CN102519829A - Test method for determining beer foam stability - Google Patents

Abstract

The present invention provides a kind of test method that is used to measure the stability of beer foam, comprising steps: S1, bubbling into CO _Gas foaming: S2, monitoring and recording of the defoaming process; S3, calculating the size of the foam stability; according to the second order The law of gradual change of the derivative, the defoaming curve t-lnV is divided into three sections, and the slope of the middle section is calculated. The smaller the absolute value of the slope, the better the stability. In the present invention, since each parameter is controllable, the defoaming characteristics of the foam produced under different parameter combinations can be studied. Compared with hand-pour foaming, the foam formed by the device has significantly improved reproducibility of foam shape and defoaming process. The invention is used to study the dynamic defoaming process of beer foam, evaluate the stability of beer foam, the collection of foam active substances and their relationship with foam stability, etc., and has the characteristics of simplicity, applicability, accuracy, low cost and easy operation .

Description

A test method for determining the stability of beer foam

technical field

The invention relates to the technical field of measuring beer foam, in particular to a test method for measuring the stability of beer foam.

Background technique

Foam is a typical feature that distinguishes beer from other alcoholic beverages. It is also an important evaluation index of beer quality and an important characteristic that determines consumers' willingness to purchase. Structurally, the foam is composed of a gas phase, a liquid phase, and a surface-active component that stabilizes the foam. In the traditional beer foam detection method, the gas phase required for foam formation is provided by the CO ₂ carried by the beer itself. During the foaming process, the CO ₂ of the beer itself is released under external force (dumping) or decompression, and at the same time, the inherent surface active components of the beer itself (such as protein, α-acid) dissociate to the surface of the gas phase and consolidate into the bubble wall , to stabilize the foam in the wine body (liquid phase) and delay its defoaming process. The generation and disappearance of beer foam are the two main processes involved in the detection of beer foam. The traditional beer foam detection method (stopwatch method) uses hand pouring to pour the foam, and defoams naturally in an open room temperature environment, and records the foam retention time. In this measurement method, uneven foaming strength, injection speed, fluctuations in room temperature and observation of the ^0.05cm2 exposed wine surface will reduce the repeatability and reliability of the results, so the accidental error is relatively large. In addition, because the traditional beer foam stability detection method relies on the CO ₂ carried by the beer itself, the foam shape and foaming amount are subject to the CO ₂ content of the beer and cannot be adjusted; and the CO ₂ content of the same batch of beer Inhomogeneity directly leads to a reduction in the repeatability of the method. More importantly, too much CO ₂ will cover the contribution of surface active components in the wine body to the soaking time. The characteristics and functions of the foam surface active ingredients are often the special attention and understanding of the beer foam stability research. Therefore, to develop a beer foam stability measurement device and method that can exclude the influence of the wine body's own _CO2 and ambient temperature fluctuations, high repeatability and reliability, for the evaluation of beer foam stability, process monitoring and foam active substances It is of great significance to research and guide industrial practice.

At present, the test devices and methods used for beer foam evaluation at home and abroad mainly include the following types:

1. Stopwatch method. As shown in FIG. 1 , the test device mainly includes an iron frame platform 101 , an iron frame ring 102 , a foam cup 103 , and a stopwatch 104 .

The foam cup has an inner diameter of 60mm and a height of 120mm. The iron frame ring is fixed at a distance of 1cm from the edge of the foam cup. the

When measuring, quickly place the mouth of the newly opened beer bottle (can) on the iron ring 12, and pour the beer into the cup at a uniform flow rate along the center line of the cup (as shown in the figure) until the foam height is equal to the mouth of the cup. . Simultaneously start counting by the stopwatch, when the liquid surface is exposed to 0.05cm ² , the counting is terminated, and the recorded time is the soaking time. The longer the time, the better the stability of the foam.

2. Sigma method. As shown in FIG. 2 , the test device mainly includes a sigma special foam funnel 201 , a measuring cylinder 202 and a stopwatch 203 . Sigma special foam funnel comes with a volume scale line of 800mL. When measuring, close the outlet valve of the funnel tightly, and immediately inject the beer liquid along the center line of the funnel at a constant speed after the beer is opened until the foam reaches the 800ml mark, and the timing starts. After 30 seconds, open the sampling valve to release the liquid and keep the foam. Reset the stopwatch to zero. After 200 seconds, open the sampling valve to separate the defoaming liquid into a 100ML graduated cylinder. When the foam just flows out, turn off the switch, stop the watch, and record the time t and volume b. Finally, add 3ml of alcohol to the remaining foam in the funnel to defoam, so that all the foam becomes liquid, measure the total liquid volume with a measuring cylinder, and record the volume c (minus 3ml from the total liquid volume). Calculate the sigma value according to the following formula:

The larger the calculated sigma value, the better the foam stability.

3. NIBEM method. As shown in FIG. 3 , the test device mainly includes a gas dispersion head 301 , a compression rod 302 , a foam cup 303 , a CO2 supply source 304 , and a NIBEM measuring instrument 305 . During measurement, first use the compression rod 302 to penetrate the gas dispersion head 301 into the beer bottle (can) cover, insert it into the wine liquid, and let CO ₂ bubble. Collect the foam in the foam cup until it is flush with the rim. Then, put the foam cup full of foam into the NIBEM measuring instrument 305. The special probe will track the descending process of the upper foam level. Time as the infusion of beer. The longer the time, the better the foam stability.

4. Rudin's improved method. As shown in Figure 4, the test device mainly includes a foaming tube 401, a _CO2 supply source 402, a gas flow meter 403, and a constant temperature water bath 404. When measuring, first introduce the constant temperature beer at the bottom of the foaming tube, adjust the liquid level to the 100mL mark, and release the excess wine sample from the side arm C. Then, slowly pass _CO2 at a constant speed to turn the beer into foam as much as possible, and stop aerating when the foam rises to the 350mL mark, so the foam begins to collapse, and the liquor rises in the thin tube. Measure the time interval between the two markings (50mL and 75mL) on the thin tube, the longer the time, the more stable the foam.

The common disadvantage of the above devices and methods is that the dynamic monitoring of the whole process of foam defoaming cannot be realized. The four devices and measurement methods all use cumulative quantities (such as total defoaming time) to describe and evaluate the dynamic process of defoaming, so it may cover up many differences in the process, and it is difficult to accurately clarify the relationship between foam active ingredients and foam characteristics . Both the first two test devices use hand pouring to foam, and factors such as foaming strength, injection speed, and room temperature fluctuations are uncontrollable, resulting in large accidental errors and reduced reliability of the method. Although devices 3 and 4 have been improved to replace pouring foaming with bubbling foaming, they are still defoaming in a natural environment, and fluctuations in environmental factors such as temperature have not been eliminated. It can be seen that none of the four devices have a constant temperature control on the defoaming environment, and environmental fluctuations directly lead to a decrease in the reliability of the measurement method. And the device 3 does not pre-constant temperature the blown CO ₂ compressed gas, resulting in supercooled CO ₂ gas directly into the wine to foam, so that the subsequent foam collapse process is greatly affected by temperature fluctuations. Therefore, providing a test device and method that can accurately reveal the dynamic defoaming process of beer foam is an urgent problem to be solved in the evaluation of beer foam and the in-depth study of related theories.

Contents of the invention

Aiming at the deficiencies of existing test devices for measuring foam stability, the purpose of the invention is to propose a simple, applicable, accurate and easy-to-operate test method for measuring beer foam stability. The specific technical scheme is as follows.

A kind of test method for measuring beer foam stability, comprises the following steps:

(1) Blowing CO ₂ gas into bubbles:

(1.1) Adjust the low temperature thermostat to stabilize the temperature at the set value of 15~65°C;

(1.2) Slowly pour the degassed beer to be tested into the foam thermostat, and pre-constant for 15-30 minutes;

(1.3) Lead _CO2 from the gas pipeline to the gas dispersion head, adjust the pressure reducing valve and the rotary valve of the rotameter, and control the gas flow rate to 0.05~0.12L/h;

(1.4) Lower the gas dispersing head to a fixed position at the bottom of the foam thermostat, immerse the gas dispersing head in the wine body, and start the bubbling timer;

(1.5) Pull the gas dispersion head away from the wine liquid and bubble layer, stop the bubbling timer, and control the bubbling time at the set value of 2~15s;

(2) Monitoring and recording of defoaming process:

(2.1) The defoaming process is a process in which the upper bubble level continues to decrease and the lower bubble level continues to rise. Whenever the lower bubble level rises to a full scale line, record the current moment: from this, the entire dynamics of the lower bubble level over time can be obtained process;

(2.2) Calculate the foam equivalent volume V corresponding to each time t, and draw the defoaming curve t-lnV that reflects the entire defoaming dynamic process. The formula for calculating the foam equivalent volume is as follows:

V=V ₀ -V′

V ₀ ——Initial liquor volume mL

V'——the volume represented by the lower bubble level corresponding to each time point;

(3) Calculation of foam stability

According to the law of gradual change of the second order derivative, the defoaming curve t-lnV is segmented, and the slope of the second segment is calculated. The smaller the absolute value of the slope, the better the beer foam stability.

In the above-mentioned test method for determining the stability of beer foam, between steps (1.2) and (1.3), it also includes adjusting the tightness gear of the gas dispersion head to adjust the diameter of the generated foam and control the fineness of the foam.

In the above test method for measuring the stability of beer foam, the gas pipeline bypasses the pulley fixed vertically above the foam thermostat, and can move up and down along the center line of the foam thermostat.

In the above-mentioned test method for measuring the stability of beer foam, the foam thermostat is a cylindrical glass vessel; the end of the foam thermostat is provided with a sampling port for collecting defoaming liquid, and the sampling port is sealed by a cock; It is marked with a uniform volume scale line, and with the record of the moment when the lower foam level rises to each volume scale line, the monitoring of the foam volume change during the entire defoaming process is realized.

Compared with the prior art, the present invention has the following advantages and technical effects:

(1) The computer can be used to quickly and accurately record the entire defoaming process, and can be segmented according to the characteristics of the defoaming curve, which significantly improves the degree of automation and data processing capabilities.

(2) It can be used to study the foam characteristics of surface active ingredients, the dynamic process of defoaming, and the comparison of the stability of different beer foams. It is simple, applicable, accurate, and easy to operate.

(3) In the present invention, the foam thermostat is a straight cylindrical glass vessel, and its inner diameter can be designed according to the standard foam cup, which can ensure the foam defoaming phenomenon in the measuring device and the defoaming phenomenon in the foam cup in the actual consumption process resemblance. The foam thermostat is equipped with dense volume scale lines, and with the recording of the moment when the lower bubble level rises to each volume scale line, it can record the change of foam equivalent volume during the entire defoaming process. Through the description of the entire defoaming dynamic process, the purpose of comprehensively evaluating foam characteristics based on dynamic parameters is realized.

(4) The gas dispersing head is an adjustable gas dispersing head. By tightening or loosening the gas dispersing head, the diameter of the generated foam can be adjusted, that is, the fineness of the foam.

(5) The initial liquor volume, air velocity, aeration time, and foam size are all adjustable parameters, which can be adjusted separately to observe the influence of different test parameters on the foam characteristics.

(6) With the help of this measuring device, many human and environmental interference problems caused by hand-poured foaming and natural defoaming are solved, and the reproducibility of the defoaming process and the reliability of the detection method are significantly improved.

(7) Before aeration, the degassed liquor to be tested can be pre-injected into the foam thermostat to keep the temperature. By adopting the method of enclosing _CO2 gas to seal the constant temperature, the oxidation of the wine to be tested can be avoided while realizing the constant temperature of the wine to be tested.

Description of drawings

Figures 1 to 4 are structural schematic diagrams of several existing test devices for measuring foam stability.

Fig. 5 is a schematic structural diagram of an embodiment of the present invention.

FIG. 6 is an enlarged schematic view of the structure of the gas dispersion head 508 in FIG. 5 .

Fig. 7 is a typical defoaming curve of beer foam measured by the device of the present invention.

Detailed ways

The implementation of the present invention will be further described below in conjunction with the accompanying drawings and examples, but the implementation of the present invention is not limited thereto.

As shown in Figure 5, it is a test device for realizing the method of the present invention, which is made according to the specific needs of the test on the basis of synthesizing the above four existing test devices.

A test device for measuring the stability of beer foam, including a foam thermostat 505, a gas dispersing head 508, a constant temperature device (502, 503), a pulley block 501, and a _CO2 gas cylinder 506. The foam thermostat 505 is a cylindrical glass vessel , the side wall of the cylindrical glass vessel is provided with a water bath interlayer; the constant temperature device is composed of a low temperature constant temperature box 502 and a temperature exchanger 503; each component is distributed and connected according to the gas pipeline and constant temperature water circulation path of the system; wherein, the CO ₂ gas The outlet end of the bottle is connected to the gas inlet end of the temperature exchanger 503 after passing through the pressure reducing valve 507 and the rotameter 504; In the foam thermostat 505, the end of the silicone tube is connected with a gas dispersion head 508; the cooling circulating water outlet of the cryogenic thermostat 502 is connected with the water inlet of the temperature exchanger 503, and the water outlet of the temperature exchanger 503 is interlayered with the foam thermostat 505 water bath the water outlet of the water bath interlayer of the foam thermostat 505 is connected to the low-temperature thermostat 502, forming a constant-temperature cooling loop of circulating water in the system, and realizing the constant temperature of the entire system.

The inner diameter of the foam thermostat 505 is consistent with the inner diameter of the foam cup required by the national standard (GB 4928-91); the side wall of the foam thermostat 505 is marked with dense and uniform volume scale lines; the lower end of the foam thermostat 505 is equipped with a , The sampling port for collecting the defoaming liquid.

Gas dispersing head 508, as shown in Figure 6, is made of two plastic hemispheres and the porous sponge sandwiched between the two plastic hemispheres, about 1cm in diameter; Tighten or loosen the distance between the two plastic hemispheres to adjust the diameter of the sponge channel, thereby adjusting and controlling the fineness of the foam, that is, the size of the foam. According to the size of the foam, the gas dispersion head is divided into several gears.

The constant temperature device is composed of a low temperature constant temperature box 502 and a temperature exchanger 503, wherein the low temperature constant temperature box 502 is a constant temperature box with an external circulation function and a refrigerator, which provides constant temperature cooling circulating water for the whole system. The temperature exchanger 503 is a serpentine condenser tube, the tube side is a gas path, and the shell side is cooling circulating water. When the _CO2 gas flows through the snake tube, it exchanges heat with the constant temperature cooling circulating water to realize the constant temperature of the gas.

The gas dispersing head 508 realizes up and down reciprocating movement between the starting point at the set position directly above the foam thermostat 505 and the lower point immersed in the beer with the set depth through the pulley block.

The pressure reducing valve 507 and the rotameter 504 are connected in series in the gas path, which can realize the adjustment of the flow rate of CO ₂ .

In the above device, the low-temperature constant-temperature circulating water flowing out of the low-temperature constant-temperature water bath 502 flows through the interlayer of the foam thermostat and the temperature exchanger 503 to keep the temperature of the entire system. Finally, the foam is subjected to constant temperature defoaming in the foam thermostat 505 .

The role of each component is further explained:

(1) CO ₂ gas, provided by the CO ₂ cylinder, flows through the pressure reducing valve and rotameter into the foam instrument;

(2) The foam meter is a straight cylindrical glass vessel with a water bath interlayer and a volume scale, and its inner diameter is consistent with the standard foam cup. There is a sampling port at the end of the foam meter, which is similar in structure to the separating cock at the lower end of the separating funnel.

(3) Low temperature constant temperature device. Since temperature has a great influence on the defoaming process, a low-temperature constant temperature water bath with external circulation is used to control the system temperature, and the difference in defoaming conditions at different temperatures can be studied.

(4) Temperature exchanger. The structure is similar to the coil type condenser. The supercooled compressed gas is exchanged with the flowing low-temperature circulating water in the temperature exchanger and then passed into the foam instrument after heat exchange and constant temperature, which avoids the temperature fluctuation of the system that may be caused by the supercooled compressed gas directly blowing into the wine body.

(5) Gas dispersion head. Connected to the end of the gas pipeline to refine the foam. By adjusting different gears, the difference in defoaming conditions of foams of different sizes can be measured.

(6) Pulley blocks. It is fixed vertically above the center line of the foam instrument, and the gas pipeline bypasses the pulley block and leads into the foam instrument. The gas dispersing head can be lifted vertically along the centerline of the foam. When the gas dispersing head rises vertically and breaks away from the wine body and bubble layer, the bubbling ends.

Example 1

1.1 Test purpose: evaluation of beer foam dynamic defoaming process

1.2 Test principle: The defoaming process is a process in which the upper bubble level keeps decreasing and the lower bubble level keeps rising. Record the time it takes for the bubble level to rise by one volume scale, and then continue to calculate the foam equivalent volume corresponding to each moment point, and observe the dynamic change of the foam volume over time. The fluctuation of foam volume and defoaming rate during the defoaming process can be obtained by the matching defoaming curve analysis software.

1.3 The test steps are as follows:

1.3.1 Bubble CO ₂ gas:

(1) Adjust the low temperature and constant temperature water bath to stabilize the temperature at the set value of 15~65°C;

(2) Slowly pour the degassed beer to be tested into the foam thermostat, and pre-constant for 15-30 minutes;

(3) Adjust the sandhead gear to the preset value (1~7 gears are available);

(4) Open the main valve of the gas cylinder, adjust the pressure reducing valve and the rotary valve of the rotameter, and control the gas flow rate at the set value of 0.05~0.12L/h;

(5) Lower the gas dispersing head to a fixed position at the bottom of the foam thermostat, immerse the gas dispersing head in the wine body, and start the bubbling timer;

(6) After a certain period of time, pull the gas dispersion head away from the wine liquid and bubble layer, stop the bubbling timer, and control the bubbling time at the set value of 2~15s;

1.3.2 Monitoring and recording of defoaming process

(1) The defoaming process is a process in which the upper bubble level keeps decreasing and the lower bubble level keeps rising. Whenever the lower bubble level rises to a full scale line, record the current moment. From this, the whole dynamic process of the bubble level changing with time can be obtained;

(2) Calculate the foam equivalent volume V corresponding to each time t, draw the defoaming curve t-lnV reflecting the entire defoaming dynamic process, and calculate the foam equivalent volume as follows;

V=V ₀ -V′

V ₀ ——Initial liquor volume mL

V'——the volume represented by the lower bubble level corresponding to each time point

It can be seen from Figure 7 that the complete defoaming process of beer foam is a typical three-segment curve, representing the leachate stage, the defoaming stage of foaming substances, and the defoaming stage of stable substances respectively. The parameters of the defoaming curve can comprehensively reflect the foam stability of beer, such as: time T ₁ of leaching—the speed of leaching; defoaming slope k ₂ of foaming substances—the retention properties of foaming substances in beer; Total foam substance content V ₁ ——total foam substance content in beer; stable substance defoaming slope k ₃ ——foam retention property of stable substance in beer; stable substance content V ₂ , ratio of stable substance to total foam substance V ₂ / V ₁ - the amount of stable substances in beer.

Example 2

2.1 Purpose of the test: Evaluation of foam stability of different brands of beer

2.2 Experimental principle: The defoaming curve of beer foam is a typical three-segment curve, and the slope of the fitting line of the second segment curve can reflect the foam retention of foaming substances in beer, and it can be compared with the foam retention time measured by the stopwatch method. There is a significant correlation, so the slope of the second section of the defoaming curve can be used to characterize the size of the foam stability.

2.3 The test steps are as follows:

2.3.1 Bubble CO ₂ gas:

(1) Adjust the low temperature and constant temperature water bath to stabilize the temperature at the set value of 15~65°C;

(2) Slowly pour the degassed beer to be tested into the foam thermostat, and pre-constant for 15-30 minutes;

(3) Adjust the sandhead gear to the preset value (1~7 gears are available);

(4) Open the main valve of the gas cylinder, adjust the pressure reducing valve and the rotary valve of the rotameter, and control the gas flow rate at the set value (0.05~0.12L/h);

(5) Lower the gas dispersing head to a fixed position at the bottom of the foam thermostat, immerse the gas dispersing head in the wine body, and start the bubbling timer;

(6) After a certain period of time, pull the gas dispersion head away from the wine liquid and bubble layer, stop the bubbling timer, and control the bubbling time at the set value of 2~15s;

2.3.2 Monitoring and recording of defoaming process

(1) The defoaming process is a process in which the upper bubble level keeps decreasing and the lower bubble level keeps rising. Whenever the lower bubble level rises to a full scale line, record the current moment. From this, the whole dynamic process of the bubble level changing with time can be obtained;

(2) Calculate the foam equivalent volume V corresponding to each time t, draw the defoaming curve t-lnV reflecting the entire defoaming dynamic process, and calculate the foam equivalent volume as follows;

V=V ₀ -V′

V ₀ ——Initial liquor volume mL

V'——the volume represented by the lower bubble level corresponding to each time point

2.3.3 Calculation of foam stability

According to the law of gradual change of the second order derivative, the defoaming curve t-lnV is divided into sections, and the slope of the second section is calculated. The smaller the absolute value of the slope, the better the stability. Table 1 shows the soaking time of different beers, the slope of each segment of the defoaming curve and the correlation coefficient between them.

Table 1

beer samples Soaking time (s) 1 segment slope 2 slopes 3 slopes sample 1 194 -1.9993 -0.7751 -0.2177 sample 2 236 -1.3491 -0.6065 -0.2749 sample 3 246 -1.4398 -0.5843 -0.3074 Sample 4 263 -0.9704 -0.5617 NO Sample 5 264 -1.3517 -0.5284 -0.1921 The correlation coefficient between the slope of each segment and the soaking time the 0.903* 0.984** 0.064

From the results in Table 1, it can be seen that the slopes of the first and second sections of the defoaming curve are significantly related to the foam retention, especially the slope of the second section, that is, the defoaming rate of the foaming material in the defoaming stage, is the same as that measured by the stopwatch method. There is a high correlation between foam stability (r=0.984, p < 0.01), so it can be used to characterize the size of foam stability. The smaller the absolute value of the slope, the better the stability of the beer foam. Therefore, by the present invention, the foam stability of finished beer, the foam stability of fermented liquid and the foam retention characteristic of foam formation of foam surface active ingredient can be accurately measured, thereby guide industrial practice, and for further exploring foam surface active ingredient The mechanism of action has laid the foundation.

Claims (4)

1. a test method for measuring beer foam stability is characterized in that comprising the following steps: (1) Blowing CO ₂ gas into bubbles: (1.1) Adjust the low temperature thermostat to stabilize the temperature at the set value of 15~65°C; (1.2) Slowly pour the degassed beer to be tested into the foam thermostat, and pre-constant for 15-30 minutes; (1.3) Lead _CO2 from the gas pipeline to the gas dispersion head, adjust the pressure reducing valve and the rotameter rotary valve, and control the gas flow rate to 0.05~0.12L/h; (1.4) Lower the gas dispersing head to a fixed position at the bottom of the foam thermostat, immerse the gas dispersing head in the wine body, and start the bubbling timer; (1.5) Pull the gas dispersion head away from the wine liquid and bubble layer, stop the bubbling timer, and control the bubbling time at the set value of 2~15s; (2) Monitoring and recording of defoaming process: (2.1) The defoaming process is a process in which the upper bubble level continues to decrease and the lower bubble level continues to rise. Whenever the lower bubble level rises to a full scale line, record the current moment: from this, the entire dynamics of the lower bubble level over time can be obtained process; (2.2) Calculate the foam equivalent volume V corresponding to each time t, and draw the defoaming curve t-lnV that reflects the entire defoaming dynamic process. The formula for calculating the foam equivalent volume is as follows: V=V ₀ -V′ V ₀ ——Initial liquor volume mL V'——the volume represented by the lower bubble level corresponding to each time point; (3) Calculation of foam stability According to the law of gradual change of the second order derivative, the defoaming curve t-lnV is segmented, and the slope of the second segment is calculated. The smaller the absolute value of the slope, the better the beer foam stability. 2. The test method for determining the stability of beer foam according to claim 1, characterized in that steps (1.2) and (1.3) also include adjusting the tightness of the gas dispersion head to adjust the diameter of the foam produced Size, to control the fineness of the foam. 3. the test method for measuring beer foam stability according to claim 1, characterized in that the gas pipeline bypasses the pulley fixed on the vertical top of the foam thermostat, and can be displaced up and down along the centerline of the foam thermostat . 4. the test method for measuring beer foam stability according to claim 1 is characterized in that described foam thermostat is a cylindrical glass vessel; the end of foam thermostat has a sampling port for collecting defoaming liquid, sampling The mouth is sealed by a cock; the foam thermostat is marked with a uniform volume scale line, and with the record of the moment when the lower bubble level rises to each volume scale line, the monitoring of the foam volume change during the entire defoaming process is realized.

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