**4.2 Reduction of salt**

Reducing the consumption of salt in general population has been identified as a priority intervention to reduce NCDs. Indeed, the World Health Organization has

agreed to diminish 30% of salt intake by 2025. The use of vegetable extracts able to enhance flavor while improving health benefits arises as a promising alternative. Under this framework, extracts rich in PC have been already used in food industry. Indeed, green tea extracts were used to enhance the flavor of fish flesh [75], soybean isoflavones enhance the flavor quality in the muscle of grass carp while contribute to health benefits [76]. Furthermore, PC-rich extracts containing aromatic compounds such as onion, garlic, celery spices and herbs could also be a nutraceutical alternative to reduce salt.

#### **4.3 Preservative agents**

Spoilage are one of the main causes of economic loses in food industry [77]. Traditionally, the use of artificial preservative technologies such as drying, freezing, thermal treatments and more recently modified atmosphere packaging and nonthermal physical treatments (pulsed electric fields and high hydrostatic pressure) have been employed to extend shelf life of food [78]. Synthetic chemical preservatives such as, tartaric or citric acids; sulphites, sorbate, propionate and benzoate; or nitrites and nitrates, have been extensively used but in recent times the use of natural products as preservative agents acquire relevance [79]. The increase in the consumption of minimally processed foods joined with the clean label requirements boost the trend to explore the use of natural antimicrobials for food preservation. PC have been widely reported as antimicrobial agents [80]. Indeed antimicrobial extracts containing PCs have been already designed for this purposes, such as an extract of moso bamboo (Takeguard™) launched by Takex Labo (Osaka, Japan) or a mixture of different natural antimicrobial extracts (Biovia™ YM10) including green tea extract launched by Danisco DuPont [81]. **Table 1** summarizes the already tested PC from food byproducts with antimicrobial properties.

#### **4.4 Colorant agents**

Some PC are natural pigments with high potential to be incorporated into food systems as colorant agents. However, the great reactivity and lack of chemical stability make necessary to deliver these compounds in encapsulated forms. Among PC sources, flowers such as *Clitoria ternatea* petals are commonly used in health drinks and natural food colorants [95]. Moreover, Brazilian fruit peel - jabuticaba (*Plinia cauliflora* (Mart.) Kausel) and propolis from Tubuna (*Scaptotrigona bipunctata*) encapsulated in alginate beds have been tested as a new ingredient with colorant properties and health outcomes [96]. Betacyanins (red-violet) and betaxanthins (yellow-orange), from beets are also powerful antioxidants, which can be used as natural colorants in the food industry [97]. Furthermore, pecan nut shell has been already studied as a food colorant for active packaging for color stabilization [98].

#### **4.5 Emulsifier agents**

New alternatives to reduce the content of saturated fats while maintaining the emulsifying properties of sauces must be evaluated. To date, some amphiphilic plant proteins such as wheat gliadins and maize zeins have rheological properties suitable to fabricate colloidal particles for stabilizing foams and emulsions. However, in recent years the use of novel emulsifiers to obtain nutraceutical emulsions are being studied. In this context, the ability of PC to bind to proteins have been described as able to improve the chemical and physical stability of emulsions, arising as a good source of nutraceuticals while emulsifier agents. The emulsifying


#### **Table 1.**

*Polyphenols as food preservatives. Adapted from [81].*

properties of proteins have also been modified by introducing polysaccharides; however, little to nothing is known about how ternary interactions could affect the physical stability of emulsions. Ternary conjugates were fabricated by covalently bonding polyphenol, protein, and polysaccharide together. The protein was used to provide surface activity, the polysaccharide to provide strong steric repulsion, and the PC to provide functional properties [99]. But, some PC have poor interfacial activity, like green tea PCs [100]. However, the interaction between green tea PC and the protein β-lactoglobulin (β-lg) (spontaneous nanocomplexes formation) was sucesfully used as an emulsifier agent in fish oil [101]. Colloidal complexes were also prepared from pea protein and grape seed proanthocyanidin and the ability of these complexes to form and stabilize oil-in-water emulsions were verified [102]. Overall, covalent and noncovalent interactions between proteins and PC have provide novel insights into the interfacial behaviors of novel emulsifiers [103].

#### **4.6 Matrix effect**

There are several factors which could influence the PC delivery to bloodstream, to their target tissues and biological activities. Disruption of the natural matrix or the microstructure created during processing may influence the release, transformation, and further absorption of some nutrients as well as functional ingredients such as PC in the digestive tract. Some *in vitro* studies verified the effect of milk proteins in PC bioaccesibility and bioactivities after consuming oat based breakfast cereals with blueberry fruit [104]. The absorption of flavanols, such as green tea catechins, is influenced by epimerization reactions, which usually occur during technological processing as well as the presence of lipids and carbohydrates. Moreover is enhanced by the presence of piperine and tartaric acid [105]. Phenolic acids and Flavanones such as hesperidin are affected by the attached sugar, which can covalently link these compounds to the cereal bran matrix [106, 107]. There are only a few examples reported on PC release from the food matrix, but existing information established a direct relationship between the absorption and dose but is sometimes linear and sometimes saturated [108]. The lack of systematic information on the effects of other components on the bioavailability of PCs needs to be performed. This information must be completed by human studies to further establish general principles affecting absorption in vivo. Information derived from such experiments could be useful for the optimal design of future bioefficacy studies for functional foods production.
