The non-spore forming gram-positive bacterium Listeria monocytogenes is a food pathogen bacterium and the causative agent of listeriosis. The aim of study was to determine the survival limits of L. monocytogenes inoculated in manufactured cold smoked sausages depending on water activity (aw) and pH values. Enumeration of L. monocytogenes colony forming units per gram (cfu gE-1) was done according to ISO standards. The decreasing water activity conditioned by moisture (weight) loss during ripening and pH decrease ensured negative exponential growth rate of inoculated L. monocytogenes lg cfu gE-1 - 0.44 each day. A significant Pearson's correlation (p is less than 0.01) was established between decreased values of L. monocytogenes count, aw (0.99), pH (0.92), moisture % (0.96), and weight loss (0.93) in sausages during ripening. The experiments were done at the Faculty of Veterinary medicine of the Latvia University of Agriculture and in a sausage manufacturer's laboratory.

The non-spore forming gram-positive bacterium Listeria monocytogenes is a food pathogen bacterium and a causative agent of listeriosis. The aim of the study was to determine the survival limits of L. monocytogenes inoculated in manufactured vacuum-packed cold smoked pork depending on shelf time, supported by water activity (aw) and pH values. Enumeration of L. monocytogenes colony forming units per gram (cfu gE-1) was done according to ISO standard. Water activity (aw) and pH values in pork samples were more or less constant and supported L. monocytogenes growth. The behaviour of L. monocytogenes in cold-smoked sliced pork by shelf time, when environmental factors changed minimally and supported growth, largely depended on the initial contamination level. A lag-phase of bacterial growing process before exponential growth rate of inoculated L. monocytogenes depended on initial cell concentration and had 10 days step level if storage temperature was approximately 5 deg C. A significant Pearson’s correlation (p is less than 0.01) was established between the microbiological test values of L. monocytogenes count changes in sliced and packed cold-smoked pork during storage time of 60 days. The main parameter which maintained negative polynomial growth rate of L. monocytogenes in cold-smoked pork was the decrease of live cell concentration in samples below lg 2.0. The experiments were done at the Faculty of Veterinary Medicine of Latvia University of Agriculture and at a sausage manufacturer’s laboratory.

In presented study we have investigated an occurrence of 15 polycyclic aromatic hydrocarbons (PAH) in different smoked meat and fish samples. After clean up and extraction procedures, the samples were analyzed by gas chromatography-mass spectrometry (GC-MS). Large variability in PAH levels for samples of the same type was found, thus the contamination level is not strongly correlated with the type of product. In the smoked fish samples concentrations of total PAHs ranged from 0.26 to 104 mu g kgE1, and in smoked meat samples - from 1.7 to 197 mu g kgE-1. In general, the predominating PAHs in all samples were benz(a)anthracene, crysene, and cyclopenta(c,d)pyrene. Also the elimination of PAHs in smoked fish by UV irradiation was investigated. Significant decrease in carcinogenic PAH content in smoked fish was found after a 15 min exposure.

The use of the smoke released during the wood burning process to prepare food products is a centuries-long tradition, practically all over the world. However, during the combustion process, a group of compounds called polyaromatic hydrocarbons (PAHs) are formed in the flue gases, which are carcinogenic and condense during the smoking process and diffuse into the smoked food product. Therefore, permissible PAH norms have been set for food producers, which significantly complicate the use of wood. In the study, using a gas analyser, we measured the flue gases released during the burning of specially made, apple and grey alder wood pellets, with and without enrichment of the supplied air with ozone. The use of ozone does not ensure a higher burning temperature of pellets, but it stabilizes it – temperature fluctuations are significantly wider using non-ozonised air (697 to 817 and 611 to 817 ℃, respectively). The content of CO2, CO, as well as CH4 and N2O increases significantly in apple wood flue gases using ozonised air, while CH4 increases and N2O decreases in grey alder smoke. Which generally indicates specific reactions with ozone during combustion. Comparing the flue gases released during the burning of apple and grey alder wood pellets, grey alder smoke contains significantly more N2O and CO2 than apple wood pellet flue gases. On the other hand, using ozonised air in the combustion process increases N2O significantly in the flue gas of apple tree pellets compared to white alder.