Abstract: At present, although there are a lot of reports on the analysis of aroma components of wine and other fruit wines by gas chromatography-mass spectrometry in China, the research on aroma components of sea buckthorn wine has not been reported.
Seabuckthorn fruit is rich in nutrition and has obvious health care effects. The total area of ​​seabuckthorn in China accounts for 95% of the total area of ​​seabuckthorn in the world, while the resources of seabuckthorn in Qinghai Province account for more than 20% of the national total. Qinghai seabuckthorn resources have the characteristics of wide distribution, variety, large area and good fruit quality.
The conversion of sea buckthorn juice through alcohol fermentation has the characteristics of large conversion amount, high product grade and high added value. Seabuckthorn wine has become the main channel for digesting and absorbing seabuckthorn juice resources in seabuckthorn producing areas such as Qinghai. Sea buckthorn wine with sea buckthorn fruit and sea buckthorn juice as raw materials not only has the characteristic of fruit wine with rich aroma, but also has certain health care functions, and is the main development direction of high-end health fruit wine production.
The aroma components of fruit wine not only determine the flavor characteristics and typical characteristics of fruit wine, but also an important indicator of fruit wine classification and origin labeling.
In the extraction and separation technology of aroma compounds, headspace solid phase microextraction technology is used by many researchers because of its safety, high efficiency and low cost.
The composition of fruit wine aroma is a complex system. Biostatistics and chemometrics methods provide an advantageous means for the study of the aroma quality of fruit wine. Factor analysis, principal component analysis, cluster analysis and other chemometric methods are widely used in the research of aroma quality of fruit wine.
Qinghai seabuckthorn dry wine is brewed from seabuckthorn juice produced in Qinghai. Seabuckthorn ice wine uses 100% Qinghai-Tibet Plateau seabuckthorn frozen fruit as raw material to extract concentrated juice. According to the production technology of grape ice wine, it is brewed at low temperature.
Due to the difference in raw materials and processes, there are obvious differences in the quality and taste of the two products. The taste and aroma quality of sea buckthorn ice wine is significantly better than that of dry wine, but there is no theoretical and experimental basis for this difference.
At present, although there are a lot of reports on the analysis of aroma components of wine and other fruit wines by gas chromatography-mass spectrometry in China, the research on aroma components of sea buckthorn wine has not been reported.
In this study, HS-SPME and GC-MS were used to detect the volatile compounds of sea buckthorn wine; the compound standard was used as a reference to discriminate and analyze the aroma compounds in sea buckthorn wine; The metrological method compares and analyzes the differences in the aroma components of the two products, and provides basic data for the research on the aroma characteristics, flavor formation mechanism and product quality improvement of sea buckthorn wine.
1 Materials and methods 1.1 Test materials and instruments 1.2 Test materials and standard compound test materials: 3 batches of sea buckthorn dry wine and ice wine products produced by Qinghai Tsinghua Bozhong Biotechnology Co., Ltd. were selected in 2008, and 3 bottles were randomly selected for each batch of products As a sample. The volume fraction of dry wine alcohol content is 12%, the sugar content is ≤10 g / L, and the total acid content is ≥8 g / L. The source of ice wine article Huaxia Wine reported that the volume fraction of alcohol content was 12%, sugar content ≥125 g / L, total acid content ≥10 g / L, and each sample was measured twice.
Analysis and testing 1.3 Instruments and conditions Manual SPME injector and 50 / 30μm DVB / CAR / PDMS extraction head, before use, the solid-phase micro-extraction head is aged at 250 ℃ in the inlet of the gas chromatograph for 1 hour, use TRACE DSQ GC-MS combined instrument and DB-WAX (30 m × 0.25 mm × 0.25 μm) elastic quartz capillary column.
1.4 Preparation of standard compounds Dissolve 10 μL of 22-octanol and various volumes of various standards into 100 mL of absolute ethanol to make standard compounds and internal standard stock solutions. Dissolve this stock solution in the simulated wine system. The concentration of the standard product in the simulated wine refers to the typical content of these compounds in the wine. The concentration of the internal standard substance in the simulated wine is 8.22 mg / L. The alcohol concentration in the simulated wine is 12% (v / v), the tartaric acid content is 6 g / L, and the pH of the simulated wine is adjusted to 3.3 with 1 mol / L NaOH. All solutions are stored at 4 ℃ until use.
1.5 Determination of aroma components SPME: Place 8 mL of sample in a 15 mL brown glass vial, add 2 g of NaCl, and add 8 μL of 22-octanol ethanol solution (the internal standard concentration in the sample is 8.22 mg / L). Equilibrate in a 40 ° C water bath for 40 minutes; insert the aging solid-phase microextractor into the sample bottle, pull it out after 40 minutes of adsorption, insert it into the gas chromatograph inlet, and analyze at 250 ° C for 5 minutes.
Qualitative and relative quantitative analysis: The random Xcalibur workstation N IST2002 standard spectrum library is used to automatically search the mass spectrum data of each component, and the retention index (see formula) and the standard spectrum are used to check the machine inspection results and confirm the aroma compounds. Semi-quantitative analysis of peaks (relative percentage of peak area) of detected aroma components using internal standard method.
The detection peak area of ​​the internal standard compound (2-octanol) is set to 100, and the detection peak areas of other aroma components are converted into semi-quantitative calculations in order to compare the differences in the content of each component in different samples.
Retention index Ki = 100 × n 100 [(tR i―tR n) / (tR (n 1) ―tRn)] where tR is the insurance transfer time from China Wine News? The analyzed compounds, n and n 1 represent the number of carbon atoms of normal paraffins, respectively.
1.6 Statistical analysis SAS statistical software was used to analyze the main components and cluster analysis of the aroma components, and to examine the differences in the content of various aroma compounds in the 2 seabuckthorn wines. In statistics, the content of undetected compounds is calculated as zero.
2 Results and analysis 2.1 Analysis of aroma components of sea buckthorn wine 2.2 Comparison and analysis of the content of various compounds in two products 2.3 Acetate Four kinds of acetate were detected in two products. Ethyl acetate is the highest content of this type of compound, and there is no significant difference between the two products, but the relative content of isoamyl acetoacetate and isobutyl acetate in ice wine is higher than that of dry wine.
Acetate and fatty acid ethyl esters are both important flavor substances produced by yeast during the fermentation of fruit wine. Acetate is the product of the combination of acetyl coenzymes and higher alcohols produced by the degradation of various amino acids and carbohydrates. It is the main source of fruit wine flavor .
Under the same fermentation conditions, the content of such compounds should be related to the content of carbohydrates and amino acids in the fermentation material. The raw juice of sea buckthorn ice wine comes from the frozen fruit of sea buckthorn naturally concentrated in winter, and the content of sugar and dry matter is obviously higher than that of fresh fruit.
2.4 Fatty acid ethyl ester Fruit wine fatty acid ethyl ester is produced by the esterification reaction between ethanol and lactic acid, succinic acid, acetic acid, butyric acid, caproic acid, caprylic acid, lauric acid, etc. in wine, and is also the main source of fruit wine fruit aroma.
The total content of fatty acid ethyl ester in dry wine is higher than that of ice wine. Mainly long-chain fatty acid esters, such as ethyl 2-hydroxypropionate, ethyl caproate, ethyl octanoate, ethyl sunflower, diethyl succinate and monoethyl succinate. The threshold value of such fatty acid esters is high, about 100 mg / L. Although the content is relatively high, the contribution to the flavor of sea buckthorn wine is not obvious. The high content of fatty acid ethyl ester may not significantly increase the flavor of dry wine. The types of fatty acid esters in ice wine are more abundant, and 16 kinds are detected, while only 14 kinds are in dry wine.
2.5 Higher alcohols Some higher alcohols can give the typical aroma of fruit wine. Most of the higher alcohols are by-products of yeast fermentation.
In addition to ethanol, higher alcohols account for about 50% of the aroma components of wine. The relative contents of these compounds in seabuckthorn dry wine and seabuckthorn ice wine are relatively high. Higher alcohol is an important aroma component of fruit wine. Due to the lower threshold, lower levels of compounds also make an important contribution to the aroma of fruit wine. In ice wine, the relative content of 2-methyl-1-propanol and 2-butanol is significantly higher than that of dry wine, and the content of n-hexanol in dry wine is higher than that of ice wine.
2.6 Terpene dilute compounds Terpene dilute compounds are important flavoring substances derived from raw materials of fruit wine. They are mainly produced by the degradation of the combined flavor precursor glycoside compounds and carotenoids, which can determine the typicality of fruit wine. A total of 5 terpene compounds were detected in sea buckthorn ice wine and 4 in dry wine. Eucalyptus oil was only detected in ice wine.
2.7 Ketones and aldehyde compounds were detected in 6 ketoaldehyde compounds in seabuckthorn ice wine, and 4 species were detected in seabuckthorn dry wine. The relative content of these compounds in seabuckthorn ice wine was higher than that of dry wine. From the point of view of the types and relative contents of compounds, the difference of these compounds in the two products is most obvious. Whether the difference in the content of these compounds in the two products determines the difference in the aroma quality of the products requires further study.
2.8 Fatty acids The source of fatty acids in seabuckthorn wine is mainly the organic acids rich in seabuckthorn juice and organic acids produced during yeast fermentation. The aroma caused by fatty acids is relatively stable, similar to the smell of soap, candles and stearic acid. The relative content of organic acids was not significantly different between the two products.
2.9 Principal component analysis Using relative content data as a variable, the principal component analysis was performed on the aroma components of 49 kinds of seabuckthorn wines detected. The contribution rate of the four principal components is close to 100%. The contribution rate of the first 2 principal components is 71%, which can explain most of the variable information.
The top 10 compounds with the main factors PC1 and PC2 loading. It can be seen from Table 2 that the contribution rate of a single aroma component to the main factor is low.
Therefore, it is impossible to distinguish the aroma characteristics of sea buckthorn wine by using a few ingredients. It is necessary to comprehensively analyze and discriminate the aroma components of sea buckthorn wine. Except for ethyl 2-hydroxypropionate, the compounds with a larger contribution rate to the main factors PC1 and PC2 are different. There are a total of 19 compounds, which can be judged from the relative content. The main compound of the product's aroma composition.
2.10 Cluster analysis results The cluster analysis of two seabuckthorn wine product samples with the relative content of 7 types of compounds such as acetate as variables can separate the 2 types of samples by product type, and the samples of similar products are in the same group. The characteristics of the comprehensive aroma components of the two products are different. The relative content of aroma compounds can be used as an effective quantitative indicator to distinguish the aroma quality of the two types of products.
3 Conclusion There are certain differences in the types and contents of aroma compounds in dry seabuckthorn wine and ice wine; there are certain differences in the comprehensive aroma characteristics of the two seabuckthorn wines.
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