12
1 Polyphenols and the Mediterranean Diet …
content (0–5 mg/kg). Common olive oil (10–100 mg/kg) and pomace olive oil (10–
30 mg/kg) also exhibited low contents of polyphenolic compounds.
With reference to apple juices, the phenolic composition and total polyphenols’
level depend on the processing steps in obtaining the juice. Enzymatic and physical
methods may produce apple juices with different content in polyphenols. Pectinolytic
enzymes destroy the polysaccharides structures and allow the release of phenolic
compounds from the fruit.
Green, black and oolong tea are produced differently. Green tea keeps the highest level of total phenolics, of which about 94% of flavonoids is catechins (Duh
et al. 2004). Oolong tea contains about 18% of total phenolics and 4.4% of
flavonoids. Theaflavins and thearubigins predominate in black tea; chlorogenic, caffeic, p-coumaric and quinic acids have been also detected in black tea (Kiehne and
Engelhardt 1996).
Crozier and colleagues have studied the impact of culinary steps (frying, boiling and microwaving) on the quercetin content of onions and tomatoes. Authors
have found that the most detrimental procedure in terms of quercetin loss was the
boiling step, as boiling onions and tomatoes in water for 15 min were found to
reduce the levels of quercetin in onions and tomatoes by 75 and 80%, respectively
(Crozier et al. 1997). Finally, authors found that the order from the most detrimental to the less one cooking manner is boiling (80% loss of quercetin from the food
matrix) > microwaving (with 65% loss from the food matrix) > frying (30%).
Food technologists are aware that during the processing steps of some new foodstuffs (i.e. introducing new pigments, new taste, new flavour, new odour and new
appearance), many unknown and uncontrolled chemical and biochemical reactions
can take place. Trial and error still prevail in redefining the sensorial properties of
ultraprocessed foods.
6 Efforts are made to favour some desirable chemical and enzymatic reactions while inhibiting others. An example is the exposure to oxygen and
light, which degrade polyphenols leading to colour changes and marked losses of
antioxidant properties. Polyphenol structures can be affected by heat, and its preservation is very important in fruit juices leading to the development of new physical
extraction methods.
Genetic variability, structural diversity, biochemical and chemical reactivity
towards oxidation, the ability to associate with proteins and polysaccharides and
impact on food processing are factors implying phenolic compounds. Besides this
structural, quantitative, qualitative and relational biovariability, polyphenols have
important sensorial properties on taste, odour, aroma and colour (Cheynier et al.
1998; Shoji 2007).
6 On ultraprocessed foods: Fardet (2018).
1 Polyphenols and the Mediterranean Diet …
content (0–5 mg/kg). Common olive oil (10–100 mg/kg) and pomace olive oil (10–
30 mg/kg) also exhibited low contents of polyphenolic compounds.
With reference to apple juices, the phenolic composition and total polyphenols’
level depend on the processing steps in obtaining the juice. Enzymatic and physical
methods may produce apple juices with different content in polyphenols. Pectinolytic
enzymes destroy the polysaccharides structures and allow the release of phenolic
compounds from the fruit.
Green, black and oolong tea are produced differently. Green tea keeps the highest level of total phenolics, of which about 94% of flavonoids is catechins (Duh
et al. 2004). Oolong tea contains about 18% of total phenolics and 4.4% of
flavonoids. Theaflavins and thearubigins predominate in black tea; chlorogenic, caffeic, p-coumaric and quinic acids have been also detected in black tea (Kiehne and
Engelhardt 1996).
Crozier and colleagues have studied the impact of culinary steps (frying, boiling and microwaving) on the quercetin content of onions and tomatoes. Authors
have found that the most detrimental procedure in terms of quercetin loss was the
boiling step, as boiling onions and tomatoes in water for 15 min were found to
reduce the levels of quercetin in onions and tomatoes by 75 and 80%, respectively
(Crozier et al. 1997). Finally, authors found that the order from the most detrimental to the less one cooking manner is boiling (80% loss of quercetin from the food
matrix) > microwaving (with 65% loss from the food matrix) > frying (30%).
Food technologists are aware that during the processing steps of some new foodstuffs (i.e. introducing new pigments, new taste, new flavour, new odour and new
appearance), many unknown and uncontrolled chemical and biochemical reactions
can take place. Trial and error still prevail in redefining the sensorial properties of
ultraprocessed foods.
6 Efforts are made to favour some desirable chemical and enzymatic reactions while inhibiting others. An example is the exposure to oxygen and
light, which degrade polyphenols leading to colour changes and marked losses of
antioxidant properties. Polyphenol structures can be affected by heat, and its preservation is very important in fruit juices leading to the development of new physical
extraction methods.
Genetic variability, structural diversity, biochemical and chemical reactivity
towards oxidation, the ability to associate with proteins and polysaccharides and
impact on food processing are factors implying phenolic compounds. Besides this
structural, quantitative, qualitative and relational biovariability, polyphenols have
important sensorial properties on taste, odour, aroma and colour (Cheynier et al.
1998; Shoji 2007).
6 On ultraprocessed foods: Fardet (2018).