Browsing by Subject "tyhjiöpakkaus"

Nisin and silver have antimicrobial effects on bacteria growing on meat. Nisin is a bacteriocin peptide produced by lactic acid bacteria Lactococcus lactis. It is known to have a wide killing effect against many gram-positive bacteria. Food industry utilizes nisin as a food preservative. The antimicrobial effect of silver is known over the couple of decades. It has a killing effect against many gram-positive and gram-negative bacteria. In food industry silver can be used in packaging materials to prevent bacterial growth. In this study our aim was to evaluate the use of nisin and silver on the meat spoilage microbiota and the rate of spoilage in vacuum and modified atmosphere (80 % oxygen and 20 % carbon dioxide) packed meat. The antimicrobial effect of nisin and silver was evaluated by microbial counts and sensory evaluations. B. thermosphacta, Enterobacteriaceae, lactic acid bacteria and Pseudomonas sp. bacteria were interest of. Pyrosequencing was used to specify the bacterial taxonomy in spoiled meat samples. Nisin showed to have an antimicrobial effect only against lactic acid bacteria in vacuum packed meats. The growth rate of lactic acid bacteria was 2 logarithmic scales lower in nisin threated samples than in control samples. In modified atmosphere packed meat nisin didn´t show to have effect on bacterial growth. Nisin didn´t have antimicrobial effect on other bacteria. Silver treatment didn´t show to have effect on bacterial growth in both packing methods. Vacuum packed meat was evaluated of being spoiled after 56 days with nisin treatment and control samples spoiled couple of weeks earlier. Silver didn´t prolong the shelf life of meats compered to control samples. Based on the sequence analyse, total of 29 bacterial genus and 11 family where identified. Leuconostoc, Lactogbacillus and Serratia being the most abundant genus in vacuum packed meats in nisin series. Serratia and Pseudomoas sp. where spoilage bacteria associated in modified atmosphere packed meats. Lactic acid bacteria species belonging to genus Lactobacillus and Lactococcus where dominating in vacuum packed meats in silver series. Spoilage bacteria in modified atmosphere packed meat in silver series was mainly Leuconostos sp. The shelf life of vacuum packed meat was evidently longer in nisin treated samples and that’s why the allowance to use nisin in meat should be reconsidered. Silver didn’t have the effect to prolong the shelf life of meats on either packing methods even though its usage is allowed in food packaging materials.