Citation
Md. Nor, Shahidah
(2021)
Growth and maturation processes of purple passion fruit (Passiflora edulis sims) through physical and metabolomics approaches.
Doctoral thesis, Universiti Putra Malaysia.
Abstract
The purple passion (Passiflora edulis SIMS) fruit has enormous potential to be
cultivated on a mass scale in Malaysia since it gains high demand in the global market.
This study is aimed to understand the growth and maturation process of passion fruit
through physical and metabolomics approaches for producing high quality fruit for
fresh fruit and varieties of industries. Growth and development of passion fruit were
tracked starting from 7 days after anthesis (DAA) until the fruit detached from the plant.
The first study was conducted to establish the fruit optimal harvesting stage. Logistic
model showed all physical traits of passion fruit fitted well with single sigmoid curve
with high regression coefficient (R2) around 0.984-0.992. The anatomical study showed
that passion fruit have three distinct growth phases; stage 1 (S1) (0-7 DAA), stage 2
(S2) (14-28 DAA) and stage 3 (S3) (35-63 DAA). Purple passion fruit obtained
maturity at 49 DAA and ripened at 56 DAA. The S3 phase was investigated intensively
in studies 2 and 3 because it is a vital period for maturation and ripening. In the second
and third studies, metabolomics approaches have been implemented in studying the
dispersion of metabolites during maturation and ripening process. In the study 2, juice
and seed were subjected to 1H NMR analysis as both compartments play significant
role in fruit eating quality. Around 30 and 32 metabolites were found in juice and seed,
respectively. Result showed the primary metabolites dominating both compartments
consist of sugar (glucose, sucrose, fructose), organic acid (tartaric acid, citric acid,
malic acid) and amino acid (lysine, threonine, methionine, leucine) while secondary
metabolites present as minor compounds (chlorogenic acid, epicatechin and
phenylacetic acid). Segregating the metabolites using principal component analysis
(PCA) and partial least square discriminant analysis (PLS-DA) have outlined how the
metabolites in both compartments changed dynamically throughout the maturation and
ripening process. Variable importance in the projection (VIP) has sorted 13 and 18
metabolites as highly influential metabolites in juice and seed. Glycolysis, TCA cycle,
shikimate pathway, ethylene and polyamine were detected as important biochemical
pathways that were responsible for the fruit's maturation and ripening. The third study
analysed juice, seed and peel since all fruit compartments have equal benefits to be
exploited as industrial products. Result showed that each fruit compartments have
different secondary metabolites contents correlated with their antioxidant activity.
During ripening, β-carotene and chlorophyll pigments degraded while anthocyanin
accumulated, resulting peel in a deep purple. The peel was abundant with different
types of phenolic acid (chlorogenic acid, caffeic acid and its derivatives) and flavonoid
components (isorientin, rutinoside and vitexin-2''-O-rhamnoside) possessed the highest
antioxidant activity determined by FRAP (732.91- 1089.61 μmol TE. 100 g-1 FW),
ABTS (62.34-70.10 μmol TE. g-1 FW) and DPPH (52.362- 67.66 μmol TE. g-1 FW)
as compared to seed and juice. All passion fruit compartments should be completely
exploited for fresh consumption and product manufacturing. Hence, herein a
comprehensive view of passion fruit growth and development may benefit Malaysia's
agriculture and processing industries.
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