26
2 Polyphenols as Bioactive Compounds in Foods and Food Supplements
greens, brussels sprouts, etc. Also, garlic and onion contribute with cysteine sulfoxides of four types: alliin, methiin, propiin, and isoalliin. Onions are especially
rich in isoallin, whereas garlic is rich in alliin (Batchu et al. 2013). According to
the same authors, organosulfur compounds decrease ROS levels by inhibiting
ROS generating system.
2.2 Polyphenols and the Colour of Foodstuffs
Colour is also a marker of the presence of polyphenols, as many of them render the
colour to plants (Cheynier et al. 1998). These classes of natural pigments have been
studied by many authors.
Deng and colleagues studied the phenolic composition of a series of rice sample
pigments (Deng et al. 2013). In their paper, they demonstrated that pigmented rice
varieties contain a wide range of phenolic compounds including anthocyanins, proanthocyanidins, 4-hydroxycinnamic acid, 4,7-dihydroxyvanillic acid, syringaldehyde,
vanillin, the group of p-coumaric, ferulic, sinapinic acids, etc. (Chung and Woo 2001;
Deng et al. 2013; Hu et al. 2003). The presence of quercetin and isorhamnetin was
identified in black rice (Nakornriab et al. 2008).
Anthocyanins represent the group of flavonoids acting as pigments with reddish
to purple colour. Cyanidin 3-glucoside is reported to be the most abundant anthocyanin in black rice and red rice (88 and 67% of the total anthocyanins, respectively)
followed by peonidin 3-glucoside, while cyanidin diglucoside was the third major
anthocyanin in same coloured rice grains (Abdel-Aal et al. 2006; Deng et al. 2013).
Deng and coworkers also reported that phenolic acids (i.e. ferulic acid) are implicated
in conferring colour to rice. Similar results have been reported by other researchers
(Vichapong et al. 2010; Yawadio et al. 2007; Zhou et al. 2004).
Shoji discusses chemical and enzymatic reactions of phenolic compounds in foods
with reference to colour (Shoji 2007). Hence, he classified polyphenols into two
groups: (i) non-flavonoids, which include mainly phenolic acids, stilbenes, gallotannins and lignins and (ii) flavonoids. Shoji reported that non-flavonoids are colourless
or slightly brownish; consequently, their role in food pigmentation is negligible. However, flavonoids play an important role in determining the colour of foods and drinks
(Shoji 2007). Anthocyanin tops the list of natural phenolic compounds involved in
food pigmentation in a wide range of colours: red, orange, purple and blue. Colours
given by anthocyanin depend on pH, temperature, oxygen level, the concomitant
presence of other polyphenols and metal ions, light and certain enzymes. Such features although undesirable in certain cases (browning of fruit juices) may found
uses, for example, in intelligent packaging, in displaying changes suffered by foods.
Polymerization reactions have shown to be involved in the redefinition of new colorimetric coating of red wines. Such polymerizations implicate mainly anthocyanins
and the development of new colours of some processed food. Shoji reported the
2 Polyphenols as Bioactive Compounds in Foods and Food Supplements
greens, brussels sprouts, etc. Also, garlic and onion contribute with cysteine sulfoxides of four types: alliin, methiin, propiin, and isoalliin. Onions are especially
rich in isoallin, whereas garlic is rich in alliin (Batchu et al. 2013). According to
the same authors, organosulfur compounds decrease ROS levels by inhibiting
ROS generating system.
2.2 Polyphenols and the Colour of Foodstuffs
Colour is also a marker of the presence of polyphenols, as many of them render the
colour to plants (Cheynier et al. 1998). These classes of natural pigments have been
studied by many authors.
Deng and colleagues studied the phenolic composition of a series of rice sample
pigments (Deng et al. 2013). In their paper, they demonstrated that pigmented rice
varieties contain a wide range of phenolic compounds including anthocyanins, proanthocyanidins, 4-hydroxycinnamic acid, 4,7-dihydroxyvanillic acid, syringaldehyde,
vanillin, the group of p-coumaric, ferulic, sinapinic acids, etc. (Chung and Woo 2001;
Deng et al. 2013; Hu et al. 2003). The presence of quercetin and isorhamnetin was
identified in black rice (Nakornriab et al. 2008).
Anthocyanins represent the group of flavonoids acting as pigments with reddish
to purple colour. Cyanidin 3-glucoside is reported to be the most abundant anthocyanin in black rice and red rice (88 and 67% of the total anthocyanins, respectively)
followed by peonidin 3-glucoside, while cyanidin diglucoside was the third major
anthocyanin in same coloured rice grains (Abdel-Aal et al. 2006; Deng et al. 2013).
Deng and coworkers also reported that phenolic acids (i.e. ferulic acid) are implicated
in conferring colour to rice. Similar results have been reported by other researchers
(Vichapong et al. 2010; Yawadio et al. 2007; Zhou et al. 2004).
Shoji discusses chemical and enzymatic reactions of phenolic compounds in foods
with reference to colour (Shoji 2007). Hence, he classified polyphenols into two
groups: (i) non-flavonoids, which include mainly phenolic acids, stilbenes, gallotannins and lignins and (ii) flavonoids. Shoji reported that non-flavonoids are colourless
or slightly brownish; consequently, their role in food pigmentation is negligible. However, flavonoids play an important role in determining the colour of foods and drinks
(Shoji 2007). Anthocyanin tops the list of natural phenolic compounds involved in
food pigmentation in a wide range of colours: red, orange, purple and blue. Colours
given by anthocyanin depend on pH, temperature, oxygen level, the concomitant
presence of other polyphenols and metal ions, light and certain enzymes. Such features although undesirable in certain cases (browning of fruit juices) may found
uses, for example, in intelligent packaging, in displaying changes suffered by foods.
Polymerization reactions have shown to be involved in the redefinition of new colorimetric coating of red wines. Such polymerizations implicate mainly anthocyanins
and the development of new colours of some processed food. Shoji reported the