Control Tofu Research Articles

Evaluation of the efficacy of rice bran and sesame oil for producing nutritionally-superior quality functional tofu

Paneer prepared from edible-quality de-oiled soy flour is known as tofu. Functional tofu was augmented with specific antioxidants such as oryzanol and lignan obtained from rice bran oil (RBO) and sesame oil (SO), respectively. All the fortified and control tofu were evaluated for physicochemical (proximate composition, oxidative stability, antioxidant activity, penetration, and color property), microbiological, and sensory properties. The total viable count and yeast and mold counts increased slowly in the samples stored at 4 °C in the refrigerator for 9 days. Fortified tofu showed higher oxidative stability and antioxidant activity than the control tofu during storage conditions. Additionally, tartaric acid-coagulated tofu retained its quality attributes, especially taste and overall acceptability, during refrigerated storage. Functional tofu aided in an innovative technological technique for making functional non-dairy products with boosted healthy constituents.

Quality and functional characteristics of tofu prepared rapidly from soybeans dried after soaking in water

In this study, Soybeans dried after soaking (SDSs) were prepared for rapid tofu production, and quality and functional characteristics of SDS-tofu were analyzed. SDS40, SDS50, and SDS60 were prepared by soaking for 12 hr and then drying at 40, 50, and 60℃, respectively. During the soaking process in tofu production, the water absorption rate of SDSs was higher than that of control soybeans. SDS-tofu was prepared by soaking SDSs for 1 hr. Quality, texture, and sensory characteristics were similar among tofu samples. SDS-tofu had a higher aglycone isoflavone content (AIC) than did control tofu. SDS60-tofu had the highest AIC, indicating high nitric oxide inhibitory effect. Antioxidant components, activities and cell viabilities were similar among control tofu and SDS-tofu. Consequently, this study presents the possibility of enhancing efficiency of tofu production process and functionality of tofu by using SDSs because of reduction of the soaking time and the improvement of aglycone isoflavone content. Novelty impact statement Soybeans dried after soaking (SDSs) contained much higher contents of aglycone isoflavones than did general-use soybeans because the former was prepared by drying soybeans at 40–60℃ after they had been completely soaked for a long time, thus allowing endogenous β-glucosidase (optimal temperature, 60℃) to be activated, and in particular, glycitein, which was not detected in general-use soybeans, was detected in the SDSs. The use of SDSs can shorten the moisture reabsorption time because the cross-sectional area for moisture absorption is larger in SDSs than in general-use soybeans, likely as the result of porous structures that form in the soybean as it dries after swelling from being soaked. By manufacturing tofu using SDSs, tofu with enhanced characteristics, can be produced quickly due to improvement of the manufacturing process, namely, the time needed for soaking is shorter, and the resulting tofu has a higher content of aglycone isoflavones from the conversion of isoflavones to aglycone isoflavones.

Effect of whole chia seed flour on gelling properties, microstructure and texture modification of tofu

Effect of whole chia seed flour (WCSF) on the gelation, microstructure, texture, and water-binding ability of tofu was studied. The WCSF with different concentration (1.0, 1.5 and 2.0% w/w) was added in soymilk. Glucono-δ-lactone (GDL) was used as coagulant for tofu making. Results showed that the initial gelling time of soymilk gradually decreased with the increase of WCSF concentration, but it did not affect the gelling rate of soymilk during gelation. The tanδ of chia seed tofu was between 0.154 and 0.166, indicating a weak gel structure. Control tofu showed a continuous and honeycomb-like structure, whereas tofu with 2% (w/w) WCSF had a discontinuous network. Furthermore, the addition of WCSF decreased the texture property and increased the water-binding ability of tofu. The rheological results suggested that the chia seed mucilage might affect the coagulation process of protein aggregates in soymilk due to the phase separation and electrostatic interaction, resulting in the formation of tofu with distinct rheological property, texture, and water-binding ability.

Tailoring Physical and Sensory Properties of Tofu by the Addition of Jet-Milled, Superfine, Defatted Soybean Flour.

The use of defatted soybean flour (DSF) in food as a source of dietary fiber has been limited due to its rough texture and bitter taste. Our previous work indicates that superfine DSF prepared by jet milling could overcome these problems, as it positively affected physical and sensory properties. Therefore, differently sized DSFs were incorporated in tofu, and their impacts on physical and sensory properties were investigated in this study. Coarse DSF (Dv50 = 341.0 µm), fine DSF (Dv50 = 105.3 µm), and superfine DSF (Dv50 = 5.1 µm) were prepared by conventional sifting and jet milling. Tofu was made with a 5% addition of differently sized DSFs and without DSF (control tofu). The quality of tofu was evaluated by scanning electron microscopy, color measurement, texture profile analysis, and quantitative descriptive analysis. The tofu made with coarse and fine DSF showed negative changes in its physical and organoleptic qualities, such as reduced yields, a less pure color, a harder texture, and a rougher mouthfeel. However, the tofu made with superfine DSF showed only minimal changes in its qualities compared to the control. Therefore, superfine DSF is a promising fiber supplement that does not change the physical and sensory properties in the making of high-quality tofu.

Yield and physicochemical properties of low fat tofu prepared using supercritical carbon dioxide treated soy flours with different fat levels.

The consumer demands for low fat foods are increasing to reduce obesity and chronic diseases. Low-fat tofu (LFT) was prepared using soy flours treated with supercritical CO2 (SC-CO2) at pressures of 10, 20, and 30MPa. After SC-CO2 treatment, the residual oil contents of the soy flours were 12.07, 8.12, and 1.64%, respectively, whereas that of the control soy flour was 18.20%. The objective of this study was to investigate the yield and quality characteristics of LFTs, compared to the control tofu. All SC-CO2-treated LFTs had significantly higher protein and moisture contents than the control tofu. The yields (g/100g soy flour) of SC-CO2-treated tofu were 442.69, 507.44, and 535.47g, respectively, at three fat levels, whereas the yield was 385.23g in case of the control tofu. The SC-CO2-treated LFTs had softer textural attributes due to increasing moisture contents. In addition, the LFTs obtained higher sensory scores owing to softer texture and lower beany flavor than control sample. SC-CO2-treated soy flours showed higher solubility in soy milk, leading to higher yield, produced softer texture of tofu, and increased nutritional value with low fat and high protein content.

Physicochemical and Consumer Acceptance of Tofu Supplemented with Licorice Powder.

To develop functionally and nutritionally improved tofu, the effects of partial (0.2~0.8%) replacement with licorice powder (LP) on the quality characteristics of tofu were investigated. The pH and turbidity values decreased upon addition of increasing amounts of LP (P<0.05). The yield of LP-supplemented tofu was higher than that of the control tofu, and it increased as the concentration of LP increased (P<0.05). Substituting 0.6% and above of LP significantly hardened the texture of tofu (P<0.05) while control and 0.2~0.4% samples were not significantly different among them (P> 0.05). Lightness significantly decreased with higher LP content in the formulation (P<0.05), as indicated by visual observation that the color of tofu became darker. Redness and yellowness significantly increased (P<0.05). 2,2-Diphenyl-1-picrylhydrazyl and 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid radical scavenging activities significantly increased (P<0.05) with higher substitution of LP, and they were well correlated. Tofu incorporated with LP (0.2~0.8%) had a better shelf life which was approximately 4.32~26.64 h longer than the control tofu at the elevated temperature of 15°C. Finally, consumer acceptance test revealed that supplementation of LP more than 0.4% had an adverse effect on general consumer acceptance. On the basis of the overall observations, tofu samples supplemented with 0.2% (w/w) LP were found to benefit from the functional properties of LP, without compromising consumer acceptance.

HPMC (hydroxypropyl methylcellulose) as a fat replacer improves the physical properties of low-fat tofu.

The effect of the addition of hydroxypropyl methylcellulose (HPMC) on the textural properties of low-fat tofu was investigated. Three fat levels (240, 100 and 30 g kg-1 ) were used to make tofu, which were identified as C (full-fat tofu), L1 and L2. HPMC (5 g kg-1 ) was added to soymilk to prepare control and low-fat tofu, designated as CH, L1H and L2H. Soymilk with a lower fat level had a lower viscosity: 143 (C), 100 (L1) and 42 (L2) cP. The addition of HPMC increased the viscosity of all types of soymilk, particularly in L2H (107 cP). With fat reduction, tofu syneresis increased from 19% (C) to 29% (L2), although syneresis of L2H recovered to 19%, which is similar to high-fat control tofu. Decreased fat resulted in a lower firmness in L2 (0.67 N) compared to control (0.78 N). Firmness increased to 1.08 N in L2H tofu, whereas the firmness of CH tofu was 0.63 N. All types of tofu showed a denser, well-connected and cross-linking structure when HPMC was added, especially in L2H tofu. HPMC improved the texture of the low-fat tofu by creating a harder texture and reducing syneresis. HPMC is an effective fat replacer for lower fat soymilk. © 2017 Society of Chemical Industry.

Changes in quality characteristics of tofu with freezing treatment of soybeans.

The aim of this study was to investigate the influence of length of freezing time (-18°C for 5 or 24 h) on the quality characteristics of tofu. The yield and moisture content of tofu obtained from frozen soybean were lower than control tofu. Tofu made from frozen soybeans showed higher hardness, gumminess and chewiness than the control. Freezing treatment also made the microstructure of the tofu more uniform than the control. However, after 24-h freezing, hardness decreased and the microstructure of tofu appeared to form pores. Sensory evaluation showed that mouth-feel decreased with an increase of freezing time. Among all of tofu frozen at -18°C, 5-h freezing treatment showed the highest overall acceptability. These results indicate that the length of time that soybeans are frozen before making tofu affects the quality of tofu.

Pre-treatment of Soy Slurry with Viscozyme L and the Concentration of Sugars and Isoflavones and the Microstructure of Silken Tofu

Silken tofu which retains soluble solids present in the soymilk was investigated for differences in the microstructure, sugars and isoflavones content from regular silken. Soy slurry treated with Viscozyme L (2.5 mL/L) was incubated for 30 minutes at 55°C. Stachyose was the predominant oligosaccharide in treated tofu, 4.58 g/100 g and 3.30 g/100 g in control tofu, raffinose content was 1.21 and 0.75 g/100 g in treated and control tofu, respectively. Glucose was approximately duplicated in treated tofu (1.66 g/100 g) compared to control (0.74 g/100 g) while fructose content was three times higher (1.09 g/100 g). Comparing isoflavones content, malonyl conjugates were double the amount of the control tofu, with the exception of malonylgenistin, but the total amount of isoflavones was not different. The tofu of the treated slurry showed a fibrous three-dimensional network structure, but with larger protein aggregates and was more tightly connected than the control.

Ultra high pressure homogenized soy flour for tofu making

Using whole soybean for tofu making can effectively reduce the okara waste, increase the utilization of raw material, and lower the production cost. However, the fiber in whole soybean would alter the protein concentration in soymilk and might weaken the structure of tofu. In the current study, UHPH was used for reducing the particle size of soy flour, non-thermally denaturing the soy proteins, and making a high quality tofu. Two soy flour suspension concentrations (15% and 20%) were treated by UHPH with four combinations of pressures and cycles. Glucono-δ-lactone (GDL) was used as coagulant for tofu making. Soy flour suspensions heated at 95 °C for 10 min were used as the control. The result showed that the UHPH treated soy flour suspension had a smaller and more uniform particle size than in the control. Under appropriate pressure and cycles the hardness, gumminess and chewiness of tofu made from soy flour treated with UHPH was similar to the control tofu. The tofu made from 20% soy flour suspension with 150 MPa UHPH for 3 cycles had the lowest expressible water and syneresis. Control tofu showed a particles inlaid, incomplete honeycomb-like network, whereas UHPH tofu had a regular, continuous honeycomb-like structure. The above results indicated that UHPH reduced the particle size of soy flour, denatured the soy proteins, and could produce a favorable tofu with high level of functional components such as fiber.

청양고추 착즙액을 첨가한 두부의 품질 특성

본 연구에서는 청양고추즙을 두유량의 5%, 10%, 15% (v/v)가 되도록 첨가하여 제조한 두부의 품질 특성 변화를 조사하였다. 제조된 두부의 수분 함량은 청양고추즙 첨가량이 증가할수록 감소하는 경향을 보였지만 무첨가 두부에 비해 높았으며, 조단백, 조지방 및 조회분 함량은 청양고추즙 첨가량에 따라 증가하는 경향을 보였다. 두부의 수율은 5% 청양고추즙 첨가 두부에서 대조구에 비해 유의적으로(p＜0.05) 높게 나타났다. 청양고추즙 첨가량이 증가할수록 탁도 및 총산도는 증가하였으며, pH는 감소하는 경향을 보였다. 두부의 색도는 청양고추즙을 첨가하였을 때 L값과 a값은 감소하고 b값은 증가하였다. 청양고추즙 첨가 두부의 견고성, 부착성, 탄력성, 검성, 씹힘성은 첨가량에 따라 증가하는 경향을 보였으나 대조구에 비해 감소하는 것으로 나타났다. 청양고추즙 첨가 두부의 capsaicin, dihydrocapsaicin, 총 폴리페놀 함량과 DPPH 및 ABTS radical 소거활성은 첨가량에 비례하여 각각 1.62∼5.21, 0.35∼1.33, 31.08~42.94 ㎎/100 g 및 4.14~6.26, 10.50~14.91 AEAC로 증가하였다. 두부의 관능검사 결과 점수는 청양고추즙 첨가량이 증가할수록 감소하는 경향을 보였으나, 5% 첨가 두부가 대조구에 비해 유의적인 차이는 없었으나 다소 높은 점수를 받았다. 이상의 결과로부터 두부 제조 시 청양고추즙의 첨가는 두부의 품질 특성은 유지하면서 관능적 특성 및 기능성의 향상을 기대할 수 있으며, 적정 첨가량은 5% 이내가 적합할 것으로 판단된다.

홍삼 추출물을 첨가한 연두부의 저장 중 품질 및 항산화 특성

저장성, 영양성 및 생리적 기능성을 가지는 두부를 제조하기 위하여 생리적 기능성이 널리 알려진 홍삼 추출물을 첨가하여 압착 성형 공정 없는 연두부의 형태로 제조하여 홍삼 추출물 첨가 연두부의 저장기간에 따른 저장성, 이화학적, 항산화 활성 변화 및 관능적 평가를 측정하였다. 홍삼 추출물을 첨가하지 않은 연두부 대조군의 pH 및 산도는 홍삼추출물 첨가 연두부와 큰 차이가 없었으며 저장기간에 따른 변화도 거의 없었다. 또한 일반세균수의 변화에 있어서도 대조군은 저장 10일차부터 약간의 일반세균이 발견되었으나 홍삼 추출물을 첨가하여 제조한 연두부는 대조군에 비하<BR>여 낮은 균수 또는 검출되지 않는 것으로 나타났으며 홍삼추출물의 함량이 높을수록 항균효과가 있는 것으로 나타났다. 연두부의 색도는 명도 및 적색도는 홍삼 추출물 첨가에 따라 약간 감소하였고 황색도는 증가하였다. 연두부의 조직감은 홍삼 추출물 첨가 유무에 크게 관계가 없는 것으로 나타났다. 연두부의 지질과산화 억제능 및 DPPH radical 소거 능은 대조군보다 홍삼 추출물을 첨가하여 제조하였을 때 억제능이 증가하였다. 관능검사 결과에서는 색에 대한 편견 때문에 0.20% 이상의 홍삼 추출물 첨가군에서는 다소 낮은 기호도를 보였으나 0.18% 첨가군까지는 대조군과 큰 차이를 보이지는 않는 것으로 나타났다.

Texture and Storage Stability of Tofu Incorporated with Rhynchosia volubilis

The effects of Rhynchosia volubilis (yakong) incorporation (0%, 10%, 20%, and 30%, w/w of soybeans) on quality and shelf life of tofu were investigated. Moisture content of tofu increased slightly with the increase in the level of yakong incorporation from 10% to 30% and no apparent relationships between yakong incorporation and the yield were found. Turbidity of soybean whey tended to increase with increased level of yakong incorporation where the values of 20% and 30% samples were significantly different from those of control and 10% sample (p＜0.05). The different levels of yakong incorporation were found to have significant influence (p＜0.05) on all the color characteristics of tofu. Tofu texture varied with the level of yakong incorporation in consistent pattern; however, there was no significant difference (p＞0.05) in most cases. Tofu incorporated with yakong (10～30%) had a shelf life of above at least 1 day longer than that of the control tofu.

EVALUATION OF MICROBIOLOGICAL, PHYSICOCHEMICAL AND SENSORY QUALITIES OF CHITOSAN TOFU DURING STORAGE

ABSTRACTTofu containing both low and high viscosity chitosan was prepared and changes in the microbiological, physicochemical and sensory properties of the tofu during storage were investigated. The colony forming units of mesophilic and psychrotrophic microorganisms in tofu containing high viscosity chitosan were markedly lower during storage than those in the control tofu as well as the tofu containing low viscosity chitosan. The pH of the tofu samples increased during storage. The L and a values of the tofu, especially the control tofu, increased during storage. In the sensory test, the roasted nutty and beany aromas of the tofu decreased during storage. Instrumental analysis of hardness and chewiness of the tofu decreased during storage. Overall preference for the tofu gradually decreased during storage, but overall preference for the tofu containing high viscosity chitosan scored higher than the other tofu samples.

EFFECTS OF CHITOOLIGOSACCHARIDE ON THE PHYSICOCHEMICAL, TEXTURAL AND SENSORY PROPERTIES OF TOFU

ABSTRACTChitinous polymers have been experimented with for the purpose of shelf‐life extension of foods due to their antimicrobial activity. Food additives, however, may impair the taste, color or texture of foods. Therefore, it is necessary to evaluate the effect of a food additive on foods before it is used. In this study, we investigated how the physicochemical properties, microstructure, textural properties and sensory characteristics of tofu are affected by the addition of chitooligosaccharide during its preparation. The addition of chitooligosaccharide to tofu did not significantly affect its physicochemical properties including moisture content, yield, turbidity and color. The chitooligosaccharide tofu, however, had lower hardness and smaller protein aggregates than the control tofu. The chitooligosaccharide did not influence most sensory attributes of tofu except for imparting a bitter taste.

Evaluation of physico‐chemical characteristics and microstructure of tofu containing high viscosity chitosan

Tofu, containing high viscosity chitosan dissolved in a δ‐gluconolactone solution, was prepared and physico‐chemical properties, microstructure, textural properties and sensory characteristics were investigated. Moisture content and pH of the chitosan tofu were slightly lower than those of the control tofu. The textural properties of tofu such as hardness, cohesiveness, gumminess and chewiness measured by an instrumental method were not significantly changed by the addition of chitosan to tofu. Springiness of chitosan tofu, however, was significantly higher than that of the control tofu. All characteristics except the roasted nutty aroma and yellowness in the sensory evaluation, did not exhibit significant differences between the chitosan tofu and control tofu. Therefore, the quality of tofu was little affected by the addition of the chitosan content employed in this experiment.