Study On Rapid Detection Of Physicochemical Indexes And Quality Evaluation Of Olive Oil

Olive oil is a natural juice which is extracted from fresh olive by cold pressed,riching in the nutrients such as the unsaturated fatty acids,sterols,squalene,pigment?chlorophyll,carotene?and others,which with the prevention of cardiovascular disease,cancer,improving the digestive system,beautifying.With the increasing demand for olive oil,more and more attention has been paid to the quality of olive oil.At present,the detection methods have many disadvantages,such as complex operation,slow detection speed and consuming a large number of reagents.It can not detect the quality of olive oil quickly and accurately.In terms of quality evaluation,there is no complete quality evaluation system.This study based on the advantages of near infrared spectroscopy which is a rapid,accurate and nondestructive detection method,combining with partial least squares analysis model in order to realize rapid detection of physicochemical index establishment of olive oils.Meanwhile,based on the detection of 8 quality parameters,using multivariate statistics,in order to establish quality evaluation system of olive oil,and analyse the quality of olive oils from different origin.The results are as follows:1.To scan the near infrared spectra of 70 olive oil samples,and detect the physicochemical indexes?acid value,peroxide value,K value?,using partial least squares?PLS?analysis,established quantitative models of acid value,peroxide value,K value,root mean square error correction and prediction?RMSEC,RMSEP?,correlation coefficient correction and prediction?Rc,Rp?are used to evaluate performance of models.The results show that the root mean square error of the model are close to 0,the correlation coefficients were greater than 0.99,the stability of the model is well.Blind sample validation of 20unknown samples,the model predicted values and the real value are used to do linear regression analysis,the slope of the linear equation is close to 1,the intercept is close to 0,R²was greater than 0.99,indicating the prediction results of unknown samples is better.By means of variance paired t test,t_20,0.050,0.05 is greater than 0.05,indicating that there is no significant difference between NIR and standard methods.Based on near infrared spectroscopy model and partial least squares?PLS?analysis,the physicochemical properties of olive oil can be rapidly detected.2.Select 9 indexes to evaluate the quality of olive oil,and establish a quality evaluation system of olive oil based on cluster analysis?CA?and principal component analysis?PCA?.Using principal component analysis?PCA?to replace the original information.The first principal component represents oxidation degree?K225,K232,K270 oxidation,peroxide value?,the second principal component mainly represents freshness degree?save time,pyropheophytin content,K value?,the third principal component mainly represents rancidity degree?acid?,the three principal component contribution rate were 50.01%,19.44%,10.92%,the cumulative contribution rate is 80.37%,so the three principal components can be used to evaluate quality of olive oil,the strength decreased gradually.The quality evaluation system of olive oil can provide theoretical guidance for the quality analysis of olive oil.3.Based on the establishment of the quality evaluation system,the olive oil samples from different producing areas were analyzed.The results showed that the oxidation degree of olive oil samples in Spain and Turkey was low.Spain imports-China's sub packaging and domestic production of olive oil samples have a higher degree of freshness,olive oil samples of Turkey and Greece with the higher degree of rancidity,olive oil samples of Spanish have low rancidity degree,the Tunisian olive oil samples have high oxidation degree.Through the analysis,Spanish olive oil samples have the best quality.Through cluster analysis can be found all the olive oil samples were clustered into two categories,the first category contains olive oil samples of third interval of PC1-PC2 score and PC1-PC3 score,the quality of olive oil samples are better,another class contains olive oil sample in the first interval of the score map,olive oil samples are poor quality.The results of cluster analysis are consistent with the results of principal component analysis.Analysis of the quality from different habitats is of great practical significance for the origin traceability and quality evaluation of olive oil.