Black tea aroma substance detection method

Abstract

The invention relates to the field of tea evaluation, in particular to a black tea aroma substance detection method. The method comprises the following steps: extracting tea aroma components by adopting headspace solid-phase extraction: adding tea into a solid-phase micro-extraction headspace bottle, then adding sodium chloride, distilled water and ethyl decanoate, then putting the solid-phase micro-extraction headspace bottle on a constant-temperature magnetic hot plate stirrer, heating, stabilizing, inserting SPME fibers into the solid-phase micro-extraction headspace bottle, and carrying out headspace solid-phase extraction; performing aroma adsorption; and analyzing the aroma by adopting a gas chromatograph and a mass spectrometer, wherein the reaction condition of the gas chromatograph is as follows: an Rtx-5MS chromatographic column is adopted.

Description

Technical Field

[0001] The present invention relates to the field of tea evaluation, and specifically provides a method for detecting aroma substances in black tea. Background Art

[0002] The aroma of tea is closely related to its origin, craftsmanship, and variety. Its aroma is the result of the combined effects of the content and types of volatile aroma compounds within the tea. The aroma of black tea is determined both by the characteristics of the fresh leaves and by processing techniques such as withering and fermentation. Drying is also a crucial step in the development of black tea's aroma.

[0003] Black tea aroma testing is primarily divided into non-volatile and volatile component testing. Testing for non-volatile components is relatively mature. For example, moisture content is determined by referring to GB5009.3-2016, "National Food Safety Standard for the Determination of Moisture in Foods." Water extracts are determined using the GB / T8305-2013 method; tea polyphenols are determined using the folin-phenol method (GB / T8313-2018); total free amino acid content is determined using the ninhydrin colorimetric method (GB / T8314-2013); and soluble sugars are determined using the anthrone colorimetric method. Theaflavins, thearubigins, and theabrownins are determined using a systems analysis method.

[0004] However, there is little research on the detection methods of volatile substances. Summary of the Invention

[0005] The present invention hopes to provide a method for detecting black tea aroma substances, and the specific scheme is as follows: A method for detecting black tea aroma substances comprises the following steps: (1) Extracting tea aroma components by headspace solid phase extraction: Add tea leaves into the solid phase microextraction headspace bottle, then add sodium chloride, distilled water and ethyl decanoate, then place the solid phase microextraction headspace bottle on a constant temperature magnetic hot plate stirrer to heat it. After stabilization, insert the SPME fiber into the solid phase microextraction headspace bottle for aroma adsorption; (2) Aroma analysis using a gas chromatograph and mass spectrometer: The reaction conditions of the gas chromatograph are as follows: an Rtx-5MS column is used, and the column temperature is as follows: the initial column temperature is 40°C, without holding, the temperature is increased at 1.5°C / min to 70°C, without holding, the temperature is increased at 1°C / min to 72°C, held for 2 minutes, the temperature is increased at 1.5°C / min to 90°C, held for 1 minute, the temperature is increased at 5°C / min to 170°C, held for 1 minute, and finally the temperature is increased at 9°C / min to 230°C, held for 2 minutes. This column and temperature program are specifically designed for black tea.

[0006] In step (1), 1 g of tea sample was weighed and added into a 20 mL solid phase microextraction headspace bottle.

[0007] In the step (1), the amount of sodium chloride added is 1 g, the amount of distilled water is 5 ml, the mass fraction of ethyl caproate is 50 ug / ml, and the amount added is 5 ul.

[0008] The temperature of the distilled water added in step (1) is 60°C, and the heating temperature of the magnetic hot plate stirrer is 60°C.

[0009] The heating stabilization time in step (1) is 6 minutes.

[0010] The column flow rate of the chromatographic column in step (2) is 1.0 mL / min.

[0011] The reaction conditions of the mass spectrometer in step (2) are as follows: EI source 70 eV; ion source temperature 230°C, interface temperature 240°C; mass scanning range mass-to-charge ratio (m / z) 40∼400, solvent delay time 2 min.

[0012] The present invention provides a method for detecting volatile substances in black tea, which, when combined with a method for detecting non-volatile substances in accordance with national standards, can obtain information on the relevant aroma components of the tea. DETAILED DESCRIPTION

[0013] 1. Non-volatile substance detection method Moisture: Referring to GB5009.3-2016 “National Food Safety Standard for the Determination of Moisture in Food”, this experiment adopted the direct drying method. The water extract was determined using the GB / T8305-2013 method; tea polyphenols were determined using the folin phenol method (GB / T8313-2018); the total free amino acid content was determined using the ninhydrin colorimetric method (GB / T8314-2013); soluble sugars: anthrone colorimetric method

[63] . Theaflavins, thearubigins, and theabrownins were determined using the system analysis method. The catechin components, caffeine, and flavonoid glycosides of black tea were determined using high performance liquid chromatography, where mobile phase A was 0.261% phosphoric acid and 5% acetonitrile aqueous solution, mobile phase B was 80% methanol solution, the flow rate was 1 ml / min, and the column temperature was 35°C.

[0014] 2. Volatile substance detection method Headspace solid-phase microextraction (HS-SPME) was used to extract tea aroma components. One gram of tea sample was accurately weighed and placed in a 20-mL HS-SPME headspace vial. 1 gram of sodium chloride was added, followed by 5 mL of 60°C distilled water and 5 μL of 50 μg / mL ethyl decanoate. The headspace vial was heated on a magnetic hot plate stirrer at 60°C. After stabilization for 6 minutes, an SPME fiber (50 / 30 μm DVB / CAR / PDMS, Supelco, Bellefonte, PA, USA) was inserted into the headspace vial and aroma adsorption was performed for 50 minutes. The fiber was then removed and analyzed by GC-MS.

[0015] The aroma components of the tea samples were analyzed by GC-MS. Specific analytical conditions were as follows: GC conditions: Rtx-5MS column (30 m × 0.25 mm × 0.25 μm); temperature program: initial column temperature at 40°C (no hold); temperature increased at 1.5°C / min to 70°C (no hold); temperature increased at 1°C / min to 72°C (hold for 2 min); temperature increased at 1.5°C / min to 90°C (hold for 1 min); temperature increased at 5°C / min to 170°C (hold for 1 min); and finally temperature increased at 9°C / min to 230°C (hold for 2 min); injection port at 250°C; split flow; carrier gas: He; column flow rate: 1.0 mL / min. MS conditions: EI source 70 eV; ion source temperature 230 °C, interface temperature 240 °C; mass scan range mass-to-charge ratio (m / z) 40-400, solvent delay time 2 min.

[0016] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for detecting black tea aroma substances, characterized in that: The steps include: Headspace solid phase extraction (SPE) was used to extract tea aroma components: tea leaves were added to a SPE headspace bottle, followed by sodium chloride, distilled water, and ethyl decanoate. The SPE headspace bottle was then heated on a constant temperature magnetic hot plate stirrer. After stabilization, the SPME fiber was inserted into the SPE headspace bottle for aroma adsorption. The aroma was analyzed by gas chromatograph and mass spectrometer: the reaction conditions of the gas chromatograph were as follows: an Rtx-5MS chromatographic column was used, and the temperature of the chromatographic column was as follows: the initial column temperature was 40°C, without maintaining, the temperature was increased to 70°C at 1.5°C / min, without maintaining, the temperature was increased to 72°C at 1°C / min, maintained for 2 minutes, the temperature was increased to 90°C at 1.5°C / min, maintained for 1 minute, the temperature was increased to 170°C at 5°C / min, maintained for 1 minute, and finally the temperature was increased to 230°C at 9°C / min, maintained for 2 minutes.

2. The method for detecting black tea aroma substances according to claim 1, wherein: In step (1), 1 g of tea sample was weighed and added into a 20 mL solid phase microextraction headspace bottle.

3. The method for detecting black tea aroma substances according to claim 2, wherein: In the step (1), the amount of sodium chloride added is 1 g, the amount of distilled water is 5 ml, the mass fraction of ethyl caproate is 50 ug / ml, and the amount added is 5 ul.

4. The method for detecting black tea aroma substances according to claim 1, wherein: The temperature of the distilled water added in step (1) is 60°C, and the heating temperature of the magnetic hot plate stirrer is 60°C.

5. The method for detecting black tea aroma substances according to claim 1, wherein: The heating stabilization time in step (1) is 6 minutes.

6. The method for detecting black tea aroma substances according to claim 1, wherein: The column flow rate of the chromatographic column in step (2) is 1.0 mL / min.

7. The method for detecting black tea aroma substances according to claim 1, wherein: The reaction conditions of the mass spectrometer in step (2) are as follows: EI source 70 eV; ion source temperature 230°C, interface temperature 240°C; mass scanning range mass-to-charge ratio (m / z) 40∼400, solvent delay time 2 min.