**5. When sensory properties can compromise the intake of potential healthy phenolic compounds**

It is undeniable that PC are a key target for the Food Industry on the design of new healthy products, as widely documented in the previous sections. Nevertheless, PC account for the main organoleptic properties of food products, mainly color and taste. Anthocyanins account for the (red) color of fruits and derived products, and flavanols and tannins are linked to unpleasant taste properties, namely astringency and bitterness. So, while PC have high expectations towards the development of health-orientated and functional products, a central challenge could be aligning their applications with consumer acceptability.

#### **5.1 PC sensory properties**

Astringency is a trigeminal sensation described as a mouthfeel of dryness, roughness and puckering sensations. It is induced by different classes of compounds

#### *Eat Tasty and Healthy: Role of Polyphenols in Functional Foods DOI: http://dx.doi.org/10.5772/intechopen.96577*

such as tannins, acids and alumns. In food, tannins are the main contributors to astringency perception. Several mechanisms are currently proposed to explain astringency molecular onset. The most studied one relies on the interaction and precipitation of particular families of salivary proteins, namely proline-rich proteins. The involvement of oral epithelial cells has been also reported and more recently the activation of G-protein coupled receptors was also reported. The involvement of oral mechanoreceptors is also a hypothesis despite no tangible data has been reported so far.

On the other hand, the perception of bitter taste is well characterized. Bitterness is perceived by activation of specific receptors, the bitter taste receptors (TAS2Rs). Humans express 25 TAS2Rs to perceive hundreds of bitter tasting molecules, with very wide structural features. These receptors occur at the cell-membrane of gustative cells within taste buds of human tongue. Among the wide diversity of TAS2Rs agonists reported there are several PC. In fact, some of these compounds are highly efficient agonists activating TAS2Rs at very low concentrations.

The importance of these taste properties is that they have elicited negative consumer reactions when present at high intensity in some products [109], decreasing the overall acceptability. This can compromise the intended intake of these new and functional food products.

#### **5.2 Phenolic compounds as ingredients in functional foods**

In the last years, the application of PC in functional and/or fortified foods has been widely reported. This has been mainly achieved by using either food industry by-products or wastes. Most studies use by-products from fruits (43%), followed by the application of winery (19%) and vegetable (13%) by-products [110]. Among fruit and vegetable by-products, citrus, tomato, grape, and apple by-products have been used in a wide range of food products (**Table 2**). One of these by-products is pomace (e.g. derived from apple or, grape), the main solid waste generated in juice or winemaking factories. It contains plenty of different varieties of nutritionally important compounds, such as dietary fibers, carbohydrates, PC, and minerals presenting a huge potential as a source of bioactive compounds. In addition to by-products or wastes, also some other high-PC content sources have been used to supplement food such as green tea.

Most of the reported studies use different fruit cultivars, obtained from different industry practices but without a deep characterization of the PC content. So, global relationships between PC composition-rheological-sensory properties-health inputs are not easily attained.

A cross-cut problem in most studies associated with the incorporation of these compounds in food matrices is that they can modify sensory properties leading to astringency and bitterness.

#### *5.2.1 Addition of PC to bakery products*

A significant amount of grape PC (near 70%) remains in pomace after wine making, the most important being tannins, anthocyanins, and phenolic acids, the quantities depending on the grape variety and winemaking practices. This by-product has been applied in bread, pancakes, pasta, biscuits, and other derived products. Some studies are summarized in **Table 1**.

White grape pomace has been also used to supplement biscuits [111]. In this case, the profile of PC was dominated by gallic acid, tyrosol and γ-resorcylic acid, which contributed nearly 87% of total PC. In this case, at sensory level, the replacement by grape pomace affected mainly on two attributes: fruity-acidic


#### *Functional Foods - Phytochemicals and Health Promoting Potential*

