Effects of curcumin-mediated of anti-microbial photodynamic technology on preservation of razor clam

Abstract: Razor clam (Sinonovaculaconstricta) is one of the most commercial clam species in China, which is in the Siliqua genus with narrow and slender shells. It has been reported that razor clams are rich in vitamins, amino acids and carbohydrates, and have high nutritional value. However, razor clam is easy to rot during storage, which seriously affects its sensory quality and consumer preferences. Particularly, its abundance of nutrients can lead to high reproduction of microorganisms, thus shortening its shelf life. Therefore, it is highly necessary to propose a novel and efficient sterilization method inhibiting microbial contamination for razor clam preservation. Currently, the anti-microbial photodynamic technology is considered as a novel non-thermal sterilization technology that not only can reduce the microbial growth in foods, but also can preserve their nutritional value, color, quality, and water content. Therefore, the purpose of this study was to investigate the influence of anti-microbial photodynamic technology on the preservation of razor clam. The treated conditions of the anti-microbial photodynamic sterilization for razor clam preservation were optimized by total number of bacterial colony with Box-Behnken experimental design. Meanwhile, sensory evaluation and physicochemical indexes were also evaluated on razor clam after storage at 4℃ for 8 days. The results demonstrated that curcumin-mediated could effectively inhibit the residual bacterial contamination in the razor clam and delay the growth of bacteria. The curcumin concentration, soaking time and LED exposure time were the key factors affecting the antibacterial efficiency of this photodynamic sterilization. The sterilization rate could reach 99.99%, when photodynamic sterilization using 26.6 μmol/L curcumin concentration with 24.8 min soaking time and 20.5 min LED exposure time. In addition, the appearance, color and other sensory characteristics of razor clam were maintained in good condition after anti-microbial photodynamic technology treatment storaged at 4 ℃ for 6 days. Compared with the control group, the physicochemical indexes water content, pH value, thiobarbituric acid and total volatile basic nitrogen values of razor clam were also in desirable range after the optimized anti-microbial photodynamic treatment. The water content of the anti-microbial photodynamic -treated samples was 73.79%, which is significantly higher than that of the control group 59.94%, indicating that treatment of razor clam with curcumin-mediated anti-microbial photodynamic technology might also maintain the water content. In addition, within 6 days of storage, the increase in pH value and decreases in thiobarbituric acid and total volatile basic nitrogen values of razor clam were observed. Moreover, anti-microbial photodynamic technology treatment could significantly delay these changes compared to the control group. In conclusion, this study suggested that the anti-microbial photodynamic technology had good bactericidal activity and could be used for the preservation of razor clam.