Biochemistry of Fruits and
vegetables

Biochemistry of Fruits and Vegetables
• Plant metabolites
• Nutritional and functional properties
• Primary metabolites
• CHO, Protein, Lipids
• Involved in growth and development
• Human Nutrition
• Secondary metabolites
• Nutraceutical and functional properties

Overview of CHO
metabolism in fruits
During glycolysis, breakdown
of sugars occurs to generate
the energy required for
ripening
Invertase
Main storage sugars, depends on fruit/veg. variety, etc.
Major sugar: Sucrose, glucose and fructose
Major polysaccharide: Starch
Minor: mannitol and sorbitol (Apple, olive)

Lipids Metabolism
• Lipids biosynthesis
• Fruits – Avocado and olives
• In avocado, lipids are stored as reserve components in the indioblast, a
specialized cell type of the mesocarp in form of triglycerides
• Veg. – Pulses, oil seed crops
• Lipid metabolism is an important part of the ripening process in fruit
• The main FA in triglycerides are palmitic (16:0), palmitoleic (16:1), oleic
(18:1), and linoleic (18:2) acids. Oil content increases during ripening,
and oils are compartimentalized in oleosomes.
• Part of cellular membranes
• Wax Synthesis and Deposition

PIGMENTS IN FRUITS
• In nature, there are three major classes of pigments:
• Green Chlorophylls
• Chl content increases during green stages and diminishes through maturation,
paralleling chloroplast disintegration, process known as degreening
• carotenoids providing yellow to red color, and
• large group of over 700 structures
• hydrophobic nature, these pigments are found in association with lipid–protein
complexes
• anthocyanins responsible for the red, blue, and violet color
• class of flavonoids derived from phenylalanine, are water-soluble, synthesized in the
cytosol, and localized in vacuoles, where pH may vary its structure and color
• Combination & diversity determine visual aspect of the fruit and their
attraction to insects and other animals to ensure seed dispersal

Secondary Metabolites
• Not required for normal growth and development, and are not made
through metabolic pathways common to all plants.
• 40,000 metabolites
Terpenoids
• repetitive fusion of branched 5‐carbon isoprene units
• have diverse functional roles in plants as structural components of
membranes (sterols), photosynthetic pigments, ETC, hormones
• Food, pharmaceutical, and chemical industries, biofuel products
• Examples: carotenoids, tocopherols and tocotrienols, quinones, sterols,
sapogenins, and essential oils

Secondary Metabolites
Carotenoids
• largest group of natural dyes
• Some have pro‐vitamin A activity
• Antioxidant activity
Tocopherols and Tocotrienols
• 4 homologues (α, β, γ, and δ), vit. E

Quinones

Phytosterols
• Sitosterol, sitostanol, campesterol,
brassicasterol, and stigmasterol
• calciferol

Phenolic Compounds
• Plant phenolic compounds include around 10,000 metabolites
• characterized by having at least one aromatic ring bearing one or
more hydroxyl groups attached
• Examples: Phenols, phenolic acids, phenylacetic acids,
hydrohycinnamic acids, naphthoquinones, xanthones, flavonoids,
lignans, bioflavonoids, lignins and condensed tannins
• also be classified in simple phenols (phenolic acids and coumarins)
and polyphenols (flavonoids and nonflavonoids)

Classification of phenolic compounds
most widespread group of
pigmented flavonoids
responsible for most of the
red, pink, purple, and blue
colors observed in
vegetables, fruits, and flowers

Alkaloids
• physiological and medicinal properties
• caffeine, nicotine, morphine, atropine, quinine
Sulfur‐Containing Compounds
Antioxidants
Organic Acids
• Organic acids are among the principal compounds in the
fruits producing a sour sensation or acidity
• major OA in most fruits are malic and citric acids – Preservation

Effects of processing and storage of food
• Water-soluble vitamins (B-group and C) are more unstable than fat-
soluble vitamins (K, A, D and E) during food processing and storage.
The most unstable vitamins include:
• folate
• thiamine
• vitamin C.
• More stable vitamins include:
• niacin (vitamin B3)
• vitamin K
• vitamin D
• biotin (vitamin B7)
• pantothenic acid (vitamin B5).

Effect of processing on vit. C content in selected
vegetables
Carotenoids losses in green leafy vegetables during
processing
Losses in antioxidant
activity of some
vegetables

The nutritional losses during canning can be minimized by using
following guidelines