Abstract: Quick-frozen foods are processed by low temperature ( below -18 °C ) . The moisture and juice in the food tissue are not easy to lose. The microorganisms are basically not propagated and the food safety is guaranteed. However, the odor often occurs during the use of packaging materials, which affects the taste and odor of the food. Therefore, the relevant chemical index is the most important aspect of quality inspection. In this paper, a residual solvent amount Labthink GC-7800 gas chromatograph testing bag blue light, in order to validate the principle and described, device parameters and briefly during the test device, providing a detection device to select the appropriate enterprise monitoring odor bag reference.

Keywords: frozen food, plastic composite film, printing film bags, residual solvent odor, gas chromatography

1 , the meaning

Frozen food refers to the use of rice, noodles, and miscellaneous grains as the main raw materials , and meat, vegetables, etc. as auxiliary materials. After being processed into various types of cooked or uncooked main foods, they are immediately frozen and frozen. Under the conditions of transportation, storage and sales of various types of staple foods, such as quick-frozen steamed buns, frozen dumplings, quick-frozen dumplings, quick-frozen buns, Hanamaki, spring rolls and so on. Fast-frozen foods are generally packaged in plastic composite film. Enterprises will print a large number of product images on the surface of the bags for better sales. Therefore, the adhesives in the compounding process and the printing ink components will introduce solvents, such as the production process of packaging materials. Improper handling can cause a high amount of residual solvents in the package, causing pungent odors, and in severe cases it will migrate to quick-freeze products. Therefore, reducing the amount of solvent residues in packaging materials has profound implications for improving the image and quality of products.

Figure 1 frozen food packaging bags

2 , the implementation of standards

Frequently frozen food packaging materials are plastic composite film, standard detection methods refer to residual solvent mainly GB / T 10004-2008 "plastic composite packaging films, bags dry lamination, extrusion lamination."

3 , test sample

Frozen food bags provided by a food factory.

4 , test equipment

LabthinkInstrumentsCo Ltd. independently developed a G C - 7800 gas chromatograph.

FIG 2 G C - 7800 gas chromatograph

4.1 Test principle

Gas chromatography is a multi-component mixture separation and analysis tool. It uses inert gas as the mobile phase and column separation technology. When multiple analytes enter the column, due to the different partition coefficients of each component in the column, the flow rate of each component in the column is different. After a certain column length, the mixed components leave the column separately. After entering the detector, after being detected, it is converted into an electrical signal and sent to the data processing workstation, thus completing the detection and analysis of the tested substances.

4.2 Scope of application

(1) Solvent residue: It is applicable to the analysis and test of residual solvents of various foods, pharmaceutical packaging plastic films, paper-plastic composite films, cigarette packets and other materials.

(2) Purity analysis: It is applicable to the purity analysis of various packaging and printing solvents.

(3) Moisture analysis: It is applicable to the solvent moisture content analysis in the packaging and printing industry.

4.3 Equipment Parameters

The instrument can be thermostatted and temperature-programmed. The column room is equipped with a flexible rear door automatic temperature control system, which can realize near-room temperature operation in true sense. Column room temperature control room temperature + 3 °C ~ 400 °C , temperature control accuracy is better than ± 0.1 °C , set temperature and display temperature deviation is less than 1 °C , set temperature and actual temperature deviation Not more than 2% . The instrument can be programmed to heat up, the temperature rise order is 5 steps , the heating rate is 0.1 ~ 30 °C /min , and the repeatability of the program temperature rise is no more than 2% . The temperature control accuracy of the gasification chamber and the detection chamber in the temperature range of +15 °C to 200 °C at room temperature is ±0.1 °C , and the accuracy of the temperature control is ±0.2 ° C when it is greater than 200 ° C . The basic configuration of the instrument is a hydrogen flame ionization detector (FID ) with a detection limit of no more than 2×10-11 g/s ( benzene ) , a noise no greater than 0.025 mV , and a drift no greater than 0.15 mV/h . The detector adopts unitized combination design and adopts plug-and-play expansion control mode. The configuration of the hydrogen flame detector and the thermal conductivity detector can be configured according to the user's analysis needs. The instrument can be installed with up to four detectors at the same time. The sample introduction system can be equipped with various sampling devices such as packed column head injection, capillary column split / splitless injection with membrane cleaning function . The response signal can reach a wide range of 1500 mV with good consistency and can meet the high purity sample analysis needs. Excellent column performance, room temperature +3 °C near room temperature when the detector and gasification chamber are both at 200 °C , and the instrument has a good program temperature repeatability, ensuring the analysis of complex components sample retention The consistency of time. A tester integrates seven independent test programs such as stretching, peeling, and tearing to provide users with a variety of test items to choose from. The instrument has a high temperature protection function. If any temperature control exceeds a certain range of the set temperature (set value is 20 °C ), the instrument will be powered off and alarmed. The instrument has a carrier gas low pressure, gas protection function. Unique operating control system software and hardware design, the instrument in the process of running the system automatically implement the entire software monitoring, fundamentally put an end to the instrument temperature and operating parameters out of control. Achieved without "fault" over-temperature protection, as well as a unique active over-temperature protection and over-temperature dual hardware self-locking control structure to ensure the safe operation of equipment when unattended.

5 , the test process

(1) Set the test parameters, click on the start, GC-7800 gas chromatograph to start the baseline balance.

(2) After the baseline of the instrument is stable, configure the mixed standards with different concentrations, inject into the sealed headspace bottle and place in a constant temperature chamber of 80±2 °C for 30 min .

(3) Use the sampling needle to take a certain amount of standard sample gas from the above headspace bottle, and quickly inject into the chromatograph, or configure the automatic sampler to automatically sample. The standard curve of the peak area and corresponding concentration of each standard substance was plotted.

(4) A sample of 0.2 m2 quickly cut into pieces of 10 mm × 30 mm, into a clean preheated under conditions of 80 ± 2 ℃ flask, quickly sealed, placed in 80 ± 2 ℃ constant greenhouse Place 30 minutes . Note that the sample should be prevented from being contaminated during sample preparation.

(5) Use a sampling needle to take a specific amount of sample gas from the thermostatted sample bottle, and quickly inject into the chromatograph, or configure the autosampler to automatically sample.

(6) According to the peak area of ​​the sample, the concentration of the component is read from the standard curve of the corresponding component.

6 , test results

The total amount of solvent residues in the quick-frozen ball bag samples was 10.1017 mg/m2 , with esters of 9.4879 mg/m2 and toxic and hazardous benzenes of 0.6138 mg/m2 .

7. Conclusion

According to GB/T 10004-2008 "Plastic composite film for packaging, bag dry compounding, extrusion compounding", the solvent residue is defined as: the total amount of solvent residue ≤ 5.0 mg/m2 , among which the benzene solvent can not be detected (< 0.01 mg/m2) . The above test results indicated that the total amount of solvent residue was excessive, and the odor of the sample was mainly caused by the high residual solvent amount. The Languang GC-7800 gas chromatograph has the advantages of high accuracy, good accuracy, and safe operation in the testing of solvent residues. It can truly reflect the amount of residual organic solvents in the packaging materials, helping packaging manufacturers and companies to better monitor packaging. Hygienic properties. L abthink blue light has been committed to providing professional testing services and equipment for global customers, For related testing equipment and testing services, you can visit Labthink website to view specific information or call us directly. The more you understand, the more trust! Jinan Languang Electromechanical Technology Co., Ltd. is willing to take this opportunity to increase technical exchanges and cooperation with enterprises and institutions in the industry.

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