Commonly eaten fish, meat and other protein-containing foods show some level of mutagenic activity following normal cooking such as broiling, frying, grilling, roasting etc. The main food mutagens found in cooked products are $quot;heterocyclic aromatic amines$quot; . Several of them have been shown to be carcinogenic in rodent and suggested to be relevant for human cancer etiology. This review summarizes the chemistry, formation, occurrence and toxicity of food-borne heterocyclic aromatic amines. Factors that influence the formation of them are also discussed with special emphasis on dietary factors. From a health safety point of view, it is desirable to estimate the intake of heterocyclic amines via foods, and reduce or prevent the formation of food mutagens.

본 연구에서는 대변형 쉘 구조물에 효과적인 적응적 유한요소 자동생성 기법을 제안한다. 사후 오차평가에 기초하여 기하학적 비선형 해석시 각 하중 단계에서의 요소 재생성에 초점을 맞추고 있다. 응력오차로부터 얻어진 요소크기 함수로 등고선을 구성하고, 요소 재생성 기법으로 advancing front method의 일종인 패이빙법(paving method)을 이용하여 적응적 요소 자동생성을 수행한 결과, 그 유용성을 확인하였다.

We checked the presence of phospholipase A2(PLA)2 which could split the ester bond at the position 2 in the glycerol backbone of glycerophospholipids, in the cells of hyperthermophiles of Pyrococcus horikoshii and Sulfolobus acidocaldarius. The results obtained are as follows; (1). Pyrococcus horikoshii cells were grown in obligate anaerobic conditions at 95℃ and they needed sulfur as energy source instead of oxygen, while Sulfolobus acidocaldarius species grew well in the aerobic medium (pH 2.5) containing yeast and sucrose at 75℃. (2). Pyrococcus horikoshii cells produced phospholipase A2 in the cell culture media although this species did not show lipase activity at least in the pH range of 1.5 ~ 3.5. Sulfolobus acidocaldarius cells produced lipase hydrolyzing triacylglycerols such as triolein, but did not split any kind of phospholipids used as substates. (3). The compound of 1-decanoyl-2-(p-nitrophenylglutaryl) phosphatidylcholine was not suitable for a substrate in this experiment, though frequently used as a subtrate for checking presence of phospholipase A2, for its decomposi-tion in this experiment. The L-α-phosphatidylcholine-β-[N-7-nitrobenz-2-oxa-1, 3-diazol]aminohexanoyl-γ-hexadecanoyl labelled with a fluorescent material, did not show any migration of acyl chains in the molecule during the reaction with phospholipase A2 under a hot condition. (4). Phospholipase A2 in the cells of Pyrococcus horikoshii, showed the optimum activity at pH6.7~7.2 and 95~105℃, respectively, and was activated by addition of calcium chloride solution. Andthe phospholipase A2 specifically hydrolyzed glycero-phospholipids such as phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine and phosphatidyl inositol, but could not split phospholipid containing ether bonds in the molecule such as DL -α-phosphatidylcholine-β-palmitoyl-γ-O-hexadecyl, DL-α-phosphati- dylcholine-β- oleoyl-γ-O-hexadecyl, DL-phosphatidylcholine-dihexadecyl.

반응생성에 의한 Ti/TiB 복합재료를 제조하기 위한 반응분말(TiB2, B4C), 소결온도, 소결시간을 결정하기 위하여 제조조건에 따른 반응생성상, 미세조직, 상대밀도 등을 조사하였다. 제조된 복합재료의 기계적 성질은 상온 압축항복강도로 평가하였다. 복합재료를 제조하기 위하여 혼합하는 TiB2반응분말의 경우 1300˚C, B4C 반응분말의 경우 1400˚C의 소결온도가 최적조건임을 확인하였다. 본 공정에 의해서 제조된 복합재료의 압축항복강도는 비교재인 Ti-6Al-4V 보다 모두 우수하였다. 또한 TiB2반응분말에 의해서 제조된 복합재료가 B4C 반응분말에 의해서 제조된 복합재료보다 우수한 압축항복강도를 나타내었다. 이는, 압축시험한 복합재료에서의 균열전파양상을 조사한 결과, 강화상과 기지간의 접합특성을 B4C 반응분말에 의한 복합재료의 접합특성보다 우수하였기 때문이었다.

Three mixtures of elemental powders of Al-25at.%Ti, 48at.%Ti and 70at.%Ti were offered to ball milling process for the formation of intermetallic compounds of , AlTi and . Ballmilling or attrition process were carried out at the condition of rotaing speed of 110 or 350 rpm at torr vacuum or argon atmospheres. phases were fully obtained by heat treatment for 1 hors at with Al-25at.%Ti composition mixtures milled by 100 hours. The amorphous phase was completely formed at the composition of Al-48at.%Ti mixed powders by milling 100hours at the 50 to 1 weight ratio of ball to powder, and AlTi compounds were obtained by heat treament. In the case of Al-70at%Ti mixed powders milled for 100 hours, and intermetallic compounds were formed by heat treatment for 1 hour at . By attrition milling of 350rpm for 10 hours, phase was formed completley after heat treatment for 1 hour at .

An enzyme-linked immunosorbent assay (ELISA) was established for the detection of zearalenone by using monoclonal antibodies produced by Z-M-26 hybridoma cells when injected into a mouse and zearalenone-oxime-OVA conjugate. Zearalenone-oxime-OVA conjugates were diluted with carbonyl buffer, coated to 96 well microtiter plates at 4℃ overnight and blocked with 1% BSA overnight. One thousand times diluted antibody solution together with standard zearalenone or sample was added to 96-well microtiter plates and stood overnight. A secondary antibody conjugated with HRP was added and an hour later, enzyme substrate (TMBZ) solution was added for color develpment. After 30 minutes, coloring reaction was terminated by adding 2 N H₂SO₄ and the O.D. was measured at 450 nm. Detection range of this method was about 0.1-100 ppb. The established indirect competitive ELISA method was suitable for a rapid and effective analysis of zearalenone in agricultural products.

Representive cured products such as ham and sausage produced in Korea were purchased at retail and cooked using heating tools such as a gas range (GR), an electric range (ER) and electric range after boiled (BE). Changes of N-nitrosamine (NA), nitrate and nitrite in the cured meats containing$lt;2.0 ug/kg of N-nitrosodimethylamine (NDMA) were checked and analyzed during their cooking process. Contents of nitrate and nitrite in ham products prior to cooking were 2.0 and 1.8 mg/kg, respectively; their contents in regular hams were slightly increased, but those of nitrate in press hams were decreased while those of nitrite were increased during its cooking process. Their contents in sausage products were 1.8 and 0.9 mg/kg; those of nitrate were decreased, while nitrite were slightly increased during its cooking process. NDMA detected only NA in all the collected cured products. Changes of NDMA, regardless of cooking methods, tend to drastically increase in all samples after their cooking; Its contents were increased by average 6.0-70.7 times in the GR samples, by average 2.4-39.2 times in the ER samples and by average 7.0-56.3 times in the BE samples. Virtually, the fact that all of this nitrosamine appeared to arise by the action of precursor such as NO_x was produced during the cooking of cured products.

This experiment was conducted to study occurrence of N-nitrosamine (NA) and its precursors such as nitrate and nitrite. For the experimental samples, 26 kinds of commercial hams and 30 kinds of sausages produced in Korea were purchased. The nitrate and nitrite were positive in all of the collected samples; nitrate levels were by average 4.4-9.2 mg/kg and nitrite ones were by average 1.3-3.6 mg/kg. The contents of nitrate and nitrite were detected higher in sausage than in ham. Especially, nitrate contents were contained higher in lyoner sausage prepared with the mixture of meat and fish, while nitrite contents were contained higher in the meat only mixture. N-nitrosodimethylamine (NDMA) among the analyzed 7 kinds of NA was detected only in ham and sausage; its contents were outstanding in lyoner sausage which was prepared with only meat and pork sausage, and then regular ham was the next one in its order, but its contants were detected by average $lt;0.5 ug/kg in press hams added vegetable.

The effect of ripening temperature, pH and salinity on the formation of N-nitrosamine (NA) during Kimchi fermentation and in vitro was studied, respectively. During Kimchi fermentation for six weeks at cold storage temperature (4℃) and room temperature (16 ±2℃), the contents of nitrite and dimethylamine (DMA) showed variation at room temperature but no variation at cold storage temperature. The maximum generation of nitrosodimethylamine (NDMA) resulted low content (2.69 ug/kg) at cold storage temperature but started to increase after one week fermentation and reached to the 18-fold higher generation (49.6 ug/kg) at room temperature. During Kimchi fermentation, no correlation was observed between the variation of nitrite and DMA content and the generation of NDMA. However, pH showed effective relation to NDMA generation such as the highest NDMA generation was obtained at lowest pH 4. During in vitro test, higher temperature and lower pH resulted more NDMA generation and generation amount was affected more by pH. Also, the salinity of Kimchi provided inhibitory effects on the formation of NDMA. NDMA was produced 5.86 ug/kg at normal salinity (2.5%) but 90.9 ug/kg at lower salinity (15%) after three week. The higher salinity showed lower formation of NDMA in vitro test, too.

강원도 원주일원의 토양에서 분리한 Streptomyces sp. SK-862 균주는 단백질 분해효소인 트립신에 대하여 강한 저해작용을 하는 물질을 생산하였다. 저해물질의 정제는 n-butanol 용매로 추출한 후 합성수지인 Amberite XAD로 흡착하였으며 ODS-HP-LC, GPC HPLC 순으로 정제하였다. 정제된 물질은 pH 2-10에서 안정하였으며 80℃에서 60분간 온도 처리하였을 때에는 65%가 실활되었다. 물, 메탄올, 에탄올, 부탄올에는 잘 용해되었으나 비극성용매인 클로로포름, 에틸아세테이트에는 녹지 않았다. TLC에서의 R_f값은 n-butanol : methanol : water(5 : 3 : 1 v/v)의 용매에서 0.56, ethanol : ammonium hydoxide : water(8 : 1 : 1 v/v) 0.23이였다. 자외선 흡수스펙트럼 조사에서는 259nm에서 최대흡광도를 보였으며, 당 반응은 검출되지 않았으나 닌히드린과 반응하였다.

본 연구는 단백질 분해효소 저해물질을 탐색하고자 방선균을 선택적으로 분리할 수 있는 colloidal chitin 고체배지를 사용하여 강원도 원주 일원의 토양에서 Streptomyces sp. SK-862를 선별하여 배양여액으로부터 단백질 분해효소 저해물질을 분리하였다. 최적의 배양온도와 초기 pH는 각각 28℃와 8.5이었다. 가장 적합한 배지조성은 1.5% glucose, 0.5% peptone, 0.1% K_2HPO_4, 0.05% CaCO_3이었으며, 60시간 동안 진탕 배양하였을 때 저해물질 생산이 최대가 되었다.

α-아밀라제의 강력한 저해물질을 생성하는 분리주 BY-445를 토양으로부터 분리하여 이를 동정하였다. 이 균주의 기균사는 나선형이며, 포자의 표면은 침상형(spiny)이었다. 멜라닌 색소 및 용해성 색소는 음성이었으며, 단백질 및 전분 분해력은 강한 편이었다. 세포벽 성분중 diaminopimelic acid는 LL형이었고 세포의 지방산은 16 : 0 iso가 25.30%, 15 : 0 anteiso는 16.19% 그리고 16 : 0이 13.16%였으며 이 균주는 Streptomyces violaceusniger와 유사하였으나 몇몇 배양학적, 생리학적 특성이 달라 Streptomyces sp. BY-445로 명명하였다.

This study was performed to investigate the possible effect of Bacillus subtilis which is the predominant species of bacteria in Korean soy sauce, soy paste, and Meju (soybean cake) on the growth and aflatoxin production of Aspergillus parasiticus ATCC 15517. The microorganisms were grown in a modified APT broth and incubated at 30℃ for 12 days. Aflatoxins were determined using high performance liquid chromatography (HPLC). A remarkable inhibition of the growth of Aspergillus parasiticus was observed during the incubation period when in the presence of B. subtilis (mixed culture). Dry mycelial weight in the mixed culture was significantly reduced by 85.3% in comparison to the control at the end of the incubation period (p$lt;0.01). Lower levels of aflatoxins were found in the mixed culture than in the monoculture. At the end of the incubation period aflatoxin production was significantly inhibited by more than 50% (p$lt;0.05). These results indicate that B. subtilis mainly inhibites the growth and aflatoxin production of toxigenic Aspergillus in Meju, soy sauce and soy paste. Although its effect on aflatoxin production was less pronounced, we . could expect more inhibition by another bacteria related with fermentation in Meju.

The study was focused to investigate the effect of nitrosodimethylamine (NDMA) formation due to nitrosamine (NA) precursor and/or inhibitor addition to Kimchi during the fermentation of Kimchi at room temperature (16±2℃). The addition of nitrite and dimethylamine (DMA) to Kimchi showed the average 32-fold (21.3-113.9 ug/kg) and 9-fold (1.3-40.3 ug/kg) higher NDMA formation than control (0-5.6 ug/kg), respectively. Also, the addition of both nitrite and DMA resulted in the increase of NDMA formation to average 42-fold (39.4-155.7 ug/ kg) higher than control. On the other hand, the addition of 4 mM ascorbic acid to Kimchi with nitrite and DMA inhibited the formation of NDMA down to 71.3% of control. However, the addition of cysteine and erythorbic acid affected no inhibition to NDMA formation during the test. The addition of sodium sulfite increased NDMA formation. Accordingly, this showed that the amount of ascorbic acid generated during Kimchi fermentation played an important inhibition role for NA formation.