## 1 Introduction  
The staggering amount of food waste, mainly related to the rapid deterioration of vegetables and fruit, prompts researchers to find novel methods for using fresh fruits and vegetables as well as extending their shelf-life and suitability for consumption. The use of whole fruits or vegetables for the production of functional food, including powdered drinks, in contrast to the traditional production of juices, does not deprive the finished product of the beneficial dietary fiber and many active compounds associated with cell walls, such as phenolic acids. Secondly, it is pro-ecological as it does not generate waste, which is a significant problem due to its low microbiological stability and high disposal costs [1]. A lot of emphasis is placed on the possibility of drying and powdering vegetables and fruits. After all such products might be used as commercial and value-added products, which can find applications in preparing smoothie-like beverages, or as additives rich in vitamins and antioxidants dedicated to, e.g., ice creams, noodles, cakes, etc. Such a premix of high protein vegetables and fruits in dehydrated form also gains a ready-to-drink character after dissolving in water [2]. The functional beverages production sector is the fastest-growing of the functional food market and, has become increasingly popular among consumers conscientious about the impact of the diet on their health and wellbeing [3]. The powdered drinks have long-term constancy and the nutrients might be better preserved compared to liquid form. As their retarded deterioration rate is related to the little amount of water in the powder and the prevention of air ingress, powdered drinks are ideal products dedicated to fortification with nutrients and bioactive compounds [2]. Nonthermal techniques, such as lyophilization, despite its relatively high price, could be a good solution for the fruit-vegetable functional beverages food market, due to the possibility of long-term storage without significant loss of their biological activity, and ease of preparation and possibility of fortification with components with high nutritional value [3; 4; 5]. Besides the instant properties, such as wettability, dispersibility, and solubility, other factors, such as the dissolution time, hygroscopicity, compressibility, or flowability characters determine the quality and preference of powdered products [6]. In powdered beverages, maltodextrin (or other polysaccharides) is usually used for their stabilization after rehydration [5; 7; 8]. Unfortunately, it has a high glycemic index, which is undesirable in the case of the products dedicated to the elderly, especially diabetics [9]. So far, alternative carriers were used, such as modified starch, inulin, alginate, gum Arabic, or combinations of them [10]. The carrier agents may additionally protect sensitive food components, such as probiotics, and carotenoids; preserve flavors, and reduce volatility and reactivity [11; 12]. Additionally, in our studies, an alternative, natural stabilizer was used--flaxseed gum (FSG) exhibiting strong prebiotic potential and pro-health properties [13]. The use of biologically active substances in nutrition and disease prevention generates great interest in the food industry [14]. The expanding range of products classified as functional foods creates an opportunity to consciously shape the diet in the aspect of broadly understood preventive healthcare. Powdered drinks seem to be one of the meal alternatives. They are easy to prepare and can be carriers of desirable components dedicated to different consumer groups, e.g., the elderly who often struggle to bite, swallow and/or have deficiencies in micro- and macronutrients [15]. The composition, and thus bioactivity, of powdered beverages, can be easily tailored to specific needs. Beverages can be fortified with antioxidants [15], minerals, vitamins [16], dietary fibre [17], amino acids, peptides and proteins [18], pro- and prebiotics [19].