Physical decontamination of lupin (Lupinus angustifolius) protein isolates, seeds and flakes: Effects on microbiological status and micellar protein yield

Abstract

Plant seeds are important food sources. Because of inevitable soil contact seeds harbor a large number of microorganisms, especially spore-forming bacteria who are able to germinate in food products. Micellar lupin (Lupinus angustifolius) protein isolates, suitable as fat replacers in foods, may include these bacteria and therefore represent a risk for consumers. To guarantee safe food, these protein isolates were pasteurized (60–80 °C, 2.5–30 min), leading to a 4-log reduction of the microbial count. Nevertheless spore-forming microorganisms remained. To inactivate these bacteria whole lupin seeds and processed raw materials (dehulled seeds, flakes) were decontaminated before protein extraction by physical methods: Ultraviolet (UVC) radiation (20, 60 min), dry heat (60 min, 110–140 °C) and wet heat (autoclaving: 115 °C, 20 min). Protein yield and decontamination performance were investigated. Autoclaving turned out to be unsuitable (up to 50% decrease of protein yield) whereas dry heat at 110 °C and 120 °C resulted in a significant increase for all raw materials. Best results concerning protein yield and decontamination performance were obtained by a dry heat treatment (130 °C) for dehulled seeds and flakes and by UVC radiation (60 min) for whole seeds, dehulled seeds and full-fat flakes.