• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.9
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• pp.1317-1324
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• 2015

The objective of this study was to examine both antioxidant activities and quality characteristics of sausages made from a mixture of purple sweet potato powder and pigment. Five sausages were manufactured: F0 (control), F1 (0.15%-sodium nitrite), F2 (0.2%-purple sweet potato pigment), F3 (0.2%-purple sweet potato pigment and 5%-purple sweet potato powder), and F4 (0.2%-purple sweet potato pigment and 10%-purple sweet potato powder). Sausages were stored at $4{\pm}1^{\circ}C$ for 30 days. Total polyphenol, 2,2-diphenyl-l-picrylhydrazyl (DPPH) radical scavenging activity, acid value, peroxide value, volatile basic nitrogen (VBN), and total bacterial cell contents were analyzed. Total polyphenol content and DPPH radical scavenging activity increased according to the amount of purple sweet potato, whereas acid value, peroxide value, and VBN decreased. Addition of 0.2% purple sweet potato pigment increased lipid oxidative stability and protein deterioration inhibitory effect compared to F0, but not to the levels of 0.15% sodium nitrite. However, F2 showed the lowest pH during storage due to the pH (2.52) of the pigment. Microorganism analysis revealed that total bacterial counts of sausage added with 0.2% purple sweet potato pigment were significantly lower (P<0.05) than that of sodium nitrite-supplemented sausage. As a result, purple sweet potato powder and pigment demonstrate antioxidative activity and lipid oxidative stability in sausages, making them suitable ingredients for manufacturing sausages.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.5
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• pp.790-795
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• 2000

To establish the optimum conditions for the extraction of anthocyanin pigment from purple-fleshed sweet potato, a suitable extraction solvent with the optimum citric acid concentration for acidification of the solvent, and the optimum extraction time and temperature were determined. Twenty percent ethanol solution acidified with citric acid was found to be a good solvent for the extraction of the pigment from purple-fleshed sweet potato. About 10 hour extraction at room temperature was appropriate for the extraction. pH of the extract was below 3 when more than 0.7% citric acid was added. The higher the concentration of citric acid added was, the higher the total optical density (TOD) of the extract was. However, the increase in TOD of the extract was insignificant when more than 1% of citric acid was added. Therefore, addition of 1% citric acid was determined for acidification of the extracting solvent. Though the initial rate of the pigment extraction increased as the extracting temperature increased, extraction at higher temperatures of 60 or 8$0^{\circ}C$ for an extended time caused a decrease in the extraction yield due to degradation of the pigment. The optimum extraction temperature for the anthocyanin pigment from purple-fleshed sweet potato with the solvent used was determined as 4$0^{\circ}C$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.6
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• pp.896-903
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• 2015

The objective of this study was to investigate the effect of nitrite substitution of sausage with purple sweet potato by examining the quality characteristics of sausage. Four sausage samples were prepared as follows: F1 (0.15% sodium nitrite), F2 (0.2% pigment), F3 (0.2% pigment and 5% powder), and F4 (0.2% pigment and 10% powder). A substitution of sodium nitrite with 0.2% purple sweet potato pigment reduced redness while increased yellowness. However, the addition of 5% purple sweet potato powder to 0.2% purple sweet potato pigment increased redness while reduced yellowness, which was similar to those of sausage with 0.15% addition of sodium nitrite. Further, color change increased as the content of purple sweet potato increased. As the amount of purple sweet potato increased, the contents of Ca, K, and Mg increased but hardness, gumminess, and chewiness decreased. In the sensory evaluation, the addition of purple sweet potato did not influence on appearance, color, or flavor. However, the addition of 10% purple sweet potato decreased the taste and texture of sausage. Correlation coefficients between overall acceptability, texture, appearance, color, taste, and flavor were 0.901, 0.895, 0.877, 0.844, and 0.688, respectively. Therefore, proper content of purple sweet potato powder and purple sweet potato pigment were determined to be 5% and 0.2%, respectively, for the substitution of sodium nitrite.

• Food Science and Preservation
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• v.8 no.1
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• pp.102-108
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• 2001

Flow properties of the concentrated pigment solutions extracted from purple-fleshed sweet potatoes were determined using a cone and plate rotational viscometer for soluble solids concentration range of 25 to 65% at temperature range of 20 to 60 $^{\circ}C$. The purple-fleshed sweet potato pigment solutions exhibited Newtonian behavior. Temperature dependency for the viscosity of the solution followed the Arhenius relationship with activation energy values between 14.23 and 43.00 kJ/mol, which increased linearly with soluble solids concentration. A relationship between viscosity, temperature and soluble solids concentration was investigated. At the same temperature, the viscosity of the concentrated pigment solutions increased exponentially as the concentration increased with higher degree of such phenomena at lower temperatures.

• Korean Journal of Food Science and Technology
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• v.29 no.3
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• pp.497-501
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• 1997

Kinetic parameters on heat-induced color changes of anthocyanin pigment from purple sweet potato were determined in the temperature range of $121{\sim}141^{\circ}C$. Color change determined by a browning index $(A_{532}\;nm/A_{420}\;nm)$ followed second order reaction kinetics. Activation energy values of purple sweet potato pigment solutions of pH 2.0, 3.0, 4.0 and 5.0 were 69.57, 76.68, 81.07 and 92.98 kJ/mol, respectively, indicating that temperature dependency of the reaction increased with pH. Apparent kinetic compensation effect between preex-ponential factor and activation energy value was observed.

• The Korean Journal of Food And Nutrition
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• v.23 no.1
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• pp.23-29
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• 2010

Pigment concentrates with violet-red color and sweet taste were obtained from purple-fleshed sweet potato(PFSP) using ethyl alcohol and water. Extract from general potato(GP) were used as a control. The relative stability of PFSP pigment concentrate(PFSPPC) in a storage test over 15 days was confirmed in the order of dark > fluorescence > sun-light irradiation. The relative stability of GP pigment concentrate(GPPC) in a storage test over 15 days was confirmed in the order of sun-light > fluorescence > dark storage. The RRP of PFSPPC was higher than that of GPPC, but the color strength of GPPC was 1/2 that of PFSPPC. Treatment of PFSPPC with aluminum potassium sulfate(0.2~0.3%, w/w) best improved its stability. The improved RRPs of PFSPPC were 45.16~47.31% in sun light irradiation, 55.91~60.22% in fluorescence irradiation, and 76.34~75.97% in dark storage conditions. In substituting aluminum potassium sulfate for chitosan, an amount of 0.2~0.3%(w/w) was suitable, giving similar results in improving pigment stability for all concentrates tested. Also, freeze-dried PFSPPC powder was manufactured as a substitute for dextrin, and also as a substitute for chitosan to the extent of 0.25%(w/w). The results of storage stabilite for freeze-dried PFSPPC and GPPC powder over 15 days, irradiation were, PRRs of 74.47~89.36% and 61.54~76.92%, respectively. The stability improving effect of freeze dried PFSPPC powder was confirmed by the results of storage experiments at various conditions. The use of freeze-dried PFSPPC powder was therefore confirmed to be an effective treatment for general foods.

• Korean Journal of Food Science and Technology
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• v.33 no.6
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• pp.808-811
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• 2001

Performance of pilot plant scale extraction and concentration of purple-fleshed sweet potato anthocyanin pigment was tested and the characteristics of pigment extracts and concentrates were investigated. Fifty kilograms of purple-fleshed sweet potato was extracted with 500 L of 1% citric acid in 20% ethanol. As a whole, extraction pattern of the large scale extraction was similar to that of the laboratory scale extraction. The extracted pigment solution was filtered twice with a bag filter and a winding type microfilter and the filtrate was concentrated by a large scale vacuum evaporator at $40^{\circ}C$ and 600 mmHg vac. The mean values of total optical density (TOD) of the extract and the concentrate were 6.53 and 120.45, respectively. Browning index (BI) and Degradation index (DI) of extract were 5.86 and 1.55 and those of concentrate were 5.89 and 1.56, respectively, which indicated that the pigments were not changed or degraded through the extraction and concentration process.

• Food Science and Preservation
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• v.6 no.4
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• pp.442-447
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• 1999

A curd yogurt was prepared by fermenting milk added with skim milk powder and purple sweet potato by culture of 5 types of lactic acid bacteria(Lactobacillus delbruekii sub. sp. lactis, Streptococcus lactis, acidity, number of viable cell, stability of purple sweet potato's pigment and keeping qualify. Among the organisms tested, the acid production and number of viable cell by the culture of L bulgaricus remarkably increased for the first 12 hem which showed 1.04${\times}$10$\^$9/ CFU/mL in number of viable cell and 4.22 In pH where as fermentation by the culture of B. bifidum was slow. After 36 hours of incubation which showed 3.3 ${\times}$ l0$\^$8/ CFU/mL in number of viable cell and 5.1 in pH. In stabilities of purple sweet potato anthocyanin pigment n fermentation, yogurt by B. bifidum was found to be most stable followed by Leuc. lactis, L. delbruekii sub. sp. lactis, L bulgaricus, but yogurt by St. lactis was not stable. When curd yogurt added with Purple sweet Potato was kept at 2∼3$^{\circ}C$ for 14 day, its keeping quality(pH, titratable acidity, number of viable cell) was relative good except product by L. bulgaricus was found to be decreased most of viable cell. After 2 weeks of keeping, pigment of yogurt was decreased by B. bifidum, stable by L. delbruekii sub. sp. lactis.

• Korean Journal of Food Science and Technology
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• v.29 no.3
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• pp.492-496
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• 1997

Purple sweet potato pigment extract was concentrated using both membrane separation method and vacuum concentration method. The pigment extract (anthocyanin content 1.6 g/L) was concentrated $({\times}25)$ after 5 hr of continuous operation of a nanofiltration to get anthocyanin content of 10.6 g/L. Total solid content also increased continuously while the flux decreased continuously during the concentration process. Degradation index (DI) changes of concentrated pigment solution were insignificant during the whole concentration process which is indicating that the nanofiltration method does not affect color degradation of anthocyanin pigment. For the comparison test, the same pigment extract was concentrated using a rotary vacuum evaporator at temperatures of 40 and $60^{\circ}C$. At both temperatures, pigment content increased in a similar manner during concentration $({\times}5)$. However, DI value at $60^{\circ}C$ increased while that at $40^{\circ}C$ did not change appreciably. Total color difference value changed only slightly by nanofiltration and $40^{\circ}C$ while changed significantly by $60^{\circ}C$. These indicate that a membrane filtration method is more effective in concentrating purple sweet potato pigment extract than a vacuum concentration method by high temperature.

• Korean Journal of Food Science and Technology
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• v.29 no.1
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• pp.9-14
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• 1997

The effect of freezing, thawing and blanching on the change of extractable pigment content of purple sweet potato (PSP) was investigated. Freezing at $-5^{\circ}C$ was more effective than freezing at $-20^{\circ}C\;or\;-40^{\circ}C$, and rapid thawing methods such as microwave heating or hat air blast heating were effective than slow thawing methods such as thawing at $4^{\circ}C\;or\;20^{\circ}C$. Inactivation of enzymes, which cause pigment destruction during thawing, by blanching before freezing was necessary to obtain the highest possible amount of extractable pigment from PSP. Microwave blanching for $3{\sim}4$ min or hot air blanching for $10{\sim}15$ min were effective in extracting pigment from PSP.