184
4-hydroxy-2- alkenals are formed, of which 4-hydroxy-2-alkenals is a known precursor for furan formation [36]. Study on monounsaturated fatty acid, for example,
oleic acid, show no furan is produced. While linoleic acid and linolenic acid produce furan, measured as 125 and 625 ng/g, respectively. The reaction was carried
out at 118 °C for 30 min and concluded that linolenic acid required a lower temperature to form furan from that of ascorbic acid or Maillard reaction [37]. Fatty acids
containing furan rings actively search for radical to react and form dioxoenoic fatty
acids. These dioxoenoic fatty acids are highly unstable and cannot exist on their
own, therefore react with thiol, in particular cysteine or glutathione and form thioethers [38]. They trap specifically hydroxyl radicals as powerful antioxidants and
this is regarded as their main function in different biological systems [39]. They also
inhibit red blood cell haemolysis caused by singlet oxygen (disintegration of
RBCs) [38].
Furan Formation Through Degradation of Carbohydrates
Furan is detected to be formed in large number in food processing as a result of nonenzymatic browning reaction as well as Maillard reaction using carbohydrate as
precursors. In the presence of amino acids Maillard reaction took place and produce
intermediates 1-deoxy- and 3-deoxyosones, 2-deoxy-3-keto-aldotetrose and aldotetrose by reduction of hexoses [33]. Some studies suggested 2-deoxy-aldotetrose
and aldotetrose as furan precursor because furan is easily formed by aldotetrose.
Furan is also produced from pentose sugar in the presence of amino acids, the reaction of pentose sugar, for instance, ribose leads to the formation of intermediate
2-deoxyaldotetrose, a precursor of furan. Furan formation from carbohydrates via
thermal degradation is a complex process and it involves many pathways but mostly
involve Maillard reaction.
In the absence of amino acid furan in formed from intact sugar skeleton. In this
process of furan formation formic acid and acetic acid are formed as by-products as
a result of sugar degradation. In this case aldotetrose is also formed to a lesser extent
by retro-aldol cleavage [40]. In this degradation process aldotetrose derivatives produced as intermediate, which go to cyclisation process to produce furan [33].
Pathway A and D explains furan formation process in presence of amino acids,
whereas pathway B illustrates the furan formation in absence of amino acids. Furan
is eventually formed from all aldotetrose derivatives [33]. The parent furan may also
be produced by pentose sugars such as ribose in the proximity of amino acids.
Similar to pentose rings, hexoses can be transformed into their 3-deoxyosone derivative products via reaction of amino acid or by dehydration in the hydroxyl group
C-3 [41]. The resultant intermediate may endure α-dicarbonyl cleavage to generate
2-deoxyaldotetrose, a direct furan precursor.
S. Muzammil et al.
4-hydroxy-2- alkenals are formed, of which 4-hydroxy-2-alkenals is a known precursor for furan formation [36]. Study on monounsaturated fatty acid, for example,
oleic acid, show no furan is produced. While linoleic acid and linolenic acid produce furan, measured as 125 and 625 ng/g, respectively. The reaction was carried
out at 118 °C for 30 min and concluded that linolenic acid required a lower temperature to form furan from that of ascorbic acid or Maillard reaction [37]. Fatty acids
containing furan rings actively search for radical to react and form dioxoenoic fatty
acids. These dioxoenoic fatty acids are highly unstable and cannot exist on their
own, therefore react with thiol, in particular cysteine or glutathione and form thioethers [38]. They trap specifically hydroxyl radicals as powerful antioxidants and
this is regarded as their main function in different biological systems [39]. They also
inhibit red blood cell haemolysis caused by singlet oxygen (disintegration of
RBCs) [38].
Furan Formation Through Degradation of Carbohydrates
Furan is detected to be formed in large number in food processing as a result of nonenzymatic browning reaction as well as Maillard reaction using carbohydrate as
precursors. In the presence of amino acids Maillard reaction took place and produce
intermediates 1-deoxy- and 3-deoxyosones, 2-deoxy-3-keto-aldotetrose and aldotetrose by reduction of hexoses [33]. Some studies suggested 2-deoxy-aldotetrose
and aldotetrose as furan precursor because furan is easily formed by aldotetrose.
Furan is also produced from pentose sugar in the presence of amino acids, the reaction of pentose sugar, for instance, ribose leads to the formation of intermediate
2-deoxyaldotetrose, a precursor of furan. Furan formation from carbohydrates via
thermal degradation is a complex process and it involves many pathways but mostly
involve Maillard reaction.
In the absence of amino acid furan in formed from intact sugar skeleton. In this
process of furan formation formic acid and acetic acid are formed as by-products as
a result of sugar degradation. In this case aldotetrose is also formed to a lesser extent
by retro-aldol cleavage [40]. In this degradation process aldotetrose derivatives produced as intermediate, which go to cyclisation process to produce furan [33].
Pathway A and D explains furan formation process in presence of amino acids,
whereas pathway B illustrates the furan formation in absence of amino acids. Furan
is eventually formed from all aldotetrose derivatives [33]. The parent furan may also
be produced by pentose sugars such as ribose in the proximity of amino acids.
Similar to pentose rings, hexoses can be transformed into their 3-deoxyosone derivative products via reaction of amino acid or by dehydration in the hydroxyl group
C-3 [41]. The resultant intermediate may endure α-dicarbonyl cleavage to generate
2-deoxyaldotetrose, a direct furan precursor.
S. Muzammil et al.