Method for Rapid Prediction of Flavor Potential of Oak Barrels Based on Short-Term Water Immersion Method

Abstract

The present invention provides a method for rapidly predicting the flavor potential of oak barrels based on the short-term water immersion method, belonging to the technical field of beer detection. This method establishes the functional correlation between the alcohol concentration of the oak barrel extract and the content of flavor substances in the oak barrel, so as to rapidly predict the intensity of flavor substances in the oak barrel, as well as the emptying time and reuse time of the oak barrel based on the alcohol concentration of the oak barrel extract. This method can rapidly evaluate the residual flavor level in the secondary oak barrel, enabling winemakers to quickly select oak barrels with more residual flavor during the barrel selection process for aging alcoholic beverages, providing a richer aroma resource for the subsequent aging process, and providing a rapid response for their finished products to have a richer flavor experience and product characteristics.

Description

Technical Field

[0001] The present invention belongs to the technical field of beer detection, and particularly relates to a method for rapidly predicting the flavor potential of oak barrels based on a short-term water immersion method. Background Art

[0002] The aging technology is an ancient traditional process and is still used to improve the sensory quality of wines, spirits and some specialty beers. At present, with the gradual development of China's economy and the continuous improvement of people's living standards, the consumer group of ultra-high-end beers is gradually expanding. Different intellectual levels, consumption capabilities and living environments result in different consumption demands for beers, while the innovation speed of high-quality products fails to meet expectations.

[0003] Oak barrels are the main providers of oak flavors in barrel-aged alcoholic beverages. Its main components are cellulose, hemicellulose, lignin and tannins, which occupy most of the oak. Lignin is a macromolecular substance, which is composed of various aromatic groups (syringyl propane, guaiacyl propane, p-hydroxyl propane) combined with carbohydrates by ester bonds, hemiacetals or acetals. The tannins in oak are macromolecular non-flavonoid hydrolyzable tannins, such as ellagitannins. The alcohol extracts of oak are mainly volatile compounds. During the process of soaking oak, through the slow action of alcohol, acid in water and oxygen in the air, macromolecular substances such as lignin, tannins and hemicellulose in oak decompose and oxidize to generate various flavor components, thus constituting the oak aroma.

[0004] After alcoholic beverages are aged in oak barrels, the body flavor changes greatly, and coconut juice, milk fragrance, woody and vanilla flavors are significantly increased. Among them, oak flavors represented by oak lactones, furan compounds and phenolic aldehyde compounds can bring more than 60% of the flavor to the finished product. However, newly processed barrels will bring a strong impact on the body flavor, making it lose balance and being unfavorable to the improvement of the finished product quality. Therefore, more than 90% of traditional Scotch whiskies are aged in secondary oak barrels used by American bourbon whiskies. The barrel-aging process of barrel-aged beers follows the practice of Scotch whiskies and uses a large number of bourbon barrels. Since the bourbon barrels purchased come from different bourbon whisky manufacturers and barrels of different periods, the liquor residues in the barrels vary greatly. This change in difference will bring the flavor characteristics of bourbon whisky to barrel-aged beers, thus directly affecting the quality of its final products. There are hundreds of flavor substances in the residues of oak barrels. If all of them are detected, it is time-consuming, laborious and has a long cycle. Therefore, how to rapidly monitor the flavor residue level in secondary oak barrels including bourbon barrels to ensure the quality of its barrel-aged beer products urgently needs to be solved by technical personnel in this field. Summary of the Invention

[0005] The present invention provides a method for rapidly predicting the flavor potential of oak barrels based on the short-term water immersion method. This method can quickly evaluate the residual flavor level in secondary oak barrels, enabling winemakers to quickly select oak barrels with more flavor residues during the barrel selection process for aging alcoholic beverages, providing a richer aroma resource for the subsequent aging process, and providing a quick response for their finished products to have a richer flavor experience and product characteristics.

[0006] To achieve the above object, the present invention provides a method for rapidly predicting the flavor potential of oak barrels based on the short-term water immersion method, establishing a functional correlation between the alcohol concentration of the oak barrel extract and the content of flavor substances in the oak barrel, so as to rapidly predict the intensity of flavor substances in the oak barrel and the emptying time of the oak barrel based on the residual ethanol content obtained from the oak barrel extract.

[0007] Preferably, the flavor substances are n-propanol, ethyl acetate, isobutanol, and oak lactone.

[0008] Preferably, establishing the functional correlation between the alcohol concentration of the oak barrel extract and the content of flavor substances in the oak barrel is specifically as follows:

[0009] The functional relationship between alcohol concentration and n-propanol content: Y = 0.8562x - 0.0646, R 2 = 0.7271;

[0010] The functional relationship between alcohol concentration and ethyl acetate content: Y = 0.1829x - 0.1076, R 2 = 0.766;

[0011] The functional relationship between alcohol concentration and isopropanol content: Y = 0.1384x - 0.2512, R 2 = 0.8295;

[0012] The functional relationship between alcohol concentration and oak lactone content: Y = 0.0458x - 0.2512, R 2 = 0.6654.

[0013] Preferably, the alcohol concentration of the oak barrel extract and the content of flavor substances in the oak barrel have a high correlation, and the correlation > 65%.

[0014] Preferably, rapidly predicting the intensity of flavor substances in the oak barrel and the emptying time of the oak barrel based on the residual ethanol content obtained from the oak barrel extract is specifically as follows:

[0015] 0.8 ≤ the residual ethanol content of the oak barrel ≤ 1% v / v, and the emptying time is 0 - 1 month;

[0016] 0.6 ≤ the residual ethanol content of the oak barrel < 0.8% v / v, and the emptying time is 1 - 3 months;

[0017] 0.1 ≤ Residual ethanol content in the oak barrel < 0.6% v / v, left empty for 3 - 6 months;

[0018] Residual ethanol content in the oak barrel < 0.1% v / v, left empty for 6 - 12 months or more.

[0019] Preferably, the oak barrel extract is obtained by the following method:

[0020] Fill a standard bourbon barrel with deionized water and let it stand for 48 hours to obtain the oak barrel extract.

[0021] Preferably, before analyzing the alcohol concentration of the oak barrel extract, it further includes the step of filtering the oak residues in the extract with a single - layer medium - speed dry filter paper.

[0022] Preferably, the extract is filtered at an ambient temperature of 20 ± 5°C and a relative humidity of 80%.

[0023] Preferably, when analyzing the alcohol concentration of the oak barrel extract, the filtered extract is tested for alcohol concentration; otherwise, it is stored at 20 ± 0.1°C and the test is completed within 1 hour.

[0024] Preferably, the content of oak barrel flavor substances is analyzed by headspace treatment combined with gas chromatography. Qualitative analysis is carried out by the retention time of relevant flavor substance standards, and quantitative analysis is carried out by establishing a calibration curve with different concentrations of standard substances.

[0025] Preferably, the headspace treatment specifically includes:

[0026] Take 5 mL of the sample and put it into a 20 mL headspace vial, and place it on the sample tray of the headspace sampler for analysis; among them, the headspace holding temperature is 60°C and the holding time is 40 min.

[0027] Preferably, the gas chromatography analysis specifically includes:

[0028] Use a weakly polar capillary column 60 m × 0.32 mm × 0.25 μm, the carrier gas is nitrogen, and the flow rate is 1.5 mL / min;

[0029] Column temperature programming: maintain at 35°C for 2 min, then increase to 200°C at a rate of 10°C / min and maintain for 3 min.

[0030] Compared with the prior art, the advantages and positive effects of the present invention are:

[0031] The present invention is based on the short-term water immersion method (i.e., filling a standard bourbon barrel with deionized water, standing still for 48 hours, and taking the immersion liquid). The alcohol content and flavor substances are measured using an alcohol analyzer and a gas chromatograph respectively. The results show that there is a certain correlation between the residual alcohol content and flavor residue in the secondary oak barrel. Based on this, the emptying time and reusing time of the oak barrel can be inferred from the alcohol content. This method can quickly evaluate the residual level of flavor substances in the secondary oak barrel, enabling winemakers to quickly select oak barrels with more flavor residues during the barrel selection process for aging alcoholic beverages. It not only provides necessary technical support for the subsequent barrel selection process but also can provide a richer aroma resource for the subsequent aging process, providing a quick response for its finished product to have a richer flavor experience and product characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a gas chromatogram of some flavor components in the water immersion liquid of the oak barrel provided by an embodiment of the present invention;

[0033] Figure 2 It is a function graph of the alcohol concentration and the content of flavor substances in the oak barrel extract provided by an embodiment of the present invention;

[0034] Figure 3 It is a schematic diagram for evaluating the flavor residue of the secondary oak barrel by measuring the ethanol content provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Embodiment 1

[0037] Oak samples: A total of 10 secondary bourbon barrels, namely JD1, JD2, JM1, JM2, JM3, JM4, HH1, HH2, HH3, and HH4, are selected respectively. They are filled with deionized water, standing still for 48 hours, and the extraction liquid is taken for subsequent alcohol concentration and flavor substance analysis.

[0038] Sample preparation: The oak residues in each extraction liquid are filtered with a single-layer medium-speed dry filter paper (the filtration environment temperature is 20 ± 5 °C, and the relative humidity is 80%).

[0039] Alcohol concentration analysis: The filtered samples should be immediately tested using an ANTON PARR alcohol analyzer. Otherwise, they need to be stored at 20 ± 0.1 °C and tested within 1 hour.

[0040] Headspace treatment: Take 5 mL of the sample and place it in a 20 mL headspace vial. Place it on the sample tray of the headspace sampler for analysis. Among them, the headspace incubation temperature is 60 °C, and the incubation time is 40 min.

[0041] Gas chromatography analysis: Use a weak polar capillary column 60 m × 0.32 mm × 0.25 μm. The carrier gas is nitrogen, and the flow rate is 1.5 mL / min. The column temperature program is: hold at 35 °C for 2 min, then increase to 200 °C at a rate of 10 °C / min and hold for 3 min.

[0042] Qualitative analysis: Use the retention time of relevant flavor substance standards for qualitative analysis.

[0043] Quantitative analysis: Establish a calibration curve using standard substances with different concentrations for quantitative analysis.

[0044] As Figure 1 and 2 shown, the main flavor substances in each bourbon barrel extract are n-propanol, ethyl acetate, isobutanol, and oak lactone. Summarize the analysis results of the flavor substances in each extract, and the following functional relationships between the alcohol concentration (v / v%) and the content of oak barrel flavor substances can be obtained:

[0045] Functional relationship between alcohol concentration and n-propanol content: Y = 0.8562x - 0.0646, R 2 = 0.7271;

[0046] Functional relationship between alcohol concentration and ethyl acetate content: Y = 0.1829x - 0.1076, R 2 = 0.766;

[0047] Functional relationship between alcohol concentration and isopropanol content: Y = 0.1384x - 0.2512, R 2 = 0.8295;

[0048] Functional relationship between alcohol concentration and oak lactone content: Y = 0.0458x - 0.2512, R 2 = 0.6654.

[0049] As can be seen from the above, there is a high correlation (R 2 > 65%) between the alcohol concentration and the content of some flavor substances in the 10 secondary oak barrel water extracts involved in Example 1. It can be proved thereby that the amount of alcohol content can indicate the intensity of the residual flavor substances in the oak barrel extract.

[0050] Verification experiment of Example 2

[0051] In this example, a reproducibility experiment was conducted on the above method, that is, the same sample (JM3) was tested six times under the same conditions. The testing method was the same as that shown in Example 1. As can be seen from the data in Table 1, the detection results show that the relative standard deviation is less than 10%. Therefore, it can be determined that the detection method provided by the present invention is stable and reliable.

[0052] Table 1 Reproducibility of Ethanol and Flavor Substance Detection

[0053] JM3 1# 2# 3# 4# 5# 6# Mean Relative standard deviation Ethanol %(v / v) 0.74 0.75 0.68 0.71 0.71 0.69 0.71 3.83％ n-Propanol (mg / L) 0.79 0.71 0.76 0.83 0.81 0.81 0.79 5.57％ Ethyl acetate (mg / L) 7.36 7.72 7.52 8.3 7.73 7.77 7.73 4.12％ Isobutanol (mg / L) 5.91 5.33 4.79 5.42 5.22 4.64 5.22 8.78％ Oak lactone (μg / L) 16.67 16.78 17.3 16.07 16.57 16.47 16.64 2.43％

[0054] Example 3 Sensory Evaluation Test

[0055] A six-person related sensory evaluation group was organized to conduct sensory evaluation tests on the above samples. The test scores ranged from 1 to 10, with 1 being the worst and 10 being the best. The test results are shown in Table 2.

[0056] Table 2 Ethanol and Flavor Substance Contents and Sensory Evaluation Scores in Oak Barrels and Aqueous Extracts

[0057]

[0058]

[0059] Combined with Figure 3 and the data in Table 2, it can be seen that the ethanol content in the extract is inversely proportional to the emptying time of the oak barrel: the relevant equation is Y = -9.8121x + 9.6898, R 2 = 0.7267; it is directly proportional to the sensory evaluation: the relevant equation is Y = 6.7949x + 2.1986, R 2 = 0.723. The results of the sensory evaluation scores combined with the gas chromatography detection show that the method provided by the present invention is effective for evaluating the flavor residues in the secondary oak barrels. As can be seen from the above, for the secondary oak barrels, when 0.8 ≤ the residual ethanol content in the oak barrel ≤ 1% v / v, it corresponds to an oak barrel emptied for 1 month. Theoretically, it is deduced that the intensity of the residual flavor substances is high, which corresponds to the results of the sensory evaluation test; when 0.6 ≤ the residual ethanol content in the oak barrel < 0.8% v / v, it corresponds to an oak barrel emptied for 3 months. Theoretically, it is deduced that the intensity of the residual flavor substances is relatively high, which corresponds to the results of the sensory evaluation test; when 0.1 ≤ the residual ethanol content in the oak barrel < 0.6% v / v, it corresponds to an oak barrel emptied for 6 months. Theoretically, it is deduced that the intensity of the residual flavor substances is low, which corresponds to the results of the sensory evaluation test; when the residual ethanol content in the oak barrel < 0.1% v / v, it corresponds to an oak barrel emptied for 12 months or more. Theoretically, it is deduced that the intensity of the residual flavor substances is low, which corresponds to the results of the sensory evaluation test. Thus, it is feasible to use the amount of residual ethanol in the secondary oak barrels to indicate the intensity of the residual flavor substances in the oak barrel extracts.

Claims

1. Method for rapidly predicting the flavor potential of oak barrels based on the short-term water immersion method, characterized in that, establish the functional correlation between the alcohol concentration of the oak barrel extract and the content of flavor substances in the oak barrel, so as to rapidly predict the intensity of flavor substances in the oak barrel and the emptying time of the oak barrel based on the residual ethanol content obtained from the oak barrel extract; the flavor substances are n-propanol, ethyl acetate, isobutanol and oak lactone; the oak barrel extract is obtained by the following method: Fill a standard bourbon barrel with deionized water and let it stand for 48 hours to obtain the oak barrel extract, which is subsequently used for alcohol concentration and flavor substance analysis.

2. The method according to claim 1, characterized in that, establishing the functional correlation between the alcohol concentration of the oak barrel extract and the content of flavor substances in the oak barrel specifically is: Functional relationship between alcohol concentration and n-propanol content: Y = 0.8562x - 0.0646, R 2 = 0.7271; Functional relationship between alcohol concentration and ethyl acetate content: Y = 0.1829x - 0.1076, R 2 = 0.766; Functional relationship between alcohol concentration and isopropanol content: Y = 0.1384x - 0.2512, R 2 = 0.8295; Functional relationship between alcohol concentration and oak lactone content: Y = 0.0458x - 0.2512, R 2 = 0.6654; In the above functional relationship, Y is the alcohol concentration.

3. The method according to any one of claims 1-2, characterized in that, the alcohol concentration of the oak barrel extract has a high correlation with the content of flavor substances in the oak barrel, and the correlation is > 65%.

4. The method according to claim 3, characterized in that, rapidly predicting the intensity of flavor substances in the oak barrel and the emptying time of the oak barrel based on the residual ethanol content obtained from the oak barrel extract specifically is: 0.8% v / v ≤ residual ethanol content obtained from the oak barrel extract ≤ 1% v / v, emptying time is 0-1 month; 0.6% v / v ≤ residual ethanol content obtained from the oak barrel extract < 0.8% v / v, emptying time is 1-3 months; 0.1% v / v ≤ residual ethanol content obtained from the oak barrel extract < 0.6% v / v, emptying time is 3-6 months; residual ethanol content obtained from the oak barrel extract < 0.1% v / v, emptying time is 6-12 months and above.

5. The method according to claim 1, characterized in that, before analyzing the alcohol concentration of the oak barrel extract, it further includes the step of filtering the oak residues in the extract with a single-layer medium-speed dry filter paper.

6. The method according to claim 5, characterized in that, filter the extract at an ambient temperature of 20 ± 5°C and a relative humidity of 80%; when analyzing the alcohol concentration of the oak barrel extract, perform an alcohol concentration test on the filtered extract, otherwise store it at 20 ± 0.1°C and complete the test within 1 hour.

7. The method according to claim 1, characterized in that, the content of flavor substances in the oak barrel is analyzed by headspace treatment combined with gas chromatography, qualitative analysis is carried out through the retention time of flavor substance standards, and quantitative analysis is carried out by establishing a calibration curve with different concentrations of standard substances.

8. The method according to claim 7, characterized in that, the headspace treatment specifically includes: Take 5 mL of the sample and put it into a 20 mL headspace vial, and place it on the sample tray of the headspace sampler for analysis; among them, the headspace incubation temperature: 60°C, incubation time: 40 min.

9. The method according to claim 7, characterized in that, the gas chromatography analysis specifically includes: A weak polar capillary column of 60 m×0.32 mm×0.25 μm was used, the carrier gas was nitrogen, and the flow rate was 1.5 mL / min; Column temperature programming: Hold at 35 °C for 2 min, then increase to 200 °C at a rate of 10 °C / min and hold for 3 min.

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