High pressure processing for food safety

Food preservation using high pressure is a promising technique in food industry as it offers nu-merous opportunities for developing new foods with extended shelf-life, high nutritional value and excellent organoleptic characteristics. High pressure is an alternative to thermal processing. The resistance of microorganisms to pressure varies considerably depending on the pressure range applied, temperature and treatment duration, and type of microorganism. Generally, Gram-positive bacteria are more resistant to pressure than Gram-negative bacteria, moulds and yeasts; the most resistant are bacterial spores. The nature of the food is also important, as it may contain substances which protect the microorganism from high pressure. This article presents results of our studies involving the effect of high pressure on survival of some pathogenic bacteria — Lis-teria monocytogenes, Aeromonas hydrophila and Enterococcus hirae — in artificially contaminated cooked ham, ripening hard cheese and fruit juices. The results indicate that in samples of inves-tigated foods the number of these microorganisms decreased proportionally to the pressure used and the duration of treatment, and the effect of these two factors was statistically significant (lev-el of probability, P ≤ 0.001). Enterococcus hirae is much more resistant to high pressure treatment than L. monocytogenes and A. hydrophila. Mathematical methods were applied, for accurate pre