42
3 Dietary Intakes of Polyphenols in Selected Vegetables and Fruits
Singh et al. 2017) and red, brown and black bean extract contained high polyphenol
and tannin’s content in comparison with whole bean extract (Madhujith et al. 2004).
3.1.7 Seeds
The most interesting seed with relation to polyphenol-containing foods is flaxseed
meal with 1528 mg/100 g of polyphenols (Pérez-Jiménez et al. 2010). The Latin
name of flaxseed (Linum usitatissimum L.) means ‘very useful’. Flax seeds have
long been used as food and feed, mainly in Canada, China, USA and India, where
it is eaten often grilled or boiled, after peeling. It is also used to extract flaxseed
oil. Flaxseed meal is the by-product of the flaxseed oil extraction process, which
is mainly used in feed (Herchi et al. 2014). Recently, several studies have focused
on the beneficial effects of the phenolic compounds of flaxseed, flaxseed oil and
flaxseed meals in human and cattle’s health. Lignans and phenolic acids are the
two main classes of polyphenols occurring in flaxseed meal, according to PhenolExplorer database. Quantified lignans (9–30 mg/g) included—in descending order—
secoisolariciresinol, lariciresinol, pinoresinol and matairesinol.
Flaxseed contains 75 times more lignans than other foods (Imran et al. 2015).
According to Phenol-Explorer database, phenolic acids are also present in a considerable amount, mainly the subclass of hydroxycinnamic acids (ferulic acid 4-Oglucoside and p-coumaric acid 4-O-glucoside). Furthermore, the secoisolariciresinol
is the principal dietary lignan present in flaxseed, and it may be considered as a
nutraceutical agent against different chronic diseases like cancer, atherosclerosis,
diabetes, kidney disorders and lupus nephritis (Imran et al. 2015).
3.1.8 Vegetables
The category of ‘vegetable’ products in the Med Diet ambit is really challenging.
On these bases, the best strategy could be the in-depth discussion of some selected
vegetables: olives and onions.
Certainly, one of these foods are olives (Olea europaea), due to their phytonutrients profile where oleuropein—an ester of 2-(3,4-dihydroxyphenyl)ethanol and a
peculiar glucoside—predominates. Different data concerning maturation effects in
green and black olives are available in Figs. 3.1 and 3.2.
Other important polyphenols commonly that found in olives also are p-coumaric
acid (Fig. 3.3) and 4-hydroxybenzoic acid (Fig. 3.4). Oleuropein (Fig. 3.5) is the
main responsible for the bitterness of olives, and its amount (initial value: 14% of
dry matter) is inversely correlated with maturation degree, with observed continuous
diminution until potential absence. Such process occurs simultaneously with the
darkening of the fruit and the softening of its pulp; fully ripe olives are black and
soft. On the other hand, tyrosol (Fig. 3.6) and hydroxytyrosol (Fig. 3.7) are expected
to augment at the same time.
3 Dietary Intakes of Polyphenols in Selected Vegetables and Fruits
Singh et al. 2017) and red, brown and black bean extract contained high polyphenol
and tannin’s content in comparison with whole bean extract (Madhujith et al. 2004).
3.1.7 Seeds
The most interesting seed with relation to polyphenol-containing foods is flaxseed
meal with 1528 mg/100 g of polyphenols (Pérez-Jiménez et al. 2010). The Latin
name of flaxseed (Linum usitatissimum L.) means ‘very useful’. Flax seeds have
long been used as food and feed, mainly in Canada, China, USA and India, where
it is eaten often grilled or boiled, after peeling. It is also used to extract flaxseed
oil. Flaxseed meal is the by-product of the flaxseed oil extraction process, which
is mainly used in feed (Herchi et al. 2014). Recently, several studies have focused
on the beneficial effects of the phenolic compounds of flaxseed, flaxseed oil and
flaxseed meals in human and cattle’s health. Lignans and phenolic acids are the
two main classes of polyphenols occurring in flaxseed meal, according to PhenolExplorer database. Quantified lignans (9–30 mg/g) included—in descending order—
secoisolariciresinol, lariciresinol, pinoresinol and matairesinol.
Flaxseed contains 75 times more lignans than other foods (Imran et al. 2015).
According to Phenol-Explorer database, phenolic acids are also present in a considerable amount, mainly the subclass of hydroxycinnamic acids (ferulic acid 4-Oglucoside and p-coumaric acid 4-O-glucoside). Furthermore, the secoisolariciresinol
is the principal dietary lignan present in flaxseed, and it may be considered as a
nutraceutical agent against different chronic diseases like cancer, atherosclerosis,
diabetes, kidney disorders and lupus nephritis (Imran et al. 2015).
3.1.8 Vegetables
The category of ‘vegetable’ products in the Med Diet ambit is really challenging.
On these bases, the best strategy could be the in-depth discussion of some selected
vegetables: olives and onions.
Certainly, one of these foods are olives (Olea europaea), due to their phytonutrients profile where oleuropein—an ester of 2-(3,4-dihydroxyphenyl)ethanol and a
peculiar glucoside—predominates. Different data concerning maturation effects in
green and black olives are available in Figs. 3.1 and 3.2.
Other important polyphenols commonly that found in olives also are p-coumaric
acid (Fig. 3.3) and 4-hydroxybenzoic acid (Fig. 3.4). Oleuropein (Fig. 3.5) is the
main responsible for the bitterness of olives, and its amount (initial value: 14% of
dry matter) is inversely correlated with maturation degree, with observed continuous
diminution until potential absence. Such process occurs simultaneously with the
darkening of the fruit and the softening of its pulp; fully ripe olives are black and
soft. On the other hand, tyrosol (Fig. 3.6) and hydroxytyrosol (Fig. 3.7) are expected
to augment at the same time.