KR20030012586A - Tofu using chitosan as a coagulant and process for preparation thereof - Google Patents

Abstract

PURPOSE: A bean curd (Tofu) using chitosan as a coagulant agent and a preparation process thereof are provided, therefore an inorganic salt conventionally used as a coagulant agent in preparing Tofu can be replaced, and the prepared bean curd has lower ash content, higher protein content and prolonged shelf life. CONSTITUTION: The process for preparing the bean curd (Tofu) using chitosan as a coagulant agent comprises the steps of: dissolving 1% (w/v) of chitosan having a molecular weight of 28 kDa in a 1% acetic acid solution or a mixed solution of 1% acetic acid and 1% lactic acid to prepare a chitosan solution; and adding the chitosan solution into soybean milk in a volume ratio of 1:8. Alternatively, the bean curd (Tofu) may be prepared by mixing chitosan having a molecular weight of 28 kDa with potassium chloride in a weight ratio of 60:40; and adding 0.3%(w/v) of the chitosan mixture into soybean milk.

Description

Tofu using chitosan as a coagulant and its manufacturing method {Tofu using chitosan as a coagulant and process for preparation

The present invention relates to tofu using chitosan as a coagulant and a method for preparing the same. More specifically, as a coagulant of soy milk, chitosan is dissolved in a mixed solution of 1% acetic acid or 1% acetic acid and 1% lactic acid and added as a coagulant, or mixed with calcium chloride. It relates to a method for preparing tofu by adding to soy milk.

Tofu is a well-digested and nutritious product that has long been consumed as a traditional food in Korea, China, Japan and Southeast Asia. Tofu is generally made from soy milk, which is then crushed and soaked in soy milk. The hot soy milk is coagulated with a coagulant and molded and pressed.

Tofu coagulants commonly used in Korea are calcium sulfate (CaSO ₄ · 2H ₂ O), magnesium chloride (MgCl ₂ · 6H ₂ O), gluconodeltalactone (C ₆ H ₁₀ O ₆ ), calcium chloride (CaCl ₂ 2H ₂ O) and the like are used a single or mixed a lot.

However, tofu has a very short shelf life because of its high moisture content.The shelf life of Korean food industry is 24 hours from April to October, 48 hours from November to March, and 3 days during refrigeration (0 to 10 ℃). Recommended.

On the other hand, chitosan is a natural high-molecular substance deacetylated by treating chitin present in the shell of crustacea such as crab and shrimp with high temperature and strong alkali. (Muzzarelli RAA. Chitin. Oxford, UK 1977., Knorr D. Food Technol 38: 85-97. 1984.). Chitosan has been used as a flocculant in the wastewater treatment of food products, and has attracted attention because it exhibits biological activities such as antibacterial activity, antitumor activity and cholesterol lowering power.

When chitosan with a cation is used as a coagulant in the production of tofu, it can partially or completely replace the inorganic salts currently used in commercial tofu manufacturing processes and can also extend the shelf life of tofu due to the antibacterial activity of chitosan.

As a study using chitosan as a tofu coagulant, a method of manufacturing tofu using chitosan has been registered in Korean Patent Registration No. 10-0205236, and Korean Patent Publication No. 99-016443 discloses healthy tofu containing chitosan and a patent publication. No. 99-0065938 A method for preparing tofu containing echitosan has been published. However, the manufacturing methods of tofu using chitosan had a disadvantage in the functional surface and texture of the tofu because the sour taste was strongly expressed by using high concentration of acetic acid as a solvent of chitosan or not considering the molecular weight of chitosan.

In view of the above points, the present inventors have established the optimum conditions of chitosan molecular weight, chitosan concentration, coagulation temperature, solidification time, and solvent of chitosan in the manufacturing method of tofu using chitosan as a coagulant. The present invention was completed by confirming that the prepared tofu was excellent in the functional and storage properties.

Accordingly, it is an object of the present invention to provide a method for preparing tofu using chitosan as a coagulant.

Another object of the present invention is to provide a tofu prepared by the above method.

The above object of the present invention is a coagulant solution having a chitosan content of 1% (w / v) by dissolving a molecular weight of 28 kDa chitosan in a mixed solution of 1% acetic acid or 1% acetic acid and 1% lactic acid 1: 1 (v / v). Prepared by adding a coagulant solution and soymilk at a ratio of 1: 8 (v / v), or mixing calcium chloride and chitosan at a ratio of 60:40 (w / w), and then adding 0.3% ( Tofu was prepared by adding w / v) and achieved by comparing and evaluating quality and shelf life with tofu made with conventional coagulants.

Figure 1a and Figure 1b is a schematic diagram showing a preferred embodiment of the manufacturing process of tofu using the chitosan of the present invention as a coagulant.

The present invention provides the coagulation force according to various types of chitosan solution, the ratio of chitosan solution and soy milk (CSSM; chitosan solution to soymilk) and the molecular weight of chitosan (chitosan having molecular weight of 1106kDa, 746kDa, 471kDa, 224kDa, 28kDa, and 7kDa). Investigating; Examining sensory quality of the head according to the ratio of chitosan solution type and CSSM; Examining the characteristics (yield, pH, hardness, quantity, turbidity) of tofu and whey according to the concentration of chitosan, coagulation temperature, and coagulation time; Preparing tofu by mixing 1% acetic acid and 1% lactic acid as a solvent of chitosan to improve the texture of tofu and examining its properties (yield, pH, hardness, quantity, turbidity); To a mixture of CaCl ₂ and chitosan to be used as coagulant, CaCl ₂ and different ratio of chitosan: for producing a head in the (100 0, 80:20, 70:30, 60:40 w / w) and characterized step; Comparing the quality and shelf life of the tofu prepared in this step and the general commercial tofu.

Six types of chitosan (1106kDa, 746kDa, 471kDa, 224kDa, 28kDa, 7kDa) with different molecular weights are Kumho Hwaseong (Seoul, Korea; 1106kDa, 28kDa), Chitolife (Seoul, Korea; 746kDa, 7kDa), Primex Ingredients AS (Avaldsnes, Norway; 471 kDa) and Biotech (Mokpo, Korea; 224 kDa).

The chitosan 1106kDa ~ 224kDa is acid-soluble, 28kDa and 7kDa is water-soluble, the chitosan was stored in a plastic bottle at room temperature. Calcium chloride (CaCl ₂ · 2H ₂ O) was used as an inorganic salt as a coagulant, and an antifoaming agent (LS-303 silicone resin) was used as a product of Dow Corning Korea.

In this step, pH measurement of the tofu was carried out by homogenizing 5 g of tofu and 25 mL of ionized water and filtering with a single layer of gauze, and then measured with a pH meter (Mettler Delta 320).

In the step of examining the characteristics of the head, the nitrogen (N) content was measured using an elemental analyzer (EA 1110, CE Instrument, Rodano-Milan, Italy). Protein was calculated as N x 6.25, moisture and ash content was measured according to standard methods (AOAC 1990). Whey turbidity measurements were expressed in NTU (Nephelometric turbidity unit) using a Hach 2100A turbidimeter (Hach, Loveland, Co., USA).

In measuring the hardness and color of the head, hardness (measurement sample size: 3 × 3 × 1 cm) was measured by rheometer (COMPAC-100, Sun Scientific Co., Japan), and the color was measured using Minolta Chroma Meter CR- It measured using 200 (Minolta Cameras, Osaka, Japan).

The sensory evaluation of the tofu was evaluated by the 5-point method, and the sour taste of the tofu (1 point: very weak to 5 points: very strong) and the general acceptability (1 point: very bad to 5 points: very) by 8 sensory test personnel. Good).

In the present invention, all experiments were performed three or six times, and the results are expressed as mean value or mean value ± standard deviation.

Hereinafter, the tofu using the chitosan of the present invention and a manufacturing method thereof will be described in detail for each process according to FIGS. 1A and 1B.

Step 1: Preparation of Coagulant Using Chitosan

The chitosan solution is prepared by dissolving chitosan to 1% (w / v) in a solution containing 1% acetic acid or 1% acetic acid and 1% lactic acid in a 1: 1 ratio. When CaCl ₂ and chitosan are mixed and used as a coagulant, chitosan (28kDa) and CaCl ₂ are dissolved in a small amount of distilled water.

Second step: manufacturing soymilk

In the present invention, the preparation of soy milk is soaked in 100 g of soybeans at room temperature overnight, then drained and rinsed, and then 800 mL of water (a ratio of soybean and water is 1: 8 w / v) and then blender (model 33BL79, New Hartford, CT) was ground at high speed for 2 minutes and the sludge obtained was filtered with four layers of gauze to obtain soymilk.

Third step: tofu production

In the present invention, tofu is prepared by mixing 800 g of soymilk with stirring and mixing with a coagulant solution at 80 ° C., and then leaving it at room temperature for 15 minutes for coagulation. The formed curd is transferred to a stainless steel box (10.5 × 7.5 × 10.0 cm) covered with one layer of gauze and pressed by a brick of about 3.8 kg. Tofu is allowed to stand in running tap water for 30 minutes and then drained for 30 minutes.

The solidification temperature of the tofu is 75 ° C to 85 ° C, preferably 80 ° C, and the solidification time is 10 minutes to 20 minutes, preferably 15 minutes.

Hereinafter, the specific method of the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited only to these Examples.

Example 1 Determination of the Coagulation Force of Six Kinds of Chitosan with Different Molecular Weights

The coagulation powers of six types of chitosan were investigated according to the different types of chitosan solution and the ratio of chitosan solution to soymilk (CSSM). Since chitosan with high molecular weight has high viscosity (particularly, when the molecular weight is dissolved in 1% acetic acid at 1% concentration in 1106 kDa chitosan, the viscosity shows 500 cP or more). Dissolve to 1% concentration. A 0.5% or 1% chitosan solution dissolved in 0.5-3% acetic acid was mixed with 200 mL of soymilk at 80 ° C. and then left at room temperature for 15 minutes for coagulation, followed by visual observation of the formation of curd.

As shown in Table 1, curd formation was affected by chitosan solution type and CSSM ratio and molecular weight of chitosan. Increasing the concentration of acetic acid as a chitosan solvent could significantly reduce the amount of chitosan solution added to soymilk for curd formation. Among the six types of chitosan investigated, the molecular weight 28kDa chitosan showed the best coagulation power in all the chitosan solution types and the CSSM ratio test.

In the above experiments, low molecular weight chitosan was uniformly distributed in soymilk at low viscosity, while high molecular weight chitosan at high viscosity could result in partial coagulation if the chitosan solution was not evenly mixed in soymilk. Therefore, it is preferable to use a low molecular weight chitosan, and when combining the experimental results of Table 1, chitosan having a molecular weight of 28 kDa is most suitable, and the following experiment was performed using chitosan having a molecular weight of 28 kDa.

Determination of the Coagulation Force of Chitosan with Different Molecular Weights According to the Ratio of Chitosan Solution Type and CSSM Chitosan solution type ¹ CSSM Rate ² Molecular weight of chitosan (kDa) 1106 746 471 224 28 7 0.5 / 0.5 1: 8 - ³ - - - - - 0.5 / 1.0 1: 8 ++++++ 0.5 / 1.0 1: 9--++++ 1.0 / 1.0 1: 8 ++++++ 1.0 / 1.0 1: 9----++ 1.0 / 1.0 1: 10----+- 1.0 / 2.0 1:10 ++++++ 1.0 / 2.0 1:11 ++++++ 1.0 / 2.0 1:12 ++++++ 1.0 / 2.0 1: 15----+- 1.0 / 2.0 1: 17----+- 1.0 / 3.0 1:11 ++++++ 1.0 / 3.0 1:12 ++++++ 1.0 / 3.0 1:15 ++++++ 1.0 / 3.0 1:17 ++++++ 1.0 / 3.0 1: 20----+- 1.0 / 3.0 1: 25------ ¹ chitosan concentration (%) / acetic acid concentration (%). ² Ratio of chitosan solution and soymilk (CSSM) (v / v). ³ -No coagulation, + Good coagulation.

Example 2 Effect of Chitosan Solution Type and CSSM Ratio on Sensory Quality of Tofu

In Example 1, the higher the concentration of acetic acid can reduce the amount of chitosan solution added to the soymilk to form a curd, and to determine the effect of acetic acid concentration on the tofu texture, Tofu was prepared at the CSSM ratio. When the concentration of acetic acid was used as a solvent of chitosan, the amount of chitosan solution added to the soymilk decreased but the sour taste increased.

When the tofu was prepared with 1% acetic acid as the solvent of chitosan, the aftertaste was slightly sour. However, when the acetic acid concentration was 1% or more, the tofu was given a strong sour taste, and thus it was found to be inadequate for use as a chitosan solvent. Therefore, in the following experiment, 1% acetic acid was used as the solvent of chitosan, and the CSSM ratio was 1: 8.

As shown in Table 2, in the sensory evaluation conducted to evaluate the sour taste of tofu, tofu prepared at a ratio of 1.0 / 1.0 chitosan solution type and 1: 8 CSSM was evaluated as 2.4 points.

Evaluation of Sensory Quality of Tofu According to the Ratio of Chitosan Solution Type and CSSM Chitosan solution type ¹ CSSM Rate ² tofu Sour taste ³ pH 0.5 / 1.0 1: 82.7 ^a 5.62 1.0 / 1.0 1: 82.4 ^a 5.65 1.0 / 2.0 1: 104.7 ^bc 5.31 1.0 / 2.0 1: 124.2 ^b 5.49 1.0 / 3.0 1: 115.0 ^c 5.11 1.0 / 3.0 1: 174.6 ^bc 5.25 ¹ chitosan concentration (%) / acetic acid concentration (%). ² Ratio of chitosan solution and soymilk (CSSM) (v / v). ³ by the eight sensory test agents was evaluated by five-point method. (1: very weak to 5: very strong). ^abc Different letters indicate significant differences (P <0.05).

Example 3: Characteristics of Tofu and Whey According to Chitosan Concentration

To determine the effect of chitosan concentration on the characteristics of tofu and whey, 0%, 0.5%, and 1% chitosan solutions were prepared using 1% acetic acid as a solvent. The characteristics of tofu and whey according to chitosan concentration are shown in Table 3 below.

The concentration of chitosan had little effect on the yield, pH and hardness of tofu as well as turbidity of whey. However, tofu prepared using 0.5% or 1% chitosan as a coagulant was more preferable in terms of tofu because it had less sour taste than tofu prepared using only acetic acid without chitosan as a coagulant. In the following experiments, chitosan at a concentration of 1% was used to give more biological function of chitosan to the tofu.

Characterization of Tofu ¹ and Whey by Chitosan Concentration Property ² % Concentration of chitosan dissolved in acetic acid 0 0.5 1.0 tofu Yield (g) 170 ± 5 ^a 176 ± 8 ^a 178 ± 4 ^a pH5.66 ± 0.11 ^a 5.70 ± 0.08 ^a 5.65 ± 0.04 ^a Hardness (× 10 ³ dyne / cm ² ) 755 ± 54 ^a 761 ± 47 ^a 759 ± 58 ^a Whey Volume (mL) 586 ± 16 ^a 590 ± 20 ^a 592 ± 18 ^a Turbidity (NTU) ³ 45 ± 4 ^a 36 ± 11 ^a 40 ± 5 ^{a 1} tofu was prepared with 800 mL soymilk at a CSSM ratio of 1: 8 (v / v). ^{The 2} numbers represent the mean ± standard deviation of the 3 replicates, and the same letter in each line means no significant difference (P> 0.05). ³ Turbidity unit of the turbidimeter.

Example 4 Characteristics of Tofu and Whey According to Solidification Temperature

Tofu was prepared at 75 ° C., 80 ° C. and 85 ° C. in order to measure the effect of the coagulation temperature on the characteristics of tofu. The characteristics of tofu and whey according to the solidification temperature are shown in Table 4. Tofu was prepared by adding 1% chitosan solution dissolved in 1% acetic acid to a ratio of CSSM 1: 8 (v / v) in 800 mL of soymilk.

Experimental results showed that the three different solidification temperatures did not affect the yield and pH of the tofu as well as the amount and turbidity of whey. The hardness of tofu was not different according to the solidification temperature as shown in Table 3. Therefore, a solidification temperature of 80 ° C., which does not affect the quality of tofu even at a temperature difference of ± 5 ° C., was considered preferable.

Characterization of Tofu ¹ and Whey according to Freezing Temperature ² characteristics Temperature (℃) 75 80 85 tofu Yield (g) 187 ± 5 ^a 187 ± 18 ^a 180 ± 6 ^a pH5.62 ± 0.09 ^a 5.65 ± 0.08 ^a 5.60 ± 0.05 ^a Whey Volume (mL) 579 ± 35 ^a 586 ± 12 ^a 605 ± 13 ^a Turbidity (NTU) ³ 21 ± 4 ^a 21 ± 1 ^a 23 ± 3 ^{a 1} tofu was prepared with 800 mL soymilk at a CSSM ratio of 1: 8 (v / v). Chitosan solutions were prepared at a concentration of 1% (w / v) in 1% acetic acid. ² Values represent the mean ± standard deviation of the 3 replicates, meaning that the same letter in each line has no significant difference (P > 0.05). ³ Turbidity unit of the turbidimeter.

Example 5 Characteristics of Tofu and Whey According to Solidification Time

Tofu was prepared in 10 minutes, 15 minutes and 20 minutes to determine the effect of the solidification time on the characteristics of tofu. The characteristics of tofu and whey according to the solidification time are shown in Table 5, and it was found that the solidification time did not affect the characteristics of tofu and whey. The hardness of the tofu was not different according to the solidification time as shown in Table 3. Therefore, even if the difference in the coagulation time of ± 5 minutes, the coagulation time of 15 minutes, which does not affect the quality of the tofu, was considered desirable.

As described above, the optimum conditions for preparing tofu from the results of Table 1 to Table 5 include chitosan and chitosan solution type having a molecular weight of 28 kDa; 1% chitosan / 1% acetic acid, the ratio of chitosan solution to soymilk is 1: 8, the coagulation temperature is 80 ° C., and the coagulation time is 15 minutes.

In the present invention, 169 g to 187 g of tofu was produced in 800 mL of soymilk (Tables 3 to 5), and these yields were determined by Lu et al. (J Food Sci 45: 32-34, 1980) and Lee et al. (Korean J Food Sci Technol 22: 116-122, 1990), similar to the yield of tofu prepared using acetic acid as a coagulant, it can be seen that the use of chitosan as a coagulant does not significantly affect the yield.

Characterization of Tofu ¹ and Whey according to Coagulation Time Property ² Minutes 10 15 20 tofu Yield (g) 169 ± 8 ^a 171 ± 9 ^a 172 ± 3 ^a pH 5.67 ± 0.04 ^a 5.64 ± 0.07 ^a 5.70 ± 0.03 ^a Whey Volume (mL) 597 ± 16 ^a 592 ± 18 ^a 613 ± 5 ^a Turbidity (NTU) ³ 29 ± 2 ^a 27 ± 1 ^a 32 ± 4 ^{a 1} tofu was prepared with 800 mL soymilk at a CSSM ratio of 1: 8 (v / v). Chitosan solutions were prepared at a concentration of 1% (w / v) in 1% acetic acid. ² Values represent the mean ± standard deviation of the 3 replicates, meaning that the same letter in each line has no significant difference (P > 0.05). ³ Turbidity unit of the turbidimeter.

Example 6 Characterization of Tofu and Whey when Acetic Acid and Lactic Acid Mixtures were Used as Chitosan Solvents

In order to further improve the quality of tofu, a mixture of 1% acetic acid and 1% lactic acid was used as a solvent of chitosan. 1% acetic acid and 1% lactic acid are mixed at a ratio of 100: 0, 75:25, 50:50, 25:75, 0: 100, and the chitosan is dissolved in each solution so that the content of chitosan is 1%. Used as.

As shown in Table 6, when tofu was prepared using only lactic acid (0: 100), the yield was higher and the amount of whey was lower than that of tofu prepared using acetic acid only (100: 0). The turbidity of whey) was high. Tofu made with a mixture of acetic acid and lactic acid at a ratio of 75:25 or 50:50 was similar in yield and whey amount compared to tofu prepared using lactic acid only, but the whey content was low. As the ratio of lactic acid increased, the pH of tofu increased from 5.65 to 6.13 without affecting hardness. In the sensory test, tofu prepared with a 50:50 ratio of acetic acid and lactic acid was evaluated best in overall preference without sour taste.

As mentioned above, lactic acid in turbidity of whey is about twice as turbid as acetic acid. Acetic acid has a faster coagulation rate and is more effective as a coagulant than lactic acid because clear whey separation occurs at an early stage. On the other hand, lactic acid has a higher yield and less sourness than tofu prepared using acetic acid, but the taste of tofu is slightly lower. Therefore, it is preferable to use a 50:50 mixture of acetic acid and lactic acid as the solvent of chitosan as the solvent of chitosan, because it can take advantages of acetic acid and lactic acid.

Characterization of Tofu ¹ and Whey Using 1% Acetic Acid and 1% Lactic Acid as Chitosan Solvent Property ² Mixing ratio of 1% acetic acid and 1% lactic acid (%, v / v) 100: 0 75:25 50:50 25:75 0: 100 tofu Yield (g) 178 ± 4 ^ab` 182 ± 5 ^abc 194 ± 10 ^bc 179 ± 5 ^ab 198 ± 12 ^c pH 5.65 ± 0.04 ^a 5.82 ± 0.04 ^b 6.00 ± 0.05 ^c 6.08 ± 0.07 ^cd 6.13 ± 0.03 ^d Hardness 759 ± 48 ^a 726 ± 34 ^a 749 ± 31 ^a 735 ± 47 ^a 769 ± 55 ^a (× 10 ³ dyne / cm ² ) Whey Volume (mL) 609 ± 10 ^c 582 ± 17 ^abc 563 ± 37 ^ab 597 ± 16 ^bc 549 ± 22 ^a Turbidity (NTU) ³ 40 ± 5 ^a 39 ± 7 ^a 42 ± 8 ^a 56 ± 13 ^a 87 ± 10 ^{b 1} tofu was prepared with 800 mL soymilk at a CSSM ratio of 1: 8 (v / v) (v / v). Chitosan solution was used to prepare a concentration of 1% (w / v) in 1% organic acid. ^{The 2} values represent the mean ± standard deviation of the 3 replicates, which means that there is a significant difference between the different characters in each line (P <0.05). ³ Turbidity unit of the turbidimeter.

Example 7: Calcium Chloride (CaCl ₂ ) And Characterization of Tofu and Whey when Mixed with Chitosan

Calcium chloride (CaCl ₂ ) is now widely used as a coagulant in making tofu. By mixing chitosan and CaCl ₂ , it was investigated whether the tofu could be improved than when preparing tofu using CaCl ₂ alone.

CaCl ₂ and chitosan were dissolved in 30 mL of distilled water at the ratio of 100: 0, 80:20, 70:30, 60:40 (%, w / w) and then 0.3% (w / v) concentration in soymilk. Added.

As shown in Table 7, the increase in chitosan concentration from 0% to 30% did not affect the characteristics of tofu and whey except for pH of tofu, but when the concentration of chitosan was 40%, Yield was higher. In sensory evaluation, tofu prepared using a 60:40 mixture of CaCl ₂ and chitosan was best evaluated in overall preference. The results indicate that effective coagulation with a mixture of chitosan and inorganic salts can reduce the use of inorganic salts as coagulants.

Characterization of Tofu ¹ and Whey by Mixing Chitosan and CaCl ₂ Property ² Ratio of CaCl ₂ to chitosan (%, w / w) 100: 0 80:20 70:30 60:40 tofu Yield (g) 180 ± 15 ^a 180 ± 14 ^a 182 ± 9 ^a 198 ± 14 ^b pH 6.34 ± 0.04 ^a 6.33 ± 0.07 ^a 6.51 ± 0.06 ^b 6.47 ± 0.09 ^b Hardness (× 10 ³ dyne / cm ² ) 801 ± 38 ^a 797 ± 25 ^a 802 ± 32 ^a 771 ± 71 ^a Whey Volume (mL) 514 ± 23^a 517 ± 26^a509 ± 9^a493 ± 19^a Turbidity (NTU) ³ 39 ± 4 ^a 38 ± 8 ^a 42 ± 8 ^a 38 ± 7 ^{a 1} tofu was prepared by adding coagulant to 0.3% (w / v) in 800 mL of soymilk. CaCl ₂ and chitosan were dissolved in 30 mL of distilled water prior to addition to soymilk. ² indicates the mean ± standard deviation of the 6 replicates, which means that there is a significant difference between the different characters in each line (P <0.05). ³ Turbidity unit of the turbidimeter.

Example 8 Quality Comparison of Tofu and Commercial Tofu Using Chitosan of the Present Invention as Coagulant

The quality of the tofu A and B of the present invention prepared by the above manufacturing method was compared with that of general commercial tofu (Table 8). Tofu A of the present invention is a tofu prepared by dissolving chitosan in a 1: 1 mixture of 1% acetic acid and 1% lactic acid and then adding a chitosan solution and soy milk at a ratio of 1: 8. Tofu B of the present invention is CaCl ₂ Tofu prepared by mixing with chitosan at 60:40 and adding 0.3% (w / v) to soymilk.

The moisture content of tofu A, B of the present invention (75.1-76.5%) was lower than that of commercial tofu (81.8-8.2%). This difference in the water content of the head was thought to be the main cause of the pressure difference during the compression molding process. When the molding pressure was reduced from 3.8 kg to 1.7 kg in the manufacturing process of the tofu, the water content was 76.5% to 79.5%. It was confirmed that the hardness was lowered from 749 to 637 × 10 ³ dyne / cm 2.

Tofu A (ash content 2.4%, protein content 64.57%) prepared using chitosan is the tofu B (ash content 4.2%, protein content 61.63%) and commercial tofu using coagulant by mixing chitosan and CaCl ₂ Compared with (ash content 4.3-4.4%, protein content 54.76-57.01%), it showed low ash content and high protein content.

Tofu B of the present invention showed slightly lower ash content and higher protein content than commercial tofu.

Color of the head of the present invention L *, a *, b * (L * is bright, a * is red, -a * is green, b * is yellow), as shown in Table 8, higher than commercial tofu The overall acceptability was 3.0-3.4, similar to commercial tofu samples (2.9-3.3).

Quality ¹ Comparison of Tofu Using Chitosan of the Present Invention as a Coagulant and Tofu Sold as a Commodity Tofu ² moisture(%) Ash content (%) protein(%) Hardness ³ Color figures General Symbol ⁴ L * a * b * Tofu of the present invention A 76.5 ^b 2.4 ^a 64.57 ^d 749 ^c 91.11 ^c -1.87 ^bc 15.16 ^a 3.0 ^a B 75.1 ^a 4.2 ^b 61.63 ^c 771 ^c 90.92 ^c -1.89 ^b 16.00 ^a 3.4 ^a Tofu for products C 84.2 ^d 4.3 ^bc 56.89 ^b 341 ^a 89.96 ^b -2.38 ^a 15.54 ^a 3.0 ^a D 81.8 ^c 4.3 ^cd 57.01 ^b 549 ^b 89.10 ^a -1.71 ^c 15.54 ^a 3.3 ^a E 82.1 ^c 4.4 ^d 54.76 ^a 473 ^ab 88.97 ^a -1.94 ^b 15.28 ^a 2.9 ^{a One} value is the average of three replicate experiments. Different characters in each column of ^abcd indicate significant differences (P <0.05). ² Tofu of the present invention was prepared by adding the following coagulant to 800 mL of soymilk. A: A solution of 1% chitosan dissolved in a 1: 1 mixture (v / v) of 1% acetic acid and 1% lactic acid. B: Calcium chloride : Chitosan = 60:40 (%, w / w). CE tofu for general merchandise bought in supermarkets. ³ hardness (× 10 ³ dyne / cm ² ). ^{4 The} sensory test was performed by 8 sensory testers using the 5-point method (1: very poor to 5: very good).

Example 9 Tofu Storage Test

Tofu (10 × 4.5 × 2.5 cm) is placed in a sterile polypropylene tofu container (10.5 × 6.5 × 4 cm, Taebang Co., Seoul, Korea) containing 50 mL of sterile water. Clean Lab, Seoul, Korea], and stored for 7 days at 10 ℃, the turbidity and viable count of the immersion liquid was measured during the storage period. All experiments were repeated six times. The total bacterial count was measured by diluting 1 mL of the dipping solution to 10 ⁸ with 0.1% of peptone water (Difco, Detroit, MI) and dispensing 0.1 mL of the dilution on a plate count agar. After culturing in a time incubator, viable counts were measured. Control A is a tofu prepared using a 1: 1 mixture of 1% acetic acid and 1% lactic acid as a coagulant, and the tofu A of the present invention is prepared by dissolving 1% chitosan in a 1: 1 mixture of 1% acetic acid and 1% lactic acid. One tofu, Control B is tofu prepared using only CaCl ₂ alone, the present invention tofu B represents tofu prepared by mixing CaCl ₂ and chitosan at 60:40.

As shown in Table 9, turbidity and viable cell count of the immersion liquid were measured during storage for 7 days at 10 ° C., and a rapid increase in turbidity was observed in Control B and Tofu B of the present invention compared to Control A and Tofu A of the present invention. Appeared quickly. The number of viable cells of all dipping solutions showed a concentration of 10 ² CFU / mL on day 0 of storage (actually measured 30 minutes after storage). There were no significant differences in viable cell counts until the 2nd day of storage for the four heads. However, as the storage period increased, the viable cell counts of control tofu B and tofu B of the present invention increased rapidly compared to control tofu A and tofu A of the present invention. In particular, the tofu A of the present invention showed that the viable cell count was much lower than that of the control B and the shelf life could be improved by about 3 days.

¹ measure changes in the viable cell count and turbidity of the soaking solution during storage at 10 ℃ Storage period (days) Tofu ² Control A Tofu of the present invention A Control B Tofu B of the present invention Turbidity (NTU) ³ 0 28 ± 5 ^a 23 ± 6 ^a 21 ± 7 ^a 25 ± 5 ^a 1 23 ± 4 ^a 26 ± 5 ^a 20 ± 7 ^a 20 ± 7 ^a 2 25 ± 8 ^a 24 ± 7 ^a 22 ± 3 ^a 23 ± 8 ^a 3 33 ± 11 ^b 23 ± 7 ^a 14 ± 5 ^a 14 ± 6 ^a 4 24 ± 4 ^a 30 ± 5 ^a 23 ± 10 ^a 26 ± 8 ^a 5 27 ± 11 ^ab 21 ± 4 ^a 136 ± 67 ^b 79 ± 44 ^ab 7 89 ± 59 ^a 57 ± 34 ^a 279 ± 133 ^b 320 ± 211 ^b Viable Count (log CFU / mL) 0 2.45 ± 0.36 ^a 2.90 ± 0.50 ^b 2.21 ± 0.17 ^a 2.16 ± 0.12 ^a 1 2.40 ± 0.22 ^a 2.31 ± 0.32 ^a 2.29 ± 0.24 ^a 2.46 ± 0.50 ^a 2 2.91 ± 0.66 ^a 2.62 ± 0.30 ^a 3.06 ± 0.47 ^a 3.36 ± 0.73 ^a 3 4.13 ± 0.86 ^ab 3.59 ± 0.84 ^a 4.97 ± 0.48 ^b 6.43 ± 0.57 ^c 4 5.75 ± 0.31 ^b 4.34 ± 0.55 ^a 7.11 ± 0.42 ^c 6.75 ± 0.28 ^c 5 6.84 ± 0.20 ^b 5.59 ± 0.82 ^a 7.23 ± 0.36 ^b 7.44 ± 0.50 ^b 7 7.12 ± 0.88 ^a 6.52 ± 0.42 ^a 8.43 ± 0.38 ^b 8.26 ± 0.17 ^{b The 1V} value represents the mean ± standard deviation of 6 replicate experiments. Different characters on each line of ^abcd indicate a significant difference (P <0.05). ^{2 The} following coagulants were used in the preparation of tofu. Control A: 1: 1 (v / v) mixture of 1% acetic acid and 1% lactic acid; Tofu A: 1: 1 mixture of 1% acetic acid and 1% lactic acid A solution prepared by dissolving chitosan in 1% (w / v); Control B: CaCl ₂ ; Tofu B of the present invention: CaCl ₂ + chitosan (60:40). ³ Turbidity unit of the turbidimeter.

As described above, the present invention has the effect of replacing the inorganic salts used as a coagulant by preparing tofu using chitosan as a coagulant, as described through Examples and Experimental Examples, and has low ash content and high protein content. It has an excellent effect in terms of storage period, which is a very useful invention for the food processing industry.

Claims (3)

A method of preparing tofu by adding chitosan as a coagulant to soymilk, wherein 1% (w / v) of chitosan having a molecular weight of 28 kDa is mixed in a 1: 1 (v / v) mixture of 1% acetic acid or 1% acetic acid and 1% lactic acid solution. Dissolving to make a chitosan solution, and adding the chitosan solution and soymilk in a ratio of 1: 8 (v / v), wherein the chitosan is used as a coagulant. In the method for preparing tofu by adding chitosan as a coagulant to soy milk, chitosan having a molecular weight of 28 kDa is mixed at a ratio of 60:40 (w / w) by weight of calcium chloride and chitosan, and then the coagulant is 0.3% (w) / v) manufacturing method of tofu using chitosan as a coagulant, characterized in that the addition. Tofu using chitosan produced by the method according to claim 1 or 2 as a coagulant.