• Korean Journal of Food Science and Technology
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• v.32 no.5
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• pp.979-984
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• 2000

To improve the quality of dehydrated onion, antibrowning agents were screened. Effects of antibrowning agents on the degree of browning and the quality characteristics in dried onions were investigated. Sliced onions were dehydrated in an air drier at $70^{\circ}C$ within 3 percent moisture. Among various antibrowning agents, cyclodextrin and corn starch treatments were selected. Dipping in 4%(w/v) corn starch suspension proved more effective in preventing browning than other treatments. The change of color and the degree of browning showed a correlation. Dried onions treated with antibrowning agents prevented browning at around $24{\sim}32%$ compared to control. The contents of reducing sugar and vitamin C in treated onions had minimally changes.

• Food Science and Preservation
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• v.20 no.6
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• pp.894-898
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• 2013

This study was performed to provide the basic data for the prediction of the usefulness of onion with cold tolerance cultivated in Kangwon. The physicochemical properties and antioxidant activity of freeze-dried and hot-air-dried (40 and $60^{\circ}C$) onions were investigated. The moisture content of the raw onion was 90.55%. The crude protein and crude fat contents of the freeze-dried onions were slightly higher than those of the hot-air-dried onions ($40^{\circ}C$ and $60^{\circ}C$). As for the color values, the freeze-dried onion powder was highest in lightness (77.19), and the $60^{\circ}C$ hot air-dried onion was highest in redness (6.09) and yellowness (24.60). Moreover, the color difference (${\Delta}E$) between the freeze-dried and hot-air-dried ($40^{\circ}C$ and $60^{\circ}C$) onion powders was significant. The brown index was lower in the freeze-dried onion than in both hot-air-dried onions. The total phenol content and the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging activity of both hot-air-dried onions were higher than those of the freeze-dried onion. These results indicate that the freeze-drying methods protected the physicochemical properties of the onion powder, whereas the hot-air-drying method enhanced the antioxidant activity and the total phenol content of the onion powder.

• Journal of the Korean Society of Food Culture
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• v.30 no.1
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• pp.86-96
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• 2015

Onions contain antioxidant flavonoids and bioactive sulfur compounds. These substances are more abundant in the peel than in onion flesh. For this reason, whole onions including peels were added to soy milk to produce soy milk with whole onions (SWO), whereas peeled onions were added to soy milk to produce soy milk with peeled onions (SPO). The functional and antioxidant properties of these two kinds of soy milk were then analyzed and compared. Compared to control soy milk (CS) without onion powder, treated samples (to which freeze dried onion powder was added at 1.4, 1.6, 1.8, and 2.0%, respectively) showed significantly increased amounts of quercetin, isoflavone, and total phenol (p=0.05). The magnitude of the increase rose as the amount of added onion powder increased and when onion powder contained onion peels. With regards to antioxidant activity (DPPH and ABTS), SWO showed a greater value than SPO. The sensory evaluation scores of SWO and SPO were lower than CS for roughness and swallowing, as adding onion powder increased solid contents and viscosities. However, higher overall acceptability were obtained 1.8SPO and 1.8SWO.

• Korean Journal of Food Science and Technology
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• v.22 no.5
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• pp.539-542
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• 1990

The effects of immersion temperature $(20,\;40\;and\;60^{\circ}C)$ and immersion times (6. 12 and 18 min) in a distilled water prior to air dehydration upon the browning reaction and pyruvic acid content of air dried onions to a 4.071 moisture content (wet basis) were analyzed by a response surface methodology (RSM). Those values were also predicted by using a second degree polynomial regression model. Immersion temperature had more influence to browning reaction and pyruvic acid content than immersion time in these experimental ranges. The processing conditions to minimize the browning reaction of dried onions at $50^{\circ}C$ of air temperature (O.D.=0.071) were $60^{\circ}C$ of immersion temperature and 18 min of immersion time compared to control (O.D.=0.168) of air dehydration at $50^{\circ}C$ Pyruvic acid contents of dried onions at $50^{\circ}C$ of air temperature were maximized $(39.85{\mu}mole/g\;onion\;solid)$ at $60^{\circ}C$ of immersion temperature and 12 min of immersion time compared to control $(24.08{\mu}mole/g\;onion\;solid)$ of air dehydration at $50^{\circ}C$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.2
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• pp.230-235
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• 2005

Volatile organic components from fresh and freeze-dried onions were extracted by SDE apparatus and analyzed by GC/MS. Components of 40 and 31 were identified in fresh and freeze-dried onions respectively. These components included esters, aldehydes, ketones, alcohols and S-containing compounds. Major compounds of S-containing compounds such as 1-propanethiol, dipropyl trisulfide, and methyl propyl trisulfide in fresh onions were clearly decreased in freeze-dried onions. Then, S-containing compounds such as methyl allyl sulfide, propyl ally sulfide, dially disulfide and 3,5-diethyl-l,2,4-trithiolane and alcohols such as pentanol, hexanol and propanol were disappeared by freeze-drying. Exceptionally, ethyl acetate, dimethyl disulfide and 2-methyl-2-pentenal were increased as different trend with major S-containing compounds. (Z)-Propenyl methyl disulfide and (E)-propenyl methyl disulfide were also changed by freeze-drying in the similar pattern as mentioned above compounds.

• Food Science and Preservation
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• v.13 no.6
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• pp.762-768
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• 2006

To assess utilization of onions extract as natural food additives, ethyl acetate, ethanol and hot water extract of freeze dried onions (red, white and yellow) were exmined for their chemical component and nitrite scavenging activity. Contents of total organic acid and total free sugar were in the range of $135.4{\sim}1,2557mg%$ and $51.7{\sim}62.9%$ as dry matter bases, respectively, and then their content of three onions were higher in ethylacetate and hor water extracts than in ethanol extract. Contents of total phenol and total flavonoids were in the range of $9.3{\sim}$13.3 % and $159.8{\sim}584.1mg%$ as dry matter bases, respectively, and their content of red onion extract by three solvent were higher than those of other onion extract. Nitrite-scavenging activities (NSA) of onion extracts were increased by lowering pH and elevating onion concentrations, and their values of ethanol and hot water were about 55% in addition of 10 mg/mL of red onion extract showing that NSA of red onion was twice higher than that of the other onions. In conclusion, the result indicated that red onion extract was very effective to inhibit nitrosamine formation at low pH condition as natural nitrite scavenging agent.

• Korean Journal of Food Science and Technology
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• v.32 no.3
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• pp.578-583
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• 2000

To use onion pomace produced from concentrated onion juice processing, dried onion pomace or dried onions were mixed with com grits at levels of 10, 20, and 30% and were extruded in a twin-screw extruder. Quality properties of extruded onion snack were investigated. Low-lignin dietary fiber of dried onion pomace was approximately 2 times higher than that of dried onion. Browning increased with increasing onion content. Reducing sugar and free sugar in onion snack showed high content by increasing onion concentration and the majority of free sugar consisted of glucose and fructose. Flavonoid in control snack was not detected and the flavonoid content containing quercetin and quercetin glycosides was about 50% less in onion pomace snack than in onion snack. Sensory evaluation of onion snack containing 10% concentration of dried onion pomace or dried onion indicated the products were acceptable in overall eating-quality.

• Journal of Life Science
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• v.18 no.9
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• pp.1271-1277
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• 2008

We investigated to determine the inhibitory effects of solvent extracts from dried onion on growth of cancer cell lines (HT-1080 human fibrosarcoma and HT-29 human colon cancer cells) and $H_{2}O_{2}$-induced oxidative stress. Two different drying methods, low temperature vacuum dryer and freeze dryer, were employed to dry onion. Inhibitory effects of acetone with methylene chloride (A+M) and methanol (MeOH) extracts from onion by two drying methods on the growth of HT-1080 and HT-29 cancer cells increased in a dose dependent manner (p<0.05) and the higher inhibitory effect was shown in onion extracts dried by low temperature vacuum dryer. The treatments of hexane, 85% aq. methanol, butanol and water fractions significantly inhibited the growth of both cancer cells (p<0.05) and onion fractions dried by freeze dryer showed a higher inhibitory effect compared with those dried by low temperature vacuum dryer. In order to determine a protective effect on H2O2-induced oxidative stress, DCHF-DA (dichlorodihydrofluorescin diacetate) assay was conducted. All fractions including crude extracts of dried onion appeared to significantly reduce the levels of intracellular reactive oxygen species (ROS) (p<0.05). Higher antioxidant effect was observed in onions dried by the low temperature vacuum dryer method. These results indicate that the low temperature vacuum dryer is useful to dry and produce onion powder.

• Food Science and Preservation
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• v.21 no.6
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• pp.838-843
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• 2014

In this study, near-infrared spectroscopy was used to observe the drying non-uniformity of vegetables such as spring onions, onions, and garlic, which are commonly used for seasoning. For the warm-air convection drying method, the vegetables showed drying non-uniformity, which is due to the unevenness of the wind temperature and humidity depending on the height and position of the drying tray. The second derivative spectra between the vegetable samples with different drying degrees were compared. The peak at around 1,390~1,400 nm, which is assigned to weak hydrogen bonds of water, was changed during drying whereas the peak near 1,420 nm, which represents strong hydrogen (H-) bonds of water, was not changed, indicating that water with weak H-bonds evaporates first during drying, and that water with strong H-bonds remains after drying. The hyperspectral NIR imaging technique combined with principal-component analysis made it possible to discriminate the dried vegetables according to their drying degree.

• Food Science and Preservation
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• v.13 no.1
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• pp.50-54
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• 2006

The identification characteristics of inadiated dried onion and garlic at 1, 4 and 7 kGy were investigated by analyzing their photostimulated luminescence (PSL), thermoluminescence (TL) and electron spin resonance (ESR). The PSL results showed that the photon counts of non-irradiated dried onion were less than 700 (negative) and those of irradiated samples at 1kGy or more were over 5000 (positive), making it possible to discriminate non-irradiated onions from irradiated ones. However, the intermediate counts (700-5000) were observed in irradiated garlic at 1 and 4 kGy, even though positive counts were measured in 7 kGy group. Radiation-induced TL glow curves $(TL_1)$ were measured at $150^{\circ}C$ range in both irradiated onion and garlic samples at 1 kGy or more, which could identify irradiated groups. Furthermore, determination of TL ratios $(TL_1/TL_2)$ for both samples could verify the above results. It was found, however, that ESR spectroscopy was not suitable for the detection of irradiated dried onion and garlic.