Study On Application Of The Molecular Weight Distribution Fingerprint Of The Soluble Protein And Comprehensive Materials In Rapid Authentication And Detection Of Orange Juice Authenticity

With the increasing demand of orange Juice, the events of adulteration happened frequently.The detection technology of adulteration has become hot spot and technical problem to be solved in beverage industries and food safety fields. Aiming at solving the problem, we adopts rapid detection equipment of independent innovation to study the rapid authentication and detection technology of orange juice. We established a rapid identification method of orange juice authenticity by establishing the fingerprint of the soluble proteins and substances(including proteins, phenols, carbohydrates and other soluble substances) in orange juice, which distributed by molecular weight, the main research contents include the following:1. A method for continuously detecting soluble proteins in orange juice according to molecular weight distribution by gel chromatography(GFC) separation coupled with post-column composite Coomassie brilliant blue staining was developed. The method was optimized by selecting column packing, column length and other experimental conditions basing on the range of the soluble protein molecular weight distribution in orange juice. Samples were filtered and then separated by No. 2 Sephadex gel chromatography column(30cm×1.2cm), 0.05mol/L KCl solution as mobile phase elution.The post columnoutflow liquid was stained with composite chromogenic agent and continuously detected at the wavelength of 595 nm. The method is simple and has less interference, can be directly on the machine without complicated pretreatment.2.The fingerprint of the soluble proteins in orange juice distributed by molecular weight was obtained by studying the characteristics of orange juice from different areas, different seasons, different fruit juice content. The molecular weight distribution fingerprint of orange juice protein has 4 peaks, the distribution range of molecular weight of peak1 was about 45KDa~70KDa, the peak 2 to peak4 was about 1KDa~10KDa. The protein fingerprint of the other kinds of fruit juice and blending false drinks were different from the fingerprint of orange juice.The interference of the additives on the protein fingerprint was studied and found that the use of additives had little effect on the characteristics. The rapid qualitative identification of orange juice beverages, which pure juice content is higher than 5% can be realized rapidly by using the characteristics of protein fingerprint.3. The scanning maps of orange juice of different areas, different seasons, different fruit juice content in 190nm-800 nm were studied. Results showed the soluble substances in orange juice have characteristic absorption at the wavelength of 325 nm, which were different from that of 20 kinds of commonly used additive solution. The soluble substances in orange juice were separated and continuously detected at the wavelength of 325 nm by the rapid detection equipment of independent innovation according to the molecular weight distribution, getting the characteristic absorption spectrum.4. The characteristic absorption spectrum of the soluble substances in orange juice of different areas, different seasons, different fruit juice content distributed by the molecular weight were studied. Results showed the origin and the season has little effect on the comprehensive quantitative peak area values, the quantitative peak area value of the orange juice in the same system has a good linear relationship with fruit juice content, the correlation coefficient is more than 0.99,laid the foundation for using the comprehensive quantitative peak area value to quantify juice content. The interference of the additives on the absorption spectrum was studied and found that the use of additives had little effect on the peak type, but has a certain effect on the peak area values.5. A method was established for the rapid identification of the authenticity of the orange juice through the above study:The qualitative identification method of orange juice is: Making 100% orange juice prepared from Brazil, Fujian, Sichuan concentrated juice as the reference standards and detecting at the wavelength of 595 nm through the ZTJ-1 type juice protein tester to obtain the characteristic fingerprint of proteins distributed by the molecular weight. The samples whose fingerprint of proteins are basically the same as the reference standard are regared as orange juice. The method is suitable for identifying orange juice beverages, which pure juice content is higher than 5%.The quantitative detection method of orange juice is: Making 100% orange juice prepared from Brazil, Fujian,Sichuan concentrated juice as the reference standards and detecting at the wavelength of 325 nm through the ZTJ-1 type juice comprehensive material tester to obtain the characteristic fingerprint of the soluble comprehensive material distributed by the molecular weight. The juice content of samples were calculated by the percentage of the sample quantitative peak area in that of reference standards. The 80%-120% of the sample labeling content is the decision criteria. When the determination result is within the range, the actual juice content value of the sample was regared as consistent with the label. If the detected value is out of this range, the sample should be further verified by the national standard method.The method is applicable to detect samples which orange juice content is not less than 10%. In the practical detection, the characteristic spectrum of the soluble comprehensive materials should be in combination with fingerprint of proteins to make qualitative and quantitative analysis.