Comparison of the effects of high hydrostatic pressure processing and heat pasteurization on the techno-functional properties of Spirugrass®, a protein-rich microalgae extract

High hydrostatic pressure processing (HPP) is an alternative method for inactivating microorganisms in foods and has less impact on heat-sensitive ingredients than conventional heat pasteurization (HP). Spirugrass®, a heat-sensitive, protein-rich extract and innovative food ingredient from Arthrospira platensis , shows high bacterial contamination (aerobic mesophilic, Enterobacteriaceae, E. coli ). We hypothesized that HPP of Spirugrass® is a sufficient method to reduce its microbial counts while improving color (phycobiliprotein content), protein structural integrity and associated techno-functional properties [solubility, emulsification, foaming capacity (FC), oil- and water-holding capacity (WHC), minimum gelling concentration (MGC), anti-oxidant capacity] compared to HP. To test this, mentioned techno-functional and microbiological parameters of HPP (300 and 600 MPa, 3 min), HP (63°C, 30 min) and an untreated Spirugrass® control were compared. HP resulted in a brown color, with phycobili- and other proteins almost completely denatured and losing their structural integrity, reducing most techno-functional properties. Contrarily, HPP preserved the green color and the proteins remained partially (600 MPa) or almost (300 MPa) intact with slightly reduced solubility and MGC but improved FC and WHC (600 MPa), or without much effect on properties (300 MPa). We conclude that HPP at 600 MPa and HP achieve up to 2.5 Logs reduction in total bacterial counts, but only HPP has a limited impact on the color and techno-functional properties of Spirugrass® as 50% of phycobiliproteins and most proteins’ structural integrity are preserved.