2009_Book_FoodChemistry

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-phenylethylamine,
tyramine, dopamine,
noradrenaline, serotonin
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 0.2 to5.0% of the fresh
weight (D-manno-heptulose, D-talo-heptulose, D-
glycero-D-galacto-heptose, D-glycero-D-mannooctulose,
D-glycero-L-galacto-octulose, D-erythro-L-gluco-nonulose
and D-erythro-L-galactononulose).
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.
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 vegetables a
Fruit/ Serotonin Tryptamine Melatonin
Vegetable (mg/kg) (mg/kg) (ng/kg)
Banana 11.7 0.03 466
Kiwi 6.2 4.2
Pineapple 29.0 1.4
Cherry 2–15
Walnut 278.9
Cucumber 86
Tomato 2.9 112–506
a Reference: fresh weight.
18.1.2.2.2 Oligosaccharides
Saccharose (sucrose) is the dominant oligosaccharide.
Other disaccharides do not have quantitative
importance. Maltose occurs in small amounts
in grapes, bananas and guava. Melibiose, raffinose
and stachyose have also been detected in
grapes. 6-Kestose has been identified in ripe bananas.
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 in Rosaceae fruits (pomme
fruits, stone fruits). For example, its concentration
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 occurs
in fruits; in orange juice it ranges from 130–
170 mg/100ml.