Techno-functional and rheological characterisation of protein isolates from two Australian lupin species as affected by processing conditions

Lupin, a sustainable non-starchy legume, holds promising potential as a novel plant protein source, yet its protein functionality has been underexplored, particularly in relation to drying and its interaction with starch and fibres. Here, protein from two Australian Lupin species (Lupinus angustifolius ‘Jurien’ and Lupinus albus ‘Murringo’) were extracted at pH 8.0, precipitated at pH 5.0, and subsequently dried via spray or freeze-drying, with or without pasteurisation. Solubility at pH 8.0 was highest in the direct freeze-dried albus and angustifolius isolates, reaching 85% and 88%, respectively, yet processing exerted a discernible influence, leading to reduced solubilities in spray-dried (albus-72% angustifolius-55%) and pasteurised samples (albus-67%, angustifolius-44%). However, this effect was not consistently reflected in foaming and emulsification abilities, or water- and oil-holding capacities. The albus species exhibited superior gelation characteristics compared to angustifolius species. Furthermore, interaction between spray-dried albus isolates, potato starch and two types of fibres showed protein–starch–fibre interactions were dependent on the type of fibres present. In conclusion, varietal disparities, largely attributed to differences in legumin-to-vicilin ratios, had a significant impact on protein functionality, while the processing parameters employed demonstrated limited effects, primarily in terms of solubility and colour.