Steamed bun rich in gamma-aminobutyric acid and preparation method thereof

Abstract

The invention discloses steamed buns rich in gamma-aminobutyric acid and a preparation method of the steamed buns, belongs to the field of functional food processing, and aims to solve the technical problems that the processing performance of wheat flour can be remarkably degraded when GABA is enriched by adopting a germination process, so that the prepared steamed buns are sticky in mouth feel and rough in structure. The method is characterized by comprising the following steps: conditioning wheat grains until the water content is 10-20%, treating the wheat grains in a damp and hot environment with the temperature of 60-70 DEG C and the relative humidity of 90-98% for 1-6 hours so as to efficiently enrich GABA, and then preparing powder, kneading dough, fermenting and steaming to obtain a finished product. The content of gamma-aminobutyric acid in the steamed buns prepared by the method is not less than 10mg / 100g dry weight, and good eating quality of the steamed buns can be kept at the same time. The invention provides a new way for supplementing gamma-aminobutyric acid through daily staple food.

Description

Technical Field

[0001] This invention relates to the field of functional food processing. More specifically, this invention relates to a steamed bun rich in γ-aminobutyric acid and its preparation method. Background Technology

[0002] Gamma-aminobutyric acid (GABA) is a non-protein free amino acid with important physiological activities, playing a role in regulating blood pressure, blood sugar, and nerve function. Supplementing with GABA through the daily diet has positive implications for improving the health of specific populations. Wheat, as a major grain crop and an important raw material for staple foods, naturally contains glutamic acid, a precursor to GABA synthesis, and is therefore considered a potential carrier for developing GABA-enriched functional foods.

[0003] Currently, the main technical approaches to increasing GABA content in grains include chemical synthesis, microbial fermentation, and phytoaccumulation. Chemical synthesis is strictly limited in the food industry due to the potential introduction of substances with unknown safety profiles. Microbial fermentation involves strain selection and process control, has a long cycle, and may affect product flavor; its ease of industrial production needs improvement. Phytoaccumulation, particularly utilizing seed germination to accumulate GABA, is a widely studied method. This method induces seed germination through soaking, temperature control, and humidity control, activating the activity of endogenous enzyme systems such as glutamate decarboxylase, thereby converting glutamate into GABA.

[0004] However, there are significant limitations to using germination for GABA enrichment. During germination, seeds initiate a series of vigorous metabolic activities to meet their growth needs, leading to significant hydrolysis of nutrients such as starch and protein. Specifically, in wheat grains, this process causes the degradation and destruction of the gluten protein network, fundamentally altering the processing properties of wheat flour. When using germinated wheat flour to make steamed buns and other staple foods, problems such as weakened dough strength, sticky texture, and coarse structure often arise. This severely limits the application of high-GABA germinated wheat flour in traditional staple food products, making it difficult to meet consumers' basic requirements for good taste and texture in staple foods.

[0005] Therefore, under the premise of ensuring the excellent and stable characteristics of wheat grains and steamed buns, how to obtain GABA with a high enrichment level as much as possible, find the balance between the two, and obtain high-GABA, high-quality wheat grains and steamed buns with the best comprehensive evaluation is an urgent problem to be solved in the development of wheat functional foods rich in GABA. Summary of the Invention

[0006] One object of the present invention is to provide a steamed bun rich in γ-aminobutyric acid and a method for preparing the same, so as to at least solve the above-mentioned problems.

[0007] To achieve the objectives and other advantages of this invention, a method for preparing steamed buns rich in γ-aminobutyric acid (GABA) is provided, comprising the following steps: 1) conditioning wheat grains to achieve a moisture content of 10%-20%; 2) placing the conditioned wheat grains from step 1) in a humid heat environment at a temperature of 60℃-70℃ and a relative humidity of 90%-98% for 1-6 hours to obtain wheat rich in GABA; 3) processing the wheat obtained in step 2) into wheat flour, then mixing it with water and yeast to prepare dough; 4) dividing and shaping the dough obtained in step 3), fermenting it, and then steaming it to obtain the steamed buns rich in GABA; wherein the content of GABA in the steamed buns is not less than 10 mg / 100 g dry weight.

[0008] Preferably, the wheat grains in step 1) are purple wheat grains.

[0009] Preferably, the wheat grains in step 1) are of the variety Ji Zi 439.

[0010] Preferably, in step 1), the moisture content of the grains is 15%-17%; and in step 2), the conditions for the wet heat treatment are: temperature 63℃-65℃, relative humidity 95%-98%, and treatment time 1-3 hours.

[0011] Preferably, in step 3), the amount of yeast added is 0.8%-1.2% of the weight of wheat flour; and the amount of water added when kneading the dough is 48%-52% of the weight of wheat flour.

[0012] The present invention also provides a steamed bun rich in γ-aminobutyric acid, which is prepared by the above-described method for preparing a steamed bun rich in γ-aminobutyric acid.

[0013] The present invention has at least the following beneficial effects: First, by treating different wheat varieties with wet heat and optimizing the wet heat treatment process, the GABA content in wheat grains was enhanced. The wheat variety Jizi 439, which has the potential for GABA enrichment and can still maintain the physicochemical properties of the original grain grains after wet heat treatment, was screened out. This realizes the application of wet heat treatment technology to enhance GABA in bulk grain wheat and expands the range of raw materials for GABA-rich foods.

[0014] Secondly, compared to the problems of sticky texture and coarse structure that often occur in steamed buns made with sprouted wheat flour, this invention, by selecting superior wheat varieties and optimizing wet heat treatment process parameters, can achieve high GABA enrichment while minimizing damage to the gluten protein network structure. This ensures that the key textural properties of the resulting steamed buns, such as specific volume, hardness, elasticity, and chewiness, are not significantly deteriorated compared to steamed buns made with untreated wheat flour, thus maintaining the basic sensory and edible quality of traditional steamed buns.

[0015] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0016] Figure 1 This is a graph showing the effect of conditioning moisture on GABA content in one embodiment of the present invention; Figure 2 This is a graph showing the effect of humid heat temperature on GABA content in one embodiment of the present invention; Figure 3 This is a graph showing the effect of humidity and heat on GABA content in one embodiment of the present invention; Figure 4 This is a graph showing the effect of humid heat time on GABA content in one embodiment of the present invention; Figure 5 This is a graph showing the GABA content of different wheat varieties after wet heat treatment in one embodiment of the present invention; Figure 6 This is an example of the electrophoretic patterns of wheat flour from three varieties, Y25, P1 and B3, and wheat flour after wet heat treatment in one embodiment of the present invention. In the figure, (a) is the reduced gel electrophoresis pattern and (b) is the non-reduced gel electrophoresis pattern. Figure 7 This is a diagram showing the appearance and cross-sectional structure of steamed buns prepared for different wet heat treatment times in one embodiment of the present invention; Figure 8 This is a graph showing the GABA content and growth rate of wheat flour and steamed buns made from it under different wet heat treatment times in one embodiment of the present invention. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings, so that those skilled in the art can implement it based on the description.

[0018] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0019] It should be noted that, unless otherwise specified, the experimental methods described in the following implementation plan are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified.

[0020] Example 1: Optimization of the process for enriching wheat GABA through wet heat treatment.

[0021] 1.1 Experimental Methods 1.1.1 Preparation of samples after damp heat treatment Weigh 50 g of wheat grains and quantitatively add water to adjust to a certain moisture content (conditioning). After sealing, mix the sample at room temperature to ensure uniform water absorption. Then, place the conditioned sample in a humidity chamber for humidity heat treatment. After humidity heat treatment, freeze-dry, pulverize, and sieve (50 mesh). The resulting wheat flour is stored at 4 ℃ for later use.

[0022] 1.1.2 Single-factor experiment on damp heat treatment Following the aforementioned damp heat treatment process, using GABA content as the evaluation index, single-factor experiments were conducted with different moisture content (10%, 15%, 20%, 25%, 30%), damp heat temperature (55℃, 60℃, 65℃, 70℃, 75℃), damp heat humidity (80%, 85%, 90%, 95%, 98%), and damp heat time (2 h, 3 h, 4 h, 5 h, 6 h). The fixed conditions for the four factors were 15% moisture content, 65℃ damp heat temperature, 98% damp heat humidity, and 6 h damp heat time. The main influencing factors were identified based on the results of one-way ANOVA, and their condition ranges were determined.

[0023] 1.1.3 Response Surface Design for Humid Heat Treatment Based on the analysis of single-factor results and the Box-Behnken experimental design principle, the process conditions for enriching wheat GABA content through hydrothermal treatment were optimized, with GABA content (Y) as the response value and conditioning moisture (X1), hydrothermal temperature (X2), and hydrothermal time (X3) as the main influencing factors. The experimental factors and levels are shown in Table 1.

[0024] Table 1. Factors and levels in the Box-Behnken experiment. 1.1.4 Determination of GABA content GABA content was determined by high performance liquid chromatography (HPLC). A 70% (v / v) ethanol solution was added to the sample at a 1:10 ratio. After extraction with shaking at room temperature for 1 h, the sample was centrifuged at 10000 g for 10 min, and the supernatant was collected. This process was repeated three times, and the supernatant was collected and diluted to volume. Under light-protected conditions, the reaction system contained 1 mL of supernatant, 0.2 mL of 0.04 g / mL NaHCO3 solution, and 0.4 mL of 2 mg / mL dansinyl chloride acetonitrile solution. After shaking and mixing, the mixture was placed in a 70 ℃ water bath for 20 min, cooled to room temperature, and filtered through a 0.22 mL filter membrane for testing. Chromatographic conditions: ZORBAX SB-C18 column (4.6 mm × 250 mm, 5 μm), isocratic elution, mobile phase composition and ratio: A (30 mmol / L sodium acetate): B (acetonitrile) = 73%:27%, flow rate 1 mL / min, column oven temperature 30 ℃, and detection wavelength 436 nm.

[0025] 1.2 Experimental Results 1.2.1 Results of Single-Factor Experiment 1.2.1.1 Effect of conditioning moisture on wheat GABA content Depend on Figure 1 It can be seen that the GABA content in wheat first increases and then decreases with the increase of conditioning moisture, and the conditioning moisture has a significant effect on the GABA enrichment. P <0.05). When the conditioning moisture content was 15%, the GABA content reached a maximum of 24.86 mg / 100g. The conditioning process before wet heat treatment affects the moisture content of wheat grains, and differences in conditioning moisture content alter the water absorption and distribution of wheat grains. Under suitable conditioning moisture conditions, the activity of glutamate decarboxylase (GAD) is enhanced, catalyzing the production of GABA from glutamate (Glu) through the α-decarboxylation reaction. Simultaneously, a sufficient moisture environment can also activate various hydrolytic enzymes such as amylase and protease, promoting enzymatic and non-enzymatic reactions, thus facilitating the efficient accumulation of GABA and its related metabolites. When the conditioning moisture content is low, endogenous enzymes are not fully activated. Under abiotic stress (such as high temperature and low oxygen), plants activate GAD activity by increasing the intracellular Ca²⁺ and H⁺ concentrations. However, when the moisture content of wheat grains is too high, the intracellular Ca²⁺ and H⁺ concentrations decrease, leading to the inhibition of GAD activity. Therefore, when the moisture content of the conditioning medium is higher than 15%, the GABA content decreases with increasing moisture content. Thus, the moisture content range for conditioning in the BBD response surface methodology was selected as 10%-20%.

[0026] 1.2.1.2 Effect of hot and humid temperature on wheat GABA content Depend on Figure 2 It can be seen that the GABA content is significantly affected by the temperature of the damp heat treatment. P<0.05), with increasing humid heat temperature, the GABA content showed a trend of first increasing and then decreasing, reaching a peak at 65 ℃. Glutamate decarboxylase (GAD) is an important factor affecting GABA enrichment, and heat shock can induce GAD activation. Within the range of 55-65 ℃, moderate heating can enhance GAD activity in wheat and promote the conversion of Glu to GABA; above 65 ℃, high temperature leads to a decrease in GAD activity, thereby reducing the enrichment of GABA in wheat. Therefore, the selected humid heat temperature range is 60-70 ℃.

[0027] 1.2.1.3 Effects of heat and humidity on wheat GABA content like Figure 3 As shown, under high humidity conditions, the GABA content in wheat grains shows a significant increasing trend with increasing humidity and heat. P <0.05). The GABA content reached its maximum when the humidity reached 98%. Humidity conditions during hydrothermal treatment have a dual regulatory effect on GABA synthesis in wheat. On the one hand, the high humidity environment, together with the water molecule layer on the wheat surface, creates a hypoxic stress environment, inhibiting the intracellular electron transport chain. Sugars are converted to pyruvate via glycolysis and further decomposed into ethanol and lactic acid, leading to a decrease in cytoplasmic pH. This activates GAD under acidic conditions, promoting GABA production. On the other hand, water vapor in the high humidity environment effectively replenishes the moisture lost from wheat grains due to high temperature through osmosis, controlling the system's moisture content within a suitable range and providing a suitable hydration environment for the GAD-catalyzed reaction. The results indicate that high humidity conditions are beneficial for GABA enrichment in wheat; therefore, the optimal humidity for hydrothermal treatment was determined to be 98%.

[0028] 1.2.1.4 Effect of hot and humid weather on wheat GABA content Depend on Figure 4 It can be seen that with the extension of moist heat time, the GABA content showed a gradual upward trend. After 4 h of moist heat treatment, the increase in GABA enrichment tended to be slow, and there was no significant difference in wheat GABA content between the 5 h and 6 h treatment groups. P >0.05). GABA accumulation is mainly affected by the activity of metabolism-related enzymes, substrate concentration, and product concentration. With prolonged wet heat treatment, endogenous metabolites in wheat are continuously consumed, Glu concentration decreases, and enzyme reaction rates, substrate conversion efficiency, and product decomposition efficiency all approach saturation, causing the GABA accumulation metabolic process to tend towards dynamic equilibrium. Therefore, after 5 hours of wet heat treatment, the GABA accumulation in wheat no longer increases significantly. P >0.05). Based on this, the damp heat time range in the BBD response surface methodology was selected as 4-6 h.

[0029] 1.2.2 Results of Response Surface Optimization for GABA Enrichment in Wheat under Humid-Heat Treatment The experimental design scheme and results of the Box-Behnken response surface optimization experiment are shown in Table 2.

[0030] Table 2 Box-Behnken Design and Experimental Results Analysis of the Box-Behnken test results revealed the optimal process parameters as follows: conditioning moisture content 16.68%, wet heat temperature 63.58 ℃, and wet heat time 5.28 h. To adapt to actual operating conditions, these parameters were modified to: conditioning moisture content 16.68%, wet heat temperature 63.60 ℃, and wet heat time 5.30 h. Combining the results of single-factor experiments, the optimal wet heat treatment conditions for enriching wheat GABA content were determined to be: conditioning moisture content 16.68%, wet heat temperature 63.60 ℃, wet heat humidity 98%, and wet heat time 5.30 h. Under these conditions, the predicted GABA content was 24.30 mg / 100g, and the verification experiment showed an actual measured value of 25.08 ± 1.12 mg / 100g, which is 420.33% higher than that of untreated wheat grains (4.82 mg / 100g).

[0031] Example 2: Screening of wheat varieties with γ-aminobutyric acid enrichment potential.

[0032] Referring to the hydrothermal treatment process in 1.1.1, the optimal hydrothermal treatment conditions obtained from Experimental Example 1 were adopted: conditioning moisture content 16.68%, hydrothermal temperature 63.60 ℃, hydrothermal humidity 98%, and hydrothermal time 5.30 h. Hydrothermal treatment was performed on wheat grains of 35 varieties, including 27 yellow wheat varieties, 5 purple wheat varieties, and 3 blue wheat varieties. The results are as follows: Figure 5 As shown.

[0033] Depend on Figure 5 It can be seen that after wet heat treatment, the GABA content increased to 11.93-31.12 mg / 100 g dry weight (the GABA content in untreated wheat varieties ranged from 0.76 to 6.87 mg / 100 g dry weight). Specifically, after wet heat treatment, the yellow wheat variety Y25 (31.12 mg / 100 g dry weight), the purple wheat variety P1 (Ji Zi 439, 30.17 mg / 100 g dry weight), and the blue wheat variety B3 (22.75 mg / 100 g dry weight) had the highest GABA content in their respective categories.

[0034] Example 3: Screening of wheat varieties rich in γ-aminobutyric acid with excellent processing characteristics.

[0035] 3.1 Experimental Methods 3.1.1 Experimental Samples The three γ-aminobutyric acid (GABA)-rich wheat varieties Y25, P1, and B3 selected in Example 2 were used as follows: A portion of these wheat varieties was directly crushed, sieved (50 mesh), and stored at 4 °C for later use, labeled as Y25, P1, and B3; the other portion was subjected to wet heat treatment under the optimal wet heat treatment conditions obtained in Experiment 1, followed by freeze drying, crushing, sieving (50 mesh), and storage at 4 °C for later use, labeled as HRH-Y25, HRH-P1, and HRH-B3.

[0036] 3.1.2 Electrophoresis Experiment SDS-polyacrylamide gel electrophoresis was performed using a 10% separating gel (pH 8.8) and a 5% stacking gel (pH 6.8). Each sample (30 mg) was mixed with 500 μl of extraction buffer (0.01 M Tris-HCl, pH 6.8, containing 10% (w / v) SDS, 5% (v / v) 2-mercaptoethanol (2-ME), 10% (v / v) glycerol, and 0.1% (w / v) bromophenol blue). For non-reduced protein samples, 2-ME was not added to the extraction buffer. After heating the samples at 99 °C for 8 min, they were centrifuged at 8000 g for 5 min. 20 μl of sample was loaded into each well, and electrophoresis was performed at a constant voltage of 120 V. The gel was stained with 0.25% (w / v) Coomassie Brilliant Blue and destaining in 10% acetic acid solution.

[0037] 3.1.3 Determination of Powder Properties Based on the moisture content of wheat flour and the calibrated sample amount of the Brabender farinograph, approximately 300 g of wheat flour was weighed, and approximately 62% distilled water was added to knead the dough. The amount of water added was adjusted so that the maximum torque of the mixed flour dough was 500±20 BU. Thus, the farinograph characteristics parameters of the mixed flour dough, such as water absorption rate, dough formation time, dough stability time, weakening degree, and farinograph quality index, were obtained.

[0038] 3.2 Experimental Results 3.2.1 Electrophoresis Experiment Results like Figure 6 As shown, proteins under both reducing and non-reducing conditions underwent significant changes after moist heat treatment. Compared to untreated samples, the intensity of wheat protein bands generally decreased or disappeared after moist heat treatment, especially in varieties Y25 and B3. These changes suggest possible protein aggregation, including the aggregation of high-molecular-weight gliadin and low-molecular-weight glutenin. Sudha et al. (2016) also reported that moist heat treatment altered the electrophoretic bands of high-molecular-weight gliadin in flour. Furthermore, Figure 6(b) The non-reducing electrophoresis patterns show no significant enhancement of visible bands in any of the samples, indicating that this type of polymerization may not be formed through disulfide bonds. Notably, the P1 wheat variety exhibited stronger tolerance to HRH treatment than the Y25 and B3 varieties, with minimal changes in its electrophoretic patterns. This characteristic may suggest that the processing characteristics and final product quality of the P1 variety are less affected by HRH treatment compared to the other two varieties.

[0039] 3.2.2 Results of powder value characteristic test The results of the powder value characteristic test are shown in Table 3.

[0040] Table 3. Flour characteristics of different wheat varieties before and after moist heat treatment. The data in the table are the mean ± standard deviation of the three samples. Different letters in the same row indicate significant differences (p < 0.05) between wheat flour samples. WF, HRH-WF1, HRH-WF3, HRH-WF5, and HRH-WF7 represent untreated P1 wheat flour, wheat flour treated with wet heat for 1 hour, 3 hours, 5 hours, and 7 hours, respectively. The same applies below.

[0041] Table 3 shows that variety P1 exhibited the highest water absorption rate at 63.7%, while variety B3 had the lowest at 57.9%. Variety P1 had the longest dough formation time at 2.52 minutes. Variety B3 had the highest stability time at 6.39 minutes, while variety P1 had the shortest stability time at 3.51 minutes. Variety Y25 had the lowest weakening degree at 35 FE. Flour parameters such as dough formation time and stability time effectively reflect the strength characteristics of flour; higher values ​​generally indicate stronger gluten and better resistance to mixing. Table 3 shows that among the three wheat varieties, variety P1 exhibited better mixing tolerance during the dough formation stage, while variety B3 showed stronger resistance to overmixing in the later stages of dough formation, a phenomenon consistent with the weakening degree analysis results. After wet heat treatment, the water absorption rate, dough formation time, and stability time of the three wheat flours all decreased significantly (p<0.05), while the weakening degree increased significantly (p<0.05). Among them, the P1 variety showed significantly less deterioration in dough formation time and weakening degree than the Y25 and B3 varieties, which is consistent with the trend of changes in electrophoretic patterns. Therefore, we consider using P1 after wet heat treatment, namely the Jizi 439 wheat variety, to develop steamed buns rich in GABA.

[0042] Example 4: Preparation of GABA-rich steamed buns.

[0043] 4.1 Experimental Methods 4.1.1 Experimental Samples The wheat variety P1, namely Jizi 439, which is rich in γ-aminobutyric acid and has excellent processing characteristics, was screened in Example 3. With fixed conditioning moisture content of 16.68%, a damp heat temperature of 63.60 ℃, and a damp heat humidity of 98%, P1 was treated with different damp heat treatment times: 1 hour, 3 hours, 5 hours, and 7 hours. After damp heat treatment, it was freeze-dried, pulverized, sieved (50 mesh), and stored at 4 ℃ for later use.

[0044] 4.1.2 Determination of Powder Properties Referring to 3.1.3, the flour properties of the wheat flour prepared in 4.1.1 were determined.

[0045] 4.1.3 Steamed Bun Making Mix the wheat flour prepared in 4.1.1 with an appropriate amount of yeast, stir at low speed until well mixed, then add water and stir at high speed to form a smooth and elastic dough. Place the dough in a refrigerator at 4 ℃ and let it stand for 10 minutes. Then take it out and divide it into 80 g small dough balls with a plastic knife. Place them in an aluminum round mold with oiled bottom and let them rise to the optimal height (35 ℃, 80%). Steam them in a pot of cold water for 30 minutes to obtain the steamed buns. Let them stand at room temperature for 1 hour and complete the determination of basic indicators within 12 hours.

[0046] 4.1.4 Evaluation of Steamed Bun Quality Specific volume: Refer to GB / T 21118-2007.

[0047] Color difference: Measured using a colorimeter. Take steamed buns of a certain size and test three times at the same location, then take the average value. The measurement parameters are L*, a*, and b* values.

[0048] Texture: The firmness of steamed buns was tested using the full texture analysis mode of a texture analyzer. The steamed buns were left at room temperature for 1 hour, then cut vertically into 25 mm slices along the center line. The slices were placed horizontally on a load-bearing platform. The test parameters were: pre-test speed 60 mm / min, post-test speed 60 mm / min, compression rate 50%, time interval between two compressions 5 s, and initial sensing force 0.05 N. Parameters such as hardness, adhesion, elasticity, cohesiveness, adhesiveness, chewiness, and resilience were obtained.

[0049] Analysis of appearance and internal texture structure: photographs.

[0050] GABA content: Refer to 1.1.4.

[0051] 4.2 Experimental Results 4.2.1 Results of powder properties determination.

[0052] The results are shown in Table 4.

[0053] Table 4. Effects of different wet heat treatment times on wheat flour properties Table 4 shows the flour water absorption rate, reflecting the amount of water required to reach 500 ± 20 FU during dough formation. Glutenin and gliadin are the most important proteins in wheat flour for gluten formation, both possessing strong water absorption capacity. Studies have shown that wet heat treatment alters the structure of high molecular weight gliadin components, leading to a decrease in wheat flour water absorption. Therefore, the reduced water absorption of wheat flour treated with wet heat (HRH) may be attributed to structural changes in gliadin. Dough formation time and stability time are effective indicators of flour strength properties. Extended dough formation and stability times indicate stronger gluten and better mixing tolerance. Aggregated gluten components significantly contribute to dough strength and toughness. Therefore, HRH treatment may induce structural changes in gluten, ultimately leading to alterations in dough formation and stability times. Thus, HRH treatment may alter the structure of gluten and gliadin in wheat flour, thereby reducing their water absorption. However, it is noteworthy that HRH treatment exhibits a bidirectional regulatory effect on other farinograph parameters, including dough formation time, stability time, fortification degree, and farinograph index. This characteristic gives it the potential to meet the specific powder requirements of different products, thereby expanding its application range.

[0054] 4.2.2 Results of steamed bun quality evaluation.

[0055] The appearance and cross-sectional structure of steamed buns are as follows: Figure 7 As shown in the figure; color, specific volume, and textural properties are shown in Table 5; GABA content and growth rate are shown in the figure. Figure 8 As shown.

[0056] Table 5. Test results of color, specific volume and textural properties of steamed buns under different humid heat treatment times. The visual appeal of food (including its appearance and color) significantly influences its market demand and consumer preferences. Figure 7 Externally, steamed buns made with untreated wheat flour (WF), HRH-treated flour for 1 hour (HRH-WF 1h), and HRH-treated flour for 3 hours (HRH-WF 3h) exhibit a uniform white color, full volume, and a smooth, wrinkle-free surface. With prolonged HRH treatment, steamed buns treated for 5 hours (HRH-WF 5h) show a slight decrease in volume, reduced surface smoothness, and slight wrinkles; while steamed buns treated for 7 hours (HRH-WF 7h) show a significant decrease in volume, a rougher surface, and more pronounced wrinkles. Cross-sectional analysis reveals that steamed buns made with wheat flour treated for 5 and 7 hours with HRH have a denser internal structure and smaller pores.

[0057] Table 5 shows that, regarding color, there was no significant difference in the L-value of steamed buns prepared within 5 hours of wet heat treatment (p>0.05); however, when the treatment time reached 7 hours, the L-value of the steamed buns decreased significantly (p<0.05), indicating that prolonged treatment would darken the product color. Furthermore, with the extension of wet heat treatment time, the a and b values ​​increased significantly, indicating that the treatment shifted the color of the steamed buns towards reddish and yellowish tones. Specific volume reflects the gas-producing capacity of the dough and the degree of expansion of the steamed buns, thus affecting their appearance, texture, and flavor. The results showed that with the extension of wet heat treatment time, the specific volume of the steamed buns decreased to some extent, but short-term treatment (within 3 hours) did not cause significant changes (p>0.05); however, extended treatment time (more than 5 hours) led to a significant decrease in specific volume (p<0.05). The textural characteristics of steamed buns directly reflect their quality and are affected by the protein-starch network structure and strength. The results showed that as the wet heat treatment time was extended, the hardness, adhesiveness and chewiness of the steamed buns did not change significantly within 3 hours (p>0.05), but increased significantly within 5 hours (p<0.05), reaching the maximum value at 7 hours; while the elasticity, cohesion and resilience did not differ significantly within 5 hours (p>0.05), but decreased significantly within 7 hours (p<0.05).

[0058] In summary, the duration of moist heat treatment significantly affects the quality characteristics of steamed buns. Short-term treatment (within 3 hours) did not show significant deterioration in the appearance, color, specific volume, and texture parameters of the steamed buns; however, long-term treatment (5 hours and above) led to a gradual decline in quality, manifested as shrinkage in volume, darkening of color, and hardening of texture. The results indicate that, to maintain the overall quality of steamed buns and consumer acceptance, the moist heat treatment time should be controlled within 3 hours.

[0059] Furthermore, by Figure 8 It was found that the GABA content in wheat flour continued to increase with the extension of the wet heat treatment time, but the rate of increase gradually slowed down. Specifically, within 1 hour of treatment, the GABA content increased from 2.14 mg / 100 g dry weight to 10.27 mg / 100 g dry weight, with an accumulation rate of 8.13 mg / h. Although the GABA content still increased significantly during the 5 to 7 hours of treatment, the accumulation rate had dropped to 1.21 mg / h. This shows that the efficiency of GABA accumulation in wet heat treatment is closely related to the treatment duration. The changes in GABA in steamed buns were similar to those in wheat flour. Overall, 3 hours of HRH treatment resulted in higher GABA accumulation efficiency and better steamed bun quality. Therefore, to obtain GABA-rich and high-quality steamed buns, it is recommended to select the P1 wheat variety, namely Jizi 439, and treat it with wet heat for 3 hours.

[0060] The number of devices and processing scale described herein are for simplification of the invention. Applications, modifications, and variations of the present invention regarding the γ-aminobutyric acid-rich steamed buns and their preparation methods will be readily apparent to those skilled in the art.

[0061] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a steamed bun rich in γ-aminobutyric acid, characterized by, Includes the following steps: 1) Condition the wheat grains to achieve a moisture content of 10%-20%; 2) Place the conditioned wheat grains from step 1) in a humid heat environment with a temperature of 60℃-70℃ and a relative humidity of 90%-98% for humid heat treatment for 1-6 hours to obtain wheat rich in γ-aminobutyric acid. 3) The wheat obtained in step 2) is made into wheat flour, and then mixed with water and yeast to make dough; 4) The dough obtained in step 3) is divided, shaped, fermented, and then steamed to obtain the steamed bun rich in γ-aminobutyric acid; wherein the content of γ-aminobutyric acid in the steamed bun is not less than 10 mg / 100 g dry weight.

2. The method of producing a γ-aminobutyric acid-enriched steamed bread according to claim 1, wherein The wheat grains in step 1) are purple wheat grains.

3. The method for preparing steamed buns rich in γ-aminobutyric acid as described in claim 2, characterized in that, The wheat variety used in step 1) is Jizi 439.

4. The method for preparing steamed buns rich in γ-aminobutyric acid as described in claim 1, characterized in that, In step 1), the moisture content of the grains is 15%-17%; in step 2), the conditions for wet heat treatment are: temperature 63℃-65℃, relative humidity 95%-98%, and treatment time 1-3 hours.

5. The method for preparing steamed buns rich in γ-aminobutyric acid as described in claim 1, characterized in that, In step 3), the amount of yeast added is 0.8%-1.2% of the weight of wheat flour; the amount of water added when kneading the dough is 48%-52% of the weight of wheat flour.

6. A steamed bun rich in γ-aminobutyric acid, characterized by The steamed bun is prepared by the method for preparing steamed buns rich in γ-aminobutyric acid as described in any one of claims 1-5.

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