| Olive oil is famous for being rich in oleic acid and bioactive substances.With the improvement of health awareness,Chinese olive oil industry has begun to develop rapidly in recent years.Due to wide olive varieties,and the great difference of climate conditions between China and Mediterranean region,few studies and subsequent data is available on the characteristics of Chinses olive oil.Therefore,we collected 109 olive oil samples of 18 varieties from the only two primary suitable areas,and then systematically analyzed the quality and composition characteristics of samples.After that,the effects of different factors on the characterization of Chinese olive oils were evaluated.On this basis,the prediction and evaluation models of antioxidant capacity were constructed,and a series of chemometric methods were used to identify and evaluate the samples.The results could guide the selection of suitable varieties in different regions and offer valuable proposal for the production of Chinese high-quality olive oil.Firstly,this study has systematically analyzed the quality indices of 109 olive oil samples of 18 varieties from two primary suitable areas.The results showed that the quality index of109 samples,fatty acid profile of 106 samples,sterol content of 95 samples,and sterol profile of 105 samples met the requirements of GB/T 23347-2009 for extra virgin olive oil.The results indicated that Chinese olive oil industry has the potential to produce high-quality olive oil.Then,characteristic components in Chinese olive oils were comprehensive studied,and a generalized linear model was established to evaluate the effects of different factors.The results showed that the major tocopherol isomer in the samples was ?-tocopherol,and the total tocopherol content ranged from 109.2 to 504.4 mg/kg.Squalene content ranged from2098 to 14433 mg/kg.The major phenolic compounds in the samples were secoiridoids,with total phenol content ranging from 25.08 to 793.0 GAE mg/kg.The characteristics of Chinese olive oils was high content of squalene,medium content of tocopherols,and low content of phenolic compounds.The results of the generalized linear model showed that cultivar was the most important factor affecting the characteristic components in Chinese olive oils.Further,the characteristics of volatile compositions in all samples were analysed,and the effects of different factors were evaluated.The results showed that 33 kinds of volatile compounds were identified in the samples,including 10 kinds of alcohols,13 kinds of aldehydes,6 kinds of acids,2 kinds of esters,1 kind of ketone and 1 kind of oxygen-containing monoterpene.The volatiles of Chinese olive oil were mainly aldehydes,followed by alcohols.Except for the highest content of volatile in Ezhi 8 was(E)-2-hexen-1-ol,the highest content of volatile in the remaining samples was all(E)-2-hexenal.The characteristics of volatile compounds in Chinese olive oil was high amount of C6 aldehydes and C6 alcohols,while C5 compounds and esters were significantly lower than those from other countries.The results of the generalized linear model showed that cultivar and region were the most important factors affecting the volatile compositions in Chinese olive oil.Subsequently,this study analyzed the relationship between the composition characteristics and antioxidant properties of Chinese olive oil.The results showed that the oxidation induction time range of Chinese olive oil was from 4.97 to 28.86 h,and the DPPH,FRAP,ABTS and ORAC results were 14.65?221.62 ?mol TE/100 g,66.63?331.24 ?mol TE/100 g,88.72?600.39 ?mol TE/100 g and 32.27?631.75 ?mol TE/100 g,respectively.The oxidation induction time and free radical scavenging capacity of Chinese olive oil were roughly similar to those from other countries.Multiple regression analysis found that the oxidation stability of Chinese olive oil was positively correlated with the content of hydroxytyrosol derivatives,C18:1 and squalene,and negatively correlated with the content of phytosterols.The free radical scavenging capacity was related to hydroxytyrosol,tyrosol derivatives and phenol alcohols.The evaluation model of the free radical scavenging capacity of Chinese olive oil is Y = 0.370 ×(hydroxytyrosol derivatives)+ 0.308 ×(tyrosol derivatives)+ 0.169 ×(HT/Try)+ 0.153 ×(phenol alcohol).According to the evaluation model,the scores of Arbequina oils were generally low,while the scores of Coratina oils were relatively high.However,the model only reflected the capacity of scavenge free radicals,and it was necessary to explore a more suitable quality evaluation model.Finally,in order to screen out suitable cultivars in different regions,chemometrics was used to identify the cultivar and region,and evaluate the quality of Chinese olive oils.Artificial neural network was used to identify the olive oil samples of six cultivars collected from the two producing regions,and the least factors when the model accuracy rate was 100%were screened out.It was found that the olive cultivar can be fully identified by 7 indicators,and the region can be fully identified by 3 indicators.Linear discriminant analysis was used to verify the identification ability of the selected indicators,and it was found that the model's identification accuracy rate of the original cultivar was 98.0%,and the accuracy rate of the leave-one-out cross-validation method was 96.0%;the identification accuracy rate of the original region was 98.0%,and the correct rate of leave-one-out cross-validation method is92.0%.The overall effect was good.On the basis of considering factor analysis and the scavenge free radicals capacities,Coratina and Picholine were suitable cultivars in Longnan,and Coratina and Koroneiki were suitable cultivars in Xichang.In conclusion,this paper systematically analyzed the composition and antioxidant capacity of Chinese olive oils from the only two primary suitable areas,and used chemometric methods to establish models for the identification and evaluation the characteristics of the samples.The results provided valuable guidance for the establishment of Chinese olive oil database and the production of high-quality olive oil. |
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