Histological Investigations of Texture in Apples.

Abstract

Changes from succulence to mealiness during ripening and storage of apples are important to the marketability of the fresh fruit. These changes also are significant t o the textural qualities of processed apples. Mealy apples frequently sauce readily when cooked. Some varieties sauce rapidly when cooked in the fresh condition ; others remain intact and relatively firm.It has been commoiily accepted that saucing of cooked apples is the direct result of cell separation when the middle lamella pectins are solubilized (7, 12). JIealiness, as a condition of cell separation in fresh apples, has long been coilsidered t o result from pectic changes during ripening and Branfoot ( 1 ) demonstrated that these changes, from insoluble "protopectin" t o vater-soluble pectins, occur in the middle Zaiiiellne betveeii ad jaceiit cells. Apples vary coiisiderably in textural qualities, howeyer : some of the conditions described by Branfoot do not agree v i t h observations made by Tetley (11) and the composition of middle lamellae, in sitii, still remains coii jectural. The exact chemical composition of Braiifoot's "protopectin" is obscure (4,7 ) and the term has little meaning other than its reference to the water-insoluble fraction remored by the C a d -Haynes method ( 2 ) . The soluble fraction, on the other hand, is extracted from the frozen. finely groand tissue and it would be erroneous t o assnme that it represents the vater-soluble pectins of only the middle lamellae.

Effects of pulsed-vacuum and ultrasound on the osmodehydration kinetics and microstructure of apples (Fuji)

“…4a shows the microstructure of fresh, untreated apple tissue, where the apple tissues have well-organized, orderly structure consisting of a high degree of cell compartmentation and intercellular spaces. The intercellular volumes in apples are estimated at 20-25% of the total volume of apple (Reeve, 1953), the greater fractional air volumes in apple endow a softer or more mealy texture property and a greater internal bulk flow and mass diffusion. During osmotic treatment, SEM micrographs showed the breakdown of cell walls, a decreased intercell contact and collapse of cell structure of samples ( Fig.…”

Microstructural changes during osmotic dehydration of parenchymatic pumpkin tissue

“…Several geometrical cellular parameters, previously considered by other authors (Lewicki & Pawlak, 2003;Mayor et al, 2005;Reeve, 1953) were analyzed:…”

Effect of Drying on Microstructure of Plant Tissue

“…The width of the spaces varies from 210 to 350 mm while length was between 438 and 665 mm. [6] The greatest length of intercellular spaces observed by Reeve [6] was reaching 2000 mm. The volume of intercellular spaces measured by vacuum infiltration of water and sucrose solutions is between 19.8 and 35.4% in the middle portion of the apple flesh.…”

“…[7] It was calculated that in 1 cm 3 of apple flesh number of cells can vary from 1.10 Â 10 5 to 3.66 Â 10 5 depending on apple variety. [6] Parenchyma tissue of apple contains intercellular spaces. Nearly all the larger intercellular spaces are radially elongated and have small interconnecting channels.…”

“…The average cell diameter ranged from 161 to 221 mm in outer flesh and from 170 to 235 mm in inner flesh depending on the variety of apple. [6] The standard deviation varied from AE27 to AE58 mm. Many parenchyma cells are slightly elongated but this elongation is not related in any degree to the fruit axis.…”