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Application of edible coatings to
maintain postharvest quality of
pomegranate fruit
Presented by
Tatenda Kawhena
Advisors : Prof. U.L Opara, Prof. O.A Fawole & Dr A.A Tsige
Internal decay External decay
ShrivellingChilling injury Scalding
Major causes of postharvest quality losses
Mould
3
Application of edible coatings
An alternative postharvest strategy
Volatile compounds aroma
Coating layer
Moisture
Gases (O2, CO2,
Ethylene)
Fresh produce(Water, Carbohydrates,
Proteins, Pigments and Aroma)
Adapted from Raghav, Agarwal and Saini, 2016
4
Types of edible coatings
5
Bioactive edible coatings
Active
compounds
Examples
Antimicrobials Organic acids, metals (silver), Bacteriocins (nisin, lacticin) and
enzymes (lysozyme, lactoperoxidase), peptides and natural
antimicrobials (spices and essentials oil)
Antioxidants Ascorbic acid, carotenoids, and flavonoids
Nutraceuticals Vitamins, phytosterols, lutein, fatty acids and lycopene
Flavours Thymol, geraniol, Limonene and β-unsaturated aldehydes
((E)-2-hexenal, (E)-cinnamaldehyde, citral)
Edible coatings can be utilized as encapsulating matrices to many bioactive
compounds that improve the quality of food products
6
Soluble chitosan
Gum arabic
Lemongrass oil
Pomegranate peel extract
Our approach
Edible coatings
Active ingredients
Pomegranate(cv. Wonderful)
Bioactive edible coatings
Endura-Fresh 6100
OR
7
Chitosan(1 g) 100 ml distilled water
Glycerol (1 %)
Tween 80 (0.05 %)
Chitosan
(1 %)
Preparation of edible coatings
Gum arabic
(1.5 g)
Homogenization
2 500 r.p.m. for 30 min
magnetic stirring
(90 ºC)-45 min
100 ml distilled water
Gum arabic
(1.5 %)Tween 80 (0.05 %)
Glycerol (1 %)
Lemongrass oil
(0.5%)magnetic stirring
(90 ºC)-45 min
Pomegranate peel
extract (1 %)
±
8
Storage conditions: 5 ± 0.7 °C and 95 ± 2 % RH
Evaluation period : 2 w, 4 w, 6 w, 8 w, 3 mon and 4 mon
Quality assessments of fruit were carried out prior to packaging
and storage as a baseline on day 0
CH CH + PP
GA
CH + LM
GA + LM GA + PP UNCOATED
CONTROL
Storage conditions and evaluation periods
CH + LM+ PP
GA + LM + PP
GA = Gum arabic
CH = Chitosan
LM = Lemongrass oil
PP = Pomegranate peel extract
LAC-RESIN
9
Storage and packaging of fruit
Phytosanitization(600 ppm Fludioxinil solution
for 10 min) Dipping (1 min) Drying –Growth/Humidity chamber
(20 ± 2 °C and 65 ± 5 % RH)
Edible coating
(5 L)
1 2
4
3
5
Packaging10 fruit/box, 10 boxes per treatment
SIMULATED STORAGE5 ± 0.7 °C and 95 ± 2 % RH
10
Postharvest evaluation of fruit
Parameter Relevance
Physical properties Weight loss Moisture loss in fruit
Colour Visual appeal/appearance
Headspace gas
composition
Respiration rate (CO2
production)
Fermentation/off flavour
Chemical
properties
Titratable acidity, total
soluble solids and pH
Sugar, acid and overall flavour
Results
12
Cumulative weight loss
0
0,962
2,934
4,812
0
0,677
3,81
8,402
0
0,396
1,82,901
0
1
2
3
4
5
6
7
8
9
0 2 4 6
%
Storage duration (weeks)
LAC-RESIN CONTROL GA + LM + PP
GA = Gum arabic
LM = Lemongrass oil
PP = Pomegranate peel extract
13
Scanning Electron Micrographs
Uncoated peel
Open lenticels
CHITOSAN (2 Weeks)
GUM ARABIC (2 Weeks @ 5 ºC)
Film tearing off
Not evenly spread
CLOSED LENTICEL
Lenticel NOT
FULLY CLOSED
UNTREATED CONTROL
Lac-resin wax
FUNGI HYPHAE ON FRUIT SURFACE
CRACK ON LENTICEL
16
15,315,6333
16,2333
15,2
14,8333
13,4667
15
14,2667
13,2667
13,8
13,1
14,166713,9
12,6
13,3667
10
11
12
13
14
15
16
17
2 4 6
˚Bri
x
Storage duration (weeks)
GA GA + LM GA + LM + PP LAC-RESIN WAX CONTROL
GA = Gum arabic
LM = Lemongrass oil
PP = Pomegranate peel extract
How ‘sweet’ were the arils?
17
0,8
0,9
1
1,1
1,2
1,3
1,4
2 4 6
Citri
c ac
id
(g/1
00g)
GA GA + LM + PP LAC-RESIN WAX CONTROL
GA = Gum arabic
LM = Lemongrass oil
PP = Pomegranate peel extract
How ‘bitter’ were the arils?
18
Lac-resin waxChitosan + LM + PP extract
Fruit appearance (8 weeks + 5 days shelf life)
1
0 = without scald; 1 = 1-25 %; 2 = 25-50 %; 3 = 50-75 %; 4 = 100 %
2 3 4
Scalding and chilling injury
20
Scalding and chilling injury
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0,4
0 2 4 6
Chill
ing
inju
ry (
1-5
)
Storage duration (months)
CH CH + LM CH + PP CH + LM + PP
LAC-RESIN CONTROL GA GA + LM
GA + PP GA + LM + PP
0
0,1
0,2
0,3
0,4
0,5
0,6
0 2 4 6
Sca
ldin
g (1
-5)
Storage duration (months)
CH CH + LM CH + PP CH + LM + PPLAC-RESIN CONTROL GA GA + LMGA + PP GA + LM + PP
SCALDING CHILLING INJURY
21
Mould development
0
0,05
0,1
0,15
0,2
0,25
0 2 4 6
(1-5
)
Storage duration (months)
CH CH + LM CH + PP CH + LM + PP LAC-RESIN
CONTROL GA GA + LM GA + PP GA + LM + PP0 = without mould; 1 = 1-25 %; 2 = 25-50 %; 3 = 50-
75 %; 4 = 100 %
3
2
1
22
Fruit applied with Gum Arabic + lemon grass oil + pomegranate peel extract (GA+LM+PP)
recorded the least cumulative weight loss (2.9 %) after 6 weeks of cold storage at 5 ºC
compared with Endura-Fresh 6100 (4.8 %). This may have financial implication on exported fruit,
as fruit is marketed on weight basis
Fruit coated with chitosan and gum arabic with or without lemongrass oil (LM) and/or
pomegranate peel extract (PP) developed the least incidence of scald (50 % for uncoated and 0 %
for GA+LM+PP) and chilling injury (2.5 % for CH+LM+PP and UNCOATED-34 %)
Mould incidence was mostly prevalent in uncoated control and Endura-Fresh 6100 coated fruit
(11 % for UNCOATED and 0 % for GA+LM, GA+PP, CH+LM & CH+LM+PP)
We continue to investigate the effect of various coating formulations on postharvest quality of
pomegranate fruit. In 2019/2020 season, we will explore the possibility of eliminating use of liners
inside packaging with the goal to minimize cost and provide a biodegradable packaging system for
postharvest handling of pomegranates
Summary and future prospects
Acknowledgements
This work is based on the research supported by the South African Research Chairs Initiative (SARChI) of the
Departments of Science and Technology and National Research Foundation
We thank Pomegranate Association of South Africa for research and bursary funding
Prof. Umezuruike Linus Opara, SARChI Postharvest Technology, Department of Horticultural Science
Prof. Olaniyi Amos Fawole, SARChI Postharvest Technology, Department of Horticultural Science
Dr Alemayehu Ambaw, SARChI Postharvest Technology, Department of Horticultural Science
DISCLAIMER : Information shared in this presentation is for research purposes and is subject to change during the course of the PhD study. Under no
circumstances shall we be held accountable for any damage or loss of any kind incurred in the adoption of the findings communicated
John 3: 16