Impact of microfluidization on the microstructure and functional properties of pea hull fibre

Abstract

The goal of the present work was to evaluate the impact of the particle size (D90) of microfluidized pea hull fibre suspensions on the physical microstructure, composition and functional properties (i.e. water retention capacity and rheological behaviour). To that end, fibre suspensions with D90 of 120, 100, 80 and 60 μm were produced. Among them, the suspensions of 100 and 80 μm were produced employing two different processing conditions to evaluate the impact of processing on the microstructure and functionality. Suspensions with smaller particles (D90 ≤ 80 μm) presented a thermal stable, pseudoplastic, thixotropic and viscoelastic behaviour varying their elastic modulus in the linear viscoelastic region from 19 to 89 Pa for suspensions with D90 of 80 and 60 μm. By decreasing the D90, it was observed a continuous defibrillation of aggregates of cellulosic macrofibrils, into macrofibrils and microfibrils. Consequently, the number of particles and their interactions by electrostatic and friction forces increased. Alcohol insoluble substances, released from the hemicellulosic and pectic networks, were only detected for the suspensions with D90 = 60 μm. In this case, particles presented inter-fibrillar voids that may increase their flexibility and functionality. For a given particle size distribution, the processing conditions had negligible effect on the functionality. In summary, functionality of microfluidized fibre suspensions may be tuned by controlling the release of alcohol insoluble substances and the defibrillation of the cellulosic network, process conditions then can follow energetic or economic criteria.