Development of Microbial Populations in Fermented Wastes from Frozen Vegetable Processing

Abstract

Changes in microbial populations were evaluated in fermented silage-like products prepared from wastes generated during frozen vegetable processing. Lactobacillus plantarum (107/g) was used to inoculate wastes from black-eyed peas, corn, potatoes, turnip greens and green beans. Populations of facultative anaerobic flora (lactobacilli, lactic acid cocci), anaerobes (clostridia) and lactate-hydrolyzing microflora differed in silages of different composition. Development of microflora correlated with pH decline and production of volatile and nonvolatile acids. Lactic and acetic acids were produced early while secondary metabolic end products (propionic, butyric acids) accumulated later in silages as populations of clostridia and propionibacteria increased. Minimum pH levels were attained after 2 and 4 days of fermentation. Black-eyed pea and potato silages had relatively high pH levels (>4.50). This was correlated with low soluble carbohydrate content. No generalized role could be determined for population changes of fungi or coliforms. The most desirable waste silages can be produced from temperature-stressed materials adjusted to proper composition to ensure optimum fermentation patterns.