• Title/Summary/Keyword: tofu quality

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Changes in Quality of Expired Tofu During Storage at Different Temperatures (유통기한이 경과된 포장두부의 저장온도에 따른 품질변화)

  • Kim, Su-jin;Kim, Se-Hun;Bang, Woo-Suk
    • Journal of Food Hygiene and Safety
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    • v.37 no.2
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    • pp.80-86
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    • 2022
  • The purpose of this study was to examine the microbiological and physicochemical changes on packaged tofu stored at temperatures of 5, 13, 23, and 30℃, 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 23℃) 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 5℃, 7 days at 13℃, and 1 day at 23℃ from the expiry date until the general bacteria count is at least at the early decomposition level which is 10℃ log CFU/g. However, no coliform bacteria was detected from tofu after storing at 5, 13 and 23℃. When packaged tofu was stored at 5℃, 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 13℃ and 23℃ the L value decreased after 8 and 3 days, respectively. However, both a and b values increased (P<0.05).

Nutritional Evaluation of Tofu Containing Dried Soymilk Residue(DSR) 2. Evaluation of Carbohydrate Quality (건조비지 첨가 두부의 영양적 품질평가 2. 탄수화물의 품질)

  • Kweon, Mi-Na;Ryu, Hong-Soo;Mun, Sook-Im
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.22 no.3
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    • pp.262-265
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    • 1993
  • Dietary fiber content and carbohydrate digestibility of dried soymilk residue (DSR) and tofu containing DSR were evaluated. Insoluble dietary fiber (IDF) content was 37.4 and 49.8% (%, moisture free basis) for common soymilk residue and DSR, respectively. Both soymilk residues contained 12.5% of soluble dietary fiber (SDF, dry basis). Tofu containing DSR, which is partially substituted with DSR corresponding to 10% weight of soybean used, had higher dietary fiber content (30% more for RDF and 45% more for SDF) than tofu manufactured in traditional manner. Carbohydrate digestibility was much lower in all tofu products ranging from 11% to 21%, and there was a negative correlation( r = -0.9243) between carbohydrate digestibility and total dietary fiber content.

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Physicochemical and Consumer Preference Characteristics of Tofu Incorporated with Pine Needle Powder (솔잎 분말을 첨가한 두부의 품질 특성)

  • Son, Byeong Gil;Kim, Hyun Eun;Lee, Jun Ho
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.44 no.2
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    • pp.296-301
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    • 2015
  • The effects of pine needle powder (PNP) on the physicochemical characteristics of tofu were investigated, and consumer acceptance test was conducted. The pH, moisture content, and lightness and yellowness significantly decreased with increasing PNP concentration from 0 to 0.8% (P<0.05). Hardness increased significantly with increasing PNP concentration (P<0.05). Antimicrobial effects of PNP incorporated into tofu were also investigated. Antioxidant activities of control and produced tofu were compared based on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and total polyphenol contents. DPPH radical scavenging activity and total polyphenol contents increased significantly (P<0.05) and were well-correlated. Tofu with 0.2% PNP is recommended (with respect to overall preference score) for taking advantage of the functional properties of PNP without sacrificing consumer acceptability.

Preparation and Characterization of Black Ginseng Tofu (흑삼농축액을 이용한 흑삼두부 제조 및 품질 특성)

  • Kim, Min-Jeong;Kim, Ae-Jung;Shin, Jeong-Hee
    • Journal of the East Asian Society of Dietary Life
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    • v.22 no.1
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    • pp.68-74
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    • 2012
  • This study was performed to process Tofu as an hypolipidemic food using black ginseng. Before processing we performed the ameliorating effect of black ginseng on the serum levels of triglyceride and total cholesterol in diabetic mice (db/db mice). As a result, the diabetic mice, whose diet was supplemented with black ginseng has a reduced level of serum lipid total cholesterol ($124.58{\pm}10.59mg/dL$) compared to non-supplemented diabetic mice, The supplemented mice exhibited a significant decrease (p<0.05) in serum lipid triglycerides ($80.32{\pm}35.40mg/dL$), which provided the efficacy of black ginseng in reducing hyperlipemia, thus indirectly proving the prevention and treatment of obesity. Then we processed Tofu as a hypolipidemic food using 0~8% black ginseng extract. We evaluated the quality characteristic after producing black ginseng Tofu. For color value, as the addition level of color increases, the value of L (lightness) decreased and a (redness), b (yellowness) increased. With increase in black ginseng concentrate additional level increases, the hardness, gumminess, and chewiness values increased (p<0.05), but the springiness and cohesiveness showed no significant differences. In case of sensory evaluation, Tofu with the addition of 2% black ginseng concentrate (BGT2) showed the highest preference overall. To sum up, black ginseng demonstrated pharmacological effects in treating diabetic complications like hyperlipidemia and reducing body deposit fat.

Quality Attributes of Whole Soybean flour Tofu Affected by Coagulant and Theirs Concentration (응고제 종류와 농도에 따른 전지대두분 두부의 품질)

  • Kim, Ju-Young;Kim, Jun-Han;Kim, Jong-Kuk;Moon, Kwang-Deog
    • Korean Journal of Food Science and Technology
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    • v.32 no.2
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    • pp.402-409
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    • 2000
  • To investigate the textural and physical characteristics of WSF(whole soybean flour) tofu affected by coagulant and its concentration, $CaCl_2$, $CaSO_4$, $GDL(glucono-{\delta}\;lactone)$, $MgCl_2$, and some mixed coagulants were used in this study. Yields of WSF tofu coagulated with $CaSO_4$ and GDL were ranged 4.3-4.5(g/g WSF), but common tofu was 2.2-3.0(g/g soybean). As the water addition ratio increased, L and a value were increased while heating time increased, b value increased. L value of WSF tofu was lower and b value was higher than conventional tofu and 4 commercial tofus. Kinds of coagulant and its concentration significantly affected to textural properties of WSF tofu. As the concentration of coagulant increase, the hardness increased in most all coagulants. WSF tofu coagulated with $CaSO_4$ and GDL recorded low hardness and adhesiveness, and high springiness among the used coagulants at the same concentration. As the hardness increased, the gumminess and chewiness increased in most all coagulants. As coagulation temperature and molding pressure increase, hardness also increased. WSF tofu coagulated with 0.3% $CaSO_4+GDL$ was the most similar in the textural properties with conventional tofu and 4 commercial tofus. WSF tofu coagulated with 0.3% of $CaSO_4+GDL$ at $85^{\circ}C$, 10 times water addition, 5min. heating and $25.0g/cm^2$ molding pressure recorded the highest score in the sensory evaluation.

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Evaluation of Physicochemical Properties of Jeungpyun Prepared with Membrane-filtered Tofu Whey Concentrates

  • Joo, Sin-Youn;Choi, Min-Hee;Jung, Jin-Young;Kim, Woo-Jung;Chung, Hai-Jung
    • Food Quality and Culture
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    • v.2 no.1
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    • pp.43-47
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    • 2008
  • This study examined the quality characteristics of Jeungpyun prepared with different additions of nano-filtered (NF) tofu whey concentrates. The initial pH values of the Jeungpyun batters ranged from 5.64 to 5.78, and decreased to 4.77-4.98 after 4 hours of fermentation at $35^{\circ}C$. The volume and specific volume values of the control Jeungpyun were lower than those of Jeungpyun samples prepared with 1%, 2%, and 3% NF powder. The color of the Jeungpyun became increasingly greenish-yellow as the NF powder level increased. Hardness and brittleness decreased with increasing NF powder content, while cohesiveness and springiness were not significantly different. Sensory evaluations revealed that as the level of NF powder increased, takju smell and sourness increased, but no significant differences were observed for sweetness and moistness between the control and NF powder groups. In terms of overall acceptability, the results revealed that Jeungpyun can be prepared with up to 1% NF powder in place of rice powder and be deemed as acceptable as a control Jeungpyun product.

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Microbial Analysis and Safety Evaluation in the Process of Packaged Tofus (포장두부의 가공공정에서 미생물 분석 및 안전성 평가)

  • Wang, Soun-Nam;Choi, Sung-Won;Hur, Nam-Yoon;Baik, Moo-Yeol;Lee, Han-Seung;Kim, Chang-Nam
    • Journal of Life Science
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    • v.19 no.4
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    • pp.486-491
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    • 2009
  • This study was conducted to investigate microbial distribution in the processing steps and to estimate quality index and shelf life of packaged Tofu (soybean curd). Sanitation and safety of Tofu were analysed in aspects of total viable counts (TVCs) and coliforms. Organoleptic deterioration was observed from some packaged Tofu when their TVCs were over $10^6\;CFU/g$. The controlled simply packaged Tofu and sterilized Tofu with TVCs of under $10^5\;CFU/g$ were 32.0% and 86.9% of the total samples, respectively. Also, the controlled simply packaged Tofu and sterilized Tofu with negative coliforms were 12.0% and 83.7% of the total samples, respectively. TVCs and coliforms increased in some processing steps, which include washing and soaking of raw soybeans, and formation and 1st cooling of packaged Tofu. Increases of TVCs and coliforms in the washing and soaking step were due to contamination from the soaking tank and airborne bacteria, whereas increases of TVCs and coliforms in the grinding step were due to contaminations from the grinder, line and reserving tank. TVCs and coliforms increased in the formation and 1st cooling step of packaged Tofu due to contaminations from filter wools, trays, employee's hands, cooling water, formed products and filter wools.

Effect of Surface Treatment with Chitosan on Shelf-life of Sybean Tofu (Chitosan의 표면처리가 두부의 저장성에 미치는 효과)

  • Park La-Young;Kim Seok-Joong;Lee Shin-Ho
    • Food Science and Preservation
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    • v.12 no.6
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    • pp.516-521
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    • 2005
  • Effect of chitosan on shelf life of soybean tofu was investigated. The quality changes of soybean tofu drained after immersion in $0.1\%$ chitosan solution for 1 hr were examined during storage at 10, 20 and $30^{\circ}C$. The number of viable cell of soybean tofu with treated chitosan was lower about 1 log cycle than that of control after 2 days storage at $10^{\circ}C$ and $20^{\circ}C$, although there was no detectable differences at $30^{\circ}C$. pH decrease during storage soybean tofu at $10^{\circ}C$ was begun after 4 days in soybean tofu with treated chitosan, while 3days in control. Hardness of soybean tofu with treated chitosan was maintained higher than that of control over the storage period at $10^{\circ}C,\;20^{\circ}C\;\and\;30^{\circ}C$. Shelf life of soybean tofu with treated chitosan was extended about 1 day at $10^{\circ}C$ compared with control.

Quality and Antioxidant Properties of Tofu Coagulated with 'Tsugaru' Apple (Malus domestica Borkh) Juice (쓰가루 사과즙을 이용한 두부의 품질 및 항산화 특성)

  • Kim, Dong-Ho;Hong, Kyeong-Nam;Lim, Yeo-Kyeong;Cha, Seung-Hyeon;Ryu, Ji-Eun;Cho, Jin-Ho;Kim, Dae-Il;Yoo, Do-Il;Jang, Keum-Il
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.45 no.8
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    • pp.1130-1137
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    • 2016
  • In this study, we investigated the quality, antioxidant properties, and sensory characteristics of tofu coagulated with 'Tsugaru' apple (Malus domestica Borkh) juice. Yield, $^{\circ}Brix$, pH, total acidity, total polyphenol content, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of 'Tsugaru' apple juice were 60%, 10.3, 3.89, 0.51%, 2.26 mg gallic acid equivalent (GAE)/g, $20{\mu}g$ L-ascorbic acid equivalent (AE)/g, and $75{\mu}g$ AE/g, respectively. In case of Tofu coagulated with 20% (w/v) 'Tsugaru' apple juice, yield, $^{\circ}Brix$, pH, total acidity, hardness, chewiness, cohesiveness, total polyphenol content, ABTS radical scavenging activity, and DPPH radical scavenging activity were 165%, 6.23, 0.27%, 513 g, 315, 0.61, 12.04 mg GAE/g, $80.67{\mu}g$ AE/g, and $92.32{\mu}g$ AE/g, respectively. Both the manufacture yield and pH of tofu decreased with increasing amount of 'Tsugaru' apple juice, whereas total acidity increased. Regarding the texture and chromaticity of tofu coagulated with increasing amounts of 'Tsugaru' apple juice, hardness, chewiness, and a- and b-values increased, whereas cohesiveness and L-value both decreased. In terms of antioxidant activities, total polyphenol content and DPPH radical scavenging activity increased, whereas ABTS radical scavenging activity was maintained within a certain range. Finally, concerning the sensory evaluation (taste, color, flavor, and overall preference) of tofu coagulated with 30% (w/w) 'Tsugaru' apple juice showed the highest scores. Taken together, these results support the possible use of 'Tsugaru' apple juice in producing various foods, as addition of juice enhanced quality, antioxidant properties, and sensory characteristics of tofu.

Quality Characteristics of Cuttlefish Inky Tofu Prepared with Various Coagulants (응고제에 따른 오징어 먹물 두부의 품질 특성)

  • Park, Eo-Jin;An, Sang-Hee
    • Journal of the Korean Society of Food Culture
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    • v.21 no.6
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    • pp.653-660
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    • 2006
  • Some quality characteristics of tofu prepared with cuttlefish ink were investigated to study the effects of various of coagulants. Each concentration of coagulant was determined as 0.2% of GDL, 0.3# of $MgCl_2$, 1%^ of $CaCl_2$, 1.5% of $CaSO_4$ and 0.6% D-gluconic acid calcium by pre-experiment. Also, the optimum concentration of added cuttlefish ink was chosen as 3%(diluted in twenty times). The yield of inky tofu prepared with GDL as coagulant was the highest. According to prepared with $MgCl_2$ was the highest. The result of microstructure was examined by SEM, the particles of inky tofu coagulated with GDL and D-gluconic acid calcium were small and uniformity. In overall acceptability of sensory properties, inky tofu coagulated with GDL was the highest in score. In the color of inky tofu, L value and a value were the highest coagulated with GDL, but that coagulated with $CaCl_2$ had the highest b value. In the texture properties of inky tofu, hardness, gumminess and brittleness were the highest coagulated with D-gluconic acid calcium. A positive correlation was observed between the pH of tofu whey and acidity. Sensory properties of roasted nutty flavor, hardness, cohesiveness and springiness were positively correlated with the acceptability.