Testing the moisture content of foods based on automated testing equipment
Abstract: The traditional drying method requires a tedious drying-cooling-weighing process to measure the moisture content of the food, while the automatic and efficient C830 migration and non-volatiles analyzer can simultaneously perform the drying and weighing operations automatically. , reducing cooling and frequent constant weight links. In this paper, the traditional direct drying method and the new C830 were used to test the moisture in bread, biscuit and wheat flour samples, and the test results of the two methods were analyzed and compared to verify the stability and reliability of the new testing equipment.
Keywords: moisture, food, drying, weighing, migration and non-volatiles, bread
Moisture is one of the must-test items for most food quality control. It is closely related to the color, taste, processing, preservation, microbial growth and biochemical reaction of food. It is also an important economic indicator. According to the provisions of GB 5009.3-2016 "Food Safety National Standards for Determination of Moisture in Foods", the test methods for moisture in foods include direct drying method, vacuum drying method, distillation method and Karl Fischer method. The scope of application is not the same, and the direct drying method has a wide range of applications.
The traditional direct drying method requires three equipments: oven, dryer, and analytical balance. The weighing bottle containing the test food needs to be manually moved between the three equipments, dried, cooled, weighed, and repeated until constant weight. The test process is tedious and monotonous. The manual operation has a great influence on the test results. After the weighing bottle is taken out of the oven, a slight carelessness will cause the test food to absorb moisture and affect the test results. For example, the drying ability of the desiccant in the dryer is weakened and weighed. The operation takes a long time. The new C830 migration and non-volatiles analyzer can automatically dry and weigh in one device without the need of a cooling process, avoiding the tester's repetitive test operation and improving the test efficiency. In order to verify the repeatability and accuracy of the new equipment test results, the water in three different moisture content foods was tested by traditional manual detection and new automated high-efficiency detection methods.
1 , equipment and samples
1.1 Traditional manual detection methods
SL 101 electric blast drying oven: temperature control range from room temperature to 250 ° C, accuracy is ± 1 ° C;
BSA423S electronic analytical balance: range of 220 g, accuracy of 0.1 mg;
Dryer: The color changing silica gel is used as a desiccant.
1.2 New automated testing methods
C830 migration and non-volatiles tester: test range 0.1 ~ 80000 mg, resolution of 0.01 mg; test temperature range of room temperature ~ 130 ° C, temperature control accuracy of ± 0.3 ° C; set evaporation, drying, weighing in one It can automatically and accurately weigh, the test process does not need manual participation; the volatile reagents can be collected and processed in the airtight system, and the requirements for the laboratory ventilation system are low; the international ling first quick evaporation technology is adopted to shorten Evaporation time; 9 station design, test process independent of each other, high test efficiency; through the special design of the constant temperature cavity and weighing system, greatly improve the test accuracy of the equipment.
1.3 sample
Bread, biscuits, wheat flour.
2 , the test process
2.1 Empty weighing bottle constant weight
2.1.1 Traditional manual detection methods
(1) Color-changing silica gel heating and dehydration
The temperature of the drying oven was set to 110 ° C. After the set temperature was reached, the color changing silica gel was dehydrated in a dry box for 2 hours, and taken out into a desiccator for use.
(2) Constant weight
Set the temperature of the drying oven to 102 ° C. After reaching the temperature, put the empty weighing bottle into the oven and dry it. After 1 hour, take it out, place it in the desiccator for 0.5 h as soon as possible, take out the weighing, repeat the drying, cooling, and weigh Heavy, until the difference between the two before and after the quality is not more than 2mg.
2.1.2 New automated detection method
Place the empty weighing bottle on the tray rack of the corresponding number in the equipment, close the test chamber door, do not enable the evaporation module, directly enter the test, select the difference mode, the difference is set to 2 mg, and the test temperature is set to 102 °C. The weighing interval was set to 60 min and the test was started. The equipment automatically performs drying and intermittent weighing according to the set parameters. When the difference between the current two weighing results does not exceed 2 mg, the equipment automatically stops the test.
2.2 Preparation of samples
The bread and biscuit samples were ground and the wheat flour samples were evenly mixed, and then a certain amount of bread, biscuit, and wheat flour samples were accurately weighed using a weighed bottle that had been dried to weigh.
2.3 Loading weighing bottle constant weight
2.3.1 Traditional manual detection methods
The weighing bottle containing three kinds of samples was placed in a drying oven at 102 ° C. After 2 hours, it was taken out, placed in a desiccator for 0.5 h, then weighed, placed in a dry box again, taken out after 1 h, and cooled for 0.5 h. Weighing, repeated drying for 1 h - cooling for 0.5 h - weighing process until the difference between the two before and after the mass difference does not exceed 2 mg.
2.3.2 New automatic detection method
In the same way as the constant weight operation of the empty weighing bottle, put the weighing bottle, set the parameters, and start the test.
3 , results and discussion
The test results of the moisture content of the three samples tested by the two types of detection methods are shown in Table 1.
Table 1 Results of the three samples tested with two test methods
result | Traditional manual inspection (g/100g) | New automated test (g/100g) | ||||||
1 | 2 | 3 | average value | 1 | 2 | 3 | average value | |
bread | 36.4 | 34.1 | 37.9 | 36.1 | 36.1 | 37.3 | 35.4 | 36.3 |
Wheat flour | 10.9 | 11.7 | 10.3 | 11.0 | 11.1 | 10.8 | 10.1 | 10.7 |
Biscuits | 2.91 | 3.09 | 3.17 | 3.06 | 3.03 | 3.10 | 3.09 | 3.07 |
As can be seen from the data in Table 1, in the three samples, the moisture content in the bread sample was higher, the moisture in the wheat flour sample was centered, and the moisture in the biscuit sample was low. In addition, the deviations between traditional manual detection and new automated detection are small. The difference between the test results of bread, wheat flour and biscuit samples is 0.2 g/100g, 0.3 g/100g, 0.01 g/100g, relative deviation. 0.6%, 3%, 0.3%, in line with the requirements of GB 5009.3-2016, the deviation of test results does not exceed 10%, which indicates that when testing the moisture in high, medium and low water content foods, the two methods The test results are consistent.
The relative deviations between the single test values ​​and the average values ​​of the three samples tested by the new automated test were: bread samples 0.6%, 2.8%, 2.5%, wheat flour samples 3.7%, 0.9%, 5.6%, biscuit samples 1.3% 1.0%, 0.7%, all within 10%, indicating that the test results are reproducible and stable.
The traditional manual testing and new automatic testing of the three samples are used for 7.6h and 5.1h respectively. In the traditional manual testing process, manual gap weighing cups and weighing operations are required. The new automatic testing is performed after the start of the test. Automatic operation, no manual intervention, which shows that the new automatic testing equipment has the characteristics of high test efficiency and simple operation in testing the moisture content of food.
4 , conclusion
The new automatic testing equipment can intelligently complete the detection of moisture in foods. The test results are accurate and reliable, the stability is good, the test efficiency is high, the human operation and frequent changes of the test environment are avoided, and the oven, dryer and electronic analytical balance can be replaced. The composition of the traditional test equipment. In addition to the drying function, the automation device is equipped with an evaporation function and a volatile reagent recovery function, which can be used for testing the properties of fats, solids, total migration in food packaging materials, and capable of volatilizing the solvent during the test. Recycling reduces the hazards of the test to the operator and the environment.
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