• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1169-1178
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• 1998

This study was performed to purify fig pectinesterase(F-PE) and characterize its in situ activity. Three kinds of F-PE were partially separated by using ammonium sulfate fractionation, Q-Sepharose column, CM-cation exchanger column chromatography, and HPLC. One of those was anionic protein and the others were cationic proteins. All of them had approximate molecular weight of 27,000 and lost rapidly their activity during storage. Therefore alternative crude enzyme was prepared by suspending the freeze dried and milled fig powder in 0.1 M NaCl at pH 7.5. F-PE had the optimum pH of 8.5, the optimum temperature of $50^{\circ}C$ with activation energy of 7,671 cal $mol^{-1}K^{-1}$ and stability up to $55^{\circ}C$ with 10 minutes heating. Optimum activity was obtained in $0.2{\sim}0.4$ M NaCl with optimum solubility at above 0.8 M NaCl.

• Korean journal of food and cookery science
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• v.18 no.2
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• pp.200-205
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• 2002

Corn starch was modified by the oxidation with sodium hypochlorite(NaOCl) and the changes in the distribution of molecular weight were examined. Corn starch was oxidized with 0.25, 0.5, 0.75, 1.0, and 1.5% active Cl/g of starch at pH 7.0 and 25$^{\circ}C$ for 10 min. Oxidation of corn starch caused a change in the molecular weight distribution of amylopectin. The fraction of highest molecular weight in native starch decreased gradually and the fraction of lower molecular weight increased with increasing oxidation. Also, λ$\sub$max/ and iodine binding capacities of oxidized starches decreased and the soluble carbohydrate content increased by oxidation. The differential scanning calorimetric results of oxidized starches showed that the temperature and enthalpies of gelatinization were not changed by oxidation; however, the more the starch was oxidized, the greater the extent of retrogradation.

• Korean Journal of Food Science and Technology
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• v.30 no.1
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• pp.97-102
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• 1998

Arrowroot starches, harvested in March, June, September and December, indicated that the December starch had the lower values of amylose content, ${\beta}-amylolysis$ limit and intrinsic viscosity, but the highest value of water-binding capacity. The swelling power were similar among different starches. The gelatinization by KSCN revealed that the December starch was the most resistant to alkali gelatinization. Gelatinization temperature, determined by differential scanning calorimetry, of the December sample was shifted to higher temperture by $1^{\circ}C$ compared with the others. When the December starch was heated at $98^{\circ}C$ for 8min, 93.8% of total amylose and 7.2% of total amylopectin were solubilized, which was the highest and the lowest, respectively.

• Korean Journal of Food Science and Technology
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• v.27 no.5
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• pp.673-679
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• 1995

Pectinesterase(PE) has been definitively established as the causative agent for clarification of citrus juice and gelation of frozen concentrates. This enzyme is present in multiple forms in citrus fruit. Although representing a minor fraction of the total PE activity, thermostable pectinesterase(TSPE) accounts for the severe time/temperature processing treatment required to inactivate PE. This study was undertaken to separate and purify thermolabile pectinesterase(TLPE) and TSPE from the crude PE extracts of Valencia orange rag-pulp powder. The approach taken was to carry out the three kind of chromatographies of CM-Sephadex C-50, Phenyl Sepharose CL-4B and CM-Biogel A to the unheated crude PE or the heated crude PE. All of them used could increase the purity of PEs and, specially, Phenyl Sepharose CL-4B chromatography could separate crude PE as the mixture of PEs into two forms of TLPE and TSPE. The purified TLPE had specific activity of 1,005 units/mg, yield of 13.6% and purification of 35 fold, while the TSPE separated from the unheated crude PE showed specific activity of 3,115 units/mg, yield of 1.5% and purification of 100.5 fold, and another TSPE from the heated crude PE was found to be specific activity of 1,803 units/mg, yield of 15.4% and purification of 140 fold.

• Korean Journal of Food Science and Technology
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• v.16 no.1
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• pp.41-46
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• 1984

The pectic enzymes produced from Aspergillus niger were separated into three fractions (F-A, F-I and F-II) by means of Sephadex and DEAF-Sephadex column chromatography. Each enzyme fraction was characterized by determining viscosity change and reducing surgar of the pectic acid-enzyme mixture and analyzing thin layer chromatogram of the reaction products. F-I rapidly reduced the viscosity of pectic acid solution and released reducing groups in a random manner so that appeared to be an endo-polygalacturonase (endo-PG). The optimum pH of endo-PG for viscosity reducing activity was 4.2 and that for releasing reducing surgar was 4.7. In the thermal inactivation of endo-PG of $30-45^{\circ}C$, the enthalpy of activation was 217.3 kj/mole and z-value was $7.5^{\circ}C$. F-II and F-A were determined as endo-polymethylgalacturonase and exo-polygalacturonase, respectively.

• Korean Journal of Food Science and Technology
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• v.21 no.1
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• pp.52-57
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• 1989

Large and small starch granules were isolated and characterized from kernels of Hiproly barley. Average size of large granules were $28-30{\mu}m$ and that of small granules were $6{\mu}m$. The small granules consist of 95% of total starch granules. Large granules contained more amylose than small granules. Distribution of isoamylase-debranched starch components, X-ray diffraction patterns, gelatinization characteristics by differential scanning calorimetry, and starch-granule susceptibility to acid were investigated. Large granules contained more long B chains of amylopectin and had the lower ratios of Fr. III to Fr. II , which represent one of the structural characteristics of amylopectin, than those of small granules. Small granules had higher conclusion temperature and smaller heat of gelatinization than those of large granules by D.S.C.. Both granules had A-type pattern of X-ray diffractopgrams, but hydrolysis of granules with acid showed different A-type patterns between large and small granules.

• The Journal of Natural Sciences
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• v.8 no.2
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• pp.49-55
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• 1996

In order to survey the safety of some food additives, antimicrobial activity of acidulants, stabilizers, antioxidants, natural coloring materials and bleaching agents against 5 strains of bacteria and Sacch. cerevisiae were investigated by dilution method and minimal inhibitory concentration(MIC) method. Malic acid as acidulants displayed the effective antimicrobial activity in vitro against P. aeruginosa and its MIC is 0.05%. Alginic acid and pectin as stabilizer also displayed strong antimicrobial activity against B. subtilis, E. coli and P. aeruginosa, and tannin(antioxidants) and $NaHSO_3$ displayed antimicrobial activity against all bacteria tested. However gums(Arabia, Xanthan, Gua) and natural coloring materials(Hongwha Yellow, Red powder-N) were not affected to growth of bacteria and Sacch. cerevisiae.

• Food Science and Preservation
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• v.7 no.1
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• pp.38-43
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• 2000

Changes in firmness and pectin contents during maturation and sotrage of Stsuma mandarin (Citrus Unshiu Marc. var. miyagawa) were investigated. Firmness of fruits was decreased quickly from 1,176.8g-force to 503.6g-dorce. Satsuma mandarin was stored at 3$^{\circ}C$ and 85%${\pm}$5% relative humidity. Firmness were decreased from 538.9g-force to 336.9g-force during storage. Alcohol-insoluble solid(AIS) of peel and flesh were decreased quickly from 27.04g/100g to 12.30g/100g, and from 2.67g/100g to 1.91g/100g during maturation of fruits. During storage of fruits, AIS of peel was decreased from 14.32g/100g to 12.06g/100g . During maturation of fruits, water soluble pectin (WSP) of peel were increased from 420.82mg/100g to 601.62mg/100g as wet basis. Hexametaphosphate soluble pectin (HMP) was also increased from 450.17mg/100g to 577/53mg/100g. hydrochloricacid soluble pectin (HSP) was decreased from 1938.30 mg/100g to 695.14mg/100g. During storage of fruits, HMP and HSP of peel was decreased from 507.82mg/100g to 695.14mg/100g. During storage of fruits, HMP and HSP of peel was decreased from 527.82mg/100g to 275.47mg/100g , and from 672.28mg/100g to 351.36mg/100g, respectively. WSP of peel was increased from 543.70mg/100g to 584.31mg/100g. Total pectin substance (TPS) of peel was decreased from 2809.79 mg/100g to 1874.29mg/100g during maturation, and from 1723.80mg/100g to 1211.14mg/100g during storage, respectively. Composition ratio of pectin was in order of WSP>HSP>HMP.

• Korean Journal of Food Science and Technology
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• v.29 no.5
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• pp.876-881
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• 1997

The relationship between the molecular structure of acid-hydrolyzed rice starch and the retrogradation rate of starch gel was investigated. The molecular structure of starch was modified by acid hydrolysis with 1 N HCl at $35^{\circ}C$. The molecular weight of starch decreased as acid hydrolysis time was increased. At the early stage of hydrolysis up to 3 hr, the branching point of amylopectin was degraded and thereafter both ${\alpha}-1,4\;and\;{\alpha}-1,6$ linkages were hydrolyzed. The starch gel (50%) stored at $20^{\circ}C$ revealed that the rapid retrogradation occurred during 4 hr of storage which was more pronounced as the hydrolysis time increased. The degree of retrogradation of starch gels after 4 hr storage showed a linear relationship with the yield of hydrolyzate. These results suggested that the retrogradation of starch gel was accelerated by degradation of ${\alpha}-1,6$ linkages with acid.

• Korean Journal of Food Science and Technology
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• v.30 no.3
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• pp.569-573
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• 1998

This study was conducted to investigate the differences of textural characteristics and microstructure of sugared chestnuts between heated by a heater and microwave. Raw chestnuts were boiled and infiltrated the sugar in sugar syrup by heating. The content of WSP (water soluble pectin) was increased, but HSP (hydrochloric acid soluble pectin) was decreased by boiling and sugaring. This change was remarkable when it was boiled and sugared by a microwave heating. The hardness, gumminess and chewiness were more decreased in the sugared chestnut boiled and sugared with a microwave than that processed with a heater. Microstructure of sugared chestnut processed with a microwave heating showed the distruction of cell wall.