Food Biochemistry and Food Processing (2 edition)

BLBS102-c27 BLBS102-Simpson March 21, 2012 13:25 Trim: 276mm X 219mm Printer Name: Yet to Come

550 Part 5: Fruits, Vegetables, and Cereals

Phenylalanine

p-Coumaryl-CoA p-Coumaric acid

Coumaryl-CoA ligase

Chalcone synthase

Chalcone

Malonyl-CoA

(3)

Acetyl-CoA

Glycolysis

Glucose

Chalcone isomerase

Naringenin

Flavonol hydroxylase

Dihydroquercetin Dihydrokaempferol Dihydromyricetin

Leucodelphinidin

Leucopelargonidin

Anthocyanin

Leucocyanidin

Cyanidin Pelargondin Delphinidin

Trans-cinnamic acid

Cinnmate-4-hydroxylase

Phenylalanine ammonia lyase

Anthocyanin biosynthetic pathway

Dihydroflavonol-4-reductase

Anthocyanin synthase

3-Glucosyl transferase

Methyl transferase

Figure 27.7.Anthocyanin biosynthetic pathway in plants.

so on. The organic acid moiety containing the CoA group can

vary in chain length from C2 (acetyl) to C12 (dodecanoyl). AAT

activity has been identified in several fruits that include banana,

strawberry, melon, apple and so on. In banana, esters are the

predominant volatiles enriched with esters such as acetates and

butyrates. The flavour may result from the combined perception

of amyl esters and butyl esters. Volatile production increases

during ripening. The components for volatile biosynthesis may

arise from amino acids and fatty acids. In melons, the volatile

components comprise esters, aldehydes, alcohols, terpenes and

lactones. Hexyl acetate, isoamyl acetate and octyl acetate are the

major aliphatic esters. Benzyl acetate, phenyl propyl acetate and

phenyl ethyl acetate are also observed. The aldehydes, alcohols,

terpenes and lactones are minor components in melons. In mango

fruits, the characteristic aroma of each variety is based on the

composition of volatiles. The variety “Baladi” is characterised

by the presence of high levels of limonene, other monoterpenes

and sesquiterpenes, and ethyl esters of even numbered fatty

acids. By contrast, the variety “Alphonso” is characterised by

high levels of C6 aldehydes and alcohols (hexanal, hexanol) that

may indicate a high level of fatty acid peroxidation in ripe fruits.

C6 aldehydes are major flavour components of tomato fruits

as well. In genetically transformed tomatoes (antisense PLD),

the evolution of pentanal and hexenal/hexanal was much higher