Disclosure of Invention
In view of the above problems in the prior art, the applicant of the present invention provides a simple method for rapidly determining the activity of enzymes in grains and predicting the proper temperature of enzymes. The invention uses Rapid Visco Analyser (RVA) as analysis means, the instrument is mainly used for measuring enzyme activity to judge wheat bud damage, the instrument is widely applied to the research of viscosity characteristics of starch and derivatives thereof in later period, and the instrument not only has good comparability with the test result of a falling number instrument, but also has good relativity with the application of grains in different systems. The instrument is simple to operate, the determination process is short, the sample consumption is less, the temperature multi-section type accurate control can be realized, and a good foundation is laid for the enzyme activity determination and the enzyme temperature suitability prediction.
The technical scheme of the invention is as follows:
the method takes the viscosity drop degree, namely the relative value of the peak viscosity reduction, of the heating gelatinization of the grains before and after enzyme deactivation as parameters for representing the enzyme activity and the enzyme suitable temperature, wherein the larger the parameter is, the higher the enzyme activity is; the enzyme activity refers to the general name of the enzyme which has the effect of reducing the viscosity of each component in the grains; the enzymatic optimum temperature refers to the temperature causing the maximum degree of viscosity reduction in the grains; the components comprise at least one of starch, protein, fat and polysaccharide, especially starch.
In one embodiment of the invention, the enzyme having a viscosity-lowering effect on each component comprises at least one of amylase, pectinase, cellulase, protease, lipase.
In one embodiment of the invention, the enzyme activity refers to the general term of the degree of viscosity reduction of the grains during storage; the enzymatic optimum temperature refers to the temperature at which the greatest reduction in viscosity occurs during storage.
In one embodiment of the present invention, the enzyme activity refers to a generic term of enzymes that cause a decrease in the viscosity of barley when the barley is transformed into a malt state; the enzymatic optimum temperature is the temperature at which barley sprouts with malt viscosity that decreases most significantly.
In one embodiment of the present invention, the enzyme activity refers to a generic term of enzymes that cause a decrease in viscosity of rice flour when the rice is soaked to a state for preparing rice flour; the proper temperature of the enzyme is the temperature at which the enzyme plays the greatest degradation role in the rice soaking process.
In one embodiment of the invention, the enzyme activity refers to the general term of enzyme that causes viscosity reduction of wheat flour during processing of wheat into wheat products; the enzymatic thermophilic temperature refers to the temperature required for the maximum degree of viscosity of enzymatically degraded wheat flour in wheat flour.
In one embodiment of the invention, the method comprises the steps of: (1) measuring the moisture content of the grain sample, and converting the dry basis of the sample; (2) measuring the corresponding viscosity increase values of the grain samples at 30-100 ℃ before and after enzyme deactivation by taking the water content obtained in the step (1) as a reference; (3) calculating enzyme activity by finding peak viscosity change degree in the viscosity change process, and (4) calculating enzyme adaptive temperature by the peak viscosity change degree in different temperature sections.
In one embodiment of the present invention, the method comprises the following specific steps:
(1) pretreatment: grinding the grain sample, and sieving with a 100-mesh sieve;
(2) measuring the moisture content of the sample, and weighing 3-5g of a dry base sample on the basis of taking 14% as moisture;
(3) set enzyme activity measuring program and optimum temperature measuring program
(4) 25g of deionized water was weighed and mixed with the sample as a control. At the same time, 25g of the enzyme inhibitor solution was weighed and mixed with the powder as a measurement sample. Placing the sample in a Rapid Viscometry Analyzer (RVA) to determine a viscosity profile;
(5) calculating to obtain peak viscosity, disintegration value, final viscosity, retrogradation value, peak time, paste forming temperature and area according to RVA characteristic spectrogram by referring to the method in AACC22-08 standard; wherein the enzyme activity, i.e. (P), is calculated from the peak viscosity increase of the test sample relative to the control sampleTesting-PControl)×100/PControlWherein P represents the peak viscosity;
(6) and calculating the optimal temperature of the enzyme according to the area in the RVA characteristic spectrum, namely taking the temperature corresponding to the maximum increase value of the area formed by the characteristic curve as the optimal temperature.
In one embodiment of the present invention, the procedure for measuring the enzyme activity is as follows:
procedure 1: keeping the temperature at 60 ℃ for 1min, increasing the speed of 12 ℃/min to 95 ℃ and keeping the temperature for 2.5min, then reducing the speed to 50 ℃ at the same speed and keeping the temperature for 1.4min, and keeping the stirring speed at 160 r/min;
procedure 2: keeping the temperature at 60 ℃ for 5min, increasing the speed of 12 ℃/min to 95 ℃ for 5min, then reducing the speed to 50 ℃ at the same speed, keeping the temperature for 3min, and keeping the stirring speed at 160 r/min;
wherein, the procedure 1 is suitable for the determination of the enzyme activity in the starch extract; procedure 2 is applicable to the determination of enzyme activity in whole grain flour.
In one embodiment of the present invention, the procedure for determining the optimum temperature is: setting different heat preservation time, preserving heat for 5min at 30-90 ℃, increasing to 95 ℃ at the speed of 12 ℃/min, keeping for 2.5min, reducing to 50 ℃ at the same speed, preserving heat for 1.4min, and keeping the stirring speed at 160 r/min.
In one embodiment of the present invention, the cereal species in step (1) comprises: rice, wheat, corn, buckwheat, oat, quinoa and starch extracts of rice, wheat, corn, buckwheat, oat, quinoa.
In one embodiment of the present invention, the weight of the starch extract sample in step (2) is 3-4g, while the weight of the whole grain flour sample is 4-5g, and the same mass (dry basis) of the same comparative sample is weighed as a control.
In one embodiment of the present invention, the enzyme inhibitor in step (4) includes, but is not limited to: a compound containing carbon-phosphorus bonds, a phosphoric acid derivative containing organic groups, one or a mixture of more of silver nitrate, copper sulfate, copper chloride and ferric sulfate.
In one embodiment of the present invention, the concentration of the enzyme inhibitor in step (4) is controlled to be 0.01 to 2 mM.
The invention also provides the application of the method in the aspects of grain quality control, storage, breeding, fermentation and judgment of varieties and production places.
The beneficial technical effects of the invention are as follows: the invention provides a novel method for measuring the activity and the enzyme adaptive temperature of enzyme contained in grains, which can measure the activity and the enzyme adaptive temperature of the enzyme in the grains while researching the gelatinization characteristics of the grains. Compared with a falling numerical instrument, the method can determine the enzyme activity of the total enzyme in the grains, can know the optimal temperature of the enzyme through the comparison of different temperatures, further knows the quality of the grains, is favorable for improving the efficiency of grain quality analysis, is favorable for improving the operability of quality determination, avoids the waste of manpower and material resources, and provides theoretical guidance for grain processing, storage and application.
Detailed Description
Example 1
A simple method for rapidly determining enzyme activity in grains and predicting enzyme adaptive temperature is characterized by comprising the following specific steps of:
(1) rice pretreatment: extracting rice starch with starch content of 95%, and sieving with 100 mesh sieve.
(2) The moisture content of the sample was measured, and 3g of the dry sample was weighed based on 14% moisture.
(3) The specific procedure is as follows: keeping the temperature at 60 ℃ for 1min, increasing the speed of 12 ℃/min to 95 ℃ and keeping the temperature for 2.5min, then reducing the speed to 50 ℃ at the same speed and keeping the temperature for 1.4min, and keeping the stirring speed at 160 r/min.
(4) 25g of deionized water was weighed and mixed with the sample as a control. At the same time, 25g of the enzyme inhibitor solution was weighed and mixed with the powder as a measurement sample. The samples were placed in a rapid visco-analyzer (RVA) to determine the viscosity profile.
(5) According to the RVA profile, the peak viscosity, disintegration value, final viscosity, retrogradation value, peak time, paste forming temperature and area were calculated with reference to the method described in AACC22-08 standard. Wherein the enzyme activity, i.e. (P), is calculated from the peak viscosity increase of the test sample relative to the control sampleTesting-PControl)×100/PControlWherein P represents the peak viscosity.
As shown in FIG. 1, the peak viscosity of the rice starch after enzyme deactivation is obviously increased, namely the rice starch has higher enzyme activity, the peak viscosity is increased from 6500cp to 7579cp, and the calculated enzyme activity is 16, 6.
Example 2
A simple method for rapidly determining enzyme activity in grains and predicting enzyme adaptive temperature is characterized by comprising the following specific steps of:
(1) pretreatment: grinding the rice sample into powder and sieving the powder with a 100-mesh sieve.
(2) The moisture content of the sample was measured, and 4g of a dry sample was weighed based on 14% moisture.
(3) The specific procedure is as follows: setting different heat preservation time, preserving heat for 5min at 30-90 ℃, increasing to 95 ℃ at the speed of 12 ℃/min, keeping for 2.5min, reducing to 50 ℃ at the same speed, preserving heat for 1.4min, and keeping the stirring speed at 160 r/min.
(4) 25g of deionized water was weighed and mixed with the sample as a control. At the same time, 25g of the enzyme inhibitor solution was weighed and mixed with the powder as a measurement sample. The samples were placed in a rapid visco-analyzer (RVA) to determine the viscosity profile.
(5) The optimum temperature of the enzyme is calculated according to the viscosity reduction degree in the RVA characteristic spectrum, namely the temperature corresponding to the temperature with the most obvious viscosity reduction trend (the maximum value of the increase of the area formed by the characteristic curve) is the optimum temperature.
As shown in FIG. 2, the difference between the peak viscosity and the peak viscosity before and after enzyme deactivation is different at different temperatures, and it can be seen from the figure that the optimum temperature of the enzyme in the rice flour is 60-70 ℃.
As shown in FIG. 3, the hardness of rice was most remarkably decreased at the optimum temperature for the action of enzyme (from 30499g to 11210g) and not remarkably decreased at a lower temperature such as 30 ℃ such as from 32174g to 25524g, as measured by a rice hardness measuring method (Tri-point measuring method, TA.XT-Plus, P/36 probe) proposed by the Japanese Okabe schooler and widely used internationally, depending on the soaking temperature and time, it was found that the optimum temperature measuring method proposed by the present invention can be applied to guide the processing control of rice.
Example 3
A simple method for rapidly determining enzyme activity in grains and predicting enzyme adaptive temperature is characterized by comprising the following specific steps of:
(1) pretreatment: the corn samples were ground and sieved through a 100 mesh sieve.
(2) The moisture content of the sample was measured, and 5g of the dry sample was weighed based on 14% moisture.
(3) The specific procedure is as follows:
keeping the temperature at 60 ℃ for 5min, increasing the speed of 12 ℃/min to 95 ℃ for 5min, then reducing the speed to 50 ℃ at the same speed, keeping the temperature for 3min, and keeping the stirring speed at 160 r/min.
(4) 25g of deionized water was weighed and mixed with the sample as a control. At the same time, 25g of the enzyme inhibitor solution was weighed and mixed with the powder as a measurement sample. The samples were placed in a rapid visco-analyzer (RVA) to determine the viscosity profile.
(5) According to the RVA characteristic spectrum, the peak viscosity, the disintegration value, the final viscosity, the retrogradation value, the peak time, the paste forming temperature and the area are calculated by referring to the method in AACC22-08 standard. Wherein the enzyme activity, i.e. (P), is calculated from the peak viscosity increase of the test sample relative to the control sampleTesting-PControl)×100/PControlWherein P represents the peak viscosity.
The result is shown in fig. 4, the peak viscosity of the inactivated corn flour is also significantly increased, that is, the corn flour has higher enzyme activity, the viscosity is increased from 1450cp to 1679cp after the enzyme is inactivated, and the calculated enzyme activity is 15.8.
Example 4
A simple method for rapidly determining enzyme activity in grains and predicting enzyme adaptive temperature is characterized by comprising the following specific steps of:
(1) pretreatment: and grinding the wheat sample, and sieving the ground wheat sample with a 100-mesh sieve.
(2) The moisture content of the sample was measured, and 5g of the dry sample was weighed based on 14% moisture.
(3) The specific procedure is as follows: keeping the temperature at 60 ℃ for 1min, increasing the speed of 12 ℃/min to 95 ℃ and keeping the temperature for 2.5min, then reducing the speed to 50 ℃ at the same speed and keeping the temperature for 1.4min, and keeping the stirring speed at 160 r/min.
(4) 25g of deionized water was weighed and mixed with the sample as a control. At the same time, 25g of the enzyme inhibitor solution was weighed and mixed with the powder as a measurement sample. The samples were placed in a rapid visco-analyzer (RVA) to determine the viscosity profile.
(5) According to the RVA characteristic spectrum, the peak viscosity, the disintegration value, the final viscosity, the retrogradation value, the peak time, the paste forming temperature and the area can be obtained. Wherein the enzyme activity, i.e. (P), is calculated from the peak viscosity increase of the test sample relative to the control sampleTesting-PControl)×100/PControlWherein P represents the peak viscosity.
As shown in fig. 5, the peak viscosity of the wheat flour after enzyme deactivation is also significantly increased, that is, the wheat flour has higher enzyme activity, the viscosity after enzyme deactivation is increased from 2616cp to 3158cp, and the calculated enzyme activity is 20.7.
Example 5
A simple method for rapidly determining enzyme activity in grains and predicting enzyme adaptive temperature is characterized by comprising the following specific steps of:
(1) pretreatment: grinding barley samples before and after germination, and sieving with a 100-mesh sieve.
(2) The moisture content of the sample was measured, and 4g of a dry sample was weighed based on 14% moisture.
(3) Keeping the temperature at 60 ℃ for 5min, increasing the speed of 12 ℃/min to 95 ℃ for 5min, then reducing the speed to 50 ℃ at the same speed, keeping the temperature for 3min, and keeping the stirring speed at 160 r/min.
(4) 25g of deionized water was weighed and mixed with the sample as a control. At the same time, 25g of the enzyme inhibitor solution was weighed and mixed with the powder as a measurement sample. The samples were placed in a rapid visco-analyzer (RVA) to determine the viscosity profile.
(5) Calculating to obtain peak viscosity, disintegration value, final viscosity, retrogradation value, peak time, paste forming temperature and viscosity according to RVA characteristic spectrogram by referring to the method described in AACC22-08 standardArea. Wherein the enzyme activity, i.e. (P), is calculated from the peak viscosity increase of the test sample relative to the control sampleTesting-PControl)×100/PControlWherein P represents the peak viscosity.
As a result, as shown in FIG. 6, the viscosity of barley before and after germination was changed from 2140cp to 1603cp, and the enzyme activity was calculated to be 33.4.
Example 6
A simple method for rapidly determining enzyme activity in grains and predicting enzyme adaptive temperature is characterized by comprising the following specific steps of:
(1) pretreatment: collecting 1 wheat flour germinated in rainy season and 2 normal mature wheat flours, wherein the wheat flour is high gluten flour (protein content is more than 12%);
(2) the moisture content of the sample was measured, and 5g of the dry sample was weighed based on 14% moisture.
(3) The specific procedure is as follows: keeping the temperature at 60 ℃ for 1min, increasing the speed of 12 ℃/min to 95 ℃ and keeping the temperature for 2.5min, then reducing the speed to 50 ℃ at the same speed and keeping the temperature for 1.4min, and keeping the stirring speed at 160 r/min.
(4) 25g of deionized water was weighed and mixed with the sample as a control. At the same time, 25g of the enzyme inhibitor solution was weighed and mixed with the powder as a measurement sample. The samples were placed in a rapid visco-analyzer (RVA) to determine the viscosity profile.
(5) According to the RVA characteristic spectrum, the peak viscosity, the disintegration value, the final viscosity, the retrogradation value, the peak time, the paste forming temperature and the area are calculated by referring to the method in AACC22-08 standard. Wherein the enzyme activity, i.e. (P), is calculated from the peak viscosity increase of the test sample relative to the control sampleTesting-PControl)×100/PControlWherein P represents the peak viscosity.
(6) The falling number of 3 kinds of flour is measured according to the method of GB/T10361-2008, the viscoenzyme activity is measured according to the method of the invention, meanwhile, three kinds of flour are used to make soft bread under the same operation environment and operation steps, the volume of the bread is measured according to the method of GB/T20981-2007, and the bread formula is as follows: 100% of flour, 2% of yeast, 10% of sugar, 1% of salt, 6% of oil and 57% of water.
Detecting the falling value of the wheat flour by adopting a falling value instrument, wherein the detection steps are as follows:
(1) measuring the moisture content of the flour, correcting by using a sample amount of 7g with 15 percent of moisture content, and weighing a sample according to the measured moisture content;
(2) opening the falling numerical value tester, and heating the water bath until the water bath is boiled;
(3) transferring the weighed flour sample into a dry and clean viscosity tube, adding 25ml of water by using an automatic liquid adding device, and uniformly vibrating;
(4) and (3) putting the viscosity tube into a boiling water bath, starting stirring, automatically completing the test by an instrument, and recording the time displayed on an electronic timer to be the falling number.
Table 1 is a table comparing the falling number, the viscoenzyme activity and the bread specific ratio determined in the examples, where the falling number is inversely proportional to the enzyme activity of the noodles or the bread, i.e., the higher the enzyme activity, the lower the falling number, and the direct ratio of the viscoenzyme activity to the actual enzyme activity. As can be seen from the table, the trend of the enzyme activity measured by the invention is completely consistent with the trend measured by the falling number value. Generally, the bread specific volume is about 4.8, the bread quality is better (less than or equal to 7), and the bread is too big and not good when too small. As can be seen from the table, the enzyme activity is closely related to the specific volume, the specific volume of the bread can be predicted by measuring the appropriate enzyme activity (the fall number is 250 +/-9.2, and the viscoenzyme activity is 20.6 +/-0.2), and then the bread flour is guided to produce and process, and meanwhile, the enzyme activity error limit measured by the method is reduced by 10 times.
Table 1 falling number instrument compared to the effect of the method used in the present invention on bread specific volume.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.