## 1 Introduction
Microencapsulation of probiotics is designed to increase their stability and viability during processing and storage of several types of products, and in the presence of gastric and intestinal fluids [24]. Spray drying is the most common method used to microencapsulate probiotics [22, 25] because it has a high production rate, low operation cost, and the product has low humidity, is stable, and occupies a small volume [26]. However, the main disadvantage of spray drying is the impact that the process temperature has on the cellular integrity of probiotics during drying: It reduces the stability of encapsulated bacteria during product storage due to osmotic stress, damage to the membrane, ribosome, DNA, and protein [27, 28]. The composition and concentration of the solids in the encapsulation solution are relevant factors because they define the degree of protection for probiotics against adverse environmental factors, such as thermal and dehydration damage during spray drying, storage conditions, and gastrointestinal conditions of the host. Maltodextrin, protein, polysaccharides, and reconstituted skimmed milk are the most frequently used encapsulating agents in the encapsulating solution to protect probiotics from the aforementioned adverse factors [25, 26]. Some other materials have been suggested for use in the encapsulating solution, such as prebiotics, soluble fiber, microbial polysaccharides (pullulan),and fruit juices; the results are promising as they improve the survival and viability of probiotics during spray-drying encapsulation and during storage [22; 25; 29; 30; 31; 32; 33]. Prebiotics are of special interest because of their symbiotic relationship with probiotics and because some may act as a thermoprotector [34; 35; 36]. Inulin (INL) is a heterogeneous blend of fructose polymers that can be found in a wide range of plants, such as dahlia, garlic, Jerusalem artichoke, onions, chicory roots, and others [37]. INL is a functional food ingredient that can be used as a prebiotic, texture modifier, fat or sugar replacer, or dietary fiber [38]. The consumption of INL reduces the high triacylglycerol concentrations and, therefore, reduces the risk of atherosclerosis, decreases the risk of intestinal tract diseases (irritable bowel diseases and colon cancer), and enhances the absorption of calcium, magnesium, and iron [38]. Flaxseed (_Linum usitatissimum_ L.) is considered a functional food because it contributes to nutrition and has shown numerous beneficial health effects [39]. This seed presents a high content of soluble fiber (7-10% of seed weight), commonly known as flaxseed mucilage (FM) [39; 40]. It is characterized as a mixture of two acidic (rhamogalacturonan I) [41; 42] and one neutral polysaccharide (arabinoxylan) [43; 42]. FM has several potential applications, such as a texturing agent in the food industry and a lubricant for the skin surface in cosmetic applications. In addition, the syneresis of the gel decreases when FM is mixed with other hydrocolloids [44]. Furthermore, FM consumption can prevent intestinal inflammation, decrease glucose and cholesterol in the blood [45], alter the gut microbiota and improve insulin sensitivity in obese postmenopausal women [46], and suppress postprandial lipemia in young men [47]. Chia (_Salvia hispanica_ L.) seeds are considered a safe and functional food, contributing to nutrition and preventing and treating several diseases such as cardiovascular diseases, inflammatory and nervous system disorders, and diabetes, among others [48]. In 2017, the European Parliament and the Council on novel foods declared chia seeds a novel food, and, therefore, able to be placed on the market [49]. Chia soluble dietary fiber is a clear mucilaginous gel known as chia seed mucilage (CM). It is composed of neutral sugars, D-xylose and D-glucose, showing the presence of various carbohydrates on its structure, forming a tetra-saccharide as proposed by [PERSON] et al. [50].