• Microbiology and Biotechnology Letters
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• v.38 no.4
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• pp.385-390
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• 2010

Bacillus licheniformis fermenting soybean product with highest score in consumer acceptance had been isolated from homemade Cheongkookjang. In order to develop the medium composition, effects of ingredients including nitrogen sources, carbon sources, metal ions and phosphate were examined for protease production of the isolate. Potato starch increased the protease productivity, while glucose repressed it. Yeast extract was the most effective nitrogen source for enzyme production. The calcium was found to increase protease activity slightly while cell growth and enzyme production was completely inhibited by divalent ions such as $Zn^{2+}$, $Cu^{2+}$ and $Co^{2+}$. The maximum protease productivity was reached approximately 800 unit/mL in the optimized medium consisting of potato starch (1.5%), yeast extract (1.5%), $CaCl_2$(0.7%), $K_2HPO_4$(0.03%) and $KH_2PO_4$(0.03%). The protease activity of culture filtrate was gradually decreased after incubation for 28 h.

• Journal of the East Asian Society of Dietary Life
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• v.25 no.3
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• pp.474-483
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• 2015

The textural properties of breads containing midified starches such as pregelatinized waxy corn starch, acetylated potato starch and hydroxypropylated tapioca starch, were investigated to determine the optimum addition level of modified starches. Effects of modified starches on dough properties were investigated through a farinogram and amylogram based on the different additional levels of modified starches (3%, 6%, 9%, 12% and 15% of flour content). Moisture contents and firmness values were measured to investigate the degree of retrogradation at 0 h, 36 h and 72 h after production. The levels of moisture contents were highest upon addition of pregelatinized waxy corn starch followed by acetylated potato starch and lowest upon addition of hydroxypropylated tapioca starch. Overall, higher moisture contents resulted in lower firmness levels. The preference scores by type of modified starch were highest upon addition of 9% hydroxypropylated tapioca starch, 3% pregelatinized waxy corn starch, and 6% acetylated potato starch, respectively. Preference scores were significantly correlated with textural properties such as volume, absorption, stability and weakness (p<0.01).

• Food Science and Biotechnology
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• v.16 no.5
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• pp.783-788
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• 2007

An advantage to the extrusion of raw potatoes is a reduction in the energy input required to process potato products; however, the effects of extrusion on the properties of raw potato have not been studied. The purposes of this study were to develop a workable extrusion process for raw potato and to study the effects of extrusion conditions on the pasting properties of extruded potato products. The peak viscosity, final viscosity, pasting temperature, water solubility index, and water absorption index of pressed and pressed-dried potato extrudates decreased as die exit temperature increased, whereas they did not change as screw speed increased. The peak viscosity, final viscosity, and water solubility of steam-cooked potato products decreased with extrusion processing; however, they did not change with increasing die exit temperature and screw speed. Potato products with different degrees of depolymerization of extruded potato starch, depending on die exit temperature, were produced from raw potatoes.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.198-198
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• 2017

Cultivated varieties of sweet potato were from dry texture type to tender texture type on the basis of consumer preferences. There are many differences in the quantity of sweet potato, starch content, pigment, and sugar content depending on the cultivation season and area, even in the same variety. Therefore, in this study, we attempted to establish optimum time of harvesting through growth characteristics and variation in component like starch, sugar, polyphenol and flavonoid. Four sweet potato varieties were used in this experiment. Among them, Jinhongmi (JHM) & Yulmi (YM) were as dry texture type and Pungwonmi (PWM) & Hogammi (HGM) were as tender texture type. Sweet potatoes were transplanted on 23 May, 2016 and were investigated storage root weight and component contents every 20 days from 60 days to 120 days and surveyed yield at 110, 120, 130 days after transplantation. Result revealed that storage root weight of YM, JHM, and HGM were 30.1, 38.9, 20.8 g respectively in 60 days after transplanting. Storage roots of PWM gerw faster with the weight of 88.2 g. In 120 days after transplanting, storage root weight varied from 88.3 to 118.7 g, HGM was the smallest, and PWM was the largest. Sugar contents of sweet potato ranged from 21.0 to $23.8Brix^{\circ}$ in 60 days after transplanting and from 27.5 to $30.78Brix^{\circ}$ in 120 days after transplanting. In particular, the sugar content of HGM was the highest over $30Brix^{\circ}$ after 80 days. The starch content of dry texture type (YM, JHM) increased from 15.5% to 20.4% and tender texture type (PWM, HGM) increased from 11.0% to 17.3%. Starch content tended to be high in dry type sweet potatoes. The content of polyphenol and flavonoid were highest in 60 days after transplanting and was reduced according to cultivation period. The total yield of PWM was high as 3,154 kg/10a and large storage root of over 250 g accounted for 47.4% in 110 days after transplanting. Storage root (YM, JHM, HGM) of 81~150 g accounted for 34.9% ~ 43.2% in 120 days after transplanting. These are the most marketable. Because consumer in Korea prefers small, round and about 100g size sweet potato. The ratio of large storage root (over 250 g) were increased in all varieties at 130 days after transplanting. Therefore, it is considered appropriate to harvest PWM at 110 days and YM, JHM, HGM at 120 days after transplanting, which planted in late May.

• Food Science and Biotechnology
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• v.17 no.2
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• pp.417-420
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• 2008

Rheological properties of sweet potato starch (SPS)-glucose composites (5%, w/w) at different concentrations (0, 10, 20, and 30%, w/w) of glucose were investigated in steady and dynamic shear. The steady shear rheological properties of SPS-glucose composites were determined from rheological parameters for power law and Casson flow models. At $25^{\circ}C$ all the samples showed a pronounced shear-thinning behaviors (n=0.29-0.37) with high Casson yield stress. In general, the presence of glucose resulted in the decrease in consistence index (K), apparent viscosity (${\eta}_{a,100}$), and yield stress (${\sigma}_{oc}$). Storage (G') and loss (G") moduli increased with an increase in frequency ($\omega$), while complex viscosity (${\eta}*$) decreased. Dynamic moduli (G', G", and ${\eta}*$) of the SPS-glucose composites at higher glucose concentrations (20 and 30%) were higher than those of the control (0% glucose) and also increased with increasing glucose concentration from 10 to 30%. The effect of glucose on steady and dynamic shear rheological properties of the SPS pastes appears to greatly depend on glucose concentration in the range of 10-30%.

• Journal of the East Asian Society of Dietary Life
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• v.24 no.2
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• pp.208-216
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• 2014

The purpose of this study was the optimization of mixing ratio of rice flour, potato starch and soybean flour baking domestic rice cookies with nuts. Response surface methodology, with a central composite design comprising 5 levels and 3 variables, was used to identify the optimal combination of rice flour ($X_1$), potato starch ($X_2$) and soybean flour ($X_3$). The physical properties of 16 samples were analyzed, including color L (p<0.001), color a, color b (p<0.05), spreadability (p<0.05) and hardness (p<0.05). In sensory evaluations, color (p<0.05), flavor, taste (p<0.05), crunch (p<0.05) and overall quality (p<0.05) were differed significantly among the samples. The optimal compositional ratios were 78.90 g rice flour, 18.96 g potato starch, and 15.90 g the soybean flour in 420 g total weight.

• The Korean Journal of Food And Nutrition
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• v.11 no.5
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• pp.561-564
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• 1998

The stabilizatio of amaylolytic enzyme such as $\beta$-amylase of barley, $\beta$-amylase of wheat, $\beta$-amylase of sweet potato, $\alpha$-amylase of Bacillus licheniformis, $\alpha$-amylase of Aspergillus sp. and $\alpha$-glucosidase of Aspergillus awamori was attained by modification with periodate-oxidized soluble starch. The pH stability of modified enzyme was increased at pH 9 for $\beta$-amylase of sweet potato, pH 3~5 and 8~11 for $\beta$-amylase of barley, pH 2~3 and 7~12 for $\beta$-amylase of wheat and pH 6 for $\alpha$-glucosidase of Aspergillus awamori. Thermal stability increased 17.6% for $\alpha$-amylase of Aspergillus sp. at 6$0^{\circ}C$ for 10min, 30% for $\alpha$-amylase of Bacillus licheniformis at 10$0^{\circ}C$ for 5min and 4.5% for $\alpha$-amylase of sweet potato at 6$0^{\circ}C$ for 10min compared with those of native enzymes.

• Journal of Bio-Environment Control
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• v.13 no.2
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• pp.120-123
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• 2004

This study was conducted to investigate the effect of brushing on overgrowth inhibition, growth, yield and starch content in spring-grown potato in the netted house. The plant growth of aerial parts was inhibited with growth stage and brushing duration. Especially, The number of lateral branches decreased greatly with brushing duration. The stem length and stem diameter were not different significantly between brushing and non-brushing on May 6. But the stem length was long in later growth stage but short in longer brushing duration. Chlorophyll content by SPAD increased with growth stage regardless of non-brushing duration and ranged from 30 to 36 mg/$\textrm{cm}^2$. The fresh and dry weight of aerial part and tuber were heavy in longer brushing duration. Starch content was higher in brushing treatment as compared to non-brushing and increased with brushing duration.

• Applied Biological Chemistry
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• v.34 no.1
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• pp.26-31
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• 1991

The physicochemical properties of starches from dry(Suwon 147) and moist type(Hwangmi) sweet potato were investigated and molecular structural properties of their amylopectins were also studied by gel chromatography. Suwon 147 starch bad lower swelling power and higher gelatinization temperature than Hwangmi starch. $\beta-Amylolysis\;limit(%)$ of Suwon 147 and Hwangmi amylopectin were 57.6% and 57.0%, respectively. Average unit chain length of amylopectins were 24.8 glucose units for Suwon 147 and 21.9 for Hwangmi. The elution profiles by Sephadex G-50 after debranched amylopectins of the two starches were similar but DPs of each peak were different.

• The Korean Journal of Food And Nutrition
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• v.11 no.2
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• pp.159-164
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• 1998

pH stability of sweet potato $\beta$-amylase modified with IO4-oxidized soluble starch was increased at pH 3, 5~9 and 11. And optimum pH was 3 and 5 for modification. Thermal stability of the enzyme modified with IO4-oxidized soluble starch was increased at 6$0^{\circ}C$ for 15 min. pH stability of barley $\beta$-amylase modified with IO4-oxidized soluble starch was increased at 3~4 and 8~11, and more increased at pH 3 and 8~11 in the presence of $\alpha$-cyclodextrin.