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Sweet potato Daeyumi starch was dually modified using glycogen branching enzyme (BE) from Streptococcus mutans and amylosucrase (AS) from Neisseria polysaccharea to prepare slowly digestible starch (SDS). Dually modified starches had higher SDS and resistant starch (RS) contents than control starch. The branched chain length distributions of the BE-modified starches indicated an increase in short side-chains [degree of polymerization (DP)≤12] compared with native starch. AS treatment of the BE-modified starches decreased the proportion of short side-chains and increased the proportion of long side-chains (DP≥25) and molecular mass. It also resulted in a B-type X-ray diffraction pattern and an increased relative crystallinity. Regarding thermal properties, the BE-modified starches showed no endothermic peak, whereas the BEAS-modified starches had a broader melting temperature range and lower melting enthalpy compared to native starch. The combined enzymatic treatment resulted in novel glucan polymers with slow digestion properties.

Summary Proteolytic activity, fibrinolytic activity and angiotensin converting enzyme (ACE)-inhibitory activity, volatile compound profile, off-flavour compound and sensory characteristics in soya bean paste made with Bacillus amyloliquefaciens KFCC11574P (KHG19) strain were compared with those in three different commercial soya bean paste samples. The KHG19 strain was isolated from doenjang, a traditional Korean soya bean paste, and the maximum dominance in soya bean paste prepared in this study was 68.8% after 2 months of ageing. Proteolytic and fibrinolytic activities in soya bean paste made with KHG19 strain (KHG19 soya bean paste) were higher than those in commercial soya bean pastes. The maximum proteolytic activity (2.47 cm2) was observed after 3 months of ageing, and the maximum relative fibrinolytic activity (236.98%) was appeared after 2 months of ageing. ACE-inhibitory activity in KHG19 soya bean paste was similar to those in commercial samples. The volatile compound profile of KHG19 soya bean paste was closest to that of cheonggukjang according to the result from principal component analysis. The sensory score for off-flavour character was significantly low in KHG19 soya bean paste (2.9) compare with the score (6.8) for Korean traditional doenjang. KHG19 strain can be used for the production of functional soya bean paste that would be affordable to global consumer.

To provide the basic data to dry vegetate the sweetpotato leaves, the total contents of tannin, flavonoid and polyphenol in the methanol extract from the hot- air dried sweetpotato leaves were analyzed and DPPH radical scavenging activity, ABTS radical scavenging ability, nitrite scavenging ability, and others were comparatively analyzed. The total tannin content was decreased from Shinmi of 10.87 mg/g at 40°C to 7.28 mg/g at 70°C and the total flavonoid was decreased from Hayanmi of 55.37 mg/g at 40°C to 39.63 mg/g at 70°C. That is, the low temperature drying contained more of these substances than in the high temperature drying. The DPPH radical scavenging activity was the highest in Shinmi and Hayanmi of 84.33% and 85.25% at 40°C, and the ABTS radical scavenging ability was a high value of over 80% in the treatment plot at 40°C. The nitrite scavenging ability was highest in Shinmi and Hayanmi of 76.15% and 73.74% at 40°C but low at 70°C. That is, the antioxidant effect of the hot-air dried sweetpotato leaves was high in the sample of 40°C and low in the sample of 70°C. Affected by the drying temperature, the high antioxidant effect is resulting from the little decrease of active ingredient when drying at low temperatures.

The purpose of the present study is to provide preliminary data for turning sweetpotato leaves into dehydrated vegetables. To achieve this goal, we have gone through the process of hot-air drying the leaves of sweetpotato that are usually thrown away and examined the drying speed and rehydration resilience, then made a comparative analysis of the general ingredients, lutein, β-carotene and chromaticity. The drying speed reached the peak at a temperature of 70°C. As for other general ingredients, there was no significant difference according to temperature. The content of lutein, which is a functional ingredient, was large in Shinmi with 171.59 μg/g at a temperature of 40°C; small in Hayanmi with 73.75 μg/g at a temperature of 70°C. The content of β-carotene was large in Shinmi with 379.59 μg/g at a temperature of 40°C; small in Hayanmi with 170.78 μg/g at a temperature of 70°C. The content of functional materials was the largest at a temperature of 40°C, and decreased in the order of temperatures at 50°C, 60°C, and 70°C. As for rehydration stability, rehydration rate in both Shinmi and Hayanmi was the highest at a temperature of 40°C with 233.93% and 223.47% respectively. To summarize, the quality of dried sweet potato leaf was more affected by temperature than by drying time, and low temperature drying resulted in better product value.

Storage root yield of sweetpotato was decreasing owing to continuous sweetpotato cropping, debasement of soil physical properties, increasing incidence of pest and disease. This study was conducted to evaluate the changes in physicochemical properties of the soil owing to subsoiling (subsoiling to 50 cm depth), and the effect on growth and yield of sweetpotato. The subsoiling treatments included subsoiling treated every year for two years, subsoiling in the first year, and no subsoiling control. The soil physical properties measured were bulk density, hardness, porosity, three phase. Bulk density, porosity, soild (%) of three phase were improved by subsoiling in topsoil and subsoil. Main vine length and vine yield in subsoiling soil were higher than those in no subsoiling soil, but those were not significantly different. Yield of marketable storage root in subsoiling soils treated every year for two years and treated in the first year was more increased 17% and 20% than no subsoiling soil, respectively. The number of marketable storage root per plant was also higher in subsoiling soils than no subsoiling soil, but it was not significantly different. Soluble solid contents and total free sugar contents of storage root of sweetpotato were not significantly different among the treatments. These results show that improving soil physical properties by subsoiling could promote high yield of marketable storage root in continuous sweetpotato cropping field.

This study was performed to understand the effect of cultivation periods on the physicochemical characteristics of the starch of five sweetpotato cultivars, cultivated in Muan, Korea. Starch, protein, and ash contents increased with increased cultivation period, whereas amylose content decreased. Rapid viscosity analysis showed that the pasting temperature, peak viscosity, breakdown, setback and final viscosity increased with increased cultivation period. However, trough and final viscosity decreased. Although the onset temperature and peak temperature values increased, the conclusion temperature did not show any consistent patterns by differential scanning calorimetry. X-ray diffraction showed that the starch samples had C-type crystallinity irrespective of the cultivation period and cultivar. The starch granules were dominantly round and oval, or polygonal irrespective the cultivation period. The bigger the particle size was, the longer the cultivation period was.

We investigated out the effect of cultivation region on the physicochemical characteristics of starch in six sweetpotato cultivars. The following sweetpotato cultivars were analyzed: Daeyumi, Shingeonmi, Jinhongmi, Shinyulmi, Yulmi, and Yeonhwangmi. Samples were cultivated in Muan, Iksan, Nonsan, Boryeong and Hamyang. The soil texture was found to be sandy loam in Muan, Iksan, and Boryeong, sandy clay loam in Nonsan, and loam in Hamyang. The starch content of the sweetpotato was higher in Muan than in Hamyang. The amylose content was 22.3-30.9%, and the highest amylose content was found in samples from Iksan. Rapid viscosity analysis showed that the samples from Hamyang had the lowest values of pasting temperature, while samples of the Daeyumi cultivar had the highest values. Thermal analysis with a differential scanning calorimeter showed that the Muan samples had the highest values of onset temperature, maximum peak temperature, and completion temperature, and the samples from Hamyang had the lowest values. There was no difference between the cultivation regions or the cultivar in the X-ray pattern of the starch or its appearance in scanning electron micrographs. Therefore, the results of this study confirm that cultivation region and cultivar play an important role in determining the quality of sweetpotato and the physicochemical characteristics of sweetpotato starch.

Lactic acid bacteria (LAB) were reported to comprise the majority of the bacterial population in mukeunji, a long-fermented kimchi. This current study investigated the probiotic abilities of LAB isolated from mukeunji. Forty bacterial strains from mukeunji were identified by SDS-PAGE gel patterns, which were further tested for acid and bile tolerance. An assessment of the immuneboosting effects of these strains in RAW264.7 cells was also carried out by measurement of secreted proinflammatory cytokines. Heat-killed LAB were also tested for their contribution to cytokine production because certain LAB are not durable in the digestive tract. Immune-boosting strains were further characterized by SDS-PAGE of whole-cell protein and 16S rRNA gene sequencing, resulting in the identification of Lactobacillus plantarum, L. sakei, Weissella cibaria, and Pediococcus parvulus. These data and the fact that mukeunji is highly consumed in Korea, together, highlight the need of detailed epidemiological and animal feeding studies.

This research was performed to find out the root characteristics of sweetpotato (Ipomoea batatas LAM.) cultivars according to the cultivation regions. Total 10 sweetpotato culivars, 6 yellow, 2 purple and 2 orange, were used for experiment. Samples were cultivated in Muan, Iksan, Nonsan, Boryeong and Hamyang. Precipitation and average temperature during the growth period of sweetpotato cultivation were 882~1,682 mm and 16.7~, respectively. Accumulated temperature was 3,122~. Soil texture was found of sandy loam in Muan, Iksan and Boryeong, sandy clay loam in Nonsan, and loam in Hamyang. The yield of root, dry matter content, starch value and soluble solids contents were high in Muan. The length/width ratio was high in Hamyang. The color values of sweetpotatoes were high in Nonsan. The protein content of sweetpotato powder was high in the Iksan, crude fat content and ash content were high in the Hamyang. The results of this study, we could see that root characteristics of sweetpotato in the same cultivars appeared differently depending on the cultivated regions.

Lactic acid bacteria (LAB) in salted Chinese cabbage, the main ingredient of kimchi, were analyzed by culture-dependent sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), followed by sequencing of the 16S rRNA gene and by culture-independent polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), followed by sequencing of the V3 region of the 16S rRNA gene. The results were compared to those of LAB that had previously been found in kimchi.The two identification methods produced distinct overall LAB profiles. The PCR-DGGE method detected a more diverse microflora, including non-LAB strains. The culture-dependent method uniquely detected Weissella sp. and was able to provide the quantitative distribution of LAB in samples. However, Leuconostoc mesenteroides, Lactobacillus curvatus and Leuconostoc carnosum, which had also been reported as the dominant LAB in kimchi in previous studies, were identified by both methods.The two identification methods gave different bacterial profiles, while both methods were sufficient to identify the most prevalent LAB in salted Chinese cabbage samples. The quantitative feature of the culture-dependent identification method would make it preferable for studying and monitoring LAB viability in kimchi at each fermentation stage. The availability of the culture-independent identification method to identify a broader bacterial profile, including non-LAB, would make it a more effective tool for controlling contamination of undesirable bacteria during kimchi fermentation.