# Microencapsulation of Tomato
## 1 Introduction  
Food industries generate a large quantity of solid by-products that turn into food wastes. As such, they are struggling to reduce organic wastes due to problems, such as accumulation, handling, and disposal costs. By-products obtained may well be suitable for noble purposes, since they are rich in bioactive compounds [1; 2]. Many researchers have investigated the potential use of agroindustrial by-products for their inclusion in the human diet, which could correctly solve the problem of waste associated with food processing and reduce industrial costs [3; 4]. The tomato is one of the most produced vegetables worldwide. The European Union produced approximately 17.6 million tonnes of tomatoes in 2015, of which around 10% came from Portugal (1.4 million tonnes). Although the tomato is commonly consumed fresh, around 90% of the tomato consumption in Portugal corresponds to processed products, such as tomato juice, paste, puree, ketchup, and sauce [5]. In the case of the tomato processing industry, about 5% of the total raw material is discarded as tomato pomace. It is composed of 44% of seeds and 56% of pulp and skin and isgenerally used for animal feeding [2]. Tomato pomace is a rich source of nutrients and bioactive compounds like carotenoids, sugars, and fibers [3]. Natural bioactive compounds, such as carotenoids and polyphenols, are molecules that provide health benefits due to their biological activities, like antioxidant, antihypertensive, anti-proliferative, and anti-inflammatory capacities [6]. Carotenoids as lycopene are antioxidants naturally present in some food products and may be recovered as concentrated extracts from agroindustrial by-products, like tomato pomace. They are referred to be effective against cancer and cardiovascular diseases [7]. Due to the high sensitivity of those compounds to environmental conditions (heat, light, pH, oxygen), bioactive compounds must be protected in order to preserve their expected benefits. Microencapsulation has been described as a good strategy in the food industry for various purposes, such as preservation of functional properties, masking undesirable flavors, improved handling and utilization of bioactives, development of functional foods, controlled release of the bioactive compounds at the desired time and specific target, and increasing bioavailability of bioactive compounds [8; 9]. Among various encapsulation techniques, spray drying is the most common technology applied due to its low cost, flexibility, and production of good quality powder particles [10]. The principle of spray drying is the dissolution of the core (compounds to be protected) in the dispersion of a chosen matrix (wall material). The dispersion is subsequently atomized into heated air, which promotes the rapid removal of the solvent (water) [11]. The quality of the powdered particles may be affected by the type of wall material used and by the spray drying operating conditions, such as the inlet and outlet temperatures, feed flow rate, and inlet air flow rate [12]. The structures formed in the encapsulation process are composed by the core (bioactive compounds) and the protective matrix materials. These materials are commonly polysaccharides (e.g., starches and arabic gum), proteins (e.g., gelatin and casein), lipids (e.g., stearic acid and mono- and diglycerides) and their mixtures [13]. Arabic gum is one of the most common wall materials used in microencapsulation, due to its excellent emulsification properties, high solubility, low viscosity, and good retention of volatiles [14]. It is a highly branched edible polymer exuded from acacia trees, composed of approximately 2% protein and high proportion of carbohydrates (D-galactose, L-rhannose, L-arabinose, and D-glucuron acid) [12]. In addition, inulin is also an interesting candidate, as beyond protection, it may act also as a prebiotic, stimulating the activity of colon beneficial microflora, and can improve calcium bioavailability, amongst other benefits [15].