Study on variation of volatile components in Golden Passion Fruit at different development stages

Abstract:【Objective】Passion fruit (Passiflora coerulea Linn.) is a common fruit species in tropical and subtropical regions, and its pulp is rich in vitamins, amino acids, fatty acids, polyphenols and other nutrients. Due to its high nutritional value, it is crucial to investigate and evaluate the potential of pas-sion fruit as a functional food and active compound. The peel and pulp of passion fruit have economic value. Passion fruit has a strong aroma, with fruit flavor, sweet aroma and other flavors, which is the key raw material for juice beverage products. The peel of passion fruit can be used as a raw material for spices to provide products with higher added value. The aroma of passion fruit is one of the key features to evaluate its quality. In edible fruits, the production of volatiles is of additional significance because the volatile emissions are an indicator of quality and consumer preference. Therefore, it is important to explore the volatile components of Gold Passion Fruit (Passi floraedulis Sims.) to develop and utilize its value. This study was conducted to identify and comparatively analyze the volatile components of  Golden Passion Fruit at different development stages in order to provide theoretical references for the breeding of Golden Passion Fruit, aroma regulation, quality improvement and product development.【Methods】The volatile components of the peel and pulp of Golden Passion Fruit were detected by solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). Principal compo-nent analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were per-formed using SIMCA 14.1 software to reflect the distribution of different samples and separate different variable indicators. Screening of characteristic volatile components led to differences, ranking of vari- able importance indicators (VIP values), and selection of variables with VIP values ≥1 as significant dif- ferences. Origin 2019 was used to produce heat maps for cluster analysis.【Results】59 volatile compo-nents were identified in Golden Passion Fruit at different development stages, including esters, ketones,alcohols, aldehydes and terpenes. Aldehydes and alcohols were the main volatile components in Gold Passion Fruit peel. Esters and terpenes were the main volatile components in Gold Passion Fruit pulp. With the time increase of fruit development stage, the types of volatile components in the peel of Gold-en Passion Fruit tended to decrease, and the types of volatile components in the pulp tended to increase.The types of aldehydes in the peel were more than those in the pulp, with more types of aldehydes in the peel of young fruits. The number of ketones in the peel was significantly higher than that in the pulp, and the number of esters in the pulp was significantly higher than that in the peel. The content of esters in the pulp of Golden Passion Fruit reached the maximum at full ripeness. The types of volatile components in the peel and pulp of Golden Passion Fruit during the coloring period were significantly less than those during other development periods. Principal component analysis and orthogonal partial least squares discriminant analysis showed that the volatile components of Golden Passion Fruit peel and pulp were significantly different at different development stages. The volatile components in young fruit peel differed significantly from those at other development stages. Benzaldehyde, benzyl alcohol, (E)-2-nonenal and eucalyptol were the characteristic volatile components of Golden Passion Fruit peel.The contents of benzaldehyde, benzyl alcohol and (E)-2-nonenal in the peel of Golden Passion Fruit at the young fruit stage was significantly higher, while the contents of eucalyptol were significantly lower.The volatile components of Golden Passion Fruit pulp at full ripeness were obviously different from those at other development stages. Ethyl hexanoate, hexyl acetate, (E)-B-ocimene and cis-3-hexenyl ac-etate were the volatile components with significant difference. Validation tests of 200 permutations were performed for each of OPLS-DA models. The results showed that OPLS-DA models were not overfitted and statistically significant. The results of cluster analysis showed 4 distinct groups of flora, i.e., the pulp of fully ripe Golden Passion Fruit, the pulp of coloring stage to ripe stage, the peel of young fruit, and the peel of coloring stage to fully ripe stage. The difference in volatile components between fully ripe and other development stages of Golden Passion Fruit pulp was obvious, mainly due to the significant accumulation of esters and terpenoids at full ripeness. The results showed that these volatiles were important for aroma formation during ripening of Golden Passion Fruit, and the production of pas- sion fruit volatile components depended on fruit ripening, with most volatile components accumulating at the beginning of Golden Passion Fruit development and reaching a peak at fruit ripening.【Conclusion】The volatile components of Golden Passion Fruit at different development stages varied between peel and pulp. Ocimene could be regarded as a characteristic volatile component in the peel of Golden Passion Fruit at full maturity. Ethyl hexanoate, hexyl acetate, (E)-Β-ocimene and cis-3-hexenyl acetatecould be used as key volatile component characteristic indicators to distinguish fully ripe Golden Pas-sion Fruit. the results of this study can provide a reference for breeding, aroma regulation, quality im-provement and product development of Golden Passion Fruit.