Sensory, chemical, microbial load and fatty acid composition changes of Silver carp (Hypophthalmichthys molitrix) after thermal drying process, vacuum packaging and storing in 4 °C

Abstract

The sensory attributes, chemical indices, microbial load and fatty acid composition of Silver carp were investigated as affected by thermal drying. The samples were dried at 60 °C for 4-24 h using a laboratory dryer, and stored at 4 °C. Temperature and time were recorded until moisture reduced to 35%. The products were packed under atmospheric and vacuum conditions. The results showed that there were no effects on sensory attributes, microbial load, pH and FFA. However drying significantly (p<0.05) affected TVB-N (4.26 to 18.30 mg/100g), PV (0.46 to 2.36 meqO2/Kg) and TBA (0.032 to 0.105 mgMDA/Kg). Mold and yeast counts were significantly (p<0.05) decreased (1 to 0.50 Log cfu/g) after process. Saturated fatty acids (30.66 to 34.29 g/100g) and ω-6 fatty acids (5.57 to 7.13 g/100g) were significantly (p<0.05) increased due to drying, but in contrast unsaturated fatty acids (54.62 to 50.56 g/100g), ω-3 (16.10 to 7.37 g/100g) and Polyunsaturated fatty acids (21.76 to 14.50 g/100g) were significantly (p<0.05) decreased. However, all of qualitative parameters and sensory attributes were changed during storage. Microbial load of vacuum-packed dried fish were lower than atmospheric samples; qua bacteria and mold-yeast counts were significantly (p<0.05) increased from 2.05 to 3.26 and 1.06 to 3.52 Log cfu/g, respectively. The results showed that vacuum packaging did not affect sensory attributes. Both dried products had acceptable quality during 30 days of storage but the vacuum-packed were better than atmospheric packed.