Abstract
Authentication of tuna fish products is necessary to assure consumers of accurate labelling of food products. The quality of species specific DNA crucially affects the efficiency of amplification during the subsequent PCR. The problem in DNA detection in canned products lies in the possibility of the fragmentation of DNA during the processing technologies and the use of ingredients (oil, salt, spice), that may inhibit the PCR reaction. In this study three DNA extraction methods were compared: DNeasy Blood and Tissue Kit, DNeasy mericon Food Kit and Chemagic DNA tissue 10 Kit. The quantity and quality of DNA were evaluated by measuring DNA concentration and ratios A260/A280. Several parameters were estimated: the effect of whole and mechanically treated muscle, sterilization procedure used in canned process (high temperature in combination with high pressure) and addition of raw materials. The highest DNA concentrations were observed in non-processed muscle that is not influenced by the sterilization process. Canned whole muscle demonstrated lower DNA yield, and furthermore, the mechanical treatment (canned ground) resulted in lower values of DNA concentration that was registered by using all three types of DNA extraction kits. DNeasy mericon Food Kit produced DNA of higher concentration in non-processed sample, Chemagic DNA tissue 10 Kit delivered higher DNA yields than kits DNeasy Blood and Tissue Kit and DNeasy mericon Food Kit in canned samples, although the purity was lower, but still within the range 1.7 - 2.0. DNA was considered to be satisfactorily pure in all three types of samples and using all three types of DNA isolation. In case of the samples enriched of ingredients and treated with sterilization process as whole or ground muscle Chemagic DNA tissue 10 Kit produced in all samples (whole and ground muscle) the highest values of DNA concentration, but almost all values of A260/A280 were lower than 1.7. Therefore DNeasy mericon Food Kit appears to be a favorite one, in all samples with whole muscle gives higher values of DNA concentrations than DNeasy Blood and Tissue Kit. Addition of ingredients influenced the DNA yield in terms of decreasing in samples containing vinegar and lemon, but some of the ingredients resulted surprisingly in higher yield of DNA. This was not consistent in whole and ground muscle, and the differences were described also among particular kits. The impact of ingredients was not conclusively approved and their importance to the suitability of extracted DNA for PCR amplification is needed to be discussed in further analysis.
Highlights
Fish species identification gains attention due to the commercialization of fish through filleted, salted, smoked or canned fish products
Primary requirement of this study is to find out, how far is DNA influenced by the technological processes using in food industry in model canned samples from the muscle tissue of yellowfin tuna (Thunnus albacares) and how the subsequent sample preparation and DNA extraction procedure can affect its qualitative and quantitative parameters
In the case of DNA purities, DNA was considered to be satisfactorily pure in all three types of samples and using all three types of DNA isolation
Summary
Fish species identification gains attention due to the commercialization of fish through filleted, salted, smoked or canned fish products. Tuna fish belong among the most economically important fishery resources because are typically used to manufacture canned products, the main format for marketing of these species (Espineira et al, 2009). The identification of tuna and bonito species according to their morphological features is possible only in whole or lightly processed fish. In processed products such as filleted or canned fish the morphological characteristics are removed, analytical methods as an important tool for species identification must be used. Due to the protein denaturation caused by heating or canning (high temperature in combination with high pressure) process (Mackie et al, 1999), DNA is more suitable molecular marker for fish species authentication, because it is more resistant to the thermal treatment. The fragment size is limited factor for the Volume 10
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