Changes in Water‐Soluble Calcium and Magnesium Content of Pear Fruit Tissue During Maturation and Ripening in Relation to Changes in Pectic Substances

Abstract

SUMMARYChanges were determined in total and water‐soluble calcium and magnesium content and in the pectic substances of Bartlett pears during maturation and storage. The data indicate a change in metabolic processes when the fruit is removed from the tree. In maturing fruit, about 48% of calcium and 65% of magnesium are present in soluble form. Both cations generally decreased during maturation. The Mg/Ca ratio varied with growing conditions and may be related to soil composition. The data indicate that mare, total pectin, water‐soluble pectin, total calcium, and total magnesium arc correlated with firmness. The relationship of soluble calcium and magnesium to firmness is radically different in detached fruit from that in fruit on the tree. Analyses of data indicate that the “bound” calcium and magnesium are present in concentrations far greater than the total available carboxyl groups of pectin, and that protopecin content is not related to calcium‐ or magnesium‐bound pectinic acid chains. In detaching ripening fruit, when a general breakdown begins there is a good correlation of all data with firmness.

Changes in Water Soluble Polyuronides in the Pulp Tissue of Ripening ‘Bosc’ Pears following Cold Storage in Air or in 1% Oxygen

“…5). This phenomenon agreed with the normal ripening and softening behavior of a number of fruit species (2,4,10,11,14). The increased WSP was negatively correlated with EJ during each ripening period (Table 1).…”

Relationships of Histological Structure to Texture of Fresh and Processed Fruits and Vegetables

“…Various pectic enzymes are involved in the sequence of pectic changes associated with fruit softening on ripening. Other cell wall substances, such as hemicelluloses and lignins, also undergo changes during ripening in some fruits (Coggins et al, 1968;Esau et al, 1962;Jermyn and Isherwood, 1956;Weurman, 1954). Cell wall composition and pectic enzymes are important to texture in fruits commonly used as vegetables.…”

Shelf Life Evaluation of Bartlett Pears in Retort Pouches

“…Typically, Bartlett pears are harvested at full size in hard, green condition, shipped in bins to the cannery and held under controlled temperature, ripened at elevated temperature or with ethylene gas to a penetrometer test of 0.9-1.35 kg They are then size graded, mechanically or lye peeled, washed, halved and cored, sorted, filled into cans, syruped, steam exhausted, closed, processed at atmospheric pressure and cooled. Previous research has considered several quality factors: pre-and post-harvest maturation, pectin chemistry and calcium and magnesium content (Esau et al, 1962); instrumental texture profiling of ripening pears, relating readings of the Magnuson-Taylor pressure tester with the General Foods Texturometer and Instron (Bourne, 1968); polyphenol oxidase (Tate et al, 1964); and various methods of recovering pear aroma essence during processing for addback (Heinz et al, 1964).…”