The use of irradiation for the preservation of fresh herbage for subsequent botanical and chemical analysis

The use of irradiation as a means of preserving fresh forage for subsequent botanical and chemical analysis was examined as a possible alternative to preservation by freezing. Forage samples containing a mixture of grass species were given irradiation doses of either 2-5 Mrad (25 k Grays) or 5-0 Mrad (50 k Grays). These samples were then stored in the dark under either ambient or chill (+ 2°C) conditions for up to 5 months, while similar samples of fresh forage were stored over the same period deep frozen at — 15°C. No spoilage or signs of any subsequent senescence were observed in the forage given the 5-0 Mrad irradiation treatment during the 5 month storage period. In the 2-5 Mrad treated material some browning of lamina tips occurred. However, the irradiation treatment did cause some colour changes, mainly a darkening of the green tissue. The state of preservation was also assessed by measuring the rate at which stored herbage could be separated into the constituent species. No difference in separation rates was found between samples that had either been stored frozen or irradiated at 5-0 Mrad (and then stored under either ambient or chill conditions); however, separation rates were slower on the 2-5 Mrad treated samples. The irradiation treatment did not cause any significant change in percent nitrogen content. However, water-soluble carbohydrate contents in the irradiated samples were significantly lower. The cost of commercial irradiation treatment was less than 20% of the commercial cost of freezing and cold storage.