1.3 Phenols, Their Chemical Structures, Sourcing and Interactions …
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The same authors have observed that the level of verbascoside on Manzanello cv.
olive fruits showed a gradual decrease with ripening, while their ligstroside level
remained constant. Esti and colleagues have considered the elenolic acid glucoside and 3,4-dihydroxyphenylethanol as indicators of the maturation of olive fruits
(Esti et al. 1998). They have claimed a negative correlation between the increase
of 3,4-dihydroxyphenylethanol and the amount of oleuropein when maturation is in
progress.
Moulehi and coworkers have studied the ripening impact on phenolic composition
of mandarin Citrus reticulate Blanco (Moulehi et al. 2012). They found that phenolic
acids increase up to the commercial mature scale value from 41.39 to 71.39 mg/g.
However, flavonoids exhibited the highest level at the semi-mature state. Some fluctuations on total polyphenols from unripe to overripe apples fruits have been reported
(Laaksonen et al. 2017).
1.3.6 Phenols and Their Impact in Food Processing
The ‘seasonality’ criterium, which is a basic feature of the Med Diet, must be taken
into consideration for several reasons. Seasonality applies to ‘fresh’ and ‘minimally
processed’ foods, which are the ones that should be preferred (Bach-Faig et al. 2011),
despite food processing has been used since antiquity to avoid food waste (e.g. drying
certain fruits, fermenting olives). The content of polyphenols is markedly influenced
by food processing steps/unitary operations even inside the same matrix. Boskou has
observed that phenolic level and phenolic content can depend on the style and even
for olives of the same style (Boskou 2017). The author claimed that higher phenolic
values were found in Greek-style natural black olives in brine, Kalamata olives in
brine and also in Italian table olives (240-1700 mg of caffeic acid/kg edible part).
Romero and colleagues showed that brined olives had the highest concentration in
total phenols (1200 mg/kg), whereas oxidized olives had the lowest quantity (Romero
et al. 2004). Melliou and coworkers reported values below 37 mg/kg for Californiastyle black ripe olives (Melliou et al. 2015). Moreover, Issaoui and colleagues have
reported that the percentage of polyphenols degradation was 33.20% with the traditional Tunisian process and 29.76% with the standard one for the Picholine cultivar,
while it was 34.14 and 49.54%, respectively, for the Meski cultivar (Issaoui et al.
2011).
Gorzynik-Debicka and coworkers have summarized on a figure the impact of
different kinds of technological processes for olive oil extraction, on the phenolic
concentration of the final product (Gorzynik-Debicka et al. 2018). Their research
shows that ‘virgin olive oil’ contains the highest level of polyphenols: generally, it
can range between 150 and 400 mg/kg, while refined olive oil has a low polyphenolic
contribute to flavour (given they are polar and thus mostly eliminated in the water fraction); many
different preparation of table olives include a debittering step.
11
The same authors have observed that the level of verbascoside on Manzanello cv.
olive fruits showed a gradual decrease with ripening, while their ligstroside level
remained constant. Esti and colleagues have considered the elenolic acid glucoside and 3,4-dihydroxyphenylethanol as indicators of the maturation of olive fruits
(Esti et al. 1998). They have claimed a negative correlation between the increase
of 3,4-dihydroxyphenylethanol and the amount of oleuropein when maturation is in
progress.
Moulehi and coworkers have studied the ripening impact on phenolic composition
of mandarin Citrus reticulate Blanco (Moulehi et al. 2012). They found that phenolic
acids increase up to the commercial mature scale value from 41.39 to 71.39 mg/g.
However, flavonoids exhibited the highest level at the semi-mature state. Some fluctuations on total polyphenols from unripe to overripe apples fruits have been reported
(Laaksonen et al. 2017).
1.3.6 Phenols and Their Impact in Food Processing
The ‘seasonality’ criterium, which is a basic feature of the Med Diet, must be taken
into consideration for several reasons. Seasonality applies to ‘fresh’ and ‘minimally
processed’ foods, which are the ones that should be preferred (Bach-Faig et al. 2011),
despite food processing has been used since antiquity to avoid food waste (e.g. drying
certain fruits, fermenting olives). The content of polyphenols is markedly influenced
by food processing steps/unitary operations even inside the same matrix. Boskou has
observed that phenolic level and phenolic content can depend on the style and even
for olives of the same style (Boskou 2017). The author claimed that higher phenolic
values were found in Greek-style natural black olives in brine, Kalamata olives in
brine and also in Italian table olives (240-1700 mg of caffeic acid/kg edible part).
Romero and colleagues showed that brined olives had the highest concentration in
total phenols (1200 mg/kg), whereas oxidized olives had the lowest quantity (Romero
et al. 2004). Melliou and coworkers reported values below 37 mg/kg for Californiastyle black ripe olives (Melliou et al. 2015). Moreover, Issaoui and colleagues have
reported that the percentage of polyphenols degradation was 33.20% with the traditional Tunisian process and 29.76% with the standard one for the Picholine cultivar,
while it was 34.14 and 49.54%, respectively, for the Meski cultivar (Issaoui et al.
2011).
Gorzynik-Debicka and coworkers have summarized on a figure the impact of
different kinds of technological processes for olive oil extraction, on the phenolic
concentration of the final product (Gorzynik-Debicka et al. 2018). Their research
shows that ‘virgin olive oil’ contains the highest level of polyphenols: generally, it
can range between 150 and 400 mg/kg, while refined olive oil has a low polyphenolic
contribute to flavour (given they are polar and thus mostly eliminated in the water fraction); many
different preparation of table olives include a debittering step.