A sterilization technique with applications to silage research and inoculant evaluation

Different techniques were tested to sterilize grass samples with respect to epiphytic microflora (lactic acid bacteria, enterobacteria, yeasts and moulds) to enable study of specific microfloras. Methods tested on freshly harvested grass samples included sterilization efficacies of ethanol, combined effects of ethanol and sodium hypochlorite, neutral detergents and cold shock. The antimicrobial properties of moist and dry heat were also tested, although on freeze-dried samples to minimize the extent of Maillard reactions. Sterilization efficacy was evaluated by culture-dependent microbial analysis. Heat was found to be the best antimicrobial agent. Moist heat (autoclaving) produced chemical changes including a fivefold increase in concentration of acid detergent insoluble nitrogen and reduced pH value. The results suggest that dry heating of dried samples before reconstituting to original dry-matter content could be a promising sterilization technique. Fine-tuning the technique and testing the ensilability of reconstituted samples are the next steps to be undertaken.