Food Chemistry

18.1 Fruits 817

Table 18.6.Amines in fruit

Fruit Amines

Apple Methylamine, ethylamine, propylamine,

butylamine, hexylamine, octylamine,

dimethylamine, spermine, spermidine

Plum/prune Dopamine

Orange Feruloylputrescine, methyltyramine,

synephrine

Grapefruit Feruloylputrescine

Lemon Tyramine, synephrine, octopamine

Pineapple Tyramine, serotonin

Avocado Tyramine, dopamine

Banana Methylamine, ethylamine, isobutylamine,

isoamylamine, dimethylamine,

putrescine, spermidine, ethanolamine,

propanolamine, histamine, 2-phenyl-

ethylamine, tyramine, dopamine,

noradrenaline, serotonin

these biologically active amines in fruits and
vegetables (Table 18.7) could influence their
concentrations in human serum.

(18.4)

Table 18.7.Concentrations of tryptamine, serotonin
and melatonin in fruits and vegetablesa

Fruit/ Serotonin Tryptamine Melatonin
Vegetable (mg/kg) (mg/kg) (ng/kg)

Banana 11. 70. 03 466
Kiwi 6. 24. 2
Pineapple 29. 01. 4
Cherry 2–15
Walnut 278. 9
Cucumber 86
Tomato 2. 9 112–506

aReference: fresh weight.

18.1.2.2 Carbohydrates

18.1.2.2.1 Monosaccharides

In addition to glucose and fructose, the ratios of

which vary greatly in various fruits (Table 18.8),

other monosaccharides occur only in trace

amounts. For example, arabinose and xylose

have been found in several fruits. An exceptional

case is avocado in which a number of higher

sugars are present at 0.2to5.0% of the fresh

weight (D-manno-heptulose,D-talo-heptulose,D-

glycero-D-galacto-heptose,D-glycero-D-manno-

octulose, D-glycero-L-galacto-octulose, D-ery-

thro-L-gluco-nonulose andD-erythro-L-galacto-

nonulose). Small amounts of heptuloses have

been found in the fruit flesh of apples, peaches

and strawberries, and in the peels of grapefruit,

peaches and grapes.

18.1.2.2.2 Oligosaccharides

Saccharose (sucrose) is the dominant oligosac-

charide. Other disaccharides do not have quantita-

tive importance. Maltose occurs in small amounts

in grapes, bananas and guava. Melibiose, raffi-

nose and stachyose have also been detected in

grapes. 6-Kestose has been identified in ripe ba-

nanas.

Other oligosaccharides occur only in trace

amounts. The proportion of reducing sugars to

saccharose can vary greatly (Table 18.8). Some

fruits have no saccharose (e. g., cherries, grapes

and figs), while in some the saccharose content

is significantly higher than the reducing sugar

content (e. g., apricots, peaches and pineapples).

18.1.2.2.3 Sugar Alcohols

D-Sorbitol is abundant inRosaceaefruits (pomme

fruits, stone fruits). For example, its concentra-

tion is 300–800 mg/100ml in apple juice. Since

fruits such as berries, citrus fruits, pineapples or

bananas do not contain sorbitol, its detection is

of analytical importance in the evaluation of wine

and other fruit products. Meso-inositol also oc-

curs in fruits; in orange juice it ranges from 130–

170 mg/100ml.