40
3 Dietary Intakes of Polyphenols in Selected Vegetables and Fruits
3.1.5 Non-alcoholic Beverages
The category of ‘non-alcoholic beverages’ may be complex enough, including very
different sub-classes:
(a) Herbal infusions (e.g. black or green tea; South American yerba mate; etc.) and
edible extracts after heat extraction in water (e.g. coffee)
(b) Fruit juices.
It has to be highlighted that: fruit juices may have a chemical composition which
might be similar to the composition of original fruits. For this reason, each discussion
on fruit juices should be made when speaking of original (fresh) fruits.
In this ambit, and with concern to Med Diet-related beverages only, the categories
of herbal infusions and coffee/tea products can be discussed. Interestingly, both coffee
and other tea-based infusions are excellent phenolic sources. Coffee is reported to act
positively against type-2 diabetes mellitus, cirrhosis and other non-communicable
diseases (NCD) (NCBI 2018), while claimed negative effects on the cardiovascular
system have to be demonstrated yet. Anyway, filtered coffee solutions contain more
than 400 mg/100 g of total phenolic compounds (Pérez-Jiménez et al. 2010), and
chlorogenic acid—an ester from caffeic acid and quinic acid, belonging to tannins—
is the main phenolic molecule with 70–350 mg per 200 ml of filtered solution.
Interestingly, these data assure a minimum quantity of 35 (maximum: 175) mg of
caffeic acid (NCBI 2018).
Apart from coffee, the main representative for this heterogeneous class of nonalcoholic beverages is tea. Actually, ‘tea’ is the drink obtained from the aqueous
infusion of leaves from Camellia sinensis (origin: Japan and China). However, black
and green tea infusions are now normal beverages in Europe and in Arabic countries
also (Delgado et al. 2017a, b).
Different systems are used for producing optimal tea infusions: basically, green
tea leaves have to be slightly wilted after being harvested, steamed, shaped and dried.
The process for black tea imposes the so-called tea fermentation of leaves after indoor
withering. The enzymatic oxidation by means of polyphenol oxidase is consequently
desired; after this critical step, leaves have to be rolled, crushed and finally exsiccated
(Delgado et al. 2017a, b).
Anyway, the bioavailable amount of polyphenols per serving size (approximately
200 mg of herbal infusion) is similar in both situations: 197 and 173 mg/100 for
black and green tea infusions, respectively (Pérez-Jiménez et al. 2010). The difference is in chemical profiles, although tannins and flavonoids predominate. Black
tea contains 60–70% of theaflavins and related compounds, while the remaining
30–40% is composed of non-polymeric catechins (between 20 and 30%) and other
unidentified molecules (van Duynhoven et al. 2013). Interestingly, non-polymeric
catechins and other tannins are responsible for the claimed antioxidant power, anticancer properties, astringency, aroma and the variety of colours and tones (NCBI
2018). On the other side, catechins are slightly more abundant in green tea: 30–40%
of the total extractable matter, with epigallocatechin-3-gallate (EGCG) as the main
3 Dietary Intakes of Polyphenols in Selected Vegetables and Fruits
3.1.5 Non-alcoholic Beverages
The category of ‘non-alcoholic beverages’ may be complex enough, including very
different sub-classes:
(a) Herbal infusions (e.g. black or green tea; South American yerba mate; etc.) and
edible extracts after heat extraction in water (e.g. coffee)
(b) Fruit juices.
It has to be highlighted that: fruit juices may have a chemical composition which
might be similar to the composition of original fruits. For this reason, each discussion
on fruit juices should be made when speaking of original (fresh) fruits.
In this ambit, and with concern to Med Diet-related beverages only, the categories
of herbal infusions and coffee/tea products can be discussed. Interestingly, both coffee
and other tea-based infusions are excellent phenolic sources. Coffee is reported to act
positively against type-2 diabetes mellitus, cirrhosis and other non-communicable
diseases (NCD) (NCBI 2018), while claimed negative effects on the cardiovascular
system have to be demonstrated yet. Anyway, filtered coffee solutions contain more
than 400 mg/100 g of total phenolic compounds (Pérez-Jiménez et al. 2010), and
chlorogenic acid—an ester from caffeic acid and quinic acid, belonging to tannins—
is the main phenolic molecule with 70–350 mg per 200 ml of filtered solution.
Interestingly, these data assure a minimum quantity of 35 (maximum: 175) mg of
caffeic acid (NCBI 2018).
Apart from coffee, the main representative for this heterogeneous class of nonalcoholic beverages is tea. Actually, ‘tea’ is the drink obtained from the aqueous
infusion of leaves from Camellia sinensis (origin: Japan and China). However, black
and green tea infusions are now normal beverages in Europe and in Arabic countries
also (Delgado et al. 2017a, b).
Different systems are used for producing optimal tea infusions: basically, green
tea leaves have to be slightly wilted after being harvested, steamed, shaped and dried.
The process for black tea imposes the so-called tea fermentation of leaves after indoor
withering. The enzymatic oxidation by means of polyphenol oxidase is consequently
desired; after this critical step, leaves have to be rolled, crushed and finally exsiccated
(Delgado et al. 2017a, b).
Anyway, the bioavailable amount of polyphenols per serving size (approximately
200 mg of herbal infusion) is similar in both situations: 197 and 173 mg/100 for
black and green tea infusions, respectively (Pérez-Jiménez et al. 2010). The difference is in chemical profiles, although tannins and flavonoids predominate. Black
tea contains 60–70% of theaflavins and related compounds, while the remaining
30–40% is composed of non-polymeric catechins (between 20 and 30%) and other
unidentified molecules (van Duynhoven et al. 2013). Interestingly, non-polymeric
catechins and other tannins are responsible for the claimed antioxidant power, anticancer properties, astringency, aroma and the variety of colours and tones (NCBI
2018). On the other side, catechins are slightly more abundant in green tea: 30–40%
of the total extractable matter, with epigallocatechin-3-gallate (EGCG) as the main