Use of food grade hops extracts for the development of novel food ingredients

In food productions, the use of plant extracts represents a useful strategy to replace the use of additives or ingredients with functional properties and technological functionalities, and to satisfy the demand of the stakeholders and consumers for innovative, high quality, healthy, clean labels and sustainable food products. In this frame, hops cones, inflorescences of the female plant of Humulus lupulus L., besides their main use as flavouring, bittering and stabilizing ingredients for the beer industry, have attracted the attention of researchers and of food industries for the high content in secondary metabolites with biological activity, i.e. resins, essential oils, and polyphenols (Moir et al. 2018). In particular, hops polyphenols, which depending on the variety, harvest time and year of production can represent also up to 14 % of the hops dry matter (Sanz et al., 2019; Inui, Okumura, Matsui, Hosoya, & Kumazawa, 2017), have been shown to exert antioxidant activity, and anticarcinogenic, antimicrobial, anti- inflammatory, estrogenic and neuroprotective effects (Gerh ̈auser, 2005; Bocquet et al., 2018). However, hops polyphenols, in order to be recovered from the cones, must be extracted by liquid extraction processes and the direct use of liquid extracts in food formulations can find very limited applications. Furthermore, polyphenols are compounds sensitive to environmental stresses, and exposure to high temperatures, oxygen, water, and light during processing, storage, and transport can determine the loss of their nutritional value, bioavailability, solubility, and functionality (Vinceković et al., 2017). Lastly, many of these molecules have a very astringent and bitter taste, which hinders their use in food products. In order to overcome these drawbacks and to produce a powdered ingredient starting from food-grade extracts, microencapsulation by desolvation can be an effective technique. In particular, freeze-drying encapsulation, due to the low process temperature, can be particularly suitable for entrapment and protection of sensitive bioactive compounds such as polyphenols within a carrier material(Moir et al. 2018). However, the encapsulation efficiency and the technological functionality of the encapsulated powders are strictly dependent on the type of carrier and the choice of the wall material is the main step to produce efficiently encapsulated powders. Based on the above, the aim of this thesis has been to develop a powdered functional food ingredient using a food-grade hops extract. To this purpose, freeze-drying was used as encapsulation technology, and the effect of two different carriers, i.e. maltodextrin and arabic gum, used both in single and in combination, on the functional properties and technological functionality of the resulting powders was tested. These coating materials were in particular selected since are among the most common materials used as carriers for the encapsulation and protection of plant extracts bioactive compounds (Pudziuvelyte et al., 2020).