CN110146401B - Method for testing water content in frozen milk dessert - Google Patents
Method for testing water content in frozen milk dessert Download PDFInfo
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- CN110146401B CN110146401B CN201810138410.0A CN201810138410A CN110146401B CN 110146401 B CN110146401 B CN 110146401B CN 201810138410 A CN201810138410 A CN 201810138410A CN 110146401 B CN110146401 B CN 110146401B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
- G01N5/04—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by removing a component, e.g. by evaporation, and weighing the remainder
- G01N5/045—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by removing a component, e.g. by evaporation, and weighing the remainder for determining moisture content
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Abstract
The invention relates to a method for testing water content in frozen milk dessert, which comprises the following steps: s1, sample preservation: storing a plurality of samples under the conditions that the temperature is-3 to-5 ℃ and the humidity is 40 to 50 percent; s2, sample detection: placing the sample in a moisture detector for detection, carrying out constant weight weighing at intervals of 2-5 ℃ within a heating range, and calculating the water loss rate Ax, wherein x represents different temperatures; s3, auxiliary detection: putting the sample in a thermogravimetric analyzer for analysis to obtain a curve of temperature to weight change, and calculating the water loss rate By, wherein y represents different temperatures; s4, alignment: comparing the detected data with the auxiliary detected data, and selecting the average value of the data in the range as the finally detected water content when the data error between the detected data and the auxiliary detected data is less than or equal to 5%. The method for detecting the water content of the frozen milk dessert has the characteristic of reducing the detection error of the water content of the frozen milk dessert.
Description
Technical Field
The invention relates to the field of water content detection, in particular to a method for testing water content in frozen milk dessert.
Background
Moisture content is an important detection index for frozen food, affecting the transportation and storage period of the food. Commonly used moisture detection methods include: direct drying, reduced pressure drying, and distillation. The direct drying method is that the weight loss of the sample after drying is measured by adopting a volatilization method at the temperature of 101-105 ℃ under 101.3kPa, and the weighing calculation is carried out after the sample is constant in weight. Drying under reduced pressure by heating to 60 + -5 deg.C under 40-53kPa, and removing water from the sample by drying under reduced pressure. And (3) distilling the water in the sample together with toluene or xylene by a distillation method, and calculating the volume of the distilled water.
Distillation is not suitable for the detection of water content in frozen milk desserts due to the inclusion of fat in such products. The direct drying method and the reduced pressure drying method have long detection time and are not suitable for online detection. Infrared heating is generally used to increase the rate of water evaporation. However, in the actual operation process, the temperature of infrared heating is not easy to control, and other dry matters are also included in the frozen milk dessert, so that the dry matters are easy to lose due to carbonization in the heating process, and the measurement is inaccurate.
Disclosure of Invention
The invention aims to provide a method for testing the water content in a frozen milk dessert, which has the characteristic of reducing the detection error of the water content in the frozen milk dessert.
The technical purpose of the invention is realized by the following technical scheme: a method for testing the water content of a frozen milk dessert comprises the following steps:
s1, sample preservation: storing a plurality of samples under the conditions that the temperature is-3 to-5 ℃ and the humidity is 40 to 50 percent;
s2, sample detection: placing the sample in a moisture detector for detection, carrying out constant weight weighing at intervals of 2-5 ℃ within a heating range, and calculating the water loss rate Ax, wherein x represents different temperatures;
s3, auxiliary detection: putting the sample in a thermogravimetric analyzer for analysis to obtain a curve of temperature to weight change, and calculating the water loss rate By, wherein y represents different temperatures;
s4, alignment: and comparing the data of the moisture detector with the data of the thermogravimetric analyzer, and when the data error of the moisture detector and the data of the thermogravimetric analyzer is less than or equal to 5%, the average value of a plurality of data of the moisture detector in the measured temperature range is the finally measured water content.
By adopting the technical scheme, the sample is preserved at low temperature in advance, and the water in the sample is kept in a stable state so as to avoid increasing errors caused by the influence of the external environment. And dividing the sample into two parts, wherein one part is placed in a moisture detector to detect the water loss rate, and the other part is placed in a thermogravimetric analyzer to detect the weight loss curve of the sample.
The sample is put into a moisture detector to remove the moisture in the sample in a heating and evaporating manner, and the sample can sequentially undergo the processes of free water evaporation, combined water evaporation and partial dry matter carbonization and water loss in the heating and evaporating process. In actual detection, the water loss rate of free water or the water loss rate of combined water is only required to be detected, and the two times of dehydration cannot be accurately tested only by adopting a moisture detector. When the moisture detector is used for testing a sample, a plurality of groups of data are tested at intervals so as to be convenient for comparing the data with the data obtained by auxiliary detection.
In the application, a thermogravimetric analyzer is adopted for auxiliary detection, and when a sample is placed into the thermogravimetric analyzer, the water loss rate in three stages can be obviously observed from a curve of temperature to weight change. And comparing the two groups of data to distinguish the water loss rate of the free water, the water loss rate of the combined water and the water loss rate of the dry matter carbonization, wherein the sum of the water loss rates of the free water and the combined water is the water content of the sample. Although the moisture detector and the thermogravimetric analyzer are conventional devices, no technology for detecting the water content by combining the moisture detector and the thermogravimetric analyzer exists at present.
Further, when the sample is stored, a blank sample is set, and sample detection and auxiliary detection are simultaneously carried out on the blank sample.
By adopting the technical scheme, when the sample is stored under the condition of low temperature, more frost can be formed on the surface of the sample if the storage time is too long, so that the test is inaccurate. When the sample is preserved, a plastic block with the same volume size as the sample is placed as a blank sample.
Further, when the sample is stored, the periphery of the sample is wrapped with a layer of oil absorption paper.
By adopting the technical scheme, the oil absorption paper is wrapped outside the sample, so that the accumulation of frost on the surface of the sample is further reduced.
Further, during the sample detection process, the sample is heated at a temperature of between 100 ℃ and 120 ℃.
By adopting the technical scheme, the sample is heated in the temperature range, free water and bound water in the sample can be removed, and other dry substances in the sample cannot be carbonized.
Further, in the sample detection process, the heating speed of the sample is 1-3 ℃/min.
By adopting the technical scheme, the heating speed of the sample is kept to be 1-3 ℃/min in the heating interval of 100-120 ℃, so that the measured data in the sample detection process is more stable.
Further, the sample during the auxiliary detection is heated between 80-500 ℃.
By adopting the technical scheme, the heating interval selected by auxiliary detection is larger, the heating interval of the sample is enlarged, and free water, bound water and water evaporated by carbonization of part of dry substances in the sample can be detected in the heating process. The auxiliary detection has wider data range, and can accurately verify the water loss rate of free water and combined water in the sample detection process.
Further, in the auxiliary detection process, the heating rate of the sample is 1-5 ℃/min.
By adopting the technical scheme, in the auxiliary detection process, the heating is carried out within the heating rate range, so that the finally measured data is more stable.
In conclusion, the invention has the following beneficial effects:
1. according to the invention, the moisture detector and the thermogravimetric analyzer are adopted for comparative test, the thermogravimetric analyzer enlarges the heating range of the sample, and can verify the data measured by the moisture detector, so that the free water content and the bound water content in the sample can be more accurately measured;
2. the sample is preserved at low temperature in advance, so that the water in the sample is kept stable; in addition, an oil absorption paper layer is wrapped on the periphery of the sample in advance, so that the extra frost accumulated on the surface of the sample in the preservation process is reduced.
Detailed Description
The present invention will be described in further detail with reference to examples.
The first embodiment is as follows: a method for testing the water content of a frozen milk dessert comprises the following steps:
s1, sample preservation: storing 10 ice cream samples (hereinafter referred to as samples) with the volume of 5cm by 2cm at the temperature of-3 ℃ and the humidity of 40%, and selecting 10 polypropylene plastic blocks with the volume of 5cm by 2cm as blank samples; wrapping a layer of oil absorption paper on the periphery of the sample and the blank sample in advance;
s2, sample detection: 5 samples and 5 blank samples were selected and the oil absorbing paper was removed. The water loss rate of the 5 samples and the 5 blank samples was measured sequentially by a moisture meter (in this example, a MA35 infrared moisture meter was selected). Setting the heating temperature of the moisture detector between 100 and 120 ℃, setting the heating rate of the sample to be 1 ℃/min, and recording the water loss rate of the sample to be Ax (x represents different temperatures) every 2 ℃ in the heating process;
s3, auxiliary detection: 5 samples and 5 blank samples were selected and the oil absorbing paper was removed. And sequentially detecting the water loss rate of the sample by using a thermogravimetric analyzer for 5 samples and 5 blank samples. Setting the heating temperature of a thermogravimetric analyzer to be 80-500 ℃, setting the heating rate of the sample to be 2 ℃/min, finally obtaining a weight change curve of the temperature to the sample, and calculating the water loss rate By (y represents different temperatures) of the sample according to the curve;
s4, alignment: comparing the water loss ratio Ax (blank deduction) of the water content detector with the water loss ratio By (blank deduction) of the thermogravimetric analyzer, and respectively making curves of Ax and By for the temperature. And selecting the position with the same trend in the two curves, selecting data with an error value less than or equal to 5% in the data corresponding to the two curves, and averaging the data of the moisture detector in the range to obtain the water content of the final product.
The difference between the other embodiments and the first embodiment is the process parameters, which are specifically shown in table 1.
TABLE 1 Process parameters corresponding to the examples
The water content of the samples was measured by the methods of the above examples, and the specific test data are shown in table 2.
TABLE 2 results of measuring the water content of the samples using the above examples
Comparative example
Comparative example one: a method of testing the water content of a frozen milk dessert, the comparative example differing from the first example in that: the samples were not cryogenically preserved.
Comparative example two: a method of testing the water content of a frozen milk dessert, the comparative example differing from the first example in that: the sample was oven dried and tested for weight loss ratio Ax (x represents different temperatures).
The above comparative moisture test data is shown in table 3.
Table 3 comparative water content test data
From the above data, it can be seen that if the sample is not stored at low temperature, the water content in the sample is unstable, and the deviation of the water content detected by the moisture detector and the thermogravimetric analyzer is large. Furthermore, if the sample is heated by an oven and operated according to GB5009.3-2010, it may absorb part of the water when cooled at constant temperature, resulting in a large deviation of the measured result from the water content measured by the thermogravimetric analyzer.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Claims (2)
1. A method for testing the water content in frozen milk dessert is characterized in that: the method comprises the following steps:
s1, sample preservation: storing a plurality of samples under the conditions that the temperature is-3 to-5 ℃ and the humidity is 40 to 50 percent;
s2, sample detection: placing the sample in a moisture detector for detection, carrying out constant weight weighing at intervals of 2-5 ℃ within a heating range, and calculating the water loss rate Ax, wherein x represents different temperatures;
s3, auxiliary detection: putting the sample in a thermogravimetric analyzer for analysis to obtain a curve of temperature to weight change, and calculating the water loss rate By, wherein y represents different temperatures;
s4, alignment: comparing the data of the moisture detector with the data of the thermogravimetric analyzer, and when the data error between the data of the moisture detector and the data of the thermogravimetric analyzer is less than or equal to 5%, the average value of a plurality of data of the moisture detector in the measured temperature range is the finally measured water content;
in the sample detection process, the sample is heated at the temperature of between 100 ℃ and 120 ℃;
in the sample detection process, the heating speed of the sample is 1-3 ℃/min;
heating the sample at 80-500 deg.C during auxiliary detection;
in the auxiliary detection process, the heating rate of the sample is 1-5 ℃/min;
when the sample is stored, the periphery of the sample is wrapped with a layer of oil absorption paper.
2. The method of testing the water content of a frozen milk dessert as claimed in claim 1, wherein: and when the sample is stored, setting a blank sample, and simultaneously carrying out sample detection and auxiliary detection on the blank sample.
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| CN103743646A (en) * | 2014-01-13 | 2014-04-23 | 广东中烟工业有限责任公司 | Measurement method for content of moisture in tobacco and tobacco product |
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| JP3022259B2 (en) * | 1995-06-30 | 2000-03-15 | 不二製油株式会社 | Oily composition and frozen food |
| JP3521059B2 (en) * | 1998-11-05 | 2004-04-19 | 株式会社大林組 | Method and apparatus for measuring water content of fresh concrete |
| CN2549459Y (en) * | 2002-06-19 | 2003-05-07 | 吉林中谷科技工程有限公司 | Infrared electronic water content test device |
| CN101539523B (en) * | 2009-05-07 | 2012-05-02 | 内蒙古蒙牛乳业（集团）股份有限公司 | Method for detecting content of trace elements in cheese |
| CN103063822A (en) * | 2012-12-26 | 2013-04-24 | 合肥立华畜禽有限公司 | Grease water rapid detection method |
| CN104297096B (en) * | 2014-09-26 | 2016-09-28 | 西南石油大学 | A kind of quantitative determine the method that clay combines water content |
| CN104535451A (en) * | 2014-12-31 | 2015-04-22 | 长沙开元仪器股份有限公司 | Automatic moisture detector |
| CN104655519B (en) * | 2015-02-12 | 2017-08-25 | 北京市农林科学院 | A kind of free water content assay method |
| CN105571981B (en) * | 2015-12-23 | 2018-09-25 | 常州广建仪器科技有限公司 | A kind of determination of moisture device and method |
| CN105758684A (en) * | 2016-03-17 | 2016-07-13 | 贵州安达科技能源股份有限公司 | Preparation method of moisture test sample and test method |
| CN106959256A (en) * | 2017-05-19 | 2017-07-18 | 四川莱源科技有限公司 | The moisture detecting method of accuracy of detection can be improved |
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