Evaluation of Twait Shad (Alosa fallax nilotica) in The Production of Cooked Marinade and Examining of Microbiological and Sensory Quality Changes During Storage at 4⁰C Storage

Project no. 23969 · Status: Kapanmış · 2022

Summary

In this thesis, Shad (Alosa fallax nilotica), one of the most economically dominant species in the world, will be used as a primary raw material. Despite its delicious taste, Shad is not commonly preferred very much due to its myriad bones. For this reason, this study aims to increase Shad’s consumption by processing it into a cooked marinade. Shad were obtained fresh and filleted from a private fish company and brought by cold chain conditions. After the shad were boiled (35 min at 65 ± 1°C), three different types of fruit vinegars (pomegranate, rose, and hawthorn) were applied. The fish were then left to marinate in refrigerator at 4°C for 24 hours in a (2:1) (vinegar to fish ratio). At the end of the ripening process, the fish was prepared for storage in glass jars by adding 10 g red chili peppers, 3 black peppers, and 2 bay leaves. The jars were filled with olive oil to prevent its contact with air. Red chili peppers, black pepper, and bay leaves were added to the marinades prepared in glass jars both for their antimicrobial properties and to add flavor and aroma. The prepared cooked shad marinades were stored in a refrigerator at 4°C for microbiological analysis (Total Psychrophilic Bacteria Count, Total Mesophilic Aerobic Bacteria CountLactic Acid Bacteria Count, , Coliform Bacteria Count, Mold and Yeast Count, Fecal Coliform Bacteria and E. coli Count, Staphylococcus aureus Count), pH, water activity and sensory changes (odor, taste, color, texture and general evaluation) as well as for the identification of spoilage-causing bacteria. Analyses were conducted on days 0, 1, 15, 30, 60, and 90, with the bacterial identification performed using API test kits.  The results revealed that total mesophilic aerobic bacteria counts were below the detectable level (<1.0 log CFU/g) in all groups on days 0 and 1. By day 60, counts were 7.22±0.04 log CFU/g in marinades prepared with hawthorn vinegar, 7.23±0.19 log CFU/g in marinades prepared with pomegranate vinegar and 7.19±0.08 log CFU/g in marinades prepared with rose vinegar, and all groups reached the inedible level (maximum recommended bacteria count 6-7 log CFU/g (ICMSF, 1986)). By day 90 (end of storage), counts were increased to 9.72±0.05 log CFU/g in the marinade prepared with hawthorn vinegar, 8.06±0.04 log CFU/g in the marinade prepared with rose vinegar and 8.01±0.07 log CFU/g in the marinade prepared with pomegranate vinegar. Staphylococcus aureus, coliform bacteria, fecal coliform and E. coli were not detected in any marinade group during storage. In all marinade groups, psychrophilic bacteria counts were below detectable levels (<1.0 log CFU/g) on storage days 0 and 1. Total psychrophilic aerobic bacteria change in marinades prepared with hawthorn vinegar, pomegranate vinegar, and rose vinegar was determined as 7.04±0.14 log CFU/g, 7.07±0.23 log CFU/g and 6.88±0.07 log CFU/g at day 60, respectively. At the end of storage (90th day), the highest to lowest number of psychrophilic bacteria in the marinade groups was 7.9±0.24 log CFU/g in the marinade prepared with pomegranate vinegar, 7.66±0.11 log CFU/g in the marinade prepared with hawthorn vinegar, and 7.60±0.04 log CFU/g in the marinade prepared with rose vinegar, respectively. As a result, pH values were determined as 6,37±0,10 in the control (fresh fish) group and 6,67±0,04 in boiled fish. The pH change in marinades prepared with Hawthorn, Rose, and Pomegranate vinegar was determined as 5,47±0,01, 5,51±0,03, and 5,36±0,05, respectively, on the 90th day. pH values increased with deterioration. The products were sensory and microbiologically rejected By day 60. The sensory and microbiological analyses heeded parallel results. According to the results of statistical analysis of microbiological and sensory value, Statistical analysis revealed significant differences in microbiological and sensory values that depending on storage duration (p<0.05). This indicates a very clear correlation between extended storage in time and that changes in both microbial counts and sensory attributes. According to the general evaluation of sensory analysis, the group prepared with hawthorn vinegar decreased from 7,62±0,51 to 4,03±0,54 on the 60th day. By day 90, it decreased to 2,72±0,79 and fell below the acceptability limit. The group prepared with pomegranate vinegar decreased from 7.37±0.91 to 4.21±0.53 on the 60th day. On the 90th day, it decreased to 2,87±0,35 and fell below the acceptability value. The group prepared with rose vinegar decreased from 7.25±1.48 to 4.68±0.96 on day 60. On the 90th day, it decreased to 2,62±0,94 and fell below the acceptability value. Overall, microbiological and sensory analyses were consistent, determining a shelf life of 60 days for cooked shad marinades.

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