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.

Baltic sprats (Sprattus sprattus balticus) are a good source of protein, vitamins D3, B12, minerals, and unsaturated fats. In response to consumer demand, various types of fish products of stable quality are available all year round. Pre-treatment with brine containing acetic acid, salt (NaCl), and/or granulated CaCl2 in various concentrations and proportions can be used to stabilise quality. The aim of the study was to evaluate the effect of various pre-treatment methods on smoked Baltic sprat sensory and technological parameters. Prior to smoking, fish was treated in a solution of additives in various proportions for 30 min. Untreated sprats were used as a control sample. The use of pre-treatment allowed reduction of the smoking losses; the combination of NaCl and acetic acid resulted in about 26% smoking loss. If no pre-treatment was applied, the drying losses after 24-hour storage were 1.6%, while using the solution of NaCl and CaCl2 it decreased to 0.3%. Both the pre-treatment method and freezing affected fish pH. The pH of smoked fresh sprats was 6.73 and for smoked frozen sprats, it was 6.38. Sensory testing using the Just About Right (JAR) method demonstrated that the use of acetic acid made smoked fish texture firmer.

Smoked sprats are delicious and nutritionally valuable product. Besides protein, it contains high amount of unsaturated fatty acids and fat soluble vitamins. Nowadays, human interest for fish product consumption is increasing. It leads to the demand for increased shelf life of the smoked sprats. One way to prolong the shelf life is to use some pre-treatment prior to smoking. The aim of study was to analyse the effect of pre-treatment on smoked Baltic sprat quality and microbiological parameters. Various compositions of brine using salts (NaCl, CaCl2) and acetic acid in different proportions were used for fresh sprat pre-treatment. Pre-treatment had the influence on physical parameters; pre-treated samples had higher salt and lower moisture content, and lower pH, which allowed prolonging the shelf life of smoked sprats. The highest pH was in the control sample 6.6, and it allowed growth of yeasts, moulds, Pseudomonas spp., and mesophilic and facultative anaerobic microorganisms. The results demonstrated that after two-week storage of the smoked sprats the growth of moulds (1×102 CFU g−1) was observed only for smoked sprats without pre-treatment (control sample), indicating the positive effect of pre-treatment. Salmonella spp., Clostridium perfingens, Listeria monocytogenes, and Escherichia coli were not detected in any of the analysed samples. After pre-treatment in brine, containing combination of NaCl and CaCl2, smoked fish had darker colour compared to control sample or sample with sodium chloride only. Any of applied pre-treatments, except brine containing NaCl, made firmer texture of the smoked fish.