## 1 Introduction  
Innovative functional hydrogels based on gluten-free matrices could be formulated from both the agricultural and marine environments. The main non-gluten agricultural sources for obtaining natural starches are cereals, roots, tubers and legumes. Starches, considered as one of the most suitable biopolymers, are usually employed in the food industry to make a wide array of pastry products, such as cookies, breads, puddings, cakes and pasta, among others [1]. Potato starch, considered a low-cost source that is easy to obtain and has multiple properties, is used as a gelling agent, stabilizer, emulsifier, thickener and adhesive nowadays, thus contributing to the improvement of the textural properties in food formulations [2]. Starch, in the presence of water and with the adequate supply of energy, undergoes a gelatinization process in which its crystalline structure is broken, passing from insoluble granules to obtaining a solution of its molecules, originating viscous pastes. During this process, the amylose molecules diffuse into the water and form a gel while the amylopectin loses its crystalline order [3]. It is this order-disorder transition that starch polymers undergo when subjected to heating which impacts the processing, quality and stability of starch-based products [1]. Other gelling agents and stabilizers that could be suitable for gluten intolerance come from algae polysaccharides such as alginates, carrageenanates or agars. In this study, the red marine macroalga _Mastocarpus stellatus_, also known as false Irish moss or false carrageenan moss, was employed as a rich source of hybrid carrageenanans. These natural polymers are widely used in many industries from different fields due to their chemical and physical characteristics, giving them versatility in their applications [4; 5]. Carrageenan can be used to give volume, texture and viscosity or as a powerful gelling agent [6] due to its singular properties of biodegradability and durability, which are widely used in the food industry to provide consistency to milk products or ice creams [7]. In particular, hybrid carrageenans extracted from the proposed alga are a group of long-chain polymers consisting of blocks of \(k\)- and \(t\)-carrageenan disaccharides placed along a chain, sharing with minor amounts of non-gelling disaccharide blocks [8] that are characterized by the formation of viscous gels when dispersed in water, due to the fact that they have a large number of hydroxyl groups. This increases their affinity for water molecules, providing a high flexibility similar to the natural tissue and the ability to modify the system's rheology [9]. The combinations of both \(k\)- and \(t\)-carrageenans are fundamental for creating gels [7]. Kappa-type carrageenans provide hard, strong and brittle gels, whereas iota-type carrageenans are soft and weak; however, their characteristics and applicability depend on various physical-chemical factors, such as temperature, pressure, ionic strength (amount of ions of sodium and calcium) and pH changes [10]. Many recent studies can be found in the literature which were interested in the preparation of gluten-free hydrogels for food and even non-food applications [11]. In this study, novel raw materials such as tea pruning waste were considered a rich source of polyphenols [12; 13] with antioxidant properties, as well as two varieties of hops considered for their microbial growth inhibitory power and relaxant and antioxidant properties. All this, encompassed with the use of green extraction techniques such as microwave-assisted extraction (MAE), microwave hydrodiffusion and gravity (MHG), ultrasound-assisted (US) extraction in a water bath or hot water under pressure or autohydrolysis (AH), promoted the recovery of high valuable compounds, using resources more efficiently and saving energy and time when compared with the traditional methods [14].