| The plastic products made of polyolefin resin are widely used in food packaging materials because of its light texture and large elasticity.Some studies have found that polyolefin resin will produce peculiar smell,migrate to the food or beverage directly contacted with it,which will cause potential harm to human health,and may also cause peculiar smell of food.Therefore,it is urgent to investigate the source and composition of odor compounds.In this paper,polyolefin resin is used as a research material to establish monitoring conditions for detecting volatile components,and to find compounds that have an important contribution to odor.The above data can provide data support for reducing the odor of polyolefin resin and guide the correct implementation of processing technology of odorless polyolefin resin.The main research contents and results are as follows:1.Optimization of detection conditions of volatile components in polyolefin resin:the volatile components of polyolefin resin were detected by Purge and trap,solid phase microextraction(SPME)and gas chromatography-mass spectrometry(GC-MS).The number of detected peaks and sum of peak area are used as evaluation indexes to explain the influence of sample pretreatment technology,column,test matrix,fiber,extraction time,extraction temperature,sample volume on the test results.The response surface method was used to optimize the test conditions.The optimum process conditions was that SPME-GC-MS,the polar column DB-WAX,75?m Carboxen TM-PDMS fiber,water as the test matrix,extraction temperature 64?,extraction time 34 min,sample volume 2.0g.2.Validation parameters:all compounds have a good linearity(R~2>0.99)for a wide range of concentrations essayed,the results for recovery were in the range of 80%-110%,these LOD values ranged between 0.3?g/kg for octanal and the highest value(11?g/kg)calculated for ethyl octanoate.The intra-assay precisions were expressed as relative standard deviations(RSD,%).These values were lower than 2%.In conclusion,this method is sensitive,reproducible,accurate and reliable.3.GC-MS analysis of volatile components of polyolefin resin and its raw materials(powder and additives):The results show that there are 58 compounds in bag resin and 66 compounds in bottle resin.The compounds include alkanes,alkenes,alcohols,esters,etc.the content of alkanes is higher,accounting for more than 90%.There are 53 kinds of powder,39 kinds of bag additive and 70 kinds of bottle additive.The volatile compounds mainly include alkanes,benzene rings,alcohols,esters,ethers.Among them,alkanes account for a large proportion in powder,and benzene rings account for a large proportion in additive.4.Analysis of GC×GC-TOF/MS results of volatile components of polyolefin resin:the results show that the main types of polyolefin resin volatiles are alkanes,alcohols,esters,aldehydes,ketones,acids,etc.,among which alkanes and alcohols are abundant.More than 40 compounds were detected by GC×GC-TOF/MS,including ketones,acids,aldehydes and other compounds not detected by GC-MS,which usually have strong odor characteristics.The data show that GC×GC-TOF/MS can be used to detect the odor substances of polyolefin resin.5.Determine and track the odor substances of polyolefin resin:according to the odor activity value of the compounds,the key odor substances were determined.The key odor compounds of bag resin are toluene,o-xylene,nonanal,decanal,2-ethyl-1-hexanol and 4-methyloctane;the odor compounds of bottle resin are o-xylene,2-ethyl-1-hexanol,nonanal,decanal and 4-methyloctane.On the basis of the resin processing technology,trace the source of odor substances,in addition to 4-methyloctane,the other five components are introduced into the packaging materials by additives,which lead to the key substances of peculiar smell in the packaging materials.6.Screening of important odor contributors by olfactory technology:it was found that 2-ethyl-1-hexanol had a greater contribution to odor in bag resin and bottle resin,followed by decanal and nonanal. |
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