Flesh and fatty acid compositions, total volatile basic nitrogen (TVB-N), lipid oxidation and aerobic plate count, Enterobacteriaceae, psychrotrophic bacteria were determined in raw and smoked mackerel during cold storage (three groups differing in way of packaging; unpacked (UP), vacuum packaging (VP) and modified atmosphere (MAP) at 7, 14, 21, 28, 35, and 42 days. The protein, fat content and n-3 polyunsaturated fatty acids increased after smoking. The pH value and TVB-N were significantly higher in unpacked mackerel. Initial malondialdehyde concentration in raw mackerel was lowered after smoking and then lipid oxidation was the most pronounced in unpacked mackerel. Hot smoking, vacuum packaging, and modified atmosphere reduced bacterial growth, while the microbial contamination in all groups was below the limits during the whole period of storage. However, physicochemical properties of unpacked mackerel exceeded the limits from day 35 on. The present study indicates a lowering of products of secondary lipid oxidation after smoking followed by accelerated lipid degradation during cold storage of unpacked smoked mackerel. It is suggested that the smoking process and appropriate packaging method can protect lipids as well as valuable polyunsaturated fatty acids from oxidation. Vacuum packaging and modified atmosphere ensured microbial quality and protein and lipid stability. Their use is recommended for extending the shelf life of smoked fish considering the initial microbial and also chemical quality before and after smoking.

The aim of the study was to compare the efficiency, sensitivity and reliability of the MEAT 5.0 LCD-Array and innuDETECT Assay detection kits in identifying selected animal species. Samples were taken from the femoral muscles of six animal species (turkey, chicken, cattle, pig, sheep and goat), and six variants of binary meat mixtures were analysed at 18 different concentration levels of addition. The MEAT 5.0 LCD-Array test was able to detect 0.1% of other meat additions in two meat mixtures and 0.5% in four meat mixtures. The innuDETECT Assays were able to detect the addition of 0.1% of other meat in three meat mixtures, 0.5% in two mixtures and 1% in one meat mixture. Subsequently, these methods were applied in practice to 136 samples of various products taken from commercial food networks. By performing extensive monitoring, we identified 60 products in which one to three species were detected besides what was present on the product label. Nine products were contaminated with pig DNA. Two products that the MEAT 5.0 LCD-Array kit identified as positive for the presence of pig DNA were not confirmed by the innuDETECT Pork Assay kit. We recommend these methods of analysis to comprehensively monitor the presence of animal species in food samples, regardless of the degree of heat treatment or mechanical processing, as a tool to detect food adulteration.