Method for pickling dry-pickled ham by ultrahigh pressure auxiliary method

Abstract

The invention relates to the technical field of food processing, in particular to a method for pickling dry-pickled ham by an ultrahigh pressure auxiliary method. In order to improve the traditional ham processing technology, the pickling speed of dry-pickled ham can be accelerated, the pickling time can be shortened, and the risk of microbial pollution can be reduced. According to the technical scheme, the method comprises the following steps: cleaning blood on the surface of fresh pig hind leg meat, removing fat and fascia, cutting, and pre-cooling at 4 DEG C for 24 hours; pickling with sea salt, salting once every other day for three times, uniformly spreading salt to rub the surface, and placing in a refrigerator at 4 DEG C after the salting is completed; placing the pickled meat blocks in a vacuum sealing bag, performing vacuum packaging, then performing ultrahigh pressure treatment, and performing treatment under ultrahigh pressure for a period of time; and hanging the meat blocks subjected to ultrahigh pressure treatment in a room with the temperature of 10-15 DEG C and the relative humidity of 75-80%, standing for 21 days, and transferring the meat blocks into a constant-temperature and constant-humidity box with the temperature of 20-22 DEG C and the relative humidity of 65-70% until the meat blocks are completely mature.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a method for curing dry-cured ham using an ultrahigh pressure assisted method. Background Art

[0002] Dry-cured fermented ham is a typical meat product produced in the Mediterranean region. It has a unique taste and is rich in nutrients. Compared with general meat products, fermented meat products contain more polypeptides and a richer variety of amino acids in a more reasonable proportion. After being cured, the pork hind leg meat undergoes a series of fermentation and decomposition, making the nutrients easier to be absorbed by the human body. At the same time, it has anti-hypertensive and antioxidant effects, which are beneficial to the health of consumers. Meat curing is an important part of meat processing. At present, meat curing has changed from the simple preservation in the past to a processing method to improve the flavor and color and improve the quality of meat. However, the traditional static curing process not only has a long production process and a high salinity in the meat, but is also prone to microbial contamination and other phenomena, making it difficult to adapt to the requirements of modern industrial production.

[0003] The existing ham production process takes a long time. During the fermentation process, the protein and fat in the ham muscle undergo microbial, biochemical and physicochemical changes. The resulting hydrolysis or oxidation reaction products and their secondary products are enough to form the unique flavor and texture of the ham.

[0004] In recent years, a variety of technologies have been applied to meat pickling, including low-temperature plasma technology, ultrasonic technology, microwave technology, etc. These new pickling methods can effectively improve the quality of meat and increase the pickling rate, but the ultrasonic-assisted method will generate heat during the processing, which can easily damage the nutrients inside the meat; the low-temperature plasma-assisted method has high requirements for equipment and is complex to operate.

[0005] Ultrahigh pressure is a new type of non-thermal food processing technology that can effectively kill microorganisms in food. Since high pressure only acts on non-covalent bonds such as hydrogen bonds, ionic bonds and hydrophobic bonds in biological macromolecules, it has no obvious effect on the covalent bonds of small molecular compounds such as vitamins, pigments and flavor substances, so it can better maintain the original nutrition, color and flavor of food. It is mostly used in fruit juice sterilization, active substance extraction, and food quality improvement. However, there are few studies on the use of ultrahigh pressure technology to intervene in the pickling period of traditional fermented meat.

[0006] The patent number is 201010031346X, and the patent name is "A method for producing low-temperature and low-salt ham using ultra-high pressure". It discloses a method for producing low-salt ham under low-temperature conditions with the assistance of ultra-high pressure. This method reduces the amount of salt used in the ham when it is pickled. The reduction in the amount of salt may cause the ham to fail to reach the flavor of ham products sold on the market. Summary of the invention

[0007] In view of this, the present invention provides a method for dry-cured ham by ultrahigh pressure assisted method in order to improve the traditional ham processing technology, so as to speed up the curing rate of dry-cured ham, shorten the curing time and reduce the risk of microbial contamination. The method is simple to operate, has less loss of nutrients, good flavoring effect, and further improves the quality of the ham.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for curing dry-cured ham by ultra-high pressure assisted method, the steps are:

[0009] Step 1) clean the fresh pork hind leg meat to remove blood and fat, fascia, cut into pieces and precool at 4°C for 24 hours;

[0010] Step 2) Use sea salt to marinate, apply salt once every day for 3 times in total, sprinkle salt evenly on the surface and rub it. After completion, place it in a 4°C refrigerator;

[0011] Step 3) placing the meat pieces in step 2) in a vacuum sealed bag, vacuum-packing and then ultra-high pressure, and treating under ultra-high pressure for a certain period of time;

[0012] Step 4) The ultrahigh pressure treated meat is hung in a room at 10-15°C and a relative humidity of 75%-80% for 21 days, and then transferred to a constant temperature and humidity chamber at 20-22°C and a relative humidity of 65%-70% until the meat is fully fermented.

[0013] Furthermore, in step 2), the first amount of salt applied is 4% of the mass of the ham, and the second and third amounts of salt applied are 2% of the mass of the ham, and the pickling time after each salting is 7 days.

[0014] Furthermore, the processing pressure of step 3) is 100-500 MPa, and the holding time is 10-50 min.

[0015] Compared with the prior art, the advantages and effects of the present invention are as follows:

[0016] 1) The present invention adopts ultra-high pressure assisted pickling, which has the advantages of low pickling temperature and short pressure holding time, and also avoids the destruction of the nutrients in the ham by thermal effect. After ultra-high pressure treatment, the sodium chloride content in the meat increased by 23%, and the final fermentation time was shortened by 1 / 3. At the same time, the water holding capacity increased by 14%. The salt-soluble protein content increased by 14.5%, and the color change of the meat was small, which had little effect on naked eye observation and was easy for consumers to accept.

[0017] 2) The method of the present invention is easy to operate, can retain the nutrients of dry-cured ham to a large extent, meets consumers' needs for product functionality and flavor, and has a broad application market.

[0018] 3) The present invention improves upon the traditional ham processing technology by adding an ultra-high pressure auxiliary pickling process, which not only saves the time for pickling meat, but also tenderizes the meat to a certain extent, making the meat more flavorful.

[0019] 4) The present invention is based on a single factor test, and uses the NaCl content, chromaticity, water holding capacity, salt-soluble protein content, moisture content, and pH value of the dry-cured ham as screening conditions to obtain the ultra-high pressure conditions that best improve the curing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The effect of ultra-high pressure on the sodium chloride content of ham.

[0021] Figure 2 The effect of ultra-high pressure on the moisture content of ham.

[0022] Figure 3 The effect of ultra-high pressure on the water holding capacity of ham.

[0023] Figure 4 Effect of ultrahigh pressure on the salt-soluble protein content of ham.

[0024] Figure 5 The effect of ultrahigh pressure on pH value of ham.

[0025] Figure 6 The effect of holding time on the sodium chloride content of ham.

[0026] Figure 7 The effect of holding time on the moisture content of ham.

[0027] Figure 8 The effect of pressure holding time on the water holding capacity of ham.

[0028] Fig. 9 The effect of holding time on the salt-soluble protein content of ham.

[0029] Fig.10 The effect of holding time on pH value of ham.

[0030] Fig.11 These are MASSON-stained sections of ham muscle fiber tissue treated under optimal ultrahigh pressure conditions (4×, 20×).

[0031] Fig.12 In order to study the effect of optimal ultrahigh pressure treatment conditions on the dispersion of sodium chloride in ham, SEM-EDX was used to observe the longitudinal sections of ham tissues under different treatments.

[0032] Fig.13 Comparison of sodium chloride content in the control group and the UHP treatment group from the beginning to the end of the pickling period. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] As a cold processing technology, ultra-high pressure technology does not change the temperature during the treatment process, and the compounds in the food do not break covalent bonds, so the chemical changes are very small, so that the original color, flavor, texture and nutritional components of the food can be retained to the greatest extent. In addition, ultra-high pressure technology has the advantages of stable temperature, simple operation, short curing time and high efficiency in meat curing processing. The present invention studies the influence of ultra-high pressure pressure and pressure holding time on the curing effect of dry-cured ham, in order to change the curing time of traditional ham, further determine the optimal process parameters for improving the curing efficiency of dry-cured ham, and provide a basis for ultra-high pressure to improve the early curing efficiency of meat.

[0035] This embodiment provides a method for ultra-high pressure assisted dry-cured ham, the steps of which are:

[0036] Step 1) clean the fresh pork hind leg meat to remove blood and fat, fascia, cut into pieces and precool at 4°C for 24 hours;

[0037] Step 2) Use sea salt for pickling, apply salt once every day, for a total of 3 times, sprinkle salt evenly on the surface and rub it, and then place it in a 4°C refrigerator; the amount of salt used for the first time is 4% of the mass of the ham, and the amount of salt used for the second and third times is 2% of the mass of the ham. Pickle for 7 days after each salting, for a total of 21 days.

[0038] Step 3) The meat pieces prepared in step 2) are placed in vacuum sealed bags respectively, and subjected to ultra-high pressure treatment after vacuum packaging; the extraction pressure is 100-500 MPa, and the pressure holding time is 10-50 minutes.

[0039] Step 4) The meat blocks in step 3) are hung in a room at 10-15°C and a relative humidity of 75%-80% for 21 days, and then transferred to a constant temperature and humidity chamber at 20-22°C and a relative humidity of 65%-70% until the meat blocks are fully fermented, during which samples are taken every 6 days.

[0040] The present invention adopts the following method to measure the sodium chloride content, moisture content, water holding capacity, salt-soluble protein content, pH value and chromaticity of ham during the pickling period, and to measure the types of volatile compounds and free amino acids in mature ham:

[0041] Determination of sodium chloride content: The pickled sample after step 3) and the sample during fermentation in step 4) were chopped, mixed with double distilled water at 25°C to 60 mL, and then vigorously shaken and left for 2 hours to obtain a water extract. Then, the sample was filtered through glass wool, and the sodium chloride content in the sample was determined using a digital salinity meter (Japan Atuo PAL-SALT).

[0042] Determination of moisture content: Take 1-2 g of the sample after pickling in step 3) and place it in a near-infrared automatic moisture meter to determine the moisture content;

[0043] Determination of water holding capacity: Take 2-3 g of the sample after pickling in step 3), centrifuge it at 4°C (300 r / min, 10 min), and record the sample weight after taking it out. Water holding capacity (%) = (sample weight before centrifugation - sample weight after centrifugation) / sample weight before centrifugation × 100%.

[0044] Determination of salt-soluble protein content: Weigh 4g of the sample after pickling in step 3), cut it into pieces, add 40mL of extract (0.1mol / L NaCl, 10mmol / L Na3PO4·12H2O, 2mmol / L MgCl2, 1mmol / L EGTA, pH=7.0), homogenize in a homogenizing bag, centrifuge at 4°C (4500r / min, 15min) after standing, take the precipitate and centrifuge it again, dissolve the precipitate and the centrifuge tube with 0.1mol / L NaCl at a ratio of 1:4, and centrifuge it twice (4500r / min, 15min) to obtain myofibrillar protein isolate. Use BCA kit to detect protein content.

[0045] Determination of chromaticity: Cut the ham that has been pickled after step 3) into a meat sample of 4cm×3cm×1.5cm (length×width×height), expose the cut surface to air for 30min, and use a colorimeter to determine the L*, a* and b* values. For each sample, three points are randomly selected from the lean meat part for determination, and each point is measured three times. The average value of each point is taken, and the total average value is taken as the chromaticity value of the meat sample.

[0046] Determination of pH value: Take 5 g of the pickled sample after step 3), add 50 ml of distilled water, homogenize and filter, collect the supernatant and let it stand for 30 minutes, and then use a pH meter to determine the pH value of the sample.

[0047] MASSON staining: Masson staining was used to show the myofibers and collagen fibers in the ham muscle tissue. First, the paraffin sections were dehydrogenated to water in the order of xylene I and xylene II, each for 20 minutes, 100% ethanol I, 100% ethanol II and 75% ethanol for 5 minutes each. Second, the sections were saturated in Masson A overnight and rinsed with tap water. The other two reagents of Masson B and C were prepared in a 1:1 ratio. The sections were stained in Masson solution for 1 minute and rinsed with tap water. They were placed in 1% hydrochloric acid alcohol for differentiation and then rinsed. Third, the sections were saturated in Masson D for 6 minutes, then immersed in Masson E for 1 minute and in Masson F for 2 to 30 seconds. Rinse with 1% glacial acetic acid and dehydrated in twice anhydrous ethanol, 100% ethanol and xylene for 5 minutes.

[0048] SEM-EDX spectral analysis: Cut the meat sample slices (1×3×3mm) from 1 cm below the meat surface. 3 ), the samples were fixed by oven drying instead of immersion in 2.5% (v / v) glutaraldehyde to prevent the dissolution of sodium chloride. An X-ray detector (X-Max 80, Oxford, UK) was then used to observe the NaCl in the meat samples. + and Cl - distribution.

[0049] Determination of volatile compounds: Weigh 5 g of the mature ham sample after step 4), cut it into pieces and put it into a 10 mL headspace bottle, and incubate it at 50°C for 30 minutes. Use an SPME fiber (30 / 50μm DVB / CAR / PDMS) to extract the volatile compounds in the headspace for 30 minutes, and then desorb on the gas chromatograph injector for 5 minutes, with the injection port temperature at 250°C. Use an Elite-MS (30m×0.25mm×0.25μm) column to separate volatile organic compounds. The carrier gas is 99.999% high-purity helium with a flow rate of 1.00mL / min. The mass spectrometry conditions are EI electron source, ion source of 70eV, and temperature of 230°C. The experiment adopts full scan mode with a scan range of 45m / z to 450m / z.

[0050] Determination of amino acid types: Weigh 5g of the mature ham sample after step 4) into a 50mL centrifuge tube, add 30mL of 5% trichloroacetic acid solution, homogenize at 12000r / min, put in a refrigerator at 4℃ for 30min, centrifuge (5000r / min, 15min), filter the supernatant with a 0.22μm needle filter and test. Accurately pipette 20μL of sample, add 180μL of methanol, vortex for 1min, centrifuge at 4℃14000g for 20min, take 50μL of supernatant to a 1.5mL centrifuge tube and blow dry with nitrogen, add 50μL of 50% acetonitrile aqueous solution, vortex for 1min, add 30μL of 10 mg / mL dansyl chloride solution and 40μL of 0.5M sodium carbonate-ammonium bicarbonate buffer solution, seal and vortex quickly for 1min, centrifuge for 5s, and react at a constant temperature oscillator at 60℃ for 30min. After the reaction is completed, let it stand at room temperature for 5 minutes, add 10μL of 0.25 M sodium hydroxide solution, vortex for 1 minute, centrifuge for 5 seconds, and react again at 60℃ for 10 minutes. After the reaction is completed, return to room temperature, add 70μL of 10% formic acid solution, vortex for 1 minute, centrifuge at 4℃14000g for 15 minutes, take the supernatant to the injection vial, and detect it on the machine. This experiment uses LC-ESI-MS / MS (UHPLC-Qtrap) to qualitatively and quantitatively detect the target in the sample. The specific parameters are as follows: Chromatographic conditions: ExionLC AD system, Waters HSS T3 (2.1x100 mm, 1.8μm) liquid chromatography column, column temperature 40℃, injection volume 2μL. Mobile phase A (0.1% formic acid water), mobile phase B (0.1% formic acid methanol). Mass spectrometry conditions: SCIEX QTRAP 6500+, positive mode detection, Curtain Gas (CUR) was 35, Collision Gas (CAD) was Medium, IonSpray Voltage (IS) was +5000, Temperature (TEM) was 350, Ion Source Gas1 (GS1) was 60, and Ion Source Gas2 (GS2) was 60.

[0051] 1. Single factor test:

[0052] Two factors that mainly affect the curing effect of dry-cured ham, namely, treatment pressure and pressure holding time, were selected for single factor experiment; the cured ham was obtained under the conditions of treatment pressure of 100, 200, 300, 400, 500 MPa and pressure holding time of 10, 20, 30, 40, 50 min, and the effects of each factor on the sodium chloride content, moisture content, water holding capacity, salt-soluble protein content, chromaticity and pH value of the ham during the curing period were investigated respectively;

[0053] 2. Single factor test results:

[0054] A: Effects of treatment pressure on sodium chloride content, moisture content, water holding capacity, salt-soluble protein content, pH value and chromaticity of ham during the curing period

[0055] The results show that during the pickling process, the sodium chloride content in the ham increases first and then decreases with the pressure. At 200MPa, the sodium chloride content reaches the maximum value. Figure 1 As shown. Therefore, 200MPa is the best pressure condition for improving the pickling effect of ham. As the pressure increases, the sodium chloride content in the ham increases. This is because under the mechanical effect of ultra-high pressure, the sample tissue cells rupture, causing the expansion of capillaries and the formation of pores, allowing sodium chloride to fully enter and increase the salt content of the ham. When the processing pressure exceeds 500MPa, the sodium chloride content decreases. The reason is that when the processing pressure is too high, the osmotic pressure difference between the inside and outside of the tissue cells is too large, causing sodium chloride and other macromolecular substances to seep out.

[0056] The moisture content tends to decrease gradually with pressure changes, such as Figure 2 As shown. Ultrahigh pressure processing will cause the destruction or formation of non-covalent bonds such as hydrogen bonds, ionic bonds and hydrophobic bonds in food. Compared with the control group (ham that has not been treated with ultrahigh pressure and has the same pickling and fermentation steps), the moisture content of the ham in the 400 and 500 MPa treatment groups is significantly reduced. Ultrahigh pressure can allow more salt to enter the meat and dissolve salt-soluble proteins. High pressure affects the hydration of proteins, causing some water to be freed from the tissue, thereby reducing the moisture content.

[0057] The water holding capacity increases first and then decreases with pressure changes, such as Figure 3 As shown. Water holding capacity is an important quality indicator of meat, which directly affects the color, juiciness and tenderness of meat. Compared with the control group, ultra-high pressure treatment reduces the water loss of ham during the curing period, and the difference is significant when the pressure is 500MPa. This shows that ultra-high pressure treatment can improve the water holding capacity of ham during the curing period. This may be because the mechanical effect of ultra-high pressure destroys the myofibril structure in the ham, allowing the myofibrillar protein to hold more water. At the same time, more salt enters the meat fiber after ultra-high pressure treatment, so that more protein side chains bind to water, improving the water holding capacity of ham during the curing period.

[0058] The content of salt-soluble protein first increases and then decreases with the increase of treatment pressure, e.g. Figure 4As shown. At 200MPa, the salt-soluble protein content reached the maximum value, increasing by 30.3% compared with the control group. The reason may be that the ultra-high pressure treatment with a relatively small pressure causes the myofibrils to swell, causing their structure to break and decompose into short filaments, resulting in an increase in protein content. When the pressure exceeds 400MPa, the salt-soluble protein content decreases. Due to the mechanical and physical destruction of salt-soluble proteins by ultra-high pressure, the protein structure denatures, causing the protein in the ham muscle to dissolve, resulting in a decrease in the protein content in the muscle tissue. Most of the macromolecular proteins are decomposed into small molecular substances such as amino acids, and the nutritional content of the ham is reduced.

[0059] The pH value gradually increases with the treatment pressure, such as Figure 5 As shown. This may be due to the denaturation of certain proteins during the ultra-high pressure process, or due to the decomposition of nitrogen-containing substances (such as free amino acids, etc.). It proves that the ham during the pickling period produced a large number of alkaline substances under the action of ultra-high pressure, causing the pH to rise. There is no significant difference between the 100-400MPa treatment and the control group, indicating that the lower pressure treatment has less effect on the pH of the ham.

[0060] The change of chromaticity with treatment pressure is shown in Table 1. As the pressure increases, the L* value increases, the a* value decreases, and the b* value shows a downward trend. The muscle gradually loses its red color and turns gray-pink. This is mainly because the pressure of ultra-high pressure rises by relying on water pressure. Part of the myoglobin is destroyed under the action of pressure, and the hemoglobin is diluted. The increase in L* value may be related to the denaturation and coagulation of protein. Protein coagulation changes the surface properties of the sample, increases light reflection and produces white. At the same time, ultra-high pressure promotes the cleavage of water molecules to produce more hydroxyl free radicals, causing the myoglobin in the ham to be oxidized, thereby reducing the a* value. When the treatment pressure is greater than 200MPa, the chromaticity value of the ham during the curing period shows a significant change compared with the control group, indicating that ultra-high pressure treatment with lower pressure can better maintain the chromaticity of the ham and has no effect on consumer acceptability.

[0061] Table 1 Effect of treatment pressure on chromaticity of ham during curing period

[0062]

[0063] B: Effect of holding time on sodium chloride content, moisture content, water holding capacity, salt-soluble protein content, chromaticity and pH value of ham during the pickling period

[0064] The results show that the sodium chloride content increases first and then decreases with the pressure holding time. When the pressure holding time is 40 minutes, the sodium chloride content in the meat reaches the maximum value, and the pickling effect is improved by 23%. Figure 6As shown. Therefore, 40 minutes is the best holding time to improve the curing effect of ham. As the holding time increases, the sodium chloride content increases. The reason is that when the holding time is too long, the food will lose water, and the sodium chloride will dissolve in the free water and then dissolve, resulting in a decrease in the sodium chloride content in the tissue.

[0065] The moisture content gradually decreases with the pressure holding time, such as Figure 7 As shown in the figure. It may be that the ultra-high pressure treatment squeezed out the water in the ham, causing the water loss, resulting in a decrease in its moisture content. Subsequently, as the holding time increased, the protein denatured and combined with some of the squeezed out water, causing the moisture content to rise slightly. However, when the holding time increased to 40 minutes, a small amount of water was squeezed out again, and the moisture content decreased to 57.63%.

[0066] The water holding capacity increases first and then decreases with the pressure holding time, such as Figure 8 When the pressure holding time is 20 minutes, the water holding capacity increases significantly. Continuously increasing the pressure time causes the muscle to absorb water and swell, and the salt-soluble protein dissolves, promoting protein denaturation. The muscle absorbs water and swells, which is manifested as an increase in the gaps between closely arranged myofibrils, resulting in a decrease in water holding capacity.

[0067] The salt-soluble protein content first increases and then decreases with the increase of holding time, such as Fig. 9 As shown. At 20 minutes, the salt-soluble protein content reached a maximum value of 37.48 mg / 100 g, which was significantly different from the control group. When the holding time was 50 minutes, the salt-soluble protein content decreased significantly, which may be due to the promotion of high pressure on endogenous enzymes, causing most salt-soluble proteins to be hydrolyzed into small molecules, thereby reducing the content. When the holding time was less than 50 minutes, the salt-soluble protein content was not significantly different from that of the control group, indicating that while ultra-high pressure can improve the pickling effect, the holding time cannot be too long, otherwise it will affect the nutritional components of the ham.

[0068] The pH changes of ham during the curing period under different holding times are as follows: Fig.10 As shown in the figure, the pH has a clear upward trend with the increase of holding time. The pH increases significantly due to the long holding time. This may be because some proteins are denatured or unfolded under the long-term ultra-high pressure treatment, which causes the partial fragmentation of cells in the muscle and exposes some basic amino acid groups. In addition, the exposed basic groups react with acidic groups or acidic substances, causing the pH to rise.

[0069] The change of chromaticity with holding time is shown in Table 2. As the holding time increases, the L* value of the product shows a downward trend, and the a* value shows a trend of first increasing and then decreasing. The main reason for the color change of meat is the change in the proportion of myoglobin pigment. The reaction of myoglobin and oxygen will generate bright red oxymyoglobin or brown metmyoglobin, and the appropriate holding time will activate the metmyoglobin reductase system, so that the brown metmyoglobin is reduced to bright red oxymyoglobin. However, when the holding time is too long, the protein will coagulate, myoglobin will be over-oxidized, and the meat color will darken.

[0070] Table 2 Effect of holding time on chromaticity of ham during pickling period

[0071]

[0072] Combining the results of single factor experiments A and B, the best treatment condition for ham is: maintaining pressure at 200 MPa for 20 minutes. Subsequent measurements were performed on the samples under this treatment condition.

[0073] C: Effect of optimal ultrahigh pressure treatment conditions on the microstructure of ham muscle during the curing period

[0074] The results showed that the MASSON staining images showed the internal muscle structure of the hams in the control group and the 200MPa ultrahigh pressure treatment group. Under a 40x microscope, the collagen fibers in the muscle were blue, and the muscle fibers, cellulose and red blood cells were red. Fig.11 As shown in a and b. After ultrahigh pressure treatment, myofibrils are broken and the ultrastructure of muscles changes significantly. Under a 200x microscope, the interstitial space inside the tissue increases and the fibers swell. Fig.11 c and d, which may help the diffusion process. It can be seen that ultra-high pressure treatment changes the internal structure of muscle fiber tissue. Compared with the control group, as the interstitial space increases, sodium chloride enters the muscle tissue more quickly and diffuses, which can better explain the increase in sodium chloride content in ham.

[0075] SEM-EDX analysis showed the dispersion of sodium chloride in the control group and the 200MPa ultrahigh pressure treatment group ( Fig.12 ), yellow dots represent Na + , red dots indicate Cl - Compared with untreated meat, the Na + and Cl - In the traditional process, the diffusion and balance of sodium chloride in the whole muscle are slow. Ultra-high pressure treatment can significantly promote the penetration and absorption of sodium chloride in meat, making it more evenly distributed. This further proves that ultra-high pressure has the ability to accelerate mass transfer during the curing process, improve the curing effect of dry-cured ham, and shorten the curing time.

[0076] D: Effects of optimal ultrahigh pressure processing conditions on quality indicators of mature ham

[0077] The results showed that the determination of sodium chloride content in dry-cured ham during fermentation was as follows: Fig.13 On the 12th day of fermentation, the sodium chloride content in the ultra-high pressure treatment-assisted pickling group was almost the same as that in the control group at maturity, indicating that ultra-high pressure can shorten the fermentation time of dry-cured ham by nearly 1 / 3.

[0078] The results of the determination of volatile compounds are shown in Tables 3 and 4. In the control group, 6 ketones, 9 aldehydes, 15 hydrocarbons, 7 carboxylic acids and their derivatives, 7 alcohols, 1 ether and other compounds were detected; in the HHP group, 2 ketones, 9 aldehydes, 31 hydrocarbons, 13 carboxylic acids and their derivatives, 7 alcohols, 1 ether and other compounds were detected. According to the relative content of each substance, the main compounds in the ham under different treatments were aldehydes and hydrocarbons, followed by esters, acids, alcohols, and ketones.

[0079] Table 3 Volatile compounds identified in the control group

[0080]

[0081]

[0082] Table 4 Volatile compounds identified in the UHP group

[0083]

[0084]

[0085] Aldehyde compounds are key VOCs with high content and low odor threshold. In this experiment, hexanal, valeraldehyde, heptanal, etc. were separated from different treated hams, and the content was very high, accounting for 77.71% in the control group and 70.39% in the ultra-high pressure assisted curing group, indicating that straight-chain aldehydes contribute more to the flavor of dry-cured ham. The generation of straight-chain aldehydes is closely related to the autoxidation of lipids. Hexanal, valeraldehyde and heptanal are the most abundant in this study, and the odor characteristics are grassy, ​​malty and oily. Branched-chain aldehydes and aromatic aldehydes are mainly derived from the Strecker degradation of amino acids. In this study, a total of one branched-chain aldehyde (3-methylbutanal) was identified. 3-methylbutanal is related to nutty and acorn flavors and is the most abundant flavor substance in mature Iberian ham. No corruption-characteristic flavor substances were detected. Hydrocarbon compounds are widely present in dry-cured hams, mainly formed by lipid oxidation, but have a high threshold and contribute less to the overall aroma of dry-cured ham.

[0086] Ester compounds are formed by the esterification reaction of carboxylic acids and alcohols. In this study, there were large differences among the different treatment groups. A total of 4 types were detected in the control group and 8 types were detected in the HHP group. The common substances were ethyl hexanoate, isoamyl acetate and isobutyl butyrate, which have a fruity aroma.

[0087] Acid compounds are important volatile components in dry-cured ham, which may come from the oxidative degradation of glycerol and phospholipids, Maillard reaction or high-temperature oxidation of aldehydes. In this study, the acid content detected in the control group accounted for 1.63% of the total ham flavor content, and the acid content detected in the ultra-high pressure assisted curing group accounted for 2.9% of the total ham flavor content. Short-chain acids play an important role in aroma development due to their low olfactory threshold, such as acetic acid, butyric acid, caproic acid, etc. Caproic acid accounts for a high proportion in different processed hams, and has a sour cheese flavor.

[0088] The formation of alcohols is closely related to lipid oxidation, amino acid metabolism, methyl ketone reduction and microbial reproduction. Most compounds in alcohols have high thresholds and low content in ham, so their contribution to the flavor of ham is limited. In this study, a total of 7 alcohols were identified. The most abundant alcohol in different treatment groups was amyl alcohol, followed by 1-octen-3-ol. 1-octen-3-ol mainly comes from microbial activity and is considered to be an important VOCs. It is formed by the oxidation of arachidonic acid and has a typical mushroom flavor. It has been listed as the main flavor substance of ham in many studies and contributes to the sensory characteristics of dry-cured ham.

[0089] Ketones usually have special aromas, such as fruity, spicy, fatty and cooked meat, and also contribute to the flavor composition of traditional ham. In this experiment, more ketones were identified in the control group ham, including 2-heptanone, sec-octanone, 5-methyl-3-heptanone, 3-octen-2-one, 3-methyl-2-heptanone, and 3-hydroxy-2-butanone. The content of sec-octanone was relatively high, and it had a mushroom-like aroma. Only two ketones, 2-heptanone and sec-octanone, were identified in the ultra-high pressure assisted pickling group. The content of 2-heptanone was relatively high, and it had a fruity aroma similar to pears.

[0090] The results of free amino acid determination are shown in Table 5. There is no difference in the types of free amino acids in the control group and the ultra-high pressure treatment group, but the content of each free amino acid in the samples treated with ultra-high pressure increases to varying degrees, and the average total content increases from 920.1ug / g to 1092.71ug / g. On the one hand, the free amino acids in meat are decomposed into aldehydes, ketones, esters and pyrazines through Maillard reaction and Strecker degradation during fermentation to enhance the aroma of ham. On the other hand, they have salty, sweet and sour tastes to enhance the taste of ham. For example, the umami amino acids glutamine and asparagine increased by 34.57ug / g and 5.95ug / g respectively after ultra-high pressure treatment. Studies have shown that arginine and lysine contribute to the presentation of bacon flavor. In this experiment, the contents of the two amino acids increased by 30.34ug / g and 42.88ug / g respectively after ultra-high pressure treatment.

[0091] Table 5 Types and contents of free amino acids in mature ham (ug / g)

[0092]

[0093]

[0094] The method of the invention is a novel and efficient method. The optimal process conditions for improving the pickling effect of ham are screened out through single factor experiments, and the influence of ultra-high pressure treatment on the quality of mature ham is explored, which provides a certain reference for shortening the pickling time of dry-cured ham.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention.

Claims

1. A method for curing dry-cured ham using an ultrahigh pressure assisted method, characterized in that: The method steps are: Step 1) Clean the fresh pork hind leg meat to remove blood and fat, fascia, cut into pieces and precool at 4℃ for 24 hours; Step 2) Use sea salt to marinate, apply salt once every day for 3 times in total, sprinkle salt evenly on the surface, and place in a 4℃ refrigerator after completion; Step 3) placing the meat pieces in step 2) in a vacuum sealed bag, vacuum-packing and then ultra-high pressure, and treating under ultra-high pressure for a certain period of time; Step 4) Hang the ultra-high pressure treated meat in a room at 10-15°C and 75%-80% relative humidity for 21 days, then transfer it to a constant temperature and humidity chamber at 20-22°C and 65%-70% relative humidity until the meat is fully fermented.

2. The method for curing dry-cured ham using ultrahigh pressure assisted method according to claim 1, characterized in that: In the step 2), the first amount of salt applied is 4% of the mass of the ham, and the second and third amounts of salt applied are 2% of the mass of the ham. The pickling time after each salting is 7 days.

3. The method for curing dry-cured ham using an ultra-high pressure assisted method according to claim 1 or 2, characterized in that: The processing pressure of step 3) is 100-500 MPa, and the pressure holding time is 10-50 min.

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