Study On The Deterioration Mechanism And Discriminant Model Of Armeniacae Semen Amarum With Rancidity During Storage

Objective: Armeniacae Semen Amarum was selected as the representative of traditional chinese medicinal(TCM)of kernel fruit that are easy to rancidity.The aim is to explore the mechanism of rancidity during storage by researching the changes of appearance traits,physical and chemical properties and physiological activity of Armeniacae Semen Amarum in deterioration process.The results provide theoretical supports for establishing reasonable storage conditions of TCM of kernel fruit.Headspace-gas chromatography-ion mobility spectrometry(HS-GC-IMS)is used to extract and analyze volatile organic compounds(VOCs)in Armeniacae Semen Amarum with different rancidity levels,which combined with chemometric methods to establish an accurate,fast and stable discriminant model for judging the rancidity levels of Armeniacae Semen Amarum.Based on the above two aspects of research,the results have important theoretical guiding significance for the prevention and control of the rancidity of Armeniacae Semen Amarum,and they also provide new methods and new ideas for the objective evaluation of the quality of rancid TCM.Methods:(1)The constant temperature and humidity accelerated test and the long-term sample retention method were adopted to prepare the Armeniacae Semen Amarum,and the traditional sensory evaluation method was used to classify them.(2)In the experiment,seven internal deterioration indexes,including water value,water activity,relative conductivity,malondialdehyde(MDA)content,fatty oil content,peroxide value and acid value,were selected to characterize the quality of Armeniacae Semen Amarum.Water content and water activity were measured by toluene method and water activity meter,respectively;The content of fatty oil was obtained by soxhlet extraction method;The acid value and peroxide value were measured in accordance with the general rules 0713 and 2303 of the 2020 edition of the Pharmacopoeia of the People’s Republic of China(Part 4),respectively;The MDA content and conductivity value were measured using thiobarbituric acid colorimetric and conductivity meter,resepectively.(3)HS-GC-IMS was used to extract and analyze the VOCs of Armeniacae Semen Amarum with different rancidity levels.The analysis results were combined with chemometric methods such as principal component analysis(PCA)and stepwise linear discriminant analysis(Step-LDA)to establish a feasible rancidity discriminant model.Results:(1)The constant temperature and humidity accelerated test was used to simulate the preparation of Armeniacae Semen Amarum with different rancidity levels,and 20 groups(100 samples)were obtained in total.Traditional sensory evaluation method divided the above-mentioned samples into three groups: no rancidity,light rancidity and rancidity.Only the samples from the first 6 months were obtained in the long-term retention test,and all samples were identified without rancidity by the traditional sensory method.(2)Quantitative analysis of each index components had been carried out,and it was found that in the process of rancidity,as the storage time was prolonged,the fatty oil content decreased,and the content of other indexes showed an upward trend.Under the storage conditions of high temperature and high humidity,this process accelerated;Combining the character identification results,it was concluded that the phenomena of discoloration,softness,and rancidity after Armeniacae Semen Amarum rancidity were related to the oxidative rancidity of fatty oil.Temperature,humidity,oxygen and other external factors were the key factors that cause oxidative rancidity.It is recommended that Armeniacae Semen Amarum should be stored in a low-temperature,dry environment,as well as short storage time.(3)By comparing the GC-IMS maps of Armeniacae Semen Amarum with different rancidity levels,it was found that the types and contents of VOCs were different from each other;The qualitative analysis of VOCs by GC-IMS Library Search software showed41 kinds of volatile components;Based on the peak intensities of the VOCs in the fingerprint,27 biomarkers were screened out.The information of biomarkers were combined with PCA and Step-LDA to establish a classification and discriminant model,which can effectively distinguish Armeniacae Semen Amarum with different rancidity levels.Conclusions: Storage conditions of high temperature and high humidity can accelerate the deterioration of Armeniacae Semen Amarum,which may be due to the increase of internal water content and the increase of cell permeability,and then lead to the outflow of fatty oil and a series of oxidative decomposition reactions,and finally rancidity occurs.It is recommended that Armeniacae Semen Amarum should be packaged in polyethylene materials and stored in a low-temperature,dry environment,and the storage time should not be too long.The established rancidity discrimination model of Armeniacae Semen Amarum can comprehensively reflect the“quality” and “quantity” of TCM,and can quickly,accurately and stably distinguish the quality of Armeniacae Semen Amarum.This research provides a scientific basis for preventing and controlling the rancidity of TCM,as well as provides a new method for the rapid identification it and the objective judgment of the levels of rancidity.