Optimization of a thermal process for the production of superabsorbent materials based on a soy protein isolate

• Published in: Industrial crops and products 2018-12, Vol.125, p.573-581
• Main Authors: Álvarez-Castillo, Estefanía, Del Toro, Alejandro, Aguilar, José Manuel, Guerrero, Antonio, Bengoechea, Carlos
• Format: Article
• Language: English
• Subjects: Bioplastic; Crosslinking; Porosity; Soy protein; Superabsorbent; Water uptake
• ISSN: 0926-6690; 1872-633X
• DOI: 10.1016/j.indcrop.2018.09.051

[Display omitted] •Thermal processing conditions play a key role for soy superabsorbent materials.•Swelling and tensile properties may be tailored through adequate thermal processing.•Materials moulded at 70 °C are superabsorbent if stored less than 10 h at 50 °C.•High temperature-moulded materials are not influenced by dehydrothermal treatment. Superabsorbent materials have found several applications in fields related to diapers, hygienic tissues or controlled-release in agriculture. In order to produce more environmentally-friendly materials, some efforts have been focused on grafting copolymerization of acrylic derivatives onto a natural compound (e.g. protein, polysaccharide). This manuscript deals with the production of biodegradable superabsorbent materials produced from a Soy Protein Isolate (SPI), in which their water absorbance capacity is modulated only through the modification of the thermal processing. Thus, SPI was blended with a plasticizer (glycerol), using a 1/1 (w/w) SPI-glycerol ratio, and then injection moulded at different mould temperatures (Tmould). Subsequently, a dehydrothermal (DHT) treatment was carried out, consisting of the storage of bioplastic produced at 50 °C in an oven for a certain period of time (tDHT). The present study demonstrated that thermal conditions (Tmould, tDHT) plays a crucial role in the formation of superabsorbent materials from protein sources like SPI. Mould temperatures as low as 70 °C resulted in materials with a water uptake which defines their superabsorbent character, as long as the tDHT selected is shorter than 10 h. Longer tDHT resulted in a tighter structure with generally higher viscoelastic properties, which was less able to swell and absorb water. A longer moulding stage also lead to a decrease in the water uptake. Thus, thermal processing parameters have been proven to modulate the superabsorbent characteristics of the materials studied, not being necessary any chemical modification of the protein source.