This study was conducted to compare the quality characteristics of commercial tofu products from the market in Korea. Seventeen types of commercial tofu samples were taken and their physicochemical properties, including soluble solid contents, salinity, pH, total acidity and moisture (total solid contents), were analyzed. The hardness of tofu was negatively correlated with the moisture contents of tofu (r=－0.667**). The commercial tofu showed pH 5.80~6.24, total acidity of 0.016~0.034%, soluble solids of 1.50~3.45 °Brix, salinity of 1.20~2.30%, and moisture content of 79.91~87.57%, respectively. All 17 tofu samples sold in the Korean market were prepared using crude MgCl2 and sea water as a coagulant. The quality characteristics vary depending on the constituent’s of soybeans, and the ratio and amount of coagulants of tofu used. The origin of soybean seeds affected the yellowness of tofu; tofu made from imported soybean showed a higher b value than domestic soybean. These results are expected to be useful for understanding trends in the domestic tofu industry.
In vitro digestibility and protein digestibility corrected amino acid scores (PDCAAS) were investigated to verify the availability of protein in various Rhizopus oligosporus fermented products of domestic soybean (Glycine max L.) cultivars. Danbaegkong (DBK), Daepung (DP), Daewonkong (DWK), Saedanbaek (SDB), Seonyu (SY), and Cheongja4ho (CJ4) were used as raw samples, which were fermented using commercially available Rhizopus oligosporus for 48 h. All cultivars showed increased crude protein content after fermentation. The crude protein content of DBK and SDB was significantly higher than that of the other samples (55.12% in DBK and 54.22% in SDB) (p<0.001). CJ4 had the highest alanine content of 28.88 mg/g (p<0.001), and no significant difference in cysteine content was detected among the cultivars. In most of the fermented samples, the in vitro digestibility was 0.9 or higher, indicating high protein in the fermented samples. However, it is considered that restrictions on digestion are low. In DWK, the amino acid content and PDCAAS, which together indicate protein quality, were 0.917 and 0.855, respectively, confirming that it was the best cultivar to provide the raw material for fermentation. In conclusion Rhizopus oligosporus fermented soybean products can be considered a prospective source of protein with high utility value.
The purpose of this study was to investigate the Maillard reaction–related physicochemical properties of three maize varieties (Kwangpyeongok, Sinhwangok2ho and Gangdaok) after roasting them for different times (0, 15, 25, 40, and 55 minutes). The Maillard reaction is a non-enzymatic browning reaction involving reducing sugars and amino compounds. The content of reducing sugar, the causative agent of the Maillard reaction, decreased as roasting time increased. Gangdaok showed the lowest reducing sugar content of 1.04 mg/g after 55 minutes of roasting. In the elapsed roasting time, chromaticity ‘L’ and ‘b’ values decreased. At 55 minutes of roasting, wherein the Maillard reaction occurred most actively, Gangdaok showed the lowest ‘L’ value of 56.37 and the highest ‘a’ value of 7.60. Gangdaok had superior conditions for inducing the Maillard reaction compared to other varieties, and it is consider that 'flint–type', an endosperm characteristic, may have been the influencing agent. This study detected a total of 52 types of volatile aroma compounds (VACs), of which 28 were produced after roasting. Of the total VACs detected, 2-Formyl-5-methylfuran and 2-Furancarboxaldehyde accounted for 43.8~45.5% and have been confirmed to be the major VACs present in roasted maize. Most of the correlations between the Maillard reaction–related characteristics showed high correlation coefficients.
The effect of 16 cultivars on the quality of the rice porridge was investigated. The ‘Geunnun’ had the highest water absorption rate, but the ‘Segyejinmi’ yield (w/w) was the highest. The total sugar content of the rice porridge was 0.29~8.10%, showing significant variation among the cultivars. High amylose ‘Dodamssal’ and ‘Hwaseonchalbyeo’ glutinous rice displayed rotational viscosities of <20,000 cP. Rotational viscosities for boiled rice cultivars were 30,000~40,000 cP, representing an intermediate level, and the rotational viscosities of ‘Geonyang2’ and ‘Hanareum4’ were over 50,000 cP. These results suggest that the viscosity of rice porridge varies significantly among raw material cultivars. Among other variables affecting the texture profile of rice porridge, there were significant differences in hardness and gumminess among the cultivars. As a raw material, ‘Baekokchal’, a kind of glutinous rice, is known to be whiter than the non-glutinous rice, but after processing to porridge, it showed the lowest L value (71.1). Starch degrading enzyme activity was not significant in most types of rice porridges within 30 or 60 minutes. Therefore, enzymatic starch degradation is thought to be completed within 30 minutes. Among the tested raw materials, ‘Miho’ was 73.5 μg/mg, indicating the best digestibility in vitro.
Saengcheonggukjang, known as Natto in Japan, is a soybean fermented food which is made from steamed soybean, Bacillus and water. Demand of Saengcheonggukjang has increased because it does not have much smell compared to Cheonggukjang. Seven varieties of Saengcheonggukjang were investigated and compared in terms of 100 seed weight, quality characteristics, hard seed rate, and water absorption rate in order to determine the suitability of Korean soybeans. In addition, each characteristic of Saengcheonggukjang was compared. ‘Hoseo’ and ‘Haewon’ showed low 100 seed weight with 8.41 g and 8.11 g, respectively. The water absorption rate was higher in ‘Hoseo’ and ‘Pungwon’ than in Japan varieties. The yield of Saengcheonggukjang was significantly different for each variety. No differences were observed in yield and hardness of Saengcheonggukjang with respect to the varieties and sowing date. ‘Haewon’ showed the highest amino nitrogen content with 575.0 mg%. Viscous material content did not appear to differ between varieties. These results suggested that ‘Hoseo’ and ‘Haewon’ can be considered as suitable candidates for yield and quality of Saengcheonggukjang compared to Japan varieties.
This study was conducted to compare the quality characteristics of firm tofu (coagulant calcium chloride, CaCl2 used) made from eight imported and four domestic soybeans selling in Korean markets. The 100-seed weight of soybeans imported from China and Seonpung cultivated in Korea was the highest at 33.23 g and 32.51 g, respectively. Soybeans imported from the USA (bulk type) showed the lowest at 16.12 g, followed by Ukraine at 16.94 g, and Brazil at 18.51 g. The range of protein and fat in the 12 soybeans was 37.08~41.36% and 18.35~22.17%, respectively. The isoflavone contents were the highest in Daepung2 cultivated in Korea at 3,764.10 μg/g and the lowest in soybeans imported from Brazil at 1,439.85 μg/g. Tofu yield among the samples was in the following order: Seonpung (235.2%), China (232.0%) Daepung2 (228.7%), Daechan (225.7%), and Brazil (208%). Tofu made with soybeans cultivated in Korea (including from China) showed a higher yield compared to that made from soybeans from seven other countries. In the analysis of the correlation of quality factors of tofu, the hardness of the tofu was correlated with 100-seed weight (r=0.676*) and protein content of the soybeans (r=0.837**). Tofu yield was correlated with 100-seed weight (r=0.748**) and protein content of the soybeans (r=0.583*).
This study analyzed the nutritional composition properties of soybeans and the antioxidants, isoflavones, organic acids, and volatile flavor compounds of fermented black soybean products (FBSP). After 24 hours of fermentation, the range of water uptake ratio was 129.00-131.30%, respectively. Total polyphenols content and DPPH and ABTS radical scavenging activity were higher in Cheongja-3 FBSP, flavonoids in Socheongja, while DPPH and ABTS radical scavenging activities were similar in Cheongja-3 FBSP. Isoflavone contents of aglycones (daidzein, genistein, and glycitein) in Cheongja-4 FBSP increased up to 41.97 μg/g. The rank order of primary organic acids was citric acid > fumaric acid > acetic acid > lactic acid, with Cheongja-3 FBSP being the highest. This study identified a total of 34 volatile aroma-compounds, including seven alcohols, seven acids, seven ketones, five phenols, two esters, one furan, four pyrazines, and one miscellaneous. The result could be applied to determine the suitability of cultivars and the quality of the process used for fermented soybean products.
This study was conducted to secure basic information for corn processing by comparing the quality characteristics according to maize cultivars and kernel types (dent, intermediate, flint-like). As a result of analyzing 15 cultivars, a range of measurements were observed: 100-kernel weight, 22.89~35.63 g; moisture, 7.57~8.42%; crude protein, 8.46~11.45%; crude lipids, 3.26~4.83%; Hunter’s L-value, 83.70~86.79; a-value, 2.61~5.49; b-value, 22.01~28.15; and total carotenoids, 6.74~17.07 μg/g. Significance among the cultivars was shown in all quality characteristics (p<0.001), but the significance among the kernel types was found only in crude protein (p<0.005), crude fat (p<0.001), and Hunter’s L-value (p<0.05). The hardness of maize was decreased proportionally to the soaking time for all maize cultivars (p<0.001). In particular, with the same soaking time for different kernel types, the hardness difference was shown in the order of flint-like > dent ≒ intermediate. It was confirmed that the decrease in the hardness of flint-like kernel of close to that of hard-type starch was slowed compare dent and intermediate kernels. So it is expected the some characteristic of kernel types will contribute to the appropriate customized use of the developed cultivars.
The purpose of this study was to compare the quality characteristics of silken tofu products from the commercial market in Korea. Seven types of commercial silken tofu were sampled and their physicochemical properties, including soluble solid contents, salinity, pH, total acidity, moisture contents (total solid contents), crude protein and fat contents were evaluated. The TPA results suggest that the texture of silken tofu was very different from one another according to the type of and the amount of coagulant. The commercial silken tofu showed a range of pH 5.53~6.48, total acidity of 0.12~0.32%, soluble solid contents of 2.62~5.07 °Brix, salinity of 2.28~4.30%, and moisture contents of 87.10~92.24%, respectively. In terms of the coagulant of tofu, besides the GDL (glucono-δ- lactone), other coagulants such as MgCl2 for making ‘silken tofu’ in the Korean tofu market. The quality characteristics differed depending on the constituents of sample and the coagulants of tofu used. These results are expected to be useful in identifying new trends in the domestic silken tofu industry.
The purpose of this study was to evaluate the quality properties of Meju prepared by inoculating two strains of Bacillus amyloliquefaciens HJ5-2, and Aspergillus oryzae PS03. The three soybean varieties that include Daewonkong, Daechan, and Saedanbaek were used in this experiment. The fermentation temperature during the Meju aging varied at 20℃, 30℃, and 40℃, respectively. The physicochemical analysis of the soybeans, showed that the cured protein and fat contents were 34.83~43.49% and 12.91~18.90%, respectively. The pH and total acidity were 6.47~6.93 and 0.11~1.22%, respectively. The change in appearance of the Meju was that the yellow-green mold was well formed on seven days at fermentation temperature of 20℃ and 30℃, but at 40℃, there was minimal mold formation and cracking of the surface. The amino nitrogen content was highest on the Daechan Meju at 621.83 mg% for seven days. The amylase increased as the fermentation period increased in all samples, and the protease increased rapidly until the first day of the fermentation, and then gradually increased thereafter. The total number of bacteria increased or decreased as the fermentation proceeded to 6.66~10.07 log CFU/g. The mold counts increased with increasing fermentation period in the range of 6.38~8.79 log CFU/g.
The purpose of this study was to evaluate the appearance, physicochemical, physical, and fermentation properties of the fermented soybean produced by manufacturing with inoculation the different types of microbial strains. The strains were inoculated by the NSI (natural strains inoculation), and the SSI (selective strain inoculation) were treatments. The appearance showed differences in color, viscous substance, and hardness depending on strains inoculation and fermentation duration. The pH, and total acidity were 6.40~7.26%, and 0.10~0.39% respectively with differences depending on the samples. The moisture content as the fermentation duration increased, the NSI (56.03~57.66%) decreased and the SSI (56.71~58.63%) increased. The physical characteristics of the hardness increased as the fermentation duration increased for the NSI and the SSI decreased. The color values for the L, a, and b values were 47.64~58.56, 7.15~9.08, and 12.41~17.30, respectively. The α-amylase and protease activities of the SSI were the highest among all treatments. The total viable cell counts of the fermented soybean products by strains were 5.02 to 9.77 log CFU/g, and SSI (fermentation, 48 hours) was the highest. The amino-type nitrogen contents of all samples were 301.62~746.97 mg% and the SSI showed the highest content. The amino acid had the highest glutamic acid content.
In this study, the properties of the substances fermented soybean producted by manufacturing with several Aspergillus strains were investigated. The five soybean cultivar that includes miso, jinpung, pyeongwon, cheonga and chamol were used in this experiment. The pH and total acidity were 6.30~6.66%, and 0.27~0.48%, respectively with differences depending on the samples. The color values for L value, a, and b value were 60.28~69.80, 0.64~3.68, and 11.48~31.21, respectively. The amylase activities, protease activities, and amino-type nitrogen of the jinpung samples were the highest among all cultivars. The mold counts the fermented soybean products by cultivars were 6.18~9.14 log CFU/g, and miso was the highest. Free amino acid and organic acid contents were highest in the jinpung and showed different composition depending on each sample. A total of 18 volatile aroma-compounds, including two acids, four alcohols, four ketones, three phenols, one furan, three pyrazines, and one miscellaneous compounds. In conclusion, it is expected that manufacturing A. oligze inoculation fermented soybean products using jinpung cultivar will improve quality.
In this study, the physicochemical traits of soybean (100-seed weight, seed coat rate, protein content, composition, and amino acid content) and the quality of tofu (texture and sensory characteristics) were evaluated in order to determine the features of six varieties (Saedanbaek, Daechan, Daepung2, Seonpung, Miso, Saegeum) in terms of textural and sensory characteristics of tofu. Regardless of cultivar, the order of amino acid composition rate was as follows: Glutamic acid > Aspartic acid > Arginine > Leucine > Lysine. Approximately 50-60% of tofu (dry weight) consisted of protein, and among the cultivars, Tofu made from Saedanbaek showed the highest amount of protein at 59%. It was followed by tofu made from Miso at 54%. The rest contained about 50% protein. According to the result of correlation, crude lipid (-0.933**), crude protein (0.961**), and total phosphorus (0.924**) were strongly correlated with tofu hardness, and such factors could be utilized as an indicator of tofu quality.