Analysis of volatile components in post harvest bananas treated with short wave ultraviolet light based on GC-MS
Bananas (Musa spp.) are the fourth most consumed fruit in the world and the fifth largest fruit producer in China, with Guangdong, Guangxi, and Hainan being the main production areas. Bananas are rich in nutrients and contain various trace elements that the human body needs. After harvesting, they are not resistant to storage and are prone to decay and deterioration. Volatile components are important quality indicators for evaluating the freshness of fruits and vegetables such as bananas. Solid phase microextraction (SPME) has the advantages of no pollution, low cost, and simple and convenient operation, and is currently a commonly used pretreatment technique for the determination of volatile components in samples. The combined determination of volatile components in samples by SPME and GC-MS is a widely used model. To obtain the volatile components of the studied samples and accurately identify the chemical composition of the mixture, key technologies include appropriate extraction heads, extraction conditions, quality of mass spectrometry data obtained, rich mass spectrometry libraries, and good qualitative identification parameters. At present, there are many reports on the volatile components of bananas. Tao et al. used PDMS extraction heads to analyze and identify 39 volatile components in mature bananas; Zhu et al. used SPME-GC-MS to identify and analyze the volatile components of bananas at different maturity stages, and determined that there were mainly 41 volatile components in bananas at the yellow maturity stage; Shen et al. analyzed the volatile components in mature and immature bananas using SPME-GC-MS, compared the differences in chemical composition between the two, and identified 30 volatile components in mature bananas. In recent years, according to reports, the application of appropriate doses of short wave ultraviolet (UV-C) for the preservation of fruits and vegetables can enhance their defense systems, reduce damage from external factors, improve their quality, and prolong their storage time. Although there have been reports of using SPME-GC-MS to analyze the volatile components of bananas, there have been no studies on the differences in volatile components of bananas stored until the yellow ripening stage after UV-C treatment.

On the basis of optimizing the combination of orthogonal experimental design to find the optimal parameters for SPME extraction, this study will use MS-DIAL software to reduce the interference of overlapping peaks and background signals, identify the volatile components of bananas, and then compare the differences in volatile components of bananas after UV-C treatment through mathematical statistical analysis to evaluate the effect of UV-C treatment on the aroma of harvested bananas during storage.

This article selects the CAR/PDMS extraction head for SPME operation, and applies orthogonal experimental design to optimize the combination of SPME extraction conditions. The SPME extraction optimization conditions for the determination of volatile components in bananas are obtained as follows: ultrasound time of 20 minutes, sample size of 4.0g, and extraction temperature of 50 ℃. On this basis, by measuring the volatile components of bananas in the treatment group and the control group that had preservation effects after UV-C treatment, the experimental results showed that the metabolic pathways of the two groups of bananas changed. A total of 38 differential metabolic volatile components and 34 differential metabolic volatile components had their relative contents decreased, and 4 differential metabolic volatile components had their relative contents increased. The total ester content, main characteristic aroma components isoamyl acetate and isoamyl butyrate of bananas stored after UV-C treatment were higher than those of the control group bananas. Esters are the main volatile components and aroma components of mature banana flesh. Therefore, applying UV-C treatment to preserve bananas not only does not cause a decrease in the aroma components of bananas, but also benefits the aroma of bananas. generated, The results of this study can provide qualitative reference for SPME-GC-MS determination of volatile components in agricultural products and other foods, as well as reference for the aroma changes of fresh fruits after UV-C treatment. At present, research on the metabolic pathways of aroma components in bananas and other fruits, changes in volatile components during fruit storage and processing, and the physiological functions of corresponding genes and enzymes is not yet complete. The mechanism of the upregulation or downregulation of volatile components in bananas caused by UV-C treatment in this study still needs further exploration.