulated by environmental concerns. Scientists arevresearchingvdifferentvmethods ofvimprovingvplastics thatvcanvbevusedvmorevefficientlyvsuchvthat they could be recycled, vreused and to possiblyvdegradevafter use.

Alternationvisvtowardsvgreenervagriculturalvsources,   vwhich valsovwouldvlead   vto    the    reduction of CO₂emissions (Narayan, 2001). According to the Biodegradable    ProductsvInstitutev (BPI), avbiodegradable plastics isvone in which degradation    results from    the vactionvofvnaturallyvoccurring   vmicro-organismsvsuch as bacteria, vfungi or algae. Degradablevplastics are classified byvAmericanvSociety forvTesting and Materials    (ASTM) into four these are:-

(1) Photodegradablevplastics: Degradation of the plastic results from natural daylight.

(2) Oxidativevdegradable plastics: A degradation of plastics as a result of oxidation.

(3) hydrolytically degradable plastics: – The degradability resultsvfromvhydrolysis, vand

(4) BiodegradablevPlastics: – Degradablevplastics invwhich there isvbreakdown of long chain polymervmoleculevinto smaller or shorter lengths. It undergoes oxidationvwhich is triggered by heat, ultraviolent light (UVlight), and mechanical stress. Itvoccurs in thevpresencevof moisture and actions from naturallyvoccurringvmicroorganismsvsuch asvbacterial, fungi and algae. (ASTM Standards, 1998)

Thevvariousvdegradablevplastics definitions classified above offers the onlyvproducts whichvarevnaturallyvdegradable. Starch isvbeenvdiscoveredvamongst all biopolymers as a high potentialvmaterial for biodegrablevfilms. Starchvconsists of two types of polysaccharides, amylose and amylopectinvdepending on the sucrose (10-20%) amylase and (80-90%) amylopectin. The hydrophlicity ofvstarch canvbe used tovincrease the biodegrability of starch-basedvplastics. Amylosevis avlinearvmolecule with a fewvbranches, whereasvamylopectinvis avhighlyvbranchedvmolecule. Therefore, vamylosevcontentvis an importantvfactor to biodegrable plastic filmvstrength. Branchedvstructure of amylopectin generallyvleads to filmvwith lowvmechanical properties. To improve thevflexibilityvof plastics, plasticizers arevadded tovreduce internalvhydrogen bondvbetweenvpolymer chainsvwhile increasing molecular space. The mostvcommonly used starchvplasticizers are polyols, sorbitol and glycerol. Thevkey emphasisvin biodegrability is thatvbiopolymer materialsvbreakdownvintovsmaller compounds, either chemically or byvorganisms sooner than synthetic plastics (Bastioli, 2005.). Biodegradablevpackagingvmaterials are materials that degrades back tovthe earth surfacevharmlessly when disposed. This help largely in reducingvthe amount of packaging materialsvthat goes back into landfills andvfurthermore, saves energy, as the biodegrable route requires little or novexternal source of energy its endothermic.

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PRODUCTION OF BIODEGRADABLE PLASTIC FILMS FROM CASSAVA STARCH USED IN FOOD PACKAGING, USING VARIOUS ADDITIVES AND PLASTICIZERS.  A RESEARCH PROJECT MATERIAL ON BIOCHEMISTRY