HIGH PRESSURE PASTEURIZATION OF WHITE STURGEON Acipenser transmontanus CAVIAR
Caviars are ready to eat seafood products which refrigeration is currently the only method to preserve and extend the shelf life. The international market demand for pasteurized caviar is increasing significantly, particularly, cruise and airline industries. However, caviar is heat labile which makes it difficult to use thermal processing for pasteurization. Non-thermal processing and novel approaches such as natural antimicrobial compounds provide possible alternative to the conventional thermal processing. The objective of this study was investigating the effect of high pressure processing alone and in combination with a natural antimicrobial compound, on Listeria innocua reduction in White sturgeon caviar.
An overnight cell suspension (1mL) of approximately 108 CFU/ml of Rifampicin resistant L. innocua in either deionized water or 10mM Gallic acid was added to one gram of caviar and incubated for two min. After that, the treatment solutions were discard and caviar samples were transfer to 0.5 Eppendorf tubes, wrapped with paraffin film and vacuum packed prior to High Pressure treatment. An Avure 2L High Pressure Laboratory Food Processing system was used to treat caviar sample. This system was designed with an integrated temperature controlling unit to maintain the ambient temperature during the process. DI water was used as pressure transferring medium. After being vacuum packed, caviar sample were subjected to three different pressure levels including 300, 350 and 400 MPa in three cycles, five minutes each cycle. The treatment temperature was keep at room temperature. Log survival of bacteria was assessed by the standard plate counting method, where treated bacterial samples were serially diluted in Phosphate-Buffered Saline (PBS) followed by overnight cultivation in Tryptic Soy Agar (TSA).
The results (Fig. 1) showed 1.2, 2.7, and 6 log reduction for DI treated samples exposed to 300, 350 and 400 MPa, respectively, and 1.2, 3.22, and 6 log reduction for Gallic acid treated samples treated with 300, 350 and 400 MPa, respectively.