Functional properties of powders produced from either or not fermented mealworm (Tenebrio molitor) paste

Abstract

25The aim of this study was to determine the effect of fermentation of mealworms (Tenebrio 26 molitor) with commercial meat starters cultures on the functional properties of powders 27 produced from the larvae. Full fat and defatted powder samples were prepared from non-28 fermented and fermented mealworm pastes. Then the crude protein, crude fat and dry matter 29 contents, pH, bulk density, colour, water and oil binding capacity, foaming capacity and 30 stability, emulsion capacity and stability, protein solubility, quantity of free amino groups and 31 protein composition of the powders were evaluated. Regardless of the starter culture used, 32 fermentation significantly (p < 0.05) reduced the crude and soluble protein content of the non-33 defatted mealworm powders and in general impaired their water and oil binding, foaming-and 34 emulsifying properties. Defatting of the powders improved most functional properties studied, 35 except the protein solubility, water binding capacity, foaming capacity and emulsion stability. 36The o-phthaldialdehyd assay revealed that the amount of free amino groups increased during 37 fermentation, which may be attributed to proteolysis of mealworm proteins by the starters. 38Sodium dodecyl sulfate polyacrylamide gel electrophoresis demonstrated that the soluble 39 proteins of fermented powders were composed of molecules of lower molecular mass compared 40 to non-fermented powders. As the molecular sizes of the soluble proteins decreased, it is clear 41 that also the protein structure was modified by the fermentation process, which in turn led to 42 changes in functional properties. It was concluded that fermentation of mealworms in general 43 does not contribute to the functional properties studied in this work. Nevertheless, the results 44 confirmed that the properties of non-fermented powders are comparable to other food protein 45 sources.46 Key words 47 In particular, mealworms (Tenebrio molitor) are gaining attention as alternative protein source 51 due their high protein level, good amino acid profiles and high levels of unsaturated fatty acids, 52 vitamins and minerals (Van Huis, 2016). Various technologies are used for the stabilisation of 53 mealworms and processing them into foods, most of which are based on heat application (oven 54 drying and boiling). It can be interesting, both cost-wise and protein property-wise, to apply 55 processes that do not involve heat. Fermentation is a non-thermal process in which a food matrix 56 is subjected to the action of microorganisms or enzymes so that desirable biochemical changes 57 cause modification to the product (Campbell-Platt, 1987). These modifications may result in 58 modified sensory qualities, improved nutritional value, enhanced preservation and/or increased 59 economic value. Fermentation of mealworm paste has been reported to be feasible with lactic 60 acid starter cultures, as indicated by a rapid pH reduction (De Smet et al., 2019; Borremans et 61 al., 2019). During fermentation, some of the starter cultures tes...