• Korean Journal of Food Science and Technology
• /
• v.30 no.6
• /
• pp.1448-1455
• /
• 1998

Fermented milk was prepared from milk or mixture of milk and apple juice/grape juice, and it was freeze dried. pH change and growth of Lactobacillus acidophilus (KCTC 2182) during freeze drying were studied. The effects of freeze drying on sensory evaluation and volatile aroma compounds in freeze dried sample or reconstituted sample were also studied. Freezing and freeze drying did not affect pH of fermented milk. Number of viable cells of L. acidophilus was markedly reduced during freezing or freeze drying. When number of viable cells in original fermented milk was considered as 100%, survival ratio of viable cells after freezing was $64.5{\sim}85.2%$ and that after freeze drying was $10.0{\sim}21.1%$. When sensory properties of original fermented milk prepared from juice-milk (ratio 15:35) were compared with those of freeze dried/reconstituted sample, sensory properties of original sample were better than those of freeze dried/reconstituted sample. Ethanol, diacetyl, butanol and acetoin were detected in all of original samples and freeze dried/reconstituted samples while acetone was detected in samples containing high amount of grape juice. Volatile aroma compounds in original fermented milk were reduced during freeze drying. L. acidophilus produced ethanol, diacetyl and acetoin during fermentation.

• The Plant Pathology Journal
• /
• v.21 no.1
• /
• pp.7-12
• /
• 2005

Plant growth-promoting rhizobacteria (PGPR) are a wide range of root-colonizing bacteria with the capacity to enhance plant growth and control plant pathogens. Here we review recent progress that indicate some PGPR strains release a blend of volatile organic compounds (VOCs) that promote growth in Arabidopsis seedlings and induce resistance against Erwinia carotovora subsp. carotovora. In particular, the volatile components 2,3-butanediol and acetoin released exclusively from the PGPR strains triggered the greatest level of growth promotion and induced systemic resistance. Pharmacological applications of 2,3-butanediol promoted the plant growth and induced resistance, while bacterial mutants blocked in 2,3-butanediol and acetoin synthesis was devoid of growth-promotion and induced resistance capacities. The results suggested that the bacterial VOCs play a critical role in the plant growth promotion and induced resistance by PGPR. Using transgenic and mutant lines of Arabidopsis, we provide evidences that the signal pathway activated by volatiles from one PGPR strain is dependent on cyto-kinin activation for growth promotion and dependent on an ethylene-signaling pathway for induced pathogen resistance. This discovery provides new insight into the role of bacterial VOCs as initiators of both plant growth promotion and defense responses in plants.

• Journal of Microbiology and Biotechnology
• /
• v.27 no.1
• /
• pp.92-100
• /
• 2017

Acetoin (AC) is a volatile platform compound with various potential industrial applications. AC contains two stereoisomeric forms: (3S)-AC and (3R)-AC. Optically pure AC is an important potential intermediate and widely used as a precursor to synthesize novel optically active materials. In this study, chiral (3R)-AC production from meso-2,3-butanediol (meso-2,3-BD) was obtained using recombinant Escherichia coli cells co-expressing meso-2,3-butanediol dehydrogenase (meso-2,3-BDH), NADH oxidase (NOX), and hemoglobin protein (VHB) from Serratia sp. T241, Lactobacillus brevis, and Vitreoscilla, respectively. The new biocatalyst of E. coli/pET-mbdh-nox-vgb was developed and the bioconversion conditions were optimized. Under the optimal conditions, 86.74 g/l of (3R)-AC with the productivity of 3.61 g/l/h and the stereoisomeric purity of 97.89% was achieved from 93.73 g/l meso-2,3-BD using the whole-cell biocatalyst. The yield and productivity were new records for (3R)-AC production. The results exhibit the industrial potential for (3R)-AC production via whole-cell biocatalysis.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.41 no.8
• /
• pp.947-950
• /
• 1992

At-cut quartz crystal has been applied as chemical vapour sensors. The responses of quartz crystal at 9 MHz coated with phosphatidylglycerol(PG), phosphatidylinositol(PI), phosphatidylethanolamine(PE), phosphatidylserine(PS), and lipid A(LA) are determined for amyl acetate, acetoin, menthone and other organic gases which showed different affinities for each lipid. The identification of odorants depending on the species of lipid used for coating is discussed in terms of the normalized resonant frequency shift pattern.

• Food Science of Animal Resources
• /
• v.20 no.1
• /
• pp.64-71
• /
• 2000

The volatile flavour compounds such as acetaldehyde, acetone, ethanol, diacetyl and acetoin were detected by gas chromatography in adlay yoghurt during fermentation and storage period at 4 $pm$1$^{circ}C$, but acetoin was trace. The contents of acetaldehyde of adlay yoghurt showed maximum immediately after fermentation and decreased significantly(P<0.05) with storage period and were in order of adlay yoghurt fermented with YC-380, ABT-D and ABT-4. The contents of acetone were shown similar trend to acetaldehyde and those of adlay yoghurt fermented with YC-380, ABT-4 and ABT-D, decreased rapidly from 6 days, 9 days and 12 days of storage, respectively. The contents of ethanol increased during the storage period and those were significant differences(p<0.05) between 6 days and 9 days of storage period in control and treatments. The contents of diacetyl were detected in control and treatments at 9 days of storage and increased slightly during the storage period. The contents of volatile flavour compounds of T1 showed similar to that of control and slightly high compared to those of treatments, and decreased gradually with increasing the level of addition of adlay in treatments. The taste, flavour and texture of T1 immediately after fermentation and during the storage period at 4$\pm$1$^{\circ}C$ were slightly higher than those of control and treatments. The scores of sensory evaluation of treatments except T1 were lowered significantly(p<0.05) with increasing level of addition of adlay. Adlay yoghurt fermented with YC-380 and ABT-4 and ABT-D were superior to both of taste and flavour, and texture, respectively. From the results mentioned above, the addition of taste and flavour, and texture, respectively. From the results mentioned above, the addition of adlay at 1% (w/v) level in skim milk substrate were suitable for quality of adlay yoghurt such as volatile flavour compounds and sensory property.

• Korean Journal of Food Science and Technology
• /
• v.30 no.1
• /
• pp.184-191
• /
• 1998

Gel-type fermented milk was prepared from mixture of milk and apple juice or grape juice by fermentation with Lactobacillus acidophilus (KCTC 2182). Changes in volatile aroma compounds during 21 hr-lactic fermentation were studied. Diacetyl and acetoin, that were produced by L. acidophilus, were detected at 6 hr or 12 hr and showed peak values at 12 hr. Acetone and butanol, that were present originally in sample, decreased gradually during fermentation. Ethanol, that was either present originally in sample or produced by L. acidophilus, showed peak value at 18 hr in case of mixture of apple juice and milk. The concentration of ethanol was substantially high during whole period of fermentation in case of mixture of grape juice and milk though it showed peak value at 18 hr. Because the concentrations of ethanol in apple juice and ethanol and acetone in grape juice were relatively high, it might affect the results.

• Korean Journal of Food Science and Technology
• /
• v.27 no.4
• /
• pp.612-617
• /
• 1995

Changes in titratable acidity, pH, viable cells, sensory properties and volatile aroma compounds of yogurt during lactic fermentation in milk added with egg white powder (EWP) have been studied. Milk added with 1% or 2% (W/V) of EWP was fermented with Lactobacillus acidophilus for 30 hr. Acidity of milk added with EAT increased gradually during lactic fermentation for 30 hr, pH dropped gradually and number of viable cells increased and reached stationary phase at about 9 hr. Addition of EWP significantly stimulated acid production by lactic acid bacteria and stimulating effect of 2% EWP addition on acid production was slightly higher than that of 1% EWP addition. Sensory evaluation showed that optimum fermentation time of yogurt prepared from milk added with 2% of EWP was about 15 hr. Gas chromatographic analysis showed that the amount of acetone and butanol decreased gradually and that of ethanol increased until 30 hr. Diacetyl and acetoin were first detected after 6hr and 9hr, respectively, and then increased until 30 hr.

• Korean Journal of Food Science and Technology
• /
• v.27 no.4
• /
• pp.458-463
• /
• 1995

A curd yogurt was prepared from milk added with skim milk powder or egg white powder(EWP). The effects of EWP addition on growth and acid production by lactic acid bacteria in milk were studied. The effects of EWP addition on quality of curd yogurt in point of apparent viscosity, sensory property and volatile aroma compounds were also investigated. Addition of PAT markedly stimulated acid production by lactic acid bacteria and stimulating effect of EWP on acid production was proportional to the amount of addition. Apparent viscosity of curd yogurt added with EWP was generally higher than that of control. Curd yogurt fermented with L. acidophilus showed thixotropic characteristics. Sensory property of curd yogurt added with EWP was evaluated as better than reference sample and sample added with EWP at 2% level was evaluated as better than other samples. Acetone, ethanol, diacetyl, butanol and acetoin were detected by gas chromatographic analysis.

• Food Science of Animal Resources
• /
• v.33 no.5
• /
• pp.646-654
• /
• 2013

In this study, quantitative analysis of major volatile flavor compounds from yogurt was conducted using headspace-solid phase microextraction (HS-SPME) GC-FID analysis technique, and the changes of volatile aroma compounds during the storage period were evaluated. The yogurt was prepared with the addition of 2% cereals, such as, white rice (WR), brown rice (BR), germinated brown rice (GBR) and saccharified germinated brown rice (SGBR). After fermentation, the products were stored at $5^{\circ}C$for 15 d. The major volatile aroma compounds in yogurt, such as acetaldehyde, acetone, diacetyl and acetoin were able to be extracted using HS-SPME technique efficiently. The regression ($r^2$) value of standard curve prepared with various concentrations of individual flavor chemicals was analyzed over 0.9975, and reproducibility was acceptable to apply quantitative analysis. The analysis of volatile components of control sample during storage showed that the acetaldehyde on 0 d was 10.83 ppm, and that contents were increased to 15.67 ppm after 15 d of storage. However, addition of BR, GBR and SGBR decreased the acetaldehyde contents during storage periods. The acetone content of all treatments during storage was not significantly different. The diacetyl content of all treatments were increased during storage and the addition of SGBR showed the highest amount of diacetyl (0.84 ppm) among treatments on 15 d of storage. The acetoin content of yogurt added with grains was higher than that of control during storage. As a result, the content of volatile aroma compounds in yoghurt during storage period could be analyzed HS-SPME extraction technique effectively, and HS-SPME/GC analysis can be considered for quality control of fermented milk products.

• Proceedings of the KOSOMBE Conference
• /
• v.1991 no.05
• /
• pp.98-100
• /
• 1991

A sensitive surface acoustic wave (SAW) sensor for the detection of odorants has been constructed by depositing different phospholipids and fatty acids on the surface of the SAW device wi th the Langmuir-Blodgett technique. The characteristics of SAW device operating at 310 MHz deposited with phosphatidylcholine were analyzed. Amyl acetate, acetoin, menthone and other organic gases showed different affinities. The identification of odorants depending on the species of lipid used for coating is discussed in terms of the similarity of the normalized resonant frequency shift pattern. Using a number of different lipid-coated SAW devices, odorants could be identified by a neural-network pattern recognition with back-propagation algorithm.