Walnut shell smoking liquid as well as preparation method and application thereof

Abstract

The invention relates to the technical field of food processing, and particularly discloses a walnut shell smoking liquid as well as a preparation method and application thereof, and the preparation method comprises the following steps: drying walnut shells until the water content is 7-10% by mass, crushing the walnut shells, sieving the crushed walnut shells with a 10-30-mesh sieve, adding cane sugar, and then sequentially carrying out destructive distillation, condensation and filtration to obtain the walnut shell smoking liquid; the dry distillation temperature is 400-450 DEG C, the dry distillation time is 20-40 minutes, and the addition amount of the cane sugar is 12.0%-14.0%. According to the walnut shell smoking liquid prepared by the method provided by the invention, the contents of phenolic substances, carbonyl compounds and soluble solids are increased, and the high-quality smoking liquid is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a walnut shell smoking liquid and a preparation method and application thereof. Background Art

[0002] The large amount of smoke produced by burning wood in the traditional smoking process pollutes the environment, and the polycyclic aromatic hydrocarbons such as 3,4-benzo(a)pyrene that consumers are exposed to during the smoking process pose a potential threat to their health.

[0003] Liquid smoke, also known as smoke flavoring, is made from natural plants and refined through distillation and purification processes. However, the quality of liquid smoke is greatly affected by material selection, distillation process and purification process. The volatile flavor substances in liquid smoke are mainly divided into 9 categories, namely phenols, aldehydes, ketones, acids, esters, alcohols, furans, benzene and other components. Among them, carbonyl compounds have smoky flavor characteristics, and their content is of great significance to the overall flavor quality. The quality of liquid smoke is closely related to the process and parameters in its preparation process. Liquid smoke prepared by traditional preparation processes often ignores the contribution of carbonyl compounds to the quality of liquid smoke. Therefore, it is urgent to provide a method for preparing liquid smoke that takes into account the flavor characteristics of carbonyl compounds. Summary of the invention

[0004] In order to develop a method for preparing high-quality smoke liquid, the present invention provides a walnut shell smoke liquid and a preparation method and application thereof. The color index of the smoke liquid prepared by the present invention using walnut shell as a raw material is better than that of other raw materials. When the water content of the walnut shell is 7% to 10% by mass, the particle size of the spice powder is 10 mesh to 30 mesh, the amount of sucrose added is 12.0% to 14.0%, the retorting temperature is 400°C to 450°C, and the retorting time is 20min to 40min, the phenol content and carbonyl compound content in the walnut shell smoke liquid prepared under specific process parameter settings are significantly higher than those outside the range.

[0005] The present invention provides a method for preparing walnut shell smoke liquid, comprising the following steps:

[0006] The walnut shells are dried at 90-100° C. to a water content of 7-10% by mass, crushed and sieved through a 10-mesh to 30-mesh sieve to obtain spice powder, and then sucrose accounting for 12.0%-14.0% of the mass fraction of the spice powder is added; and then the walnut shell smoke liquid is obtained by sequentially performing dry distillation, condensation and filtration; the dry distillation temperature is 400-450° C., and the dry distillation time is 20-40 minutes.

[0007] The invention uses walnut shells as raw materials, dries the walnut shells to a moisture content of 7% to 10%, crushes them to 10 meshes to 30 meshes to obtain spice powder, adds sucrose accounting for 12.0% to 14.0% of the mass fraction of the spice powder, and then obtains walnut shell smoke liquid through dry distillation, condensation and filtration, wherein the dry distillation temperature is 400° C. to 450° C., and the dry distillation time is 20 min to 40 min. The smoke liquid prepared by setting the above technical parameters and combining the process means significantly increases the content of phenolic substances, carbonyl compounds and soluble solids, and obtains high-quality smoke liquid. Compared with existing commercially available products, the walnut shell smoking liquid prepared by the invention has newly added flavor characteristic substances: 3-methyl-phenol, 3-ethyl-phenol, 4-ethyl-2-methyl-phenol, 2-ethyl-4-methyl-phenol, 2-methyl-5-(1-methylethyl)-phenol, 2-hydroxy-3-methylbenzaldehyde, 3-methyl-3-cyclohexene-1-one, 1-(2-hydroxyphenyl)-ethanone, 2-methyl-benzofuran, ethyl-2-benzofuran, ethyl-2-benzofuran, styrene, indene, naphthalene and 2-methyl-naphthalene.

[0008] The invention also provides a walnut shell smoking liquid prepared by the preparation method.

[0009] The present invention also provides an application of the walnut shell smoke liquid in preparing smoked horse meat. The walnut shell smoke liquid prepared by the method of the present invention has good quality. By adding 3% to 5% of the walnut shell smoke liquid by volume, the smoked horse meat prepared has high quality and a sensory score of 85.72±0.19.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] The invention uses walnut shells as raw materials, dries the walnut shells to a moisture content of 7% to 10%, crushes them to 10 meshes to 30 meshes to obtain spice powder, adds sucrose accounting for 12.0% to 14.0% of the mass fraction of the spice powder, and then obtains walnut shell smoke liquid through dry distillation, condensation and filtration, wherein the dry distillation temperature is 400° C. to 450° C., and the dry distillation time is 20 min to 40 min. By setting the above technical parameters and combining process means, the prepared smoke liquid increases the content of phenolic substances, carbonyl compounds and soluble solids, and obtains high-quality smoke liquid. Compared with existing commercial products, the walnut shell smoke liquid prepared by the invention has new flavor characteristic substances: 3-methyl-phenol, 3-ethyl-phenol, 4-ethyl-2-methyl-phenol, 2-ethyl-4-methyl-phenol, 2-methyl-5-(1-methylethyl)-phenol, 2-hydroxy-3-methylbenzaldehyde, 3-methyl-3-cyclohexene-1-one, 1-(2-hydroxyphenyl)-ethanone, 2-methyl-benzofuran, ethyl-2-benzofuran, ethyl-2-benzofuran, styrene, indene, naphthalene and 2-methyl-naphthalene. The invention also selects a macroporous resin adsorption method to reduce and remove 3,4-benzopyrene in natural smoke liquid, so as to obtain a new smoke liquid with ideal effects in both flavor and function. The smoke liquid prepared by the present invention is used for smoking horse meat. It is found that when the addition amount of the smoke liquid is 3% to 5% and the cooking temperature is 95° C. to 100° C., the finished product rate and quality of the liquid-smoked horse meat are significantly improved, the finished product rate is above 70%, and the sensory score reaches 85.72±0.19. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 The figure shows the influence of different raw material selection and preparation process on the quality of the prepared liquid smoke; in the figure, A shows the influence of different raw material selection on the phenolic content of the prepared liquid smoke; B shows the influence of different raw material selection on the carbonyl compound content of the prepared liquid smoke; C shows the influence of distillation time on the phenolic content and carbonyl compound content of the prepared walnut shell liquid smoke; D shows the influence of the particle size of the spice powder (spice mesh number) on the phenolic content and carbonyl compound content of the prepared walnut shell liquid smoke. Figure 2 To study the effect of sucrose addition on the phenolic and carbonyl compound contents of walnut shell smoked liquid. Figure 3Response surface diagram and contour diagram of the two-variable interaction in the preparation of walnut shell smoke liquid; in the figure, (a), (c), (e) respectively represent the response surface diagrams of distillation time and spice particle size, distillation time and sucrose addition amount, spice particle size and sucrose addition amount; (b), (d), (f) respectively represent the contour diagrams of distillation time and spice particle size, distillation time and sucrose addition amount, spice particle size and sucrose addition amount. Figure 4 To study the effect of walnut shell moisture content on the phenolic and carbonyl compound contents of the prepared walnut shell smoke liquid. Figure 5 The types and contents of volatile flavor substances in the walnut shell smoke liquid prepared in Example 6 and commercially available smoke liquid. Figure 6 The effect of different process parameters on the quality of smoked horse meat; in the figure, A, B, C and D respectively represent the effects of the amount of smoke liquid added, ultrasonic-assisted immersion time, cooking temperature and cooking time on the quality of smoked horse meat. Figure 7 These are the response surface diagram and contour diagram of the two variable interaction in the preparation process of smoked horse meat; in the figure, a and b represent the response surface diagrams of the amount of smoke liquid added and ultrasonic-assisted immersion time, the amount of smoke liquid added and cooking temperature, respectively; c and d represent the contour diagrams of the amount of smoke liquid added and ultrasonic-assisted immersion time, the amount of smoke liquid added and cooking temperature, respectively. Figure 8 These are the response surface diagram and contour diagram of the two variable interaction in the preparation process of smoked horse meat; in the figure, a and b represent the response surface diagrams of the amount of smoke liquid added and cooking time, ultrasonic-assisted immersion time and cooking temperature, respectively; c and d represent the contour diagrams of the amount of smoke liquid added and cooking time, ultrasonic-assisted immersion time and cooking temperature, respectively. Fig. 9 These are the response surface diagram and contour diagram of the interaction between two variables in the preparation process of smoked horse meat; in the figure, a and b represent the response surface diagrams of ultrasonic-assisted immersion time and cooking time, cooking temperature and cooking time, respectively; c and d represent the contour diagrams of ultrasonic-assisted immersion time and cooking time, cooking temperature and cooking time, respectively. DETAILED DESCRIPTION

[0014] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified, and the materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0015] Embodiment 1: A walnut shell smoking liquid and a preparation method thereof.

[0016] 1. Experimental Materials and Methods

[0017] 1. Experimental materials: Walnut shells were collected from Aksu, Xinjiang.

[0018] 2. Preparation steps of walnut shell smoke liquid

[0019] The walnut shells were laid out neatly in a blast drying oven and dried at 100°C to a moisture content of 9%, then crushed in a grinder and passed through a 20-mesh sieve to obtain spice powder. 300g of spice powder and 14.0% sucrose by mass of the spice powder were placed in a 1L round-bottom flask, which was then placed in an electric heating jacket and connected to a condensing device. The temperature was raised to 450°C and dry distilled for 30.0min. Then, the smoked liquid was collected by condensation. The smoked liquid was allowed to stand at -5°C for 24h to achieve complete separation of smoke components and tar (smoked liquid was in the upper layer and tar was in the lower layer). After taking out the sample, it was restored to room temperature and slowly filtered with a double-layer 6μm qualitative filter paper. After filtration, the upper layer of smoked liquid was collected as the filtrate, and the filtrate was allowed to stand again at -5°C for 12h, and then filtered again, and the upper layer of smoked liquid was collected to achieve refining, and refined smoked liquid was obtained. Then, 10 mL of refined smoke liquid was added to 1 g of pretreated XAD-4 macroporous adsorption resin, and the mixture was shaken at 120 r / min for 24 h at 32 ° C. Subsequently, the macroporous adsorption resin was slowly filtered using a double-layer 6 μm qualitative filter paper to obtain walnut shell smoke liquid. The pretreatment process of XAD-4 macroporous adsorption resin is as follows: the macroporous adsorption resin is placed in a conical flask and soaked in 95% ethanol for 24 h to achieve complete swelling of the macroporous adsorption resin. Then, the macroporous adsorption resin is washed with 95% ethanol. After the ethanol used to wash the macroporous adsorption resin is mixed with distilled water at a ratio of 1:5, there is no white precipitate, indicating that the macroporous adsorption resin has been washed. Then, the macroporous adsorption resin is washed with distilled water until there is no ethanol smell. Soak it with 3 times the volume of 5% HCl solution and 2% NaOH solution for 2 h, and then wash it with distilled water until it is neutral.

[0020] Embodiment 2: A walnut shell smoking liquid and a preparation method thereof.

[0021] The method is basically the same as Example 1, except that the dry distillation time is 30 min, the walnut shells are crushed to pass through 10 meshes, and the amount of sucrose added is 12.0%.

[0022] Embodiment 3: A walnut shell smoking liquid and a preparation method thereof.

[0023] The method is basically the same as Example 1, except that the dry distillation time is 20 min, the walnut shells are crushed to pass through 25 meshes, and the amount of sucrose added is 12.0%.

[0024] Embodiment 4: A walnut shell smoking liquid and a preparation method thereof.

[0025] The method is basically the same as Example 1, except that the dry distillation time is 40 min, the walnut shells are crushed to pass through 25 meshes, and the amount of sucrose added is 13.0%.

[0026] Embodiment 5: A walnut shell smoking liquid and a preparation method thereof.

[0027] The method is basically the same as Example 1, except that the dry distillation time is 35 min, the walnut shells are crushed through 30 meshes, and the amount of sucrose added is 14.0%.

[0028] Embodiment 6: A walnut shell smoking liquid and a preparation method thereof.

[0029] The method is basically the same as Example 1, except that the dry distillation time is 31 min, the walnut shells are crushed through 20 meshes, and the amount of sucrose added is 14.0%.

[0030] Comparative Example 1: Fragrant pear wood smoke liquid and preparation method thereof.

[0031] The preparation steps are basically the same as those in Example 1, except that the walnut shells are replaced with fragrant pear wood, which is collected from Shayidong Horticultural Farm in Korla, Bayinguoleng Mongol Autonomous Prefecture, Xinjiang.

[0032] Comparative Example 2: Crabapple wood smoke liquid and preparation method thereof.

[0033] The preparation steps are basically the same as those in Example 1, except that the walnut shells are replaced with crabapple wood, which is collected from Manas, Changji Autonomous Prefecture, Xinjiang.

[0034] 1. The smoke liquid prepared in Example 1 and Comparative Examples 1-2 was used as the test sample, and the color, soluble solid content, phenol content, carbonyl compound content and harmful substance 3,4-benzo(a)pyrene content of the samples were tested respectively. The test method and test results are as follows:

[0035] 1. Experimental methods

[0036] (1) Color determination: Use Color i7 colorimeter to determine L* value, a* value and b* value. (2) Soluble solids determination: Refer to ISO 2173-2003. "Determination of soluble solids content of fruit and vegetable products". (3) Phenol content determination: Dilute the smoke liquid to 100 times, prepare 1mg / mL gallic acid mother solution, and then prepare gallic acid standard solutions with concentrations of 20, 40, 60, 80 and 100μg / mL respectively. Pipette 200μL of sample solution or gallic acid standard solution, add 1mL15% Folin phenol reagent, mix well, and react for 10 minutes. Then, add 800μL 5% calcium carbonate solution and mix well again. Place the mixture at room temperature and put it in a shaker under light-proof conditions, and shake at a speed of 120r / min for 2h. Next, 250 μL of the mixture was added to each well of the 96-well plate, and the absorbance was measured at a wavelength of 765 nm using an ELISA reader. The phenol content was calculated as follows:

[0037] Phenol content (mg / mL) = d x x 0.001, where d: dilution factor; X: sample conversion result based on gallic acid standard curve, μg / mL; 0.001 is the conversion factor.

[0038] (4) Determination of carbonyl compounds: Refer to the hydroxylamine hydrochloride method in GB 1886.127-2016 "Food Additives Hawthorn Kernel Smoked Flavors No. Ⅰ and No. Ⅱ" to measure the content of carbonyl compounds. (5) Determination of 3,4-benzo(a)pyrene: Refer to GB 5009.27-2016 "Determination of Benzo(a)pyrene in Foods" for detection operations. The sample liquid was prepared, extracted and purified according to the national standard for the preparation, extraction and purification of oils and their products. After filtering through a 0.45μm microporous filter membrane, the benzo(a)pyrene content in the smoked liquid was detected by high performance liquid chromatography. C 18 The liquid chromatography column (4.6 mm × 250 mm, 5 μm) was equipped with acetonitrile and water as the mobile phase, with a ratio of 88% and 12%, and the mobile phase flow rate was set at 1.2 mL / min. The excitation wavelength of the fluorescence detector was 384 nm and the emission wavelength was 406 nm; the column temperature was controlled at 30 °C; the injection volume was 10 μL. (6) GC-IMS analysis conditions

[0039] Sample treatment: Take out 10 μL of the smoke liquid sample to be tested, dilute it to 10 mL, then take 1 mL of the dilution and put it into a 20 mL headspace bottle, then incubate it at 60°C for 10 minutes, and finally perform sampling analysis.

[0040] Gas phase ion mobility chromatography unit conditions: column type FS-SE-54-CB-0.5 15m ID: 0.53mm; column temperature 60°C; carrier gas / drift gas N2; IMS temperature 45°C. Automatic headspace injection unit: injection volume 1mL; incubation time 10min; incubation temperature 60°C; injection needle temperature 65°C; incubation speed 500rpm.

[0041] 2. Experimental results

[0042] Table 1 Test results of physical indexes of different smoke liquids

[0043] Grouping category Brightness value L* Redness value a* Yellowness value b* Soluble solids / % Comparative Example 1 Pearwood <![CDATA[11.08±0.20 c ]]> <![CDATA[7.61±0.08 c ]]> <![CDATA[7.25±0.10 d ]]> <![CDATA[12.17±0.28 c ]]> Comparative Example 2 Begonia <![CDATA[15.27±0.59 b ]]> <![CDATA[4.66±0.39 d ]]> <![CDATA[15.06±0.79 c ]]> <![CDATA[10.33±0.28 d ]]> Example 1 Walnut Shells <![CDATA[19.97±0.63 a ]]> <![CDATA[13.87±0.67 a ]]> <![CDATA[22.45±1.34 a ]]> <![CDATA[16.83±0.28 b ]]>

[0044] Note: Data are expressed as mean ± standard deviation. For longitudinal comparison, the same lowercase letters indicate no significant difference (P>0.05); different lowercase letters indicate significant difference (P<0.05).

[0045] The results are shown in Table 1. The walnut shell smoke liquid prepared with walnut shell as raw material in Example 1 of the present invention has the highest a* value, reaching 13.87, the highest b* value, which is 22.45, and the highest soluble solid content, indicating that the various indicators of the smoke liquid prepared with walnut shell as raw material are significantly higher than those of other raw materials.

[0046] The results are as follows Figure 1 As shown in A, the phenol content in the walnut shell smoke liquid prepared in Example 1 is significantly higher than that in the smoke liquid prepared in Comparative Example 1 and Comparative Example 2. This indicates that the use of walnut shell as a raw material to prepare smoke liquid significantly increases the content of phenolic substances and improves the quality of the smoke liquid.

[0047] The results are as follows Figure 1 As shown in Figure B, the carbonyl compound content in the smoke liquid prepared with walnut shell as raw material in Example 1 is the highest, reaching 18.57 g / 100 mL, which is significantly higher than the smoke liquid prepared with fragrant pear wood and crabapple wood as raw materials in Comparative Examples 1 and 2. The carbonyl content of the smoke liquid prepared in Example 1 is significantly higher than that of the four commercially available smoke liquids mentioned in the journal [Zhao Bing, Li Su, Wang Shouwei, et al. Quality characteristics of apple wood smoke liquid [J]. Food Science], ranging from 3.16 g / 100 mL to 8.22 g / 100 mL.

[0048] The benzo(a)pyrene in the product was detected by high performance liquid chromatography according to national standards. The results showed that no benzo(a)pyrene was detected in the smoking liquids prepared in Example 1 and Comparative Examples 1-2.

[0049] 2. Comparative Examples 3 to 6 were set up to study the effect of different distillation times on the quality of walnut shell smoke liquid.

[0050] Comparative Example 3: A walnut shell smoking liquid and a preparation method thereof.

[0051] The preparation steps are basically the same as those in Example 2, except that the dry distillation time is 45 min.

[0052] Comparative Example 4: A walnut shell smoking liquid and a preparation method thereof.

[0053] The preparation steps are basically the same as those in Example 2, except that the dry distillation time is 60 min.

[0054] Comparative Example 5: A walnut shell smoking liquid and a preparation method thereof.

[0055] The preparation steps are basically the same as those in Example 2, except that the dry distillation time is 75 min.

[0056] Comparative Example 6: A walnut shell smoking liquid and a preparation method thereof.

[0057] The preparation steps are basically the same as those in Example 2, except that the dry distillation time is 90 min.

[0058] The phenol content and carbonyl compound content of the walnut shell smoke liquids prepared in Comparative Examples 3 to 6 were tested according to the above method.

[0059] The results are as follows Figure 1 As shown in Figure C, with the continuous distillation time, the concentrations of carbonyl compounds and phenolic compounds in the smoke liquid produced by walnut shells showed a rapid increase to a peak and then a slow decrease. When the distillation time was between 20min and 40min, the phenol content and carbonyl compound content of the prepared walnut shell smoke liquid were significantly higher than those at other times. The reason for this phenomenon may be that with the increase of distillation time, the hemicellulose and cellulose inside the walnut shell gradually entered a progressive decomposition stage. This process leads to an increase in the number of carbonyl compounds. However, once the distillation time reaches a certain critical point, the hemicellulose and cellulose in the walnut shell will tend to be completely decomposed. When the distillation time is 30.0min, the carbonyl compound and phenol content both reach the maximum value, and as the distillation time continues to increase, the changes in the carbonyl compound and phenol content tend to be gentle.

[0060] 3. Comparative Examples 7 to 10 were set up to study the effects of different particle sizes of spice powder on the quality of walnut shell smoke liquid.

[0061] Comparative Example 7: A walnut shell smoking liquid and a preparation method thereof.

[0062] The preparation steps are basically the same as those in Example 1, except that the walnut shells are crushed and passed through a 10-mesh filter to obtain the spice powder.

[0063] Comparative Example 8: A walnut shell smoking liquid and a preparation method thereof.

[0064] The preparation steps are basically the same as those in Example 1, except that the walnut shells are crushed and passed through a 30-mesh filter to obtain the spice powder.

[0065] Comparative Example 9: A walnut shell smoking liquid and a preparation method thereof.

[0066] The preparation steps are basically the same as those in Example 1, except that the walnut shells are crushed and passed through a 40-mesh filter to obtain the spice powder.

[0067] Comparative Example 10: A walnut shell smoking liquid and a preparation method thereof.

[0068] The preparation steps are basically the same as those in Example 1, except that the walnut shells are crushed and passed through a 60-mesh filter to obtain the spice powder.

[0069] The phenol content and carbonyl compound content of the walnut shell smoked liquids prepared in Comparative Examples 7 to 10 were tested according to the above-mentioned testing method.

[0070] The results are as follows Figure 1 As shown in D, the phenol content and carbonyl compound content of the walnut shell smoke liquid prepared when the spice powder particle size is 10-30 mesh are significantly higher than those of other particle sizes, and the walnut shell smoke liquid prepared with a spice powder particle size of 20 mesh has the highest phenol content and carbonyl compound content. As can be seen from the figure, as the walnut shell particle size decreases, the phenolic substances and carbonyl compounds contained in the walnut shell smoke liquid show a downward trend. When the particle size reaches 20.0 mesh, the content of these two compounds reaches a peak. This may be because the smaller particle size makes the temperature difference between the inside and outside of the walnut shell smaller when heated, and the heat transfer is rapid, resulting in more complete pyrolysis. However, when the particle size is less than 20.0 mesh, due to the small particle size, the heat transfer is too fast, which may promote the carbonization process, resulting in a reduction in the original product in the walnut shell smoke liquid.

[0071] 4. Study the effect of different particle sizes of spice powder and moisture content of walnut shell on the quality of walnut shell smoke liquid

[0072] 1. Comparative Examples 11 to 14 were set up to study the effects of different particle sizes of spice powder on the quality of walnut shell smoke liquid.

[0073] Comparative Example 11: A walnut shell smoking liquid and a preparation method thereof.

[0074] The preparation steps are basically the same as those in Example 1, except that the amount of sucrose added is 5.0%.

[0075] Comparative Example 12: A walnut shell smoking liquid and a preparation method thereof.

[0076] The preparation steps are basically the same as those in Example 1, except that the amount of sucrose added is 8.0%.

[0077] Comparative Example 13: A walnut shell smoking liquid and a preparation method thereof.

[0078] The preparation steps are basically the same as those in Example 1, except that the amount of sucrose added is 11.0%.

[0079] Comparative Example 14: A walnut shell smoking liquid and a preparation method thereof.

[0080] The preparation steps are basically the same as those in Example 1, except that the amount of sucrose added is 17.0%.

[0081] The phenol content and carbonyl compound content of the walnut shell smoke liquids prepared in Comparative Examples 11 to 14 were tested according to the above-mentioned testing method.

[0082] The results are as follows Figure 2 As shown in the figure, with the increase of sucrose addition, the carbonyl compounds in walnut shell smoke liquid increased rapidly, while the phenolic substances increased slowly. The contents of both reached a peak when the sucrose addition reached 14.0%. When the sucrose addition continued to increase, the concentration of total phenols showed a downward trend, while the content of carbonyl compounds tended to be stable. This may be because the moisture contained in sucrose hindered the decomposition of lignin during the heating process. Considering that excessive sucrose content is easy to carbonize, it affects the heating and decomposition of wood, thus affecting the quality of smoke liquid.

[0083] 2. The other steps are the same as those in Example 1, and the walnut shells are dried to a moisture content of 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10% by mass. The effect of the moisture content of the walnut shells on the quality of the walnut shell smoke liquid is studied.

[0084] The results are as follows Figure 4 As shown, when the moisture content of the walnut shell is 5%-10%, the content of carbonyl compounds in the prepared walnut shell smoke liquid continues to increase with the increase of the moisture content. When the moisture content reaches 9%, the content of carbonyl compounds reaches the highest point, but there is no significant change when the moisture content is 7-11%. It shows that controlling the moisture content of the walnut shell at 7%-9% can significantly increase the content of carbonyl compounds in the prepared walnut shell smoke liquid, thereby improving the quality of the walnut shell smoke liquid.

[0085] 5. Response surface optimization experiment

[0086] 1. The content of carbonyl compounds was selected as the key response index, and the three factors of distillation time, flavor particle size and sucrose addition were determined as independent variables. Subsequently, Design-Expert 13 software was used to conduct a three-factor three-level experimental design. The specific experimental factors and level settings are shown in Table 2. Each set of experimental conditions will be tested three times to ensure the reliability of the data.

[0087] Table 2 Factors and levels of response surface experiment

[0088]

[0089] 2. According to the experimental results of the above-mentioned embodiments of the present invention and the comparative examples, the Design-Expert 13 software was used, and according to the design concept of Box-Behnken, the carbonyl compound content was selected as the response value, and a response surface analysis including three factors and three levels was performed, and 17 experimental points were set in total. This process is intended to explore the influence of different factors on the carbonyl compound content and optimize the experimental conditions. The design combination and the results are shown in Table 3.

[0090] Table 3 Response surface design scheme and results

[0091] Test No. Retort time / min Spice particle size / mesh Sucrose addition amount / % Carbonyl compounds g / 100mL 1 30 20 14 31.171 2 20 10 14 24.829 3 30 20 14 31.629 4 40 30 14 26.63 5 30 20 14 31.066 6 30 30 17 27.458 7 40 20 11 25.978 8 30 10 17 26.747 9 40 10 14 26.135 10 30 20 14 31.543 11 20 20 17 25.706 12 30 30 11 28.545 13 20 30 14 25.393 14 30 20 14 31.933 15 30 10 11 27.401 16 40 20 17 26.834 17 20 20 11 24.26

[0092] 3. Model establishment and significance analysis

[0093] The Design-Expert 13 software was used to perform variance analysis on the test results of the preparation process of walnut shell smoke liquid, and the quadratic multinomial regression equation of the carbonyl compound content Y in walnut shell smoke liquid and A, B, C was obtained:

[0094] Y = 31.47 + 0.6736 × A + 0.3643 × B + 0.0701 × C - 0.0173 × A × B - 0.1475 × A × C - 0.1083 × B × C - 3.78 × A2 - 1.94 × B2 - 1.99 × C2. The results of the variance analysis of the regression model are shown in Table 4.

[0095] Table 4 Analysis of variance of regression model of carbonyl compound content

[0096]

[0097]

[0098] As shown in Table 4, all models are significant. According to the significance analysis of the influence of P value and F value on each factor, the result shows that each factor has a significant effect on the content of carbonyl compounds in walnut shell smoke liquid. The p of this model is less than 0.0001, and the lack of fit term of the equation is p = 0.0627, indicating that the equation has a good fit. In addition, the coefficient of variation (CV) of the model is 2.20%, indicating that the experiment is precise and reliable and can be used for statistical analysis. Among them, B is significant, indicating that the distillation time has a greater influence on the content of carbonyl compounds in walnut shell smoke liquid. From the F value, it can be seen that the order of influence of the three factors on the content of carbonyl compounds in walnut shell smoke liquid is: A>B>C, that is, distillation time>spice particle size>sucrose addition amount.

[0099] 4. Response surface three-dimensional model analysis

[0100] OriginPro 2021 software was used to draw trend line graphs and bar graphs; SPSS 26 software was used for preliminary data statistical analysis. The response surface optimization experiment was carried out using the Box-Behnken Design model of Design-Expert 13. The experimental data results were presented as mean and standard deviation.

[0101] The interactive effects among three groups of variables, namely, distillation time, spice particle size, and sucrose addition, were explored, and the interaction patterns of these effects were deeply analyzed using the response surface methodology. Figure 3 The contour map and response surface map based on the regression model are shown, where the shape of the contour line provides intuitive information about the significance of factor interaction: the ellipse indicates that there is a very significant interaction effect, while the circle indicates that the interaction is not obvious. In addition, the slope changes of each factor on the response surface reflect the intensity of their influence on the content of carbonyl compounds in walnut shell smoke liquid. The steeper the slope, the more significant the influence of the factor.

[0102] like Figure 3 As shown in the figure, the AB surface is the steepest in the interaction of the two variables, indicating that the interaction between distillation time and spice particle size has the most significant effect on the content of carbonyl compounds in walnut shell smoke liquid, which is consistent with the results of variance analysis in the regression model.

[0103] 5. Optimal Conditions Prediction and Verification

[0104] Through regression simulation, the optimal process conditions for the preparation of walnut shell smoke liquid were obtained as follows: the distillation time was 30.8901min, the spice particle size was 20.972 mesh, and the sucrose addition amount was 14.0345%. The carbonyl compound content in the walnut shell smoke liquid was 31.5152g / 100mL. Combined with the actual operation, the process conditions for the preparation of walnut shell smoke liquid were adjusted as follows: the distillation time was 31.0min, the spice particle size was 20.0 mesh, and the sucrose addition amount was 14.0%. According to the conditions, three parallel tests were carried out to prepare walnut shell smoke liquid. The actual measured carbonyl compound content was 31.019±0.19g / 100mL, which was close to the theoretical value. Therefore, the established quadratic model was consistent with the actual situation.

[0105] 6. Analyze and compare the types and contents of volatile flavor substances in the walnut shell smoke liquid prepared in Example 6 of the present invention and the commercial smoke liquid on Taobao platform (hawthorn kernel smoke flavor produced by Tai'an Deshun Food Additive Co., Ltd.). At the same time, the safety index of the walnut shell smoke liquid prepared in Example 6 was tested.

[0106] 1. Determination of volatile components

[0107] Extraction method: Accurately weigh 10g of homogeneous liquid sample into a 20ml headspace bottle, add a rotor, and place in a 40℃ water bath for 15 minutes. Insert the activated extraction head into the headspace bottle and push out the adsorption head, about 2mm away from the liquid surface of the adsorbed sample. After adsorption for 50 minutes, perform GC-MS sampling analysis.

[0108] Gas phase conditions: chromatographic column: Agilent HP-5MS, carrier gas: helium, column flow: 1 ml / min, injection port 270°C, split ratio: 1:1, program temperature rise: initial temperature 40°C, hold for 3 min, increase to 130°C at 3.2°C / min, increase to 280°C at 12°C / min, hold for 6 min. Mass spectrometry conditions: auxiliary heat 280°C, ion source 230°C, quadrupole 150°C, scan range 30-550.

[0109] Qualitative analysis: Qualitative analysis was performed by searching the NIST 20 database and calculating the compound retention index (RI) using C7 to C40 normal alkane standards to determine the chemical composition of the volatile compounds.

[0110] Quantitative calculation:

[0111]

[0112] Wherein: RT(x) is the retention time / min of the unknown compound; RT(n) is the retention time / min of the normal alkanes eluting before the unknown compound x; RT(n+1) is the retention time / min of the normal alkanes eluting after the compound.

[0113] The results of volatile component detection are shown in Table 5.

[0114] Table 5 Composition and relative content of volatile compounds in two smoking liquids

[0115]

[0116]

[0117] The results are shown in Table 5. The volatile flavor substances in walnut shell smoke liquid and commercial smoke liquid were detected by GC-MS technology. The volatile flavor substances in smoke liquid are mainly divided into 9 categories, namely phenols, aldehydes, ketones, acids, esters, alcohols, furans, benzene and other components. 62 volatile flavor substances were detected in commercial smoke liquid, including 22 phenols with a relative content of 20.76%; 5 aldehydes with a relative content of 21.49%; 16 ketones with a relative content of 7.88%; 2 acids with a relative content of 37.51%. 66 volatile flavor substances were detected in walnut shell smoke liquid, including 25 phenols with a relative content of 24.03%; 3 aldehydes with a relative content of 19.70%; 9 ketones with a relative content of 2.84%; 1 acid with a relative content of 34.51%. It can be seen that there are certain differences in the types and relative contents of the two smoke liquids.

[0118] By comparing the two liquid smokes, walnut shell smoke liquid contains 25 phenolic compounds, with a relative content of 24.03%, while commercial smoke liquid contains 22 phenolic compounds, with a relative content of 20.76%. The types and relative contents of walnut shell smoke liquid are higher than those of commercial smoke liquid.

[0119] from Figure 5 It can be seen that the relative contents of volatile flavor components in the smoke liquid prepared by the present invention and the commercially available smoke liquid are different. Compared with the commercially available smoke liquid, the types and relative contents of phenolic compounds in the walnut shell smoke liquid are the highest in terms of volatile flavor substances, while the relative contents of carbonyl compounds of characteristic flavors are not much different, and the contents of furfural and other components are higher than those of the commercially available smoke liquid.

[0120] 2. Safety index detection

[0121] 3,4-Benzo(a)pyrene The content of heavy metal lead and total arsenic in the smoking liquid was measured according to the above test steps and GB / T 15337-2008 and GB / T21191-2007. The test results are shown in Table 6.

[0122] Table 6 Determination results of safety indexes of walnut shell smoke liquid

[0123] Test items Detection Methods unit Test results 3,4-Benzopyrene GB / T 5009.27-2016 μg / kg Not detected lead GB / T 15337-2008 mg / kg ＜0.1 Total Arsenic GB / T 21191-2007 mg / kg ＜0.1

[0124] As shown in Table 6, all safety indicators of the walnut shell smoke liquid prepared by the present invention meet the national standards.

[0125] Application Example 1: Application of the walnut shell smoke liquid prepared by the present invention in the preparation of smoked horse meat.

[0126] 1. Experimental Materials and Methods

[0127] 1. Experimental materials: The peach shell smoke liquid prepared in Example 6 above was used as raw material.

[0128] 2. Preparation steps of smoked horse meat

[0129] Pretreatment of raw materials: Select fresh horse hind leg meat, first remove the fascia on the surface of the horse hind leg meat, and then cut it into uniform pieces of meat. Each piece of meat is weighed to be about 200g, with an error of no more than 5g. Tumble and knead marinating: The proportion of the marinating agent is based on 100g of meat, adding 2.5% salt, 0.4% compound phosphate (sodium pyrophosphate: sodium hexametaphosphate: sodium tripolyphosphate = 2:1:1), 0.05% sodium ascorbate, and 0.009% sodium nitrite. The solvent is distilled water. The marinating liquid is injected into the meat by injection, with an injection rate of 25% (indicates that 25ml of marinating agent is injected for every 100g of horse hind leg meat), and then put into the tumbler. The marinating agent is prepared by adding 2.5g salt, 0.4g compound phosphate, 0.05g sodium ascorbate, and 0.009g sodium nitrite to 25ml of distilled water. Vacuum tumbling and curing conditions: vacuum degree -0.08MPa, tumbling for 3h, rotation speed of 8r / min, tumbling for 20min and stopping for 10min, so that the seasoning agent can fully penetrate into the taste. Liquid smoking: Take out the marinated horse meat and place it in a clean container, soak it in a smoke liquid with a volume fraction of 5% of the horse meat, and place it in 250W ultrasound and 25℃ for liquid smoking for 3h. The preparation steps of the smoke liquid with a volume fraction of 5% are: 5ml of peach shell smoke liquid prepared in Example 6 is mixed with 95ml of sterile water. Cooking: After the raw meat is smoked by liquid smoking, take it out, put it in a pot and cook it at 99℃ for 41min to obtain smoked horse meat products. Packaging: The cooked meat pieces are vacuum packed.

[0130] 2. To study the effects of liquid smoke addition, ultrasonic-assisted immersion time (liquid smoking time), cooking temperature and cooking time on the quality of liquid-smoked horse meat

[0131] 1. Effect of the amount of liquid smoke added on the quality of liquid smoked horse meat

[0132] The liquid smoking time was fixed at 2h, the cooking temperature was fixed at 90℃, the cooking time was 40min, and the amount of smoke liquid added was 1%, 3%, 5%, 7%, 9%, and 11%. A single factor experiment was conducted, and the yield, water activity, pH, color and sensory score were used as indicators to measure and analyze, and the appropriate amount of smoke liquid added was determined.

[0133] 2. Effect of ultrasonic-assisted immersion time on the quality of liquid-smoked horse meat

[0134] A single factor experiment was conducted with the amount of smoked liquid fixed at 5%, the cooking temperature fixed at 90℃, the cooking time fixed at 40min, and the liquid smoking time at 1, 1.5, 2, 2.5, 3, and 3.5h. The yield, water activity, pH, color, and sensory score were used as indicators for measurement and analysis to determine the appropriate ultrasonic-assisted impregnation time.

[0135] 3. Effect of cooking temperature on the quality of liquid-smoked horse meat

[0136] A single factor experiment was conducted with the amount of smoked liquid fixed at 5%, the liquid smoking time fixed at 3h, the cooking time fixed at 40min, and the cooking temperatures at 80℃, 90℃, 100℃, 110℃, and 120℃. The yield, water activity, pH, color, and sensory score were used as indicators for measurement and analysis to determine the appropriate cooking temperature.

[0137] 4. Effect of cooking time on the quality of liquid-smoked horse meat

[0138] A single factor experiment was conducted with the amount of smoked liquid added fixed at 5%, the ultrasonic-assisted immersion time fixed at 3h, the cooking temperature at 100℃, and the cooking times at 20, 30, 40, 50, 60, and 70min. The yield, water activity, pH, color, and sensory score were used as indicators for measurement and analysis to determine the appropriate cooking time.

[0139] 5. Response surface optimization experiment

[0140] Based on the results of the single-factor experiment, the sensory score was selected as the key response indicator, and the four factors of smoke liquid addition, ultrasonic assisted immersion time, cooking temperature and cooking time were determined as independent variables. Subsequently, Design-Expert 13 software was used to conduct a four-factor three-level experimental design. The specific experimental factors and level settings are shown in Table 7. Each set of experimental conditions will be repeated three times to ensure the reliability of the data.

[0141] Table 7 Factors and levels of response surface experiment

[0142]

[0143] 6. Main evaluation indicators and their detection methods

[0144] (1) Sensory evaluation method

[0145] The smoked horse meat products prepared by the above different processes were cut into slices of equal size and taken out for sensory evaluation. A sensory evaluation team was formed by selecting 20 meat product sensory assessors, 10 men and 10 women, and they received relevant training. The color, smell, taste, tissue state and overall acceptability of the liquid smoked horse meat were scored 2 hours after the meal. The specific scoring criteria are shown in Table 8.

[0146] Table 8 Sensory evaluation of smoked horse meat products

[0147]

[0148]

[0149] (2) Determination of yield rate: Weigh the average weight W1 of smoked horse meat before cooking and the average weight W2 after cooking, and calculate according to the following formula: yield rate (%) = W2 / W1×100. (3) Determination of water activity: Refer to the method in GB 5009.238-2016 National Food Safety Standard "Determination of Water Activity in Food". (4) Determination of pH: Refer to the method in GB 5009.237-2016 National Food Safety Standard "Determination of pH Value of Food". (5) Determination of color: The color of smoked horse meat is analyzed using a JZ-300 universal colorimeter. Cut the liquid smoked horse meat into slices of about 3cm×3cm×1cm thick, put them into the colorimeter for measurement, and make three parallel measurements for each sample, and take the average value. Where L* is the brightness value; a* is the redness value; b* is the yellowness value.

[0150] 3. Experimental Results

[0151] 1. Effect of the amount of liquid smoke added on the quality of smoked horse meat

[0152] Table 9 Effect of the amount of liquid smoke added on the physical and chemical indicators of liquid smoked horse meat

[0153] Amount of liquid smoke added (%) 1 3 5 7 9 11 pH <![CDATA[6.12±0.01 a ]]> <![CDATA[5.98±0.01 b ]]> <![CDATA[5.85±0.04 c ]]> <![CDATA[5.57±0.01 d ]]> <![CDATA[5.52±0.00 e ]]> <![CDATA[5.34±0.01 f ]]> Yield rate (%) <![CDATA[73.47±0.35 b ]]> <![CDATA[71.16±0.17 cd ]]> <![CDATA[73.76±0.13 ab ]]> <![CDATA[71.05±0.05 d ]]> <![CDATA[71.47±0.11 c ]]> <![CDATA[73.87±0.12 a ]]> Water content (%) <![CDATA[48.32±0.08 a ]]> <![CDATA[48.21±0.21 bc ]]> <![CDATA[46.26±0.06 c ]]> <![CDATA[46.13±0.03 c ]]> <![CDATA[46.42±0.11 b ]]> <![CDATA[46.20±0.04 c ]]>

[0154] As shown in Table 9, the yield rate of the product is negatively correlated with the loss caused during the processing. There is no significant change in the yield rate and moisture mass fraction of liquid-smoked horse meat under different amounts of smoked liquid added in the present invention (P>0.05), indicating that the amount of smoked liquid added has little effect on the yield rate and water activity of low-sodium bacon. The pH of liquid-smoked horse meat decreased significantly with the increase of smoked liquid (P<0.05), and the pH decreased from 5.87 to 5.33. This is mainly because the phenolic and acidic substances in the smoked liquid lower the pH in the meat products and increase the inhibitory effect of salt on microbial growth. Since the concentration of smoked liquid is positively correlated with the mellowness of the flavor of liquid-smoked horse meat, and when the concentration of smoked liquid is high, the pH of liquid-smoked horse meat is low, which can inhibit the growth of microorganisms and extend the shelf life of liquid-smoked horse meat. Figure 6 As shown in A, with the increase of the amount of liquid smoke added, the L* value of liquid smoked horse meat slowly decreased; the a* value increased in an undulating manner; the b* value increased slowly, and the color difference between different liquid smoke concentration groups was not significant, indicating that the amount of liquid smoke added had little effect on the red and yellow color of meat products. Comprehensively considered, the sensory score was the highest when the amount of liquid smoke added was 5%.

[0155] 2. Effect of ultrasonic-assisted immersion time on the quality of smoked horse meat

[0156] Table 10 Effect of ultrasonic-assisted immersion time on the physical and chemical indices of liquid-smoked horse meat

[0157] Immersion time (h) 1 1.5 2 2.5 3h 3.5h pH <![CDATA[6.12±0.01 a ]]> <![CDATA[6.06±0.01 b ]]> <![CDATA[5.85±0.04 c ]]> <![CDATA[5.76±0.00 d ]]> <![CDATA[5.52±0.00 e ]]> <![CDATA[5.44±0.01 f ]]> Yield rate (%) <![CDATA[71.16±0.15 d ]]> <![CDATA[72.41±0.16 c ]]> <![CDATA[73.24±0.14 b ]]> <![CDATA[73.43±0.17 b ]]> <![CDATA[74.47±0.19 a ]]> <![CDATA[74.45±0.11 a ]]> Water content (%) <![CDATA[47.65±0.59 a ]]> <![CDATA[47.54±0.54 a ]]> <![CDATA[46.26±0.06 b ]]> <![CDATA[45.80±0.55 b ]]> <![CDATA[45.75±0.56 b ]]> <![CDATA[45.53±0.60 b ]]>

[0158] From Table 10, with the increase of ultrasonic assisted immersion time (liquid smoking time), the finished product rate of liquid smoked horse meat showed a slow upward trend. The water activity showed a downward trend, and there was no significant change in the ultrasonic assisted immersion time of 2h to 3.5h (P>0.05), which may be due to the concentration difference between the smoked liquid and the liquid smoked horse meat, resulting in the loss of some free water; as the internal and external osmotic pressure gradually stabilized, this change tended to be gentle; the pH of liquid smoked horse meat showed a downward trend, and the difference between different time groups was significant (P<0.05), which may be due to the phenolic substances and acidic substances in the smoked liquid slowly penetrating into the meat products during the liquid smoking process. After a certain period of liquid smoking, the smoked liquid has difficulty penetrating into the meat, so the pH of liquid smoked horse meat products decreases slowly. Figure 6 From B, we can see that with the extension of ultrasonic assisted immersion time, the L* value increases slowly, reaches the maximum value at 3h, and is significantly higher than (P<0.05) 1, 1.5, 2, 2.5h groups; there is no significant difference in a* value between different liquid fumigation time groups (P>0.05); b* value increases slowly, reaches the maximum value at 3h, and has no significant change with the 3.5h group (P>0.05). Taking into account, the ultrasonic assisted immersion time of 3h is the highest sensory score, so the ultrasonic assisted immersion time of 2.5h, 3h, and 3.5h are selected as the liquid fumigation time levels of the response surface optimization experiment.

[0159] 3. Effect of cooking temperature on the quality of liquid-smoked horse meat

[0160] Table 11 Effect of cooking temperature on the physical and chemical indexes of liquid smoked horse meat

[0161]

[0162] As shown in Table 11, with the increase of cooking temperature, the finished product rate, water activity and pH of liquid smoked horse meat showed a steady downward trend. When the cooking temperature was between 80℃ and 130℃, there were significant differences in the finished product rate and water mass fraction of liquid smoked horse meat (P<0.05). When the cooking temperature was 80℃, the water activity of liquid smoked horse meat was high, which was not conducive to the preservation of liquid smoked horse meat. Baking at too high a temperature would denature the protein in liquid smoked horse meat, affecting the taste and nutritional value of liquid smoked horse meat. Figure 6It can be seen from the C that the brightness value of liquid-smoked horse meat tends to decrease with the increase of temperature, and there is no significant difference when the cooking temperature is between 110℃ and 130℃ (P>0.05). Combined with the comprehensive processing cost and the sensory quality of liquid-smoked horse meat, cooking temperatures of 90℃, 100℃ and 110℃ were selected as the temperature levels of the response surface optimization experiment.

[0163] 4. Effect of cooking time on the quality of liquid-smoked horse meat

[0164] Table 12 Effect of cooking temperature on the physical and chemical indexes of liquid smoked horse meat

[0165]

[0166] As shown in Table 12, the yield and moisture content of liquid smoked horse meat were significantly affected by cooking time (P<0.05), but had no significant effect on the pH of liquid smoked horse meat (P>0.05). Figure 6 It can be seen from the D that cooking time has a significant effect on the color of liquid-smoked horse meat (P<0.05). As the cooking time increases, the brightness value L* shows a stable upward trend, and there is a significant difference when the cooking time is 20-60min (P<0.05). The yellowness value b* and redness value a* of liquid-smoked horse meat increase with time. Among them, the a* value of liquid-smoked horse meat cooked for 40min is the highest, which is significantly higher than other groups (P<0.05), indicating that with the extension of time, the color of the surface of liquid-smoked horse meat becomes darker and darker, from bright red to dark red, and the red color deepens. Combined with the comprehensive processing cost and the sensory quality of liquid-smoked horse meat, cooking times of 30min, 40min, and 50min were selected as the time levels of the response surface optimization experiment.

[0167] 5. Response surface optimization of smoked horse meat preparation process

[0168] (1) Response surface experimental design and results

[0169] According to the above single-factor experimental results, Design-Expert 13 software was used, and in accordance with the Box-Behnken design concept, sensory scores were selected as response values. A response surface analysis with four factors and three levels was performed, and a total of 17 experimental points were set. This process aims to explore the impact of different factors on sensory scores and optimize experimental conditions. The design combination and results are shown in Table 13.

[0170] Table 13 Response surface design scheme and results

[0171]

[0172] (2) Model establishment and significance analysis

[0173] The Design-Expert 13 software was used to perform variance analysis on the results of the liquid-smoked horse meat process experiment, and the quadratic polynomial regression equation of the sensory score Y of liquid-smoked horse meat with A, B, and C was obtained as follows: Y = 31.47 + 0.6736×A + 0.3643×B + 0.0701×C - 0.0173×A×B - 0.1475×A×C - 0.1083×B×C - 3.78×A² - 1.94×B² - 1.99×C². The results of the variance analysis of the regression model are shown in Table 14.

[0174] Table 14 Variance Analysis of the Sensory Score Regression Model

[0175] Sources of variance sum of squares Degrees of Freedom Mean Square F-number P-value Significance Model 363.38 14 25.96 66.9 <0.0001 ** A-Amount of liquid smoke added 59.01 1 59.01 152.1 <0.0001 ** B-Ultrasonic assisted immersion time 13.48 1 13.48 34.75 <0.0001 ** C-cooking temperature 0.7803 1 0.7803 2.01 0.178 D-cooking time 1.48 1 1.48 3.81 0.0713 * AB 2.71 1 2.71 6.98 0.0194 * AC 0.1406 1 0.1406 0.3625 0.5568 AD 1.16 1 1.16 2.98 0.1064 BC 0.5112 1 0.5112 1.32 0.2702 BD 0.0729 1 0.0729 0.1879 0.6713 CD 0.8649 1 0.8649 2.23 0.1576 <![CDATA[A 2 ]]> 238.62 1 238.62 615.07 <0.0001 ** <![CDATA[B 2 ]]> 72.64 1 72.64 187.24 <0.0001 ** <![CDATA[C 2 ]]> 18.45 1 18.45 47.56 <0.0001 ** <![CDATA[D 2 ]]> 51.5 1 51.5 132.75 <0.0001 ** Residual 5.43 14 0.388 Lack of Fit 4.83 10 0.4829 3.21 0.1362 Pure Error 0.6019 4 0.1505 Total deviation 368.82 28

[0176] Note: "*" indicates significant difference (0.01 < P < 0.05), "**" indicates extremely significant difference (P < 0.01), and "#" indicates no significant difference (P > 0.05).

[0177] The results are shown in Table 14 and Figure 7 to Figure 9 as follows. All models reached significance. According to the significance analysis of the influence of each factor based on the P value and F value, the result was that each factor had a significant influence on the carbonyl compound content in the walnut shell smoke solution. The p value of this model was < 0.0001, and the p value of the lack-of-fit term of the equation was 0.1362, indicating that the fitting degree of the equation was good. In addition, the coefficient of variation (CV) of the model was 0.7824%, indicating that this experiment was precise and reliable and could be used for statistical analysis. Among them, A and B were significant, indicating that the addition amount of the smoke solution and the ultrasonic-assisted impregnation time had a greater influence on the sensory score of liquid-smoked horse meat. From the F value, the order of the influence of the three factors on the carbonyl compound content in the walnut shell smoke solution was: A > B > D > C, that is, the addition amount of the smoke solution > the ultrasonic-assisted impregnation time > the boiling time > the boiling temperature.

[0178] (3) Analysis of the Four-Factor Response Surface Three-Dimensional Model

[0179] The contour plot and response surface plot based on the regression model are shown. The shape of the contour provides intuitive information about the significance of factor interactions: an ellipse indicates an extremely significant interaction effect, while a circle indicates an insignificant interaction. In addition, the slope change of each factor on the response surface reflects their influence intensity on the sensory score of liquid-smoked horse meat. The steeper the slope, the more significant the influence of the factor.

[0180] (4) Prediction and Verification of the Optimal Conditions

[0181] The optimal process conditions for liquid smoked horse meat were obtained through regression simulation as follows: the amount of smoked liquid added was 5.3968%, the ultrasonic assisted immersion time was 2.910h, the cooking temperature was 99.30℃, and the cooking time was 40.80min. The sensory score of liquid smoked horse meat was 85.7106. The process conditions for liquid smoked horse meat were adjusted according to actual operation as follows: the amount of smoked liquid added was 5%, the ultrasonic assisted immersion time was 3h, the cooking temperature was 99℃, and the cooking time was 41min. Three parallel tests were carried out under these conditions to prepare liquid smoked horse meat. The actual sensory score was 85.72±0.19, which was close to the theoretical value. Therefore, the quadratic model established was consistent with the actual situation.

[0182] Although preferred embodiments of the present invention have been described, additional changes and modifications may occur to these embodiments once those skilled in the art are aware of the basic inventive concepts.

[0183] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing walnut shell smoked liquid, characterized in that: The steps include: The walnut shells are dried at 90°C to 100°C to a moisture content of 7% to 10% by mass, crushed, and sieved through a 10-mesh to 30-mesh sieve to obtain a spice powder, and then sucrose accounting for 12.0% to 14.0% by mass of the spice powder is added; Then, walnut shell smoke liquid is obtained through dry distillation, condensation and filtration in sequence; The dry distillation temperature is 400° C. to 450° C., and the dry distillation time is 20 min to 40 min.

2. The method for preparing walnut shell smoked liquid according to claim 1, characterized in that: The mass fraction of sucrose is 14.0%.

3. The method for preparing walnut shell smoked liquid according to claim 1, characterized in that: The filtration comprises: first filtering with a filter pore diameter of 0.45 μm to 0.80 μm to obtain refined smoked liquid, then adding pretreated XAD-4 macroporous adsorption resin, shaking and culturing at 30° C. to 32° C. and 120 r / min to 130 r / min for 20 h to 24 h, and filtering the macroporous adsorption resin with a filter pore diameter of 0.45 μm to 0.80 μm to obtain walnut shell smoked liquid; The preparation process of the pretreated XAD-4 macroporous adsorption resin is as follows: The XAD-4 macroporous adsorption resin was soaked in ethanol and then washed, and then soaked in 3 to 4 times the volume of HCl solution and NaOH solution for 2 to 2.5 hours, and then washed with distilled water until neutral.

4. The method for preparing walnut shell smoked liquid according to claim 3, characterized in that: The usage ratio of the refined smoke liquid to the pretreated XAD-4 macroporous adsorption resin is 10mL-12mL:1g.

5. Walnut shell smoking liquid prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the walnut shell smoking liquid according to claim 5 in preparing smoked horse meat.

7. The use according to claim 6, characterized in that: The preparation steps of the smoked horse meat include pretreatment of raw materials, tumbling and curing, liquid smoking and boiling; The liquid smoking process is as follows: soaking the tumbled and marinated horse meat in a diluent of smoke liquid, placing it in a 250W ultrasonic wave at 30°C for liquid smoking for 2.5h to 3h; the amount of smoke liquid added to the diluent of smoke liquid is 3% to 5% by volume; The cooking process is as follows: the liquid-smoked horse meat is cooked at 95°C to 100°C for 35min to 45min to obtain the smoked horse meat.

8. The use according to claim 7, characterized in that: The amount of smoke liquid added to the smoke liquid diluent is 5% by volume, the ultrasonic liquid fumigation time is 3 hours, the cooking temperature is 99° C., and the cooking time is 41 minutes.

9. The use according to claim 7, characterized in that: The pretreatment process of the raw materials is as follows: fresh horse hind leg meat is selected, the fascia on the surface is removed, and the meat is cut into blocks weighing 195 g to 205 g.

10. The use according to claim 7, characterized in that: The tumbling and kneading pickling process is as follows: 2.0% to 2.5% of salt, 0.3% to 0.4% of composite phosphate, 0.04% to 0.05% of sodium ascorbate and 0.008% to 0.009% of sodium nitrite are injected into the pretreated horse hind leg meat, and then vacuum tumbling and kneading pickling is performed.

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