Hardness Of Tofu Research Articles

Protein composition and textural properties of inulin-enriched tofu produced by hydrothermal process

Tofu protein composition changes induced by a pilot plant processing method involving hydrothermal cooking, commercial rennet as coagulant and inulin as functional ingredient were assessed. Glycoproteins (γ-, β-conglycinin) were firmly bound to the matrix of the obtained gels. Extractable proteins of inulin-enriched tofu were with mainly basic 7S-globulin, and polypeptides of glycinin. Polypeptides A1,2,4 and B1,2,4 were found in higher concentrations in protein extracts of tofu than other 11S polypeptides. Tofu was characterized by high total (417.6–556.5 g/kg) and extractable soluble (155.3–367.5 g/kg) protein content, good protein extractability (37.2–68.6%), both total protein (52–69%) and soluble protein (50–76%) recovery. Increasing concentrations of inulin proportionally improved tofu hardness (6.23–8.98 N/cm2) contributing to the uniformity of gel microstructures. Inulin played an important role in incorporating β- and γ-conglycinins into the gel matrix and by increasing the concentration of inulin in soymilk before gelation, the content of extractable soluble proteins, protein extractability and soluble protein recovery of produced tofu were also proportionally increased. For all tested sensory attributes the grades were increased with increasing inulin content in the samples. Under the applied production method, protein composition and proportion of inulin had important roles in defining tofu quality.

레드비트 분말 첨가가 두부의 이화학적 및 미생물학적 특성에 미치는 영향

This study aimed to investigate the enhancing effects of a specified amount of red beet (Beta vulgaris L.) powder on the quality of tofu over existing ones. Thereafter, physicochemical characteristics and microbial safety were compared between tofu prepared addition of red beet powder (RBP) at different concentrations (0.5-2%) and tofu without RBP. No significant differences in sample yield were observed (p>0.05) and, the brix degree and lightness of tofu significantly decreased with an increase in the RBP concentration (p<0.05). Texture analysis revealed that incorporation of RBP significantly increased the hardness of tofu (p<0.05), while the cohesiveness, springiness, and chewiness were not significantly altered. Furthermore, total phenolic content and antioxidant activity of RBP-incorporated tofu were significantly greater than those of untreated tofu on the DPPH radical scavenging assay, ABTS radical scavenging assay, and ferric reducing antioxidant power assay (p<0.05). In the case of microbial safety, RBP-incorporated tofu contained significantly fewer aerobic bacteria and yeast during storage than tofu without RBP (p<0.05). These results suggest that RBP incorporation in tofu increasees its functional quality and shelf-life.

Evaluation of the genetic architecture of tofu traits in soybean towards genomics‐assisted breeding

AbstractBreeding soybean (Glycine max [L.] Merr.) cultivars that possess an improved suitability for tofu production is of crucial importance for tofu manufacturers. However, phenotyping of tofu‐related traits is cumbersome, costly and time‐consuming. The objective of this study was, therefore, to investigate the potential of marker‐based approaches to assist selection for tofu quality. Three recombinant inbred line (RIL) populations were evaluated for several tofu‐related traits. We found in each population at maximum one QTL per trait, explaining 10.9%–74.2% of the genetic variation, and no QTL at all for tofu weight and tofu yield. The QTL for soymilk weight, tofu hardness and tofu value was population‐specific and may correspond to QTL controlling the proportion of water‐soluble protein. The results of the QTL mapping illustrated that the tofu traits are of a highly quantitative nature. Results from the genomewide prediction were promising for seed quality traits and soaking traits, but for the tofu traits, the prediction accuracies have to be increased further based on improvements of the phenotyping procedure.

Interactions of protein content and globulin subunit composition of soybean proteins in relation to tofu gel properties

The content and globulin subunit composition of soybean proteins are known to affect tofu quality and food-grade soybeans usually have higher levels of proteins. We studied the tofu quality of soybeans with high (44.8%) or low (39.1%) protein content and with or without the 11S globulin polypeptide, 11SA4. Both protein content and 11SA4 significantly affected tofu gel properties. Soybeans containing more protein had smaller seeds which produced significantly firmer (0.663 vs.0.557 N, p<0.001) tofu gels with creamier colour. The absence of 11SA4 was positively correlated with seed size, tofu hardness and water holding capacity and led to significant changes to the profile of storage protein subunits, which may have contributed to the improvement in tofu gel properties. These results suggest that, in combination with higher protein content, certain protein subunits or their polypeptides can also be targeted in selecting soybeans to further improve soy food quality.

Comparison of Two Small-Scale Processing Methods for Testing Silken Tofu Quality

In developing a simple, reliable, small-scale method to assess silken tofu quality in our soybean improvement program, we examined two processing methods and two coagulants, glucono-δ-lactone (GDL) or nigari (magnesium chloride) in two experiments. Silken tofu was prepared from a commercial soybean variety (expt 1) or seven soybean varieties (V1–V7) which were grown and harvested together (expt 2). The soybeans were soaked overnight (the soak method, with 55 g soybeans) or ground dry first (the dry method, with 60 g soybeans) before processing. The quality of the silken tofu was evaluated and compared among varieties and coagulant-processing methods and their interactions. Moisture and protein content in soymilk and soybean seeds, soymilk yield and protein and solid recovery in soymilk were determined. Compared with the dry method, the soak method allowed faster soymilk extraction, produced soymilk with lower solid and higher protein content and firmer silken tofu with either GDL or nigari as coagulant. Depending on whether nigari or GDL was used as coagulant, the soak method also produced silken tofu with the highest or the lowest water loss which correlated strongly and negatively with tofu hardness (r = −0.93***). Differences were detected among varieties for the key quality attributes. Taken together, the soak method with GDL as coagulant would be the preferred combination to use to assess tofu quality.

Quality Characteristics of Tofu Prepared with Tomatoes and Strawberries

Abstract This research tried to contribute to the diversification and the high quality of tofu products by adding the natural colors from tomatoes and strawberries, thus providing more attractive colors, greater antioxidative activity, and higher palatability The quality characteristics of tofu with 4%, 8%, and 12% strawberry juice and 5%, 10%, and 15% of tomato juice were analyzed. Tofu with tomato juice was fo und to be higher in transference number, and pH showed a significant decrease as the rate of the addition increased, The antioxidan t activity of tofu with strawberry juice is 37.76~52.12%, and tofu with tomato juice is 41.79~51.51%, with tofu with tomato juice is being higher than tofu with strawberry juice in antioxidant status DPPH radical scavenging ability. In chromaticity, the L-value and b-value showed significant decreases as tomato juice was added and when strawberry juice are was added and the values increased. In texture, the hardness of tofu with tomato juice was found to be significantly more solid than tofu with strawberry juice. For the test of springiness, the order was as follows: control group> tomato juice 5%> tomato juice 10%. The result of the organoleptic test of tofu showed, tofu with tomato juice to be significantly brighter in exterior color than tofu with strawberry juice (p<0.001), in for savory flavor, the result shows that tofu with 12% strawberry juice added and that with 10% tomato juice added had better flavor. For the test of beany f lavor, the control group is higher than tofu with strawberry juice and tomato juice, and tofu with 10% of tomato juice added was lowest in beany flavor. In the preference investigation, tofu with 10% tomato jui ce showed the highest preference aft er swallowing and in overall status.Key words: tomato, strawberry, tofu, quality characteristics

Influence of globulin subunit composition of soybean proteins on silken tofu quality. 2. Absence of 11SA4 improves the effect of protein content on tofu hardness

Soybean variety Bunya was developed in Australia to provide a better quality bean for tofu manufacturers. It is null for globulin subunit 11SA4. We investigated the effect of both the Bunya genetic background and the11SA4 subunit on tofu properties using genotypes containing 11SA4, with and without Bunya parentage, or lacking 11SA4 with Bunya parentage. Both Bunya parentage and 11SA4 significantly influenced globulin subunit composition and tofu texture. The group lacking 11SA4 had lower seed protein content, the largest seeds and the highest 7S and the lowest 11S content and produced the hardest tofu. Examination of the impact of 11SA4 null on tofu texture at four protein contents (380–440 g kg–1) over four coagulant (2.0–3.5 g kg–1) levels revealed that the absence of 11SA4 produced firmer tofu across the protein and coagulation levels tested, and this difference was larger than that from higher protein or coagulation levels. These results demonstrated that the absence of the 11SA4 subunit could increase tofu hardness to a level that otherwise could only be achieved with much higher seed protein content.

Assessment of Soy Genotype and Processing Method on Quality of Soybean Tofu

Protein quality in six soybean varieties, based on subunit composition of their protein, was correlated with quality of the produced tofu. Also, protein changes due to a pilot plant processing method involving high temperature/pressure and commercial rennet as coagulant were assessed. In each soybean variety, glycinin (11S) and β-conglycinin (7S) as well as 11S/7S ratio significantly changed from beans to tofu. Between varieties, the 11S/7S protein ratio in seed indicated genotypic influence on tofu yield and gel hardness (r = 0.91 and r = 0.99, respectively; p < 0.05). Also, the 11S/7S ratio correlated with soymilk pH (r = 0.89, p < 0.05), leading to a relationship between soymilk pH with protein recovery and yield of tofu (r = 0.94 and r = 0.91, respectively; p < 0.05). The soybean β'-subunit of 7S protein negatively influenced tofu hardness (r = -0.91, p < 0.05). Seed protein composition and proportion of 7S protein subunits under the applied production method had an important role in defining tofu quality.

국산 장려콩으로 만든 두부의 Mineral, Oxalate 및 Phytate 함량과 품질특성

This study was conducted to investigate the changes of mineral, oxalate and phytate during tofu processing with Korean recommended soybean cultivars. Fourteen cultivars were selected by distribution of calcium, oxalate and phytate contents. Tofu was manufactured and analyzed for quality characteristics, mineral, oxalate and phytate contents. The yield and moisture contents of tofu ranged from 137.77% in Anpyeongkong to 201.91% of Geomjeongkong 4, and 74.42 (Bongeuikong)~80.01% (Hojangkong), respectively. The lightness (L-value), redness (a-value) and yellowness (b-value) ranged from 53.05 (Dawonkong) to 86.16 (Jipumkong 2), -2.04~5.85, and from 3.28 in Geomjeongkong 4 to 16.17 of Cheongjakong, respectively. The hardness of tofu with selected soybean cultivar ranged from 537.36 g (Dongpuktae) to 1696.05 g (Jinpumkong 2). The highest calcium content was 1.488 mg/g in Dawonkong, oxalate and phytate in tofu were high at 0.40 mg/g in Geomjeongkong 4 and 0.41 mg/g in Dawonkong, respectively. The transfer ratios of oxalate and phytate from soybean to tofu were ranged from 0.31~19.70 and 0.41~19.70%, respectively.

Development of functional tofu fortified with garlic and calcium carbonate

The objective of this study was to investigate the effects of calcium lactate as a coagulant and garlic on the quality including color, textural properties and shelf‐life of tofu. Statistical analysis of data was carried out using the SPSS 12.0 program. The yield of garlic tofu was of the order: 0.75% addition of garlic juice〉 1.00% addition of garlic juice〉 0.00% addition of garlic juice〉 0.50% addition of garlic juice〉 0.25% addition of garlic juice. The lightness (L value) was significantly decreased with increasing the concentration of garlic juice addition with increasing the concentration of garlic juice addition (p&lt;0.05). The hardness and cohesiveness were significantly decreased with increasing the concentration of garlic juice addition (p&lt;0.05). However, the hardness of tofu with calcium lactate was significantly lower compared to the other samples using different coagulants (p&lt;0.05). All tofu had initial bacterial concentrations of 9.6×103 CFU/g at 0 day of storage. Tofu prepared with 0.75% and 1.0% addition of garlic juice did not show any changes of viable counts by the second day and the fourth day of storage, respectively. However, viable microbial counts of tofu prepared with 0.0%, 0.25%, 0.50% addition of garlic juice increased more rapidly than those of tofu prepared with 0.75% and 1.0% addition of garlic juice during longer storage periods. These results can further help in process optimization that becomes essential in retaining maximum nutritive value in the tofu especially when the choices of coagulants are plenty.

황금첨가 농도가 두부의 저장성에 미치는 영향

This study was carried out to investigate potential use of Scutellaria bicalensis Georgi (SBG) as an ingredient for extending the shelf life of tofu. The spore of Bacillus sp. KN-4 was isolated from commercial tofu and inoculated to soybean milk to prepare artificially contaminated tofu. The contaminated tofu was stored in the presence of 0.05 and 1% of SBG extract at for 72 hrs. The pH changes of contaminated tofu with SBG extract was slower than those of control during storage. The degree of pH change decreased as the concentration of SBG extract was increased from 0.05% to 0.1%. The change of titratable acidity of the tofu showed the same tendency as pH change during storage. Total cell number of the SBG extract added tofu was lower about log cycle (0.05% SBG extract) or log cycle (0.1% SBG extract) than that of control after storage for 12 hrs at . The color changes of the tofu did not show any difference with and without SBG during storage at . The strength and hardness of the tofu was improved by the addition of SBG extract. Especially, the strength and hardness of tofu in the Presence of 0.1% SBG extract did not change during storage time. The sensory Qualify of SBG extract added tofu was better than control in texture, but not in taste and color. The overall acceptability of the SBG extract added tofu was similar to control.

큰느타리버섯 균사체를 증식시킨 콩을 첨가제조한 두부의 품질특성

큰느타리버섯 균사체를 증식시킨 콩을 첨가하여 버섯의 맛과 성분이 첨가된 기능성 두부를 제조하여 품질특성을 조사하였다. 버섯균사체가 증식된 콩의 성분 중 단백질 및 회분의 함량은 43.23 및 6.34%로 일반 콩의 40.42 및 5.90%에 비하여 높았고 지질과 총당의 함량은 낮았으며 무기질 중 Mg과 Ca의 함량은 높았고 P의 함량은 낮았다. 균사체를 증식시킨 콩을 일반 콩에 대하여 25% 첨가 시까지는 두부제조가 가능하였으나 30% 이상 첨가 시부터는 성형이 제대로 이루어지지 않았다. 균사체를 증식시킨 콩의 첨가비율에 따라 제조한 두부 조직내부의 초미세구조를 촬영한 결과 버섯균사체를 증식시킨 콩의 첨가량이 높은 두부에서는 다당체 간의 응집반응으로 거대분자가 만들어져서 단백질의 응고 조직 간에 공극이 커져있음을 볼 수 있었다. 또한 5～10% 첨가 시 두부의 수율이 약 1.5～3.7% 증가하였다. 두부의 물리적 특성은 균사체를 증식시킨 콩을 20% 첨가 시까지는 첨가량이 클수록 두부의 hardness가 증가하였고 cohesiveness, chewiness, springiness 및 gumminess 등은 5～10% 첨가 시에 무첨가구보다 높은 경향이었다. 관능검사 결과 두부제조 시 버섯균사체를 증식시킨 콩의 첨가비율이 증가할수록 버섯향이 진하다는 결과를 보여주었으나 기호도면에서 5～15% 첨가하였을 때 버섯 향 및 전체적인 맛에 대한 기호도가 무첨가구보다 유의적으로 높게 나타났다.

Stability of soybean seed composition and its effect on soymilk and tofu yield and quality

Soymilk was made from 10 soybean [ Glycine max (L.) Merr.] lines grown at three locations for 2 years, using an 18:1 water/soy protein ratio. Tofu was made with either glucono-delta-lactone (GDL) or calcium sulphate dihydrate (CS). Genotype and year effects were substantially greater than location effects on soybean protein content and seed composition; soymilk and tofu yield, solids levels, and pH; and tofu colour, hardness, and firmness. Genotype by location and genotype by year interaction effects were minor relative to the genotype and year effects. Yield of soymilk, GDL tofu, and CS tofu, which averaged 7.39 l, 6.29 kg, and 6.15 kg per kg soybeans, respectively, were all positively correlated with seed protein and stachyose, and negatively correlated with seed oil, free sugar, sucrose and remainder content. Seed protein was positively correlated with tofu hardness and firmness, while seed oil, free sugar, sucrose, and remainder content were generally negatively correlated with tofu quality parameters. Results of stepwise regression analysis showed that seed protein was the major determinant of soymilk yield and solids content, while soymilk yield was, in turn, the major factor determining GDL tofu yield. Procedures used in making soymilk and tofu play a major role in determining which seed component has a major effect on soymilk and tofu yield and quality.

Processing effect on soybean storage proteins and their relationship with tofu quality.

Tofu was prepared from 13 soybean varieties according to three different methods (bench, pilot, and production methods). Different soybean varieties showed significant differences in storage protein composition (glycinin and beta-conglycinin). The beta-conglycinin (7S) and glycinin (11S) contents were 7.3-9.9 and 14.1-22.9% on the dry matter basis, respectively. The 11S/7S protein ratio varied from 1.64 to 2.51 among the varieties. Glycinin content and 11S/7S protein ratio of the 13 varieties did not change significantly from soy milk to tofu for the production and pilot methods. Soybean 11S/7S protein ratio positively correlated with the 11S/7S ratio of soy milk and tofu (0.57 < or = r < or = 0.83, p < or = 0.01). The correlation coefficient depended on the processing method. Processing method affected 7S and 11S protein contents of tofu and their contribution to tofu hardness, yield, and sensory quality. This may explain in part the contradictory findings of the relationships between storage proteins and tofu quality because processing methods differed in various studies.

DRY TOFU CHARACTERISTICS AFFECTED BY SOYMILK SOLID CONTENT AND COAGULATION TIME1

ABSTRACTThe effects of soymilk solid content (°Brix) and coagulation time on the yield, proximate composition, and textural characteristics of dry tofu were investigated. Soymilk °Brix significantly (p &lt; 0.05) influenced tofu yield, fracturability, hardness, springiness, cohesiveness, and chewiness. Among soymilk °Brix of 7.1, 7.8, 8.4, and 9.2 tested, °Brix 9.2 (9:1 water/bean ratio) produced the lowest yield (201g/100g bean), but the highest fracturability, hardness, cohesiveness, springiness, and chewiness. Coagulation time for 5 min resulted in a significantly lower tofu yield but higher cohesiveness than coagulation for 15 min. The fracturability and hardness of tofu from 9.2 °Brix soymilk coagulated for 5 min were greatest (18.0 and 19.6 kg, respectively). Lower soymilk °Brix and longer coagulation time produced tofu with a significantly higher moisture content. Dry tofu contained approximately 75–78% moisture (wet basis), 55–58% protein (dry basis), and 20–23% fat (dry basis).

Recent progress on biotechnology of soybean proteins and soybean protein food products

Summary Recently it has been recognized that the action of the enzymes contained in soybeans has negative effects on the qualities of soybean protein foods. Based upon these findings, new manufacturing techniques for high quality soybean protein foods have been developed through the control of such enzyme action. For instance, new soybean seeds lacking lipoxygenases have been developed which reduce the production of grassy‐beany flavors. The gel hardness of tofu can also be controlled through the action of the lipoxygenases contained in soybeans. In addition objectionable after‐tastes develop through the hydrolysis of soybean isoflavones by the s‐glucosidases which are found in soybeans. Genetic engineering of soybean proteins made a great progress in improving their functional and nutritional qualities through the modifications of genes encoding for soybean storage proteins. The application of a bioreactor for soy sauce is also described as an example of the progress on the biotechnology.