• Korean Journal of Food Science and Technology
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• v.35 no.4
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• pp.635-641
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• 2003

A non-thermal pasteurization technology, high Pulsed Electric Field (PEF) has been thought to be a new alternative processing technology instead of heating. The objective of this study was to examine and compare the effect of PEF and High Temperature Short Time (HTST) treatments on the physicochemical, microbiological and sensory characteristics of citrus juices. Total sugar and titratable acidity values of fresh citrus juice and two treatments were not significantly different each other at p<0.05. The concentration of vitamin C in fresh citrus juice $(31.2{\pm}0.59\;mg%)$ was not significantly different with the value of PEF treatment $(29.4{\pm}0.75\;mg%)$ but was significantly higher than the value of HTST treatment $(27.4{\pm}0.75\;mg%)$. The color values (L, a, and b) in PEF treatment were significantly lower than the fresh citrus juice, but were higher than the values of HTST treatment. Both total bacterial cell counts $(6.65\;{\pm}\;0.08\;log_{10}(cfu/mL))$ and yeast counts $(7.79{\pm}0.07\;log_{10}(cfu/mL))$ in fresh citrus juice were significantly reduced by PEF $(1.39{\pm}0.14,\;2.42{\pm}0.1\;log_{10}(cfu/mL))$ as well as HTST treatment (0, 0). PE activity of fresh citrus juice $(1.3{\pm}0.12\;units/mL)$ was significantly reduced by PEF treatment $(0.11{\pm}0.01\;units/mL)$ and was totally inactivated by HTST treatment. Sensory evaluation scores in flavor, taste and overall acceptability between the fresh and PEF treated citrus juices $(7.2{\sim}7.5)$ were not significantly different but the values of HTST treatment $(5.1{\sim}5.8)$ were lower than others. Consequently, PEF treatment is thought to be a good alternative pasteurization method for fresh citrus juice to HTST treatment due to its strong pasteurization effect, reduced destruction of nutrients and good sensory characteristics.

• Journal of the Korean Society of Food Science and Nutrition
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• v.19 no.3
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• pp.195-200
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• 1990

Effects of cooking time(5-30 min in a pressure cooker) and HTST air dehydratiion time(0-9min at 15$0^{\circ}C$) on physical properties of dried green peas(3% oisture content wet basis) were investigated by determining rehydration ratio rehydration curve browning reaction and puncture force, The rehydration ratio and curve of dried green peas were increased with increa-sing cooking time and HTST air dehydration time. Preheating of the green peas for 30 min in a pressure cooker or for 9 min of HTST air dehydration time prior to 6$0^{\circ}C$ air dehydration recovered a 87.3% of original moisture content of raw green peas in a boiling water for 5 min. The brownin greaction was gradually decreased up to 15 min of cooking time. Puncture pressure of rehydrated green peas treated in a boiling water for 5 min was decreased as the cooking time and HTST air dehydration time were increased and was highly correlated with rehydration (r=-0.956) The effects of cooking time and HTST air dehydration time on rehydration ratio browning reaction and puncture pressure were significantly different at the a=0.01 level except effect of HTST air dehydration time on browning reaction.

• Korean Journal of Food Science and Technology
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• v.31 no.5
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• pp.1196-1202
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• 1999

This work was to determine the microbial and physico-chemical changes of HTST-pasteurized soymilk using microwave energy. Soymilk was HTST pasteurized$(at\;90^{\circ}C\;for\;20\;sec)$ by three methods: by heating in a stainless steel tube immersed in a hot water bath(MP0), by heating in a microwave cavity to a defiled temperature and then holding in a hot water bath(MP1), and by both heating and holding in a microwave cavity(MP2). The microbial quality based on the total plate count was in the order of MP0, MP2 and MP1. The three samples pasteurized by different methods showed the similar microbial quality with respect to the coliform count, psychrotrophic bacterial count and phosphatase activity. The destruction of trypsin inhibitor was in the order of MP0, MP1 and MP2. There were no significant differences in pH, titratable acidity, viscosity and vitamin $B_2$ content before and after pasteurization and among the different pasteurization methods. The similar or higher quality retention of the MP1 or MP2 supports the possibility of using microwave energy for the HTST pasteurization of soymilk and other fluid food products.

• Journal of Dairy Science and Biotechnology
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• v.16 no.2
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• pp.90-97
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• 1998

This study was carried out to investigate changes of microbiological and sensory properties in various heat-treated market milks (LTLT, HTST, and UHT milks) stored at 10$^{\circ}C$ during 15d. Titratable acidity (TA) increased with storage, while pH tended to decrease. During the initial 9d, no difference was found in TA, however, after 9d, it was slightly higher in HTST and UHT milks than that in LTLT milk. In LTLT and HTST milks, total viable cells and psychrotrophs were dramatically increased during storage, In addition coliform and pathogenic bacteria were found at 12 and 15d. In UHT milk, total viable cells were found only at 15d. In sensory evaluation, LTLT and HTST milks developed a negligible off-flavor until 9d. At 12d, it became stronger in HTST milk than that in LTLT milk. In UHT milk, off-flavor was detected at 9d and increased rapidly there-after. The degree of off-flavor was little higher in HTST and UHT milks, compared with that of LTLT milk after 9d storage. These observations indicated that LTLT and HTST milks may not be microbiologically acceptable after 5d, while off-flavor was not detectable until 9d, In comparison, UHT milk keeps a good quality in microorganism until 15d, however, it may not be accepted in sensory aspect after 9d storage.

• Korean Journal of Food Science and Technology
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• v.31 no.5
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• pp.1392-1396
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• 1999

This work was to apply the microwave energy to HTST pasteurization of milk in order to prevent undesirable quality changes due to the fouling and overheating on the surface of heat exchanger. A continuous tubulartype microwave pasteurization system was designed using a domestic microwave oven(800w and 2,450MHz). Raw milk was HTST pasteurized$(at\;72^{circ}C\;for\;15\;sec)$ by three methods; by heating in a stainless steel tube immersed in a hot water bath(MP0), by heating in a microwave cavity to a desired temperature and then holding in a hot water bath(MP1) and by both heating and holding in a microwave cavity(MP2). The microbial quality based on the total plate count and Psychotrophic bacterial count was in the order MP0, MP2 and MP1 ; however, the quality difference was not significant(p<0.05) when the initial microbial numbers were involved in the statistical analysis. In addition, the three samples pasteurized by different methods showed the similar microbial quality based on the coliform count and phosphatase activity. The similar microbial quality of the three samples supports the potential use of microwave energy for the pasteurization of milk and other fluid food products.

• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.4
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• pp.755-759
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• 1999

To evaluate the effect of sterilizing method on the quality of iron fortified market milk, HTST(high temperature, short time) or LTLT(low temperture, long time) method was adopted after addition of 100ppm ferrous sulfate, ferric citrate, ferric ammonium citrate, or ferrous lactate in market milk. Sterilized iron fortified market milk was stored at 4oC and then pH, lipid oxidation, color change, and sensory quality were observed. The range of pH change in iron fortified market milk sterilized by HTST or LTLT was 6.51~6.74. The order of pH was control>ferric ammonium citrate>ferrous lactate>ferrous sulfate>ferric citrate. Oxygen consumption of ferric ammonium citrate and ferric citrate was lower than ferrous lactate and ferrous sulfate. This trend was same in HTST and LTLT method, but generally oxygen consumption was lower in iron fortified market milk sterilized by LTLT method than by HTST. In total color change, ferrous lactate treatment was closer to control than other treatments. Also sensory characteristics of ferrous lactate treatment was showed better quality than other treatment. From these results, LTLT method was more suitable than HTST method for iron fortified market milk and ferrous lactate was comparably suitable among iron salts used in this study.

• Korean Journal of Food Science and Technology
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• v.31 no.6
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• pp.1518-1522
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• 1999

This work was to determine the quality changes of milk with respect to the chemical components when HTST pasteurized by microwave energy. Raw milk was HTST pasteurized $(at\;72^{\circ}C\;for\;15\;sec)$ by three methods; by heating in a stainless steel tube immersed in a hot water bath (MP0), by heating in a microwave cavity to a desired temperature and then holding in a hot water bath (MP1) and by both heating and holding in a microwave cavity (MP2). There were no significant differences in pH and titratable acidity before and after pasteurization and among the different pasteurization methods. MP1 or MP2 showed better retention or less destruction than MP0 with respect to vitamin A, vitamin $B_1$, ascorbic acid and lysine content. The higher retention of nutrients of the MP1 or MP2 supports the possibility of using microwave energy for the pasteurization of milk and other fluid food products.

• Journal of Food Hygiene and Safety
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• v.10 no.1
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• pp.19-22
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• 1995

Sensory characteristics of various milk samples-low-temperature long-time(LTLT) milk, high-temperature short-time (HTST) milk and ultra-high temperature (UHT) milk-were investigated using chemical analysis and sensory evaluation. The chemical composition was not much different among the milk samples. The results of evaluation of preference for color, flavor, taste and overall desirability of the milk samples by scoring and ranking tests indicated that significant difference on the sensory quality was recognized at 0.01 percent level. UHT milk samples (especially sample F and H) had better sensory acceptability than LTLT milk HTST milk samples.

• Journal of the Korean Society of Food Science and Nutrition
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• v.21 no.4
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• pp.390-397
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• 1992

This study was carried out to analyze the physicochemical properties of bovine milks, which were heated with LTLT, HTST, UHT pasteurization and UHT sterilization methods and to compare the heat intensity among the heating methods and samples. The mean HMF values per liter milk were measured as 0.66~1.62 $\mu$M (LTLT), 0.9~1.78$\mu$M (HTST), 3.53$\mu$M(UHT pasteurized) and 7.43~8.97$\mu$M (UHT sterilized) in samples, re- sportively. The available Iysine contents per 100ml milk showed 293.2 mg (Raw), 289.2~291.2 mg (LTLT), 298.4~292.4mg (HTST), 272.4~261.6mg (UHT pasteurized) and 279.0mg (UHT sterilized), respectively. The rates of whey protein denaturation were 9.5~11.4% (LTLT), 9.5~17.1% (HTST), 89.3~95% (UHT pas-tsterilized) and 62.7% (UHT sterilized), respectively. The contents of SH groups per g protein were determined as 2.86$\mu$M (Raw) and 2.95~3.15$\mu$M (LTLT), 3.08~3.18$\mu$M (HTST), 3.26~3.42$\mu$M (UHT Pasteurized) and 3. 36$\mu$M (UHT sterilized), respectively, The SS groups Contents per g protein were 28.93$\mu$M (Raw), 25.72~26. 51 $\mu$M (LTLT), 26.93~26.79$\mu$M (HTST), 23.65~23.04 $\mu$M (UHT pasteurized) and 24.69$\mu$M (UHT sterilized), respectively. The ascorbic acid contents per liter milk were measured 6.05mg (Raw), 1.47~1.65mg (LTLT), 2.50~3.85mg (HTST), 2.87~3.69mg (UHT pasteurized) and 4.50mg (UHT sterilized). The changes of some in-dices in milk samples depend on the heating temperature and time ; the HMF values, SH groups, whey protein denaturation rates increased, while the available lysine contents and SS groups decreased in LTLT, HTST, UHT pasteurized and UHT sterilized milks. No remarkable differences were found in heating indicators between LTLT and UHT milks.

• Bulletin of Food Technology
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• v.14 no.2
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• pp.116-121
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• 2001