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Method for moisture,total polyphenols and caffeine in tea polyphenol products -– Near infrared reflectance spectroscopy
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Basic data
| Standard ID | GH/T 1259-2019 (GH/T1259-2019) |
| Description (Translated English) | Method for moisture,total polyphenols and caffeine in tea polyphenol products -�C Near infrared reflectance spectroscopy |
| Sector / Industry | Supply and Marketing Cooperatives Industry Standard (Recommended) |
| Classification of Chinese Standard | X55 |
| Date of Issue | 2019-05-21 |
| Date of Implementation | 2019-12-01 |
| Regulation (derived from) | Industry Standards Record Announcement No.2 of 2019 (Total No.230) |
| Issuing agency(ies) | All-China Federation of Supply and Marketing Cooperatives |
GHT1259-2019: Method for moisture,total polyphenols and caffeine in tea polyphenol products -– Near infrared reflectance spectroscopy
---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
(Determination of Moisture, Tea Polyphenols and Caffeine in Tea Polyphenols by Near Infrared Spectroscopy)
GH
People's Republic of China Supply and Marketing Cooperation Industry Standard
ICS 67.140.10
X 55
2010- ××-×× Release
1.1.1.1.2010-06-01 Implementation
Published by the Ministry of Health of the People's Republic of China
Published by All China Supply and Marketing Cooperative
2019-5-21 released
2019-12-01 Implementation
Content of water, tea polyphenols and caffeine in tea polyphenol products
Near infrared spectroscopy
Method for moisture, total polyphenols and caffeine in tea polyphenol
products--Near infrared reflectance spectroscopy
Foreword
This standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This standard was proposed by the All-China Supply and Marketing Cooperative.
This standard is under the jurisdiction of the National Tea Standardization Technical Committee.
This standard was drafted. China National Supply and Marketing Cooperative Hangzhou Tea Research Institute, Hangzhou Spectrum Education Technology Development Co., Ltd., Lake
Zhou Rongkai Plant Extraction Co., Ltd., Jiangsu Dehe Biotechnology Co., Ltd., Zhejiang Tea Group Co., Ltd.
The main drafters of this standard. Wang Jing, Yang Xiufang, Kong Junhao, Cao Houjian, Tu Yunfei, Zuo Xiaobo, Tan Rong, Gao Yuping, Gao
Yue, Mao Limin, Liu Jianhong, Zhou Xinqi, Zheng Qiwei.
The content of water, tea polyphenols and caffeine in tea polyphenol products
Near infrared spectrometry
1 Scope
This standard specifies the principles and terminology for rapid determination of moisture, tea polyphenols, and caffeine content in tea polyphenol products by near-infrared spectroscopy.
And definitions, instrumentation, calibration model verification and evaluation, measurement, result processing and representation, confirmation and processing of abnormal samples, etc.
This standard is applicable to the rapid determination of moisture, tea polyphenols, and caffeine content in tea polyphenol products by near-infrared spectrometer.
This standard does not apply to arbitration inspections.
2 Normative references
The following documents are essential for the application of this document. For dated references, only the dated version applies to this
file. For undated references, the latest version (including all amendments) applies to this document.
GB/T 18798.1-2017 Sampling of solid instant tea
GB/T 31740.2 Tea products. Part 2. Tea polyphenols
GB/T 31740.2-2015 Tea polyphenol content detection method
GB/T 31740.2-2015 Test methods for catechins and caffeine content
GB/T 31740.22015 Test method for moisture content
3 Principle
The near-infrared spectrum is generated when the molecular vibration transitions from the ground state to a high energy level due to the non-harmonicity of the molecular vibration.
Frequency doubling and combined frequency absorption bands of the hydrogen-containing group XH (X = C, N, O, etc.) vibration. Using near-infrared spectroscopy with chemometrics
The method can realize the rapid detection of tea polyphenol products by using near-infrared spectroscopy.
4 Terms and definitions
The following terms and definitions apply to this document.
4.1
Calibration model
Mathematical model between the near-infrared spectrum of the sample and the corresponding chemical standard value established by the chemometric method.
4.2
Sample set
A representative collection of samples that substantially covers the range of related component content.
4.3
Calibration samples
Sample set created by the reference calibration model.
4.4
Check samples
Sample set used to verify the accuracy and repeatability of NIR model measurements. Verify that the sample set does not participate in the establishment of the calibration model.
4.5
Monitor samples
A homogeneous sample of the same variety for monitoring the daily working stability of a near-infrared analyzer.
4.6
Abnormal samples
Samples with outliers. Outliers are measured values of samples that are far away from other measured values.
The samples used vary widely.
4.7
Calibration model validation
The process of verifying the accuracy and repeatability of a calibration model using a validation sample set.
4.8
Standard error of prediction corrected for bias (SEP)
After the model is established, the residual value between the near-infrared method measurement value obtained after the prediction set is subtracted from the national standard method measurement value and the system standard deviation
The standard deviation is directly related to the accuracy of the near-infrared model. The smaller the SEP, the higher the model accuracy. SEP
Equation (1) is calculated.
(1)
In the formula.
-Verify the near-infrared measurement of the component of sample i
-Verify the component standard values for sample i
n--number of samples;
Bias-system deviation, and the sum of the deviations divided by the number of samples. Where is the near-infrared component of the verification sample i
The difference between the measured value and the standard value, ie.
5 instruments
5.1 Near-infrared spectrometer
Diffuse reflection type near-infrared spectrometer with continuous scanning monochromator or other products, light source is 10W tungsten halogen lamp, scanning range is
1000-1800nm, resolution 10 nm, wavelength accuracy 0.2 nm, wavelength repeatability ± 0.05 nm.
5.2 Software
Use the analysis software that comes with the near-infrared instrument in 5.1.
5.3 Sample dish
Use the sample dish provided with the near-infrared instrument in 5.1.
6 Determination
6.1 Preparation before measurement
6.1.1 The collection of samples shall be performed in accordance with the provisions of GB/T 18798.1-2017
6.1.2 According to the instructions of the near-infrared spectrometer (5.1), the instrument is preheated and self-tested.
6.1.3 In the use state, use the monitoring sample to detect the near-infrared spectrometer (5.1) at least once a day. Monitor sample preparation
Follow the rules in Appendix B.
6.1.4 The temperature of the test sample shall be consistent with the temperature during the measurement of the calibration model sample.
6.2 Determination of samples
According to the instructions of the near-infrared spectrometer (5.1), take an appropriate amount of tea polyphenols for measurement with a near-infrared spectrometer.
Record the measurement data. Each sample was measured in triplicate.
7 Calibration model verification and evaluation
7.1 Basic requirements for verification
7.1.1 In one of the following cases, the existing calibration model of the near-infrared analyzer needs to be verified.
a) When the calibration model is used for the first time, or after the calibration model is updated, or when the instrument is replaced;
b) when the source of the sample changes significantly;
c) After the instrument is repaired or the light source is replaced;
d) when other verification is needed;
e) Verification shall be performed at least twice a year.
7.1.2 For different models of near-infrared analyzers, the calibration model shall be verified using a verification sample set with the same variability. Calibrated
See Appendix A for general rules and procedures.
7.1.3 The content of the measured component in the verification sample should be within the range of the component content in the calibration model, covering the range as much as possible, and showing a more uniform
Uniform distribution, meet the requirements of Appendix A.
7.1.4 The standard values of the sample components are measured and statistically determined in accordance with GB/T 31740.2-2015 Appendix A, B and C. Sample components
Chemical analysis should be performed at the same time as near-infrared measurement.
7.1.5 The physical characteristics such as the particle size of the sample should be consistent with the sample used in the calibration model.
7.1.6 The temperature range during the verification test shall be consistent with the temperature range specified by the calibration model.
7.1.7 The calibration model verification results obtained using the verification samples are only applicable to the range covered by the verification samples.
7.2 Verification content and evaluation
7.2.1 Accuracy Evaluation
The verification sample set is used to verify the accuracy of the calibration model. The verified calibration standard deviation (SEP) should meet the requirements in Table 1. Correct
If it fails to meet the requirements and fails to pass the verification, the cause shall be found out and verification shall be carried out again until it meets the requirements.
7.2.2 Repeatability evaluation
The verification sample set was used for repeatability verification of the calibration model. Randomly select 3 verification samples, measure 10 times each, each sample
The repeatability (sr) of the measurement results shall meet the requirements of Table 1. For those that do not meet the requirements and cannot pass the verification, the cause should be investigated.
New verification until required.
Table 1 Basic requirements for calibration model evaluation
Component calibration standard deviation (SEP) /% ≤ Repeatability (sr) /% ≤
Moisture 0.30 0.10
Tea Polyphenols 1.50 0.40
Caffeine 0.50 0.10
8 Results processing and representation
8.1 The relative deviation of the three measurement results shall meet the requirements of Table 2. Take the arithmetic mean of the three data as the measurement result, and determine the result.
The result is one digit after the decimal point.
Table 2 Allowable errors of analysis
Relative deviation between component parallel samples is less than /%
Moisture 2.5
Tea Polyphenols 4.0
Caffeine 5.0
8.2 For abnormal measurement results reported by the instrument, the obtained data should not be used as valid measurement data. Confirmation and treatment of abnormal samples
The requirements of Chapter 9 are implemented.
9 Confirmation and treatment of abnormal samples
9.1 Confirmation of abnormal samples
9.1.1 The reasons for the abnormal measurement results may come from the following aspects.
-The content of water, tea polyphenols or caffeine in the sample exceeds the range of the calibration model of the instrument;
-The wrong calibration model is used;
-Excessive impurities in the sample;
-The sample shifted during the spectral scanning process;
--The temperature difference between the sample temperature and the calibration model sample is too large.
9.1.2 The cause of abnormal measurement results should be analyzed and eliminated, and the second near-infrared measurement should be performed.
Alarm, it is confirmed as an abnormal sample.
9.2 Treatment of abnormal samples
The moisture, tea polyphenol and caffeine content of the abnormal samples should be determined according to the methods specified in GB/T 31740.2-2015 Appendix A, B and C.
Line determination.
Appendix A
(Normative appendix)
Calibration rules and procedures
A.1 Selection of samples
The participating tea polyphenol samples should be representative and should cover the characteristics of the samples to be analyzed. Creating a new calibration model requires
Collect more than 120 samples, 20 of which were used as verification samples and the rest as calibration samples.
A.2 Determination of physical and chemical components of the sample
The moisture content of tea polyphenol products is determined according to the method specified in Appendix C of GB/T 31740.2-2015.
The content of tea polyphenols in tea polyphenol products was measured according to the method specified in Appendix A of GB/T 31740.2-2015.
The content of caffeine in tea polyphenol products was determined according to the method specified in Appendix B of GB/T 31740.2-2015.
A.3 Data processing methods
Use the software that comes with the near-infrared instrument.
A.3.1 Model optimization
According to the model evaluation index, the model is further optimized by changing the modeling method, modeling band, and preprocessing method
And the number of principal components to get a more reasonable model.
A.3.2 External verification
The established model should be evaluated by external data.
Appendix B
(Normative appendix)
Monitor sample preparation
B.1 Instrument
The near-infrared analyzer meets the requirements of 5.1 of this standard.
B.2 Preparation of monitoring samples
B.2.1 Sampling
The collected tea polyphenol samples shall meet the quality indicators of the products in GB/T 31740.2-2015, and shall be taken in accordance with GB/T 18798.1-2017
kind. 150 grams per sample.
B.2.2 Determination of samples
The near-infrared analyzer (5.1) was used to determine the caffeine content in tea polyphenol products.
B.2.3 Four samples shall be prepared for monitoring. Three of them are reserved.
B.3 Preservation of monitored samples
The samples should be sealed, protected from light, and stored in a temperature below -18 ° C. Shelf life is 18 months.
B.4 Service life of monitored samples
When the monitored samples appear wet, contaminated, or exceed the storage period, the samples should be changed or re-prepared.
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