• Korean journal of food and cookery science
• /
• v.11 no.4
• /
• pp.356-361
• /
• 1995

This study was conducted to know the quality of marketed green teas which were devided into high, middle and low grade according to the price. we examined the content of water, ash, total nitrogen, tannin, caffeine, chlorophyll and color value and did sensory evaluation. The results were as follows: 1) The content of water was 2.17-3.67％ and content of ash was 4.50-5.17％, there were no significant difference in each grade. 2) The content of total nitrogen was 4.38％ in high grade, 4.60％ in middle grade and 4.68％ in low grade. 3) The content of tannin was 11.09％ in high grade, 14.22％ in middle grade and 14.44％ in low grade, middle and low grade were significantly higher than high grade. 4) The nitrogen rate to tannin (N/T) was 39.5％ in high grade, 32.6％ in middle grade and 32.70％ in low grade, N/T rate of high grade was significantly highest than others. 5) The content of caffeine is 1.78％ in high grade, 1.32％ in middle grade and 0.92％ in low grade, high and middle grade were significantly higher than low grade. 6) The content of total chlorophyll is 297.37 mg％ in high grade, 192.89 mg％ in middle grade and 204.79 mg％ in low grade, chlorophyll a was 69.23 mg％ in high grade, 51.99 mg％ in middle grade and 63.42 mg％ in low grade, and chlorophyll b was 228.47 mg％ in high grade, 131.21 mg％ in middle grade and 141.63 mg％ in low grade. 7) Yellow value of high and middle grade were significantly higher than low grade, but blue and red value were no significant diffrence in groups. 8) In sensory evaluation, appearance, taste, odor of high grade were better than others and total score was 15.25 in high grade, 12.97 in middle grade and 9.80 in low grade. 9) Price had a positive correlation with caffeine, appearance and taste, but a negative correlation with tannine. NT rate had a negative correlation with tannine, but a positive correlation with caffeine.

• Korean journal of food and cookery science
• /
• v.9 no.4
• /
• pp.323-328
• /
• 1993

Benzo(a)pyrene [B(a)P], one of the polycyclic aromatic hydrocarbons (PAHs) is known as a potent carcinogen. As lipid consumption increases recently, the toxic effect of overheated lipid foods and fats ＆ oils were reported increasingly. In this study, the contents of B(a)p, other PAHs and rancidities of soybean oil were determined, and then the proper heating temperature, time and frequency were recommended, The work was carried out using soybean oil heated at $180\pm$5^{\circ}C$$, $200\pm$5^{\circ}C$$, and $300\pm$5^{\circ}C$$,for 50 hours. Acid Value(AV) and Conjugated Diene Value of samples were determined. The contents of B(a)P and other PAHs contents of all samples were masured by HPLC/UV method. The results obtained were as follows; Each content of PAHs in the fresh soybean oil was: Pyr 1.093, B(a)A 0.986, Ch 1.147, DMBA 1.082, B(e)P 0.664, Per 1.135, B(a)P 0.146, DBA 1.053, 3-MC 0.05 rg/kg. When the soybean oil was heated at $180\pm$5^{\circ}C$$, for 10, 20, 30, and 50 hours, B(a)P conterlts in heated soybean oils were 0.391, 0.692, 0.451, and 0.372 $\mu\textrm{g}$/kg respectively. Acid value of them were 0.26, 0.26, 0.29, and 0.33, and conjugated diene value was 0.67, 0.76, 0.99, and 1.04, respectively. When the soybean oil was heated at $200\pm$5^{\circ}C$$,and $300\pm$5^{\circ}C$$,for 10, 20, 30, and 50 hours, B(a)P coiltents in soybean oil heated at $200\pm$5^{\circ}C$$,were 0.844, 0.512, 0.479 and 0.247 Ig/kg respectively, Acid value 0.22, 0.21, 0.23 and 0.51 and CDNV 0.39, 0.49, 3.27, and 3.89. B(a)P contents in soybean oil heated at $300\pm$5^{\circ}C$$,were 0.466, 0.706, 0.607 and 0.247$\mu\textrm{g}$/kg respectively, Acid value 0.47, 1.57, 3.90, and 6.42 and CDNV 0.65, 2.15, 3.00, and 3.88.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.31 no.2
• /
• pp.278-287
• /
• 1998

Carotenoids in integument of wild manchurian trout, Brachymystax lenok, and wild and cultured masu salmon Oncohynchus macrostomus, which are all the Korean native cold fresh water fish, were investigated by thin layer chromatography, column chromatography and HPLC. The total carotenoid contents of the wild manchurian trout were $3.72\;mg\%$ which is relatively higher compare to other species of salmonidae. The carotenoids were composed of $36.9\%$ zeaxanthin and $14.7\%$ $\beta-carotene$ as the major compounds, $7.8\%$ triol $7.3\%$ isocryptoxanthin, $5.7\%$ 4-hydroxy echinenone, $4.7\%$ lutein, $4.5\%$ salmoxanthin and $2.2\%$ astaxanthin as minor compounds, and other carotenoids such as canthaxanthin, tunaxanthin A, tunaxanthin B, tunaxanthin C, $\beta-cryptoxanthin$ and $\alpha-cryptoxanthin$ as minute carotenoids. Wild masu salmon contained more total carotenoids than cultured one and the contents were $0.82\;mg\%$ and $0.66\;mg\%$, respectively. The composition of the carotenoids from wild masu salmon were $20.7\%$ xeaxanthin, $17.0\%$ isocryptoxanthin and $15.8\%\;\beta-carotene$ as major compounds, and $6.2\%$ triol, $6.1\%$ 4-hydroxy echinenone, $6.1\%$ salmoxanthin, $5.9\%$ canthaxanthin, $5.8\%$ lutein, $4.9\%$ $\alpha-cryptoxanthin$ and $1.0\%$ astaxanthin as minor compounds. The composition of the carotenoids from cultured masu salmon were $19.7\%$ isocryptoxanthin, $18.0\%$ $\beta-carotene$ and $10.3\%$ zeaxanthin as the major compounds, and $8.9\%\;\beta-cryptoxanthin$, $8.5\%\;\alpha-cryptoxanthin$, $8.0\%$ lutein, $7.6\%$ canthaxanthin, $5.1\%$ triol and $2.0\%$ astaxanthin as minor carotenoids. Based on these data, wild masu salmon contained more zeaxanthin, salmoxanthin and 4-hydroxy echinenone while cultured masu salmon contained more $\alpha-cryptoxanthin$, indicating that carotenoid pigment of masu salmon depends on their living conditions. Unlike wild masu salmon, 4-hydroxy echinenone and salmoxanthin which are the characteristic carotenoids of salmons, were not found in the integument of cultured masu salmon. Unlike manchurian trout, both wild and cultured masu salmon did not contain tunaxanthin A, tunaxanthin B and tunaxanthin C.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.27 no.2
• /
• pp.114-120
• /
• 1994

To clarify the effect of storage temperature on the morphological and histological changes of plaice, Paralichthys olivaceus muscle at early stages after killing, the changes in breaking strength of muscle, morphological observation of myofibrils and histological observation of extracellular spaces during storage at $0^{\circ}C\;and\;10^{\circ}C$ were studied. The maximum breaking strength of samples stored at $0^{\circ}C$ was reached within 10hrs and then it dropped significantly (p<0.05) from 10hrs to 25hrs of storage. However, breaking strength was not increased in fresh muscle stored at $10^{\circ}C$ and gradually decreased after 10hrs storage. In myofibrils prepared from dorsal muscle immediately after death, A-band, I-band, H-band and Z-line in sarcomere were clearly distinguishable from each other. Due to muscle contraction, it was not easy to distinguish H-band from I-band observed in sarcomere stored at $0^{\circ}C$ after 10hrs storage. But, in the case of samples stored at $10^{\circ}C$, H-band could be observed dimly until 15hrs of storage. The changes in morphological myofibrils were closely related to increase of breaking strength. No extracellular space was observed among muscle cells immediately after killing. Stored samples at $0^{\circ}C$ showed extracellular spaces after 15hrs storage. On the other hand, samples stored at $10^{\circ}C$ didn't show any extracellular spaces until 15hrs storage and showed extracellular spaces after 24hrs storage. It was thought that the post-mortem tenderization of plaice muscle was closely related to the gradually disintegration of the extracellular matrix structure after killing.

• Korean journal of food and cookery science
• /
• v.16 no.6
• /
• pp.577-583
• /
• 2000

The purpose of this study was to investigate the effectiveness of various quality preservative treatments for extending shelf life and maintaining good quality of minimally processed fruit and vegetables produced in Korea. To determine the suitable treatments for delaying quality deterioration, fresh Asian pears and Chinese cabbages were sliced and treated with various quality preservatives (1% CaCl$_2$, 1% NaCl, 3% sucrose, 1% Ca-lactate, 1% vitamin C, 0.05% chitosan ＋1% vitamin C, 0.1% Sporix＋1% vitamin C, hot water (60$\^{C}$), 0.2% L-cysteine), packed with polyethylene film (60㎛-thick), and stored at 4$\^{C}$/0$\^{C}$ or 20$\^{C}$. Various biological and sensory tests were performed to evaluate the quality changes in minimally processed products. Results indicated that Chinese cabbages treated with 1% CaCl$_2$ at 4, and 1% CaCl$_2$ and 1% NaCl at 20$\^{C}$ were most effective in maintaining the quality and minimizing the biochemical changes during storage. For sliced Asian pears, 0.2% L-cysteine and 1% NaCl treatments were effective to reduce browning, and 1% CaCl$_2$ treatment was the most effective to prevent softening during storage at 20$\^{C}$ and 0$\^{C}$. Modified atmosphere packaging of Pleurotus ostreatus and Lentinus edodes had a significantly different shelf life depending on packaging material, packaging thickness and storage temperature. Sealed packaging with polyethylene film (60㎛-thick) for two kinds of mushrooms maintained a good quality with an extended shelf life by 30-50% at 20$\^{C}$ and by 30-130% at 0$\^{C}$. To minimize the quality deterioration which appeared in the condition of polyethylene film packaging, quality preservatives such as KMnO$_4$ and KHSO$_2$＋K$_2$S$_2$O$\_$5/ for SO$_2$ generation were added inside of mushroom packaging. The best condition for maintaining good quality longer was packaging with polyethylene film+SO$_2$ which showed 5080% extended shelf life for both Pleurotus ostreatus and Lentinus edodes at 20$\^{C}$ and 0$\^{C}$.

• Korean journal of food and cookery science
• /
• v.20 no.5
• /
• pp.436-443
• /
• 2004

The purpose of this study was to examine the physico-chemical and sensory characteristics of Kakdugi made with mashed red pepper. With regard to the pH of the Kakdugi, those of the juice from Kakdugi with red pepper powder and of the liquid with mashed red pepper were the highest and lowest immediately after preparation, respectively, but thereafter both slightly decreased, but were similar after the fifth week. Generally, the total acidity of Kakdugi liquid was the higher than that of Kakdugi juice. With regard to the L value, that of the Kakdugi juice was higher than that of Kakdugi liquid and that of Kakdugi with mashed red pepper washigher than that of Kakdugi with red pepper powder. From the third week, the 'L' values of all samples generally decreased. The 'a' value of the Kakdugi liquid with mashed red pepper during fermentation was highest During early fermentation, the juice of Kakdugi with red pepper powder showed a higher value than that of Kakdugi with mashed red pepper, but conversely, from the second week that of Kakdugi with mashed red pepper was higher than that of Kakdugi with red pepper powder. The 'b' value of the juice from Kakdugi with red pepper powder was highest until the second week, but from the third week that of Kakdugi with mashed red pepper was highest. With respect to the organic acids contents, those of citric, quinic and malic acids decreased, but those of lactic and acetic acids increased during fermentation progression. In addition, the citric, lacticand malic acids contents of the Kakdugi with mashed red pepper werethe highest, whereas that of quinic acid of the Kakdugi with red pepper powder was the highest. From the forth week, the acetic acid content of the Kakdugi with mashed red pepper was further increased. As a result of the sensory test, Kakdugi with mashed red pepper showed significantly higher values with regard to redness and fresh flavor, but in overall acceptability in the QDA, appearance and taste in the acceptance test. Therefore, our results indicate that mashed red pepper particularly increased the 'a' value and organic acid contents of Kakdugi compared to those of red pepper powder, leading to an increased overall acceptability.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.18 no.4
• /
• pp.309-315
• /
• 1985

This study was designed to compare the lipid components between wild and cultured snakehead, Channa argus. The lipid components of cultured snakehead were analyzed and compared with that of wild snakehead. In both edible portion and viscera, the lipid content in cultured, snakehead was higher than that in wild one. In the fatty acid composition of neutral lipid in edible portion, percentages of $C_{14:0},\;C_{16:0},\;C_{18:1},\;C_{20:5},\;C_{22:5}\;and\;C_{22:6}$ in cultured snakehead were higher than those in wild one, while percentages of $C_{18:0},\;C_{16:1},\;C_{18:2},\;C_{18:3},\;C_{20:4}\;and\;C_{22:4}$ lower. In the case of phospholipid in edible portion, percentages of $C_{16:0},\;C_{18:1}\;and\;C_{22:6}$ in cultured snakehead were higher than those in wild one, while percentages of $C_{16:1},\;C_{18:2},\;C_{18:3},\;C_{20:4},\;C_{22:4}\;and\;C_{22:5}$ lower. The unsaturation (TUFA/TSFA) and w3 highly unsaturated fatty acid content (w3 HUFA) of neutral lipid in cultured snakehead were higher than those in wild one, while those of phospholipid lower. The essential fatty acid contents (TEFA) of both neutral and phospholipids in wild snakehead were higher than those in cultured one. In the ratio (A/B) of fatty- acid content (A) in cultured snakehead to that (B) in diet, the A/B ratios of $C_{18:2\;w6},\;C_{18:3\;w3},\;C_{20:5\;w3}\;and\;C_{22:6\;w3}$ were 0.3 to 2.5 times, and it is considered to be related to the biosynthesis of polyenoic acids and growth rate of cultured snakehead.

• Korean Journal of Food Science and Technology
• /
• v.2 no.2
• /
• pp.8-16
• /
• 1970

Exploitation of leaf protein concentrates for human consumption is very important. Leaf protein concentrates can be easily prepared by mechanically mincing leaves material and press it for getting the juice. Crude protein can be separated from the juice by aging, adjusting the pH, or heating to $75-80^{\circ}C$ etc. This report deals with the extractability of total-N from 69 species of fresh leaves by mechanical process, and then compared the recovery of leaf protein concentrates from leaf extracts by treating with TCA, pH adjustment and heating. Results are summarized as follows. 1. In general, the greater the content of total-N of leaves the greater the percentage extraction. Extraction of the juice from leaves is needed at least two times. The simple equations are constituted between the total-N (T; %) and the first and second extractability ($E_1,\;E_2;\;%$) of the total-N of leaves, as follows: $E_1=0.8168T\;E_2=0.1830T$ 2. The optimum pH value for coagulating protein from extracts is considered to be 3.5 to 4.5. However, the products of leaf protein concentrate by the pH adjustment of extracts are generally dull in color with rich elasticity. 3. Recoveries of the leaf protein concentrate from extracts by treating methods were in the following order of TCA treatment> pH 4 treatment> pH 3 treatment> heat treatment. The yield of leaf protein concentrates decreased bout 10% with pH 4 treatment, 11.4% with pH 3 treatment, and 14.8% with heat treatment compared with the TCA treatment. 4. The heat treatment is the most benifitial method for the production of leaf protein concentrates with regard to properties of texture, color and yield of products and easiness of the treatment method.

• Korean Journal of Food Science and Technology
• /
• v.2 no.2
• /
• pp.17-25
• /
• 1970

Juice were extracted from fresh leaves of 70 species of plants growing in Korea by mincing and pressing the resulting pulp through a cotton cloth. Leaf protein concentrates could be prepared from many species of land and water plants that are at present economically unimportant. The choice of plants is of considerable important. Total-N, protein-N and pH determinations were made on the extracts, and total-N remaining in the fibre were calculated. Leaf protein concentrates were precipitated from the extracts at $75{\sim}80^{\circ}C$, and analysed total-N as protein-N of products. The present paper deals with the calculated yields of leaf protein concentrates from various plants, relations between yield of leaf protein concentrates and total-N of leaves, or pH of extracts, and the amino acid compositions of leaf protein concentrates. Results are summarized as follows. 1. Spinach and radish were the best sources of easily extractable, but good results were also obtained with indian mustard, kail, chenopod, red bean, cucumber, squash, houndberry, white flowered gourd, potato, Humulus japonicus, arrowroot and soybean as a good resources for the production of leaf protein concentrates. 2. In general, the greater the protein content of leaves the greater the yield of leaf protein concentrates. However, there are some plants difficult to make a adequate protein extraction by a simple mechanical process. 3. It was to be expected that leaf protein concentrates would be more extractable with the higher pH of extracts. There were a poor yield of the leaf protein concentrate in the pH values lower than 5.50 of the first extracts. 4. Protein content of the leaf protein concentrate shows marked differences, depending on species and season. It ranged between 29 to 80% of protein contents. However, the majority of plants yielded products containing more than 50% of protein. Products containing more than 75% of protein were obtained from two species of radish and indian mustard. Cabbage and Digitaria sanguinalis cilialis (summer) made products containing 29 to 32% of protein. 5. The amino acid composition of leaf protein concentrates was not greatly altered by species of plants. On an amino acid compositional basis, the leaf protein concentrate has a favorable balance of essential and non-essential amino acids, the only exception being methionine, which was usually low in all cases.

• Korean journal of food and cookery science
• /
• v.14 no.4
• /
• pp.394-399
• /
• 1998

The juice of garlic (Euichun variety) was extracted and concentrated by heating at 90$^{\circ}C$, by using a rotary vacuum evaporator at 45$^{\circ}C$, or by freezing at -50$^{\circ}C$ until the volume was reduced to 70% of the original's. The concentrated garlic juice was packed into 15 ml test tubes wrapped with aluminum foil and kept at 4$^{\circ}C$ or 25$^{\circ}C$ for 60 days. Changes of browning, microbiological and sensory characteristics of the concentrated garlic juices were monitored every 10 days. The specific gravity and viscosity of the prepared juices decreased in the juices concentrated at 90$^{\circ}C$, 45$^{\circ}C$ and -50$^{\circ}C$ in order. Browning of the concentrated garlic juices was slower during the storage at 4$^{\circ}C$ than at 25$^{\circ}C$. Browning occurred rapidly in the juice concentrated at 45$^{\circ}C$ during the storage, especially at 25$^{\circ}C$. The numbers of mesophilic and psychrotrophic bacteria in the juices did not increase significantly during the storage, which means the garlic juices had good shelf-life. The CFUs/ml of garlic juice concentrated at 90$^{\circ}C$ were lower about 1 to 2 log cycles than those in other concentrated juices. The juice concentrated at 90$^{\circ}C$ showed the weakest garlic odor and the strongest cooked odor among the juices. The juice concentrated at -50$^{\circ}C$ had the freshest odor, especially stored at 4$^{\circ}C$, but the juice concentrated at 90$^{\circ}C$ had lowest score in fresh odor. Brown color was dark in the juice concentrated at 45$^{\circ}C$ and green color of all the juices did not change significantly during the storage.