Foaming, emulsifying and rheological properties of extracts from a co-product of the Quorn fermentation process

Abstract

This study assessed the functional profile (foaming, emulsifying and rheological properties), proteomic and metabolomic composition of a naturally foaming and currently unexploited co-product (centrate) from the Quorn fermentation process. Due to the low environmental footprint of this process the centrate is a potential source of sustainable functional ingredients for the food industry. A range of fractions were isolated from the centrate via successive ultrafiltration steps. The retentate 100 (R100) fraction, which was obtained following a 100 kDa ultrafiltration, displayed good foaming, emulsifying and rheological properties. R100 solutions and oil-in-water emulsions displayed high viscosity, while R100 solutions and hydrogels showed high viscoelasticity. R100 foams displayed high stability while oil-in-water R100 emulsions showed small and stable oil droplet size distributions. Large mycelial aggregates were reported in R100 solutions and gels, correlating with their high viscosity and viscoelasticity. A dense mycelial network was observed in R100 foams and contributing to their stability. In parallel tensiometry measurements highlighted the presence of interfacially active molecules in R100 which formed a rigid film stabilising the oil/water interface. A number of functional metabolites and proteins were identified in the centrate, including a cerato-platanin protein, cell membrane constituents (phospholipids, sterols, glycosphingolipids, sphingomyelins), cell wall constituents (chitin, chitosan, proteins), guanine and guanine-based nucleosides and nucleotides. This study highlighted the potential of functional extracts from the Quorn fermentation process as novel ingredients for the preparation of sustainable food products and the complex and specific nature of the centrate's functional profile, with contributions reported for both mycelial structures and interfacially active molecules.

Functional fungal extracts from the Quorn fermentation co-product as novel partial egg white replacers

“…The NCM content of the R100 and agglomerated EW samples were, respectively, 55.2% and 91.8% based on Kjeldahl measurements. The NCM content of the R100 fraction obtained was similar to the one measured in our previous study (56.7%) [13].…”

“…As previously observed [13], large hyphal structures were present in R100 (Fig. 1c), resulting from the aggregation of centrate hyphal debris during their retention on the 100 kDa ultrafiltration membrane.…”

“…Similarly, a high concentration of hyphal aggregates was previously correlated with a decrease of the flow index for fermentation broths of the filamentous fungus Aspergillus terreus [27]. In parallel, our previous study [13] also showed the presence of compounds with known viscosifying properties in the centrate, including cell wall and membrane constituents which concentrated in the R100 fraction as part of the hyphal aggregates and contributed to the viscosity of EW-R100. The viscosifiers reported included chitin and chitosan [28,29], inulin [30], galactan [31], nucleosides and nucleotides (including guanine-based compounds) and their derivatives [32], and sugar alcohols [33].…”

“…We previously reported that a wide range of functional molecules present in centrate and concentrated in the R100 fraction contained nitrogen, including fungal cell membrane and cell wall constituents such as phospholipids, glycosphingolipids, sphingomyelins, chitin, chitosan, and proteins [13]. In that regard, the nitrogen-containing material (NCM) content was measured using the Kjeldahl method [14] to provide a guideline for preparation of standardised sample quantities for functional tests.…”

“…In a previous study [13], we reported that an extract (retentate 100 or R100) obtained via a 100 kDa ultrafiltration of the centrate displayed good foaming stability, emulsifying, and rheological properties (viscosity, viscoelasticity, and gelation). R100 solutions displayed high viscosity, while R100 solutions and hydrogels showed high viscoelasticity.…”