Research On Application Of Ultraviolet And Mid-Infrared Spectroscopy In Investigation Of Apple Juice

The scope of planting and processing of apple in china can hold the balance in the world. This paper aimed at the concentrated apple juice from 4 different factory, had studied the application of UV and MIR spectrspectroscopy on the detection of apple juice with a method of MIR and UV spectrum coupled with chemometrics, and develepped a faster,convenint method in investigation on apple juice. Investigate apple juice by U&V spectroscopy has the advantage of celerity, convenint, inexpensive and noncontaminated.The main results of this paper are as follows:A method of Multiple Linear Regression and UV spectrum Used for detection the concentration of apple juice was studied. The result indicates that different concentration of apple juice results in different absorb curve. While the concentration is lower than 70%, it has an obvious difference between different concentrations. While the concentration is higher than 70%, UV spectrum's discriminate capability descends along with the increasing of the concentration. The wavelength range from 280nm to 365nm was picked out depend on their RSD, and the variables were compressed by PCA (Principal component analysis). The Mathematical Model was established by Stepwise Regression, and then be optimized. The result of Cross Validation indicates that the Mathematical Model has a fine predict capability, the relationship between the predict value and the true value is 0.999.Apple juices adulterated with pear juice and sucrose solution at different levels can be discriminated successfully by PCA method. By the PCA method, samples adulterated with pear juice and sucrose solution at 5%, 10%, 15%, 20%, 25% and 30% level can be discriminated clearly. The results show that this method of detecting adulteration used for apple juice is fast and economical on the bass of having a high veracity.Take the exportion standard of concentrated apple juice as quality standard. The spectrum of qualified samples and unqualified samples has a different characteristic in the principle component distributing chart. The distributing of qualified samples is Centralism and the unqualified samples are dispersive. Similarity match model was built and the similarity match values of the samples were computed by this model. 94.4% of the similarity match values of qualified samples are over 90% while the similarity match values of unqualified samples are during 70%～90%. When set the threshold value of the similarity match value as 91.5%, the qualities of all the 32 samples were assessed by their similarity value and the results acquired from this method were coincided with the results acquired from chemic test. The validity was 96.8%.The MIR spectroscopies of concentrated apple juice from different manufactuer are similar, the shapes and the position of the peaks are similar during 1200cm-1-850cm-1 and the shapes are different during 850cm-1～700cm-1. Samples from different factories can be discriminated clearly by clustering analysis and principle component analysis on their IR spectrums, and the results from the two different methods are coincident. The average validity is 96.8%.