Psychophysical Experimental Study Of The Pungency Sensation Evoked By Chinese Pepper

Psychophysics is an exact science that specializes in the functional relationship between physical and psychological quantities.Pungency sensation refers to a type of trigeminal sensation,and represents the primary flavor characteristics of Sichuan cuisine and spicy food.Traditional research involving pungency sensation focuses on the separation,purification,qualitative,and quantitative analysis,as well as the biological activity of the pungency compounds.However,few experimental studies exist on the psychophysiology of the pungency sensation,especially regarding the relationship between stimulus and response,and the evaluation method used to determine pungency intensity.Pungency sensation and basic tastes,for example,sourness,sweetness,bitterness,saltiness and umami,are both essential food flavors in the Chinese diet.The lack of experimental psychophysical research on pungency limits the industrial application of pungent substances in flavor design,new product research,and development,as well as process improvement and quality control.Psychophysical studies on the basic tastes and heat sensation of foods have already been carried out and many breakthroughs have been made,but the psychophysical study on the pungency sensation evoked by Chinese pepper has not been reported so far.In this paper,essential oil of Chinese pepper was used as the experimental material,psychophysical,food sensory science and EEG?Electroencephalograph?spectral power analysis methods were used to carry out the research on the difference and intensity response law of pungency sensation,the dynamic response characteristics of pungency in the oral cavity and the spectral power-related pungency.Furthermore,dried Chinese pepper samples were used as experimental materials,paired comparison test,time intensity method,quantitative sensory profile method and UPLC-MS/MS method were used to determine the sensory intensity and properties of pungency sensation.The relationship between the pungency intensity?or properties?and the alkymide content of Chinese pepper were analyzed by multiple linear regression methods.The main conclusions were as follows:?1?Taking the response law of sensory variations and intensity into consideration,the recognition threshold,JND?just noticeable difference?,terminal threshold,and sensory intensity were determined with 2-AFC,A not A test,and the magnitude estimation method,after being subjected to various stimulation levels.The calculated Weber fraction was stable at 0.15 for low?0.030–0.50 mg essential oil per 1 ml water solution?,and 0.20 for moderate?0.50–1.0 mg essential oil per 1 ml water solution?pungency,and the exponent of the pungency was 0.71.The values of JND and sensory differentiations were calculated as 25 and 12,respectively.The sensory evaluation scale of pungency intensity can be determined according to the relationship between the JND and sensory differentiation values.Consequently,a theoretical reference is provided for the establishment of a sensory evaluation method with which to ascertain pungency intensity.?2?With reference to the method of pungency intensity,three aspects were modified and improved,based on the standard method of heat intensity.This process includes eliminating the effect of matrix preparation,setting the test statistics,and improving the sample preparation method.The sensory evaluation method of pungency intensity and grade was established based on psychophysical laws,and the results indicated excellent repeatability within,as well as between the sensory panels.Moreover,samples of Chinese red pepper were obtained from the primary cultivation areas in China,and the pungency intensity of the samples was determined as ranging from 100,000 to 560,000,while the grade ranged from 4 to 7.The establishment of this method makes the pungent seasoning,catering and food industries have the scientific grading standard of pungency intensity in the future.?3?Time intensity,descriptive analysis of the sensory profile,and temporal dominance sensation methods were used to study the dynamic pungency intensity,attributes,and response pathway in the oral cavity.Analysis of the time-intensity parameters suggested that Imax was positively correlated with AUC and Ttot.Through the analysis of the descriptive data,it can be seen that the attributes of numbing,tingling and bitterness showed a consistent trend:the higher the numbing attribute intensity,the higher the tingling and bitterness intensity while the lower the numbing attribute intensity,the lower the tingling and bitterness intensity.Analysis of the temporal response pathway in the oral cavity suggested that pungency sensation was centralized in the tip of the tongue while expanding around it,and was referred to as a hub-and-spoke type.?4?The chemical basis was determined by measuring the chemical composition and content using the ultra-performance liquid chromatography-mass spectrometry/mass spectrometry?UPLC-MS/MS?method.Compound 1,hydroxy-?-sanshool,hydroxy-?-sanshool,hydroxy-?-sanshool,hydroxy-?-sanshool,hydroxy-?-bungeanool,bungeanool,and isobungeanool were found to be the key pungency compounds.The relationship between the content of the key pungency compounds and pungency intensity were analyzed with PCR?Principal Components Regression?,RR?Ridge Regression?and PLSR?Partial Least Squares Regression?method.Using PLSR,regression model and correlation analysis results were obtained by comparing the content of the key pungency compounds with pungency intensity,as well as the content and pungency attributes.The PLSR regression model was Y=542556.9+1692.8X₁+11826.9X₂+87.2X₃-3331.4X₄+551.5X₅-19215.4X₆+8474.9X₇-1018.9X₈-3508.2X₉?p=0.00?and the RMSEC,RMSEP,R₁ and R₂ were 4.70E+04,1.17E+05,0.94 and 0.62,repectively.The correlation analysis showed that compound 8 was negatively correlated with all the pungency properties.Compound 1,dihydroxyzanthoxylum and hydroxy-?-sanshool were positively correlated with salivating,burning and numbing sensation.Compound 3 was positively correlated with the vibration,tingling,bitterness and astringency sensation.?5?The EEG spectral power associated with pungency were primarily expressed in delta,theta,alpha and beta,while the brain areas that were possibly stimulated were located in the bilateral frontal lobe and bilateral parietal lobe.The spectral power of pungency reached its peak in Rest 2₂0 s?delta band?and Rest 2₂4 s?theta band?.The power of four stimulations are all elevated and presented in the following order:heat,sweetness,pungency,and saltiness.The power trends are as follows:the power of heat increased rapidly and gradually declined to display only a minimal difference,while the power of pungency exhibited slow increases and decreases.Contrarily,the power of sweetness and saltiness both displayed rapid levels of elevation and decline.Therefore,the duration of power after stimulation suggested that the duration of pungency and heat significantly exceeded that of sweetness and saltiness.The psychophysical experimental study of pungency sensation provides a two-pronged result.Firstly,theoretical reference is provided for clarification of the mechanism responsible for trigeminal nerve flavor perception,as well as for the establishment of the quantitative evaluation method of pungency intensity.Moreover,it fills the blank of the sensation and perception of pungency.Secondly,the psychophysical experimental results present theoretical and practical reference value for the study of flavor perception interaction,flavor preference formation,and the mechanism responsible for stimulating emotion.