Fungal Growth and Acid Production During Fermentation and Refermentation of Organic Acid Treated Corn Silages

Abstract

Chopped corn (35% dry matter) treated with either propionic, formic, 60% propionic plus 40% formic, or 80% propionic plus 20% acetic acids at 0, .5, 1, and 2%, was placed in polyethylene bags inside metal drums, and evacuated. During fermentation silages were sampled and temperatures determined. On day 40 of fermentation silages were placed in open containers at 25 C and were sampled during refermentation. All samples were analyzed for volatile and lactic acids, pH, and number and type of fungi. Lactate fermentation was totally inhibited at 2% addition of all acids, but formic acid was more effective than propionic acid at .5 and 1%. Acetate production was equally depressed by both propionic and formic additions. Heating, growth of fungi, and days until spoilage were delayed by all acid additions during refermentation, with propionic more effective than formic. The large increases in lactate and acetate of treated silages during refermentation reflect a protection of soluble sugars during fermentation and subsequent use by microbes after exposure to air. Silages treated with more than 1% propionic (as propionic or a mixture) did not increase in fungal colonies during refermentation. At initiation of fermentation yeasts were higher than other fungi but decreased by day 40. During refermentation, yeasts again grew. Geotrichum comprised 35% on day 40 of refermentation but was lower at other times. Aspergillus proliferated during refermentation and few Penicillium were detected. © 1975, American Dairy Science Association. All rights reserved.