# Advances in the Application of Microcapsules as Carriers of Functional Compounds for Food Products
## 4 Core Materials  
The core materials, which are also called coated material and actives, among other names, can be pure active substances or mixtures of high-added-value components extracted from plant leaves, flowers, stems, fruits, vegetables, or several agricultural residues. Examples of such materials are natural antioxidant bioactive compounds (carotenoids, phenolic compounds), vitamins, flavors, enzymes, and microbial cells (e.g., probiotic bacteria) [91; 92; 93] (Table 1). Carotenoids, the most studied of the natural food pigments, are widely studied due to their beneficial effects on human health and their color. Some of the main benefits of carotenoids are the prevention of many diseases such as cancer, heart and vascular diseases, cataracts, hypertension, age-related macular degeneration, and diabetes, among others. Additionally, carotenoids also have the functionality of enhancing intercellular communication and immune system activation. Carotenoids are divided into two classes based on functional group: (1) xanthophylls, molecules containing oxygen such as lutein, zeaxanthin, and \(\beta\)-cryptoxanthin; and (2) carotenes, non-oxygenated molecules such as \(\alpha\)-carotene, \(\beta\)-carotene, and lycopene. [94; 95]. These are lipophilic pigments responsible for imparting the yellow, orange, red, and green color in many foods such as carrots, sweet potato, pumpkin, broccoli, and spinach (\(\alpha\)-carotene and \(\beta\)-carotene), tomatoes, watermelon, and guava (lycopene), mandarin, orange, papaya, and egg yolks (\(\beta\)-Cryptoxanthin), and leafy greens such as spinach, collard, and kale (lutein and zeaxanthin) [94]. Phenolic compounds have been considered as promising bioactive molecules for the pharmaceutical and food industries. They constitute one of the most numerous groups of plant secondary metabolites. This group is constituted by molecules of different molecular weights and chemical structures, such as flavonoids, phenolic acids, stilbenes, tannins, and coumarins. Phenolic compounds are antioxidant, anti-inflammatory, and/or as antimicrobial agents. Therefore, the ingestion of polyphenol-rich food products may reduce the risk of developing cancer, cardiovascular diseases, diabetes, and osteoporosis. Fruits (e.g., graprefruit, lemon, blueberry, and strawberry), vegetables (e.g., potato, spinach, asparagus, artichoke, and lettuce), beverages (e.g., coffee, red wine, black and green teas, and orange and graprefruit juices), and herbs (e.g., basil, parsley, thyme, and mint) are examples of sources of phenolic compounds [40; 96]. Foods enriched in these compounds show a delay in the formation of toxic oxidizing products and a prolonged shelf life [97]. Essential oils are complex mixtures of volatile lipophilic substances characterized by a strong flavor. They are plant secondary metabolites that can be synthesized by the whole plant (e.g., mint, lavender) or stored in certain parts of the plant, such as flowers (e.g., chamomile, bergamot), leaves (e.g., eucalyptus, basil, and lemongrass), rhizomes (e.g., turmeric, ginger), or seeds (e.g., nutneg, cloves). They are commonly used in the cosmetic, pharmaceutical, and food industries due to their flavor or biological activities (e.g., antioxidant and antimicrobial properties). However, large losses of essential oil active compounds are common during the handling and storage due to their extreme sensitivity to oxidation, resulting in losses of their valuable properties [29; 98]. Probiotic bacteria are a group of bacteria that when present in sufficient quantity may confer health benefits to the host. Human health benefits associated with probiotics include efficacy in the treatment of various intestinal disorders, inhibition of pathogenic microorganisms, improved tolerance to lactose, prevention of some cancers, reduction of total cholesterol, improvement of the immune system, and increase of the intestinal microbiota.