Regulation And Effect Factors Of Aroma Release From Stewed Pork With Brown Sauce During Oral Processing

Food oral processing is a complex dynamic process of food properties and oral physiological response.While food is being eaten,structural deformation,particle reduction and chemical changes occur from the original structure through the joint action of teeth,tongue,saliva,etc.A new structure-bolus can be swallowed safely and will be triggered swallowing eventually.During oral processing,which induces the release of flavor compounds,and then in turn influence flavor perception.Oral processing plays an important role in the release of aroma compounds.As an "primitive state fat-dependent" food,Stewed Pork with Brown Sauce is the most suitable carrier for oral processing and mouth-feel perceptions research of meat products.In this paper,Stewed Pork with Brown Sauce was used as the research object to study the changes of oral physiological parameters and the characteristics of the boluses during oral processing,followed by solid phase microextraction（SPME）-gas chromatography/mass spectrometry（GC/MS）to detect volatile organic compounds in the exhaled gas of the subjects.To clarify the aroma release kinetics and effects of Stewed Pork with Brown Sauce at different oral processing stages.The main research contents and results were as follows:1.The panel of four subjects was built by recruiting members for evaluation,selection,and professional training.The dynamic changes of chewing parameters,salivation and bolus moisture content in individual subjects during oral processing were tracked and analyzed.In addition,some physical and chemical properties of the boluses at different oral processing stages were tested.To explore the differences in individual subject and changes in the characteristics of the bolus caused by oral physiology.Results showed that:（1）There were significant differences in chewing parameters and saliva secretion among four subjects（P<0.05）,but there was a certain consistency in the change:during oral processing of stewed pork.With the prolongation of chewing time,the chewing cycles of each subject increased significantly（P<0.05）,whereas the chewing frequency was not changed significantly,and it was stabilized relatively（P>0.05）.Moisture content of wet and dry basis in the boluses increased significantly at different oral processing stages（P<0.05）;the salivation was increased significantly for each subject（P<0.05）,while the saliva flow rate was decreased significantly（P<0.05）and tend to be stabilized.（2）The fat content and oxidative decomposition of stewed pork during oral processing also changed:the fat content of the bolus showed a decreasing trend,but there was no significant difference（P>0.05）;the fat content dissolved in saliva changed significantly（P<0.05）and tend to be stable at the middle and late oral processing stages;fat oxidation and the change of fatty acid composition and composition ratio,which also plays an important role in the aroma release during oral processing of Stewed Pork with Brown Sauce.（3）The average diameter of stewed pork bolus apparent particle size corresponding to D₅₀0 increased significantly during oral processing（P<0.05）,the particle size distribution curve showed "double peak";Further,microstructure observation of boluses showed that the droplets of oil-saliva was formed during oral processing,and the emulsion droplets size increased and became finer and denser;In addition,the bolus at the early stage of oral processing showed a layered distribution,and the reticular network structure was obvious at the middle and late stages.The bolus ready-to-swallow possessed a higher uniformity,illustrated a relatively tight solid continuous phase.Oral processing behavior can change the characteristics of the bolus,which in turn influences the mass transfer of aroma compounds in the bolus-air phase.2.Four subjects chewed the samples of Stewed Pork with Brown Sauce freely and collected the exhaled gas samples used Tedlar? gas bags at different oral processing stages,followed by solid phase microextraction-gas chromatography/mass spectrometry to detect volatile organic compounds in the exhaled gas.Qualitative and quantitative analysis of the exhaled gas for each subject at different oral processing stages with a discontinuous manner.Combined with the change of chewing parameters and the characteristics of the bolus,the aroma release pattern in the oral cavity and effects of aroma release were comprehensively analyzed.The results showed that:the aroma release curves were found that the aroma release of stewed pork was always in dynamic during oral processing,the inter-individual difference was still unavoidable,and there was a large aroma release at the early post-swallow period;the ratio of aroma release was larger at the pre-swallow stage than the post-swallow stage.However,the higher the hydrophobicity（log P value）of the volatile,the more release of aroma at post-swallow;Correlation analysis showed that the aroma release amount was significant positive correlation between the chewing time（r=0.856,P<0.01）,chewing cycles（r=0.855,P<0.01）,the moisture content of the dry（r=0.850,P<0.01）and wet（r=0.836,P<0.01）bolus,and salivation（r=0.822,P<0.01）;whereas which was significant negatively correlation with saliva flow rate（r=-0.668,P<0.01）,dissolved fat in saliva（r=-0.543,P<0.05）,and fat content in the bolus（r=-0.644,P<0.01）.The oral physiological parameters of the subjects determine the pattern of aroma release,the oral processing behavior changes the characteristics of the food bolus,and the combination of stewed pork bolus components effect the aroma release together.While the presence of the fat of the bolus can act as a solvent or "flavour sink" solubilizing lipophilic volatiles,retaining and delaying their in-mouth release.