A kudzu root coix seed fermentation liquid noodle and its preparation method

Abstract

The present invention belongs to the field of food processing, and particularly relates to a kudzu root coix seed fermented liquid noodle and a preparation method thereof, comprising the following steps: 1) preparing a kudzu root coix seed fermented liquid; 2) mixing the prepared kudzu root coix seed fermented liquid with flour, and successively performing dough kneading, dough proofing, rolling, and noodle cutting operations to finally obtain the kudzu root coix seed fermented liquid noodle. The nutritional value and biological activity of kudzu root coix seed are significantly improved by the fermentation of tea tree mushroom. The addition of the kudzu root coix seed fermented liquid significantly changes the texture, microstructure, and starch digestibility of the noodle. After adding the fermented liquid, the hardness, chewiness, and adhesiveness of the noodle are enhanced, while the elasticity and cohesiveness remain unchanged. After adding the fermented liquid, the contents of total amino acids and essential amino acids in the noodle also increase significantly, significantly improving the biological activity and nutritional value of the noodle.

Description

Technical Field

[0001] The present invention belongs to the technical field of food processing, and particularly relates to a kudzu root coix seed fermented liquid noodle and a preparation method thereof. Technical Background

[0002] Noodles are a traditional food and are widely consumed around the world due to their convenience, diversity, multi-functionality, nutrition, satisfactory taste and palatability. Since ancient times, noodles have been an indispensable part of the diets of many Eastern countries and developing countries. Noodles can be traced back to the Eastern Han Dynasty 2,000 years ago, and have a long history in China and are also one of the common foods of Chinese residents. Coix seed, also known as coix lacryma-jobi, coix seed, and job's tears, is an annual herbaceous crop. Coix seed is widely planted in Guizhou, Fujian, Jiangsu and other places in China and is one of the traditional cash crops in southern China. It has the reputation of "the king of gramineous plants in the world" because of its extremely high nutritional and medicinal value. Kudzu root is the dried root of a perennial deciduous vine, also known as wild kudzu root, yellow kudzu root, and powder kudzu root, etc. Kudzu root has the reputation of "ginseng in the north and kudzu root in the south" in China and is called "longevity dragon root" in Japan.

[0003] Considering that wheat flour used to make noodles has a high starch content, the nutritional value of noodles can be significantly improved if supplemented with kudzu root and coix seed. However, kudzu root has a high dietary fiber content, and coix seed contains a relatively high amount of polysaccharides. And products developed by the submerged fermentation technology of edible fungi have been applied in food. For example, Rigling et al. (2021) used Flammulina velutipes to conduct submerged fermentation on green tea extract to prepare a new type of tea beverage. Nedele et al. (2021) fermented soybean beverage with Lycoperdon pyriforme. The fermentation transformed the green color, fishy smell and other off-flavors in the soybean beverage into oat flavor and mushroom flavor, and improved the nutritional components and antioxidant capacity of the beverage. On this basis, there is no research on preparing noodles by fermenting kudzu root and coix seed through the submerged fermentation technology of edible fungi in the prior art. Therefore, it is obviously of great significance to provide a kudzu root coix seed fermented liquid noodle that can give full play to the use effects of kudzu root and coix seed, enrich the variety of noodle products, improve the grade of functional products, increase the economic added value of noodles, and promote the industrialization process of agricultural products such as coix seed, kudzu root and edible fungi. Summary of the Invention

[0004] The purpose of the present invention is to provide a kudzu root coix seed fermented liquid noodle and a preparation method thereof. Through fermenting kudzu root and coix seed with Agrocybe aegerita, and mixing the fermented kudzu root coix seed fermented liquid with flour, the use effects of kudzu root and coix seed can be given full play, the variety of noodle products can be enriched, the grade of functional products can be improved, the economic added value of noodles can be increased, and the industrialization process of agricultural products such as coix seed, kudzu root and edible fungi can be promoted.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] The present invention provides a preparation method of kudzu root coix seed fermented liquid noodles, comprising the following steps:

[0007] 1) Prepare kudzu root coix seed fermented liquid;

[0008] 2) Mix the prepared kudzu root coix seed fermented liquid with flour, and successively perform dough kneading, dough proofing, rolling, and noodle cutting operations to finally obtain kudzu root coix seed fermented liquid noodles.

[0009] Furthermore, in step 1), the specific preparation method of the kudzu root coix seed fermented liquid comprises the following steps:

[0010] (1) Select coix seeds, treat the coix seeds with a NaClO solution, then rinse them several times with deionized water, add 10 times the volume of deionized water, soak them in an incubator at 36 °C for 10 h, then spread the soaked coix seed grains between two layers of gauze, and germinate them in an incubator at 29 °C and 95% relative humidity in the dark for 24 h to obtain germinated coix seeds after the germination ends;

[0011] (2) Grind the germinated coix seeds and kudzu roots with water at a mass concentration ratio of 1:6 respectively, then perform gelatinization respectively. After the gelatinization is completed, add thermostable amylase and perform a water bath at 85 °C for 50 min respectively, then cool. After cooling, add saccharifying enzyme respectively and perform a water bath at 65 °C for 50 min until saccharification is complete, then take them out and inactivate the enzymes on an induction cooker to obtain coix seed enzymatic hydrolysate and kudzu root enzymatic hydrolysate respectively;

[0012] (3) Mix the coix seed enzymatic hydrolysate and the kudzu root enzymatic hydrolysate in equal proportions to obtain kudzu root coix seed enzymatic hydrolysate; sterilize the kudzu root coix seed enzymatic hydrolysate at 121 °C for 20 min, inoculate 4% of edible mushroom seed liquid after cooling to room temperature, and continuously ferment it in a shaker for 7 d to obtain kudzu root coix seed fermented liquid.

[0013] Furthermore, in step (1), the mass concentration of the NaClO solution is 0.1%, and the treatment time of the coix seeds with the NaClO solution is 30 min.

[0014] Furthermore, in step (2), the gelatinization time is 20 min.

[0015] Furthermore, in step (2), the dosage of thermostable amylase is 100 U / g, and the dosage of saccharifying enzyme is 200 U / g.

[0016] Furthermore, in step (3), the edible mushroom is Agrocybe aegerita.

[0017] Further, in step (3), the parameters of the shaker fermentation process are 27 °C and 170 r / min.

[0018] Further, in step 2), the addition amount of the Puerariae lobata and coix seed fermentation broth is 22%-32%.

[0019] The present invention also provides a Puerariae lobata and coix seed fermentation broth noodle prepared by using the preparation method of the Puerariae lobata and coix seed fermentation broth noodle.

[0020] The beneficial effects of the present invention are as follows:

[0021] In the present invention, Pleurotus eryngii is used to ferment Puerariae lobata and coix seeds, and the fermented Puerariae lobata and coix seed fermentation broth is mixed with flour to obtain Puerariae lobata and coix seed fermentation broth noodles. The fermentation by Pleurotus eryngii significantly improves the nutritional value and biological activity of Puerariae lobata and coix seeds. The addition of the Puerariae lobata and coix seed fermentation broth significantly changes the texture, microstructure and starch digestibility of the noodles. After adding the fermentation broth, the hardness, chewiness and adhesiveness of the noodles are enhanced, while the elasticity and cohesiveness remain unchanged. At the same time, the contents of aldehydes, ketones, alcohols, esters, etc. in the noodles are also significantly increased, and these volatile components together endow the noodles with a unique fruity and grassy flavor. In addition, after adding the fermentation broth, the total amino acid and essential amino acid contents of the noodles are also significantly increased, significantly improving the biological activity and nutritional value of the noodles. Description of the Drawings

[0022] Figure 1 : A bar graph showing the effect of fermentation time on the total phenols and flavonoids of the Puerariae lobata and coix seed fermentation broth. Different letters in the figure indicate significant differences (P<0.05);

[0023] Figure 2 : A bar graph showing the effect of fermentation time on the antioxidant activity of the Puerariae lobata and coix seed fermentation broth. Different letters in the figure indicate significant differences (P<0.05);

[0024] Figure 3 : A bar graph showing the effect of fermentation time on the crude polysaccharides and reducing sugars of the Puerariae lobata and coix seed fermentation broth. Different letters in the figure indicate significant differences (P<0.05);

[0025] Figure 4 : A bar graph showing the effect of fermentation time on the soluble proteins and soluble peptides of the Puerariae lobata and coix seed fermentation broth. Different letters in the figure indicate significant differences (P<0.05);

[0026] Figure 5 : A bar graph showing the effect of fermentation time on the GABA of the Puerariae lobata and coix seed fermentation broth. Different letters in the figure indicate significant differences (P<0.05);

[0027] Figure 6: Bar graph showing the effect of fermentation time on the content of coixol in the Pueraria thomsonii and coix seed fermented liquid. Different letters in the figure indicate significant differences (P<0.05);

[0028] Figure 7 : Bar graph showing the effect of fermentation time on the content of puerarin in the Pueraria thomsonii and coix seed fermented liquid. Different letters in the figure indicate significant differences (P<0.05);

[0029] Figure 8 : Starch digestion curves of noodles (N-0%, N-22%, N-32%, N-42%, WN-32% are noodles added with 0%, 22%, 32%, 42% Pueraria thomsonii and coix seed fermented liquid and 32% enzymolysis liquid of Pueraria thomsonii and coix seed respectively);

[0030] Figure 9 : Fitting curves of starch digestion of noodles (N-0%, N-22%, N-32%, N-42%, WN-32% are noodles added with 0%, 22%, 32%, 42% Pueraria thomsonii and coix seed fermented liquid and 32% enzymolysis liquid of Pueraria thomsonii and coix seed respectively);

[0031] Figure 10 : Fourier transform infrared spectra of noodles (N-0%, N-22%, N-32%, N-42% and WN-32% are noodles added with 0%, 22%, 32%, 42% Pueraria thomsonii and coix seed fermented liquid and 32% enzymolysis liquid of Pueraria thomsonii and coix seed respectively);

[0032] Figure 11 : Effect of adding different proportions of Pueraria thomsonii and coix seed fermented liquid on the microstructure of noodles. a - e are noodles added with 0%, 22%, 32%, 42% Pueraria thomsonii and coix seed fermented liquid and 32% enzymolysis liquid of Pueraria thomsonii and coix seed respectively;

[0033] Figure 12 : X-ray diffraction patterns of noodles with different proportions of Pueraria thomsonii and coix seed fermented liquid added. N-0%, N-22%, N-32%, N-42%, WN-32% are noodles added with 0%, 22%, 32%, 42% Pueraria thomsonii and coix seed fermented liquid and 32% enzymolysis liquid of Pueraria thomsonii and coix seed respectively;

[0034] Figure 13 : Line graph showing the effect of adding Pueraria thomsonii and coix seed fermented liquid on the color of noodles. Different letters in the figure indicate significant differences (P<0.05);

[0035] Figure 14 : Effect of adding Pueraria thomsonii and coix seed fermented liquid on the antioxidant property of noodles. Different letters in the figure indicate significant differences (P<0.05);

[0036] Figure 15 : Bar graph showing the types and total amounts of volatile flavors in noodles;

[0037] Figure 16 : To study the effects of adding fermented kudzu root and coix seed liquid on GABA, puerarin and flavonoids in noodles, different letters in the figure indicate significant differences (P<0.05). Detailed implementation method

[0038] The following experimental examples and embodiments are used to further illustrate the present invention, but are not limited to the present invention.

[0039] Experimental Example 1

[0040] 1. Selection of edible fungi and its liquid fermentation on kudzu root and coix seed

[0041] 1.1 Materials and equipment

[0042] 1.1.1 Experimental materials

[0043] Coix seeds were purchased from Guizhou Renxin Agricultural Development Co., Ltd., and kudzu root powder was purchased from Lanshan Green Food Co., Ltd. in Rongjiang County, Guizhou Province. Agrocybe aegerita, Pleurotus ostreatus, Coriolus versicolor, Ganoderma lucidum, Poria cocos were provided by the Edible Fungi Research Institute of Xishui County, Guizhou Province. Potato dextrose broth medium: 25 g / L of potato dextrose broth medium PDB, 2 g / L of peptone, 2 g / L of food-grade potassium dihydrogen phosphate, 1.5 g / L of food-grade magnesium sulfate.

[0044] 1.1.2 Drugs and reagents

[0045] Drugs and reagents are shown in Table 1

[0046] Table 1 Drugs and reagents

[0047]

[0048] 1.1.3 Experimental instruments and equipment

[0049] Table 2 Main instruments and equipment

[0050]

[0051]

[0052] 1.2 Experimental methods

[0053] 1.2.1 Preparation of fermentation raw materials

[0054] (1) Preliminary experiment: Preparation of germinated coix seeds

[0055] Select coix seeds with plump grains, treat the coix seeds with 0.1% NaClO solution for 30 min, rinse them several times with deionized water, add 10 times the volume of deionized water, soak them in an incubator at 36 °C for 10 h, then spread the soaked coix seed grains between two layers of gauze, and germinate them in the dark in an incubator at 29 °C and 95% relative humidity for 24 h. After the germination is completed, collect and reserve them.

[0056] (2) Enzymatic hydrolysis process of Pueraria lobata and germinated coix seeds

[0057] On the basis of preliminary experiments, germinated coix seeds and Pueraria lobata were respectively pulped with water at a ratio of 1:6 (w / v). After gelatinization on an induction cooker for 20 min respectively, 100 U / g of thermostable amylase was added respectively and incubated in a water bath at 85 °C for 50 min. After cooling, 200 U / g of glucoamylase was added respectively and incubated in a water bath at 65 °C for 50 min until saccharification was complete. Then they were taken out and inactivated on the induction cooker respectively.

[0058] 1.2.2 Selection of edible fungi for fermenting the enzymatic hydrolysate of Pueraria lobata and coix seeds and preparation of fermentation broth

[0059] On the basis of preliminary experiments, the enzymatic hydrolysate of Pueraria lobata and the enzymatic hydrolysate of coix seeds were compounded in equal proportions and suitable for edible fungi fermentation. Five different species of edible fungi (Agrocybe aegerita, Pleurotus ostreatus, Coriolus versicolor, Ganoderma lucidum, Poria cocos) were selected to ferment the enzymatic hydrolysate of Pueraria lobata and coix seeds in equal proportions for 4 d. Using the sensory score and GABA content as indicators, the fermentation strains were determined. The enzymatic hydrolysates of Pueraria lobata and germinated coix seeds after enzymatic hydrolysis were mixed in equal proportions and sterilized at 121 °C for 20 min. After cooling to room temperature, 4% of the edible fungi seed liquid was inoculated, and continuous fermentation was carried out in a shaker (27 °C, 170 r / min) for 7 d. Samples were taken at intervals of 24 h (3 parallel samples were made at the same time). Then the fermentation broth of Pueraria lobata and coix seeds can be obtained.

[0060] 1.2.3 Sensory evaluation

[0061] The five kinds of fermentation broths to be evaluated were coded with digital blind labels. A sensory evaluation group composed of 20 experienced teachers and students majoring in food-related fields carried out sensory evaluation in a well-ventilated food laboratory with sufficient light. The sensory characteristics were determined by color, taste, smell, tissue form and acceptability, and a score of 1.0 - 5.0 was used (5 was excellent, and 1 was unacceptable), and the scoring rules in Table 3 were used for scoring. Finally, each sensory characteristic rating was multiplied by a factor of 4, and the total score was expressed as 100.

[0062] Table 3 Sensory scoring standard for the fermentation broth of Pueraria lobata and coix seeds

[0063]

[0064] 1.2.4 Determination of flavonoid and total phenol contents

[0065] (1) Determination of flavonoid content

[0066] Take 1 mL of the Pueraria coix seed fermentation broth sample, add 1 mL of 5% NaNO 2 solution, and after reacting for 6 min, add 1 mL of 10% Al(NO 3 ) 3 . After standing for 6 min, add 3 mL of mol / L NaOH and react again for 15 min. Measure its absorbance at 510 nm. Use ultrapure water as the blank control, and the results are expressed in rutin equivalents (mg RE / mL). Prepare a series of standard solutions of rutin at 0, 0.2, 0.4, 0.6, 0.8, and 1.0 mg / mL with methanol, and obtain the standard curve according to the above operation.

[0067] (2) Determination of total phenol content

[0068] Absorb 0.2 mL of the fermentation broth, 1.3 mL of deionized water, and 0.25 mL of Folin reagent into a centrifuge tube, mix well and let stand for 6 min, then add 0.75 mL of 20% Na 2 CO 3 reagent, and finally make up the volume to 5 mL with deionized water. After mixing well, react in a water bath at 40 °C in the dark for 2 h, and measure the absorbance at 760 nm. Draw a standard curve using gallic acid GAE (gallic acid equivalents) as the standard product, and the total phenol content of the sample is expressed in gallic acid (GAE) equivalents, with the unit: μg GAE / mL.

[0069] Preparation of gallic acid standard curve: Weigh 10 mg of gallic acid standard product, dissolve it with water and make up the volume to 50 mL to prepare a standard solution of 200 μg / mL. Prepare a standard series of 20, 40, 60, 80, and 100 μg / mL respectively. Accurately absorb 0.2 mL of gallic acid standard solution, 1.3 mL of deionized water, and 0.25 mL of Folin reagent into a centrifuge tube, mix well and let stand for 6 min, then add 0.75 mL of 20% Na 2 CO 3 reagent, and finally make up the volume to 5 mL with deionized water. After shaking and mixing well, react in a water bath at 40 °C in the dark for 2 h, and measure the absorbance at 760 nm.

[0070] 1.2.5 Determination of antioxidant activity

[0071] (1) Ability to scavenge DPPH free radicals

[0072] Take 2 mL of the sample (dilute the sample to an appropriate multiple) and mix it with 2 mL of DPPH solution (0.2 mM, prepared with absolute ethanol) in a test tube, vortex and mix well, and place it in the dark at room temperature for 30 min, and measure the absorbance at 517 nm.

[0073]

[0074] Where A1 is the absorbance value of the blank group with absolute ethanol replacing the DPPH solution, and A2 is the absorbance value of the sample group.

[0075] (2) Ability to scavenge ABTS free radicals

[0076] Mix 7.00 mM ABTS solution and 2.45 mM potassium persulfate solution in a 1:1 ratio, place it in a refrigerator at 4 °C in the dark for 16 h, and adjust the absorbance value to about 0.70 ± 0.02 at 734 nm. Take 2 mL of the sample (dilute the sample to an appropriate multiple) and mix it with 3 mL of ABTS solution by shaking. After standing in the dark at room temperature for 30 min, measure the absorbance value at a wavelength of 734 nm.

[0077]

[0078] Where A1 is the absorbance value of the blank group with absolute ethanol replacing the ABTS working solution, and A2 is the absorbance value of the sample group.

[0079] 1.2.6 Determination of reducing sugar and crude polysaccharide

[0080] (1) Determination of reducing sugar content

[0081] The 3,5-dinitrosalicylic acid method (DNS method) was used to determine the reducing sugar content of the Pueraria coix seed fermentation broth. Prepare a glucose standard solution of 1 mg / mL with glucose dried to a constant weight. Take 0, 0.1, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0 mL of the glucose standard solution into test tubes in turn, make up to 1.0 mL with deionized water, add 3 mL of DNS reagent, boil in a boiling water bath for 5 min, take it out and cool, then make up to 10 mL with water, mix well, and measure the absorbance value at a wavelength of 540 nm to make a standard curve. Take 1 mL of the sample and determine the reducing sugar content in the Pueraria coix seed fermentation broth according to the above standard curve steps.

[0082] (2) Determination of crude polysaccharide content

[0083] Absorb 0, 0.2, 0.4, 0.6, 0.8, 1.0 mL of glucose standard solution (0.1 mg / mL) into test tubes, make up to 1.0 mL with deionized water, add 6% freshly prepared phenol, mix well and then add 5 mL of concentrated sulfuric acid. Shake the solution, let it cool, and measure at a wavelength of 490 nm with deionized water as the blank. Draw a polysaccharide standard curve based on the known glucose concentration and absorbance value.

[0084] Treatment of Puerariae lobatae semen coicis fermentation broth: Centrifuge the Puerariae lobatae semen coicis fermentation broth (10610×g, 15 min), take 10 mL of the supernatant into a centrifuge tube, and simultaneously add 4 times the volume of absolute ethanol. Place the centrifuge tube in a 4°C refrigerator for alcohol precipitation for 20 h, then centrifuge (10610×g, 15 min), pour out the supernatant, dissolve the residue in water to 30 mL, shake well, take 1 mL of the sample into a test tube, and determine the content of crude polysaccharide according to the above steps.

[0085] 1.2.7 Determination of soluble peptides and soluble proteins

[0086] The determination of soluble proteins in the Puerariae lobatae semen coicis fermentation broth refers to SN / T 3926-2014 "Determination of Protein Content in Exported Dairy, Egg, and Legume Foods".

[0087] Determination method of soluble peptides: Folin-phenol reagent A: Dissolve 1 g of Na 2 CO 3 in 50 mL of 0.2 mol / L NaOH, dissolve 0.5 g of CuSO 4 5H 2 O in 100 mL of 1% sodium tartrate solution, then mix 50 mL of the former with 1 mL of the latter, and prepare it fresh for use. Folin-phenol reagent B: 1 mol / L Folin-phenol reagent application solution. Take 2.0 mL of the sample, add 2.0 mL of 10% trichloroacetic acid, mix well, place at room temperature for 30 min, centrifuge at 10610×g for 10 min, take the supernatant, dilute it to 20 mL with 5% trichloroacetic acid, then take 1.0 mL of the sample dilution, add 5.0 mL of Folin-phenol reagent A and mix well, place in a 30°C water bath for 10 min, then add 1.0 mL of Folin-phenol reagent B, keep warm at 30°C for 30 min, and measure at 650 nm. Use 1.0 mL of 5% trichloroacetic acid as a control, and calculate the content of soluble peptides in the sample with reference to the standard curve.

[0088] Drawing of the standard curve: Using reduced glutathione (GSH) as the standard product, prepare a 2.0 mg / mL standard solution with 5% trichloroacetic acid solution, and prepare GSH standard solutions with concentrations of 0.0, 0.2, 0.4, 0.8, 1.2, 1.6, and 2.0 mg / mL respectively.

[0089] 1.2.8 Determination of γ-aminobutyric acid

[0090] Sample treatment: Take 0.6 mL of the sample respectively, and then add 0.6 mL of 0.5 mol / L sodium bicarbonate and 0.6 mL of 1% FDNB solution (2,4-dinitrofluorobenzene) respectively. Carry out the derivatization reaction in the dark at 60°C in a water bath for 1 h, then add 4.2 mL of 0.12% phosphoric acid solution, filter through a membrane, and analyze on the machine.

[0091] Preparation of standard curve: Weigh 10 mg of GABA standard, dissolve it with water and make up the volume to 50 mL to prepare a 200 μg / mL GABA standard solution. Prepare gradient concentration solutions of GABA standard with concentrations of 10 μg / mL, 20 μg / mL, 40 μg / mL, 60 μg / mL, 80 μg / mL, 100 μg / mL, and 200 μg / mL respectively. Take 0.6 mL of the standard solution and add 0.6 mL of 0.5 mol / L sodium bicarbonate and 0.6 mL of 1% 2,4-dinitrofluorobenzene (FDNB) solution (dissolved with acetonitrile and placed in a brown bottle). Place it in a water bath at 60 °C for 1 h for derivatization reaction, then add 4.2 mL of phosphoric acid solution with a volume fraction of 0.12% for light avoidance treatment, filter through a membrane, and inject into the machine. The following standard curve equation is obtained from the concentration of the GABA standard and the corresponding absorbance value:

[0092] y = 6.1172x - 0.9054 R 2 = 0.9991 (2 - 3)

[0093] Chromatographic conditions: Mobile phase: Acetonitrile: Phosphoric acid solution (volume fraction 0.12%) = 50:50; Detection wavelength 370 nm, column temperature 35 °C, flow rate 1.0 mL / min, injection volume 10 μL, analysis time 10 min.

[0094] 1.2.9 Determination of coixol

[0095] Chromatographic conditions: Thermo UltiMate 3000 high performance liquid chromatograph, using Acclaim TM 120 C18 column (inner diameter 4.6 × 250 mm, particle size 5 μm), detector ultraviolet wavelength 232 nm, column temperature 25 °C, analysis time 10 min, flow rate 1 mL / min, injection volume 10 μL, mobile phase: Acetonitrile: 0.12% phosphoric acid solution = 30:70.

[0096] Drawing of standard curve: Add coixol standard to methanol and make up the volume to prepare gradient concentration solutions with concentrations of 100 μg / mL, 75 μg / mL, 50 μg / mL, 25 μg / mL, 10 μg / mL, 5 μg / mL, and 2.5 μg / mL respectively. Place in a brown bottle, filter through a membrane, and inject into the machine. Calculate the standard curve equation from the concentration of the coixol standard and the corresponding absorbance value.

[0097] Determination of sample: Take 10 mL of the sample and rotary evaporate it to dryness, dissolve it with methanol and make up the volume to 10 mL, filter through a membrane, and inject into the machine. The following standard curve equation is obtained:

[0098] y = 0.5585x - 0.1815 R 2=0.9995 (2-4)

[0099] 1.2.10 Determination of puerarin

[0100] Chromatographic conditions: Thermo UltiMate 3000 high performance liquid chromatograph, using Acclaim TM 120 C18 column (inner diameter 4.6×250 mm, particle size 5 μm), detector UV wavelength 250 nm, column temperature 30°C, analysis time 10 min, flow rate 1 mL / min, injection volume 10 μL, mobile phase methanol: water = 30:70.

[0101] Drawing of standard curve: Weigh 10 mg of puerarin standard, dissolve it in 25% methanol solution, dilute to 50 mL, prepare a 200 μg / mL standard solution, and then prepare different gradients of puerarin standard series, pass through the membrane, and put it on the machine. The following standard curve equation is obtained by the concentration of puerarin standard and the corresponding absorbance value:

[0102] y=0.5345x-1.2696 R 2 =0.9993 (2-5)

[0103] Sample determination: First, pass the Pueraria lobata and Coix Seed Rice fermentation liquid through a colloid mill, centrifuge at 10610×g for 10 minutes, take 10mL of the fermentation liquid and rotary evaporate to dryness in a round-bottom flask, then dissolve it with 25% methanol solution and make it up to 10mL, filter it through a 0.22μm filter membrane, and put it on the machine. Substitute the peak area of ​​the sample into the standard curve to calculate the puerarin content in the sample.

[0104] 1.2.11 Determination of phenolic substances

[0105] Pretreatment of fermentation broth: 10 mL of fermentation broth was sampled regularly at 0d, 1d, 2d, 3d, 4d, 5d, 6d, and 7d after the cultivation of Agrocybe tumefaciens. The supernatant was collected after centrifugation at 10610×g for 10 min, filtered through a 0.22μm filter membrane and filled into a liquid phase bottle for further analysis.

[0106] Preparation of standard solution: Weigh 10 mg of each solid standard (purity>98%) of ferulic acid, caffeic acid, chlorogenic acid, catechin, epicatechin, kaempferol, rutin, etc., dissolve in methanol or dimethyl sulfoxide solution and make up to 5 mL. The concentration of the standard stock solution of the above 7 compounds is 5 mg / mL.

[0107] Chromatographic conditions: Thermo UltiMate 3000 high performance liquid chromatograph, using Acclaim TMA 120 C18 column (inner diameter 4.6×250 mm, particle size 5 μm), mobile phase A is a 0.05% trifluoroacetic acid solution, and mobile phase B is methanol. The elution gradient of the mobile phase is shown in Table 2-4. The column temperature is 30 °C; the detection wavelength of the ultraviolet detector is 280 nm, the analysis time is 20 min, and the injection volume is 10 μL.

[0108] Table 4 Gradient elution program of chromatographic conditions

[0109]

[0110] 1.2.12 Statistical analysis

[0111] Software such as SPSS 22 and Excel was used to process and analyze the data. The analysis results are presented as mean ± standard deviation. The significance of the differences was obtained through one-way ANOVA analysis (using Tukey's multiple range test), and different letters were used to represent them (P < 0.05 indicates a statistically significant difference). The graphs of the analyzed data were plotted using Origin software. All the results were obtained through the processing and analysis of three parallel data sets.

[0112] 1.3 Results and discussion

[0113] Selection of edible mushroom strains:

[0114] Using the contents of GABA, flavonoids, puerarin, and sensory evaluation scores as indicators, Poria cocos, Agrocybe aegerita, Ganoderma lucidum, Pleurotus ostreatus, and Coriolus versicolor were used to ferment the enzymolysis solution of Pueraria lobata and Coix lacryma-jobi. The results are shown in Table 5. After comparison, Agrocybe aegerita was selected as the subsequent fermentation strain.

[0115] Table 5 Effects of fermentation by different edible mushrooms on GABA, flavonoids, puerarin, and sensory properties of the enzymolysis solution of Pueraria lobata and Coix lacryma-jobi

[0116]

[0117] Note: Different letters in the table indicate significant differences (P < 0.05)

[0118] Effects of Agrocybe aegerita fermentation on total phenols and flavonoids in the enzymolysis solution of Pueraria lobata and Coix lacryma-jobi:

[0119] From Figure 1It can be seen that fermentation significantly increased the total phenol content of Pueraria coix seed (P < 0.05). The total phenol content of the enzymatic hydrolysate of coix seed (0 days) was 141.84 ± 2.813 mg GAE / 100 mL, and after 4 days of fermentation, it was 242.86 ± 8.38 mg GAE / 100 mL, an increase of 71.21%. After that, the total phenol content decreased slightly and tended to be stable. During the fermentation process of Pueraria coix seed by Agrocybe aegerita, the flavonoid content showed a trend of first increasing and then decreasing. The flavonoid content of the enzymatic hydrolysate of Pueraria coix seed (0 days) was 58.91 ± 3.25 mg RE / 100 mL, and it reached 146.70 ± 2.69 mg RE / 100 mL after 2 days of fermentation; then it showed a slight downward trend, and the flavonoid content decreased to 126.04 ± 3.94 mg RE / 100 mL after 7 days, still higher than that at 0 days of fermentation (P < 0.05).

[0120] Effect of Agrocybe aegerita fermentation on the antioxidant activity of Pueraria coix seed:

[0121] The DPPH and ABTS methods were selected to analyze the changes in the antioxidant capacity of the enzymatic hydrolysate of Pueraria coix seed during the fermentation process by Agrocybe aegerita. As Figure 2 can be seen, with the prolongation of the fermentation time, the scavenging rates of DPPH and ABTS free radicals showed a trend of first increasing and then decreasing, and both reached the maximum values at 4 days of fermentation, which were 89.28% (ABTS) and 69.25% (DPPH), respectively. In the later stage of fermentation, the scavenging rates of ABTS and DPPH free radicals began to decline, but were still higher than those without fermentation (0 days). Thus, it can be seen that Agrocybe aegerita fermentation improved the antioxidant capacity of Pueraria lobata and coix seed.

[0122] Effect of Agrocybe aegerita fermentation on the reducing sugar and polysaccharide of Pueraria lobata and coix seed:

[0123] As Figure 3 can be seen, the reducing sugar content in the fermentation broth of Pueraria coix seed fermented by Agrocybe aegerita showed a trend of first increasing and then decreasing with the prolongation of the fermentation time. With the increase of the fermentation time, the crude polysaccharide content in the fermentation broth of Pueraria coix seed showed a trend of first increasing and then decreasing. Agrocybe aegerita continuously secreted intracellular polysaccharide and extracellular polysaccharide in the early stage of fermentation, so the content of crude polysaccharide increased rapidly at this time. At this time, a large amount of extracellular polysaccharide of Agrocybe aegerita accumulated, and reached the maximum value of 9.67 ± 0.12 mg / mL on the 3rd day.

[0124] Effect of Agrocybe aegerita fermentation on the soluble peptides and soluble proteins of Pueraria coix seed:

[0125] As Figure 4 shown, with the prolongation of the fermentation time, the soluble protein content showed a trend of first increasing and then decreasing. On the 2nd day of fermentation, the soluble protein content reached the highest value of 0.83 ± 0.02 mg / mL,

[0126] Effect of Agrocybe aegerita fermentation on GABA in Pueraria thomsonii and Coix lacryma-jobi

[0127] The change of GABA content in the enzymolysis solution of Pueraria thomsonii and Coix lacryma-jobi during fermentation is as Figure 5 shown. The GABA content in the unfermented enzymolysis solution of Pueraria thomsonii and Coix lacryma-jobi was 37.84±0.24 μg / mL, and it increased significantly with the prolongation of fermentation time, with a 64.96% increase after 7 days of fermentation.

[0128] Effect of Agrocybe aegerita fermentation on coixenolide in Pueraria thomsonii and Coix lacryma-jobi

[0129] The coixenolide in the fermentation broth of Pueraria thomsonii and Coix lacryma-jobi is as Figure 6 shown. The coixenolide content increased from 47.79±0.20 μg / 100 mL (0 day) to 63.4±1.71 μg / 100 mL (5 days), and decreased slightly to 46.13±0.35 μg / 100 mL (7 days) in the later stage of fermentation.

[0130] Effect of Agrocybe aegerita fermentation on puerarin in Pueraria thomsonii and Coix lacryma-jobi

[0131] As Figure 7 known, after fermentation with Agrocybe aegerita, the puerarin content in the fermentation broth of Pueraria thomsonii and Coix lacryma-jobi decreased slightly from 79.58±1.46 μg / mL (0 day) to 72.87±0.61 μg / mL (7 days).

[0132] Effect of Agrocybe aegerita fermentation on phenolic compounds in Pueraria thomsonii and Coix lacryma-jobi

[0133] Table 6 Effect of fermentation time on the content of phenolic compounds in the fermentation broth of Pueraria thomsonii and Coix lacryma-jobi (μg / mL)

[0134]

[0135] Note: Different letters in the table indicate significant differences (P<0.05)

[0136] The content of phenolic compounds in the fermentation broth of Pueraria thomsonii and Coix lacryma-jobi at different fermentation times is shown in Table 6. Generally speaking, Agrocybe aegerita liquid fermentation significantly increased the content of phenolic compounds in Pueraria thomsonii and Coix lacryma-jobi.

[0137] 2. Effect of the addition amount of Agrocybe aegerita fermentation broth of Pueraria thomsonii and Coix lacryma-jobi on the texture quality and in vitro digestibility of noodles

[0138] 2.1 Materials and equipment

[0139] 2.1.1 Source of experimental materials

[0140] Same as step 1.1.1.

[0141] 2.1.2 Experimental reagents

[0142] Table 7 Drugs and reagents

[0143]

[0144] For other reagents, see Step 1.1.2

[0145] 2.1.3 Experimental instruments and equipment

[0146] Table 8 Main instruments and equipment

[0147]

[0148] 2.2 Experimental methods

[0149] 2.2.1 Preparation of Pueraria lobata coix seed enzymatic hydrolysate and fermentation broth:

[0150] The method is shown in Step 1.2.1 and Step 1.2.2. The nutritional value of Pueraria lobata coix seed is the highest after being fermented by Agrocybe aegerita for 4 days. The fermented Pueraria lobata coix seed is passed through a colloid mill and reserved for use.

[0151] 2.2.2 Preparation of Pueraria lobata coix seed noodles:

[0152] Process flow: Prepare flour and fermentation broth → Knead dough → Let the dough rest → Roll out → Cut into strips → Finished product.

[0153] Process description: Basic ingredients: Based on 100 g of the total amount of flour, 0.5% salt, 3% vital wheat gluten, 0.6% gluten strengthening agent, prepare Pueraria lobata coix seed fermentation broth at 0%, 22%, 32%, 42% and 32% Pueraria lobata coix seed enzymatic hydrolysate noodles, and name them N-0%, N-22%, N-32%, N-42% and WN-32% respectively.

[0154] 2.2.3 Determination of noodle texture (TPA)

[0155] Cook the noodles until the optimal time, take them out, drain the surface water with absorbent paper after rinsing with cold water, and place them on the texture analyzer for measurement. Test parameters: Probe T / 10, pre-test speed 2.0 mm / s, test speed 1.0 mm / s, post-test speed 1.0 mm / s, interval 5 s, compression ratio: 70%, trigger force 5 g, each sample is measured 10 times repeatedly.

[0156] 2.2.4 Determination of in vitro starch digestion characteristics of noodles

[0157] Enzyme solution preparation: Take 1 g of porcine pancreatic amylase (140 U / g) and dissolve it in 100 mL of deionized water. After stirring evenly, centrifuge it (10610×g, 10 min), and mix it with 90 μL of amyloglucosidase (100000 U / mL). The mixed enzyme solution is freshly prepared. Mix 0.5 g of the sample with 15 mL of sodium acetate buffer (0.2 M, pH = 5.2) and place it in a centrifuge tube. Add glass beads to the centrifuge tube to prevent the sample from caking. Incubate it in a continuously shaking water bath at 37 °C for 30 min. Then add 10 mL of the mixed enzyme solution and react in a water bath with oscillation at 37 °C. Take 1 mL of the sample hydrolysis solution and 4 mL of absolute ethanol at 0, 20, 30, 60, 90, 120, 150, and 180 min respectively to inactivate the enzymes in the hydrolysis solution. Determine the glucose content at different reaction times by the DNS method. Calculate the contents of rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) using the following equations.

[0158] RDS (%) = (G20 - G0) × 0.9 / TS × 100 (3-1)

[0159] SDS (%) = (G120 - G20) × 0.9 / TS × 100 (3-2)

[0160] RS (%) = TS - (RDS + SDS) / TS × 100 (3-3)

[0161] Wherein, G0, G20, and G120 are the glucose contents at 0, 20, and 120 min of starch hydrolysis time, respectively, in mg; TS is the mass of total starch in the sample, in mg.

[0162] 2.2.5 In vitro starch hydrodynamics model and predicted glycemic index of noodles

[0163] Starch hydrolysis rate = glucose equivalent in the hydrolysis solution at the sampling time point × 0.9 × 100 / total starch content. Draw a starch digestion rate curve with hydrolysis time as the abscissa and starch digestion rate as the ordinate. Use the first-order kinetic model C = C ∞ (1 - e -kt ), where C, C ∞ and k represent the hydrolysis percentage of starch at time t, the maximum hydrolysis constant, and the first-order reaction kinetic constant. Calculate the starch hydrolysis hydrogenation index (HI) through conversion, and calculate the GI value according to formula 3-4.

[0164] GI = 39.71 + 0.549HI (3-4)

[0165] 2.2.6 Determination of short-range ordered structure of noodle starch crystals (FTIR)

[0166] The freeze-dried noodle samples were ground into powder and passed through a 100-mesh sieve for later use. The samples were mixed with dry spectroscopic grade potassium bromide (1:50, w / w), finely ground in an agate mortar, and then the mixture powder was pressed into a transparent thin film for scanning with an infrared spectrometer. Scanning times: 64, scanning wavelength range was 4000 - 400 cm -1 . The Fourier transform infrared spectrum was deconvoluted using OMNIC 8.0 data processing software and Peakfi 4.12 software, and second derivative fitting was performed. And the percentage content of each structure was calculated based on the characteristic peaks of protein secondary structure.

[0167] 2.2.7 Observation of the microscopic morphology of noodles (SEM)

[0168] The dry noodles were cut into cross-sections (about 1.0 cm × 0.4 cm × 0.3 cm), fixed with glutaraldehyde (2.5% / w / w, pH 6.8) at 4°C for 4 h, then dehydrated with 50%, 70%, and 90% ethanol solutions for 15 min each, and dehydrated again with absolute ethanol for 15 min. After dehydration of the samples, they were replaced with tert-butanol once and then freeze-dried. Before testing, the samples were placed on the sample stage with the help of double-sided tape, and the samples were sputter-coated with gold by high-altitude ion spraying method. After gold spraying, the microscopic morphology of the noodles was observed under a scanning electron microscope at a voltage of 10.0 kV.

[0169] 2.2.8 Determination of the crystal structure of noodles (XRD)

[0170] The noodle samples were ground into powder and passed through a 100-mesh sieve for later use. The crystalline structure of the noodle samples was determined using an X-ray diffractometer. The working voltage and current of the X-ray diffractometer were 45 kV and 40 mA respectively, the scanning range was from 5 to 40 (2θ angle range), the step size was 0.013, and the step rate was 0.3 s per step.

[0171] 2.2.9 Determination of the content of free sulfhydryl groups and disulfide bonds in noodles

[0172] The steps for measuring the content of free sulfhydryl groups are as follows: Weigh 250 mg of noodle powder and disperse it in 4.0 mL of 0.2 mol / L Tris-HCl buffer solution (pH 8.0, containing 3.0 mmol / L of EDTA, 8 mol / L of urea, and 2.0% of SDS). After mixing evenly, shake it at room temperature for 2 h, and then centrifuge it at 10610×g for 15 min. Take 4 mL of the supernatant, add 0.5 mL of 0.2 mol / L Tris-HCl buffer solution (pH 8.0, containing 10 mmol / L of 5,5′-dithiobis(2-nitrobenzoic acid)), react it in the dark at room temperature for 20 min, measure the absorbance of the sample at 412 nm, prepare a series of concentrations of L-cysteine, and measure the absorbance values in the same way as above. Convert the absorbance value of the noodle sample into the content of free sulfhydryl groups in the gluten solution through the standard curve.

[0173] The steps for measuring the content of disulfide bonds are as follows: Weigh 10.0 mg of freeze-dried noodle powder and disperse it in 1.0 mL of 0.2 mol / L Tris-HCl buffer solution (pH 8.0, containing 40 mmol / L of DTT), and react it at 60 °C for 2 h. Then add 3 mL of trichloroacetic acid (12% w / v) to stop the reaction, and centrifuge it at 10610×g at -4 °C for 10 min. Remove the supernatant, wash the precipitate twice with trichloroacetic acid (12% w / v), and finally measure the content of sulfhydryl groups in the precipitate. The measurement method is the same as that for the content of free sulfhydryl groups above. Then the content of disulfide bonds is equal to half of the difference between the total sulfhydryl groups and the free sulfhydryl groups.

[0174] 2.2.10 Data processing

[0175] Data analysis is the same as in step 1.2.12.

[0176] 2.3 Results and discussion

[0177] 2.3.1 Influence on noodle texture

[0178] Table 9 Influence of adding fermented liquid of Pueraria thomsonii and Coix lacryma-jobi with different ratios on noodle texture

[0179]

[0180] Note: Different letters in the table indicate significant differences (P<0.05)

[0181] The TPA results of the noodles are shown in Table 9.

[0182] 2.3.2 Analysis of in vitro starch digestion characteristics of noodles

[0183] Table 10 Influence of adding fermented liquid of Pueraria thomsonii and Coix lacryma-jobi with different ratios on the starch content of noodles

[0184]

[0185] Note: Different letters in the table indicate significant differences (P < 0.05). RDS: rapidly digestible starch; SDS: slowly digestible starch; RS: resistant starch; TS: total starch

[0186] The contents of TS, RDS, SDS, and RS of the noodles calculated from formulas (3-1)-(3-3) are recorded in Table 10.

[0187] 2.3.3 In vitro hydrolysis kinetics and predicted glycemic index analysis of noodles

[0188] As Figure 8 can be seen, during the in vitro digestion process, the starch digestibility of the 5 groups of noodle samples increased rapidly in the first 20 minutes, the hydrolysis rate increased slowly from 20 to 80 minutes, and the hydrolysis rate tended to level off after 80 minutes. The starch hydrolysis rate of the noodles was inversely proportional to the proportion of the Puerariae radix and Coix seed fermentation broth. At the digestion end point of 180 minutes, the starch digestibility of the N-0% noodles was the highest (65.93%), followed by the WN-22% sample (50.86%), the N-22% noodles (47.89%), the N-32% noodles (39.78%), and the lowest starch hydrolysis rate was the N-42% noodles (37.34%).

[0189] As Figure 9 shown, the ratio of the fitting curve area of the noodles to white bread was calculated using Origin software, and then the maximum degree of hydrolysis (C ∞ ), kinetic constant (k), hydrolysis index (HI), and pGI of the noodles were calculated through formula (3-4) and recorded in Table 11.

[0190] Table 11 Effects of addition of Puerariae radix and Coix seed fermentation broth at different ratios on starch digestion, first-order kinetic model parameters, hydrolysis index, and predicted glycemic index (pGI) of noodles

[0191]

[0192] Note: Different letters in the table indicate significant differences (P < 0.05). C ∞ : maximum degree of hydrolysis; k: kinetic constant; HI: hydrolysis index; pGI: predicted glycemic index.

[0193] 2.3.4 Short-range ordered molecular structure of noodles

[0194] Figure 10 The infrared spectra of noodles with different contents of Puerariae radix and Coix seed fermentation broth (0%, 22%, 32%, 42%) and 32% Puerariae radix and Coix seed enzyme hydrolysate. From Figure 10It can be seen that the shapes of all spectral peaks of the 5 groups of samples are basically similar, indicating that the addition of the Puerariae semen coicis fermentation broth does not change the chemical groups and conformations of starch.

[0195] As can be seen from the FTIR spectral analysis, the R values of the noodles added with 0%, 22%, 32%, and 42% fermentation broth and 32% enzymolysis solution 1047 / 1022 are 1.015, 1.023, 1.027, 1.006, and 1.017 respectively.

[0196] 2.3.5 Content of protein secondary structure in noodles

[0197] The amide I region in FTIR reflects the secondary structure of proteins. The amide I band region (1600 - 1700 cm -1 ) of the spectrum was analyzed using Peakfit software, and two-point baseline correction was performed. The Gaussian curve fitting method was used to fit the spectrum, and multiple fittings were carried out to minimize the residuals in order to fully distinguish different bands and analyze the content of each secondary structure. The secondary structures of proteins include β-sheet structure (1600 - 1640 cm -1 ), random coil (1640 - 1650 cm -1 ), α-helix structure (1650 - 1660 cm -1 ), and β-turn structure (1660 - 1700 cm -1 )(Cai et al., 2022).

[0198] Table 12 Effects of adding Puerariae semen coicis fermentation broth at different ratios on the secondary structure of noodles

[0199]

[0200] Note: Different letters in the table indicate significant differences (P < 0.05)

[0201] The effects of adding Puerariae semen coicis fermentation broth at different ratios on the secondary structure of noodles are shown in Table 12. The results show that the secondary structure of the protein in the noodles added with Puerariae semen coicis fermentation broth is mainly dominated by the β structure, and the increase in the content of α helix will affect the elasticity of the dough to a certain extent.

[0202] 2.3.6 Microscopic morphology analysis of noodles

[0203] Overall observation of the cross-section microstructure of noodles magnified 1000 times. As Figure 11 can be seen, after adding an appropriate amount of Puerariae semen coicis fermentation broth, the quality of the noodles is improved.

[0204] 2.3.7 Analysis of the starch crystal structure of noodles

[0205] Figure 12X-ray diffraction patterns of noodles with different contents (0, 22%, 32%, 42%) of Pueraria thomsonii and Coix lacryma-jobi fermentation broth and 32% Pueraria thomsonii and Coix lacryma-jobi enzymolysis broth.

[0206] The diffraction peaks of the samples containing Pueraria thomsonii and Coix lacryma-jobi fermentation broth and enzymolysis broth were higher than those of the N-0% sample group, and the crystalline region was complete, indicating that the samples added with Pueraria thomsonii and Coix lacryma-jobi had a higher crystallinity, especially when the content of Pueraria thomsonii and Coix lacryma-jobi fermentation broth was 22% and 32%.

[0207] 2.3.8 Analysis of the content of free sulfhydryl groups and disulfide bonds in noodles

[0208] Table 13 Effects of adding different proportions of Pueraria thomsonii and Coix lacryma-jobi fermentation broth on the free sulfhydryl groups and disulfide bonds of noodles

[0209]

[0210] Note: Different letters in the table indicate significant differences (P<0.05)

[0211] The content of free sulfhydryl groups in noodles added with different Pueraria thomsonii and Coix lacryma-jobi fermentation broth is shown in Table 13. As can be seen from Table 13, the higher the content of disulfide bonds in noodles, the higher the degree of intermolecular crosslinking, which can improve the quality of noodles.

[0212] 3. Effects of adding Pueraria thomsonii and Coix lacryma-jobi fermentation broth on the nutritional and functional quality of noodles

[0213] 3.1 Materials and instruments

[0214] 3.1.1 Experimental instruments and reagents

[0215] For other instruments and reagents, please refer to Steps 1.1.2, 1.1.3, 2.1.2 and 2.1.3.

[0216] 3.1.2 Experimental materials

[0217] For materials, please refer to Step 1.1.1.

[0218] 3.2 Experimental methods

[0219] 3.2.1 Preparation of noodles

[0220] For the preparation of noodles, please refer to Step 2.2.2.

[0221] 3.2.2 Determination of noodle color difference

[0222] After grinding the noodle samples into powder, sieve them through 100 meshes for standby. Take 50 g of the sample and spread it flat on the test bench. After calibrating the color difference meter, measure the L* (brightness value), a* (redness value), and b* (yellowness value) of the noodles, and measure 5 times in parallel and take the average value.

[0223] 3.2.3 Determination of noodle cooking characteristics

[0224] (1) Optimal cooking time: Weigh 25 noodles of the same length, put them into 600 mL of boiling water and cook for 2 min. After 2 min, take out one noodle every 30 s, place it in cold water for 30 s. When there is no white core, it is the optimal cooking time of the noodles.

[0225] (1) Determination of water absorption rate: Weigh 25 noodles of the same length, then put them into a pot with 600 mL of boiling water and cook for 4 min. Take them out and let them stand for 3 min, then weigh them. The water absorption rate is calculated according to the following formula: Water absorption rate % = (mass of cooked noodles - mass of raw noodles) / mass of raw noodles × 100%.

[0226] (2) Determination of breakage rate: Weigh 25 noodles of the same length, then put them into a pot with 600 mL of boiling water and cook for 4 min. Take them out and drain the water, record the number of complete noodles. The breakage rate formula is as follows: Breakage rate % = (total number - number of complete noodles) / total number × 100%.

[0227] (3) Determination of cooking loss: Weigh 25 noodles of the same length and put them into 200 mL of boiling water. After 4 min, take them out. Make the remaining noodle soup up to 200 mL, mix well and take 100 mL of the noodle soup. Evaporate it to dryness on an electric furnace and then dry it to a constant weight in an oven at 105 °C. The cooking loss rate is calculated according to the following formula: Cooking loss rate % = mass of dry matter in noodle soup × 2 / mass of raw noodles × 100%.

[0228] 3.2.4 Sensory evaluation of noodles

[0229] Cook the noodles until the optimal cooking time, take them out and cool. Conduct sensory evaluation in a food laboratory with sufficient light and good ventilation. Select 20 food professionals for sensory evaluation. The sensory evaluation method of noodles refers to the standard SB / T 10137 - 1993.

[0230] 3.2.5 Determination of antioxidant activity of noodles

[0231] The determination of antioxidant activity of noodles is the same as in step 1.2.5.

[0232] 3.2.6 Determination of free amino acids in noodles

[0233] Weigh 1 g of the sample, extract it with 50 mL of 0.01 mol / L hydrochloric acid for 30 min. After shaking well, take 10 mL of the mixed solution and centrifuge it at 8000 × g for 10 min. Then take 2 mL of the supernatant into a centrifuge tube, add 2 mL of 8% sulfosalicylic acid, mix well, let it stand for 15 min, filter it with a 0.22 μm filter membrane and then analyze it on a machine. Use an S - 433D automatic amino acid analyzer to determine the free amino acids in the noodles.

[0234] 3.2.7 Determination of volatile compounds in noodles

[0235] Sample treatment and extraction conditions: Take 5.0 g of noodle sample powder and place it in the headspace vial (Pegasus HRT 4D Plus, USA) of a comprehensive two-dimensional gas chromatography-high throughput high-resolution mass spectrometer with a volume of 20 mL. At the same time, add 1 μL of 2-methyl-3-heptanone (5 g / L) as an internal standard to the headspace vial. Insert the aged 50 / 30 μm CAR / PDMS / DVB extraction head into the headspace of the sample vial, adsorb at 50 °C for 30 minutes. After adsorption, take out the extraction head and insert it into the gas chromatography injection port, desorb at 250 °C for 3 minutes, and start the instrument for data acquisition simultaneously.

[0236] Gas phase conditions: Use a DB-Wax (30 m × 0.25 mm × 0.25 m) capillary column. The heating program is as follows: The initial temperature of the column oven is 40 °C, maintained for 3 minutes, then heated to 230 °C at a rate of 10 °C / min and held for 6 minutes. The carrier gas is helium (1 mL / min), and the injector and detector temperatures are 250 °C.

[0237] Mass spectrometry conditions: Electron impact ionization source (EI), electron energy 70 eV. The ion source temperature is set to 200 °C, and the interface temperature is maintained at 250 °C. The identification method of volatile compounds is to compare their mass spectra with the standard spectra in the NIST2020.L MS library of the National Institute of Standards and Technology of the United States. Qualify the substances by comparing the retention indices and mass spectra of each component. The content of each volatile substance is expressed by its relative peak area.

[0238] Determination of key flavor substances in noodles: The absolute concentration of flavor substances in noodle samples can only reflect the content of volatile compounds and cannot fully and truly reflect the strength and quality of the sample aroma. Although the concentration of some flavor substances in the sample is high, their thresholds are high, and their contribution to the overall flavor is not significant. Therefore, when judging the role of a substance in the sample aroma, the concentration and threshold of the flavor substance should be considered comprehensively. Therefore, the odor activity value (OAV) is used to intuitively evaluate the influence effect of specific flavor substances. OAV is the ratio of the concentration of the flavor substance to its threshold. The calculation formula is as follows: OAVi = Ci / OT

[0239] In the formula: Ci is the concentration (μg / kg) of volatile component i, and OT is the corresponding flavor threshold (μg / kg)

[0240] 3.2.8 Determination of bioactive substances in noodles

[0241] The detection of bioactive substances is the same as in steps 1.2.4, 1.2.8, 1.2.9, and 1.2.10.

[0242] 3.2.9 Data analysis

[0243] The data analysis is the same as in Step 1.2.12.

[0244] 3.3 Results and Discussion

[0245] 3.3.1 Effects of Puerariae Radix and Coix Seed Fermentation Broth on Noodle Color

[0246] It can be seen from Figure 13 that there are significant differences in the color of different noodle samples after adding Puerariae Radix and Coix Seed Fermentation Broth at different ratios (P < 0.05). Compared with N-0% noodles, the L* values of N-22%, N-32%, N-42%, and WN-32% noodles decrease with the increase of Puerariae Radix and Coix Seed Fermentation Broth. The L* value of the N-42% sample is the lowest, at 86.84, still within the acceptable range. This situation may be caused by the colors of Puerariae Radix and Coix Seed themselves. The gradual decrease of the b* value within a certain range indicates a decrease in the yellowness value of the noodles. When 42% of the fermentation broth is added, the b* value is 6.75, and the yellowness of the noodles reaches the lowest, with a significant difference. The a* value increases with the increase of the proportion of Puerariae Radix and Coix Seed Fermentation Broth, indicating that after adding Puerariae Radix and Coix Seed, the redness value of the noodles increases.

[0247] 3.3.2 Effects of Puerariae Radix and Coix Seed Fermentation Broth on Noodle Cooking Characteristics

[0248] Table 14 Effects of Adding Puerariae Radix and Coix Seed Fermentation Broth on Noodle Cooking Characteristics

[0249]

[0250] Note: Different letters in the table indicate significant differences (P < 0.05)

[0251] It can be seen from Table 14 that adding Puerariae Radix and Coix Seed Fermentation Broth and enzymolysis broth has certain effects on the cooking time, cooking loss rate, and water absorption rate of noodles.

[0252] 3.3.3 Effects of Puerariae Radix and Coix Seed Fermentation Broth on Noodle Sensory Quality

[0253] Table 15 Effects of Adding Different Proportions of Puerariae Radix and Coix Seed Fermentation Broth on Noodle Sensory Quality

[0254]

[0255] Note: Different letters in the table indicate significant differences (P < 0.05)

[0256] As can be seen from Table 15, there are significant differences (P<0.05) in the color, texture, palatability, and toughness between the wheat noodles (N-0% sample) and the noodles added with different proportions of kudzu root coix seed fermentation broth. After adding the kudzu root coix seed fermentation broth, the palatability and toughness of the noodles are significantly improved, both being better than those of the wheat noodles (N-0% sample). It can be seen that the noodles made by adding 22% and 32% of the kudzu root coix seed fermentation broth and the enzymolysis solution are rich in nutrients and have a relatively high acceptance in sensory evaluation.

[0257] 3.3.4 Effect of Kudzu Root Coix Seed Fermentation on the Antioxidant Activity of Noodles

[0258] The antioxidant activities of 5 noodle samples were compared by two different methods (DPPH and ABTS scavenging activities), as Figure 14 shown. It can be seen that the noodles made by adding the kudzu root coix seed fermentation broth and the enzymolysis solution can achieve antioxidant effects to a certain extent.

[0259] 3.3.5 Effect of Kudzu Root Coix Seed Fermentation Broth on Free Amino Acids in Noodles

[0260] The amino acid contents and compositions of N-0% noodles, N-22% noodles, N-32% noodles, N-42% noodles, and WN-32% noodles are shown in Table 16.

[0261] Table 16 Effect of Adding Kudzu Root Coix Seed Fermentation Broth on the Amino Acid Content and Composition of Noodles (mg / 100g)

[0262]

[0263] Note: Different letters in the table indicate significant differences (P<0.05), and * indicates essential amino acids

[0264] 3.3.6 Effect of Kudzu Root Coix Seed Fermentation Broth on the Volatile Flavors of Noodles

[0265] The noodle samples were analyzed by GC-MS, and the contents of volatile flavor substances are summarized in Figure 15 . It shows that adding the kudzu root coix seed fermentation broth increases the content of ester volatile flavor substances in the noodles.

[0266] 3.3.7 Contribution Degree and Flavor Presentation of Volatile Flavor Components in Kudzu Root Coix Seed Noodles

[0267] The overall flavor characteristics of noodles are jointly determined by the concentrations of various volatile flavor components and their corresponding sensory thresholds. The contribution degree of noodles' flavor is characterized by the OAV values of different volatile flavor substances. Among all the detected volatile flavor substances, 49 substances with aroma characteristics were selected. It was found that the larger the OAV value, the greater the overall contribution to the sample. Generally, components with OAV > 1 are considered key flavor substances of the sample, and components with 0.1 ≤ OAV < 1 have a modifying effect on the overall flavor of the noodle sample. After adding kudzu root and coix seed, 2-n-amyl furan contributes fruity flavors such as bean flavor and green flavor, and 1-octen-3-ol and γ-nonalactone contribute mushroom flavor, coconut and peach flavors to the noodles.

[0268] 3.3.8 Effects of the fermented liquid of kudzu root and coix seed on the bioactive substances of noodles

[0269] 3.3.8.1 Puerarin

[0270] Figure 16 The determination results (P < 0.05) of the puerarin content in wheat noodles (N-0%) and 4 kinds of noodles added with the fermented liquid and enzymolysis liquid of kudzu root and coix seed are shown. It can be seen that the puerarin content in the noodle sample added with 32% of the enzymolysis liquid of kudzu root and coix seed is 9.67 μg / g.

[0271] 3.3.8.2 GABA

[0272] As Figure 16 can be seen, after adding the fermented liquid of kudzu root and coix seed, the GABA content in the noodles increases and is proportional to the addition amount, and GABA is not detected in the N-0% sample.

[0273] 3.3.8.3 Total flavonoids

[0274] As Figure 16 can be seen, compared with the wheat noodles (N-0% sample) without adding the fermented liquid and enzymolysis liquid of kudzu root and coix seed, with the increase of the addition amount of the fermented liquid and enzymolysis liquid of kudzu root and coix seed, the flavonoid content in the noodle sample also shows a significant upward trend, and their total flavonoid content is significantly higher than that of the N-0% sample.

[0275] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A preparation method of kudzu root coix seed fermented liquid noodles, characterized in that, it comprises the following steps: 1) Prepare kudzu root coix seed fermented liquid; 2) Mix the prepared kudzu root coix seed fermented liquid with flour, and successively carry out dough kneading, dough proofing, rolling and noodle cutting operations to finally obtain kudzu root coix seed fermented liquid noodles; The specific preparation method of the kudzu root coix seed fermented liquid comprises the following steps: (1) Select coix seeds, treat the coix seeds with NaClO solution, then rinse them several times with deionized water, add 10 times the volume of deionized water, soak them in an incubator at 36 °C for 10 h, and then spread the soaked coix seed grains between double-layer gauze, and germinate them in an incubator at 29 °C and 95% relative humidity in the dark for 24 h. After the germination is completed, germinated coix seeds are obtained; (2) Grind the germinated coix seeds and kudzu root into slurries by adding water at a mass concentration ratio of 1:6 respectively, then carry out gelatinization respectively. After the gelatinization is completed, add thermostable amylase and carry out a water bath at 85 °C for 50 min, then cool. After cooling, add saccharifying enzyme respectively and carry out a water bath at 65 °C for 50 min until saccharification is complete, take out and inactivate the enzyme on an induction cooker to obtain coix seed enzymatic hydrolysate and kudzu root enzymatic hydrolysate respectively; (3) Mix the coix seed enzymatic hydrolysate and kudzu root enzymatic hydrolysate in equal proportions to obtain kudzu root coix seed enzymatic hydrolysate; Sterilize the kudzu root coix seed enzymatic hydrolysate at 121 °C for 20 min, cool it to room temperature, inoculate 4% of edible mushroom seed liquid, and continuously ferment it in a shaker for 7 d to obtain kudzu root coix seed fermented liquid; In step (3), the edible mushroom is Agrocybe aegerita; In step 2), the addition amount of the kudzu root coix seed fermented liquid is 22%-32%.

2. The preparation method of kudzu root coix seed fermented liquid noodles according to claim 1, characterized in that, in step (1), the mass concentration of the NaClO solution is 0.1%, and the treatment time of the coix seeds with the NaClO solution is 30 min.

3. The preparation method of kudzu root coix seed fermented liquid noodles according to claim 1, characterized in that, in step (2), the gelatinization time is 20 min.

4. The preparation method of kudzu root coix seed fermented liquid noodles according to claim 1, characterized in that, in step (2), the dosage of thermostable amylase is 100 U / g, and the dosage of saccharifying enzyme is 200 U / g.

5. The preparation method of kudzu root coix seed fermented liquid noodles according to claim 1, characterized in that, in step (3), the parameters of the shaker fermentation process are 27 °C and 170 r / min.

6. A kudzu root coix seed fermented liquid noodle prepared by using the preparation method of kudzu root coix seed fermented liquid noodles according to any one of claims 1-5.

Images