• Journal of the Korean Society of Food Science and Nutrition
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• v.39 no.10
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• pp.1476-1480
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• 2010

Physicochemical properties of flours prepared from sweet potatoes with different flesh color (white, yellow/orange and purple) were investigated. Sweet potatoes were soaked in solutions of antibrowning agents such as sodium metabisulfite and citric acid, and freeze or hot air-dried prior to grinding to produce sweet potato flours. Sweet potato flours with different flesh colors showed differences in chemical composition. Purplefleshed sweet potato flour had higher protein, ash, and dietary fiber contents that white and yellow/orangefleshed sweet potato flours. Average particle size of yellow/orange-fleshed sweet potato flour was higher than those of white/yellow or purple-fleshed sweet potato flour. Both water absorption index (WAI) and oil absorption capacity of flours prepared from sweet potatoes by hot-air drying were higher than those from sweet potatoes by freeze drying.

• Korean Journal of Food Science and Technology
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• v.27 no.5
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• pp.819-825
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• 1995

Two sweet potato CV.(Ipomoea batatas) were examined, i.e. purple flesh sweet potato(PSP) and light yellow flesh sweet potato(LYSP) which varied in degree of sweetness. On a fresh weight basis, nitrogen free extract in cultivars ranged from $25.73{\sim}26.24%$ and PSP contained more crude fat than LYSP. Total amino acids of PSP and LYSP were 5676.57mg% and 4550.86mg%, respectively. Aspartic acid, serine, alanine and valine were the major components in sweet potatoes. Sulfur-containing amino acids are the first limiting amino acid in PSP. The major fatty acids in PSP and LYSP analyzed by GC were palmitic acid, linoleic acid. The content of the saturated fatty acid was less than that of the unsaturated fatty acid. Carbohydrate contents were $75.43{\sim}79.10%$ and neutral sugars contents were $67.22{\sim}64.85%$(dry wt). Two sweet potato CV. contained the most glucose of all neutral sugars. PSP contained 11.88% for uronic acid, 59.42% for starch. Free sugars of PSP(0.82%) was much less than that of LYSP(2.53%). The contents of thiamin, riboflavin and niacin were similar, and the ascorbic acid contents in PSP and LYSP were 63.4mg% and 48.7mg%(dry wt), respectively. Comparing the mineral content in PSP, K was the greatest element in concentration followed by mg, Ca, Na. The total dietary fiber(TDF) value was 13.43% in PSP, 9.79% in LYSP respectively. The ratio of soluble dietary fiber(SDF) content and insoluble dietary fiber(IDF) content to TDF content for PSP were 57.6%, 42.4%, respectively.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.1
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• pp.37-46
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• 2011

Polyphenolic content and antimutagenicity of the methanol extracts prepared from 22 cultivars of sweet potato with different flesh colors were investigated using Folin-Ciocalteu's phenol reagent method and Ames test, respectively. There was a remarkable cultivar difference in the polyphenolic content of sweet potato. Su, Hayanmi and Shinhwangmi among 17 cultivars of non-purple sweet potato had higher polyphenolic contents of 21.4, 21.5 and $20.3{\mu}g$ (GAE/g dried sweet potato), respectively, whereas Manami and Yeonhwangmi were very much lower at 4.6 and $4.8{\mu}g$. Mokpo No.62, Borami, Sinjami, Jami and Ayamurasaki had much higher polyphenolic contents of 67.7, 76.9, 44.9, 128.3 and $93.2{\mu}g$, respectively, than non-purple sweet potato. The methanol extract from the sweet potato effectively inhibited the reverse mutation induced by 1-NP, daunomycin, Trp-P-1, Trp-P-2 and 2-AA on S. Typhimurium TA 98, and by 1-NP on S. Typhimurium TA 100. These results suggest that the antimutagencity properties may be influenced by the tested mutagen and strain rather than the polyphenolic content of non-purple and purple sweet potato. However, in the purple sweet potatoes, a high polyphenolic content may influence the antimutagencity properties.

• Korean journal of food and cookery science
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• v.27 no.2
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• pp.19-29
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• 2011

Sweet potato powders made from eight Korean varieties, including purple-fleshed, orange-fleshed, and commercial dry type sweet potatoes, were investigated for physicochemical and pasting properties to develop processed food. Crude protein and lipid contents of Shinjami and Borami were higher than those of other varieties. The lightness value of raw sweet potato flesh was the highest value in Shinchunmi, and the lowest in Shinjami. Using the color difference (${\Delta}E$), color similarities compared to the white plate occurred in the following order; purple-fleshed > orange-fleshed > commercial dry type sweet potatoes. Total and damaged starch contents were significantly different (p<0.05). Total starch content of sweet potatoes was higher in commercial dry sweet potatoes (61.89-70.46%), particularly Shinchunmi (70.46%) but lower in orange-fleshed sweet potato (48.87 and 49.53%, respectively). Water binding capacity of Yeonwhangmi, swelling power and solubility of Shinyulmi were the highest values (174.70, 25.54 and 87.49%, respectively) among them (p<0.05). But oil absorptions of Shinyulmi and Shinchunmi showed lower values (97.08 and 97.54%, respectively). All sweet potato powders had an A type x-ray diffraction pattern. The initial pasting temperatures of sweet potato powders ranged from 69.50 to $75.95^{\circ}C$ and the amylolytic enzyme in sweet potato powder lowered pasting viscosity.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.50 no.spc1
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• pp.141-146
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• 2005

The objective of this study was to determine the characterisics of quality and antioxidant with various sweet potato(SP) varieties. The differences of skin color between general and colored SP was not significant. The flesh color of steamed SP was the lower than flesh of raw SP, and especially steamed purple SP(5.24) was lower than flesh SP(22.0). In physical characteristics, the hardness of raw SP showed the low values and the springness, gumness and hardness among steamed SP varieties was not significant. The total phenol content(TPC) of purple, yellow-fleshed and general SP had 13.1, 6.22 and 3.02 mg/g, respectively. In DPPH, the purple-fleshed SP had the highest free radical scanvering. Also, shingunmi$(88.5\%)$, Saengmi$(80.9\%)$ and Shinchunmi$(78.9\%)$ show the high antioxidant activities. The redness of SP was positively correlated with TPC in raw and steamed. However, the yellowness of flesh SP was negatively correlated with DPPH.

• Korean Journal of Food Science and Technology
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• v.28 no.6
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• pp.1180-1183
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• 1996

Growth characteristics and changes of pigment content of purple sweet potato (PSP) during growth were investigated. Vine length of PSP was increased to the maximum length of 130 cm after 100 days of growth. Numbers of branches and nodes were increased to the maximum of 21and 550, respectively, after 120 days of growth. Vine weight was also increased to the maximum of 4,384 kg/10a after 120 days of growth, while the weight of marketable root was increased continuously to the end of the growth period of 150 days to reach the production of 1,875 kg/10a. Uniquely considerable amount of anthocyanin pigment has been developed in both skin and flesh of young roots harvested after 40 days of growth. The pigment content was increased slowly until 140 days of growth then decreased. This fact indicates that the best time for harvesting of PSP is 140 days after planting.

• Journal of Applied Biological Chemistry
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• v.58 no.1
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• pp.21-24
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• 2015

Antioxidant activities of ethanol extracts from three types of sweet potatoes with distinctive flesh color (white, orange, and purple) were investigated. Total phenolic content of purple-fleshed sweet potato (PF) was always 2- to 5-fold higher than those of white-fleshed (WF) and orange-fleshed sweet potato (OF). 2,2-diphenyl-1-picryl-hydrazyl free radical scavenging activity of 70% ethanol extracts was highest ($EC_{50}$ = 0.179 mg/mL) for PF and lowest ($EC_{50}$ = 2.127 mg/mL) for OF. And then, reducing power was also highest ($EC_{50}$ = 0.236 mg/mL) for PF and lowest ($EC_{50}$ = 1.587 mg/mL) for WF. Antioxidant activities of 70% ethanol extracts were closely related to the amount of total phenolics. These results imply that antioxidant activity of PF is 6.7 to 11.9 times higher than those of WF and OF.

• Korean Journal of Food Science and Technology
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• v.28 no.2
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• pp.345-351
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• 1996

Studies on extraction and color characteristics of purple sweet potato (PSP) pigment were performed to provide the basic information for the utilization of PSP as a new source of natural food colorant. PSP pigment was extracted well with the polar solvents such as distilled water, ethanol, and methanol. but hardly extracted with the non-polar solvents. Among the tested solvents, 20% ethanol solution containing 0.1% citric acid was found to be the most efficient for extraction of the pigment from PSP. PSP contained high amount of pigment not only in the epidermis but also in the flesh of the potato. The PSP pigment was heat stable even under pretreatments such as autoclaving and blanching of the potato before extraction. The optimum temperature of the extraction for the PSP Pigment was decided to be $30^{\circ}C$ by considering the stability and the rate of extraction. The pigment was markedly influenced by the change of pH. The color of the pigment solution was red at the pH range of $1.0{\sim}3.0$, became blue at $7.0{\sim}8.0$, then turned green at $9.0{\sim}10.0$. A characteristic batho-chromic shift of the pigment solution was observed as the pH of the solution increased.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.6
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• pp.955-961
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• 2014

This study was carried out to investigate the amounts of vitamin C in 22 sweet potato cultivars cultivated in Korea as well as evaluate the effects of cooking methods on vitamin C contents. Methods for determining vitamin C was validated by determining linearity, specificity, limit of detection (LOD), limit of quantification (LOQ), precision, and accuracy using HPLC. Results showed high linearity in the calibration curve with a coefficient of correlation ($R^2$) of 0.9999. The LOD and LOQ values for ascorbic acid (AA) were 0.03 and $0.10{\mu}g/mL$, respectively. The relative standard deviations (RSDs) for intra- and inter-day precision of AA were less than 5%. The recovery rates of AA and dehydroascorbic acid (DHA) were in the range from 98.21~98.64 and 98.28~100.68%, respectively. Depending on cultivar, contents of AA, DHA, and total ascorbic acid (TA) in sweet potatoes varied in the range from 37.76 (Sinyulmi)~89.25 (Juhwangmin), 23.37 (Sinjami)~63.94 (Sinyulmi), and 68.52 (Sinjami)~115.95 (Juhwangmin) mg/100 g, respectively, and their average levels were $56.98{\pm}12.53$, $36.46{\pm}9.03$, and $93.44{\pm}12.00mg/100g$, respectively. The average TA levels were also dependent on flesh color, whish was significantly higher in general sweet potato and orange sweet potato than in purple sweet potato. Steaming, baking, and frying processes significantly reduced AA (10.61~58.41%), DHA (2.57~52.81%), and TA (14.54~49.92%) contents in sweet potatoes. The highest reduction of AA, DHA, and TA contents was observed after baking, followed by steaming and frying. We expect that the basic information provided by this study will be useful to plant breeders and food scientists.