Bio-Based Disposable Containers for Food Services

Table 1

Select studies involving enhancement of protein-based adhesives.

Protein type	Enhancement done	References
Soy protein	(i)     Soy proteins modified by 0.5% and 1% sodium dodecyl sulfate and 0.5% and 1% sodium dodecylbenzene sulfonate enhanced the water resistance and tensile strength of soy protein adhesives applied on walnut, cherry, and pine plywood.	[81]
	(ii)   Soy proteins modified by 1 and 3 M urea and 1 M guanidine hydrochloride improved the water resistance and tensile strength of soy protein adhesive applied on walnut, cherry, and pine plywood.	[82]
	(iii) Soy proteins modified with higher hydrophobicities under moderate alkaline conditions (pH of 10.0 at 50°C) and the addition of trypsin enhanced adhesive strengths and water resistance properties.	[83]
	(iv) Urea modified soy proteins resulted to higher water resistance properties compared to adhesives containing alkali-modified and heat-treated proteins when applied to plywood.	[84]
	(v)   Moderate esterification using ethanol yielded the maximum increase in adhesion strengths and water resistance of soy protein adhesives. The optimum esterification condition was found to be 10 hr with no catalyst. This condition increased the dry, wet, and soaked strengths by 20.6%, 61.6%, and 48.1%, respectively.	[85]
	(vi) The use of 20 µM optimum glutaraldehyde concentration as a protein cross-linker enhanced the dry, wet, and soak strengths of soy protein isolate applied to cherry wood.	[86]
	(vii) Soy protein isolate modified with three cationic detergents (hexadecyltrimethyl ammonium bromide, ethylhexadecyldimethyl ammonium bromide, and benzyldimethylhexadecyl ammonium chloride) at a concentration of 2.6 mM improved the dry tensile strength and water resistance of soy protein.	[87]
	(viii) Decreasing the carbohydrate content and extent of Maillard reaction at high temperatures improved the degree of cross-linking and hydrophobicity of soy-based adhesives. The highest bonding strength was observed for soy-based adhesives with a glucose content of 71%.	[88]
	(ix)   The shear strength and water resistance of sorghum lignin and extruded sorghum lignin blended with soy protein improved the shear strength and water resistance of soy protein adhesive.	[89]
Wheat protein (gluten)	(i)     The addition of triacetin to phenolic resins containing wheat protein improved the performance of thermoset wood adhesives.	[90]
	(ii)   Alkaline hydrolysis (pH of 13 with concentrated sodium hydroxide solution) improved the dry and wet bonding strength of wheat protein adhesive by forming smaller peptides after longer treatment times.	[72]
	(iii) The addition of polyamidoamine-epichlorohydrin as cross-linker for wheat gluten proteins dispersed in sodium hydroxide instead of citric acid enhanced the internal bonding strength, reduced thickness swelling, and water absorption capacity of particleboards bonded with wheat protein adhesive.	[91]
	(iv) Thick spent sulfite liquor, an industrial by-product from sulfite pulp mills, combined with wheat flour at an 84 : 16 dry weight ratio and preheated to 94°C prior to application yielded an internal bonding strength higher than the standard requirements for particleboard type P2 (boards for interior fitments for use in dry conditions).	[92]
Cotton protein	(i)     Hexane-extracted cottonseed meal glue yielded comparable shear strength values with commercial casein glue and peanut meal glue.	[93]
	(ii)   Cottonseed protein isolate modified with adipic acid, butyric acid, acetic acid, glutamic acid, and aspartic acid enhanced the adhesive strength and water resistance of cottonseed protein adhesive tested on maple wood veneer.	[94]
	(iii) Cottonseed protein modified with sodium dodecyl sulfate showed improved shear strength and superior retained strength on a hot water test.	[94]
Canola (rapeseed) protein	(i)    Chemical modification with SDS, CaCO3, ZnSO4, and OSA improved the dry and soak strengths of canola proteins adhesives. However, the combined chemical modifications of canola protein using SDS and CaCO3, and SDS and ZnSO4 did not improve the shear strength.	[75]
	(ii)   Canola proteins modified with ammonium persulfate (APS) at optimum conditions (1% w/w APS/protein) followed by nanomaterial exfoliation improved wet and dry adhesion strengths.	[95]
	(iii) Canola protein isolate–poly(glycidyl methacrylate) conjugates synthesized by free radical polymerization showed can be produced with good adhesive strength and water resistance.	[96]
Corn protein (zein)	(i)    Zein-based adhesive modified with 5 wt % FeCl3 aqueous solution (Fe(III)@zein/SDS adhesive) showed high adhesive strength.	[97]
	(ii)   Using acetic acid rather than ethanol as solvent, zein can be cross-linked by glutaraldehyde for improved water resistance and strength. Zein adhesives added with 5% cellulose nanofibrils also enhanced the adhesive bonding strength.	[98]