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Watery kimchi is a traditional fermented food served with its soup. In this study, we collected 21 samples of yeolmu mulkimchi (YMK), dongchimi(DC), and nabakkimchi (NK), respectively, which are the most popular watery kimchi in Korea. A composite sample of each watery kimchi was prepared for estimation of their bioactive compounds and antioxidant activities. Of the three kimchi types, YMK had the highest total carotenoid content (63.78 ± 4.88 mg/100 g, of which lutein, capsanthin, and β-carotene were the main carotenoids), and DC had the lowest (3.50 ± 0.12 mg/100 g). YMK also had the highest contents of chlorophyll (250.1 ± 3.91 mg/100 g), ascorbic acid (447.16 ± 8.95 mg/100 g), and capsaicinoids (2.51 ± 0.09 mg/100 g) compared to DC and NK. The lactic acid content was highest in NK (582.72 ± 29.10 mg/100 g). Moreover, YMK showed significantly higher antioxidant activity (ABTS and DPPH) than DC and NK (p< 0.05). Chlorophyll and antioxidant activity showed a strong positive correlation (p< 0.01). The results of this study highlighted watery kimchi as a potentially valuable source of bioactive compounds, and the carotenoids and capsaicinoids were affected by the supporting ingredients used in watery kimchi. Furthermore, watery kimchi provides 4.11% of the recommended daily intake of vitamin A according to the 2020 Korean dietary reference intakes.

Perfluorinated compounds (PFCs) are widely used in industries, and have become common environmental pollutants. Consumption of aquatic foods and its processed products can result in the accumulation and maintenance of PFCs in organs of human body, which can lead to toxic consequences and poisoning. The aim of this study was to evaluate the reducing effects of PFC contents in fish cake and swimming crab by different cooking conditions. Fish cake was processed with blanching, boiling, frying, stir-frying and swimming crab was pretreated with soaking and cooked by steaming and stewing. The change of PFCs were determined using LC–MS/MS. Boiling reduced the total PFCs in fish cake by up to 45.9%. As for swimming crab, soaking, steaming and stewing have reduced 65.7%, 17.6% and 13.3% of PFCs, respectively. These results suggest that cooking method involving water addition and high-temperature heating would be effective at reducing PFCs (PFOA especially) in food.

The individually quick-frozen (IQF) method is used to produce high-quality frozen food by freezing an individual piece of food separately from the remaining food. In this study, the effect of various freezing and thawing combinations on the quality preservation of Pleurotus eryngii(king oyster mushroom) was investigated. For this purpose, diced and mini P. eryngiimushrooms were frozen by natural freezing (NF, − 20 °C) or IQF (− 62.5 °C and speed 8.23 m/s) methods and thawed using three thawing methods—flowing water thawing (FT, 4 °C), microwave thawing (MT, 620 W), or natural air convection thawing (NT, 20 ± 5 °C). Quality characteristics, such as thawing loss, texture, water holding capacity, color, microstructure, and sensory quality, were evaluated. MT showed the most rapid thawing time, followed by FT and NT for all the samples. The results showed that thawing curve, water holding capacity, and hardness of IQF samples were better than those of NF samples after NT, FT, and MT. Scanning electron microscopy analysis revealed that cell integrity of the IQF sample was better than that of the NF sample. MT is the fastest of the thawing methods, but thawing after NF yielded a sample closest to the fresh mushroom sample. Therefore, when combined with NT, IQF minimized the quality changes in frozen diced and mini P. eryngiimushrooms. This study showed that the IQF technology can be used as a new preservation and distribution method of mushroom.

Biogenic amines are formed by microorganisms during fermentation. Major biogenic amines found in food are histamine, tryptamine, 2-phenylethylamine, putrescine, cadaverine, tyramine, spermidine, and spermine. Doenjangis a traditional fermented food made of soybean and is widely used for cooking of various foods in Korea. During fermentation, harmful substances such as biogenic amines could be produced in Doenjang.In this study, we examined the types and quantities of biogenic amines in commercial Doenjangand analyzed the destructive effects of cooking on biogenic amines in Doenjang. Biogenic amines were identified by high-performance liquid chromatography with a fluorescence detector (HPLC-FLD). The concentrations of biogenic amines in commercial Doenjangdepended on the manufacturer and ranged from none detected to 415.08 mg/kg. Putrescine and tryptamine were the most abundant biogenic amines in Doenjangsamples, whereas cadaverine was not detected in any commercial samples. For all cooking conditions, tryptamine, 2-phenylethylamine, putrescine, and tyramine were detected in Doenjang, and their concentrations decreased significantly after 10 min of roasting. The total concentration of biogenic amines in Doenjangsoup was not changed significantly by boiling. Therefore, roasting, unlike boiling, can be considered more effective at reducing the amount of biogenic amines in Doenjang.

Baechuand radish are the major by-products generated from kimchi factories. Because vegetable and fruit by-products have abundant functional ingredients, the availability of them as a source of bioactive compounds is gaining attention. The objective of this study was to determine the feasibility of using kimchi by-products as sources of functional ingredients. For this purpose, 13 by-product samples were collected from different kimchi factories and analyzed for their sugar contents, total dietary fiber (TDF), antioxidant capacity, water holding capacity (WHC), viscosity, and specific gravity. The dietary fiber contents in kimchi by-product cabbage powder and radish powder were 27.37–49.54 and 30.19–62.81 %, respectively. TDF, WHC, and antioxidant capacities of kimchi by-products were equally as high as those of other by-products that are reused in industry. These results suggested that kimchi by-products have the potential as a new agro-industrial by-product that could be recycled as valuable sources of dietary fibers.

There has been an increasing interest in the use of natural plant materials as alternative food preservatives. We examined the antimicrobial effects of natural plant materials used as additives against foodborne pathogens in laboratory media and Sulgidduk, oriental-style rice cakes. Cinnamon, mugwort, and garlic powder solutions (3%) were tested for their antimicrobial activities against pathogens in laboratory media. Sulgidduk prepared with different amounts of cinnamon powder (1, 3, and 6%) was inoculated with a Staphylococcus aureusor Bacillus cereuscocktail. The samples were air or vacuum packaged and stored at 22 ± 1°C for 72 h, and microbial growth was determined. Cinnamon powder showed more inhibitory properties against pathogens such as Salmonella entericaserovar Typhimurium, Escherichia coliO157:H7, Listeria monocytogenes, S. aureus, and B. cereusthan did mugwort or garlic powder. The populations of S. aureusand B. cereusin Sulgidduk containing cinnamon powder were significantly lower than in the control during storage time. Different packaging methods did not result in a significant difference in pathogen growth. In a sensory evaluation, Sulgidduk containing 1 and 3% cinnamon powder did not significantly differ from the control sample in any of the attributes tested other than flavor. These results indicate that natural plant materials such as cinnamon powder could be used as food additives to improve the microbiological stability of rice cakes.

Abstract: Escherichia coli O157:H7 infection has been implicated in a number of outbreaks of illness linked to the consumption of foods. Handling raw meat contaminated with E. coli O157:H7 in the kitchen could easily contaminate the surface of cutting boards. Thus, levels of cross-contamination of E. coli O157:H7 from ground beef to cutting boards made of different materials and effects of cleaning methods on reducing E. coli O157:H7 were evaluated. Four types of cutting boards (wood, polyethylene, polypropylene, and acrylic) were selected and contaminated with ground beef inoculated with E. coli O157:H7. Levels of cross-contaminated E. coli O157:H7 on boards were then evaluated. For evaluation of cleaning methods, wiping with dry paper towel, wet paper towel, alcohol paper towel, chlorine paper towel were used to clean the contaminated cutting boards. Initial population of pathogens was 6.09 log CFU/g in ground beef. After 1 h contamination of the inoculated ground beef on the cutting boards, no significant difference were observed in levels of cross-contaminated E. coli O157:H7 depending on the cleaning materials except for the normal polyethylene surface. Order of efficacy in removing E. coli O157: H7 was as follows: alcohol > chlorine > wet > dry paper towel. Cleaning with alcohol sanitizer appeared as the most effective cleaning method for reducing E. coli O157: H7 population on kitchen cutting boards. These results could be used to develop kitchen safety guidelines for preventing foodborne outbreaks.