• 한국식품과학회지
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• 제47권4호
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• pp.431-437
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• 2015

In this study, high-acidity cider vinegar (HACV) was produced by alcoholic and acetic acid fermentation of apple concentrate without any nutrients and then the optimum alcohol concentration was determined through a qualitative study. HACV was fermented with different initial alcohol concentrations (6-9%) during the process of acetic acid fermentation. The highest content of reducing sugar, organic acids, and free amino acids was observed at 6% of initial alcohol concentration. Approximately 20 types of volatile compounds were identified by solid-phase microextraction (SPME) and GC-MS. The total volatile content was the highest at 6% of initial alcohol concentration, and the acid content was the lowest at 9% of the initial alcohol concentration. The HACV produced by a two-stage fermentation process was qualitatively better than commercial HACV presenting the highest value at 6% of initial alcohol concentration. Malic acid, aspartic acid, and hexyl acetate were selected as quality index components of HACV production by two-stage fermentation on the basis of correlation between their physicochemical properties and the sensory attributes of HACV.

• 한국식품영양학회지
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• 제37권4호
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• pp.189-196
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• 2024

To develop farm-made high effective vinegar, this study prepared apple vinegar using four kinds of acetic acid bacteria isolated from a natural fermentation liquid of 'Cheongsoo' grapes and analyzed vinegar samples fermented 93% apple juice and 7% alcohols at 30℃ for 20 days. To accomplish this, quality characteristics such as pH, total acidity, reducing sugar, organic acid, color, total polyphenol contents, and antioxidant activity contents were determined. The pH decreased while total acidity of all samples gradually increased during fermentation period. The vinegar with AP 21 strain tended to increase the total acidity quicker than other stains. Reduced sugar content remained high until the last fermentation day. Furthermore, reduced sugar contents of all vinegars increased as fermentation progressed by decomposing sucrose present in apples. When physiological activities were compared, apple vinegars fermented with AP 21 and 30 strains had higher total polyphenol and flavonoid contents than other samples. However, there was no significant difference in antioxidant activity between samples. These results indicate that strain 21 is the most suitable starter as acetic acid bacteria for producing farm-made vinegar.

• 한국토양비료학회지
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• 제33권5호
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• pp.356-360
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• 2000

우리나라 강우의 pH 분포와 산성도 중화에 미치는 $NH_4{^+}$ 및 $Ca^{2+}$ 영향을 평가하기 위하여 1993, 1994, 1995, 1997 및 1998년 각각 5월부터 10월까지 6개월 동안 안성지역에 내린 강우의 주요 이온들의 함량을 조사한 결과, 강우의 산성도 분포는 pH 5.0~5.6의 범위가 가장 많았으며 pH 5.6 이상의 강우는 연차적으로 점차 감소하는 경향이었다. 빗물중 $SO_4{^2-}$와 $NO_3{^-}$의 당량비는 1994년 이후 점차 증가하여 빗물중에 함유된 음이온중 $SO_4{^2-}$가 차지하는 비중이 점차 높아졌다. $[H^+]+[NH_4{^+}]+[Ca^{2+}]$의 역대수 값으로 계산되는 이론적 산성도는 측정된 pH값에 비해 5.0~12.6배 높았고 대기중에 존재하는 알카리 물질들에 의한 빗물의 월별 중화력은 강우량이 많은 7월과 8월에 가장 적었다. 또한 빗물의 산성도 중화에는 $NH_4{^+}$가 $Ca^{2+}$ 보다 기여도가 컸으며, 두 이온에 의한 빗물의 중화는 점차 감소하는 경향을 나타냈다.

• 공업화학
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• 제26권3호
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• pp.366-371
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• 2015

루이스 산도가 다른 두 종류의 클로로알루미네이트계 이온성 액체(IL) 촉매를 사용하여 tetrahydrotricyclopentadiene (THTCPD) 이성화 반응 거동에 관하여 연구하였다. 루이스 산도가 낮은 1-butyl-3-methylimidazolun chloride $(BMIC)/AlCl_3$와 높은 pyridine hydrochloride $(PHC)/AlCl_3$계 IL 촉매를 이용하고 온도와 시간을 반응 인자로 하여 THTCPD의 이성화 반응 경로를 고찰하였다. IL 촉매의 루이스 산도 증가에 따라 THTCPD 이성화 전환율을 증가시킬 수 있었다. 반응온도 및 IL 촉매의 산도에 따라 THTCPD 이성화 반응경로가 바뀌었다. 산도가 낮은 $BMIC/AlCl_3$ IL 촉매의 경우에는 기존에 사용되어오던 $AlCl_3$ 촉매와 유사한 반응 경로를 보이지만, 반응온도가 높아짐에 따라 endo, exo, endo-(norbornene; NB) ${\rightarrow}$ exo, exo, endo-NB ${\rightarrow}$ diamondoid로의 골격 재배열화 반응이 일어났다. 하지만, 산도가 높은 $PHC/AlCl_3$ IL 촉매의 경우에는 $TEAC/AlCl_3$ IL 촉매와는 다른 새로운 두 가지 경로(endo, exo, endo-NB ${\rightarrow}$ exo, exo, endo- NB ${\rightarrow}$ exo, exo, exo-NB 및 endo, exo, endo-NB ${\rightarrow}$ exo, exo, endo-NB ${\rightarrow}$ exo, exo, exo-(cyclopentadiene; CP))가 추가로 관찰되었다.

• Bulletin of the Korean Chemical Society
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• 제24권12호
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• pp.1785-1792
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• 2003

Zirconia modified with $MoO_3$ was prepared by impregnation of powdered $Zr(OH)_4$ with ammonium heptamolybdate aqueous solution followed by calcining in air at high temperature. Spectroscopic studies on prepared catalysts were performed by using FTIR, Raman, XRD, and DSC and by measuring surface area. Upon the addition of molybdenum oxide to zirconia up to 15 wt%, the specific surface area increased in proportion to the molybdate oxide content, while acidity measured by irreversible chemisorption of ammonia exhibited a maximum value at 3 wt% of $MoO_3$. Since the $ZrO_2$ stabilizes the molybdenum oxide species, for the samples equal to or less than 30 wt%, molybdenum oxide was well dispersed on the surface of zirconia and no phase of crystalline $MoO_3$ was observed at any calcination temperature above $400^{\circ}C$. The catalytic activities for cumene dealkylation were roughly correlated with the acidity of catalysts measured by ammonia chemisorption method, while the catalytic activities for 2-propanol dehydration were not correlated with the acidity because weak acid sites are necessary for the reaction.

• Preventive Nutrition and Food Science
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• 제21권3호
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• pp.255-262
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• 2016

The objective of this study was to determine the effects of different growing regions on quality characteristics, total bioactive compound contents, and in vitro antioxidant activity in aronia. Aronia grown in 3 different regions (Sangjoo, Ulju, and Youngcheon) in Korea was obtained and used fresh or as a freeze-dried powder. No statistically significant differences were observed for moisture, ash, crude lipid, and crude protein contents in aronia sampled from the 3 different regions. Aronia grown in Sangjoo had the highest total acid content and the lowest sugar content and pH value. Conversely, aronia grown in Youngcheon possessed the lowest total acid content and the highest sugar content and pH value. Aronia grown in Sangjoo possessed relatively high levels of polyphenols, flavonoids, and anthocyanins, as well as high antioxidant activity in comparison with aronia produced in other regions. Aronia grown in Youngcheon scored the highest for taste and overall acceptability in sensory evaluations, which may be related to the high sugar content and pH, and the low total acidity of the fruits. It is possible that higher sugar contents and pH, and lower total acidity in the aronia grown in Youngcheon result in more preferable sensory characteristics. However, they also contain relatively low levels of total polyphenols, flavonoids, and anthocyanins, and have low antioxidant activity as measured by 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging assays.

• Bulletin of the Korean Chemical Society
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• 제24권8호
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• pp.1141-1149
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• 2003

The structures and gas-phase ionization energies (ΔG°) of Meldrum's acid (I) and related cyclic (II-VI) and acyclic compounds (VII-IX) are investigated theoretically at the MP2/6-31+$G^*$, B3LYP/6-31+$G^*$, B3LYP/6- 311+$G^{**}$, B3LYP/6-311++G(3df,2p) and G3(+)(MP2) levels. Conformations of three neutral cyclic series vary gradually from boat (Meldrum's acid, I), to twisted chair (II) and to chair (III) as the methylene group is substituted for the ether oxygen successively. The preferred boat form of I can be ascribed to the two strong $n_O$ → σ* c-c antiperiplanar vicinal charge transfer interactions and electrostatic attraction between negatively charged C¹ and positively charged C⁴at the opposite end of the boat. All the deprotonated anionic forms have half-chair forms due to the two strong $n_C$ → π* c=0 vicinal charge transfer interactions. The dipole-dipole interaction theory cannot account for the higher acidity of Meldrum's acid (I) than dimedone (III). The origin of the anomalously high acidity of I is the strong increase in the vicinal charge transfer ($n_C$ → π* c=0) and 1,4-attrative electrostatic interactions (C¹↔C⁴) in the ionization (I → $I^-$ + $H^+$). In the acyclic series (VII-IX) the positively charged end atom, C⁴, is absent and the attractive electrostatic stabilization (C¹↔C⁴) is missing in the anionic form so that the acidities are much less than the corresponding cyclic series.

• 치위생과학회지
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• 제19권1호
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• pp.1-8
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• 2019

Background: Erosion is a gradual process that occurs fairly quickly, and the full extent of the erosive effects of acidic beverages is not yet clear. The present study aimed to determine the differences in the erosive potentials among four naturally acidic fruit nectars within the same range of titratable acidity and to determine the influence of the components of organic acids on tooth erosion. Methods: Diluted fruit nectars (mandarin 1:1.1, orange 1:1.7, lemon 1:15, grapefruit 1:20) with the same range of titratable acidity (7.9 ml) and their corresponding organic acids (0.05%, 0.1%, 0.3%, and 0.5% citric acid, malic acid, and a citric and malic acid mixture [pH 2.8], respectively) were used. Specimens were placed in conical tubes with 50 ml of each of the test solutions for 1 hour. A microhardness test and scanning electron microscopy were used to measure enamel erosion. Acid separation was carried out using high-performance liquid chromatography to analyze the composition of each test solution. Results: Similar decreases in the Vickers hardness number (VHN) were observed among the groups treated with the following diluted fruit nectars: diluted mandarin nectar ($75.9{\Delta}VHN$), diluted lemon nectar ($89.1{\Delta}VHN$), diluted grapefruit nectar ($91.7{\Delta}VHN$), and diluted orange nectar ($92.5{\Delta}VHN$). No statistically significant differences were found in the enamel surface hardness after erosion (p>0.05). Citric and malic acids were the major organic acids in the test fruits. The lemon and orange groups had the highest malic acid concentrations, and the mandarin group had the lowest malic acid concentration. Conclusion: The titratable acidity and the citric and malic acid contents of the fruits could be crucial factors responsible for enamel erosion. Therefore, fruit-based drinks should be regarded as potentially erosive.

• 한국식품과학회지
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• 제3권1호
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• pp.19-24
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• 1971

경기도 김포지방에서 수확한 농림6호를 1970년 3월에 현미와 백미로 표준도정하여 kraft paper bag에 포장하고 Co-60 irradiator로 30, 50, 600 및 800 Krad의 조사한후 저온($10^{\circ}C$, 75% RH)에 저장하면서 fat acidity, amylase activity, 백미가루와 그 전분의 amylogram에 의한 viscosity 및 식미시험 등의 시험 결과는 다음과 같다. 1) Fat acidity의 증가는 $30{\sim}50\;Krad$ 조사미에 있어서 대조구에 비해서 근소한 차이였으나, $600{\sim}800\;Krad$ 조사구에서는 현저하게 증가하였고, 상온 저장에 비해서는 그 증가율이 낮았다. 2) Amylase activity는, $30{\sim}50\;Krad$ 조사구에서 대조구와 차이가 없고, 모두 감소경향이며, $600{\sim}800\;Krad$ 조사구는 그 감소경향이 현저하다. 3) Brabender amylogram에 의한 viscosity는 백미분의 경우 $30{\sim}50\;Krad$ 조사구는 대조구와 차이없이 저장중 약간 감소경향이고, $600{\sim}800\;Krad$ 조사구는 현저하게 그 viscosity가 감소하였다. 4) 식미시험 결과는 $30{\sim}50\;Krad$ 조사구가 대조구와는 차이가 없고, $600{\sim}800\;Krad$ 조사구는 색깔에서만 대조구와 유의차를 나타냈다.

• 한국식품저장유통학회지
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• 제19권1호
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• pp.7-11
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• 2012

온주밀감의 산함량 감소를 목적으로 열처리를 실시할 때 습도와 가스조성의 환경조건이 과실 품질에 미치는 영향을 알아보고자 필름을 이용한 실험을 실시하였다. 필름은 18 ${\mu}m$ HDPE 천공필름, 30 ${\mu}m$ LDPE, 100 ${\mu}m$ LDPE 필름을 이용하였고, $30^{\circ}C$에서 55시간 열처리를 실시하였다. 열처리 후 산함량은 모든 처리구에서 처리 전보다 유의하게 감소하였고, 가용성고형물 함량은 변화가 없어 결과적으로 당산비가 증가하여 품질 향상의 효과가 있었다. 그러나 열처리 중 습도가 낮았던 필름 무처리구는 비슷한 가스조성의 HDPE 천공필름 보다 에탄올 및 아세트알데하이드 함량과 이취정도가 높은 경향이었고, 필름 처리구들 중에서도 필름 내부의 $CO_2$ 농도가 높고 $O_2$가 낮을수록 두 휘발성분 함량도 급격히 증가하고 이취발생이 심하여 신선도가 떨어지는 것이 관찰되었다. 결론적으로, 온주밀감의 산함량 감소를 위한 열처리 시 습도는 90%이상, 온도 처리실의 가스조성은 정상 대기를 유지하는 것이 이취관련 성분의 발생을 줄여 신선도를 유지할 수 있을 것으로 생각된다.