In vitro protein digestibility and mineral accessibility of edible filamentous Fungi cultivated in oat flour

Abstract

Edible filamentous fungi, a source of mycoprotein, are one of the sustainable alternative protein. This study compares protein digestibility (DH%) and amino acid and mineral accessibility in Rhizopus oligosporus cultivated in oat flour (OatRO) or glucose media (GluRO) by using the INFOGEST in vitro digestion protocol. Fungal total amino acids was higher in GluRO (39.0 ± 1.1 % dw) than OatRO (21.8 ± 1.3 % dw) which was also the case for calcium and magnesium content. After completed gastrointestinal digestion, there were no significant differences between GluRO and OatRO regarding DH% (27.21 ± 10.4 % and 29.4 ± 0.5 %), however, GluRO provided significantly higher amino acid accessibility compared to OatRO (64.3 ± 1.6 % and 55.1 ± 3.1 %). Mineral accessibility of GluRO was for Ca: 37.9 ± 1.8 %, Zn: 9.3 ± 0.4 %, Fe: 38.2 ± 1.9 %, Mg: 66.5 ± 1.4 % and Cu: 24.7 ± 1.3 % and for OatRO; Ca: −40.2 ± 2.4 %, Zn: −4.13 ± 0.15 %, Fe:14.6 ± 1.6 %, Mg: 74.5 ± 3.1 %, and Cu: 55.95 ± 0.8 %. Despite the low phytic acid content, OatRO thus showed antinutrient properties with respect to calcium, and zinc, suggesting that oat-derived fungi had antinutrients other than phytic acid. This study hereby revealed that the cultivation substrate affect amino acid and mineral accessibility of filamentous fungi and calls for deeper evaluations of antinutrients in oat-derived fungi.