On the Occurrence of Free-galacturonic Acid in Apples and Tomatoes.

McClendon, John H.; Woodmansee, C. W.; Somers, G. Fred

doi:10.1104/pp.34.4.389

Cited by 15 publications

(4 citation statements)

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“…In order to understand the process, considerably more basic information must be obtained on the chemical changes associated with ripening of these fruits. Information on some of the constituents of the 70% alcohol-soluble fractions are covered in another publication (23). Further knowledge of other polysaccharides in the alcohol-insoluble fractions of these fruits such as starch, sugars, cellulose, and hemicellulose may indicate a role in maintaining firmness and other attributes of good quality.…”

Section: Results a N D Discussionmentioning

confidence: 99%

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CHEMICAL CHANGES ASSOCIATED WITH THE RIPENING OF APPLES AND TOMATOES^a

Woodmansee

McClendon

Somers

1959

Journal of Food Science

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The ripening and eventual softening of fruits is a natural phenomenon. More knowledge concerning the chemical changes associated with ripening is necessary to improve the present handling techniques for maintaining the quality of fruits in fresh market channels. In this study, the chemical changes of several constituents in whole apples and tomatoes were ascertained at the unripe, ripe, and overripe stages of maturity to help explain the softening process.Objective measurements of fruit quality have as their goal the establishment of precise specifications to characterize any given lot of material. For example, measurements such as alcohol-insoluble solids, crude fiber, protein, acid content, and fruit pressure tests have been used by many workers for quantitative evaluation of the nutrition and quality levels of fruits and vegetables (3,5,10, If, 12,18,20,21,26). For many years, changes in the quantity and type (16) of pectic substances have been considered to play a role in ripening and firmness of fruits (7,13,15,19,22,25,27,28). Some evidence suggests that the pectic components of fruits may be hydrolyzed to soluble forms, with accompanying demethylation, and finally to smaller, less complex, units ( 4 ) . The mechanism involved in the transformation of these pectic substances as fruits mature, as well as their function in providing firmness to plant tissues, has not been clearly demonstrated. Older methods for extracting and analyzing pectic substances from plant material have been not entirely free from criticism (15). Recent methods (24) use less drastic extractions with little or no degradation, possibly yielding a product comparable to pectin in situ.This study seeks to provide fundamental information, using reliable methods, for a quantitative evaluation of some chemical changes associated with the maturation process of apples (Red Delicious and Stayman) and tomatoes (Brookston and Valiant). Especial attention is given to the determination and characterization of the pectic constituents. EXPERIMENTAL MATERIALS AND METHODSApple and tomato fruits. The fruits were obtained from orchards and plots at the University Farm during the 1953 and 1954 seasons. They were carefully harvested at the unripe and ripe stages of maturity with the ripe stage allowed to become overripe in the laboratory. Extremely large and small specimens were excluded as well as those with cracks or blemishes. The selection of fruits for analyses at the 3 stages of maturity was on the basis of skin color and firmness. Unripe fruits were full size but essentially green and were hard. Ripe fruits had full color change and were firm. Overripe fruits were similar to ripe, except senescence and softening had taken place, hence special care was required in handling them.

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Section: Results a N D Discussionmentioning

confidence: 99%

“…The insoluble material was dried at 60" C. overnight, ground to pass a 30-mesh screen, and stored in bottles for subsequent analysis. The constituents in the initial alcohol-soluble fractions were considered in another study (23).…”

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confidence: 99%

CHEMICAL CHANGES ASSOCIATED WITH THE RIPENING OF APPLES AND TOMATOES^a

Woodmansee

McClendon

Somers

1959

Journal of Food Science

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“…The organic acids identified in tomato fruits are citric, malic, galacturonic, pyrrolidonecarboxylic, lactic, fumaric, oxalic, aconitic, acetic, and formic (1,2,3,10). Citrate predominates, comprising 40 to 90 percent of the organic acid content, depending upon cultivar, environment, degree of fruit maturity, and postharvest treatment (2,4,5,9,10). Malate concentration ranges from 5 to 60 percent of that of citrate, depending largely on the cultivar (5).…”

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confidence: 99%

“…Concentration of free galacturonate is relatively low, but increases with increasing maturity. The greatest concentration occurs in overripe fruits (9), possibly as a result of breakdown of pectins. Pyrrolidonecarboxylage appears to be an artifact, and apparently is a decomposition product of glutamine and possibly glutamic acid (10).…”

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confidence: 99%