S. Terasaki et al., Changes in cell wall polysaccharides of kiwifruit and the visco-elastic properties detected by a laser Doppler method, J JPN S HOR, 70(5), 2001, pp. 572-580
Citations number
40
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Plant Sciences
Journal title
JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE
Visco-elastic properties of kiwifruit were measured by a laser Doppler meth
od over an eight day ripening period. After ethylene treatment, fruit flesh
elasticity decreased exponentially. However, viscosity of the flesh increa
sed from day 0 to 2 and then decreased. Fruit tissue was boiled in 80% etha
nol to extract soluble sugars (EtOH fraction); the EtOH-insoluble residue w
as treated with alpha -amylase to solubilize starch. The amount of sucrose,
glucose, fructose and inositol in the EtOH fraction on unit FW basis incre
ased from day 0 to 3, while starch decreased during the ripening period. Ce
ll wall material was fractionated into the hot water-soluble (WS), hot EDTA
-soluble (pectin), alkaline soluble (hemicellulose) and residual (cellulose
) fractions. The quantity of hydrolyzed sugars in the WS fraction decreased
exponentially during ripening, whereas that in the pectin and hemicellulos
e fractions increased slightly on day 1 and then decreased rapidly. The amo
unt of cellulose remained nearly constant during ripening. The iodine metho
d revealed appreciable amounts of xyloglucan in the hemicellulose fraction.
Gel permeation chromatography of polymers in the hemicellulose fraction re
vealed that xyloglucan had degraded rapidly by day 2. The molecular weights
of both total sugar and uronic acid components of the pectin fraction incr
eased from day 0 to 2, and then decreased. The amount of total cell wall po
lysaccharides and starch decreased by 80% during ripening, which indicates
that a decrease in the molecular weight of xyloglucan correlates with a los
s in fruit tissue elasticity, while the changes in the molecular weight of
pectin corresponds with changes in viscosity. A substantial portion of the
cell wall polysaccharides was hydrolyzed to soluble sugars in the early pha
se of ripening.