Organic acids evolution in corn silage

This research was carried out to study the evolution of organic acids content during ensiling process of whole plant maize in three different conditions: inoculation of Lactobacillus buchneri, control and disinfection with sodium hypochlorite. Chopped whole crop maize was ensiled in vacuum polyethylene bags (0.9-1.0 kg per bag) with inoculation of L. buchneri, without it and disinfected with sodium hypochlorite. Three silos per treatment were frozen until analysis at -20°C after 0, 12, 24, 48 hour and after 4, 8, 16 and 30 days (72 samples). Immediately after defrosting simultaneous determination of lactic, acetic, propionic, butyric aconitic, malic, citric and fumaric acids was performed. Data were analyzed by using the GLM procedure of SPSS. Plant organic acids (aconitic, malic, citric and fumaric) lowered their concentration during ensiling process but malic, starting from 8 days after ensiling, kept on increasing until 30 days. Major organic acid found at the end of the process was lactic acid but its faster accumulation rate was recorded on first 48 hours in inoculated and control thesis when pH dropped under value 4. In disinfected samples pH lowered more slowly and its decrease was clear only after 24 hours when also lactic acid began to increase. After 8 days, in inoculated samples, lactic acid concentration decreased while acetic acid increased. We concluded that major cause of lactic acid production was not bacterial fermentations but enzymatic glycolysis by plant cell enzymes. Treating whole-plant corn with L. buchneri resulted in increased concentrations of acetic acid and decreased concentration of lactic acid when compared with untreated corn silage. Sodium hypochlorite did not blocked only fermentations but retard also enzymatic glycolysis. Interesting is the rise of malic acid content which was ascribed to a new production during ensiling process despite preservation of initial cell plant content.[...]