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.

The purpose of this study was to examine the microbiological and physicochemical changes on packaged tofu stored at temperatures of 5, 13, 23, and 30oC, and measure the consumable period from the expiry date to ultimately evaluate the microbiological safety on the extension of the consumable period. From the investigation, the pH value of tofu at each storage temperature (5, 13, and 23oC) showed a slight decrease over the storage period, although there was no significant change. The hardness of packaged tofu decreased more rapidly as temperature and storage time increased and the tofu started to show signs of decomposition at the same time. Analysis on the microbial change of tofu at different storage temperature revealed that the number of general bacteria also increased as the temperature increased. It was further found that packaged tofu takes 25 days at 5oC, 7 days at 13oC, and 1 day at 23oC from the expiry date until the general bacteria count is at least at the early decomposition level which is 10oC log CFU/g. However, no coliform bacteria was detected from tofu after storing at 5, 13 and 23oC. When packaged tofu was stored at 5oC, the L value changed significantly after 26 days, whereas the a and b values showed no significant change during the storage period (P>0.05). When storing tofu at 13oC and 23oC the L value decreased after 8 and 3 days, respectively. However, both a and b values increased (P<0.05).

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*).

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.

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.

Pumpkin (Cucurbita moschata Duch.) seed is rich in protein and sulfur-containing amino acids. Tofu is a protein gel made from soybean, which is rich in lysine but lacking in sulfur-containing amino acids. This study was conducted to investigate the use of pumpkin seeds in tofu manufacture and to determine its quality and texture characteristics. Soybean was substituted with pumpkin seed to obtain pumpkin seed tofu at the following ratios: 10%, 30%, 50%, and 70% (P10, P30, P50 and P70). Tofu manufactured only with soybean was used as a control (Con). The higher rate of pumpkin seed substitution significantly decreased the moisture content and yield rate (p<0.05). In contrast, pH value and turbidity were significantly increased with the increase in the amount of pumpkin seed (p<0.05). The L-value (81.74~79.04), a-value (－0.19~－3.89) and b-value (12.40~9.84) of samples significantly decreased with the amount of pumpkin seed (p<0.05). No significant difference in syneresis was found among the samples (p<0.05). The hardness tended to decrease with the increase in the amount of pumpkin seed. The microstructure analysis revealed that the pore size of pumpkin seed tofu was smaller than that of Con. These results suggest that the pumpkin seed protein is a useful ingredient in the manufacture of tofu. Increasing the pumpkin seed substitution levels improves the texture of tofu.

The physicochemical and sensorial properties of fibrous tofu with the addition of different sized defatted soybean flour (DSF) were investigated. Coarse DSF (DSF-150; D50 = 279 μm), fine DSF (DSF-63; D50 = 105 μm), and super-fine DSF (DSF-JM; D50 = 5.0 μm) were prepared via conventional sifting followed by jet-milling with the milling pressure of 7 bars. Tofu was made with the 5% addition of coarse DSF (TDSF-63), fine DSF (TDSF-150), superfine DSF (TDSF-JM), and without DSF (TC). The yields of tofu were slightly decreased as coarse and fine DSF were incorporated while the yield of tofu with super-fine DSF was statistically identical with that of control tofu (p<0.05). Tofu with larger DSF (TDSF-63 and TDSF-150) showed less smoother texture and less pure in color, while tofu with superfine DSF (TDSF-JM) resulted in little changes in physical and organoleptic qualities, which were verified by quantitative descriptive analysis (QDA), texture profile analysis (TPA), and color measurements. Each fibrous tofu samples were prepared by mixing soymilk with 5% of DSF from sifting (150 μm, 63 μm sieve) and jet milling process which mentioned as TDSF-150 (DSF average particle size), TDSF-63 (D50 = 105 μm) and TDSF-JM (D50 = 5 μm), respectively. The fibrous tofus were compared to the normal tofu (TC). TDSF-JM has higher yielded (50.98%) among tofu samples. The moisture content of TC, TDSF-JM, TDSF-150 and TDF-63 were 75.81%, 75.47%, 69.89% and 69.80%, respectively. TDSF-JM and TC were having similar L-a-b index. Texture properties of TDSF-JM were similar with TC. On the other hand, TDSF-150 and TDSF-63 has statistically significant higher hardness value and lower point on springiness and cohesiveness compared with TC. Sensory evaluation with quantitative descriptive analysis (QDA) method shown that hardness, mouth feel and beany flavor intensity were decreased with the decreasing of particle size of DSF.

The objective of this study was to investigate the effects of combinations of tofu paste and non-starch polysaccharides (NSP) on the oil uptake reduction (OTR) of deep-fat fried cake doughnuts. OTR agents were tofu paste (from grinding tofu with deionized water, followed by passage through a 60 mesh sieve), and five neutral and nine anionic NSPs. A control doughnut (without tofu paste or NSP), tofu doughnut (with tofu paste) and NSP-tofu doughnut (with tofu paste and NSP) were prepared. The moisture and total lipid (TL) content, cross-section image, color characteristic, and specific volume were measured. The tofu and NSP-tofu doughnuts exhibited higher moisture and lower TL content than the control. OTR was 10.8% for the tofu doughnut, and between 13.2% and 41.2% for the NSP-tofu doughnut. The highest OTR (41.2%) was found in the NSP-tofu doughnut with a combination of tofu paste and sodium alginate (NaA). The specific volume of the NSP-tofu doughnuts with combinations of tofu paste with NaA (2.5 mL/g), locust bean gum (2.5 mL/g), and κ-carrageenan (2.4 mL/g) was very close to that of the control (2.6 mL/g). Considering the OTR and specific volume of doughnuts, the combination of tofu paste and NaA would be most effective in reducing the oil uptake of doughnuts during deep-fat frying.

This study investigated the effects of the mixing ratio of tofu paste and normal corn starch on the characteristics of gluten-free (GF) muffins. Soft wheat flour for wheat flour-based muffins (control) was replaced with the mixture of tofu paste and normal corn starch (NCS). The mixing ratios of tofu paste and NCS were 1:6.4 (S100), 1:5.1 (S80), 1:3.8 (S60), 1:2.6 (S40), 1:1.3 (S20), and 1:0 (S00), based on their total solid contents. GF muffins of S40- S100 developed the porous, sponge-like structure without crumb collapse. The weight and baking loss did not significantly differ in the control and GF muffins. By decreasing NCS in GF muffin batters, the moisture content, firmness, and crumb redness/yellowness of GF muffins increased, while their volume, specific volume, and crumb lightness decreased. Nevertheless, these characteristics (except for firmness) of S100 were much closer to those of the control. In the preference test, however, S60 (possessing lower attributes than S100 and S80) was most favored among GF muffins, and was very similar in all evaluations (except for appearance) to the control. Overall, the mixture of tofu paste and NCS would be a potential material to replace soft wheat flour in muffins.

The objective of this study is to examine the effects of consumer beliefs regarding three food certifications on their behavioral intention and the behavioral intention biases to purchase (purchasing intention biases) certified agricultural products as predicted by a subjective probability model. The food certifications used for this study are ‘Organic food’, ‘Traceability system of food products,’ and ‘Hazard Analysis Critical Control Point (HACCP)’. Tofu (bean curd) was selected as being representative of agricultural food products, for the purposes of this study. In 2016, we surveyed 243 consumers regarding the strength of their belief regarding their prior beliefs relative to each certification, as well as the strength of their intention to purchase certified tofu based on their belief strengths for this study. The study resulted in the following findings: Firstly, consumers hold more than two different prior beliefs for each of the three certifications included in this study. Consumers’ prior beliefs regarding these certifications have an impact on their consideration as to whether they plan to buy those certified agricultural products. Secondly, consumers try to persuade themselves to ensure that their particular belief about the product’s certification could lead to a purchasing decision regarding that agricultural product

The purpose of this study was to formulate the optimal ratio of tofu ice cream made with crushed tofu and soybean milk. Also, to compare characteristics of tofu ice cream and soybean ice cream. Mix viscosity, overrun and melting down are measured as characteristics of ice cream. The optimal mixing ratio of tofu ice cream was determined by response surface methodology based on overall quality. As a result of optimization, tofu ice cream was made with 65.90% tofu cream (9% solid contents), 4.35% whipping cream, 14.35% canola oil, 15.00% sugar, 0.2% emulsifier and 0.2% guar gum. Soybean ice cream made with three different treated (blanched, steamed, roasted) soybean and each preprocess are treated for 0-20 min. Mix viscosity was enhanced preprocessing time increasing. Also, overrun and melting down was decline preprocessing time increased. As a result of comparison of ice cream overall quality, 15 min roasted soybean ice cream was shown the best quality.

Lipoxygenase(LOX) 결여 콩으로 제조한 두부의 급이가 5주간의 고지방-콜레스테롤 식이성 흰쥐에서 간 조직과 분변 지질 함량 및 생체 내 항산화계에 미치는 영향을 평가하였다. 실험군은 정상군, 고지방-콜레스테롤 급이군(HFC), 고지방-콜레스테롤 식이+두부 급이군(태광 두부 급이군, HFC-T1; 개척#1 두부 급이군, HFC-T2; 진양 두부 급이군, HFC-T3)으로 구분하였다. 두부의 콜레스테롤 흡착활성은 개척#1 두부가 타 시료에 비해 유의적으로 높았다. 두부 급이군의 비만지수는 대조군에 비해 통계적인 유의차는 없었으나, 개척#1 두부 급이군(HFC-T2)의 비만지수가 가장 낮았다. 간 조직의 총 지질 함량은 정상군에 비해 대조군이 5.9배 증가되었으며, 개척#1 두부 급이군(HFC-T2)은 대조군에 비해 유의적으로 감소되었다. 대조군에 비해 중성지방 함량은 개척#1, 진양 두부 급이군에서 유의적으로 낮았으며, 총 콜레스테롤 함량은 두부 급이군에서 모두 유의적으로 감소되었다. 두부 급이군의 분변 중 총 지질 함량은 대조군에 비해 유의적으로 증가되었으나, 두부의 종류에 따른 유의차는 없었다. 중성지방 함량은 개척#1 두부 급이군에서 가장 많았고, 총 콜레스테롤의 배출량은 대조군에 비해 두부 급이군에서 다소 증가되었으나, 통계적인 유의차는 없었다. 지질과산화물 함량은 대조군에 비해 HFC-T2 및 HFC-T3군에서 유의적으로 감소되었다. DPPH 라디칼 소거활성은 HFC-T2군에서 정상군과 유사한 수준까지 상승하였다. 간 조직에서 SOD 활성은 대조군에 비해 두부 급이군에서 1.4~2.2배 증가되었으며, HFC-T3군에서 활성이 가장 높았다. Catalase, GSH-Px 및 UDPGT 활성은 개척#1 두부 급이군에서 유의적으로 높았다. LOX 결여 콩으로 제조한 두부의 섭취는 고지방-콜레스테롤 식이에 대해 체내 지질 수준 저하 및 항산화 활성에 긍정적인 효과를 가질 것으로 생각된다.

동부박(CPM)을 첨가하여 제조한 두부의 품질특성의 변화를 측정하였다. CPM 첨가비율이 증가할수록 L값은 대조구 CPM-O과 처리구 CPM-I, CPM-II, CPM-III 간에 유의적인 차이를 나타내지 않았다(p < 0.05). b값은 CPM-III 에서 14.26로 가장 낮았으며, 동부박(CPM) 첨가비율이 증가함에 따라 감소하였다. 텍스쳐 프로파일의 결과는 대조 구 CPM-O와 동부박 첨가 처리구 CPM-I간에는 응집성 (cohesiveness)을 제외한 모든 조사항목에서 유의적인 차이를 나타내지 않았다. 처리구 별 pH는 6.36~6.52로 대조구와 유의적인 차이를 나타내지 않았다. 탁도는 1.46~1.81 범위로 CPM 첨가비율이 증가됨에 따라 증가하였다. 일반 세균수는 CPM-III에서 4.40 × 102CFU/g로 대조구와 유의 적인 차이를 나타내었다. Esterichia coli의 경우, 대조구 CPM-O와 전 처리구에서 검출되지 않았다. 관능적인 분석 결과는 동부박 현탁액 첨가비율이 10%인 처리구 CPM-I 의 경우 대조구와 유의적인 차이를 나타내지 않아, 동부 묵 제조의 부산물을 이용하여 두부제조에 적용할 때는 동부박 첨가 비율이 10%가 적합하다고 판단되었다. Isoflavone glycoside (IG)는 genistin, daidzin, glycitin 순으로 많이 함유되어 있었으며, 동부박(CPM) 첨가 비율이 증가함에 따라 그 함량은 유의적으로 감소하였다. Isoflavone-aglycone (IA)는 IG보다는 함량이 낮았으며, genistein과 daidzein이 glycitein 보다 많이 함유되어 있었으며, 동부박 첨가비율이 증가됨에 따라 유의적으로 감소하였다.

This study was conducted to evaluate the biopreservative potential of a bacteriocin-containing cell-free culture from Lactococcus lactis A164 on tofu. In order to increase the shelf-life of tofu, cell-free culture of A164 was added to tofu coagulant agent for coagulation process. Compared with tofu treated with distilled water, lactic acid, or cell-free culture from Lactobacillus plantarum P23, the tofu treated with a bacteriocin-containing cell-free culture from A164 could significantly suppress the number of total bacteria and extend the shelf-life of tofu. The antibacterial activity of tofu treated with cell-free culture from A164 was further evaluated by using modified agar diffusion method with Weissella paramesenteroides ATCC33313, as an indicator strain. The cell growth of the indicator strain was significantly inhibited by tofu treated with cell-free culture from A164. These results indicate that a bacteriocin-producing strain, L. lactis A164, can be used as a biopresevative for extending the shelf life of fresh-processing foods such as a tofu.

생리적 기능성을 함유하는 두부를 제조하기 위하여 홍삼추출물을 첨가하여 압착 성형 공정 없는 연두부의 형태로 제조하였으며, 홍삼 추출물 첨가 연두부의 저장기간에 따른 항산화 성분 및 항산화 활성 변화를 측정하였다. 홍삼 추출물을 첨가하지 않은 대조군의 polyphenol 화합물의 함량은 605.25 μg/mL이었으며, 홍삼 추출물을 첨가군의 함량은 598.51~681.65 μg/mL이었으며, 홍삼 추출물 함량에 비례하였다. 대조군의 ascorbic acid의 함량은 6.42 mg%이었으며, 홍삼 추출물 첨가군은 5.74~7.67 mg%로 대조군보다는 높은 함량을 나타내었다. 저장기간에 따른 polyphenol 화합물 및 ascorbic acid의 변화를 보면 저장기간 내내 대체적으로 대조군보다는 홍삼 추출물 첨가군이 높은 함량을 보였다. 환원력의 경우, 대조군은 O.D.값이 0.2781로 나타났으며, 홍삼 추출물 첨가군은 O.D.값이 각각 0.3260~0.3477로 대조군에 비하여 높은 값을 나타내어 홍삼 첨가가 항산화 활성이 증가하는 것으로 나타났으며, 저장기간 내내 높은 항산화 활성을 유지하였다. ABTS radical cation decolorization은 대조군은 20.54 AEAC이었으나, 홍삼추출물 첨가군은 20.63~20.86 AEAC로 홍삼 추출물의 첨가농도가 높을수록 높은 값을 나타내어 항산화 활성이 있는 것으로 나타났다.

In this study, the characteristics of soybeans with different cultivation methods depending on their origins and the properties of tofu made from these soybeans were studied. The isoflavone content was higher in the general Korean soybeans compared to the organic American soybeans. There were no significant differences among the Chinese soybean samples, so the cultivar method was considered to have a greater effect on the isoflavone contents rather than the cultivation method. The protein contents were higher in the tofu made from the general Chinese soybeans and the organic Korean soybeans. Furthermore, the tofu made from the organic Chinese soybeans contained the least amount of proteins. Isoflavone contents were not significantly different among the samples. Texture profile analyses consisting of hardness, cohesiveness, adhesiveness, springiness, and gumminess were all shown to be higher in the organic tofu than in general tofu, with the exception of adhesiveness. In sensory evaluation, color and texture were significantly different according to the samples, and the differences were found to be affected more by the origin of soybeans rather than the cultivation methods. According to this study, the physicochemical properties of the soybeans and tofu seemed to be influenced by the cultivation region rather than the methods.