Inactivation of Human Norovirus GII.4's Infectivity in Fresh Oysters (Crassostrea gigas) through Thermal Treatment in Association with Propidium Monoazide

The current study investigated the effects of heat treatment (85 °C or 100 °C for 5-20 min) on human norovirus (HuNoV) GII.4's capsid stability in fresh oysters. In addition, propidium monoazide (PMA) was used in viral samples to distinguish infectious viruses and evaluated using real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR). Further, we explored the effect of the heat treatment on oyster quality (Hunter color and hardness). The titer of HuNoV for oysters significantly (p < 0.05) decreased to 0.39-1.32 and 0.93-2.27 log10 copy number/μL in the non-PMA and PMA-treated groups, respectively, after heat treatment. HuNoV in oysters not treated with PMA showed a decrease of <1.5 - log10, whereas in PMA-treated oysters, a decrease of >1 - log10 was observed after treatment at 85 °C for 10 min. Treatments for both 15 min and 20 min at 100 °C showed a >99% log10 reduction using PMA/RT-qPCR. In the Hunter color, an increase in heat temperature and duration was associated with a significant decrease in 'L' (brightness+, darkness-) and an increase in 'a' (redness+, greenness-) and 'b' (yellowness+, blueness-) (p < 0.05). Our findings confirmed that the hardness of oyster meat significantly increased with increasing temperature and time (p < 0.05). This study demonstrated that PMA/RT-qPCR was effective in distinguishing HuNoV viability in heat-treated oysters. The optimal heat treatment for oysters was 10 min at 85 °C and 5 min at 100 °C.

Effect of Dielectric Barrier Discharge Plasma against Listeria monocytogenes Mixed-Culture Biofilms on Food-Contact Surfaces

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.

Food functionalities and bioactivities of protein isolates recovered from skipjack tuna roe by isoelectric solubilization and precipitation

Four roe protein isolates (RPIs) from skipjack tuna were prepared using isoelectric solubilization (pH 11 and 12) and precipitation (pH 4.5 and 5.5) (ISP) at different pH points to evaluate their physicochemical and functional properties and in vitro bioactivities. Moisture (<6.3%) and protein (71%-77%) content were maintained. Sulfur, sodium, phosphorus, and potassium were the major elements, and glutamic acid and leucine were the prevalent amino acids (12.2-12.8 and 9.6-9.8 g/100 g protein, respectively) in RPIs. RPI-1 showed the highest buffering capacity at pH 7-12. RPIs and casein showed similar water-holding capacities. At pH 12, RPI-1(pH 11/4.5) showed the highest solubility, followed by RPI-3(pH 12/4.5), RPI-2(pH 11/5.5), and RPI-4(pH 12/5.5) (p < .05). Oil-in-water emulsifying activity indices of RPI-1 and RPI-3 significantly differed. At pH 2 and 7-12, pH-shift treatment improved the food functionality of RPIs, which was superior to positive controls (casein and hemoglobin). RPI-1 showed ABTS+ radical scavenging (102.7 μg/ml) and angiotensin-converting enzyme inhibitory activities (44.0%).

Food functionality of protein isolates extracted from Yellowfin Tuna (Thunnus albacares) roe using alkaline solubilization and acid precipitation process

Four types of roe protein isolates (RPIs) were prepared through the alkaline solubilization and acid precipitation (ASAP) process, and their functional properties and in vitro bioactivities were evaluated. Higher buffer capacity in pH-shift range of 8-12 was found in RPI-1 (pH 11/4.5), required average 94.5 mM NaOH than that of other RPIs to change the pH by 1 unit. All the samples of 1% dispersion (w/v) showed the lowest buffering capacity near the initial pH. The water-holding capacities (WHC) of RPIs and casein as controls without pH-shift were in range of 3.7-4.0 g/g protein, and there were no significant differences (p > 0.05). At pH 2 and 8-12 with pH-shift, WHC and protein solubility of RPIs were significantly improved compared to those of controls. Foaming capacities of RPI-1 and RPI-3 were 141.9% and 128.1%, respectively, but those of RPI-2 and RPI-4 were not detected. The oil-in-water emulsifying activity index of RPI-1 and RPI-3 was 10.0 and 8.3 m2/g protein, which was not statistically different from casein (7.0 m2/g), but lower than that of hemoglobin (19.1 m2/g). Overall, RPIs, casein, and hemoglobin exhibited lower food functionality at pH 4-6 near isoelectric points. Through the pH-shift treatment, the food functionalities of RPIs were improved over the controls, especially in the pH 2 and pH 8-12 ranges. RPI also showed in vitro antioxidant and antihypertensive activities. Therefore, it has been confirmed that RPI extracted from yellowfin tuna roe has high utility as a protein- or food-functional-enhancing material or protein substitute resource for noodles, confectionery, baking, and surimi-based products.

Survey and Exposure Assessment of Biogenic Amines in Fish Species Commonly Consumed in Korea

Because of the increased awareness of the health benefits of fish, fish consumption has increased each year in several countries, including Korea. However, fish consumption is associated with acute toxicity owing to the presence of biogenic amines in rapidly spoiling fish. Several food safety agencies have established standards for acceptable histamine concentrations in some restrictive fish and fishery products; however, such standards are not available for other species. We aimed to generate data from biogenic amine monitoring to evaluate the safety of fish commonly consumed in Korea. We monitored the biogenic amine concentrations in 609 fish samples from 19 commonly consumed species. Of these 609 samples, several had amine concentrations higher than the maximums allowed. An age-specific exposure assessment based on human biogenic amine exposure per serving revealed that persons 1 to 3 years of age had the highest exposure to total biogenic amines, although no significant differences were found between the age groups analyzed. The analysis also revealed that the exposure in some fish species, such as Japanese jack mackerel, Konoshiro gizzard shad, and brown sole, exceeded the standard limits established in some countries. These results suggest that more fish species should be included to establish standards for exposure to various biogenic amines. Parameters such as age-specific consumption and data for populations with maximum consumption should be considered because the current standards are limited to histamine and do not account for the differences in histamine sensitivity associated with these variables. Our results provide important data on limits for biogenic amines in various fish species that could be used to minimize potential health risks.

Chemical composition and functional properties of roe concentrates from skipjack tuna (Katsuwonus pelamis) by cook-dried process

The objective of this study was to investigate physicochemical properties of protein concentrate from skipjack tuna roe by a cook-dried (boiled or steamed-dried) process, and to evaluate their food functional properties. The yields of boil-dried concentrate (BDC) and steam-dried concentrate (SDC) prepared from skipjack tuna roe were 22.4 for BDC and 24.4% for SDC. Their protein yields were 16.8 and 18.4%, respectively. In terms of major minerals of the BDC and SDC, sulfur (853.2 and 816.6 mg/100 g) exhibited the highest levels followed by potassium, sodium and phosphorus. The prominent amino acids of roe protein concentrates (RPCs) were Glu, Asp, Leu and Val. The BDC and SDC showed a higher buffer capacity than egg white (EW) at the pH-shift range. The pH-shift treatment significantly improved the water holding capacities of RPCs, except pH 6. But they had a low solubility across the pH-shift range. The foaming capacities (104%-119%) of BDC and SDC were significantly lower than those of EW (p < .05), and their foam stabilities were not observed. Emulsifying activity index (m2/g protein) of RPCs and EW was 2.3 for BDC, 11.1 for SDC and 18.0 for EW. RPCs in the food and seafood processing industries will be available as egg white alternative protein sources and will be available as ingredients of surimi-based products in particular.

Protein functionality of concentrates prepared from yellowfin tuna (Thunnus albacares) roe by cook-dried process

Three kinds of roe protein concentrates (RPCs: boil-dried concentrate, BDC; steam-dried concentrate, SDC; freeze-dried concentrate, FDC) were prepared from yellowfin tuna to produce value added products for food applications. The buffer capacities of the RPCs were higher under alkaline than under acidic conditions. The water holding capacities of the RPCs were in range 4.5-4.7 g/g protein at pH 6.0. The protein solubility of the FDC (14.2%) was higher than those of the BDC (5.4%) and SDC (5.5%) at pH 6.0. The foaming capacity of the FDC (156.8%) was higher than those of the BDC (109.7%) and SDC (109.4%); the FDC foam was stable for 60 min. The oil-in-water emulsifying activity index of the FDC (12.2m2/g protein) exceeded those of the BDC and SDC (2.2m2/g protein). Protein concentrates from yellowfin tuna roe may be useful as a potential protein source and as a high-value food ingredient.

Processing optimization of restructured jerky from sea rainbow trout frame muscle

This study determined optimal drying temperature and time on the moisture content, hardness, and overall sensory acceptance of restructured jerky from sea rainbow trout frame muscle (RJ-SRTF) using response surface methodology. The optimal drying conditions with respect to the above variables were 67.2°C for drying temperature and 8.6 h for drying time. The predicted values of response optimal conditions were 18.8 g/100 g for moisture content, 495.8 g/cm² for hardness, and a score of 7.2 for overall sensory acceptance. The actual values obtained in this experiment were 19.1±0.6 g/100 g for moisture content, 453.9±91.0 g/cm² for hardness, and a score of 7.4±0.5 for overall sensory acceptance. Both actual and predicted values were nearly identical. In conclusion, the models are adequately fitted to experimental data and suitable for optimization.

Comparison of collagen characteristics of sea- and freshwater-rainbow trout skin

Proximate composition, volatile basic nitrogen content, and concentrations of collagen in skin samples from either sea- (S-RT) or freshwater-rainbow trout (F-RT) were characterized and compared, to assess the effect of the sea or freshwater habitat on these parameters. Results of amino acid composition, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, thermal denaturation assay and Fourier transform infrared (FT-IR) spectroscopy of acid-soluble collagens were comparable between the two sample sets. Both acid-soluble collagens from sea- and freshwater-rainbow trout skins contained glycine as the major amino acid and high alanine, proline, and hydroxyproline contents, and was found to be predominantly composed of α1-, α2-, and β-chains. FT-IR spectra of ASCs from S-RT and F-RT skins were quite similar. These findings suggest that different rainbow trout habitats (seawater and freshwater) do not affect amino acid composition and molecular weight properties of ASCs from S-RT and F-RT skins.

Neuroprotective effects of phlorotannins isolated from a brown alga, Ecklonia cava, against H2O2-induced oxidative stress in murine hippocampal HT22 cells

Exposure of neurons to hydrogen peroxide (H(2)O(2)) results in oxidative stress and the activation of a cascade of intracellular toxic events resulting in oxidation, lipid peroxidation, and Ca(2+) elevation, ultimately resulting in cell death. In this study, we attempted to characterize the neuroprotective effects of phlorotannins isolated from Ecklonia cava, including phloroglucinol, eckol, triphloroethol A, eckstolonol, and dieckol, against H(2)O(2)-induced cell damage in murine hippocampus neuronal (HT22) cells. We measured the reactive oxygen species (ROS) and lipid peroxidation levels and evaluated the resultant cell death and alterations in Ca(2+)-concentrations. All phlorotannins were to scavenge intracellular ROS and repress ROS accumulation, thus preventing lipid peroxidation. Consquently, all phlorotannins reduced H(2)O(2)-induced cell death in HT22 cells. Moreover, phlorotannins inhibited H(2)O(2)-induced Ca(2+) release. This study provides a new useful strategy for preventing neuronal H(2)O(2)-induced oxidative stress.

Molecular characteristics and anti-inflammatory activity of the fucoidan extracted from Ecklonia cava

Enzymatic extraction has been successfully used for extracting numerous biologically active compounds from a wide variety of seaweeds. In this study, we found that enzymatic extraction of the fucoidan from Ecklonia cava may be more advantageous than water extraction. Therefore, we studied the E. cava fucoidans extracted by the enzymatic extraction technique and used ion-exchange chromatography to determine their molecular characteristics and anti-inflammatory activities. The crude and fractionated fucoidans (F1, F2, and F3) consisted mostly of carbohydrates (47.1-57.1%), uronic acids (9.0-15.8%), and sulfates (16.5-39.1%), as well as varying levels of proteins (1.3-8.7%). The monosaccharide levels significantly differed, and the composition included fucose (53.1-77.9%) and galactose (10.1-32.8%), with a small amount of rhamnose (2.3-4.5%), xylose (4.0-8.2%), and glucose (0.8-2.2%). These fucoidans contained one or two subfractions with an average molecular weight (Mw) ranging from 18 to 359×10(3)g/mol. These fucoidans significantly inhibited NO production in lipopolysaccharide (LPS)-induced Raw 264.7 macrophage cells by down-regulating the expression of iNOS, COX-2, and pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1β. Thus, the present results suggest that E. cava fucoidan may be a potentially useful therapeutic approach for various inflammatory diseases.

Purification and characterization of cathepsin L-like enzyme from the muscle of anchovy, Engraulis japonica

Results relative to inhibitory effects and substrate specificity indicated that a protease from the muscle of anchovy, Engraulis japonica, was a cathepsin L-like enzyme. The enzyme was activated by thiol reagents and inhibited by thiol-blocking reagents. The molecular weight was estimated to be 25.8 kDa by SDS-PAGE. The enzyme exhibited its maximal activity at pH 6.0 and 50 degrees C for casein and N-benzoyl-D, L-arginine-beta-naphthylamide. The enzyme hydrolyzed at the position of Phe1, Asn3, Val13, Glu14, Val19 and Gly24 of the insulin beta-chain. The K'm and kcat of the enzyme were 73.4 microM and 0.5 microM/min, respectively, toward Z-Phe-Arg-MNap.

Comparison of trypsin and chymotrypsin from the viscera of anchovy, Engraulis japonica

The molecular weights of trypsin and chymotrypsin purified from anchovy viscera were estimated to be 25.6 and 26.1 Kda, respectively, by SDS-PAGE. Both enzymes had their maximal activity at pH 9.0 and 45 degrees C for casein and at pH 8.0 and 45 degrees C for synthetic substrates. Trypsin hydrolyzed at the position of Arg22 and Lys29, and chymotrypsin did at the position of Phe1, Tyr16, Phe24, Phe25, and Tyr26 of insulin beta-chain. The K'm and kcat of trypsin were 50 microM and 1.84 microM-1 min-1 toward N-benzoyl-L-arginine-p-nitroanilide (BAPNA) and those of chymotrypsin were 89 microM and 10.0 microM-1min-1 toward N-succinyl-(Ala)2-Pro-Phe-p-nitroanilide. The activation energy of trypsin and chymotrypsin were estimated to be 14 Kcal/mol toward N-benzoyl-L-arginine-p-nitroanilide and 6.5 Kcal/mol toward benzoyl-L-tyrosine ethyl ester.