Modified walnut protein and walnut milk containing same

Abstract

A modified walnut protein and walnut milk containing same. The modified walnut protein is prepared by sequentially subjecting a walnut protein solution to a high-pressure microfluidization homogenization treatment and a trypsin treatment.

Description

A modified walnut protein and walnut milk containing it Technical Field

[0001] This invention relates to the field of deep processing technology of agricultural and sideline products, and in particular to a modified walnut protein and walnut milk containing it. Background Technology

[0002] Walnut protein contains 18 amino acids, including 8 essential amino acids. Its amino acid content is rich and balanced, making it a high-quality source of plant protein, thus possessing high economic and nutritional value. Walnut protein is mainly derived from walnut meal, a byproduct of walnut oil processing. Walnut meal is often used as animal feed or discarded, failing to be fully utilized and resulting in significant resource waste. The main reason is its poor functional properties; for example, gluten accounts for over 70% of walnut protein, leading to poor water solubility and consequently poor emulsifying and foaming properties, severely limiting its application in food.

[0003] Currently, there are few reports on research on improving the functional properties of walnut protein during walnut processing. The patent with patent number 201410076807.3 uses protease to defatted walnut powder for restricted enzymatic hydrolysis, thereby improving the solubility of walnut protein. This process uses a single enzyme to modify walnut protein, which has problems such as high cost and long processing time. Therefore, the improvement of the functional properties of walnut protein by modifying it with a single enzyme cannot be industrialized. Summary of the Invention

[0004] In view of this, the present invention provides a green method to improve the solubility of walnut protein, namely, to modify walnut protein by enzymatic hydrolysis and physical modification to improve the solubility of walnut protein. This method does not introduce chemical reagents and can reduce the high cost of single enzymatic hydrolysis, making it more suitable for industrial production.

[0005] First, the present invention provides a modified walnut protein, which is prepared by sequentially subjecting a walnut protein solution to high-pressure microfluidic homogenization and trypsin treatment.

[0006] Preferably, the pressure of the high-pressure microjet homogenization treatment is 150-200 MPa, more preferably 160-180 MPa; the number of times the high-pressure microjet homogenization treatment is performed is 1-3 times.

[0007] Most preferably, the pressure of the high-pressure microjet homogenization treatment is 180 MPa, and the number of times is 3.

[0008] Under the above conditions of high-pressure microfluidic homogenization treatment, the particle size of walnut protein is further reduced, which is beneficial to further improving solubility.

[0009] Preferably, the concentration of the walnut protein solution is 5%-10%.

[0010] By controlling the concentration of the walnut protein solution to 5%-10%, it can be ensured that no clogging occurs during high-pressure microfluidic homogenization.

[0011] Preferably, the trypsin treatment step includes:

[0012] The walnut protein solution, homogenized by high-pressure microfluidic jet, was mixed with trypsin at a dosage of 900-1200 U per gram of walnut protein. The mixture was then enzymatically hydrolyzed for 20-50 minutes at 40-50°C and pH 7.5-8.2 to obtain the hydrolysate. The hydrolysate was then inactivated at 90-100°C for 5-15 minutes to obtain the modified walnut protein.

[0013] After the enzymatic hydrolysis reaction, the enzyme needs to be inactivated in time to ensure that the protein is not over-hydrolyzed and produces bitter peptides.

[0014] Furthermore, the present invention provides a walnut milk containing the modified walnut protein described above.

[0015] Preferably, the walnut milk raw material further includes an oil phase; the oil phase includes at least one of corn oil and walnut oil.

[0016] Preferably, the walnut milk raw material further includes additives; the additives include emulsifiers, stabilizers, and sweeteners;

[0017] The emulsifier is at least one of mono- and diglycerides, sucrose fatty acid esters, and sodium caseinate.

[0018] The stabilizer is at least one of xanthan gum, carrageenan, and carboxymethyl cellulose.

[0019] The sweetener is at least one of maltodextrin, sucralose, and xylitol.

[0020] Preferably, the walnut milk raw material comprises, by weight percentage: 3.2%-6.4% modified walnut protein, 1%-5% oil phase, 0.04%-0.3% mono- and diglycerides, 0.04%-0.14% sodium caseinate, 0.1%-0.5% xanthan gum, 2%-8% maltodextrin, 0.01%-0.1% flavoring, and 0.001%-0.01% sucralose.

[0021] The appropriate types and dosage ranges of oil phases and additives mentioned above ensure that the walnut milk has a good appearance, good stability, and a good taste. Using corn oil and / or walnut oil as the oil phase in the high-protein walnut milk ensures a harmonious flavor and pure aroma.

[0022] Preferably, the modified walnut protein content is 3.8% to 4.2%.

[0023] When the amount of modified walnut protein used is within the above range, the sensory evaluation of the prepared walnut milk is optimal.

[0024] Furthermore, the present invention provides a method for preparing the walnut milk, comprising: mixing the modified walnut protein with an oil phase and additives, and then subjecting it to sterilization, high-speed shearing, and high-pressure homogenization to obtain the milk.

[0025] Preferably, the sterilization temperature is 70-90℃ and the sterilization time is 15-30 min; and / or, the high-speed shearing speed is 8000-12000 rpm and the time is 1-5 min; and / or, the high-pressure homogenization pressure is 20-40 MPa and the homogenization is performed 1-3 times.

[0026] In the preparation of high-protein walnut milk, pre-mixing additives beforehand ensures faster and more uniform dispersion throughout the system. High-speed shearing then homogenizes the liquid, causing aggregates to break down into smaller, uniform aggregates. High-pressure homogenization further expands the contact area between protein and water, thus improving the stability of the walnut milk. This ensures the walnut milk has a suitable particle size, resulting in an acceptable taste and appearance.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention provides a greener, more environmentally friendly, shorter-processing-time, and lower-cost method to improve the solubility of walnut protein. The resulting highly soluble modified walnut protein is used to prepare walnut milk rich in protein, expanding the market for walnut protein in industrial food production and showing broad application prospects.

[0029] The walnut milk provided by this invention is rich in protein, low in fat, and has good stability. It also has a good taste, meeting consumers' needs for walnut milk with balanced nutrition and a balanced amino acid ratio. Attached Figure Description

[0030] Figure 1 shows the TSI of different walnut milks.

[0031] Figure 2 is a CLSM diagram of walnut milk from Example 6.

[0032] Figure 3 is a CLSM diagram of walnut milk from Example 7.

[0033] Figure 4 is a CLSM diagram of walnut milk from Example 8.

[0034] Figure 5 is the CLSM diagram of walnut milk in Comparative Example 1.

[0035] Figure 6 is the CLSM diagram of walnut milk in Comparative Example 2.

[0036] Figure 7 is a statistical chart of the protein content of different walnut milks. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] Unless otherwise specified, specific techniques or conditions in the embodiments shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Instruments and other equipment whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels. Unless otherwise specified, the methods described are conventional methods, and the raw materials described are all obtainable through publicly available commercial channels. The walnut protein in the following embodiments is from Xi'an Guohao Biotechnology Co., Ltd., and the flavoring is from Givaudan Flavors & Fragrances Co., Ltd. The percentages (%) in the following embodiments represent weight percentages.

[0039] Examples 1-5

[0040] This embodiment provides a modified walnut protein, prepared by the following method:

[0041] An 8% walnut protein solution was homogenized using a high-pressure microfluidic jet. The homogenization conditions are shown in Table 1. Then, trypsin was added to the homogenized protein solution at a concentration of 1000 U / g. Enzymatic hydrolysis was performed at 45℃ for 25 min at pH 8.0. After hydrolysis, the hydrolysate was heated to 95℃ and held for 10 min to inactivate the enzyme, yielding modified walnut protein. The solubility, particle size, and potential of the modified walnut protein are shown in Table 1.

[0042] The solubility test method was as follows: a 1% (w / v) walnut protein solution was prepared using distilled water. The solution was vortexed for 2 min, and then each sample was centrifuged at 6000 × g for 10 min at 20 °C. The protein content in the supernatant was determined using the Lowry method, with bovine serum albumin (BSA) as the standard, and the protein concentration was calculated (y = 0.3121x + 0.0568, R...). 2 =0.9949, where x is protein concentration and y is absorbance.

[0043] The particle size and potential were measured as follows: the modified 8% protein solution was diluted to 0.1%, and then the diluted sample was slowly poured into the measuring vessel to prevent air bubbles from forming. The particle size and zeta potential of the sample were measured at room temperature using a Malvern nanoparticle size potentiostat. The equilibration time was 2 min. The refractive indices of the dispersed phase and the dispersant were 1.45 and 1.33, respectively, and the absorbance was 0.001.

[0044] Table 1

[0045] Example 6

[0046] This embodiment uses the modified walnut protein prepared in Example 4 above to prepare walnut milk, and the steps are as follows:

[0047] (1) Weigh 50% of the 8% modified walnut protein solution (4% modified walnut protein), add 3% walnut oil, 0.24% mono- and diglycerides, 0.12% sodium caseinate, 0.3% xanthan gum, 6% maltodextrin, 0.005% sucralose and water (% balance), mix evenly, heat and stir at 80℃ for 15 min and sterilize to obtain the mixed liquid;

[0048] (2) The sterilized mixture was subjected to high-speed shearing at 10,000 rpm for 2 minutes;

[0049] (3) Add 0.05% flavoring to the mixture and homogenize it twice under high pressure; the first homogenization pressure is 25 MPa and the second homogenization pressure is 35 MPa to obtain walnut milk.

[0050] Example 7

[0051] This embodiment uses the modified walnut protein prepared in Example 4 to prepare walnut milk. The only difference between this embodiment and Example 6 is the following steps:

[0052] Weigh out 75% of the 8% modified walnut protein solution (6% modified walnut protein).

[0053] Example 8

[0054] This embodiment uses the modified walnut protein prepared in Example 4 to prepare walnut milk. The only difference between this embodiment and Example 6 is the following steps:

[0055] Weigh out 40% of the 8% modified walnut protein solution (modified walnut protein 3.2%).

[0056] Comparative Example 1

[0057] This comparative example provides a walnut milk, the only difference from Example 6 being:

[0058] The modified walnut protein was replaced with an equal amount of commercially available walnut protein powder.

[0059] Comparative Example 2

[0060] This comparative example provides a commercially available walnut milk product.

[0061] Test case

[0062] The TSI of walnut milk tested in Examples 6-8 and Comparative Examples 1 and 2 was determined by placing the sample in a cylindrical glass bottle and performing a light scattering test. After standing for 10 minutes, the sample was scanned within a range of 2 to 45 mm. The entire measurement process took 24 hours. The backscattered light (BS) curve of the turbine stability curve was obtained, and the turbine stability index (TSI) was derived from this curve. The test results are shown in Figure 1.

[0063] The microstructure of the walnut milk in Examples 6-8 and Comparative Examples 1 and 2 was further characterized using confocal laser scanning microscopy (CLSM), and the results are shown in Figures 2-6.

[0064] Furthermore, the protein content of 15g of walnut milk was tested using the Kjeldahl method in GB5009.5-2016, and the results are shown in Figure 7.

[0065] Furthermore, a total of 19 professionally trained personnel conducted sensory evaluations on the walnut milk from Examples 6-8 and Comparative Examples 1 and 2. The sensory evaluation criteria are shown in Table 2, and the sensory evaluation results are shown in Table 3. Among them, the indicators such as color and appearance, smell, taste, mouthfeel, and overall acceptability refer to the national standard (GBT31325-2014).

[0066] Table 2

[0067] Table 3

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. Industrial applicability

[0069] This invention provides a modified walnut protein and walnut milk containing it. The modified walnut protein is obtained by sequentially subjecting a walnut protein solution to high-pressure microfluidic homogenization and trypsin treatment. This green, environmentally friendly, short-processing, and low-cost method can improve the solubility of walnut protein. The resulting highly soluble modified walnut protein can be used to prepare walnut milk rich in protein, expanding the market for walnut protein in industrial food production.

Claims

1. A modified walnut protein, characterized in that, It is prepared by sequentially subjecting a walnut protein solution to high-pressure microfluidization homogenization treatment and trypsin treatment.

2. The modified walnut protein of claim 1, wherein, The high-pressure microfluidization homogenization treatment has a pressure of 150-200 MPa, preferably 160-180 MPa, and is performed 1-3 times.

3. The modified walnut protein of claim 1, wherein, The walnut protein solution has a concentration of 5%-10%.

4. The modified walnut protein of claim 1, wherein, The trypsin treatment comprises the following steps: The walnut protein solution after high-pressure microfluidization homogenization treatment is mixed with trypsin, 900-1200 U of trypsin is added per gram of the walnut protein solution, and then the mixture is subjected to enzymolysis at a temperature of 40-50℃ and a pH of 7.5-8.2 for 20-50 min to obtain an enzymolysis solution; and then the enzymolysis solution is subjected to enzyme inactivation treatment at 90-100℃ for 5-15 min to obtain the modified walnut protein.

5. A walnut milk, characterized by, The modified walnut protein is as claimed in any one of claims 1-4.

6. The walnut milk according to claim 5, characterized in that, The raw material further comprises an oil phase; the oil phase comprises at least one of corn oil and walnut oil.

7. The walnut milk according to claim 6, characterized in that, The raw material further comprises an additive; the additive comprises an emulsifier, a stabilizer and a sweetener. The emulsifier is at least one of monoglyceride, diglyceride, sucrose fatty acid ester and sodium caseinate. The stabilizer is at least one of xanthan gum, carrageenan and carboxymethyl cellulose. The sweetener is at least one of malt dextrin, sucralose and xylitol.

8. The walnut milk according to claim 7, characterized in that, The raw material comprises, by weight percentage: the modified walnut protein 3.2%-6.4%, the oil phase 1%-5%, monoglyceride 0.04%-0.3%, sodium caseinate 0.04%-0.14%, xanthan gum 0.1%-0.5%, malt dextrin 2%-8%, essence 0.01%-0.1% and sucralose 0.001%-0.01%.

9. The method of claim 7 or 8, wherein the walnut milk is prepared by the steps of: The method comprises the following steps: The modified walnut protein is mixed with the oil phase and the additive, and then subjected to sterilization, high-speed shearing and high-pressure homogenization treatment to obtain the product.

10. The method of claim 9, wherein, The sterilization temperature is 70-90℃, and the sterilization time is 15-30 min; and / or, the high-speed shearing has a rotation speed of 8000-12000 rpm and a time of 1-5 min; and / or, the high-pressure homogenization has a pressure of 20-40 MPa and is performed 1-3 times.

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