Growth and toxigenesis behavior of Clostridium botulinum type E in Persian sturgeon (Acipenser persicus) Caviar prepared with various preservatives

Growth behavior of Clostridium botulinum type E beluga was studied in Acipenser persicus granular caviar treated with 5% NaCl, 5%NaCl plus 0.3% boric acid and 0.4%borax and 5%NaCl plus 0.15% methyl paraben incubated at temperatures -2, 5 and 15 °C for 224 days. The initial number of inoculated bacterial spore was 5.1×104 cfu/g caviar in each treated sample. The number of bacterial spores in samples treated with 5% NaCl changed to 3.59 × 104, 1.02×105 and 9.9×105 cfu/g at -2 °C, 5 °C and 15 °C, respectively, while those samples treated with 5%NaCl plus 0.3% boric acid and 0.4%borax changed to 1.56×104, 3.65×104 and 9.22×104 cfu/g, respectively. Also, number of bacterial spores in samples treated with 5% NaCl plus 0.15% methyl paraben changed to 1×104, 2.86×104 and 3.56×104 cfu/g at the above storage temperatures, respectively. Fourteen days post-inoculation, toxin production was positive in samples treated with 5% NaCl incubated at 5 °C and 15 °C, while those samples treated with 5%NaCl plus 0.3% boric acid and 0.4% borax were positive for toxin production only at 15 °C. Toxin production was negative in samples treated with 5%NaCl plus 0.15% methyl paraben incubated at all three above mentioned temperatures. These data showed that 5%NaCl plus methyl paraben had more inhibitory effect than boric, borax and NaCl. Also, such inhibitory effects can be increased at lower storage temperature of -2°C. Therefore, due to restricted usage of boric acid and borax in granular caviar, use of methyl paraben can be recommended as a safe preservative with a strong antimicrobial effect at caviar pH.