Assessment of chemical and bacterial quality of surimi produced from common Kilka (Clupeonella cultriventris) under pennyroyal (Mentha pulegium) extract during refrigerator storage (4±1 °C)

In this research, the pennyroyal extract (PE) effect was studied at different concentrations (0, 2 and 4% w/v) on chemical and bacterial quality of surimi produced from common Kilka over a period of 15 days (0, 3, 6, 9, 12 and 15 days) during refrigerator storage (4±1°C). The experiments was conducted to determine chemical tests including peroxide value (PV), thiobarbitoric acid (TBA), total volatile bases nitrogen (TVB-N), pH and total viable count (TVC) and psychrophilic count (PTC) as bacterial tests at 3 days intervals with triplicate. Findings showed that the PV content was significantly higher than that from control treatment as it was increased from 0.64 on the first day to 5.41 meq O₂ on the 12th day (p<0.05). The TBA and TVB-N amounts were increased in the control treatment until 15th day so that it was recorded 0.43 mg malondialdehyde for TBA and 32.8 mg N for TVB-N on day 15  with a significant difference compared to those containing PE (p<0.05). The pH value was significantly higher in control than groups treated with PE during the whole storage period (p<0.05), with an increase from 7.14 at day 1 to 8.08 at day 15. The TVC and PTC bacteria from treated groups with PE were significantly lower than those from control wherein TVC and PTC bacteria were increased in the control from 3.55 to 3.25 to 6.64 and 5.96 log cfu/g, respectively (p>0.05); but it was remained lower than the proposed acceptable limit (7 log cfu/g). Based on the findings of the present study, 4% PE can use for enhance the shelf life of the common kilka surimi at refrigerator.