Effect of high‐pressure treatment and cellulase‐mediate hydrolysis on functional, rheological and microstructural properties of garden cress seed residual fibre

Garden cress ( Lepidium sativum ) is valued in Asia and some part of Africa for its seed oil and other parts of plant that retain curative activities and act as a tonic in traditional medicine. The residue left over after the oil and protein extraction is a rich source of bioactive compounds and dietary fibres. The garden cress seed residual fibre (GCRF) contained 99.82% total dietary fibre (TDF), 99.4% insoluble dietary fibre (IDF) and 0.38% soluble dietary fibre (SDF). To improve the industrial applications of the GCRF, an approach was taken to break down the IDF into the SDF following a treatment of enzymatic hydrolysis [cellulase at 2% or 5% (w/w)] and high‐pressure processing (600 MPa/15 min) or a combination of both. The combined treatment had significantly improved the SDF concentration by loosening the surface structure of the GCRF and enhanced the hydration properties. The structural changes were elucidated using the Fourier transform infrared spectroscopy, rheometry and scanning electron microscopy. The Fourier transform infrared spectrum revealed a major shift in the cellulose band because of the combined effect of high‐pressure processing and enzymatic hydrolysis. High‐pressure‐assisted enzymatic hydrolysis was determined the best combination to be ensured almost 18‐fold increase in SDF ratio and to be improved radical scavenging activity more than two times in addition to well‐documented change in viscoelastic properties of the GCRF.