Effects Of Food Processing Conditions On The Properties Of Silicone Rubber Baking Moulds And The Migration Of Silicone Oligomers

Silicone rubber?SR?products are widely used in food contact materials due to their good heat resistance and flexibility.However,there are silicone oligomers with potential safety hazards in SR products.The silicone oligomers migrate to food,causing hidden dangers to human health.In this study,the effects of three food processing conditions of 175?baking,800 W microwaving,and-18?freezing on the performance of SR baking moulds and the migration of silicone oligomers from moulds to food simulants and cakes were studied,and their safety was evaluated.The specific studies were as follows:?1?The effects of three using conditions on the surface morphology,total volatile organic compounds?TVOC?content of SR baking moulds,and migration of silicone oligomers in the moulds to food simulants were studied.The results showed that baked at 175?,microwaved at800 W and frozen at-18?unchanged the chemical structure of the SR baking mould,but increased its surface roughness.The TVOC content in the SR baking mould was 2.53%.Both baking and microwaving significantly?P<0.05?reduced TVOC content in the mould,but the freezing treatment did not change significantly?P>0.05?.18 kinds of silicone oligomers migrated from the SR baking mould were detected by atmospheric pressure gas tandem time-of-flight mass spectrometer,and their molecular formula is[Si?CH₃?₂-O]n?n=4...21?.In the migration test at 70?for 2 h,the migration of silicone oligomers to isooctane was 3.16 and9.41 times that of 95%ethanol and Tenax?,respectively.And the silicone oligomers with a molecular weight of less than 1000 Da in isooctane account for 70.7%of the amount of total silicone oligomers,while 91.8%in 95%ethanol and 97.2%in Tenax?.Simultaneously,baking treatment significantly reduced the migration of silicone oligomers to food simulants?P<0.05?,followed by microwaving treatment and freezing treatment.?2?A solvent extraction-gas chromatography mass spectrometry method was established for the determination of the contents of low molecular weight silicone oligomers octamethylcyclotetrasiloxane?D4?,decamethylcyclopentasiloxane?D5?and dodecamethylcyclohexasiloxane?D6?in food contacted SR products,and the market samples were detected.Then the migration of D4-D6 to 95%ethanol were also studied.The results showed that infrared analysis identified 9 products as SR materials.The contents of D4-D6 in SR products were determined by gas chromatography mass spectrometry combined with ultrasonic extraction with n-hexane for 30 min.The contents of D4-D6 in SR baking moulds were more than that of SR teat and pressure cooker sealing ring,and the total average content of D4-D6 was1900.37 mg/kg.The single-sided migration of D4-D6 in a SR baking mould to 95%ethanol at60?reached the migration equilibrium in 150 min,and the migration rate of D4?71.36%?was the largest,followed by D5?57.03%?,and D6?49.31%?.?3?The changes in thermal stability and mechanical properties of SR baking moulds after baking and microwaving treatment were studied,and the migration of D4-D6 in the mould to olive oil and Tenax?during baking and microwaving were studied by headspace-gas mass spectrometry.The results showed that baking and microwaving unchanged the thermal stability of the SR baking mould,but the elongation at break of the mould was significantly?P<0.01?reduced and the tensile strength of the mould was also reduced.The migration rate of D4-D6 to olive oil increased gradually at 175?and reached equilibrium at 240 min,which were 88.00%,64.08%and 40.75%,respectively.And the migration rate of D4-D6 from mould to olive oil increased and then decreased under 800 W microwave conditions.However,the migration rate of D4-D6from mould to Tenax?gradually decreased at 175?baking and 800 W microwave conditions.Moreover,D4 has the strongest migration ability to olive oil and Tenax?,followed by d5 and D6.?4?A method for detecting D4-D6 in cakes was established and its safety was evaluated.The effects of the type of baking oils,repeated baking times of mould,and the type of added dairy products on the migration of D4-D6 in the mould to cakes were studied.Results showed that after extracting the cake in ultrasonic with acetonitrile for 20 min and repeating extraction 3times,the contents of D4-D6 in cake were detected by gas chromatography mass spectrometry.D4-D6 were all identified as Cramer III substances,and the total estimated daily intake of D4-D6 in cake was 63.34?g/d,which was lower than the threshold of toxicological concern?90?g/d?.However,the total estimated daily intake of D4-D6 in the bottom cake was higher than the threshold of toxicological concern.The migration of D4-D6 from SR baking mould to cakes were affected by the type of baking oil.And the contents of D4-D6 in the cake baked with corn oil was significantly greater than that baked with olive oil?P<0.05?,so olive oil is not suitable as an oily food simulant for SR baking mould.Increasing the baking times of the mould and adding milk or milk powder to the cake recipe significantly?P<0.05?reduced the contents of D4-D6 in the cake.