Assessing the properties of protein foams as an alternative absorbent core layer in disposable sanitary pads†

Developing biodegradable menstrual products using co-stream proteins as a material alternative to fossil counterparts presents a significant environmental advantage across their entire value chain. The intrinsic properties of wheat gluten foams derived from wheat starch production have been validated with respect to their potential as absorbent core layers in disposable sanitary pads, which is relevant to the rising demand for eco-friendly disposable sanitary pad alternatives. Here, we report the fabrication of a gluten-porous absorbent layer and evaluate its liquid absorption properties and mechanical stability under relevant operating conditions compared to a commercial absorbent foam layer used in sanitary pads. The porosity was achieved using sodium and ammonium bicarbonate, which are non-toxic and food-grade blowing agents, and the materials were shaped/foamed using a conventional oven. The use of sodium bicarbonate resulted in a more homogeneous and lower-density foam with smaller pores than with ammonium bicarbonate. The developed prototypes show comparable mechanical properties under compression to foams used in commercial pads, retaining up to 95% of their initial shape after 3 h of compression. Moreover, the foamed structure permitted a liquid uptake of saline and blood of 4.5 g g⁻¹ and 1 g g⁻¹, respectively, with the possibility to absorb up to 1.5 g g⁻¹ of saline under load. The results indicate that the choice of blowing agent has a large impact on the performance of gluten pads under constant pressure. It is thereby demonstrated here that protein-based foams have adequate mechanical and absorption properties that make them interesting for their future use as the absorbent layer in sanitary products following a circular economy model.