CN111929397A

CN111929397A - Method for analyzing protein and flavor of air-dried preserved meat

Info

Publication number: CN111929397A
Application number: CN202010895085.XA
Authority: CN
Inventors: 曲直; 郑善清; 刘楠; 李瑞玲; 李博
Original assignee: Henan University
Current assignee: Henan University
Priority date: 2020-08-31
Filing date: 2020-08-31
Publication date: 2020-11-13

Abstract

The invention discloses a method for analyzing protein and flavor of air-dried preserved meat, which comprises the following steps: preparing preserved meat; analyzing flavor substances; determination of sarcoplasmic proteins; measuring SH and S-S group levels; measuring the content of carbonyl; measurement of protein surface hydrophobicity (H0); circular Dichroism (CD) spectroscopic analysis of sarcoplasmic proteins; and (5) carrying out statistical analysis. The invention has the advantages that: the flavor forming mechanism of the air-dried preserved meat is clarified from the combination of food chemistry and computational mathematics, a theoretical basis is provided for establishing the scale processing engineering technology of the traditional meat product, and the method has very important research value and potential social and economic value for promoting the upgrading and reconstruction, carrying forward and developing of the traditional industry.

Description

Method for analyzing protein and flavor of air-dried preserved meat

Technical Field

The invention relates to the technical field of bacon production, in particular to a method for analyzing temperature and ionic strength of air-dried bacon sarcoplasmic proteins and myofibrillar proteins and flavor.

Background

Cured meat products represented by sausage and bacon are one of the oldest traditional meat products in China and even the world. The annual output of bacon in China reaches more than 200 million tons, the bacon is various and has obvious regional flavor characteristics, so the bacon is always a key research object of meat science, and particularly the research on the forming mechanism of the salted bacon flavor becomes the most popular topic in the meat research field in recent years. Although researchers at home and abroad have different research depths for different preserved meat products and a plurality of processing principles cannot be clarified, research results of a plurality of scholars show that protein can be degraded into a large number of free amino acids and other substances in the processing process, and the substances can be converted into a plurality of compounds with aromatic flavor. Therefore, the research on the change and action mechanism of protein in the processing process of the preserved meat products has important significance for deeply understanding various change mechanisms in the production process of the salted preserved meat products and disclosing the relationship between the change of lipid substances and the formation of flavor.

During the baking or airing process of the cured meat, the ion concentration of the buffer system of the cured meat is continuously changed, and the ion concentration and the temperature are used as two important factors to further interact and influence the protein.

Current state of research at home and abroad

The current situation of cured flavor substances

Chinese bacons are divided into a plurality of types, namely Guangdong bacons, Hunan bacons, Chuan bacons, Qian bacons and the like according to the flavor, and natural air-drying bacons and baked bacons can be divided according to the preparation method, wherein the former has long drying time (10-15 days), the latter is directly baked at high temperature (50-60 ℃) after being cured, the drying time is short (2-4 days), the baking processing mode is mostly adopted by large-scale enterprises at present, and the air-drying preparation mode is usually adopted by small enterprises or families. Some varieties also need to be smoked, and can be divided into a cold smoking method and a hot smoking method according to the heating temperature condition in the smoking process, wherein the Cantonese bacon is used as the characteristic bacon in south China and does not need to be smoked.

Cured meat products have many flavor precursors. Wherein lipid and protein hydrolysis are the main sources of precursor flavor generation. Lipid is precursor of aromatic flavor compounds (aldehyde, ketone and alcohol), protein is hydrolyzed to form peptide and free amino acid, and further changes occur, which have important influence on the taste and flavor of preserved meat, reducing sugar (mainly glucose and ribose) in meat and amino acid, peptide and protein are subjected to Maillard reaction at normal temperature or heating to generate a plurality of flavor compounds, such as ketone, aldehyde, furan, pyrazine, alcohol and the like, and the flavor is good for food. Spices are one of the main additives in the production of Cantonese bacon. It can impart special flavor to the product. The compounds produced by the lipid degradation may undergo subsequent reactions with amino acids or intermediates of the maillard reaction to produce flavour compounds which contribute to the overall aroma of the meat.

② the development of the flavor forming mechanism of cured meat

The biochemical changes that occur during the processing of cured meat products determine the flavor of the final product. The degradation of saccharides by lactic acid bacteria and the acidification thereof and the degradation of nitrate and nitrite by micrococcus during the processing of cured meat products have been widely studied. In recent years, protein degradation during processing has also been studied extensively, but the effect of these biochemical changes on flavor development and their interaction with flavor materials has not been clarified yet. The typical flavor of a cured meat product depends not only on the volatile flavor itself, but also on the ratio of volatile flavors to other components in the product and their interactions. Most of the research at present focuses on the degradation of glycerides into free fatty acids, monoglycerides and diglycerides and the change of carbonyl compounds during processing, which have a lower threshold and also play an important role in the flavor of the product. Degradation products of proteins, such as small peptides and amino acids, have also been studied extensively.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method for analyzing the protein and flavor of air-dried preserved meat, and solves the defects in the prior art.

In order to realize the purpose, the technical scheme adopted by the invention is as follows:

a method for analyzing the lipase activity and flavor of air-dried preserved meat comprises the following steps:

1. preparation of preserved meat

Rinsing the rib meat, pickling, tying, drying, finishing and packaging.

2. Headspace solid phase microextraction conditions

Aging of the extraction fiber head: for the first use, the 50/30 μm DVB/CAR/PDMS extraction fiber head was aged at 270 ℃ for 1h at the gas chromatography inlet.

Uniformly sampling the preserved meat, cutting into small pieces, weighing 3.0g of the preserved meat, putting the small pieces into a 15ml sample bottle, adsorbing the preserved meat at the constant temperature of 40 ℃ for 60min by using an 50/30 mu m DVB/CAR/PDMS extraction fiber head, and desorbing the preserved meat at the temperature of 250 ℃ of a sample inlet for 5min to obtain a sample flavor substance.

3. Flavor substance analysis

Extracting the flavor substances of the sample for 30min by adopting an SPME combined GC-MS analysis method, enriching volatile compounds at 60 ℃, analyzing the volatile compounds on the fiber head by using gas chromatography, comparing mass spectrum data of the volatile components with MEANLIB, REPLIB, WILLEY and NISTDEMO4 picture library data, confirming the identified compounds with a similarity index of more than 800, and carrying out peak area normalization quantitative analysis on the identified substances.

4. Determination of sarcoplasmic proteins

Extracting sarcoplasmic protein of the salted meat and extracting myofibrillar protein of the salted meat. Performing nitrogen measurement on the sarcoplasmic protein and myofibrillar protein;

5. measurement of SH and S-S group levels

SH group 2.5mL Tris-glycine buffer, 8mol/L urea, 20mol/L Ellman reagent were added to 0.5mL sarcoplasmic proteins and myofibrillar proteins, respectively. Incubating at room temperature for 1h, centrifuging at 8000 Xg for 15min, adding sarcoplasmic protein and myofibrillar protein in 0.2mL, respectively, and adding triglycine buffer solution in 2mL, urea in 10mol/L and min-mercaptoethanol in 0.02 mL. Standing at room temperature for 1h, mixing with cold 50% TCA to a final concentration of 10%, centrifuging at 3000 Xg for 15min, adding 3mL triglycine buffer, and precipitating with 8mol/L urea.

The absorbance was measured at 412nm with a spectrophotometer. The protein content was determined to be 280nm using Bovine Serum Albumin (BSA) as standard. The calculation formula is that mol SH/g is 73.53 multiplied by A412/C; mol total SH/g is 73.53 multiplied by A412/C; mol s/g-mol total SH/g-mol SH/g

In the formula, 73.53 is 106/1.36X 104, 1.36X 104 is molar extinction coefficient, C is protein sample concentration, mg/mL.

6. Determination of the carbonyl content

And (4) carbonyl analysis. Add 2ml sarcoplasmic protein and myofibrillar protein to 50% TCA respectively to 10% final concentration, centrifuge for 15min at 8000 Xg, wash precipitate with 3ml acetone to remove residual TCA. One precipitate was treated with 2ml of 2mol/L HCl and the other precipitate was treated with an equal volume of 0.2% (w/v)2, 4-Dinitrophenylhydrazine (DNPH) in 2mol/L HCl and left at room temperature for 1 h. The precipitate was centrifuged at 4000 Xg for 10min and washed with 2ml ethanol/ethyl acetate (1: 1). The precipitate was dissolved in 3ml of 6mol/L guanidine hydrochloride, and 20mmol/L sodium phosphate buffer, pH 6.5, was added. The protein concentration in the supernatant was calculated under 280nm hydrochloric acid control conditions using bovine serum albumin in 6mol/L guanidine as a standard. The absorbance was measured at 370nm with a spectrophotometer.

7. Determination of protein surface hydrophobicity (H0)

Surface hydrophobicity determination of sarcoplasmic proteins: each sarcoplasmic protein was serially diluted with 10mmol/L phosphate buffer (pH 7.5) to give a protein concentration in the range of 0.05-2.0 mg/mL. Then 4ml of each sarcoplasmic protein was added, and 20mol-8 mmol/L1-aniline-8-naphthalenesulfonate (ANS) was added. Fluorescence Intensity (FI) was measured at a wavelength of 390nm (excitation) and 470nm (emission) using a Cray Eclipse fluorescence photometer at 20. + -. 0.5 ℃. The initial slope of the FI versus protein concentration curve was calculated by linear regression analysis and used as an indicator of H0.

Measurement of hydrophobicity of myofibrils: to 1mL of myofibril suspension was added 1mg/mL bromophenol blue (BPB)40mol/L and mixed. A control without myofibrils was prepared by adding 40 polypropylene (1mg/mL BPB) to 1mL of 20mmol/L phosphate buffer at pH 6.0. Samples and controls were stirred at room temperature for 10min and centrifuged at 2000 Xg for 15 min. The absorbance of the supernatant was measured at 595nm against blank phosphate buffer. The BPB boundary amount is given by the following equation, where BPB boundary (commander) ═ 40 commander L × (O Dcontrol-ODsample)/ODcontrol.

8. Circular Dichroism (CD) spectroscopic analysis of sarcoplasmic proteins

And (3) measuring the sarcoplasmic protein by using an optical physical spectrum polarizer to obtain a CD spectrum. Using 10mmol/L phosphate buffer (pH 7.0), the protein concentration was about 0.1 mg/mL. The sarcoplasmic protein samples were scanned at 190-260 nm. All calculations assume an average of 110 amino acid residues. And (3) compressing the data by using CONN CD spectrum deconvolution software, and performing deconvolution on the data by using Molec software. The molecular weight (Da) was 4000 and the amino acid number was 36.

9. Statistical analysis

Statistical analysis and methodological comparison of the data obtained from steps 3 to 8 above was performed using SPSS Statistics V17. The data of the samples and the panelists were analyzed using one-way analysis of variance (ANOVA) for 0h, 6h, 18h, 36h, 54h and 72h, with significant differences at P < 0.05.

Further, step 4 is specifically as follows:

sarcoplasmic proteins of cured meat were extracted and slightly modified. 50g of the cured meat was added to 500mL of phosphate buffer and centrifuged at 5000 Xg at 4 ℃ for 15 min. The supernatant was sarcoplasmic proteins.

Extracting myofibrillar protein from the salted meat. 10g of the sample was added to 100ml of a solution having a pH of 6.5 containing 50mmol/L NaCl, 25mmol/L KCl, 3mmol/L MgCl2, 1mmol/L phenylmethanesulfonyl fluoride (PMSF) and 4mmol/L EDTA. The temperature was 4 ℃ and centrifugation at 2000 Xg for 15 min. Resuspended in 50ml of 0.45mol/L KCl,15.6mmol/L Na2HPO4,3.5mmol/L KH2PO4, pH 7.5.

50ml of sarcoplasmic proteins and 3ml of myofibrillar proteins were retained for nitrogen determination and the protein fraction was determined by sds-polyacrylamide gel electrophoresis. The sarcoplasmic and sarcoplasmic proteins were 1:1 mixed standard buffer containing 50 more readily compatible with L Tris-HCl 8mol/L urea, 2mol/L thiourea, 5% (v/v) beta mercaptoethanol, 2% (w/v) SDS, 0.1% (v/v) bromophenol blue at pH 6.8, heated at 100 ℃ for 5 minutes, and centrifuged at 8000 Xg for 5 minutes, respectively. One whole aliquot (15 μ L) of the supernatant was applied to the gel with 5% spacer gel and 15% resolving gel. The currents for the spacer gel and the resolving gel were 20mA and 40mA, respectively.

Compared with the prior art, the invention has the advantages that:

1. the influence of temperature and ionic strength on the protein and flavor of the air-dried preserved meat is researched, food chemistry and computational mathematics are combined, the construction and application of a neural network model under the condition of two hospitals in the air-dried preserved meat are established, and a theoretical template is provided for the research of other fields of video science.

2. Through research on the influence of temperature and ionic strength on sarcoplasmic protein, myofibrillar protein and flavor in the actual process and the simulation process of air-drying preserved meat processing, the mechanism of forming specific quality by the conventional meat product processing protein is disclosed, and a theoretical basis is provided for establishing the conventional meat product scale engineering technology.

Drawings

FIG. 1 is a graph of the change in nitrogen content of sarcoplasmic proteins and myofibrillar proteins during the processing of meat products according to the example of the present invention;

FIG. 2 is a graph showing the change in the levels of sarcoplasmic and myofibrillar proteins SH (a) and S-S groups (b) during the course of meat curing in accordance with the embodiment of the present invention;

FIG. 3 is a graph showing the change in carbonyl content of sarcoplasmic proteins and myofibrillar proteins during the processing of meat products according to the example of the present invention;

FIG. 4 is a graph showing changes in the surface hydrophobicity (Ho) of meat and myofibrillar proteins during the processing of examples of the present invention;

FIG. 5 is a far ultraviolet CD spectral band scan graph of sarcoplasmic proteins secondary structure according to an embodiment of the present invention;

FIG. 6 is a secondary structure diagram of sarcoplasmic proteins during the processing of marinated meat in accordance with an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings by way of examples.

1. preparation of preserved meat

Rinsing the rib meat, pickling, tying, drying, finishing and packaging.

Air-dried preserved meat

Pickling conditions are as follows: adding 3% of salt and 2% of white sugar at 4 ℃ for 12 h.

Drying conditions are as follows: outdoor hanging at 18:00 pm, recording the temperature three times (6: 00, 14:00, 22:00) per day, sampling, and hanging for seven days.

Cured meat

Drying conditions are as follows: the temperature is set in time intervals. At 8:00-20:00, taking 10 samples, wherein every two samples form a group, and the temperature of each group is respectively set to be 20 ℃, 25 ℃, 30 ℃, 35 ℃ and 40 ℃; at 20:00-24:00, the 10 samples were taken as one group at different temperatures in the previous period, i.e. five samples were taken as one group, two groups were used, the temperature was set at 4 ℃ and 8 ℃, the samples were taken each time the temperature was changed, and the drying was repeated for 72 hours at this temperature.

2. Headspace solid phase microextraction conditions

3. Flavor substance analysis

4. Determination of sarcoplasmic proteins

Sarcoplasmic proteins of cured meat were extracted and slightly modified. 50g of the cured meat was added to 500mL of phosphate buffer (15.6mmol/L Na2HPO4,3.5mmol/L KH2PO4, pH 7.5), centrifuged at 5000 Xg for 15min at 4 ℃ (BR4, Thermo, USA). The supernatant was sarcoplasmic proteins.

Extracting myofibrillar protein from the salted meat. 10g of the sample was added to 100ml of a solution having a pH of 6.5 containing 50mmol/L NaCl, 25mmol/L KCl, 3mmol/L MgCl2, 1mmol/L phenylmethanesulfonyl fluoride (PMSF) and 4mmol/L EDTA. Centrifuge at 2000 Xg for 15min at 4 ℃. Resuspended in 50ml of 0.45mol/L KCl,15.6mmol/L Na2HPO4,3.5mmol/L KH2PO4, pH 7.5.

5. Measurement of SH and S-S group levels

SH group 2.5mL Tris-glycine buffer (0.086mol/L Tris,0.09mol/L glycine,4mmol/L EDTA, pH 8.0), 8mol/L urea, 20mol/L Ellman reagent (4mg DTNB,1mL Tris-glycine buffer) were added to 0.5mL sarcoplasmic proteins and myofibrillar proteins, respectively. Incubating at room temperature for 1h, centrifuging at 8000 Xg for 15min, adding sarcoplasmic protein and myofibrillar protein in 0.2mL, respectively, and adding triglycine buffer solution in 2mL, urea in 10mol/L and min-mercaptoethanol in 0.02 mL. Standing at room temperature for 1h, mixing with cold 50% TCA to a final concentration of 10%, centrifuging at 3000 Xg for 15min, adding 3mL triglycine buffer, and precipitating with 8mol/L urea.

The absorbance was measured at 412nm with a spectrophotometer (UV-2450, Shimadzu, Japan). The protein content was determined to be 280nm using Bovine Serum Albumin (BSA) as standard. The calculation formula is that mol SH/g is 73.53 multiplied by A412/C; mol total SH/g is 73.53 multiplied by A412/C; mol s/g-mol total SH/g-mol SH/g

6. Determination of the carbonyl content

And (4) carbonyl analysis. Add 2ml sarcoplasmic protein and myofibrillar protein to 50% TCA respectively to 10% final concentration, centrifuge for 15min at 8000 Xg, wash precipitate with 3ml acetone to remove residual TCA. One precipitate was treated with 2ml of 2mol/L HCl and the other precipitate was treated with an equal volume of 0.2% (w/v)2, 4-Dinitrophenylhydrazine (DNPH) in 2mol/L HCl and left at room temperature for 1 h. The precipitate was centrifuged at 4000 Xg for 10min and washed with 2ml ethanol/ethyl acetate (1: 1). The precipitate was dissolved in 3ml of 6mol/L guanidine hydrochloride, and 20mmol/L sodium phosphate buffer, pH 6.5, was added. The protein concentration in the supernatant was calculated under 280nm hydrochloric acid control conditions using bovine serum albumin in 6mol/L guanidine as a standard. The absorbance was measured at 370nm with a spectrophotometer (UV-2450, Shimadzu, Japan).

7. Determination of protein surface hydrophobicity (H0)

Surface hydrophobicity determination of sarcoplasmic proteins: each sarcoplasmic protein was serially diluted with 10mmol/L phosphate buffer (pH 7.5) to give a protein concentration in the range of 0.05-2.0 mg/mL. Then 4ml of each sarcoplasmic protein was added, and 20mol-8 mmol/L1-aniline-8-naphthalenesulfonate (ANS) was added. Fluorescence Intensities (FI) were measured at wavelengths 390nm (excitation) and 470nm (emission) using a Cray Eclipse fluorescence spectrometer (Warran, USA) at 20 + -0.5 deg.C. The initial slope of the FI versus protein concentration curve was calculated by linear regression analysis and used as an indicator of H0.

Measurement of hydrophobicity of myofibrils: to 1mL of myofibril suspension was added 1mg/mL bromophenol blue (BPB)40mol/L and mixed. A control without myofibrils was prepared by adding 40 polypropylene (1mg/mL BPB) to 1mL of 20mmol/L phosphate buffer at pH 6.0. Samples and controls were stirred at room temperature for 10min and centrifuged at 2000 Xg for 15 min. The absorbance of the supernatant was measured at 595nm against blank phosphate buffer. The BPB boundary amount is given by the following equation, where BPB boundary (command) is 40 command L × (ODcontrol-ODsample)/ODcontrol.

8. Circular Dichroism (CD) spectroscopic analysis of sarcoplasmic proteins

The CD spectrum was obtained by measuring sarcoplasmic proteins with an applied photophysical spectrum polarimeter from Chirascan, England. Using 10mmol/L phosphate buffer (pH 7.0), the protein concentration was about 0.1 mg/mL. The sample was scanned at 190-260 nm. All calculations assume an average of 110 amino acid residues. And (3) compressing the data by using CONN CD spectrum deconvolution software, and performing deconvolution on the data by using Molec software. The molecular weight (Da) was 4000 and the amino acid number was 36.

9. Statistical analysis

Statistical analysis and methodological comparisons were performed using SPSS Statistics V17. The data of the samples and panelists were analyzed using one-way analysis of variance (ANOVA) with time (levels: 0, 6, 18, 36, 54 and 72h) and P <0.05 was significantly different.

The experimental results are as follows:

as shown in tables 1 to 3:

TABLE 1 variation of material parameters during the drying of Guangdong bacon

TABLE 2 change of chemical characteristics of Guangdong bacon during drying

TABLE 3 amino acid composition (g/100g) of Guangdong cured meat when dried

The changes of proteins in the processing processes of the air-dried preserved meat and the baked preserved meat are analyzed, the oxidation degree of the preserved meat protein is evaluated by using the carbonyl value and the S-S, SH content, the surface hydrophobicity of the proteins in the two processing processes is analyzed, and the secondary structure in the processing process of the baked preserved meat is researched, and the results are shown in fig. 1 to 6.

It will be appreciated by those of ordinary skill in the art that the examples described herein are intended to assist the reader in understanding the manner in which the invention is practiced, and it is to be understood that the scope of the invention is not limited to such specifically recited statements and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.

Claims

1. A method for analyzing the lipase activity and flavor of air-dried preserved meat is characterized by comprising the following steps:

1. preparation of preserved meat

Rinsing, pickling, tying, drying, finishing and packaging rib meat;

2. headspace solid phase microextraction conditions

Aging of the extraction fiber head: when the fiber head is used for the first time, the 50/30 mu m DVB/CAR/PDMS extraction fiber head needs to be aged for 1h at the gas chromatography sample inlet at 270 ℃;

uniformly sampling preserved meat, cutting into small pieces, weighing 3.0g of the preserved meat, putting the small pieces into a 15ml sample bottle, adsorbing the preserved meat at constant temperature of 40 ℃ for 60min by using an 50/30 mu m DVB/CAR/PDMS extraction fiber head, and desorbing the preserved meat at 250 ℃ of a sample inlet for 5min to obtain a sample flavor substance;

3. flavor substance analysis

Extracting a sample flavor substance by adopting an SPME combined GC-MS analysis method for 30min at 60 ℃ to enrich volatile compounds, analyzing the volatile compounds on a fiber head by using gas chromatography, comparing mass spectrum data of the volatile components with MEANLIB, REPLIB, WILLEY and NISTDEMO4 picture library data, wherein the similarity index is more than 800 for compounds which are confirmed to be identified, and carrying out peak area normalization quantitative analysis on each identified substance;

4. determination of sarcoplasmic proteins

Extracting sarcoplasmic protein of the salted meat, and extracting myofibrillar protein of the salted meat; performing nitrogen measurement on the sarcoplasmic protein and myofibrillar protein;

5. measurement of SH and S-S group levels

SH group respectively adds 2.5mL Tris-glycine buffer, 8mol/L urea and 20mol/L Ellman reagent into 0.5mL sarcoplasmic protein and myofibrillar protein; incubating at room temperature for 1h, centrifuging at 8000 Xg for 15min, adding sarcoplasmic protein and myofibrillar protein in 0.2mL respectively into total SH component, adding triglycine buffer solution in 2mL, urea in 10mol/L and min-mercaptoethanol in 0.02 mL; standing at room temperature for 1h, mixing with cold 50% TCA until the final concentration is 10%, centrifuging at 3000 Xg for 15min, adding 3mL of triglycine buffer solution, and precipitating with 8mol/L urea;

measuring absorbance at 412nm with a spectrophotometer; measuring the protein content to 280nm by taking Bovine Serum Albumin (BSA) as a standard; the calculation formula is that mol SH/g is 73.53 multiplied by A412/C; mol total SH/g is 73.53 multiplied by A412/C; mol s/g-mol total SH/g-mol SH/g

Wherein 73.53 is 106/1.36 × 104,1.36 × 104 is a molar extinction coefficient, C is a protein sample concentration, mg/mL;

6. determination of the carbonyl content

Analyzing carbonyl; adding 2ml of sarcoplasmic protein and myofibrillar protein into 50% TCA respectively to a final concentration of 10%, centrifuging for 15min at 8000 Xg, washing and precipitating with 3ml of acetone, and removing residual TCA; one precipitate was treated with 2ml of 2mol/L HCl and the other precipitate was treated with an equal volume of 0.2% (w/v)2, 4-Dinitrophenylhydrazine (DNPH) in 2mol/L HCl and left at room temperature for 1 h; centrifuging at 4000 Xg for 10min, and washing the precipitate with 2ml ethanol/ethyl acetate (1: 1); dissolving the precipitate in 3ml of 6mol/L guanidine hydrochloride, adding 20mmol/L sodium phosphate buffer solution, and adjusting the pH value to 6.5; calculating the protein concentration of the supernatant by taking bovine serum albumin in 6mol/L guanidine as a standard under the hydrochloric acid control condition of 280 nm; measuring absorbance at 370nm with a spectrophotometer;

7. determination of protein surface hydrophobicity (H0)

Surface hydrophobicity determination of sarcoplasmic proteins: serial dilutions of each sarcoplasmic protein were performed with 10mmol/L phosphate buffer (pH 7.5) to give a protein concentration in the range of 0.05-2.0 mg/mL; then adding 4ml of each sarcoplasmic protein, and respectively adding 20mol-8 mmol/L1-aniline-8-naphthalene sulfonate (ANS); measuring Fluorescence Intensity (FI) at wavelengths 390nm (excitation) and 470nm (emission) using a Cray Eclipse fluorescence photometer at 20 + -0.5 ℃; calculating the initial slope of the FI and protein concentration curve through linear regression analysis, and using the initial slope as an index of H0;

measurement of hydrophobicity of myofibrils: adding 1mg/mL bromophenol blue (BPB)40mol/L into 1mL myofibril suspension, and mixing uniformly; at pH 6.0, 40 polypropylene, 1mg/mL BPB, was added to 1mL of 20mmol/L phosphate buffer to prepare a control without myofibrils; the sample and control were stirred at room temperature for 10min, centrifuged at 2000 Xg for 15 min; measuring the absorbance of the supernatant at 595nm with an empty phosphate buffer; a BPB boundary amount given by the following equation, where BPB boundary (commander) ═ 40 commander lx (OD control-ODsample)/ODcontrol;

8. circular Dichroism (CD) spectroscopic analysis of sarcoplasmic proteins

Measuring the sarcoplasmic protein by using an optical physical spectrum polarizer to obtain a CD spectrum; using 10mmol/L phosphate buffer (pH 7.0), the protein concentration was about 0.1 mg/mL; scanning the sarcoplasmic protein sample at 190-260 nm; all calculations assume an average of 110 amino acid residues; compressing data by using CONN CD spectrum deconvolution software, and performing deconvolution on the data by using Molec software; a molecular weight (Da) of 4000 and an amino acid number of 36;

9. statistical analysis

Performing statistical analysis and method comparison on the data obtained in the steps 3 to 8 by using SPSS Statistics V17; the data of the samples and the panelists were analyzed by one-way anova for 0h, 6h, 18h, 36h, 54h and 72h, with a significant difference when P < 0.05.

2. The method for analyzing the lipase activity and the flavor of the air-dried preserved meat according to claim 1, wherein the step 4 is as follows:

extracting sarcoplasmic proteins of the cured meat, and slightly modifying the sarcoplasmic proteins; taking 50g of salted meat, adding 500mL of phosphate buffer, centrifuging at 4 ℃ and 5000 Xg for 15 min; the supernatant is sarcoplasmic protein;

extracting myofibrillar protein from the salted meat; 10g of the sample was added to 100ml of a solution having a pH of 6.5 containing 50mmol/L NaCl, 25mmol/L KCl, 3mmol/L MgCl2, 1mmol/L phenylmethanesulfonyl fluoride (PMSF) and 4mmol/L EDTA; centrifuging at 2000 Xg for 15min at 4 deg.C; resuspending in 50ml of 0.45mol/L KCl,15.6mmol/L Na2HPO4,3.5mmol/L KH2PO4, pH 7.5;

50ml of sarcoplasmic proteins and 3ml of myofibrillar proteins were retained for nitrogen determination and the protein fraction was determined by sds-polyacrylamide gel electrophoresis; the sarcoplasmic and sarcoplasmic proteins were 1:1 mixed standard buffer containing 50 more readily compatible L Tris-HCl 8mol/L urea, 2mol/L thiourea, 5% (v/v) beta mercaptoethanol, 2% (w/v) SDS, 0.1% (v/v) bromophenol blue at pH 6.8, heated at 100 ℃ for 5 minutes, centrifuged at 8000 Xg for 5 minutes, respectively; one whole aliquot (15 μ L) of supernatant was applied to the gel, 5% for spacer gel and 15% for solution gel; the currents for the spacer gel and the resolving gel were 20mA and 40mA, respectively.