Study of Nanoemulsions of Grapefruit Oil and their role in controlling Postharvest Fungus
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Date
2021
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Punjab Agricultural University, Ludhiana
Abstract
Among therapeutic and fragrant plant botanicals, essential oils are charming consideration for
research, attributable to their huge scope of bioactivities. Utilization of essential oils as
antimicrobial agents in fields of food conservation, makeup, agribusiness, drugs and so on is well
established. However, their use for development of ecofriendly agrochemicals such as
nanoformulations, is yet to be explored. Kinnow, a Citrus crop is hybrid of Citrus deliciosa and
Citrus nobilis is grown mainly in Punjab region of India and Pakistan. Its high fruit quality, better
juice content and bright orange color makes it the major consumed citrus crop. But owing to
mesophillic fungal attacks, the kinnow crop experience post harvest losses leading to nutritional
loss and financial losses to farmers. Penicillium digitatum is the most prominent one and majorly
contributes to the postharvest losses. Apart from medicinal plants, certain fruit and vegetable
wastes of food processing industry also possess potent chemical compounds with antimicrobial
properties. Grapefruit (Citrus paradisi or C. paradisi) is a subtropical citrus hybrid originated in
Barbados with vast antimicrobial properties. The present study was therefore, aimed to develop
grapefruit essential oil nanoemulsions to explore its antifungal potential against Penicillium
digitatum. Grapefruit EO was extracted using Clevenger-type apparatus with 0.25% essential oil
yield. Compositional analysis of extracted EO by GC-MS revealed presence of 𝜶-limonene
(83.73%) as the major compound. Nanoemulsions were prepared by mixing grapefruit essential oil
and surfactant (Tween 80) in different ratios (v/v) viz 1:0.5, 1:1, 1:2 and 1:3 by using bath and
probe sonicator. The droplet size of nanoemulsions formulated using probe and bath sonication
ranges from 60nm -190nm and 120-400 nm respectively. The polydispersity index (PDI) of
nanoemulsions formulated using probe and bath sonication ranges from ranges from 0.22-0.26 and
0.24-0.276 respectively, indicating homogeneity produced by both the techniques. All the
nanoemulsions formulated possessed the pH in 5-7.04 and the electrical conductivity more than
30μS cm-1. The nanoemulsions with 1:1 O:S ratio (20 min) exhibited the optimum droplet
diameter and PDI with maximum stability. Antimycotic potential of grapefruit essential oil and its
nanoemulsions [1:1 O:S ratio (20 min)] was evaluated using poisoned food technique which
revealed the best efficacy of the naoemulsion against P. digitatum (88.6%) as compared to pure
grapefruit peel essential oil (76.6%) treatment. Optical microscopy of grapefruit peel essential oil
and nanoemulsion treated fungus also supplemented the antifunagal activity data. The optical
micrographs indicated change in morphology with further decrease in hyphal diameter in treated
grapefruit peel essential oil nanoemulsions. Further studies need to be conducted to explore the
potential of grapefruit peel essential oil nanoemulsions for enhancing shelf life of kinnow fruits.
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Dudeja, Isha (2021). Study of Nanoemulsions of Grapefruit Oil and their role in controlling Postharvest Fungus (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.