Samooel Jung

Evaluation of atmospheric pressure plasma to improve the safety of sliced cheese and ham inoculated by 3-strain cocktail Listeria monocytogenes

The objective of this study was to evaluate the efficacy of atmospheric pressure plasma (APP), which is capable of operating at atmospheric pressure in air, in sliced cheese and ham inoculated by 3-strain cocktail of Listeria monocytogenes (ATCC 19114, 19115, and 19111, LMC). The process parameters considered were input power (75, 100, 125, and 150 W) and plasma exposure time (60, 90, and 120 s). Microbial log reduction increased with increases of input power and plasma exposure time. After 120 s APP treatments at 75, 100, and 125 W, the viable cells of LMC were reduced by 1.70, 2.78, and 5.82 log in sliced cheese, respectively. More than 8 log reductions can be achieved in 120 s at 150 W. In contrast, reductions after 120 s ranged from 0.25 to 1.73 log CFU/g in sliced ham. Calculated D values, the exposure time required to inactivate 90% of a population, from the survival curves of 75, 100, 125, and 150 W of APP treatments were 71.43, 62.50, 19.65, and 17.27 s for LMC in sliced cheese, respectively, and those in sliced ham were 476.19, 87.72, 70.92, and 63.69 s. No viable cells were detected at 125 and 150 W of APP treatment in sliced cheese, irrespective of plasma exposure time, after 1 week at a detection limit of 10(1) CFU/g. These results indicate that the inactivation effects of APP on L. monocytogenes are strongly dependent on the type of food.

Effect of atmospheric pressure plasma on inactivation of pathogens inoculated onto bacon using two different gas compositions

Atmospheric pressure plasma (APP) is an emerging non-thermal pasteurization method for the enhancement of food safety. In this study, the effect of APP on the inactivation of pathogens inoculated onto bacon was observed. Sliced bacon was inoculated with Listeria monocytogenes (KCTC 3596), Escherichia coli (KCTC 1682), and Salmonella Typhimurium (KCTC 1925). The samples were treated with APP at 75, 100, and 125 W of input power for 60 and 90 s. Two gases, helium (10 lpm) or a mixture of helium and oxygen, (10 lpm and 10 sccm, respectively) were used for the plasma generation. Plasma with helium could only reduce the number of inoculated pathogens by about 1-2 Log cycles. On the other hand, the helium/oxygen gas mixture was able to achieve microbial reduction of about 2-3 Log cycles. The number of total aerobic bacteria showed 1.89 and 4.58 decimal reductions after plasma treatment with helium and the helium/oxygen mixture, respectively. Microscopic observation of the bacon after plasma treatment did not find any significant changes, except that the L∗-value of the bacon surface was increased. These results clearly indicate that APP treatment is effective for the inactivation of the three pathogens used in this study, although further investigation is needed for elucidating quality changes after treatment.

Effect of dietary mixture of gallic acid and linoleic acid on antioxidative potential and quality of breast meat from broilers.

The effect of dietary mixture of gallic acid and linoleic acid (MGL) on the antioxidative potential and quality of breast meat from broilers was investigated. Broilers during the 22-36days on trial received 3 dietary treatments: 1) control (commercial finisher diet), 2) 0.5% MGL (gallic acid:linoleic acid=1M:1M), and 3) 1.0% MGL. The feed efficiency, DPPH radical scavenging activity, ABTS(+) reducing activity, reducing power, TBARS, and total phenolic content in the breast from the broilers improved significantly by 1.0% MGL dietary treatment. Arachidonic and docosahexaenoic acids were higher in the broilers fed both levels of MGL diets. In addition, water holding capacity of the breast was enhanced by the 1.0% dietary MGL treatment and was accompanied by a slight antimicrobial activity (1 decimal reduction) during storage. In conclusion, 1.0% dietary supplementation with MGL can improve the antioxidative potential, and nutritional and functional qualities of broiler breast meat.

Comparison of Quality Traits of Meat from Korean Native Chickens and Broilers Used in Two Different Traditional Korean Cuisines

With the aim of investigating the differences in the quality traits between Korean native chicken (Hanhyup, KNC) and broilers commonly used in two different traditional Korean cuisines, the chemical composition and sensory properties of breast and thigh meat from the two chicken strains were assessed. KNC for baeksuk (chicken meat braised in soup with various Oriental medicinal plants; KNL), KNC for samgyetang (similar to baeksuk but young chickens and ginseng are used; KNS), broiler for baeksuk (BL), and broiler for samgyetang (BS) were used as treatments in this study. KNL and KNS contained higher protein but lower fat content than BL and BS. The L* values of breast and thigh meat, but not the a* values, were significantly different between KNS and BS, whereas significant differences in both values were observed between KNL and BL. Compared to the other three types of chickens, KNS contained the highest total and insoluble collagen content, and KNL and BL showed higher inosine-5’-monophosphate content in their meat. Overall, KNL and KNS contributed darker, less tender meat with higher protein and less fat content together with more n-3 fatty acids, as opposed to their counterparts used for the same cuisines. Based on the results of the sensory analysis, even though there are some differences in physiochemical traits, different chicken sources do not differ in overall sensory quality. This information can help consumers to understand better the meat available for their preferred traditional cuisines.

The use of atmospheric pressure plasma-treated water as a source of nitrite for emulsion-type sausage.

We investigated the possible use of atmospheric pressure plasma-treated water (PTW) as a nitrite source in curing process. Emulsion-type sausages were manufactured with PTW, celery powder containing nitrite, and synthetic sodium nitrite at a concentration of nitrite ion 70mgkg(-1). In terms of sausage quality, there were no noticeable effects of PTW on the total aerobic bacterial counts, color, and peroxide values of sausages compared with those of celery powder and sodium nitrite throughout 28days of storage at 4°C. Sausage with added PTW had lower concentrations of residual nitrite compared to those of added celery powder and sodium nitrite during the storage period (P<0.05). The sensory properties of PTW-treated and sodium nitrite-treated sausages were not different, whereas the sausage with added celery powder received the lowest scores in taste and acceptability. From the results, it is concluded that PTW can be used as a nitrite source equivalent to a natural curing agent.

Differential Proteome Analysis of Breast and Thigh Muscles between Korean Native Chickens and Commercial Broilers

The Korean native chickens (Woorimotdak™, KNC) and commercial broilers (Ross, CB) show obvious differences in meat flavor after cooking. To understand the contribution of protein and peptide for meat flavor, 2-dimensional (2-D) gel electrophoresis and matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) mass spectrometry was performed. A total of 16 protein spots were differentially expressed in the breast and thigh meat between the two breeds. A total of seven protein spots were represented by different levels between KNC and CB for breast meat. Among them three protein spots (TU39149, TU40162 and TU39598) showed increases in their expressions in KNC while other four protein spots (BU40125, BU40119, BU40029 and BU39904) showed increases in CB. All nine protein spots that were represented by different levels between KNC and CB for thigh meat showed increases in their expression in KNC. Phosphoglucomutase 1 (PGM 1), myosin heavy chain (MyHC), heat shock protein B1 (HSP27), cytochrome c reductase (Enzyme Q), Glyoxylase 1, DNA methyltransferase 3B (DNA MTase 3) were identified as the main protein spots by MALDI-TOF mass spectrometry. These results can provide valuable basic information for understanding the molecular mechanism responsible for breed specific differences in meat quality, especially the meat flavour.

Effect of phosvitin on lipid and protein oxidation in ground beef treated with high hydrostatic pressure.

In this study, we aimed to examine the effect of phosvitin on lipid and protein oxidation of raw and cooked ground beef treated with high hydrostatic pressure (HHP). Ground beef patty with 0, 500, or 1000 mg phosvitin/kg meat was treated with HHP at 0.1, 300, or 600 MPa. Half of the patties were used in a raw meat analysis, and the other half were used in a cooked meat analysis. Phosvitin and HHP treatment at 300 MPa synergistically reduced microbial growth, and HHP treatment at 600 MPa reduced microbial counts to undetectable levels (<1 log CFU/g) throughout the length of the study in all samples. Phosvitin delayed lipid and protein oxidation in HHP-treated cooked and raw ground beef, respectively. However, phosvitin had no effect on the color changes of raw ground beef attributable to HHP. The results indicated that phosvitin could enhance the stability of lipids and proteins but not color changes of raw ground beef caused by HHP.

Evaluation of a Dielectric Barrier Discharge Plasma System for Inactivating Pathogens on Cheese Slices

The objective of this study was to evaluate the potential use of a dielectric barrier discharge (DBD) plasma system to improve microbial safety of sliced cheese. The atmospheric pressure plasma (APP) effect on visual appearance and a sensory evaluation were also carried out. The number of Escherichia coli inoculated on cheese slices decreased by 0.09, 0.47, 1.16 and 1.47 log cycles with helium (4 liters/min (lpm)) and 0.05, 0.87, 1.89 and 1.98 log cycles with He/O2 mixture (4 lpm/15 standard cubic centimeters per minute), after being treated with plasma for 1, 5, 10, and 15 min, respectively. Significant reductions were also observed in Staphylococcus aureus inoculated onto cheese slices ranging from 0.05 to 0.45 log cycles with He and from 0.08 to 0.91 log cycles with He/O2-treated samples, respectively. Adding oxygen resulted in a significant increase in inactivation of both pathogens. No visible change in the plasma-treated cheese slices was observed even though the instrumental analysis showed a significant decrease in the L*-value and an increase in the b*-value. The cheese slices were damaged after 10 and 15 min of plasma treatment. In addition, significant reductions in sensory quality including flavor, odor, and acceptability of plasma-treated cheese slices were observed. The results indicate that the DBD plasma system has potential for use in sanitizing food products, although the effect was limited. Further development of the APP system is necessary for industrial use.

Flexible thin-layer plasma inactivation of bacteria and mold survival in beef jerky packaging and its effects on the meat's physicochemical properties

The aims of the present study were to examine the use of a flexible thin-layer plasma system in inactivating bacteria and mold on beef jerky in a commercial package and to evaluate the physicochemical changes of the jerky. After plasma treatment for 10min, Escherichia coli O157:H7, Listeria monocytogenes, Salmonella Typhimurium, and Aspergillus flavus populations on the beef jerky were reduced by approximately 2 to 3Log CFU/g. No significant changes in metmyoglobin content, shear force, and myofibrillar fragmentation index were found in the plasma-treated beef jerky. On the other hand, the peroxide content and L⁎ value were decreased whereas the a⁎ and ΔE value were increased in the plasma-treated sample. Sensory evaluation indicated negative effects of plasma treatment on flavor, off-odor, and overall acceptability of the beef jerky. In conclusion, the flexible thin-layer plasma system could be employed as a means for decontamination of beef jerky, with slight changes to the physicochemical quality of the product.

Ex Vivo Responses for Interferon‐gamma and Proinflammatory Cytokine Secretion to Low‐Molecular‐Weight Antigen MTB12 of Mycobacterium tuberculosis during Human Tuberculosis

MTB12 protein, also called CFP‐2, is a major and early secreted component of Mycobacterium tuberculosis. However, its role during mycobacterial infection has been poorly characterized. In this study, we purified the native MTB12 protein and investigated the profile of MTB12‐induced cytokines [interferon (IFN)‐γ, tumour necrosis factor (TNF)‐α and interleukin (IL)‐6], in early tuberculosis (TB) patients (n = 20) and healthy controls (n = 35). The cytokine profiles were compared with those induced by the 30‐kDa antigen (Ag). In healthy controls, MTB12‐induced IFN‐γ production was markedly decreased in peripheral blood mononuclear cells compared with 30‐kDa Ag‐induced IFN‐γ. In TB patients, the mean IFN‐γ level induced by MTB12 was lower than that induced by the 30‐kDa Ag, albeit the difference was not significant. After 2 months of anti‐TB therapy, both the MTB12‐ and 30‐kDa‐induced IFN‐γ levels were significantly increased in TB patients. MTB12‐induced TNF‐α and IL‐6 levels were prominently upregulated in monocyte‐derived macrophages from TB patients, but they were not significantly different from those induced by the 30‐kDa Ag. Further, the activation of p38 mitogen‐activated protein kinase and extracellular signal‐regulated kinase was required for the induction of TNF‐α and IL‐6 by MTB12, as well as by the 30‐kDa Ag. Collectively, these data suggest that the MTB12 protein plays an essential role for proinflammatory responses through the MAPK pathway during the early stages of human TB, even though its T‐cell immunoreactivity is weaker than that of the 30‐kDa Ag.