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 survival of inoculated in a cold-smoked sausages Listeria monocytogenes wild strains was studied. The sausages were prepared with and without starter cultures. The survival limits of L. monocytogenes and lactic acid bacteria (LAB) were determined as colony forming units per gram (cfu gE-1) depending on water activity (aw) and pH on 0, 1st, 3rd, 5th, 7th, 14th and 21st days of maturation. The decreasing water activity conditioned by moisture (weight) loss during ripening and pH decrease ensured negative polynomial growth rate of inoculated L. monocytogenes - 0.27 lg (cfu gE-1) each day of ripening time, and - 0.65 lg (cfu gE-1) on the first 7 days of maturation. A significant Pearson’s correlation (p is less than 0.01) was established between decreased values of L. monocytogenes count, aw, salt concentration and LAB growth in sausages during the ripening period of 21 days. The main parameters, maintained negative exponential growth rate of L. monocytogenes in cold smoked sausages, are aw value decrease and LAB (starter culture), which stopped L. monocytogenes growth at the beginning of cold-smoked sausage maturation. If fermentation process went technically and hygienically correctly, the fermented (cold-smoked) sausages could be one of the safest meat products, because in real practice a low level contamination has been seen. The remaining count of L. monocytogenes in cold-smoked sausage depends on the possible initial contamination level and could exceed the European Union regulation value 2.0 lg (cfu gE-1) for ready-to-eat products when contamination at first is more than lg 5.0.

Smoked sprats (Sprattus sprattus balticus) from the Baltic Sea are one of the most popular processed fish products in Latvia. The amount of catching and demand is annually increasing. For producers, it is important to provide stable quality throughout the year, which sometimes is challenging due to many factors. Smoked fish quality depends not only on the seasonality, but also on the applied technologies. The aim of the current study was to review research findings about factors affecting the smoked fish quality. The databases of Science Direct, Web of Science, Wiley Online Journals and Google Scholar were searched. The first parameter that affects quality of fish till processing is raw material, its catching place and season, as well as whether it is fresh or frozen fish, that includes not only microbiological parameters, but also physical and chemical changes in fish depending on the storage conditions. The second parameter is the applied pre-treatment methods (using salt, acids) before processing, which can improve fish texture and make better result for smoked fish. The third parameter is the used technology for the fish processing, heat treatment methods use of wood chips or liquid smoke, or adjustment of smoking conditions. These all together make a lot of sensorial and textural changes in the final product. If any of these parameters is changed during processing, they can affect the smoked fish quality. Therefore, to ensure constant quality of smoked fish, in-depth knowledge of parameters is extremely important.

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.