Preparation method of crisp nut sticks based on two-stage gradient baking

Abstract

The invention discloses a preparation method of crisp nut sticks based on two-stage gradient baking, which comprises the following steps: performing primary baking on raw materials at a lower temperature, performing secondary baking at a higher temperature, putting the baked raw materials and isomaltooligosacharide into vacuum boiling equipment, and performing low-temperature vacuum boiling to obtain the nut sticks. The nut stick prepared by the method has the characteristics of low hardness and crispness, is not bitter and astringent, and is rich in fragrance. The crispness of the nut bar is improved by combining two times of baking with vacuum boiling, the purpose of the first time of baking is to release moisture in the nut bar without causing excessive coking of the surface, and the second time of baking enables the surface to be coked under the action of high temperature under the condition that the baking temperature is increased and moisture is further released under the action of the first time of baking, so that the crispness of the nut bar is improved. Therefore, the brittleness is improved, the hardness is reduced, and the problem that the taste is affected due to the fact that the surface is coked and the core moisture is remained in the traditional one-time baking process and the nuts are hardened is solved.

Description

Technical Field

[0001] The invention belongs to the field of food processing, and in particular relates to a method for preparing a crispy nut bar based on two-stage gradient baking. Background Art

[0002] Nuts are dried fruits with one seed (rarely two). Their ovary walls are very hard when ripe, and the seeds are unattached or free within the ovary wall. Nuts are rich in various nutrients and bioactive substances, including fat, protein, dietary fiber, vitamins (such as vitamin E, niacin, and folic acid), minerals (such as magnesium, potassium, calcium, and phosphorus), carotenoids, plant sterols, and antioxidant phenols. Eating nuts in moderation can effectively reduce the risk of chronic diseases such as cardiovascular disease and diabetes. They are especially suitable for elderly people who need nutritional supplements and have weakened digestive function.

[0003] Currently, the majority of nut snacks on the market are dried products, which are mainly edible after the kernels are air-dried. Due to the hardness of the kernels, the body cannot absorb too much of the nutrients when eating, resulting in a waste of the nuts' nutrients. This is especially true for the elderly, who have poor teeth and cannot meet their needs for light chewing.

[0004] As an emerging portable nutritional food, nut bars are gradually entering the market. They are made by mixing nut particles with syrup (such as maltose syrup, honey) and adhesives (such as whey protein, plant gum), and then pressing and molding them into a stick-shaped structure, which combines nutrition and convenience. However, existing nut bars are usually prepared by pre-treating the raw materials (baking or crushing) and then mixing and molding them. In order to maintain the stability of the product results, it is usually necessary to add a higher proportion of syrup or adhesive to the product. The addition of syrup or adhesive can easily lead to high hardness and poor chewing of the nut bars. In addition, the high oil content in nuts is prone to oxidation and rancidity under hot and humid processing environments, and the high water activity of the syrup accelerates the growth of microorganisms, resulting in problems such as a short shelf life for nut bars. For example, patent CN115053950A discloses a method for producing a high-dietary fiber composite nut bar. By adjusting the formula of the nut bar, a nut bar with both flavor and taste is prepared using four-sided joint extrusion molding technology and multi-channel packaging technology. Although the patent does not mention the crispness, hardness and shelf life of the nut bar, the nuts themselves are relatively hard, and the patent does not provide a method for improving the hardness and brittleness and shelf life of the nuts. The prepared nut bar will have problems such as poor hardness and brittleness and a short shelf life. Patent CN113575883B discloses a method for preparing a crayfish nut bar. A crayfish nut bar with an extended shelf life is prepared by selecting a combination of multiple raw materials and adding antioxidants such as vitamins. Although this method can extend the shelf life of the nut bar, the nut bar also has problems such as poor hardness and brittleness, and cannot meet the requirements of light chewing of the elderly.

[0005] Therefore, how to improve the hardness and brittleness of nut bars to meet the requirements of light chewing by the elderly and at the same time extend the shelf life of nut bars has become an urgent problem to be solved in this field. Summary of the Invention

[0006] In response to the above-mentioned problems, the purpose of the present invention is to provide a method for preparing crispy nut bars based on two-stage gradient baking to obtain nut bars with low hardness, high brittleness and extended shelf life, so as to solve the problems of poor hardness and brittleness and short shelf life of nut bars prepared by existing methods.

[0007] To achieve the above objectives, the present invention first provides a method for preparing a crispy nut bar based on two-stage gradient baking, the specific steps of which are as follows:

[0008] S1: Raw material preparation: prepare nuts or seeds raw materials;

[0009] S2: Primary baking: Place the raw materials prepared in step S1 into an oven, bake once, and then ventilate until completely cooled.

[0010] S3: Secondary baking: The completely cooled raw materials in S2 are placed in an oven for secondary baking;

[0011] S4: Nut bar preparation: Use a vacuum syrup cooker to prepare syrup, with a sugar (isomaltooligosaccharide) to water ratio of 1:1-2, and cook at 80-100°C for 8-12 minutes under vacuum conditions of 0.01-0.08 MPa; then add the nut raw materials in S3 to the vacuum cooker, with the nut raw materials and isomaltooligosaccharide added in a ratio of 80-100 parts:15-25 parts, and mix under vacuum conditions;

[0012] S5: Pressing and molding: Put the raw materials in S4 into a mold, press and mold, cool for 1-2 hours, cut and mold to obtain a nut bar product.

[0013] In one embodiment of the present invention, the nut or seed raw material in step S1 includes at least one of almonds, cashews, walnuts, pumpkin seeds, pistachios, chia seeds, hazelnuts, pine nuts, and almonds.

[0014] In one embodiment of the present invention, the nut or seed raw materials in step S1 include at least one or more of 6-8 parts of almonds, 11-20 parts of cashews, 5-8 parts of walnuts, 6-12 parts of pumpkin seeds, 5-8 parts of pistachios, 2-5 parts of chia seeds, 4-6 parts of hazelnuts, 3-5 parts of pine nuts, and 4-7 parts of almonds, calculated by weight.

[0015] In one embodiment of the present invention, the temperature of the first baking in step S2 is 80-100° C., and the baking time is 10-20 minutes.

[0016] In one embodiment of the present invention, the ventilation time in step S2 is 1 to 2 hours.

[0017] In one embodiment of the present invention, the secondary baking temperature in step S3 is 120-140° C., and the baking time is 5-10 minutes.

[0018] In one embodiment of the present invention, the vacuum degree during boiling in step S4 is 0.01-0.08 MPa, the boiling time of the vacuum syrup is 8-12 min, and the boiling temperature is 80-100°C.

[0019] In one embodiment of the present invention, the cutting and forming in step S5 refers to cutting into rod-shaped products with a length of 5-10 cm and a thickness of 1-3 cm.

[0020] The invention also discloses a crispy nut bar prepared according to the method.

[0021] The present invention also discloses the application of the above-mentioned two-stage gradient roasting combined with low-temperature vacuum cooking method in the preparation of nut products.

[0022] Beneficial effects:

[0023] 1. The present invention proposes a method of preparing crispy nut bars by using a two-stage gradient roasting method in conjunction with moisture control. The nut bars prepared by the present invention have the characteristics of low hardness and greater crispness, and the nut bars are not bitter and have a rich aroma.

[0024] 2. The present invention utilizes a double baking method combined with vacuum cooking to improve the crispness of the nut bar. The first baking is performed at a slightly lower temperature for a short time to release moisture in the nut bar without causing excessive charring of the surface. The second baking, under the action of the first baking, increases the baking temperature to further release moisture, and chars the surface under the action of high temperature, thereby improving the crispness and reducing the hardness. This overcomes the problem of the traditional single baking process that causes surface charring and residual moisture in the core, resulting in hardening of the nuts and affecting the taste.

[0025] 3. The introduction of secondary baking and low-temperature vacuum mixing processes can increase the crispness of the nut bars by 35%, reduce the hardness by 34%, and make them less likely to absorb moisture and become soft. DETAILED DESCRIPTION

[0026] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0027] Hardness and brittleness test: TA.new plus texture analyzer with a spherical probe (SMSP / 1SP) was used. The test distance was 75%, with a front speed of 1 mm / s, a test rate of 0.5 mm / s, a side-to-back speed of 2 mm / s, a dwell time of 2 seconds, and a trigger force of 5 g. This test was repeated five times. The test parameter was hardness (in grams).

[0028] Moisture content test results: Refer to the national food safety standard "GB 5009.3-2016" Determination of moisture in food.

[0029] Example 1

[0030] A method for preparing a crispy nut bar based on two-stage gradient roasting, the specific steps are as follows:

[0031] S1: Raw material preparation: prepare 8 parts of almonds, 11 parts of cashews, 5 parts of walnuts, 6 parts of pumpkin seeds, 8 parts of pistachios, 2 parts of chia seeds, and 8 parts of isomaltooligosaccharide.

[0032] S2: Primary baking: Place the raw materials prepared in step S1 into an oven at 100°C for 20 minutes with a moisture content of approximately 10%. Ventilate for 2 hours to achieve complete cooling.

[0033] S3: Secondary baking: The completely cooled raw materials in S2 are placed in an oven at a temperature of 120° C. for 10 minutes, with a moisture content of approximately 6%.

[0034] S4: Nut bar preparation: Use a vacuum syrup cooker to prepare syrup with a sugar (8 parts isomaltooligosaccharide) to water ratio of 1:1.5, and cook at 100°C for 8 minutes under a vacuum condition of 0.01 MPa. Then, add the nut raw materials (40 parts) in S3 to the vacuum cooker and mix under vacuum conditions.

[0035] S5: Pressing and molding: Put the raw materials in S4 into a mold, press and mold, cool for 2 hours, cut and mold into a thickness of 3 cm and a height of 8 cm to obtain a nut bar product.

[0036] Example 2

[0037] The only difference between Example 2 and Example 1 is that the amount of isomaltooligosaccharide added in S1 is modified to 12 parts.

[0038] Example 3

[0039] The only difference between Example 3 and Example 1 is that the amount of nut raw materials added in step S1 is different, namely, 12 parts of almonds, 8 parts of cashews, 10 parts of walnuts, 5 parts of pumpkin seeds, 12 parts of pistachios, 4 parts of chia seeds, and 12 parts of isomaltooligosaccharide.

[0040] Comparative Example 1

[0041] The difference between Comparative Example 1 and Example 1 is that step S2 is omitted, and the raw materials in S1 are directly placed in the oven in S3 and baked under the conditions of S3;

[0042] Comparative Example 2

[0043] The difference between Comparative Example 2 and Example 1 is that step S3 is omitted;

[0044] Comparative Example 3

[0045] The difference between Comparative Example 3 and Example 1 is that steps S2 and S3 are omitted, and the raw materials in S1 are directly vacuum boiled to prepare the nut bar product;

[0046] Comparative Example 4

[0047] The difference between Comparative Example 4 and Example 1 is that the isomaltooligosaccharide in step S4 is replaced with corn syrup;

[0048] Comparative Example 5

[0049] The difference between Comparative Example 5 and Example 1 is that the isomaltooligosaccharide in step S4 is replaced with maltose syrup;

[0050] Comparative Example 6

[0051] The difference between Comparative Example 6 and Example 1 is that the isomaltooligosaccharide in step S4 is replaced with maltitol;

[0052] Comparative Example 7

[0053] The difference between Comparative Example 7 and Example 1 is that the vacuum cooking temperature is changed to 70°C.

[0054] Comparative Example 8

[0055] The difference between Comparative Example 8 and Example 1 is that the vacuum cooking temperature is changed to 100° C. and the time is changed to 15 minutes.

[0056] Comparative Example 9

[0057] The difference between Comparative Example 9 and Example 1 is that the baking time is extended by 1 hour.

[0058] Comparative Example 10

[0059] The difference between Comparative Example 10 and Example 1 is that the secondary baking time is extended by 30 min.

[0060] Comparative Example 11

[0061] The difference between Comparative Example 11 and Example 1 is that the amount of isomaltooligosaccharide used is different, that is, 6.5 parts.

[0062] Experimental results

[0063] Table 1 Hardness and brittleness results of nut bars in Examples and Comparative Examples

[0064] Examples Hardness / g Brittleness / g Taste / flavor / quality Example 1 1469 2152 No bitterness, crispy, rich aroma Example 2 1534 1904 No bitterness, crispy, rich aroma Example 3 1501 2038 No bitterness, crispy, rich aroma Comparative Example 1 3025 1702 No bitterness, slightly hard, light fragrance Comparative Example 2 3251 1593 No bitterness, slightly hard, light fragrance Comparative Example 3 3645 2593 No bitterness, slightly hard, light fragrance Comparative Example 4 3264 2569 No bitterness, no stickiness, rich aroma Comparative Example 5 4231 3025 No bitterness, no stickiness, rich aroma Comparative Example 6 3894 2904 No bitterness, no stickiness, rich aroma Comparative Example 7 2102 2242 No bitterness, no stickiness, rich aroma Comparative Example 8 2930 3019 No bitterness, hardness, rich aroma Comparative Example 9 1802 2103 Slightly bitter, light aroma, poor quality Comparative Example 10 2014 2253 Slightly bitter, light aroma, poor quality Comparative Example 11 1702 1902 No bitterness, crispy, rich aroma

[0065] Table 2 Moisture content results of the 30-day storage experiment at 37°C

[0066] time 0 days 7 days 14 days 28 days 30 days Example 1 5.83％ 6.13％ 6.21％ 5.91％ 5.79％ Example 2 6.24％ 5.86％ 6.25％ 5.83％ 5.79％ Example 3 6.91％ 5.48％ 6.01％ 6.35％ 6.13％ Comparative Example 1 10.2％ 11.4％ 12.74％ 16.1％ 15.7％

[0067] Table 1 shows the hardness and brittleness data and flavor of the nut bars in Examples 1 to 3 and Comparative Examples 1 to 11. It can be seen from the experimental results of Examples 1 to 3 and Comparative Example 11 that the amount of oligomeric isomaltosaccharides added has a significant effect on the hardness and brittleness effect. Specifically, the amount of oligomeric isomaltosaccharides added can ensure that they are evenly dispersed in the nut bar within a certain range, reducing their hardness and increasing their brittleness. Too much addition will cause the sugar to accumulate at the bottom, thereby increasing the hardness and reducing the brittleness of the nut bar. If the amount of addition is too much, it will cause it to be unevenly distributed in the nut bar and have poor bonding properties, thereby affecting the hardness and brittleness effect. Compared with Comparative Examples 4 to 6, Example 1 changes the type of sugar (binder) in Comparative Examples 4 to 6. The results show that after replacing oligomeric isomaltosaccharides with binders such as corn syrup, the viscosity of the nut bar will be higher and the hardness will be larger, thereby affecting the taste of the nut bar.

[0068] In the present invention, the most critical process parameters affecting the crispness of the nut bar are the baking parameters and the cooking parameters. The present invention controls the moisture content of the nut bar by adjusting the baking and cooking parameters, thereby improving the crispness of the nut bar in combination with the preparation process. The influence of the parameters is specifically manifested in that, on the one hand, two bakings are very important for adjusting the crispness of the nut bar. Among them, the first baking is a short-term baking at a slightly lower temperature, which releases the moisture in the nut bar without causing excessive surface coking. The second baking increases the baking temperature under the action of the first baking, further releasing the moisture, and coking the surface under the action of high temperature, thereby improving the crispness and reducing the hardness. If only one baking is performed, whether it is baked at low temperature or high temperature, it will result in poor hardness and brittleness, especially the hardness will be significantly higher. In addition, the baking time mainly affects the taste and quality. Although long baking will lead to an increase in hardness, the change will not be particularly large. The main reason is that long baking will cause the taste to be bitter and the aroma to be weak. The temperature and time of vacuum cooking also have a significant impact on the hardness and brittleness of the product. Specifically, if the temperature is too low, the hardness and brittleness of the product will increase, causing it to stick to the teeth. If the cooking time is too long, the taste will be hard.

[0069] Table 2 shows the change in moisture content of nut bars stored at 37°C over time. It can be seen that the moisture content of the nut bars of the present invention did not change much after 30 days of storage at 37°C. However, in Comparative Example 1, the original nut bar had a high moisture content after only one baking. After 30 days of storage, the moisture content increased significantly, shortening the shelf life of the nut bar. Other comparative examples also had unreasonable moisture content ranges or experienced quality degradation during storage.

[0070] The embodiments provided above are not intended to limit the scope of the present invention, nor are the steps described to limit their execution order. Any obvious improvements to the present invention made by those skilled in the art in combination with existing common knowledge shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a crispy nut bar based on two-stage gradient baking, characterized in that: The specific steps are as follows: S1: Raw material preparation: prepare nuts or seeds raw materials; S2: Primary baking: Place the raw materials prepared in step S1 into an oven, bake once, and then ventilate until completely cooled. The baking temperature is 80-100° C. and the baking time is 10-30 minutes. S3: Secondary baking: Place the completely cooled raw materials in S2 into an oven for secondary baking at a temperature of 120-150°C for 10-20 minutes; S4: Nut bar preparation: Use a vacuum syrup cooker to prepare syrup, add oligomaltodextrose and water to the vacuum syrup cooker, and cook at 80-100°C for 8-12 minutes under vacuum conditions of 0.01-0.08 MPa; then add the nut ingredients in S3 to the vacuum cooker, where the nut ingredients and oligomaltodextrose are added in a ratio of 80-100 parts: 15-25 parts, and mix under vacuum conditions; S5: Pressing and molding: Put the raw materials in S4 into a mold, press and mold, cool for 1-2 hours, cut and mold to obtain a nut bar product.

2. The preparation method according to claim 1, characterized in that The nut or seed raw material in step S1 includes at least one of almonds, cashews, walnuts, pumpkin seeds, pistachios, chia seeds, hazelnuts, pine nuts, and almonds.

3. The preparation method according to claim 1, characterized in that Calculated by weight, the nut or seed raw materials in step S1 include at least one or more of 6-8 parts of almonds, 11-20 parts of cashews, 5-8 parts of walnuts, 6-12 parts of pumpkin seeds, 5-8 parts of pistachios, 2-5 parts of chia seeds, 4-6 parts of hazelnuts, 3-5 parts of pine nuts, and 4-7 parts of almonds.

4. The preparation method according to claim 1, characterized in that The moisture content of the raw materials after the first baking in step S2 is 8-12%, and the ventilation time is 1-2 hours.

5. The preparation method according to claim 1, characterized in that The moisture content of the raw material after the secondary baking in step S3 is 5-7%.

6. The preparation method according to claim 1, characterized in that In step S4, the mass ratio of maltooligosaccharide to water is 1:1-2.

7. The preparation method according to claim 1, characterized in that The vacuum degree during boiling in step S4 is 0.01-0.05 MPa, the boiling time of the vacuum syrup is 8-10 minutes, and the boiling temperature is 100°C.

8. The preparation method according to claim 1, characterized in that The cutting and forming in step S5 refers to cutting into rod-shaped products with a length of 5-10 cm and a thickness of 1-3 cm.

9. The crispy nut bar prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the method of two-stage gradient roasting combined with low-temperature vacuum cooking in claim 1 in preparing nut products.