Effects of cellulose nanofibrils treatment on antioxidant properties and aroma of fresh-cut apples

Horticultural products tend to deteriorate during postharvest storage and processing. In this study, cellulose nanofibers (CNFs) were prepared from wood to investigate the effects of CNF treatment on the storage quality, aroma composition, and antioxidant system of fresh-cut apple (Malus domestica) wedges. Compared with control treatment, CNF coating treatment significantly improved the appearance of apple wedges; reduced the decay rate of apple wedges; and delayed the decline in weight loss, firmness, and titratable acid during storage. Gas chromatography-mass spectrometry showed that CNF treatment could maintain the aroma components of apple wedges (stored for 4 days). Further investigations showed that CNF treatment increased the antioxidant system level and decreased reactive oxygen species content and membrane lipid peroxidation level of apple wedges. Overall, this study showed that CNF coating could effectively maintain the quality of fresh-cut apples during cold storage.

Characterization of key aroma compounds and regulation mechanism of aroma formation in local Binzi (Malus pumila × Malus asiatica) fruit

BACKGROUND

Volatile components are important secondary metabolites essential to fruit aroma quality, thus, in the past decades many studies have been extensively performed in clarifying fruit aroma formation. However, aroma components and biosynthesis in the fruit of Binzi (Malus pumila × Malus asiatica), an old local species with attractive aroma remain unknown.

RESULTS

We investigated two Binzi cultivars, 'Xiangbinzi' (here named high-fragrant Binzi, 'HFBZ') and 'Hulabin' (here named low-fragrant Binzi, 'LFBZ') by monitoring the variation of volatiles and their precursors by Gas Chromatography-Mass Spectrometer (GC-MS), as well as their related genes by RNA-seq during post-harvest ripening. We firstly confirmed that 'HFBZ' and 'LFBZ' fruit showed respiratory climacteric by detecting respiratory rate and ethylene emission during post-harvest; found that esters were the major aroma components in 'HFBZ' fruit, and hexyl 2-methylbutyrate was responsible for the 'fruity' note and most potent aroma component, followed by ethyl acetate, ethyl butanoate, (E)-2-hexenal, and 1-hexanol. Regarding aroma synthesis, fatty acid metabolism seemed to be more important than amino acid metabolism for aroma synthesis in 'HFBZ' fruit. Based on RNA-seq and quantitative reverse transcription PCR (RT-qPCR), LOX2a, LOX5a, ADH1, and AAT1 genes are pointed to the LOX pathway, which may play a vital role in the aroma formation of 'HFBZ' fruit.

CONCLUSION

Our study firstly investigated the aroma components and related genes of Binzi fruit, and provided an insight into the fragrant nature of Malus species.

Transcriptome and Metabolome Dynamics Explain Aroma Differences between Green and Red Prickly Ash Fruit

Green prickly ash (Zanthoxylum armatum) and red prickly ash (Zanthoxylum bungeanum) fruit have unique flavor and aroma characteristics that affect consumers' purchasing preferences. However, differences in aroma components and relevant biosynthesis genes have not been systematically investigated in green and red prickly ash. Here, through the analysis of differentially expressed genes (DEGs), differentially abundant metabolites, and terpenoid biosynthetic pathways, we characterize the different aroma components of green and red prickly ash fruits and identify key genes in the terpenoid biosynthetic pathway. Gas chromatography-mass spectrometry (GC-MS) was used to identify 41 terpenoids from green prickly ash and 61 terpenoids from red prickly ash. Piperitone was the most abundant terpenoid in green prickly ash fruit, whereas limonene was most abundant in red prickly ash. Intergroup correlation analysis and redundancy analysis showed that HDS2, MVK2, and MVD are key genes for terpenoid synthesis in green prickly ash, whereas FDPS2 and FDPS3 play an important role in the terpenoid synthesis of red prickly ash. In summary, differences in the composition and content of terpenoids are the main factors that cause differences in the aromas of green and red prickly ash, and these differences reflect contrasting expression patterns of terpenoid synthesis genes.