• Food Science of Animal Resources
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• v.32 no.5
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• pp.540-544
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• 2012

During heat treatment and storage of milk, deteriorative reaction takes place, which consequently influence on the milk quality. In this study, formation of lactulose and furosine under different thermal conditions and storage conditions, and the ratio of lactulose and furosine (LU/FU) in presence of reconstituted milk powder were determined to establish chemical indicators for heat damages of milk and the adulteration of fresh milk in dairy field. The lactulose and furosine contents linearly increased with increased heating temperature and heating time. It showed high correlation between the formation of lactulose and furosine, and the treatment temperature and time (p<0.05). The lactulose and furosine concentration of HTST milk and UHT milk noticeably increased during storage at $30^{\circ}C$, but there was no noticeable increase of lactulose and furosine concentration at lower storage temperature. In the raw milk, the lactulose and furosine contents greatly increased with the addition of reconstituted milk. The increase level of furosine was much higher than that of lactulose, which consequently resulted in the lower LU/FU ratio in milk as increase of added reconstituted milk amounts. As comparing with raw milk, there was more than twice reduction in LU/FU ratios after the addition of reconstituted milk (p<0.05). It can be concluded that lactulose and furosine are suitable milk quality indicators of heat damage and for demonstrating improper addition of reconstituted milk powder.

• Journal of Dairy Science and Biotechnology
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• v.36 no.1
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• pp.49-71
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• 2018

Heat treatment is the most popular processing technique in the dairy industry. Its main purpose is to destroy the pathogenic and spoilage bacteria in order to ensure that the milk is safe throughout its shelf life. The protease and lipase that are present in raw milk might reduce the quality of milk. Plasmin and protease, which are produced by psychrotrophic bacteria, are recognized as the main causes of the deterioration in milk flavor and taste during storage. The enzymes in raw milk can be inactivated by heat treatment. However, the temperature of inactivation varies according to the type of enzyme. For example, some Pseudomonas spp. produce heat-resistant proteolytic and lipolytic enzymes that may not be fully inactivated by the low temperature and long time (LTLT) treatment. These types of enzymes are inhibited only by the high temperature and short time (HTST) or ultra-high temperature (UHT) treatment of milk.

• Food Science and Biotechnology
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• v.17 no.1
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• pp.58-65
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• 2008

To see the possibility of irradiation as an alternative to ultra high temperature (UHT) sterilization, the quality characteristics of milk were analyzed. Milk treated by UHT ($135^{\circ}C$ for 4 sec) and irradiation at higher than 3 kGy showed no viable counts after 7 days of storage at $4^{\circ}C$. The contents of certain amino acids of milk, such as Arg, Asp, Glu, Ile, Leu, Lys, Pro, Ser, Thr, and Tyr, were lower in irradiated groups at 10 kGy than in UHT-treated one, but no difference was observed between irradiated milks at less than 5 kGy and UHT. The capillary electrophoresis (CE) patterns of the milk irradiated at 10 kGy showed a similar trend to the raw milk, low temperature long time (LTLT, $63^{\circ}C$ for 30 min), and high temperature short time (HTST, $72^{\circ}C$ for 15 sec) treated. However, the CE pattern of UHT-treated milk was different. Rennet coagulation test agreed with the CE results, showing that all milk samples were coagulated by rennet addition except for UHT-treated milk after 1 hr. These results suggest that irradiation of milk reduce the content of individual amino acids but it may not induce severe conformational change at a protein level when compared with UHT treatment.

• Korean Journal of Microbiology
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• v.1 no.1
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• pp.48-50
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• 1963

The authors have investigated about the microbial contamination of goods which is a criterion of hygienic control. Conducting on investigation, a special attention has been paid on the rate of microbial contamination in the goods, especially in manufacturing process of the softdrink. The authors also made an experiment on total microbes which is the criterion of contamination in each step of the process and in raw materials together with materials to be used for subdividing. Results obtained were as follows : 1) The orgin of microbial contamination was found in bottle cap and in tap water, that is, there appeared 9 colony per ml in bottle cap and 31-74 colony per ml in tap water, respectively. 2) It was found that microbial contamination are 4 colony per ml in average through year. However, it appeared 1 colony per ml in winter and 8 colony per ml in summer. 3) Coliform groups are not detected in goods through a year. 4) There was no variation in number of total microbes after ion exchange resin passage in purification process of tap water. 5) The number of microbes in goods are decreased when the raw materials are treated in high temperature short time (HTST) sterilization.

• Journal of the Korean Society of Food Science and Nutrition
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• v.20 no.6
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• pp.546-550
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• 1991

Changes of pH, titratible acidity, undenatured whey protein contents and the rates of loss of available lysine in market milks were investigated to find out the effective indicators for identification and classification of different heat treatment. There showed no change of both pH and titratiable acidity among the heating methods in market milks. The contents of undenatured wheyprotein per 100ml serum were determined as 413.7mg(LTLT), 341.3mg(HTSP), 6.9mg(UHT pasteurized) and 96.6mg(UHT sterilized), respectively. Distinct differences of underatured whey protein contents accoriding to the heating method could be observed. The rates of loss of available lysine in heated milks compared to raw milk showed 1.4% (LTLT), 0.2%(HTST), 6.3%(UHT pasteurized) and 4.9%(UHT sterillized), respectively. The rates of loss of available lysine were not suitable to classify the UHT heating method.

• Journal of Dairy Science and Biotechnology
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• v.35 no.4
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• pp.270-285
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• 2017

Among milk proteins, caseins are not subjected to chemical changes during heat treatment of milk; however, whey proteins are partially denatured following heat treatment. The degree of whey protein denaturation by heat treatment is decreased in the order of high temperature short time (HTST) > low temperature long time (LTLT) > direct-ultra-high temperature (UHT) > indirect-UHT. As a result of heat treatment, several changes, including variations in milk nitrogen, interactions between beta-lactoglobulin and k-casein, variations in calcium sulfate and casein micelle size, and delay of milk coagulation by chymosin action, were observed. Lysine, an important essential amino acid found in milk, was partially inactivated during heat treatment. Therefore, the available amount of lysine decreased slightly (1~4% decrease) after heat treatment, However, the influence of heat treatment on the nutritional value of milk was negligible. Nutritional value and nitrogen balance did not differ significantly between UHT and LTLT in milk. In conclusion, our results showed that heat treatment of milk did not alter protein quality. Whey proteins denatured to a limited extent during the heat treatment process, and the nutritional value and protein quality were unaffected by heat treatment.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.10 no.1
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• pp.50-63
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• 1999

Introduction：Test anxiety is a pervasive problem among high school students in Korea. While anxiety in test situations may actually facilitate the performance of some students, more often it is disruptive and leads to performance decrements. Over the past years, many child psychiatrists have become concerned with understanding the nature of test anxiety, but it is not clearly understood yet. In order to understand the nature of test anxiety, the relationship between test anxiety and depression, state anxiety, trait anxiety, temperament and family environment were examined. Methods：The Test Anxiety Inventory, Chidlren's Depression Inventory, State-Trait Anxiety Inventory, Temperamnet and Family Environment Scale Scale were administered to 576 high school students in Seoul. The relationships between test anxiety and other measures were tested using Pearson correlation coefficients and to test the causal relationship among the variables, regression analysis was performed. Results：The correlation coefficients between test anxiety and depression, state anxiety, trait anxiety, temperament and family environment scale were 0.42(p<0.01), 0.34(p<0.05), 0.38(p<0.05), 0.36(p<0.05) and -0.23(p<0.01), respectively. Regression analysis showed that only state and trait anxiety had direct causal relationship with test anxiety. Depression, temperament and family environment were indirecly related with test anxiety. Conclusions：This study indicates that the level of state and trait anxiety are directly related with test anxiety, and other variables such as temperament, family environment and depression are indirectly related with test anxiety. Thus, in order to develop the effective methods for treatment, these psychopathological characteristics should be kept in mind and the most important factors are the levels of state and trait anxiety.

• Journal of Dairy Science and Biotechnology
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• v.23 no.2
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• pp.93-98
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• 2005

Effects of heat and gamma irradiation on chemical, microbiological, and immunological changes of raw milk were compared. Free fatty acid content of milk showed increasing tendency according to the increase of heating temperature and irradiation dose, and showed similarity in UHT (ultra high temperature) and 5 kGy irradiation. Total bacterial counts and coliforms were not detected after treatment of LTLT (low temperature long time), HTST (high temperature short time), UHT, and irradiation from 1 to 10 kGy in the milk with initial microbial load at $10^3$ CFU/mL initially, but after 7 day storage, were not detected in UHT milk and that irradiated at 3 kGy or above. Heat treatment decreased (p<0.05) arginine, asparate, iso-leucine, lysine, and methionine content compared to raw milk while irradiation decreased (p<0.05) asparate, histidine, iso-luecine, leucine, and lysine content, which means irradiation could change primary structure of milk proteins. It was concluded that f kGy gamma irradiation treatment of raw milk could give a similar effect to UHT treatment in chemical and microbiological viewpoint, and may reduce allergenicity of raw milk.

• Korean Journal of Food Science and Technology
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• v.52 no.2
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• pp.177-182
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• 2020

This study evaluated the effect of steam heating, gamma irradiation, and ultraviolet (UV) irradiation on microorganism reduction in order to determine an effective sterilization method for red pepper powder. The effect of each treatment on the reduction of thermoduric bacteria and total aerobic bacteria in red pepper powder were as follows: 10 kGy gamma irradiation, reduction of 4 log and 6 log CFU/g, respectively; 12 mW/㎠ UV irradiation (264 nm UV-C), reduction of less than 1 log CFU/g; steam heating at 120℃ for 40 s, reduction of approximately 2 log CFU/g. High-temperature short-time processing at 110℃ for 30 s reduced the total bacterial count in Gochujang solution from 5.70 log CFU/g to 2.26 log CFU/g; at 121℃, the solution was commercially sterile. Steam heating resulted in 1, 2, and 4 log microbial inactivation in garlic, onion, and pepper powder, respectively. Steam sterilization, which consumers prefer over other methods, may be an effective method for reducing microorganisms in spice powders, including those in red pepper powder.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.5
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• pp.721-728
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• 2005

The physicochemical and microbial characteristics of pickled cucumber prepared with dry salting method, which has been used for industry, were investigated. Salting and storage conditions were HSHT $(30\%,\;25^{\circ}C)$, MSMT $(21\%,\;15^{\circ}C)$, MSLT $(21\%,\;0^{\circ}C)$, LSMT $(15\%,\;15^{\circ}C)$ and LSLT $(15\%,\;0^{\circ}C)$. Acidity was lower, and pH was higher in higher salt concentration as well as lower temperature groups. At the storage of 165 days, acidity and pH reached to $0.21\%$ and 4, respectively in MSLT and HSHT, of which conditions fermentation was retarded, compared to the other groups. During storage of pickled cucumber, greenness (-a) of Hunter color system showed the highest in MSLT ranged from -10.70 to -8.08, while in LSMT, the lowest to 1.17. Total microbial and lactic acid bacteria number in HTST and MSLT were the lowest than in other groups, while tile highest in LSMT. Yeast was not detected in HSHT and MSLT after 36 days of storage, while higher in LSMT Texture profile analysis exhibited that fracturability (2,318 g and 2,318 g) and hardness (849 g and 702 g) were highest in HSHT and MSLT, compared to the other groups. Scores of over-all preference for MSLT and LSLT were higher with 8.8 and 7.6, respectively, compared to the other products (p<0.05). Based on these results, lower saltiness and lower storage temperature condition was better for pickled cucumber preparation in industry.