Comparing functional properties of concentrated protein isolates with freeze-dried protein isolates from lupin seeds

Fractionation processes are used to increase the potential applications of plant materials. Unfortunately, those processes are energy-intensive and require large amounts of water and chemicals. A route to reduce the energy consumption is to replace the drying step by ultrafiltration. The latter is possible, because in many final applications, water is used to make the products. However, the dried product is still the industrial standard and altering the final steps in fractionation requires sound understanding of the differences in functional properties and the underlying reasons. This study compared the technical functionality of freeze-dried lupin protein isolates (LPIs) with concentrated 'wet' LPIs, both obtained through aqueous fractionation. It was demonstrated that freeze-drying lead to the formation of relatively large protein particles that are quite stable upon thermal treatment. The concentrated LPI dispersions were composed of smaller protein aggregates. In terms of functionality both protein isolates show similar behaviour, though some differences are observed. Additional processing of concentrated LPI however can make the properties more comparable to the freeze-dried LPI, making them suitable for most applications in which now dried protein isolates are used. In addition, the concentrated protein isolate provides additional functionality, which might offer new product opportunities. (C) 2015 Elsevier Ltd. All rights reserved.