Abstract
Composite materials based on proteins and carbohydrates normally offer improved water solubility, biodegradability, and biocompatibility, which make them attractive for a wide range of applications. Soy protein isolate (SPI) has shown superabsorbent properties that are useful in fields such as agriculture. Alginate salts (ALG) are linear anionic polysaccharides obtained at a low cost from brown algae, displaying a good enough biocompatibility to be considered for medical applications. As alginates are quite hydrophilic, the exchange of ions from guluronic acid present in its molecular structure with divalent cations, particularly Ca2+, may induce its gelation, which would inhibit its solubilization in water. Both biopolymers SPI and ALG were used to produce composites through injection moulding using glycerol (Gly) as a plasticizer. Different biopolymer/plasticizer ratios were employed, and the SPI/ALG ratio within the biopolymer fraction was also varied. Furthermore, composites were immersed in different CaCl2 solutions to inhibit the amount of soluble matter loss and to enhance the mechanical properties of the resulting porous matrices. The main goal of the present work was the development and characterization of green porous matrices with inhibited solubility thanks to the gelation of alginate.
Highlights
It is increasingly frequent to find biopolymers as an integral part of new materials [1,2,3,4], which can be widely used in different applications where they replace traditional plastics
This decrease could be related to the differences between the density of the Soy protein isolate (SPI) and Alginate salts (ALG) flours used, which means that for the same weight of the sample (i.e., 65 g), the volume filled in the mixer is lower because the amount of ALG is higher [38]
The behavior of the blends indicates that a replacement of soy protein with alginate leads to an enhancement of the mixing process as the plasticization energy decreases, which was previously attributed to an enhancement of the plasticizing efficiency
Summary
It is increasingly frequent to find biopolymers as an integral part of new materials [1,2,3,4], which can be widely used in different applications where they replace traditional plastics. A biopolymer that is extensively used as a raw material in biodegradable materials is soy protein isolate, which is obtained as a by-product from the soy oil industry This protein is formed by two main globular fractions with different structures and molecular weights, namely glycinin-11S and βconglycinin-7S proteins. In order to promote a circular economy, this by-product could be reused for different purposes, including the formulation of biodegradable materials. In this sense, several studies have confirmed the feasibility of producing superabsorbent materials [5,6,7] that could potentially be used in different fields, such as horticulture, pharmaceutical, personal care, and textile fields [8,9,10]. A three dimensional swollen structure forms simultaneously during the water absorption, resulting in porous matrices when dried, which could be reused again as superabsorbent materials [10]
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