Research On The Processing Kinetics And The Mechanism Of Color Browning During The Processing Of Gardeniae Fructus Praeparatus

Gardenia is the dried fruit of Gardenia jasminoides Ellis,a plant of Rubiaceae.It has the functions of reducing fire and removing irritation,clearing heat and dampness,cooling blood and detoxifying.The raw gardenia are bitter and cold,which is easy to hurt the spleen and stomach.The bitter and cold nature of gardenia is weakened after frying,and the effect of cooling blood and hemostasis is enhanced,so it is widely used in clinic.ObjectiveUsing thermal analysis techniques and chemical kinetics principles to investigate the pyrolysis characteristics of gardenia,and initially reveal the temperature-time-material dynamics of Gardeniae Fructus Praeparatus（Jiaozhizi in chinese herbal name,JZZ）during processing;The mid-infrared spectroscopy technique was used to analyze the macro and fingerprint information of the samples during the processing of JZZ;Based on the exterior interior relation,the mechanism of the processing of JZZ was revealed from the view of Maillard reaction.MethodThe main pyrolysis temperature range of gardenia was determined by thermogravimetry to simulate the processing of JZZ,prepare processing pieces at different temperatures.HPLC was used to analyze the content changes of 9 main components in JZZ process decoction pieces under different temperature-time.The processing kinetics equation was established according to the content change rule and the chemical kinetics principle.Using mid-infrared spectroscopy to perform one-dimensional infrared spectroscopy analysis of raw gardenia and crcinⅠ,and using crocinⅠas a control,to analyze the main components in raw gardenia,then the samples during the processing of JZZ were analyzed by one-dimensional infrared spectrum and second-order derivative spectrum.The visual analyzer was used to analyze the change law of apparent color（chromaticity space parameter）of the samples during the processing of JZZ;the intrinsic component changes related to the Maillard reaction with the multi-component and multi-index focusing the processing of JZZ were studied;the total reducing sugar content,total amino acid content,and A420（absorbance at 420nm）changes of the samples during the processing of JZZ were determined by UV spectrophotometer,p H meter was used to determine the acidity and basicity during the processing of JZZ,HPLC was used to determine the 5-HMF content of the samples during the processing of JZZ.In the study of gardenia polysaccharide,the content of polysaccharide was determined by phenol sulfuric acid method,the molecular weight distribution of polysaccharides was determined by high performance gel chromatography,polysaccharide composition was analyzed by HPLC-ELSD.Through spss 24.0 software,Pearson correlation analysis and linear regression analysis were carried out between the color parameters L*（lightness value）,a*（red green value）,b*（yellow blue value）,E*ab（total color value）and total amino acid content,total reducing sugar content,total polysaccharide content,A420,p H value and 5-HMF content.ResultsThe main pyrolysis temperature range of raw gardenia is 229.7-329.4℃,the kinetic equation of geniposide is ln K=9.5938-6968.3·T^-1,the kinetic equation of crocin I is ln K=5.4161-4.72.7·T^-1,and the kinetic equation of multicomponent is ln K=7.703-5801.2·T^-1,r=0.9943.The results of one-dimensional infrared spectrum analysis showed that the absorption peak at 1628 cm^-1 moved to low frequency gradually with the increase of frying time,and appeared at 1623 cm^-1,which may be due to the change of ester group in JZZ during frying.The results of the second derivative analysis showed that the 1228 cm^-1 decreased gradually,with the increase of processing time,and increased gradually to 1239 cm^-1,1050 cm^-1 and 1033 cm^-1increased gradually,which may be related to the change of polysaccharide components in the processing of JZZ.The objective and digital analysis of the samples color during the processing of JZZ is basically consistent with the traditional subjective color judgment of JZZ.With the increase of processing time,the content of total reducing sugar and total amino acid decreased,no significant change in total polysaccharide content,p H is in the acidic range,and the content of 5-HMF and A420 increased.The molecular weight distribution experimental results showed that processing has degraded gardenia polysaccharides.The analysis of the monosaccharide composition of gardenia polysaccharide showed that both the raw gardenia polysaccharide and the JZZ polysaccharide were composed of arabinose,fructose,mannose and glucose.The results of Pearson correlation analysis showed that the values of L*,a*,b*,E*ab were significantly correlated with the total reducing sugar content,total amino acid content,5-HMF content and A420（P<0.01）,but not with the total polysaccharide content and p H（P>0.05）,among which,the values of L*,a*,b*,E*ab are positively correlated with the total reducing sugar content and total amino acids content,negatively correlated with A420 and 5-HMF content.The results of linear regression analysis also showed that the two are highly correlated.The results showed that Maillard reaction occurred during the processing of JZZ.ConclusionThe establishment of the kinetic equations of geniposide,crocin I and multicomponent can provide a basis for the establishment of the processing endpoint of JZZ;Using the mid-infrared spectroscopy technology to analyze the samples during the processing of JZZ,it can not only provide a basis for the identification of different decoction pieces of Gardenia jasminoides Ellis,but also provide a reference for explaining the processing mechanism of JZZ.Through the correlation study between the color change of JZZ and Maillard reaction,it not only proves that the Maillard reaction occurs during the processing of JZZ,but also provides a basis for the objective digital analysis of the subjective color of JZZ,and provides a reference for explaining the processing mechanism of JZZ from a new perspective.