Quality Assessment of Five Mono-cultivar Virgin Olive Oils Produced in Longnan (China) from 2013 to 2017.

The aim of this work was to evaluate the quality of the five mono-cultivar (Frantoio, Leccino, Picholine, Coratina and Ezhi-8) virgin olive oils (Mc-VOOs) produced in Longnan (China) from 2013 to 2017 through analysing the organoleptic quality, physicochemical properties, phenolic contents, antioxidant activity and fatty acid composition. The leading principal components for assessing the quality of Mc-VOOs were extracted by principal component analysis (PCA). The results indicated that the five Mc-VOOs showed obvious differences (p < 0.05) in flavour and substance composition with the variation of cultivar and production year; however, the same cultivar of VOO displayed certain homogeneity in five consecutive years of assessment. The five Mc-VOOs were rich in phenolic compounds and unsaturated fatty acids such as oleic acid. The quality of VOO was mainly determined by the genetic characteristics of olive cultivar, meanwhile, fruit maturity, soil and climate factors also affected its quality. The content of phenolic compound, DPPH· scavenging rate, proportion of unsaturated fatty acids and iodine value of Coratina were the highest, on the contrary, Ezhi-8 was the lowest in general. The results of PCA showed that the five leading principal components to evaluate the quality of Mc-VOOs were oleic acid, linoleic acid, acid value, total phenol and trace components (such as C20:1 and squalene) successively. In conclusion, the five Mc-VOOs from Longnan show excellent quality and have certain uniformity in different production years.

Extract of Syringa oblata: A new biocontrol agent against tobacco bacterial wilt caused by Ralstonia solanacearum.

Ralstonia solanacearum causes serious wilt disease in tobacco. To effectively control this disease, the antibacterial activity of 95% ethanol extracts from the flower buds of Syringa oblata was examined. Based on GC-MS analysis and an inhibition experiment against R. solanacearum, the main antibacterial component is eugenol. We further determined the effect of eugenol on the physiology, biochemistry, and cellular morphology of R. solanacearum. The results showed that eugenol can destroy wilt bacteria, leading to the disappearance of flagella, the leakage of contents, and the appearance of a cavity. SDS-PAGE showed that eugenol decreased protein content in R. solanacearum, reduced medium carbohydrate utilization, and inhibited CAT and SDH activity. The above results showed that eugenol had a significant inhibitory effect on R. solanacearum and this component has the potential to prevent tobacco bacterial wilt.