Polyphenols: what they are used for, where to find them and what are their functions

You probably eat them every day together with the food that’s on your table or you know them as a compound present in the plants in your garden: we are talking about polyphenols!

Ever more popular, these substances are appreciated for their beneficial properties both by our organism and by the environment. Let’s get to know them a little better, analyzing their different types, functions and various fields of application.

What are polyphenols and how are they classified?

Polyphenols are antioxidant molecules, present in almost the whole plant kingdom, in different concentration according to the specific species. Probably we take them every day without realizing it: they are naturally present in cocoa, red wine, green tea, red fruits and many other types of fruits and vegetables.

They are molecules naturally produced within plant’s metabolic processes as a defense barrier against the attack of external pathogens. The molecules that make up polyphenols are divided into 3 macro-classes, according to their chemical structure, function and origin:

• Phenols: found mostly in small fruits and tea.
• Flavonoids: largest class of polyphenols which are present, for example, in citrus fruits and pomegranate.
• Tannins: they are -divided in hydrolysable and condensed and they are present – as we will see down below – in grapes and in other types of fruits.

Why are polyphenols good for us?

Polyphenols are beneficial to our health in many ways, but the most universally recognized ability is to counteract free radicals, namely those molecules harmful to our metabolism. Polyphenols, in fact, are powerful antioxidants that can prevent cellular damage, also performing an anti-inflammatory action.

But why do most plant species produce polyphenols?

Mainly to protect themselves: without polyphenols, in fact, plants and trees would not be able to defend themselves from external pathogens attacks and from oxidative stress, caused for example by UV rays. Moreover, polyphenols are those molecules responsible for the color of fruit and vegetables. The vivid colors of fruits are an indispensable characteristic which makes them attractive both for man and animals, facilitating the dispersion of their seeds and ensuring their reproduction.

What food is rich in polyphenols?

Polyphenols are commonly found in all vegetables: specific families of vegetables produce specific types of polyphenols.

However, the concentration of polyphenols in fruit and veggies is influenced by many factors, such as the degree of ripeness, environmental factors such as climate, soil composition, product processing and preservation method. In general, we can say that the food sources richest in polyphenols are grapes, persimmons, strawberries, artichokes, Brussels sprouts and lychee, but also oil, tea (in particular black tea and green tea), cocoa and chocolate, red fruits, capers, onions and apples

The antioxidant power of wine polyphenols

Good news for wine lovers: unlike other alcoholic beverages or spirits, wine contains an extremely high concentration of polyphenols. Some recent studies have proven that polyphenols confer to wine its antioxidant power, which is fundamental to reduce the levels of bad cholesterol in the blood, as well as reducing the risk of cardiovascular diseases.

Grape polyphenols are generally found in the whole bunch, but the highest concentration is in the skins, stalks and seeds. During wine making, most of polyphenols (about 60%) are naturally released during the maceration phase, a key step to obtain a quality product.

Types of polyphenols present in wine

In grapes we find 3 classes of polyphenols:

• Phenolic acids: present mainly in the pulp and stalks.
• Tannins: present in seeds and skins.
• Flavonols and anthocyanins: present only in the skins.

Their concentration varies according to the cultivation, climatic conditions, level of ripeness and the phases of wine making: anthocyanins are present in higher percentage especially when the grape is ripe and very colored, whereas the concentration of tannins is highest from the first phases of ripening to harvest. As for phenolic acids, their concentration is higher in the very first phases of ripening, and then it drastically decreases before harvesting.

However, it is the prevailing tannic component to make a wine qualitatively excellent, both because it contributes to the vivid red color and because, thanks to the antioxidant action, it allows a slow aging process, without altering its qualities.

A wine with a high tannin content, moreover, has a typical sour and astringent taste, so appreciated by enologists worldwide, because it is an indicator of the capacity of wine to improve with aging.

Oenological tannins

Of course, the concentration of tannins is not the same in all red berried grape. For this reason, with the advent of modern technologies, it is now possible to add them throughout distinct phases of wine making, therefore making useful even the grapes which were previously “discarded” for premium quality wines.

Tannins are extracted from different botanical species, such as Quebracho (condensed tannins), oak, chestnut, tara and gall (referred to as hydrolysable tannins).

What are the benefits of adding tannin during wine fermentation?

It is mainly used to stabilize the red color and as a natural preservative for wine, guaranteeing its quality over time, imparting softness and body, while enhancing its organoleptic properties.

Is there a downside to taking polyphenols?

As already mentioned, polyphenols are natural substances present in almost all fruit and vegetables. We consume them daily as part of a healthy and balanced diet which ensures several benefits for our body.

Can they also be taken “on their own”, for example as supplements?

Indeed. Tannin extracts are regularly used as effective anti-inflammatory, antibacterial and gut flora regulators. One example? Many natural remedies against cystitis are based on cranberry and bearberry, fruits that contain high amounts of tannin. And the efficacy of these remedies is precisely due to tannin and its ability to regulate the bacterial flora.

Obviously, as for all supplements, they should never be considered as substitutes of a balanced diet. Moreover, the “do it yourself” approach is always discouraged: it is recommended to take them for limited periods and always following the doses recommended by a specialist.