Effect of post-harvest cold plasma treatment on physicochemical properties and inactivation of Penicillium digitatum in Persian lime fruit

Cold atmospheric plasma (CAP) treatment is used in this study to inactivate Penicillium digitatum in lime fruit at post-harvest. Limes were inoculated manually withP. digitatum spore (106 CFU/fruit) and then were treated with CAP at 30, 60, 90, and 120 s and compared with untreated samples. The results showed that increasing the exposure time of CAP reduced spores to less than 7 CFU/fruit in 120 s on the lime peel. In the treated samples, antioxidant activity had an upward trend. In addition, phenolic compounds, vitamin C, density, soluble solid content (SSC), color, and pH of the lime juice were increased (P < 0.05). Compared to the control sample, no significant changes were observed in the juice yield percentage, texture, acidity, chlorophyll, and carotenoid (P > 0.05). The best exposure for CAP treatment was 60 s since it increased phenolic compounds, antioxidant activity, and vitamin C content in the lime juice.

GC-MS study of changes in polar/mid-polar and volatile compounds in Persian lime (Citrus latifolia) during fruit growth

BACKGROUND

Citrus fruits possess a high content of bioactive compounds whose changes during fruit maturation have not been studied in depth. Fruits were sampled from week 1, after fruit onset (7 days after flowering), to week 14. Volatile compounds isolated by headspace-solid-phase microextraction and polar extracts from all samples were analyzed by gas chromatography-mass spectrometry.

RESULTS

The relative abundance of 107 identified metabolites allowed differences among samples at different stages of fruit growth to be established. Principal component analysis showed a clear discrimination among samples, and analysis of variance revealed significant differences in 94 out of the 107 metabolites. Among total volatiles, monoterpenes increased their relative abundance from 86% to 94% during fruit growth, d-limonene, γ-terpinene and β-pinene being the most abundant; conversely, sesquiterpenes decreased from 11.5% to 2.8%, β-bisabolene and α-bergamotene being the most concentrated. Sugars, in general, exhibited a gradual increase in abundance, reaching a maximum between weeks 9 and 12. Citric and malic acids, representing approximately 90% of the total identified carboxylic acids, reached a maximum concentration at commercial maturity (week 14).

CONCLUSION

Of the 107 tentatively identified metabolites during Persian lime growth, sugars, carboxylic acids, and volatiles were those that experienced more significant changes and more clearly created differences among fruit growth stages. © 2018 Society of Chemical Industry.

Targeted Analysis of the Concentration Changes of Phenolic Compounds in Persian Lime (Citrus latifolia) during Fruit Growth

Citrus fruits possess a high content of phenolic compounds; however, few studies have focused on the changes occurring during fruit growth. In this study, the changes in the concentration of 20 flavonoids, 4 phenolic acids, and their biosynthetic precursors phenylalanine and tyrosine have been evaluated during fruit maturation (14 weeks). Extracts from all samples, obtained by ultrasound assistance, were analyzed by liquid chromatography coupled to tandem mass spectrometry with a triple quad system (LC-QqQ MS/MS). In general, the concentration of flavanones, which represented over 70% of the studied phenols, and flavones increased during fruit growth, reaching their maximum concentration around week 12. In general, flavanols and phenolic acids exhibited their maximum concentration at week 5 and then decreasing significantly during the rest of maturation. Phenylalanine and tyrosine showed a sinuous behavior during fruit growth. Partial least-squares showed a clear differentiation among fruits belonging to different maturation stages, coumaric acid derivatives being the most influential variables on the projection.

Changes in the composition of the polar fraction of Persian lime (Citrus latifolia) during fruit growth by LC-QTOF MS/MS analysis

Citrus possess a large number of bioactive compounds mainly studied in ripe fruits. Few studies have focused on evolution of metabolites during fruit growth. In this study, fruits were sampled from weeks 1-14 of the ripening process. Polar extracts were obtained from all collected samples and analysed by liquid chromatography-tandem mass spectrometry. Analysis of variance applied to the dataset indicated that the relative concentration of 394 out of 423 molecular entities changed significantly during maturation. Principal component analysis showed a clear separation among samples from different weeks and revealed the main compounds responsible for differentiation. Additionally, 72 metabolites were tentatively identified and changes in their relative concentration during growth were individually analysed. The observed trends in relative concentrations of representative metabolites during the growth process are discussed.