Idesia oil aroma enhancement process

Abstract

The invention relates to the technical field of edible oil, in particular to an aroma enhancement process of idesia oil. According to the method, the idesia pulp enzymatic hydrolysate is used as an aroma-producing source, and the aroma of the idesia refined oil is enhanced. The optimal parameters of the idesia oil aroma enhancement process are determined by a response surface method as follows: the material-oil ratio is 1: 12, the reaction temperature is 121 DEG C, and the heating reaction time is 37 minutes. Under the condition, the comprehensive sensory score of the idesia oil is 9.16. 84 volatile substances are totally identified through a GC-IMS technology. The contents of acids, esters and other substances in the aroma-enhanced idesia oil are increased, and the contents of aldehydes, alcohols and ketones are reduced.

Description

Technical Field

[0001] This invention relates to the field of edible oil technology, specifically a process for enhancing the aroma of tung oil. Background Technology

[0002] Idesia polycarpa Maxim., a woody oilseed plant of significant economic value, has garnered widespread attention due to its excellent adaptability, high survival rate, and low cultivation costs. Idesia polycarpa oil is rich not only in higher fatty acids but also in various natural bioactive substances such as tocopherols, sterols, and squalene, which endow it with potential medicinal and edible value. However, during extraction, Idesia polycarpa oil often exhibits a dark color and is accompanied by a bitter taste and unpleasant odor, requiring refining to improve its quality. Our research team discovered that while refining effectively removes undesirable flavors and enhances stability, it also leads to the loss of natural aroma components, resulting in a less fragrant refined Idesia polycarpa oil. Currently, research on aroma-enhancing techniques for Idesia polycarpa oil is limited.

[0003] The Maillard reaction is a series of complex reactions between amino and carbonyl compounds. The reaction products affect the color, flavor, sensory characteristics, and nutritional value of food, and are currently widely used to enhance the aroma properties of oils. Liu Chunxiao et al. successfully prepared a richly aromatic sesame oil by using the enzymatic hydrolysate of sesame meal and refined sesame oil to conduct a Maillard reaction. Yang Ning et al. and Guo Jinting et al. also optimized the aroma-enhancing process of porcini mushroom flavored oil and sunflower seed oil through the Maillard reaction, respectively, giving the products unique flavor characteristics. After oil extraction from *Vernicia fordii* seeds, a large amount of *Vernicia fordii* meal is produced, with a crude protein content of over 12%.

[0004] Therefore, finding a method that can enhance the aroma of tung oil and effectively improve the utilization rate of tung oil meal by-products is currently a key research direction. Summary of the Invention

[0005] To address the aforementioned technical problems in the existing technology, the present invention provides a process for enhancing the aroma of *Vernicia fordii* seed oil, comprising the following steps:

[0006] A process for enhancing the aroma of tung oil involves mixing enzymatic hydrolysate of tung oil meal with refined tung oil and heating the mixture. After the reaction is complete, the mixture is cooled to 40°C–50°C, filtered to remove impurities, and the resulting tung oil is flavored.

[0007] Furthermore, the mixing ratio of the enzymatic hydrolysate of *Vernicia fordii* meal to the refined oil of *Vernicia fordii* is a volume ratio of (1:9) to (1:12), preferably 1:12.

[0008] Furthermore, the heating reaction temperature is 115-130℃, preferably 121℃.

[0009] Furthermore, the heating reaction time is 30-50 minutes, preferably 37 minutes.

[0010] Furthermore, the heating reaction involves placing the raw materials in a constant-temperature heating magnetic stirrer, setting an oil bath to heat to a preset reaction temperature, and maintaining a constant reaction time for the heating reaction.

[0011] Furthermore, the enzymatic hydrolysate of *Vernicia fordii* meal is an enzymatic hydrolysate obtained by enzymatic hydrolysis of *Vernicia fordii* meal with alkaline protease and flavor protease, respectively.

[0012] Furthermore, the enzymatic hydrolysate of *Vernicia fordii* meal is prepared by the following method:

[0013] Crush and sieve the tung oil seed meal. Mix the tung oil seed meal with deionized water at a ratio of (1:6) to (1:10), adjust the pH to (8.5-9.5), and add 3500-4500 U / g of alkaline protease at 50-60℃ for enzymatic hydrolysis for 2-4 hours. After hydrolysis, heat the hydrolysate to 85-95℃ for 5-15 minutes to inactivate the enzyme. After the mixture cools, adjust the pH to 6-7, add 800-1200 U / g of flavor protease, and hydrolyze at 55-65℃ for 3-5 hours. After inactivating the enzyme again, centrifuge the mixture and separate the supernatant for later use.

[0014] The preferred method is as follows:

[0015] The pulp of *Vernicia fordii* seeds was crushed and sieved to increase its surface area and promote subsequent enzymatic hydrolysis. Based on the previous optimization of enzymatic hydrolysis conditions in the laboratory, *Vernicia fordii* seed pulp and deionized water were mixed at a material-to-liquid ratio of 1:8, the pH was adjusted to 9, and 4000 U / g of alkaline protease was added at 55℃ for 3 hours of enzymatic hydrolysis. After the enzymatic hydrolysis was completed, the hydrolysate was heated to 90℃ for 10 minutes to inactivate the enzyme. After the mixture cooled, the pH was adjusted to 6.5, and 1000 U / g of flavor protease was added for enzymatic hydrolysis at 60℃ for 4 hours. After another enzyme inactivation treatment, the mixture was centrifuged, and the supernatant was separated for later use.

[0016] Furthermore, the process involves mixing the tung oil seed meal with deionized water at a ratio of 1:8, where the ratio is a mass ratio.

[0017] Furthermore, the centrifugation is specifically performed at 4000 r / min for 15 min.

[0018] A scented oil made from *Vernicia fordii* seeds is prepared using the aforementioned scenting process for *Vernicia fordii* seeds.

[0019] Compared with the prior art, the technical effects of this invention are reflected in:

[0020] This application uses the enzymatic hydrolysate of *Vernicia fordii* meal as the aroma source to enhance the aroma of refined *Vernicia fordii* oil. Response surface methodology was used to determine the optimal parameters for the aroma enhancement process: a feed-to-oil ratio of 1:12, a reaction temperature of 121℃, and a heating reaction time of 37 minutes. Under these conditions, the overall sensory score of the aroma-enhanced *Vernicia fordii* oil was 9.16. GC-IMS technology identified 84 volatile compounds. The aroma-enhanced *Vernicia fordii* oil showed an increase in the content of acids, esters, and other compounds, while the content of aldehydes, alcohols, and ketones decreased. Based on OAV values, 35 key flavor compounds were screened. Among them, the aroma-enhanced *Vernicia fordii* oil showed increased concentrations of volatile compounds such as 2-methylpropionic acid, butyraldehyde, 3-methylbutyraldehyde, 2-methylpropionaldehyde, phenylacetaldehyde, and 2-acetylthiazole, which endowed it with rich fruity, fatty, and meaty flavor characteristics. The concentration of volatile substances such as 1-octen-3-ol, 1-octen-3-one, 1-penten-3-one, and diacetyl in the flavored *Vernicia fordii* oil decreased, thus reducing unpleasant odors such as earthiness, mushroominess, and irritation. Further sensory analysis of the flavored *Vernicia fordii* oil revealed that it outperformed unflavored refined *Vernicia fordii* oil in terms of roasting aroma, caramel aroma, and overall score. There were no significant differences between the flavored and refined oils in terms of fatty acid composition, acid value, peroxide value, color, and saponification value, indicating that the flavoring process did not negatively impact the basic quality of the *Vernicia fordii* oil. These findings provide a scientific basis for flavor improvement and product diversification of *Vernicia fordii* oil, and also open up new avenues for the efficient utilization of *Vernicia fordii* meal byproducts. In the future, our team will further investigate the effects of potential variables such as enzymatic hydrolysis time and temperature on the aroma generation of *Vernicia fordii* oil, the aroma stability and persistence of the flavored *Vernicia fordii* oil in practical applications, and the quality changes under different storage conditions, in order to further evaluate its application potential in the food industry and provide better guidance for the industrial production process of flavored *Vernicia fordii* oil. Attached Figure Description

[0021] Figure 1 This is a flowchart of the aroma-enhancing process for tung oil in this application.

[0022] Figure 2 This study examines the effect of the ratio of raw material to oil on the sensory quality of the aroma-enhancing oil from *Vernicia fordii*.

[0023] Figure 3 This study investigates the effect of reaction temperature on the sensory quality of the aroma-enhancing oil from *Vernicia fordii*.

[0024] Figure 4 This study examines the effect of reaction time on the sensory quality of the aroma-enhancing oil from *Vernicia fordii*.

[0025] Figure 5These are contour lines and three-dimensional response surfaces representing the overall sensory score of the aroma-enhancing oil from *Vernicia fordii* due to the interaction of various factors.

[0026] Figure 6 Two-dimensional spectra (a) and differential comparison spectra (b) of refined oil and flavoring oil from *Vernicia fordii*.

[0027] Figure 7 It is the fingerprint spectrum of refined oil and flavoring oil from *Vernicia fordii*.

[0028] Figure 8 This is a bar chart showing the volatile matter content of refined oil and flavoring oil from *Vernicia fordii*.

[0029] Figure 9 This is a radar chart showing the sensory ratings of refined tung oil and flavoring oil from tung trees. Detailed Implementation

[0030] The technical solution of the present invention will be further defined below with reference to specific embodiments, but the scope of protection is not limited to the description made.

[0031] 1. Materials and Methods

[0032] 1.1 Materials and Instruments

[0033] The *Vernicia fordii* cake and refined *Vernicia fordii* oil were provided by the Forestry and Grassland *Vernicia fordii* Processing and Comprehensive Utilization Engineering Technology Center; diethyl ether and chloroform (analytical grade) were from Beijing Macklin Company; alkaline protease (20000 U / g) and flavor protease (30000 U / g) were from Beijing Solarbio Science & Technology Co., Ltd.; 2-octanol (chromatographic grade) was from Macklin Reagent Company; potassium chloride, sodium thiosulfate, sodium hydroxide, hydrochloric acid, glacial acetic acid, phenolphthalein, starch, potassium iodide, etc. (analytical grade) were from Tianjin Mio Chemical Reagent Co., Ltd.; n-ketones: 2-butanone, 2-pentanone, 2-hexanone, 2-heptanone, 2-octanone, and 2-nonanone (all analytical grade) were from Aladdin Company; 2-octanol (chromatographic grade) was from Aladdin Company.

[0034] HD-5 Water Activity Analyzer, Wuxi Huake Instrument Co., Ltd.; DF-101Z Thermostatic Heating Magnetic Stirrer, Zhengzhou Changcheng Science & Industry Trade Co., Ltd.; LC-FA2204 Electronic Analytical Balance, Shanghai Lichen Bangxi Instrument Technology Co., Ltd.; PHS-3C pH Meter, Shanghai Yidian Scientific Instrument Co., Ltd.; JC-NY 20B Fully Automatic Kjeldahl Nitrogen Analyzer, Qingdao Jingcheng Instrument Co., Ltd.; TGL-16A High-Speed ​​Refrigerated Centrifuge, Hunan Pingfan Technology Co., Ltd.; Agilent 8890 Gas Chromatograph, Agilent Technologies Inc. Flavor analyzer, Shandong Haineng Scientific Instruments Co., Ltd.

[0035] 1.2 Experimental Methods

[0036] 1.2.1 Preparation of enzymatic hydrolysate of tung oil seed meal

[0037] The pulp of *Vernicia fordii* seeds was crushed and sieved to increase its surface area and promote subsequent enzymatic hydrolysis. Based on previous optimization of enzymatic hydrolysis conditions in the laboratory, *Vernicia fordii* seed pulp and deionized water were mixed at a material-to-liquid ratio (mass ratio) of 1:8, the pH was adjusted to 9, and 4000 U / g of alkaline protease was added at 55℃ for 3 hours of enzymatic hydrolysis. After hydrolysis, the hydrolysate was heated to 90℃ for 10 minutes to inactivate the enzyme. After the mixture cooled, the pH was adjusted to 6.5, and 1000 U / g of flavor protease was added for 4 hours of enzymatic hydrolysis at 60℃. After another enzyme inactivation treatment, the mixture was centrifuged (4000 r / min, 15 min), and the supernatant was separated for later use.

[0038] 1.2.2 Preparation of Flavoring Oil from *Vernicia fordii* Seeds

[0039] The enzymatic hydrolysate of *Vernicia fordii* meal and refined *Vernicia fordii* oil were mixed at a specific volume ratio and placed in a constant-temperature magnetic stirrer. The mixture was heated in an oil bath to a preset reaction temperature and maintained for a constant reaction time. After the reaction was complete, the mixture was allowed to cool to 40℃~50℃, then filtered to remove impurities, yielding *Vernicia fordii* flavored oil. The process flow is as follows: Figure 1 As shown.

[0040] 1.2.3 Single-factor experiment on aroma-enhancing oil from *Vernicia fordii* seeds

[0041] The effects of different material-to-oil volume ratios (1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15) on the sensory properties of *Vernicia fordii* aroma oil were investigated under the conditions of a fixed Maillard reaction time of 30 min and a material-to-oil ratio of 1:12 (volume ratio). The effects of different Maillard reaction temperatures (105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃) on the sensory properties of *Vernicia fordii* aroma oil were also investigated under the conditions of a fixed Maillard reaction temperature of 115℃ and a material-to-oil ratio of 1:12 (volume ratio).

[0042] 1.2.4 Optimization of Flavoring Oil from *Vernicia fordii* using Response Surface Methodology

[0043] Based on the results of single-factor experiments, response surface methodology (RSM) and Box-Behnken design model were used to construct mathematical models relating heating time, heating temperature, and oil-to-material ratio to sensory scores. Model analysis was used to determine the order of influence of each factor on the quality of the flavored oil and to identify the optimal combination of process parameters.

[0044] Table 1 Response surface experimental factor level table

[0045]

[0046] 1.2.5 Establishment of a Sensory Evaluation System

[0047] A sensory evaluation team of 8 experienced fragrance tasters (4 men and 4 women) was formed, and professional sensory training was provided to ensure the accuracy and consistency of the evaluation. Sensory evaluation criteria were established, including descriptive terms such as toasted aroma, caramel aroma, tung oil aroma, and burnt aroma, and a certain concentration of the sample was used as a reference (this concentration of reference was worth 10 points). Blind evaluation of the samples was conducted under constant temperature conditions to ensure the impartiality of the evaluation. Each sample was evaluated three times. The weighting values ​​were determined by the sensory evaluators based on their assessment and scoring of the importance of each indicator. The sensory evaluation criteria are shown in Table 2.

[0048] Table 2 Evaluation standard of flavor intensity of idesia polycarpa Maximoil

[0049]

[0050] 1.2.6 Analysis of volatile substances in refined oil and flavoring oil of *Vernicia fordii*

[0051] 1.2.6.1 Sample preparation method

[0052] Weigh 1g of sample into a 20mL headspace vial, add 50μL of 100mg / L internal standard 2-octanol, incubate at 80℃ for 20min, and then inject the sample. Each sample is measured in triplicate.

[0053] 1.2.6.2 Headspace injection conditions

[0054] Incubation temperature: 80℃; Incubation time: 20min; Injection volume: 500μL; Splitless injection; Incubation speed: 500r / min; Injection needle temperature: 85℃.

[0055] 1.2.6.3 GC Conditions:

[0056] Column temperature: 60℃; Carrier gas: High-purity nitrogen (purity ≥99.999%); Programmed pressure: Initial flow rate 2.0 mL / min, held for 2 min, linearly increased to 10.0 mL / min within 8 min, linearly increased to 100.0 mL / min within 10 min, held for 40 min. Chromatographic run time: 60 min; Injector temperature: 80℃.

[0057] 1.2.6.4 IMS Conditions

[0058] Ionization source: tritium source (3H); migration tube length: 53 mm; electric field strength: 500 V / cm; migration tube temperature: 45℃; drift gas: high-purity nitrogen (purity ≥99.999%); flow rate: 75.0 mL / min; positive ion mode. 2 mL of sample was placed in a 20 mL headspace vial and incubated at 60℃ and 500 r / min for 15 min. Automatic sampling was performed, with an injection volume of 500 μL and a needle temperature of 85℃.

[0059] Qualitative and quantitative analysis of volatile substances: A calibration curve for the retention time and retention index of ketones (C4-C9) was established, and the retention index (RI) of volatile substances was calculated. The GC retention index (NIST 2020) database and IMS migration time database built into the VOCal software were used to perform qualitative analysis of volatile substances in the sample. Based on the known content of the internal standard 2-octanol and the principle that the peak area of ​​volatile substances is proportional to the content, the content of unknown volatile substances was calculated according to formula (2):

[0060]

[0061] Among them, t x Let t be the retention time of compound x. n and t n+1 t represents the retention times of n and n+1 n-alkanes, respectively, and t n <t x <t n+1 .

[0062]

[0063] In formula (1): Cx is the content of the unknown compound (μg / g); C0 is the concentration of the internal standard (mg / L); V0 is the injection volume of the internal standard (μL); S x S0 is the peak area of ​​the unknown compound; S0 is the peak area of ​​the internal standard; m is the mass of the sample (g).

[0064] 1.2.7 Odor Activity Value (OAV) Analysis

[0065] The odor activity value (OAV) of volatile substances is calculated to assess their contribution to the overall flavor profile. Compounds with an OAV ≥ 1 are generally considered to contribute significantly to the overall flavor profile. The calculation formula is as follows.

[0066]

[0067] In formula (2): Cx is the content of volatile flavor substances (μg / g); Tx is the olfactory and taste threshold of the flavor substance in water.

[0068] 1.2.8 Fatty acid composition analysis of refined oil and flavoring oil from *Vernicia fordii* seeds

[0069] Gas chromatography (GC) was used for determination. The sample pretreatment of refined tung oil and flavoring oil from *Vernicia fordii* was referenced from Zhou Kang et al.

[13] Methods. Gas chromatographic conditions: The gas chromatographic column was an SH-Rt-2560 capillary column (100m x 0.25mm x 0.20μm), and the detector was an FID detector. A programmed temperature rise was used: initial temperature 130℃, held for 5 min, then increased to 240℃ at a rate of 4℃ / min and held for 20 min. Carrier gas: nitrogen; column flow rate: 1.0 mL / min; injection port temperature: 240℃; detector temperature: 240℃; split ratio: 20:1; injection volume: 1 μL.

[0070] 1.2.9 Quality Index Analysis of Refined Oil and Flavoring Oil from *Vernicia fordii*

[0071] The determination of acid value in refined tung oil and flavoring oil of *Vernicia fordii* was carried out in accordance with the national food safety standard GB 5009.229-2016; the determination of peroxide value was carried out in accordance with the national food safety standard GB 5009.227-2016; the determination of iodine value was carried out in accordance with the national food safety standard GB / T 5532-2008; the determination of saponification value was carried out in accordance with the national food safety standard GB / T 5534-2008; the determination of moisture content was carried out in accordance with the national food safety standard GB 5009.236-2016; and the determination of oil color was carried out in accordance with the national food safety standard GB 5009.236-2016. (Note: The original text contains some formatting errors and inconsistencies. A more accurate translation would require the full context.)

[14] The method was slightly modified. 3 mL of refined tung oil and flavoring oil were respectively placed in white glass lab dishes, and the L (volume) of the oils was measured using a colorimeter. * (brightness), a * (yellowness), b * (Redness) value. Each test was repeated 3 times.

[0072] 1.3 Data Processing

[0073] SPSS Statistics 20 software was used for analysis of variance (ANOVA) and Duncan's multiple comparison test significance analysis. Origin-2021 software was used to generate bar charts and flavor profiles. Excel was used for data statistical analysis and tabulation. Response surface methodology software Design-Expert 11 was used for response surface regression analysis of variance to establish a quadratic regression multinomial model. Six ketones were tested in a mixed standard, and calibration curves for retention time and retention index were established. The retention index of the target substance was then calculated based on its retention time. The VOCal software's built-in GC retention index (NIST 2020) database and IMS migration time database were used for retrieval and comparison to perform qualitative analysis of the target substance. VOCal data processing software's Reporter and Gallery Plot plugins were used to generate two-dimensional spectra, differential spectra, and fingerprint spectra of volatile components for comparison of volatile organic compounds between samples.

[0074] 2 Results and Analysis

[0075] 2.1 Results of Single-Factor Experiments on Aroma Enhancement Process of Refined Oil from *Vernicia fordii*

[0076] 2.1.1 Effect of the ratio of raw material to oil on the aroma-enhancing effect of tung oil

[0077] The ratio of enzymatic hydrolysate to refined tung oil is also a crucial parameter affecting the Maillard reaction and final flavor formation. This study investigated the influence of different hydrolysate-to-oil ratios on the aroma-enhancing effect of tung oil, aiming to find the optimal ratio and thus optimize the aroma-enhancing process. The hydrolysate-to-oil ratio directly affects the interaction between the enzymatic hydrolysate and refined tung oil, thereby influencing the generation and transformation of flavor compounds. A lower ratio may result in insufficient concentration of flavor precursors in the hydrolysate, while an excessively high ratio may dilute these flavor compounds, affecting the final flavor quality. Results are as follows... Figure 2 As shown, with the increase of the material-to-oil ratio, the overall sensory score of the *Vernicia fordii* flavoring oil exhibits a trend of first stabilizing and then decreasing. When the material-to-oil ratio is within the range of 1:9 to 1:12, the sensory score is relatively stable, indicating that the generation and transformation of flavor substances reach a balance within this range. When the material-to-oil ratio exceeds 1:12, the sensory score of the flavoring oil begins to decline. This may be because the excessive oil content dilutes the flavor precursors in the enzymatic hydrolysate, resulting in insufficient generation of flavor substances and affecting the final flavor quality. Therefore, based on the experimental results, a material-to-oil ratio of 1:12 was determined to be the optimal ratio for the *Vernicia fordii* oil flavoring process, serving as a factor parameter for subsequent response surface methodology experiments.

[0078] 2.1.2 Effect of reaction temperature on the aroma-enhancing effect of tung oil

[0079] Reaction temperature is a crucial factor regulating the Maillard reaction and influencing the final flavor characteristics. In this study, we investigated the effect of different reaction temperatures on the aroma-enhancing effect of *Vernicia fordii* oil. Lower reaction temperatures tend to generate low-molecular-weight, mild-flavored aroma compounds. As the reaction temperature increases, it promotes the formation of high-molecular-weight, more intense, and complex aroma compounds. However, excessively high reaction temperatures may lead to the formation of undesirable flavor compounds, such as bitterness and burnt taste, which could negatively impact the sensory quality of the final product. [15 , 16] The result is as follows Figure 3 As shown, with increasing reaction temperature, the roasted aroma, caramel aroma, and overall score of the *Vernicia fordii* flavoring oil all exhibit a trend of first increasing and then decreasing. When the reaction temperature reaches 120℃, the overall score of the *Vernicia fordii* flavoring oil reaches its highest point, indicating the optimal flavor at this temperature, and undesirable flavors such as burnt aroma have not yet significantly increased. As the reaction temperature continues to rise, the burnt aroma gradually intensifies and becomes dominant, leading to a decrease in the sensory score. This may be because the high temperature intensifies the reaction, causing the aroma source to overreact, generating excessive bitterness or other harmful substances. Therefore, based on the experimental results, 120℃ was determined as the optimal reaction temperature in the *Vernicia fordii* oil flavoring process, and this temperature was used as a factor parameter in subsequent response surface methodology experiments.

[0080] 2.1.3 Effect of reaction time on the aroma-enhancing effect of tung oil

[0081] Reaction time is one of the key parameters determining the aroma enhancement effect of *Vernicia fordii* oil. This study investigated the effect of different reaction times on the aroma enhancement effect of *Vernicia fordii* oil under fixed material-to-oil ratio and reaction temperature conditions. Experimental results showed that the reaction time directly affects the formation and transformation of flavor compounds. When the reaction time is insufficient, intermediate products are not completely converted into flavor compounds, resulting in poor aroma enhancement. With prolonged reaction time, the aroma-generating reaction is more complete, and the amount of flavor compounds generated increases, thereby improving the aroma quality of *Vernicia fordii* oil. However, excessively long reaction times may promote excessive caramelization, producing unpleasant bitterness and burnt flavors, while also deepening the color of the oil, adversely affecting sensory quality. [10 , 17] .Depend on Figure 4 As shown, with the reaction time increasing from 20 min to 40 min, the roasting aroma, caramel aroma, and overall sensory score of the *Vernicia fordii* flavoring oil all showed an upward trend. At a reaction time of 40 min, the overall score of the *Vernicia fordii* flavoring oil reached its highest point, with a relatively mild burnt flavor and optimal flavor effect. Further extending the reaction time to over 50 min caused the sensory score to begin to decline, and the burnt flavor to significantly intensify, indicating that excessively long reaction times negatively impacted the overall flavor of the oil. Based on the above analysis, 40 min was determined to be the optimal reaction time in the *Vernicia fordii* oil flavoring process, and this was used as a parameter in subsequent response surface methodology experiments.

[0082] 2.2 Analysis of Response Surface Optimization Results

[0083] 2.2.1 Results of Response Surface Methodology Tests

[0084] Based on single-factor experiments, and following the Box-Behnken experimental design principle, response surface methodology was used to optimize three key parameters of the aroma-enhancing process of *Vernicia fordii* oil: material-to-oil ratio (A), reaction temperature (B), and reaction time (C). The experimental design and results are shown in Table 3, and the analysis of variance results are as follows.

[0085] Table 3 Response surface experimental design and results of aroma-enhanced oil of Idesia polycarpa Maxim.

[0086]

[0087]

[0088] Table 4. Comprehensive score regression equation analysis of variance table

[0089]

[0090] Note: * indicates significant (P<0.05), ** indicates highly significant (P<0.01)

[0091] 2.2.2 Analysis of variance for fitting the regression equation

[0092] Using Design Expert 11 software, a multiple regression fitting analysis was performed on the experimental data, yielding the following bivariate multinomial regression model: Overall sensory score Y = 9.12 - 0.6A + 0.5875B - 0.3125C + 0.05AB - 0.175BC - 0.7475A 2 -1.1225B 2 -0.5225C 2 The regression statistical analysis results are shown in Table 4. The regression model was highly significant (P < 0.0001), the lack-of-fit term P = 0.1116 (P > 0.05), and the coefficient of determination R0.05 was [missing value]. 2 =0.9828, adjusted coefficient of determination R 2 adj=0.9606, indicating that the equation has high reliability and the model fits well, and can be used to predict and analyze the optimization results of the aroma-enhancing process of *Vernicia fordii* oil. Based on the F-value, the influence of each factor on the overall sensory score is determined as follows: oil-to-material ratio A > reaction temperature B > reaction time C. The effects of the first-order terms of the equation on the overall sensory score of *Vernicia fordii* aroma-enhancing oil are all extremely significant (P < 0.01); in the quadratic term, A... 2 B 2 C 2 The quadratic term had an extremely significant impact on the overall sensory score of the tung oil (P<0.001).

[0093] 2.2.3 Results of Response Surface Optimization Experiment

[0094] Three-dimensional response surfaces, as an intuitive and effective analytical tool, can visually demonstrate the impact of interactions between various factors on the response value. A steeper slope indicates a more significant influence of that factor on the score, and vice versa. For example... Figure 5 It can be seen that as the levels of each factor increase, all response surfaces open downwards, and the fitted curves are all convex. The comprehensive sensory score response values ​​of the feed-to-oil ratio, reaction temperature, and reaction time all show a trend of first increasing and then decreasing, indicating that each factor has a maximum value. Figure 5 It can be seen that the response surface slopes for reaction temperature and material-to-oil ratio are steep, indicating that the interaction between B and C has a significant impact on the overall sensory score of the *Vernicia fordii* aroma-enhancing oil. The response surface for material-to-oil ratio is steeper than that for reaction time, indicating that the material-to-oil ratio has a greater impact on the sensory score of the *Vernicia fordii* aroma-enhancing oil in the AC interaction. The response surface for reaction temperature is steeper than that for reaction time, indicating that the reaction temperature has a greater impact on the sensory score in the AB interaction; these results are consistent with the analysis results in Table 4.

[0095] 2.2.4 Optimal Process Validation Test

[0096] Based on the regression model, the optimal process parameters for enhancing the aroma of *Vernicia fordii* seed oil were determined to be: a material-to-oil ratio of 1:11.6, a reaction temperature of 121.25℃, and a reaction time of 36.5 min. Under these conditions, the theoretical comprehensive sensory score was predicted to be 9.37 points. Considering the operability in actual production, the parameters were fine-tuned: a material-to-oil ratio of 1:12, a reaction temperature of 121℃, and a reaction time of 37 min. The verification experiment was repeated three times, and the comprehensive sensory score of the *Vernicia fordii* seed oil was obtained as 9.16 ± 0.58 points. The relative error between the theoretical and actual values ​​was 2.29%, indicating that the optimized parameters of the model are reliable.

[0097] 2.3 Analysis of volatile components in refined oil and flavoring oil from *Vernicia fordii* seeds

[0098] 2.3.1 Comparative Analysis of GC-IMS Spectra of Refined Oil and Flavoring Oil from *Vernicia fordii*

[0099] Two-dimensional spectra of refined tung oil and flavoring oil from tung oil are shown below. Figure 6 As shown in (a), the entire graph has a blue background. The red vertical line at the horizontal axis (1.0) represents the RIP peak (reacting ion peak, normalized). The vertical axis represents the retention time (s) in gas chromatography, and the horizontal axis represents the relative migration time (normalized). Each point on either side of the RIP peak represents a volatile organic compound. The color represents the peak intensity, ranging from blue to red, with darker colors indicating greater peak intensity. Figure 6 (a) It can be seen that there are certain differences in the concentration of volatile substances between the aroma-enhanced oil and the refined oil of *Vernicia fordii*, mainly concentrated in two regions, a and b. The concentration of substances in region b of the aroma-enhanced oil of *Vernicia fordii* is significantly higher than that of the refined oil, indicating that the aroma-enhancing process changes the volatile aroma components of *Vernicia fordii* oil, and the substances in this region are the main flavor products generated after aroma enhancement.

[0100] To further observe the differences in volatile components between the aroma-enhancing oil and refined oil of *Vernicia fordii*, the spectrum of the refined oil sample was selected as a reference. The spectrum of the aroma-enhancing oil was subtracted from the reference sample to obtain a comparison chart, as shown below. Figure 6 As shown in (b). If the relative content of volatile organic compounds in the target sample and the reference sample is the same, the background after subtraction is white. Red indicates that the concentration of substances in the target sample is higher than that in the reference sample, and blue indicates that the concentration of substances in the target sample is lower than that in the reference sample. It can be seen from the figure that the higher concentration of substances in region a in the refined oil indicates that the concentration of these substances is significantly reduced after the aroma enhancement process with *Vernicia fordii* oil. This may mean that these substances underwent transformation during the aroma enhancement process, generating new flavor compounds or decomposing due to thermal instability. The higher concentration of substances in region b in the aroma-enhanced *Vernicia fordii* oil indicates that these volatile flavor substances may be generated during the aroma enhancement process. Therefore, it is evident that the aroma enhancement process of *Vernicia fordii* oil alters the volatile aroma components of the refined *Vernicia fordii* oil.

[0101] Further, the Gallery Plot plugin was used to generate fingerprint spectra for a direct comparison of the differences in volatile substance content between the two samples. For example... Figure 7As shown, there are significant differences in the volatile substances in refined and flavored *Vernicia fordii* oil. The substances in region a are present in higher concentrations in refined *Vernicia fordii* oil. These substances mainly include aldehydes (such as butyraldehyde and 2-propenal), alcohols (such as 2-octanol and 1-penten-3-ol), and ketones (such as 2-pentylfuran and 3-pentanone). At low concentrations, these substances contribute a fresh fruity and herbal aroma to the oil, but at high concentrations, they may produce unpleasant odors. The substances in region b are present in higher concentrations in flavored *Vernicia fordii* oil. These mainly include acids (such as 2-methylpropionic acid, propionic acid, and acetic acid) and sulfur-containing compounds (such as methylthiopropionaldehyde and 2-ethylthiazole). These compounds are typically generated in the Maillard reaction and provide the flavored oil with rich nutty, fatty, and fruity aromas. Therefore, the flavoring process significantly alters the volatile components of *Vernicia fordii* oil, enhancing its flavor characteristics.

[0102] 2.3.2 Qualitative and quantitative analysis by GC-IMS

[0103] The types and content changes of volatile substances are important indicators for distinguishing between refined tung oil and flavoring oil from *Vernicia fordii*. Using GC-IMS technology, we performed qualitative and quantitative analysis of the volatile components in the two oils. Using retention index (RI), retention time (Rt), and ion migration time (Dt) as identification criteria, a total of 84 volatile substances (including monomers (M) and dimers (D)) were identified. These mainly included 32 aldehydes, 17 alcohols, 4 acids, 17 ketones, and 4 esters; 10 other categories were also identified. Figure 7 As shown in Table 5, the refined oil of *Vernicia fordii* contains high levels of aldehydes, alcohols, and ketones, a result consistent with Wang Jinhua's findings. After flavoring, the oil from *Vernicia fordii* showed decreased levels of aldehydes, alcohols, and ketones, but increased levels of acids, esters, other compounds, and total volatile substances.

[0104] Aldehydes, primarily derived from lipid oxidation, are characterized by high volatility and low odor thresholds. At low concentrations, they exhibit oily, grassy, ​​and floral / fruity aromas, but at high concentrations, they possess rancid, pungent, and nauseating odors. Table 5 shows that during the flavoring process of *Vernicia fordii* oil, the concentrations of most volatile aldehydes decreased, while the contents of volatile substances such as 3-methylbutyraldehyde, acetal, and salicylaldehyde increased. 3-Methylbutyraldehyde, with its almond, apple, and malt aromas, is generated at high temperatures via the Strecker degradation pathway, indicating that the reduction in aldehyde concentration plays a role in the flavor formation of *Vernicia fordii* oil. Alcohols and ketones are generally considered to originate from the oxidation of unsaturated fatty acids and amino acid degradation, and their odor thresholds are higher than those of aldehydes. In the flavored *Vernicia fordii* oil, the concentrations of alcohols and ketones decreased significantly (P < 0.05), while the content of acetone, which has spicy and sweet flavors, increased.

[0105] Ester compounds mainly originate from lipid oxidation or esterification reactions. Their content in refined and flavored *Vernicia fordii* oil is relatively low, and the changes in flavor before and after flavoring are not significant (P > 0.05). Acids and other substances have a significant impact on the formation of flavor in oils. High concentrations of acids produce pungent sour and putrid odors, while lower concentrations produce pleasant flavors. Acetic acid (acetic acid taste), propionic acid (sour taste), and 2-methylpropionic acid (nutty, creamy, buttery, and fruity flavors) are present in increased concentrations in *Vernicia fordii* flavored oil. Furthermore, the concentrations of 2-acetylthiazole and thiophene are also increased in *Vernicia fordii* flavored oil. 2-acetylthiazole is formed from reducing sugars and substances such as L-cysteine ​​through the Maillard reaction under heating conditions, exhibiting distinct nutty, popcorn, and meaty aromas.

[0106] In summary, during the flavoring process of *Vernicia fordii* oil, aldehydes, alcohols, and ketones may undergo Strecker degradation, Maillard reaction, and fatty acid oxidation degradation to generate flavor compounds such as 3-methylbutyraldehyde, acetal, salicylaldehyde, acetone, 2-methylpropionic acid, 3-methylbutyraldehyde, thiophene, and 2-ethylthiazole. These reactions not only reduce the concentration of aldehydes, alcohols, and ketones but also increase the content of new volatile substances, thus endowing the flavored oil with a richer and more complex flavor. Therefore, the flavored *Vernicia fordii* oil outperforms the unflavored refined *Vernicia fordii* oil in terms of flavor.

[0107] Table 5. Volatile composition of the refined oil and the aroma-enhanced oil of Idesia polycarpa Maxim.

[0108]

[0109]

[0110]

[0111] Note: In the table, "M" represents the monomer of the substance and "D" represents the dimer of the substance.

[0112] 2.3.3 OAV values ​​of volatile components in tung oil and refined oil from *Vernicia fordii*

[0113] Odor Activity (OAV) is an important indicator for evaluating the contribution of volatile substances to the overall aroma. An OAV value > 1 indicates that the substance makes a significant contribution to the overall aroma of the sample. The OAV values ​​are calculated as shown in Table 6. A total of 35 key flavor compounds (including monomers and dimers) with OAV values ​​> 1 were screened. Among them, the increased concentrations of volatile substances such as 2-methylpropionic acid (nutty, creamy, buttery, and fruity aromas), butyraldehyde (fatty and fresh aromas), 3-methylbutyraldehyde (almond, apple, and malt aromas), 2-methylpropionaldehyde (malt aroma), phenylacetaldehyde (floral aroma), thiophene (special aroma), and 2-acetylthiazole (nutty, popcorn, and meaty aromas) in the tung oil endowed the tung oil with a rich nutty, fatty, and fruity aroma. The concentrations of volatile compounds such as 1-octen-3-ol (grassy, ​​mushroom flavor), 1-octen-3-one (mushroom, rubber flavor), 1-penten-3-one (mushroom, rubber flavor), and diacetyl (creamy flavor) decreased in the aroma-enhancing oil of *Vernicia fordii*, thus reducing unpleasant odors such as earthiness, mushroom, and irritation. These compounds may have participated as intermediates in the advanced stages of the Maillard reaction, generating flavor products such as thiophenes and thiazoles. Further enhancement of its flavor quality, combined with sensory analysis, revealed (e.g.) Figure 9 As shown in the figure, the aroma-enhancing oil from *Vernicia fordii* seeds outperformed the refined oil in terms of roasting aroma, caramel aroma, and overall sensory evaluation, but the difference in *Vernicia fordii* flavor was not significant. This result is consistent with the OAV analysis results, indicating that aroma compounds such as 2-acetylthiazole, 2-methylpropionaldehyde, and 2-methylpropionic acid enhance the roasting and caramel aromas in the aroma-enhancing oil, significantly improving its overall flavor. In summary, the increase in aroma compounds such as 2-acetylthiazole and 2-methylpropionic acid, and the decrease in unpleasant odor compounds such as 1-octen-3-ol and 1-octen-3-one, work together to enhance the flavor of *Vernicia fordii* seed oil, resulting in its superior performance in roasting aroma, caramel aroma, and overall sensory evaluation. This provides a scientific basis for optimizing the aroma-enhancing process of *Vernicia fordii* seed oil and helps to further enhance its market competitiveness.

[0114] Table 6. OAV value analysis table of refined oil and aroma-enhanced oil of Idesia polycarpa Maxim.

[0115]

[0116]

[0117] 2.4 Sensory Evaluation Analysis of Aralia elata Flavoring Oil and Refined Oil

[0118] Combined with sensory analysis, it was found that (e.g.) Figure 9As shown in the figure, the aroma-enhancing oil from *Vernicia fordii* seeds outperformed the refined oil in terms of roasting aroma, caramel aroma, and overall sensory evaluation, but the difference in *Vernicia fordii* flavor was not significant. This result is consistent with the OAV analysis results, indicating that aroma compounds such as 2-acetylthiazole, 2-methylpropionaldehyde, and 2-methylpropionic acid enhance the roasting and caramel aromas in the aroma-enhancing oil, significantly improving its overall flavor. In summary, the increase in aroma compounds such as 2-acetylthiazole and 2-methylpropionic acid, and the decrease in unpleasant odor compounds such as 1-octen-3-ol and 1-octen-3-one, work together to enhance the flavor of *Vernicia fordii* seed oil, resulting in its superior performance in roasting aroma, caramel aroma, and overall sensory evaluation. This provides a scientific basis for optimizing the aroma-enhancing process of *Vernicia fordii* seed oil and helps to further enhance its market competitiveness.

[0119] 2.5 Analysis of Fatty Acid Composition Quality Indicators of Tung Seed Refined Oil and Flavoring Oil

[0120] Table 7 Fatty acid composition and quality indicators of refined oil and aroma-enhanced oil from Idesia polycarpa Maxim.

[0121]

[0122]

[0123] Note: ** indicates significant differences between samples (p<0.05)

[0124] This study conducted a detailed analysis of the physicochemical properties and fatty acid composition of the flavored and refined *Vernicia fordii* oils to assess the impact of the flavoring process on the quality of *Vernicia fordii* oils. The results showed that the fatty acid compositions of the two types of *Vernicia fordii* oils were similar, mainly containing palmitic acid, oleic acid, linoleic acid, linolenic acid, palmitoleic acid, stearic acid, and erucic acid. Linoleic acid had the highest content, accounting for approximately 65% ​​of the fatty acid composition, making it the most abundant unsaturated fatty acid in *Vernicia fordii* oil. No significant differences were found in the fatty acid composition and relative content between the flavored and refined oils (P > 0.05), indicating that the flavoring process did not alter the fatty acid structure of the oils. Further analysis of the physicochemical properties of the two types of *Vernicia fordii* oils revealed no significant differences between the flavored and refined oils in acid value, peroxide value, color, and saponification value (P > 0.05), indicating that the flavoring process did not negatively affect the basic physicochemical properties of the oils. However, the moisture content of the flavored oil was significantly higher than that of the refined oil (P < 0.05), which may be related to the addition of enzymatic hydrolysate during the heating reaction. Nevertheless, the moisture content of the flavored oil still meets the national standard (moisture content ≤ 0.10%). This demonstrates that optimizing the flavoring process of refined *Vernicia fordii* oil through the Maillard reaction preserves the original quality of the *Vernicia fordii* oil. Combined with volatile matter analysis, the flavored oil showed no significant difference from the refined oil in fatty acid composition and physicochemical properties. While ensuring the inherent quality of the *Vernicia fordii* oil, it also generated a large number of Maillard reaction flavor products, endowing the oil with new flavor characteristics. This process not only effectively reduced unpleasant odor substances in the *Vernicia fordii* oil but also improved the problem of insufficient aroma.

[0125] 3. Conclusion

[0126] This study used the enzymatic hydrolysate of *Vernicia fordii* meal as the aroma source to enhance the aroma of refined *Vernicia fordii* oil. Response surface methodology was used to determine the optimal parameters for the aroma enhancement process: a feed-to-oil ratio of 1:12, a reaction temperature of 121℃, and a heating reaction time of 37 minutes. Under these conditions, the overall sensory score of the enhanced *Vernicia fordii* oil was 9.16. A total of 84 volatile compounds were identified using GC-IMS technology. The enhanced *Vernicia fordii* oil showed an increase in the content of acids, esters, and other compounds, while the content of aldehydes, alcohols, and ketones decreased. Based on OAV values, 35 key flavor compounds were screened. Among them, the concentrations of volatile compounds such as 2-methylpropionic acid, butyraldehyde, 3-methylbutyraldehyde, 2-methylpropionaldehyde, phenylacetaldehyde, and 2-acetylthiazole increased in the enhanced *Vernicia fordii* oil, contributing rich fruity, fatty, and meaty flavor characteristics. The concentration of volatile substances such as 1-octen-3-ol, 1-octen-3-one, 1-penten-3-one, and diacetyl in the flavored *Vernicia fordii* oil decreased, thus reducing unpleasant odors such as earthiness, mushroominess, and irritation. Further sensory analysis of the flavored *Vernicia fordii* oil revealed that it outperformed unflavored refined *Vernicia fordii* oil in terms of roasting aroma, caramel aroma, and overall score. There were no significant differences between the flavored and refined oils in terms of fatty acid composition, acid value, peroxide value, color, and saponification value, indicating that the flavoring process did not negatively impact the basic quality of the *Vernicia fordii* oil. These findings provide a scientific basis for flavor improvement and product diversification of *Vernicia fordii* oil, and also open up new avenues for the efficient utilization of *Vernicia fordii* meal byproducts. In the future, our team will further investigate the effects of potential variables such as enzymatic hydrolysis time and temperature on the aroma generation of *Vernicia fordii* oil, the aroma stability and persistence of the flavored *Vernicia fordii* oil in practical applications, and the quality changes under different storage conditions, in order to further evaluate its application potential in the food industry and provide better guidance for the industrial production process of flavored *Vernicia fordii* oil.

[0127] Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the technical solution of the present invention is not limited to the above embodiments, and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the content disclosed in this invention should be considered within the scope of protection of this invention.

Claims

1. A process for enhancing the aroma of tung oil, characterized in that, The enzymatic hydrolysate of tung oil meal was mixed with tung oil and heated to react. After the reaction was completed, the mixture was cooled to 40℃~50℃, filtered to remove impurities, and tung oil flavored was obtained.

2. The aroma-enhancing process for tung oil according to claim 1, characterized in that, The mixing ratio of the enzymatic hydrolysate of *Vernicia fordii* meal to the refined oil of *Vernicia fordii* is (1:9) to (1:12) by volume.

3. The aroma-enhancing process for tung oil according to claim 1, characterized in that, The heating reaction temperature is 115-130℃.

4. The aroma-enhancing process for tung oil according to claim 1, characterized in that, The heating reaction time is 30-50 minutes.

5. The aroma-enhancing process for tung oil according to claim 1, characterized in that, The heating reaction involves placing the raw materials in a constant-temperature magnetic stirrer, setting an oil bath to heat to a preset reaction temperature, and maintaining a constant reaction time for the heating reaction.

6. The aroma-enhancing process for tung oil according to claim 1, characterized in that, The enzymatic hydrolysate of *Vernicia fordii* meal is the enzymatic hydrolysate obtained by enzymatic hydrolysis of *Vernicia fordii* meal by alkaline protease and flavor protease, respectively.

7. The aroma-enhancing process for tung oil according to claim 6, characterized in that, The enzymatic hydrolysate of *Vernicia fordii* seed meal is prepared by the following method: Crush and sieve the tung oil seed meal. Mix the tung oil seed meal with deionized water at a ratio of (1:6) to (1:10), adjust the pH to (8.5-9.5), and add 3500-4500 U / g of alkaline protease at 50-60℃ for enzymatic hydrolysis for 2-4 hours. After hydrolysis, heat the hydrolysate to 85-95℃ for 5-15 minutes to inactivate the enzyme. After the mixture cools, adjust the pH to 6-7, add 800-1200 U / g of flavor protease, and hydrolyze at 55-65℃ for 3-5 hours. After inactivating the enzyme again, centrifuge the mixture and separate the supernatant for later use.

8. The aroma-enhancing process for tung oil according to claim 7, characterized in that, The process involves mixing *Vernicia fordii* seed meal with deionized water at a ratio of 1:8, where the ratio is a mass ratio.

9. The aroma-enhancing process for tung oil according to claim 7, characterized in that, The centrifugation is specifically performed at 4000 r / min for 15 min.

10. A fragrance-enhancing oil made from tung seeds, characterized in that, It is prepared by the aroma-enhancing process of tung oil as described in any one of claims 1-9.

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