Jeonghee Surh

Estimated intakes of isoflavones and coumestrol in Korean population

The dietary intakes and sources of isoflavones and coumestrol were estimated for each age group of Koreans based on data from the Korean Nutrition Survey conducted in 1998. For quantitative data on the levels of isoflavones and coumestrol, our previous study monitoring phytoestrogens in 220 Korean leguminous foodstuffs was employed and the median value for each food was adopted. The total isoflavones and coumestrol intake per capita was estimated as 23.3 mg/day, which constituted 14.2 mg daidzein, 6.7 mg genistein, 0.9 mg glycitein, 1.0 mg formononetin, 0.2 mg biochanin A, and 0.3 mg coumestrol. The top five foods arrowroot, soybean paste, tofu, soybean, and soybean sprout contributed to 88.2% of isoflavone intake, with the corresponding intake from each food being 8.3 mg/day, 4.9 mg/day, 2.6 mg/day, 2.5 mg/day, and 2.0 mg/day, respectively. Starting at age 3–6, the contributions of fermented soy products to the isoflavones intakes were around 30%. Soybean sprout was a major source of coumestrol intake in Koreans. Slight differences in the preference of these foods were observed among the various age groups. As regards the total isoflavone intakes, the highest value was 33.6 mg/day for people age 30–49, followed by age 50–64 (26.4 mg/day), 20–29 (21.0 mg/day), ≥65 (18.8 mg/day), 1–2 (14.5 mg/day), 7–12 (12.4 mg/day), 13–19 (10.1 mg/day), and 3–6 (8.9 mg/day). The intake levels are likely to be exceeded in groups who have preferably consumed high phytoestrogen-containing foods such as soy-protein-based infant formula and arrowroot.

Fatty Acid Composition as a Predictor for the Oxidation Stability of Korean Vegetable Oils with or without Induced Oxidative Stress

This study was designed to investigate whether the fatty acid composition could make a significant contribution to the oxidation stability of vegetable oils marketed in Korea. Ten kinds, 97 items of vegetable oils that were produced in either an industrialized or a traditional way were collected and analyzed for their fatty acid compositions and lipid oxidation products, in the absence or presence of oxidative stress. Peroxidability index (PI) calculations based on the fatty acid composition ranged from 7.10 to 111.87 with the lowest value found in olive oils and the highest in perilla oils. In the absence of induced oxidative stress, malondialdehyde (MDA), the secondary lipid oxidation product, was generated more in the oils with higher PI (r=0.890), while the tendency was not observed when the oils were subjected to an oxidation-accelerating system. In the presence of the oxidative stress, the perilla oils produced in an industrialized manner generated appreciably higher amounts of MDA than those produced in a traditional way, although both types of oils presented similar PIs. The results implicate that the fatty acid compositions could be a predictor for the oxidation stability of the vegetable oils at the early stage of oil oxidation, but not for those at a later stage of oxidation.

Antioxidant and Anti-inflammatory Activities of Butanol Extract of Melaleuca leucadendron L.

Melaleuca leucadendron L. has been used as a tranquilizing, sedating, evil-dispelling and pain-relieving agent. We examined the effects of M. leucadendron L. extracts on oxidative stress and inflammation. M. leucadendron L. was extracted with methanol (MeOH) and then fractionated with chloroform (CHCl3) and butanol (BuOH). Antioxidant activity of the MeOH extract and BuOH fraction were higher than that of both α-tocopherol and butyrated hydroxytoluene (BHT). Total phenol content in the extracts of M. leucadendron L., especially the BuOH fraction, well correlated with the antioxidant activity. The anti-inflammatory activity of BuOH extracts were investigated by lipopolysaccharide (LPS)-induced nitric oxide (NO) and prostaglandin E2 (PGE2) production, and cyclooxygenase-2 (COX-2) expression in RAW 264.7 macrophages. The BuOH fraction significantly inhibited LPS-induced NO and PGE2 production. Furthermore, BuOH extract of M. leucadendron L. inhibited the expression of COX-2 and iNOS protein without an appreciable cytotoxic effect on RAW264.7 cells. The extract of M. leucadendron L. also suppressed the phosphorylation of inhibitor κBα (IκBα) and its degradation associated with nuclear factor-κB (NF-κB) activation. Furthermore, BuOH fraction inhibited LPS-induced NF-κB transcriptional activity in a dose-dependent manner. These results suggested that M. leucadendron L. could be useful as a natural anti-oxidant and anti-inflammatory resource.

Food types and frying frequency affect the lipid oxidation of deep frying oil for the preparation of school meals in Korea

200 soybean oils used in school meals for deep frying were investigated to elucidate factors influencing lipid oxidation in the oils. The mean levels of moisture along with primary and secondary lipid oxidation products were significantly different among the oils used by the six schools. When comparing lipid oxidation products of frying oils used for four different food groups (vegetables, fish, meat or carbohydrate-rich foods), differences were found among them, with the values for the carbohydrate-rich group being the lowest. The vegetable group was higher in the contents of conjugated dienes and trienes, and lower for those of hydroperoxides and malondialdehyde. The mean values of malondialdehyde and p-anisidine value for the fish group were greater than those of the other groups. The levels of conjugated trienes and malondialdehyde increased with the frying frequency. These findings indicate that food types and frequency of frying play a role in determining the oil oxidation in deep fried foods in schools.

Release properties of gel-type W/O/W encapsulation system prepared using enzymatically-modified starch

A gel-based encapsulation system was developed by incorporating W/O/W emulsions and 4-α-glucanotransferase (4αGTase) treated starch capable of thermoreversible gel formation, and its physical and release characteristics were investigated as functions of preparation conditions and temperature. Release properties of the W/O/W gels were affected by stability and encapsulation efficiency (EE) of W/O/W emulsions embedded within. Lower EE caused by longer sonication time increased fast release dye portion, which resulted in higher dye release rate, even though emulsion stability improved at longer sonication time. Lower dye release rate of W/O/W gels prepared with relatively higher W/O volume fractions slightly increased as temperature increased from room temperature to 90 °C. However, samples prepared with relatively lower W/O volume fractions showed higher dye release rate and a larger increase at 90 °C. The 4αGTase-treated starch gel improved W/O/W emulsion stability and thus retarded dye release even at 90 °C.

Improvement of physicochemical properties of cereal based ready-to-eat Sunsik using fermentation with Bionuruk and Bifidobacterium longum

Fermentation of sunsik using bionuruk and Bifidobacterium longum (B. longum) was investigated to enhance product dispersibility in water. Compared with unfermented sunsik, fermented sunsik had a higher soluble solid content, a smaller particle size, and a larger surface area per volume, resulting in a decreased sedimentation rate. Microbial enzymes hydrolyzed insoluble compounds into smaller molecular weight compounds. Fermented sunsik exhibited a much lower viscosity than unfermented sunsik, demonstrating that fermentation decreased the number of large particles that are affected by gravitational separation and/or increased solvation of components. In addition, fermented sunsik had a higher amount of free amino acids and an enhanced oxidative stability under ironascorbate-induced lipid oxidation. Fermentation improved the physicochemical properties of sunsik to allow for production of hydrosol sunsik.

Quality Characteristics of Onions Applied with Methylsulfonylmethane (MSM) during Cultivation

Two types of onions cultivated with different methods of sulfur application (designated as S-1 and S-2) were examined for their physicochemical and sensory properties, and then compared with onions without sulfur application as a control. During cultivation, dietary sulfur methylsulfonylmethane (MSM) was sprayed on the leaves twice starting at 2 months before harvest, with one month intervals for S-1. For S-2, the MSM was applied once onto surface soils before sowing, and then once again on the leaves at 2 months before harvest. Thiosulfinate, a major sulfur-containing compound in onions, increased in the order of control, S-1, and S-2, without noticeable differences in the strength of spicy hot taste and flavor. The S-2 onions demonstrated a total reducing capacity three times higher than control and S-1 did. It indicates that the application of sulfur would positively affect the quality of onions under the condition where sufficient time is given for soil mineralization.Two types of onions cultivated with different methods of sulfur application (designated as S-1 and S-2) were examined for their physicochemical and sensory properties, and then compared with onions without sulfur application as a control. During cultivation, dietary sulfur methylsulfonylmethane (MSM) was sprayed on the leaves twice starting at 2 months before harvest, with one month intervals for S-1. For S-2, the MSM was applied once onto surface soils before sowing, and then once again on the leaves at 2 months before harvest. Thiosulfinate, a major sulfur-containing compound in onions, increased in the order of control, S-1, and S-2, without noticeable differences in the strength of spicy hot taste and flavor. The S-2 onions demonstrated a total reducing capacity three times higher than control and S-1 did. It indicates that the application of sulfur would positively affect the quality of onions under the condition where sufficient time is given for soil mineralization.

Preparation and Characterization of Physicochemical and Sensory Properties of Hwajeon Added with Wild Grape Extract

Wild grape extract (WGE) was added into hwajeon at different concentrations (0, 5, 15, 30, 50% of water). The resulting hwajeon were analyzed for their physicochemical and sensory properties. With increasing concentrations of WGE, the pH of dough and hwajeon decreased, and their degrees brix and color intensity increased, presumably due to the presence of tartaric acid, sugar, and anthocyanin in the WGE. The WGE-enriched hwajeon showed higher hardness, gumminess, and chewiness than control hwajeon, which might have been because the sugar and tartaric acid in the WGE partially inhibited starch gelatinization during heat processing. Nevertheless, all the sensory properties and preference were higher in WGE-enriched hwajeon than controls, which could be partially attributed to the fact of that the WGE-enriched hwajeon retained relatively higher moisture. It is suggested that WGE-enriched hwajeon with high preference could be prepared without loss of hwajeon quality.

Effects of Heat Treatment on the Quality of the Onion Juices Prepared with Sulfur-applied Onions

Onion juices were prepared by various heat treatments (at 105-120 o C for 4.5-5.5 h), from the onions cultivated with increasing numbers of sulfur applications (once for Sulfur-1, four times for Sulfur-4). As heat treatment intensity increased, the onion juices darkened (p<0.001), which adversely affected the sensory preference. In addition, increasing the heating temperature significantly increased the organic acid content of onion juices (p<0.001), and therefore, decreased pH (p<0.001). Heat intensity did not affect the thiosulfinate content of onion juices, suggesting that the rate of decomposition of thiosulfinate into low-molecular weight sulfur derivatives is similar over the temperature range of 105-120 o C. Total flavonoids were higher in onion juices derived from Sulfur-4 than in Sulfur-1 onions, and increased with heat treatment intensity (p<0.001). These results indicated that heat-facilitated conversion of bound forms of flavonoids to their free forms increases the extractability of flavonoids from onions.

Influence of the Number of Sulfur Applications on the Improvement of the Chemical Composition and Quality of Onions

Onions were treated with different amounts of sulfur (S) during cultivation and examined for their physicochemical properties and flavor. Onions cultivated without S application were the control group; the treatment groups were grown in soil that had been pretreated with S and received additional S applications or four times before harvest. As the number of S applications increased, the levels of crude protein, quantified with total nitrogen; ash, approximating total amounts of minerals; and dietary fiber of the onions tended to increase. The mineral compositions also improved, with noticeable increases in the levels of Mg, K, Fe, and Zn. In particular, the reducing capacity of the onions increased appreciably (p<0.05), without increases in the levels of S-containing compounds such as thiosulfinate or S-containing amino acids. Nevertheless, the spicy hot taste and flavor, which is generated mainly from S-containing compounds, were perceived more strongly in the onions that had received more S applications.