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B. Fils-Lycaon and M. Buret

Pectic fractions soluble in water, oxalate, or hydrochloric acid were prepared from an alcohol-insoluble residue of cherry (Prunus avium L., `Bigarreau Napoléon') tissue. Galacturonic acid and neutral sugar contents were measured during the ripening and overripening of fruit. Fruit firmness was also determined. The changes occurring during fruit development gave prominence to three physiological stages and suggested the progressive degradation of the middle lamella and primary cell wall. The firmness measurement was related to the equilibrium between the relative parts of these pectic fractions.

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J.J. Mangas, E. Dapena, M.S. Rodriguez, J. Moreno, M.D. Gutiérrez, and D. Blanco

Water-soluble pectin (WSP), chelator-soluble pectin (CSP), and hydrochloric acid-soluble pectin (HASP) were monitored in five Asturian apples (Malus domestics Borkh.) throughout ripening. The alcohol-insoluble solid content was found to decrease during ripening, while those of the WSP and CSP fractions increased in the final stages of ripening. This increase was probably at the expense of the HASP content, which had decreased by the end of the ripening period.

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Eleni Tsantili, Miltiadis V. Christopoulos, Constantinos A. Pontikis, Pantousis Kaltsikes, Chariklia Kallianou, and Michalis Komaitis

50 mL petroleum ether for 6 h. Fruit pectic fractionation and analysis. Pectic fractionation was carried out according to Gallardo-Guerrero et al. (2002) after some modifications. In particular, the alcohol-insoluble solids (AIS) were

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Joshua D. Klein, Susan Lurie, and Ruth Ben-Arie

`Anna' and `Granny Smith' apples (Malus domestics Borkh.) that were held at 38C for 4 days before storage at 0C not only were firmer than controls upon removal from storage, but also softened more slowly during shelf life at 17C. Skin yellowing and loss of acidity attendant upon the heat treatment were not prevented by dipping fruit in 2% CaCl2 before heating. Both heat-treated and control fruit softened at the same rate upon exposure to ethylene at 100 μl·liter-1 upon removal from storage. The insoluble pectin content of cortical tissues was higher in heat-treated fruit than in controls after 10 days at 17C, while soluble pectin levels were lower. Arabinose and xylose levels were lower in cell walls from heat-treated cortical tissue, but the treatment had no effect on loss of galactose residues during shelf life.

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JD Klein, J Hanzon, PL Irwin, S Lurie, and N Ben Shalom

Prestorage heating of apples lead to enhanced retention of fruit firmness of as much as 10 N upon removal from storage, compared to unheated fruit. Further enhancement of firmness retention was obtained by dipping fruit in 2-3% calcium chloride after heating prior to storage. Cortical tissue of heated fruit had more insoluble and less water soluble pectin than unheated fruit, although the total pectin content was similar in both treatmenats. During the heat treatment neutral sugars were lost from the pectic fractions, with no accompanying decrease in galacturonic acid. No effect of heat treatment on degree of methyl esterification was observed in pectic fractions or in critical-dried whole tissues, using colorimetric and NMR techniques, respectively. Treatment differences in dissolution of the middle lamella were not observable in electron micrographs. We suggest that loss of neutral sugar side chains during the heat treatment may have lead to closer packing of the pectin strands and in turn hindered enzymatic cleavage during and after storage.

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Marius Huysamer, L. Carl Greve, and John M. Labavitch

Discs from outer pericarp of mature green (MG) and light red (LR) tomatoes were incubated with 13C6-glucose as precursor to cell wall constituents, to determine biosynthetic capacity of the outer 2mm (including cuticle) and adjacent inner 2mm of tissue. Cell wall material was fractionated into pectic and hemicellulosic classes by sequential extraction, and alditol acetates and partially-methylated alditol acetates were prepared. Neutral sugars (NS), glycosidic linkage compositions and incorporation of label were determined by GC-FID and GC-MS. Rhamnose, arabinose and galactose accounted for ca. 90% of both labeled and total NS in the pectic fractions (sugar ratios within ripeness stage were the same for labeled and total NS). Xylose and glucose accounted for ca. 70% of both labeled and total NS in the hemicellulosic fraction (sugar ratios within ripeness stage were different between labeled and total NS). In the crude cell wall, galactose and glucose contents were significantly higher in the inner than in outer tissues for both MG and LR tomatoes. Loss of galactose during ripening was higher from outer tissues. These results show compositional differences between inner and outer tissues, and suggest that ripening-related wall synthesis may give rise to pectic polymers similar in NS composition to existing polysaccharides, and hemicellulosic polymers which may differ in composition.

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Meng Li, Huanhuan Zhi, and Yu Dong

-Lycaon, B. Buret, M. 1990 Loss of firmness and changes in pectic fractions during ripening and overripening of sweet cherry HortScience 25 777 778 Hansen, M. 2010 Searching for cherry cracking strategies Good Fruit Grower 61 16 18 Ingalsbe, D.W. Carter, G

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Sokrith Sea, Cyril Rakovski, and Anuradha Prakash

because ripening had already been started in the late-harvest pears but in general, the irradiated pears were significantly more firm than the control ( P < 0.05). The conversion of insoluble pectic fractions to the soluble forms by protopectinase and

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Sima Panahirad, Rahim Naghshiband-Hassani, Babak Ghanbarzadeh, Fariborz Zaare-Nahandi, and Nasser Mahna

reduces soluble pectic fractions and retards conversion of insoluble pectins to soluble ones ( Hussain et al., 2010 , 2015 ). Polygalacturonase, pectin-methylesterase, 1,4-β-D-glucanase/glucosidase, and β-galactosidase are the main enzymes that cause