Comparison of the Microstructure of Firm and Stem-End Softened Cucumber Pickles Preserved by Brine Fermentation

Soft and firm stem end tissues of cucumbers fermented at a low concentration of sodium chloride were examined by a combination of light microscopy {LM), transmission electron microscopy { TEM), and scanning electron microscopy { SEM) . When compared to firm tissue, softened tissue cell walls were swollen and striated, and the middle lamellae were poorly stained by the uranyl acetate-1 ead citrate used in TEM . When the tissue was penetrated by a circu l ar punch {1.5 mm diameter), cells in soft tissue tore along the middle l arne ll ae rather than across cell walls, as did cells in firm tissue. Thus, softening was characterized by a weakening of cell-to-cell junctions at the middle lamellae. Ultrastructural changes in the softened tissue were consistent with cellulolytic and / or pectinolytic degradation of cell wall components . Since fungal hyphae were found in both soft and firm tissue, it was not possible to determine if the softening was due to extracellular enzymes produced by invading organisms or to enzymes endogenous to the cucumber tissue. l Paper no. 9772 of the Journal the North Carolina Agricultural Service, Raleigh, NC 27695-7601. Series of Research Initial paper received January 30, 1985. Final manuscript received April 22, 1985. Direct inquiries to W.M. Walter. Telephone number: (919) 737-2990.