Min Gyu Song

Feeding schedule is an important management factor in shrimp culture, but responses to increasing meal frequency vary with ration, shrimp size, feeding method, and culture system. We evaluated five daily schedules (2–6 meals d⁻¹) for juvenile Pacific white shrimp, Penaeus vannamei, using the same biomass-based daily feeding-rate schedule in a filtered-seawater flow-through system. Shrimp (1.40 ± 0.01 g) were stocked at 20 per 300-L tank and reared for 8 weeks with three replicate tanks per treatment. Final body weight, weight gain, specific growth rate, and feed conversion ratio (FCR) differed among schedules (p < 0.05). Shrimp fed four to six times daily (FF4–FF6) showed higher growth and lower FCR than those fed twice daily (FF2), whereas the three-feeding treatment was intermediate. Compared with FF2, FF4 increased final body weight from 10.20 to 13.87 g and reduced FCR from 1.84 to 1.26. No significant differences in growth or FCR were detected among FF4, FF5, and FF6. Linear regression detected significant relationships between meal frequency and all four variables (p ≤ 0.0025). Whole-body proximate composition was evaluated descriptively because one pooled sample per treatment was analyzed in duplicate, and hemolymph AST, ALT, and total protein did not differ significantly. Under the conditions tested, four daily feedings were the lowest schedule associated with improved growth and feed utilization; however, feeding times and intervals also differed among treatments and feed leaching was not quantified.

Listeria monocytogenes is a major foodborne pathogen. Various methods can be used to control biofilms formed by foodborne pathogens. Recently, the food industry has become interested in plasma, which can be used as a non-thermal technology with minimum changes to product quality. In this study, the effects of dielectric barrier discharge (DBD) plasma on L. monocytogenes mixed-culture biofilms formed on stainless steel (SS), latex hand glove (HG), and silicone rubber (SR) were investigated. DBD plasma effectuated reductions of 0.11–1.14, 0.28–1.27 and 0.37–1.55 log CFU/cm², respectively. Field emission scanning electron microscopy (FE-SEM) demonstrated that DBD plasma cuts off intercellular contact and induces cell decomposition to prevent the development of biological membranes. It was confirmed that the formed biofilms collapsed and separated into individual bacteria. Our findings suggest that DBD plasma can be used as an alternative non-heating sterilization technology in the food industry to reduce biofilm formation on bacterial targets.

The hepatitis A virus (HAV), which can be a threat to humans, can be found in oysters. Oysters need sterilization technology that does not cause quality changes because they are eaten raw. Therefore, in this study, antiviral effects and quality changes were conducted using dielectric barrier discharge plasma (DBDP). Total titers of non-PMA- and PMA-treated suspensions of HAV were reduced to 0.20–1.05 and 0.35–1.49 log₁₀ copies/μL, respectively, after DBDP 10–60 min treatment. HAV titers on oysters were reduced to 0.20–1.11 and 0.33–1.33 log₁₀ copies/μL, respectively, after identical an DBDP treatment of the non-PMA- and PMA-treated oysters. The HAV titers were revealed as 0.295 (=[0.25 for 30 min + 0.34 for 60 min]/2) and 0.22 (for 60 min) log₁₀-reduction in PMA-treated suspensions and oysters, respectively, compared with the non-PMA-treated suspensions and oysters. The D₁ of DBDP in PMA-treated suspensions and oysters were 39.99 and 46.73 min, respectively. There was no difference in the pH of oysters after DBDP treatment compared to the non-treated control. There were some changes in the hardness of the DBDP-treated oysters, which was due to oyster individual differences rather than the DBDP treatment. In conclusion, DBDP treatment did not affect oyster quality and PMA was able to distinguish HAV infectivity.

Human norovirus (HNoV) GII.4 and Vibrio parahaemolyticus may be found in sea squirts. Antimicrobial effects of floating electrode-dielectric barrier discharge (FE-DBD) plasma (5–75 min, N₂ 1.5 m/s, 1.1 kV, 43 kHz) treatment were examined. HNoV GII.4 decreased by 0.11–1.29 log copy/μL with increasing duration of treatment time, and further by 0.34 log copy/μL when propidium monoazide (PMA) treatment was added to distinguish infectious viruses. The decimal reduction time (D₁) of non-PMA and PMA-treated HNoV GII.4 by first-order kinetics were 61.7 (R² = 0.97) and 58.8 (R² = 0.92) min, respectively. V. parahaemolyticus decreased by 0.16–1.5 log CFU/g as treatment duration increased. The D₁ for V. parahaemolyticus by first-order kinetics was 65.36 (R² = 0.90) min. Volatile basic nitrogen showed no significant difference from the control until 15 min of FE-DBD plasma treatment, increasing after 30 min. The pH did not differ significantly from the control by 45–60 min, and Hunter color in “L” (lightness), “a” (redness), and “b” (yellowness) values reduced significantly as treatment duration increased. Textures appeared to be individual differences but were not changed by treatment. Therefore, this study suggests that FE-DBD plasma has the potential to serve as a new antimicrobial to foster safer consumption of raw sea squirts.

Vibrio parahaemolyticus, one of the most common foodborne pathogenic bacteria that forms biofilms, is a persistent source of concern for the food industry. The food production chain employs a variety of methods to control biofilms, although none are completely successful. This study aims to evaluate the effectiveness of quercetin as a food additive in reducing V. parahaemolyticus biofilm formation on stainless-steel coupons (SS) and hand gloves (HG) as well as testing its antimicrobial activities. With a minimum inhibitory concentration (MIC) of 220 µg/mL, the tested quercetin exhibited the lowest bactericidal action without visible growth. In contrast, during various experiments in this work, the inhibitory efficacy of quercetin at sub-MICs levels (1/2, 1/4, and 1/8 MIC) against V. parahaemolyticus was examined. Control group was not added with quercetin. With increasing quercetin concentration, swarming and swimming motility, biofilm formation, and expression levels of target genes linked to flagellar motility (flaA, flgL), biofilm formation (vp0952, vp0962), virulence (VopQ, vp0450), and quorum-sensing (aphA, luxS) were all dramatically suppressed. Quercetin (0–110 μg/mL) was investigated on SS and HG surfaces, the inhibitory effect were 0.10–2.17 and 0.26–2.31 log CFU/cm², respectively (p < 0.05). Field emission scanning electron microscopy (FE-SEM) corroborated the findings because quercetin prevented the development of biofilms by severing cell-to-cell contacts and inducing cell lysis, which resulted in the loss of normal cell shape. Additionally, there was a significant difference between the treated and control groups in terms of motility (swimming and swarming). According to our research, quercetin produced from plants should be employed as an antibiofilm agent in the food sector to prevent the growth of V. parahaemolyticus biofilms. These results indicate that throughout the entire food production chain, bacterial targets are of interest for biofilm reduction with alternative natural food agents in the seafood industry.

For the seafood industry, Vibrio parahaemolyticus, one of the most prevalent food-borne pathogenic bacteria that forms biofilms, is a constant cause of concern. There are numerous techniques used throughout the food supply chain to manage biofilms, but none are entirely effective. Through assessing its antioxidant and antibacterial properties, quercetin will be evaluated for its ability to prevent the growth of V. parahaemolyticus biofilm on shrimp and crab shell surfaces. With a minimum inhibitory concentration (MIC) of 220 µg/mL, the tested quercetin exhibited the lowest bactericidal action without visible growth of bacteria. In contrast, during various experiments in this work, the inhibitory efficacy of quercetin without (control) and with sub-MICs levels (1/2, 1/4, and 1/8 MIC) against V. parahaemolyticus was examined. With increasing quercetin concentration, swarming and swimming motility, biofilm formation, and expression levels of related genes linked to flagella motility (flaA and flgL), biofilm formation (vp0952 and vp0962), and quorum-sensing (luxS and aphA) were all dramatically reduced (p < 0.05). Quercetin (0–110 μg/mL) was investigated on shrimp and crab shell surfaces, the inhibitory effects were 0.68–3.70 and 0.74–3.09 log CFU/cm², respectively (p < 0.05). The findings were verified using field emission scanning electron microscopy (FE-SEM), which revealed quercetin prevented the development of biofilms by severing cell-to-cell contacts and induced cell lysis, which resulted in the loss of normal cell shape. Furthermore, there was a substantial difference in motility between the treatment and control groups (swimming and swarming). According to our findings, plant-derived quercetin should be used as an antimicrobial agent in the food industry to inhibit the establishment of V. parahaemolyticus biofilms. These findings suggest that bacterial targets are of interest for biofilm reduction with alternative natural food agents in the seafood sector along the entire food production chain.

Quercetin is an active nutraceutical element that is found in a variety of foods, vegetables, fruits, and other products. Due to its antioxidant properties, quercetin is a flexible functional food that has broad protective effects against a wide range of infectious and degenerative disorders. As a result, research is required on food-contact surfaces (rubber (R) and hand gloves (HG)) that can lead to cross-contamination. In this investigation, the inhibitory effects of quercetin, an antioxidant and antibacterial molecule, were investigated at sub-MIC (125; 1/2, 62.5; 1/4, and 31.25; 1/8 MIC, μg/mL) against Salmonella Typhimurium on surfaces. When quercetin (0–125 μg/mL) was observed on R and HG surfaces, the inhibitory effects were 0.09–2.49 and 0.20–2.43 log CFU/cm², respectively (p < 0.05). The results were confirmed by field emission scanning electron microscopy (FE-SEM), because quercetin inhibited the biofilms by disturbing cell-to-cell connections and inducing cell lysis, resulting in the loss of normal cell morphology, and the motility (swimming and swarming) was significantly different at 1/4 and 1/2 MIC compared to the control. Quercetin significantly (p < 0.05) suppressed the expression levels of virulence and stress response (rpoS, avrA, and hilA) and quorum-sensing (luxS) genes. Our findings imply that plant-derived quercetin could be used as an antibiofilm agent in the food industry to prevent S. Typhimurium biofilm formation.