CHANGES IN DISSOLVED-OXYGEN AND MICROFLORA DURING FERMENTATION OF AERATED, BRINED CUCUMBERS

Dissolved oxygen (DO) and oxygen uptake rates (OUR) were measured in cucumbers that were brined in 5‐gal pails according to the controlled fermentation process. Saturation levels of oxygen in the brines were 5‐6 ppm depending on salt concentration and temperature. DO was expressed as % saturation (% Cs). Either air or nitrogen was used to purge CO, from the brines to prevent bloater formation. In continuously aerated (air‐purged) brines, DO increased before the onset of microbial growth (ca 2 days) and then decreased, converse to OUR. Thus, there were two distinct stages of oxygen levels and uptakes. In nitrogen‐purged brines, DO was negligible throughout the period of purging; OUR of the brine samples was low (1% Cs/min maximum during the microbial fermentation stage) and lactic acid bacteria predominated the microbial flora. In air‐purged brines, DO varied with rate of aeration; OUR of brine samples was high and populations of film yeasts were high. High aeration rates (100 ml/min/gal cucumbers) resulted in lower DO, higher OUR (40% Cs/min maximum) and greater populations of film yeasts than lower aeration rates (2‐5 ml/min/gal). Tests in commercial tanks confirmed that appreciable levels of oxygen are incorporated into brines using a side‐arm purger. Copyright © 1979, Wiley Blackwell. All rights reserved