Effects of Oyster Shell Powder on the Microbial and Physicochemical Quality of Afitin, a Traditional Fermented Condiment

Aims: Afitin is a perishable condiment due to its high water content. Various preservatives are used to extend its shelf life, and among them, salt (NaCl) has generated controversy due to potential health risks associated to exposure to elevated concentrations of salt. The present study aims at assessing the effect of oyster shell powder on the quality changes of Afitin during storage at 30°C.

Methodology: Oyster shell powder was added to the condiment just before the natural fermentation at concentrations of 0.5%, 1% and 2%. At the end of the 24 h natural fermentation, the product was stored at 30°C. Afitin samples which did not receive the oyster shell powder served as controls. Samples were taken for microbiological, pH, water activity, and sensory analyses just before the fermentation, at the end of the fermentation, and at days 2 and 4 during storage.

Results: Oyster shell powder had a significant effect on the growth of microorganisms, on pH and water activity during the storage of Afitin. The average Total Viable Count (TVC) in the control samples was 8.9 Log CFU/g, whereas in the Afitin with 2% oyster shell powder, this load was 6.9 Log CFU/g after 2 days of storage. At the same time, the enterobacteria load in the control Afitin was 7.7 Log CFU/g, whereas in the Afitin with 2% oyster shell powder, it was below the detection limit. There was also a significant difference between the samples inoculated with 1% oyster shell powder and the control. From the sensory analysis, the control Afitin was rejected by the panellists after 48 h of storage, whereas the Afitin with 1% or 2% oyster shell powder was not rejected until the end of storage (4th day), indicating a notable prolongation of the product's shelf life by at least 100%.

Conclusion: The results show that oyster shell powder can potentially be used to improve the preservation of Afitin.