Combination of Propylene Glycol Alginate and Lauric Acid on Water Retention and Mechanical Properties of Soy Protein Isolate-Based Films

Abstract

The water sorption, water barrier properties and mechanical behavior of soy protein isolate (SPI) based films combined with propylene glycol alginate (PGA) and lauric acid (La) via a direct-or co-dried blending process were investigated. Higher water retention ability and a single glass transition temperature (Tg) were found when the PGA was added to form different ternary co-dried blending films by a co-drying process, indicating their compatibility. Tg was reduced in the case of higher relative humidity and incorporation of La. The response surface methodology (RSM) indicated that the effect of La content was highly significant (p < 0.05) for the water retention ability and mechanical properties, and the proposed models calculated for the tensile strength and elongation at break showed a good fit. The results revealed the importance of the interactions among lipids, protein and polysaccharide in composite films which also provided evidence for modeling film behavior.Keywords: co-dried blending film, glass transition temperature, water retention ability, mechanical properties, response surface methodology IntroductionConsiderable research interest in edible films derived from renewable sources (proteins, carbohydrates and lipids) or their combinations has been developed over the past two decades. Such films made from whey and soy proteins, corn zein, wheat gluten, and gelatin may be used as food coatings or stand-alone film wraps to retard unwanted mass transfer in food products. [1][2][3][4] They may also improve the recyclability of some packaging applications by reducing the need for complicated multilayer structures.Proteins and polysaccharides or their complexes are good film-forming materials, but the improvement of their water-barrier properties requires the extra addition of lipids, which can result in many types of new multicomponent edible films. In multi-component edible films, the addition of a lipid component will result in a significant increase in the film water-barrier properties, and affect the mechanical and oxygen-barrier properties. 5 Generally speaking, the atmospheric relative humidity surrounding the films influence lipid component less than hydrophilic component. The equilibrium moisture content has a much more obvious effect on the plasticization function, the barrier and mechanical performance of the hydrophilic film system. 6 Film equilibrium moisture is closely related to the environmental relative humidity (RH). The hydrophilic properties of protein and polysaccharides will result in the sensitivity of protein/polysaccharide-based edible films to environmental RH, and thus their film-forming performance varies. 6,7 However, different film-forming processes, film matrices, and addition proportions result in different effects on the properties of edible films, especially their mechanical and barrier properties. [8][9][10] Gas and water permeability of composite films consisting of protein-polysaccharide (soluble starch, modified starch, or chitosan), and plasticizer (water, sugars, or...

Recent Progress in Robust Regenerated Soy Protein Film

“…Protein molecules have amino and carboxyl groups that interact with glycerol, which weakens the hydrogen bonding between them and within them, enhancing the molecular chain mobility and improving SP film flexibility. [ 56 ] Other polyhydric alcohols, such as ethylene glycol, [ 57 ] propylene glycol, [ 58 ] sorbitol, [ 59 ] and polyethylene glycol [ 60 ] are also widely used as plasticizers for preparing SP film. [ 50 ] A nano‐scale study of glycerol‐plasticized SP film microstructure and molecular interactions was conducted ( Figure ) and discovered that there are two micro‐domain regions with different affinities in the plasticized SP film, leading to two T g .…”