The biodegradation of high concentration of benzoate by enrichment culture with Pseudomonas sp. was investigated. During 50 days continuous culture, average of removal rate of benzoate and COD were 90% and 83%, respectively. And the enzymatic activity of catechal 2,3-dioxygenase was determined in the continuous culture but not Catechol 1,2-dioxygenase. On the other hand, Pseudomonas sp in the culture was investigated with SEM and the result was revealed that the cell shape was more demage according the higher concentration of benzoate.
Microbial distribution as well as content of salt and preservatives in side dishes was investigated by analyzing cell count of viable cells, coliform bacteria and food poisoning bacteria of sliced squid bokum and anchovy bokum, purchased at 17 dift'erent department stores and 2 different traditional markets in Seoul, which are most preferred by many consumers to any other side dishes available in the market. 6.2 × 10³-1.2 × 10^5 cells/g of viable cells was detected in 19 different samples of the sliced squid bokum, among which samples collected at the traditional markets counted the highest number of viable cells. 16 samples of the sliced squid bokum and 14 samples of the anchovy bokum contained 10³-10^8 cells/g of coliform group. However food poisoning bacteria were not detected in all the samples tested. Salt content was 2.42-4.89 %w/w and 2.28-6.46 %w/w for the sliced squid bokum and the anchovy bokum respectively. Analysis of preservatives by HPLC such as sorbic acid, benzoic acid, dehydroacetic acid and another 6 kinds of esters resulted that 1.0× 73.8 mg/100 g of sorbic acid was detected in the 19 samples of the sliced squid bokum, while only 6 samples of the 15 anchovy bokum samples contained sorbic acid.
Time-temperature relationship and microbiological quality were assessed and critical control points were identified through hazard analysis during the phases of production in two different packaged meals (Dosirak) manufacturing establishments (A, B:Kim Pab). Microbiological tests on foods, equipments and utensils were done according to standard procedures and included total plate count, coliforms and fecal coliforma. The results of the study are summarized as follows : time-temperature control management was needed because timetemperature abuse more than 8 hours at dangerous temperature zone (5-60℃) was observed from pre-preperation to distribution phase; Poor sanitary practices of employees were observed in hand washing and using disposable gloves; Microbiological analysis results of equipments and utensils showed possible cross-contamination risks when foods were contacted with them; Kim Pab needed thorough quality control because it included various mixed ingredients of cooked and uncooked and had many apportunities of cross-contamination either by equipments or hands through whole production processes.
Based on microbiological-chemical test results under simulated time-temperature conditions, total plate count, coliform and volatile basic nitrogen were selected as effective quality indicators for estimating probable shelf-life of Kim Pab dosirak marketed in convenience stores, and shelf-life at each storage temperature was calculated from regression equation between effective quality indicator standard limit and storage time. Estimated shelf-lives of Kim Pab Dosirak were 27, 3 and 2 hours respectively under 10℃, 20℃ and 30℃. Because shelf-life was especially affected by initial values, regression analysis between initial effective quality indicator values and storage hours was performed for the estimation of probable shelf-life of Kim Pab during storage at 10, 20 or 30℃.
D_(10) values obtained for radiation alone in Bacillus subtilis and Clostridium perfrigenes were 0.35-0.48 kGy in vegetative cells, and 2-2.08 kGy in spores, respectively. Irradiation dose of 24 kGy completely inhibited spores. In the case of heat treatment, D_(50, 60) values ranged from 10 to 14 minutes in vegetative cells, and D_(70, 80, 90), values ranged from 10 to 140 minutes in spores. In the case of combined treatment with heat and radiation, D_(10) values ranged from 1 to 1.25 kGy in vegetative cells, and from 3.42 to 3.61 kGy in spores. Thus, resistance of cells to gamma radiation did not seem to be influenced by pre-heating.
One kind of fungus was isolated and identified from comtaminated red-ginseng in order to give fundermental data for improving hygienic quality of ginseng product. The isolated strain was identified as Aspergillus sp. Hyphae of the strain had septum structure. The strain showed vesicle and aterigmata structure which were typical characteristics of Aspergillus species. The growth of the strain was slightly inhibited by sodium benzoate and potassium sorbate at a concentration of 0.05%. The strain showed no growth at 4.0% potassium sorbate. The isolated strain Aspergillus sp. showed no significant degradation in the presence of red-ginseng saponins.
Irradiated and non-irradiated Korean medicinal herbs were extracted by water and 70% ethanol. Antimicrobial activity of these extracts were investigated against selected food hygiene microoganisms. The ethanol extracts of the non-irradiated Agrimonia pilosa ledebour japonica Nakai, Curcuma longa Linne and Angelica gigas Nakai were completely inhibited on four species of bacteria, such as Vibrio parahaemolyticus, Clostridium perfringenes, Bacillus subtilis and Staphylococcus aureus. Also, above four strains did not have antibacterial activity in the water-ethanol mixtures. Futhermore, the ethanol extracts of the non-irradiated Agrimonia pilosa ledebour Japonica Nakai, Curcuma ledoaria Roscoe, Curcuma longa Linne and Scutellaria baikalensis George were shown inhibitory effects against Aspergillus flavus and Penicillium islandicum. And the water extract of Scutellaria baikalensis George was the same effect to these molds. Essentially the same results were observed when samples irradiated at a dose of 10 kGy.
Korean and Chinese sesames were subjected to microscopic observation and instrumental determination of fatty acid composition and sesamolin/sesamin ratio to obtain basic data for discriminating each other. The overall appearance of both samples was differently observed by stereo microscope (X8). Fatty acid composition of sesame oils, extracted from both samples with different roasting degrees, showed a similar pattern although Chinese samples cointained about 6% higher content of stearic acid and 47% lower content of linolenic acid than Korean ones. The sesamolin/sesamin ratio was remarkably lower(0.39) in Chinese samples than Korean (0.67-0.72), showing a variation depending on producing districts. Roasting degrees of raw sesames little influenced their composition of fatty acid and sesamolin/sesamin ratio. Based on the above results, it is considered that the comparison between domestic and Chinese sesames in view of their stearic and linolenic acid contents and sesamolin/sesamin ratio might be one of the potential criteria in discriminating their production origins.
For the purpose of improving hygienic quality of health-foods, sterilization effects of y ray and ozone on microoganisms associated with food cultured in the media and contaminated in Angelica keiskei powder were investigated. Ozone was immersed in water and sprayed in air, on the concentration of 3 mg liter^(-1) at an air flow rate of 5 liter min'. Test strains cultured in the media completely inhibited by γ-ray at irradiation doses of 0.25--2 kGy. In the case of ozone, test bacteria inactivated after treatment of 10-20 minutes, but test mold, Aspergillus llavus was not effective. Strains contaminated in Angelica keiskei powder completely inhibited by γ-ray at irradiation doses of 2.5-7.5 kGy. However, when the powder was sprayed with ozonized air for 10 hours, Bacillus subtilis and Staphylococcus aureus among five strains were eliminated.