Growth Characteristics of Aciduric Sporeforming Bacilli Isolated from Fruit Juices

Abstract

Two aciduric, aerobic, sporeforming bacteria were isolated from pasteurized juices. The gram-positive, catalase-positive rods produced spores that were located subterminally in a swollen sporangium. The cultures had an optimal pH of 3.5-4.0 for growth and preferred potato dextrose agar over many of the rich media usually used for cultivating sporeforming bacteria. Spore inocula grew well in apple juice and white grape juice. Red grape juice was inhibitory, perhaps because of the concentrations of certain phenolic compounds. The spores were sufficiently heat resistant (D₉₀ values of 16 to 23 min and z-values of 7.2 to 7.7°C) to survive commercial pasteurization processes.

Keywords: Aciduric spores; fruit juices; spoilage.