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Assessment of the microbiological status of raw material for the european leather industry

Exploitable results

Initial research on raw hides showed that using UV light with a wavelength of 254nm for 30 seconds was the optimum exposure time for practical use within the leather industry. Long term trials comparing hides preserved using 40% salt only and hides stored exposed to UV and salt offers of either 20 or 40%. The results show that UV exposure results in a reduction of bacteria numbers, although in this trial, numbers increase in the second month, probably due to the salt itself being a significant bacteria source. With regards to the leather industry, the results show that UV radiation significantly reduces collegenase-producing bacteria that are known to cause skin degradation. Raw skin exposed to UV radiation, when processed are shown to have a higher tear strength
Trisodium Phosphate(TSP), nisin, chilling and boric acid were assessed individually and in conjunction with salt (at reduced offers) to determine their suitability as an alternative preservation method to salt, for the preservation of raw skins. The results showed that at a TSP concentration of 10%, in addition to either a 10 or 20% salt application, reduced bacteria numbers were observed. The current high commercial cost of TSP would however limit its use in the industry. Analysis of nisin determined that 0.248µg/cm2 was the most effective nisin load to reduce bacteria numbers and nisin treatment resulted in a 1-1.5 log reduction in bacterial numbers. In addition the trial also determined that nisin and salt offers similar or better protection against bacterial attack compared with salt alone. Nisin seems to be particularly effective against Pseudomonas bacteria species. The results from analysis of boric acid showed that it was not effective at reducing total bacteria numbers or collegenase producing bacteria. The effects of temperature control showed that at 37 degrees Celsius bacterial numbers proliferate immediately after slaughter. Reducing the temperature to 20 degrees Celsius provides a window of up to 8 hours before any significant increase in the bacteria. Cooling to 4 degrees Celsius extends this time to in excess of 24- hours.