Optimization And Determination Of 5-hydroxymethylfurfural In Jujube

5-hydroxymethylfurfural(5-HMF)is a furan compound formed by Maillard reaction or dehydration of hexose,and it is often used as an evaluation index for the degree of Maillard reaction in food.Studies have reported that 5-HMF may be cytotoxic,teratogenic,carcinogenic,and genotoxic.Therefore,some countries and international organizations have established maximum limits for the content of 5-HMF in food.Due to the large amount of reducing sugars and amino acids in red dates,Maillard reaction and the formation of5-HMF are inevitable during the heat treatment process of red dates.In our previous study,it was found that adding a certain amount of acid solvent to the dried red jujube samples would lead to an increase in the content of 5-HMF in the samples.In addition,in the analysis of dried jujube polyphenols,the chromatographic peak at 12.87 min was found to be 5-HMF.These instructions are necessary to clarify the existence state of 5-HMF in dried red dates,and to optimize the analysis method of HMF in red dates,so as to provide technical support for the accurate analysis of 5-HMF content in dried red dates.Therefore,this paper firstly carried out the analysis of the existence state of 5-HMF in red dates,then optimized the processing conditions of red dates samples,and optimized and established the HPLC method of 5-HMF in red dates.Finally,a batch of dried red dates samples and jujube sauce were analyzed.5-HMF content in the product.The main conclusions from the research are as follows:1.Study on the state of 5-HMF in red datesFirst,0.5% hydrochloric acid and water were used as solvents to extract 5-HMF from red jujube by ultrasonic at room temperature,and it was found that the content of 5-HMF extracted by 0.5% hydrochloric acid was about 3 times that of water extraction;It was found that when the concentration of hydrochloric acid was less than 1%,5-HMF would not be produced in the sample,indicating that 0.5% hydrochloric acid was more sufficient to extract 5-HMF from jujube.The water extraction residue was extracted with 0.5%hydrochloric acid,and it was found that the sum of the 5-HMF extracted by water and the 5-HMF extracted in the residue was exactly the same as the 5-HMF extracted by 0.5% hydrochloric acid.In addition,after using fresh jujube as raw material and adding a certain 5-HMF standard to the sample,the samples were treated with 0.5% hydrochloric acid and water respectively,and it was found that there was no significant difference in their results(p>0.05).The jujube cell wall extracted with hydrochloric acid and distilled water was observed under a microscope,and it was found that the hydrochloric acid solution destroyed the cell wall and released 5-HMF,which increased the content of 5-HMF.These research results indicate that part of 5-HMF in red dates exists outside the cell wall in a free state,and a part is enclosed by the cell wall.Water extraction can only extract free 5-HMF,while 0.5% hydrochloric acid can extract the total 5-HMF in red dates.Extracted at the same time,which provides a theoretical basis for the accurate analysis of 5-HMF in red dates.2.Optimization of 5-HMF extraction conditions from red datesThe extraction conditions of 5-HMF in jujube were optimized by single factor and orthogonal experiments,and the primary and secondary relationship of the influence of each factor on the extraction effect of HMF was obtained as follows: hydrochloric acid concentration> ultrasonic time> material-liquid ratio;5-HMF in jujube was the best The extraction conditions were: hydrochloric acid concentration of0.5%,ultrasonic time of 20 min,and solid-liquid ratio(g/m L)of 1:40.Under these conditions,the content of 5-HMF in the red jujube samples was the highest,up to 57.505μg/g.3.Optimization and establishment of HPLC method for determination of 5HMF in red datesThe optimized HPLC analysis conditions are: column: ZORBAX SB-C18 column(4.6×250mm,5μm);column temperature: 30℃;detection wavelength: 283nm;mobile phase: 0.5% formic acid aqueous solution(B)and methanol(A);Isocratic elution: A:B=8:92(volume ratio);flow rate: 0.7 m L.min-1;injection volume: 10 μL.Under these HPLC conditions,a method for the determination of 5-HMF in red dates was established.RSD=3.22%)and high recovery rate(95.33%).In addition,this method has the advantages of stable chromatographic baseline,high chromatographic peak resolution,short analysis period,and simple mobile phase preparation.It shows that the established HPLC method is suitable for the determination of 5-HMF in jujube samples.4.Determination of 5-HMF in jujube samplesThrough the determination of 5-HMF content in different varieties of dried red dates,it was found that there were significant differences in 5-HMF in different varieties of red dates(p<0.05),and the content of Suanzao,Alarhui date,Hetian Zanhuang and Hami date was higher..Suanzao and Hetian Zanhuang had the highest 5-HMF contents of 36.954 μg/g and 36.679 μg/g,and Hetian Dongzao had the lowest content of4.545 μg/g.By analyzing the content of 5-HMF in the samples during the production of jujube sauce,it was found that the influence of red jujube varieties and temperature on the content of HMF in jujube sauce was significantly different(p<0.05).Among the three red jujube varieties,the jujube paste made from ash jujube has the highest HMF content,27.85 μg/g and 75.678 μg/g,respectively,while the winter jujube has the lowest content,21.21 μg/g and 71.495 μg/g,respectively;In terms of temperature,the higher the temperature,the higher the content of 5-HMF in the jujube sauce,indicating that the control of the temperature in the production of jujube sauce is conducive to reducing the HMF content in the product.