• Food Science and Preservation
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• v.20 no.5
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• pp.720-726
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• 2013

This study was carried out to optimize the filtration, clarification, anti-browning processing conditions of clear pear juice and to investigate changes in antioxidant activity of pear juice produced through different heating treatment. For the filtration with cheese cloth, filter paper, or centrifugation (10 min at 3,000 rpm), the pear juice was most efficiently filtered with centrifugation because it showed the highest lightness (L value) and lowest yellowness (a value). Among various clarifying agents, 1% of gelatin or bentonite clarified effectively pear juice but tannin or egg albumin did not. Among anti-browning agents (0.1%) like L-ascorbic acid, NaCl or citric acid, L-ascorbic acid prevented the browning of pear juice with the lowest browning index value (2.62), compared to that of NaCl (2.74), or citric acid (2.87). Fructose, sucrose, glucose and sorbitol were present in the pear juice, the fructose and glucose contents increased but that of sucrose decreased in the heated pear juice. The total polyphenol content of the heated pear juice significantly increase, and did the total flavonoid contents in the clear and heated pear juice. The DPPH radical scavenging activity and nitrate scavenging activity were higher in the clear and heated pear juice than in the fruit crush.

• Korean Journal of Food Science and Technology
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• v.30 no.4
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• pp.827-831
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• 1998

Effects of pre-pressing condition on quality of pear juice were investigated. Three different types of pressed pear juices such as heated-and-pressed pear juice (HPP), blanched-and-pressed pear juice (BPP), and thawed-and-pressed pear juice (TPP) were prepared. The yield and content of soluble solids in HPP were 78% and $15.0^{\circ}Bx$ which were higher than the other treatments, respectively. Acidity and pH of all the samples were about 0.2% and 4.9, respectively. Major free sugars and organic acids in HPP, BPP, and TPP were fructose and malic acid, respectively. Major soluble minerals were K, P and Mg, and miner ones were Na and Fe. HPP showed a lowest L value, but had a highest taste.

• The Korean Journal of Food And Nutrition
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• v.31 no.6
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• pp.890-896
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• 2018

The aim of this study was to determine volatile flavor compounds in Shingo pear juice. Volatile flavor compounds were analyzed using solid-phase micro-extraction (SPME) - gas chromatography-mass spectrometry (GC-MS). The effect of inorganic salts solution on the extraction ability of the SPME fiber was treated by adding saturated $CaCl_2$ solution at the ratio of 1:20 (v/v) after 0, 60, 120 min of preparing pear juice, respectively. As a result, a total of 22 volatile compounds were identified in Shingo pear juice. Ethyl acetate was found to be the most abundant volatile compound ($13.36{\sim}19.61{\mu}g/kg$), followed in order by hexanal, ethyl hexanoate, ethyl 3-(methylthio)-2-propenoate, ethyl octanoate and 2-hexenal. Total contents of volatile flavor compounds were $31.07{\mu}g/kg$ (control), $40.93{\mu}g/kg$ (0 min), $27.62{\mu}g/kg$ (60 min) and $26.32{\mu}g/kg$ (120 min). This result indicated that the addition of saline solutions could inhibit the enzymatic reaction of volatile flavor compounds effectively when treated as soon as juice preparation.

• Preventive Nutrition and Food Science
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• v.5 no.1
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• pp.32-36
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• 2000

Prickly pear juice(PPJ) extracted from prickly pear fruit (Opuntia ficus-indica)was used as raw material for the production of alcoholic beverages. Prickly pear juice (PPJ) had 0.88 oBrix of soluble solid, pH 3.96 and 0.14% of total acidity. Alcohol fermentation of 25% PPJ including 22 oBrix of sugar and 1$\times$106 of inoculum was suitable for alcohol fermentation indicating the rapid decrease of sugar content. The 22 oBrix of sugar in PPJ (25%)GJ (50%) mixture was changed to 6.5 oBrix after fermentation at 3$0^{\circ}C$ for 7 days. The alcohol content was 9.2% (w/v). PPJ (70%)/GJ (30%) mixture produced alcoholic beverage with 6.9% alcohol content resulting in the gradual decrease of soluble for 7 days. On the other hand, PPJ (50%)/GJ(50%) mixture carried out completely the alcohol fermentation at 22$^{\circ}C$ for 6 days and enhanced the red color of alcoholic beverages.

• Journal of the Korean Society of Food Science and Nutrition
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• v.21 no.4
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• pp.377-380
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• 1992

To produce economically important acid with pear juice, an acetic acid bacterium was selected from many isolated acetic acid bacteria. The alcohoic fermentation was conducted by inoculating pear juice with Saccharomyces cerevisiae ATCC 4124, and then the pear vinegar was prepared by batch cultivation in flaskes with the isolated Acetobacter sp. The optimum conditions for high yield of acetic acid were studied experimentally in the batch shake flask . For seed purposes the Acetobactor sp. was cultivated for 2 -days and transferred to the acid production medium . Optimum alcohol concentration, initial acidity and temperature for the acid production were 8.0% , 2.0% and 28$^{\circ}C$, respectively. Under the same conditions, the addition of yeast extract (1%) was observed to produce relatively high yield of acetic acid.

• Food Science and Preservation
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• v.18 no.5
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• pp.692-699
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• 2011

This study was conducted to investigate the physicochemical characteristics of yanggaeng prepared with pear juice and dried pear powder. The proximate composition and total polyphenol content, antioxidant activities, Hunter's color values, texture, sensory properties of pear yanggaeng variants [pear juice (PJ), pear juice and hot-air-dried pear powder (PJH), pear juice and freeze-dried pear powder (PJF) yanggaeng] were examined. The moisture content was highest (27.9%) in the control (C) yanggaeng, but the latter's energy and carbohydrate content were lower than in the pear yanggaeng variants. The differences between the pear yanggaeng variants were not significant.The total polyphenol content was highest in the 20.7 mg/100g PJF yanggaeng. The antioxidant activities of PJF yanggaeng were higher than those of the other pear yanggaeng varients. The Hunter color value results showed that the lightness (L) values were highest in C yanggaeng whereas the redness(a) and yellowness(b) values were highest in PJH yanggaeng. The springiness in texture was lowest in C yanggaeng and not significant in the others. The hardness and chewiness were highest in PJH and PJF yanggaeng, but adhesiveness was lowest therein. The results of the sensory test showed that PJF yanggaeng was the highest in flavor, color, taste, hardness, chewiness, and overal quality. Based on these results, it can be concluded that pear juice and freeze-dried pear powder yanggaeng has excellent physicochemical and antioxidant activities.

• Culinary science and hospitality research
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• v.12 no.4 s.31
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• pp.299-319
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• 2006

The purpose of this study was to investigate the changes of hardness and microstructure of Dongchimi cooked with various sources of sugar(xylitol, xylose, sugar, pear juice). It was fermented at $10^{\circ}C$ for 60 days. The changes of pH in Dongchimi used different kinds of sugar decreased in all samples during the fermentation period, and then showed a slow decrease after 12 days of fermentation. The total acidity of Dongchimi using xylitol arrived slowly at the best tasting condition($0.3\sim0.4$ point) compared with other conditions. The changes of salt content were showed high as compared with other test conditions in 0 day, the day of fermentation. At the early stage of fermentation, the changes of turbidity of Dongchimi using sugar, pear juice were showed high as compared with those of Dongchimi using xylitol, xylose for $5\sim15$ days of fermentation. The maximum cutting force of Chinese radish Dongchimi showed the highest value among al at the 25 th day of ripening and then decreased gradually. The maximum cutting force of Dongchimi using sugar showed the lowest. The calcium and magnesium contents of Dongchimi juice and Chinese radish Dongchimi juice using xylitol were observed high at the early stage of fermentation and showed the highest value during the fermentation period. The microstructure showed disintegration appearance of middle lamella and cell wall during the fermentation period.

• Korean journal of food and cookery science
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• v.11 no.2
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• pp.113-118
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• 1995

A preferable mixing ratio of a six-vegetable juice was suggested in this study. The vegetables used for preparation of mixed vegetable juice were carrot(Ct), cabbage(Cg), pear(Pr), cucumber(Cr), celery (Cy) and dongchimi(Di). The characteristics of pH, titratible acidity, reducing sugar, turbidity, solids, color and acceptability were compared to determine the mixing ratio. The vegetables showed a wide ranHe of pH of 3.70-6.01, acidity of 28.92 uv~74.40 nd and reducing sugar of 1.20ft~ 12.69fo. Celery juice showed the higest suspension stability and "b" value and the lowest values in Hunter "L" and "a" values among the 6 vegetable juice. The preferable mixing ratio of two-vegetable juice selected were Ct-Di(1 : 4), Cg-Pr(1 : 3) and Cr-Cy(3 : 1). From the various ratio of the three of biary mixtures of Cg-Pr(1 : 3): Ct-Di(1 : 4): Cr-Sy(3 : 1), two ratio of 5.0 : 2.5 2.5(V-6A) and 6.0 : 2.0 : 2.0(V-6B) were suggested as the most prefered six-vegetable juice. Pear, dongchimi and cucumber were found to be influential on the preference. The pH and titratible acidity of the two juices with different ratios were in the range of 4.92~4.98 and 36.g∼37.4 ml, respectively.

• Preventive Nutrition and Food Science
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• v.19 no.2
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• pp.108-114
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• 2014

Four Korean kernel fruit (apple, pear, persimmon, and mandarin orange) juices were obtained by household processing techniques (i.e., blending, juicing). Whole and flesh fractions of each fruit were extracted by a blender or a juicer and then examined for phytochemical content (i.e., organic acids, polyphenol compounds). The antioxidant capacity of each juice was determined by ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Results revealed that juices that had been prepared by blending whole fruits had stronger antioxidant activities and contained larger amounts of phenolic compounds than juices that had been prepared by juicing the flesh fraction of the fruit. However, the concentration of ascorbic acid in apple, pear, and mandarin orange juices was significantly (P<0.05) higher in juice that had been processed by juicing, rather than blending. The juices with the highest ascorbic acid (233.9 mg/serving), total polyphenols (862.3 mg gallic acid equivalents/serving), and flavonoids (295.1 mg quercetin equivalents/serving) concentrations were blended persimmon juice, blended mandarin orange juice, and juiced apple juice, respectively. These results indicate that juice extraction techniques significantly (P<0.05) influences the phytochemical levels and antioxidant capacity of fruit juices.

• Korean Journal of Food Science and Technology
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• v.27 no.6
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• pp.845-851
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• 1995

To improve the utilization of pear in its processing, the cloudy and clear juice concentrates were prepared and their rheological properties were investigated in the range of temperatures($5{\sim}60^{\circ}C$) and concentrations($15{\sim}60^{\circ}Brix$). Pear juice concentrates showed flow behavior close to Newtonian fluids. Their flow behavior was also explained by applying Power law model and Herschel-Bulkley model. Flow behavior index did not have good correlation with concentration, but decreased with the increase of temperature, showing pseudoplastic properties. Consistency index increased with the increase of concentration and with the decrease of temperature. The effect of temperature and concentration on the apparent viscosity at 1500 1/s shear rate was examined by applying Arrhenius equation. The activation energy for flow of the cloudy and clear pear juice concentrates increased from $1.5140{\times}10^4\;to\;3.4141{\times}10^4\;J/kg{\cdot}mol$, and from $1.4762{\times}10^4\;to\;3.4963{\times}10^4\;J/kg{\cdot}mol$ with the increase of concentration, respectively. The influence of temperature on the apparent viscosity was more pronounced at higher concentration. And the concentration-dependent constant A decreased from $0.0789\;to\;0.0484^{\circ}Brix^{-1}$, and from $0.0786\;to\;0.0476^{\circ}Brix^1$ with the increase of temperature, respectively.