Effect of novel coconut oil and beeswax edible coating on postharvest quality of lemon at ambient storage

Journal Pre-proof Effect of novel coconut oil and beeswax edible coating on postharvest quality of lemon at ambient storage Taslima Ayesha Aktar Nasrin, Md. Atiqur Rahman, Most Sadia Arfin, Md. Nazrul Islam, Md. Azmat Ullah PII:

S2666-1543(19)30019-5

DOI:

https://doi.org/10.1016/j.jafr.2019.100019

Reference:

JAFR 100019

To appear in:

Journal of Agriculture and Food Research

Received Date: 29 October 2019 Revised Date:

22 December 2019

Accepted Date: 22 December 2019

Please cite this article as: T.A. Aktar Nasrin, M.A. Rahman, M.S. Arfin, M.N. Islam, M.A. Ullah, Effect of novel coconut oil and beeswax edible coating on postharvest quality of lemon at ambient storage, Journal of Agriculture and Food Research, https://doi.org/10.1016/j.jafr.2019.100019. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 The Author(s). Published by Elsevier B.V.

Applying edible (coconut oil only or mixed with beeswax) coating and MAP

A1B1 A2B1 A3B1 A4B1 A1B2 A2B2 A3B2 A4B2

30

Without coating & MAP

Weight loss (%)

25 20 15 10 5 0 0

3 6 9 12 15 Storage period (days)

18

A1B1=Uncoated & kept open, A2B1= Coconut oil coated & kept open, A3B1= Coconut oil and beeswax (90:10) coated & kept open, A4B1= Coconut oil and beeswax (80:20) coated & kept open,A1B2=Uncoated & kept in MAP, A2B2= Coconut oil coated & kept in MAP, A3B2= Coconut oil and beeswax (90:10) coated & kept in MAP, A4B2= Coconut oil and beeswax (80:20) coated & kept in MAP. Vertical bars indicate standard deviation.

Coating and MAP restrict movement of H2O, O2, CO2, N2, C2H4 Edible coated & MAP at 18th day of storage

1

Effect of novel coconut oil and beeswax edible coating on postharvest

2

quality of lemon at ambient storage

3 4

Taslima Ayesha Aktar Nasrina*, Md. Atiqur Rahmana, Most Sadia Arfina, Md. Nazrul Islama, and Md. Azmat

5

Ullaha

6

a

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Bangladesh Agricultural Research Institute, Gazipur-170, Bangladesh.

8

*

Postharvest technology section, Horticulture Research Centre,

Corresponding author: [email protected] ; [email protected]

9 10 11

ABSTRACT

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An experiment was conducted to assess the influence of coconut oil and beeswax coating and

13

modified atmospheric packaging (MAP) on postharvest storage quality of lemon at ambient storage.

14

Sorted lemons were washed with water; fruit surface water was removed by using fan and then coated

15

with coconut oil and beeswax mixture (90:10 or 80:20) or only coconut oil. After coating, lemons were

16

kept open in crates or in MAP and stored at ambient condition (21±2°C and 50±5% RH). The

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effectiveness of edible coating and MAP in extending the shelf life of lemon with quality was

18

evaluated by determining weight loss, respiration rate, ethylene production rate, firmness, shrinkage,

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yellowing, decay incidence, total soluble solid (TSS), pH, ascorbic acid, juice content and also

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organoleptic quality were assessed periodically during storage. The results revealed that coconut oil

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only and mixtures with beeswax (both formulations) coating especially with MAP had immense effect

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on retaining green colour, reducing respiration, ethylene production, weight loss and shriveling,

23

preserving firmness and moisture content of lemon throughout the storage.

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Key wards: Coconut oil; beeswax; respiration rate; hue angle; juice content; firmness

26 27

1. Introduction

1

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Lemon (Citrus limon) is an important horticultural crop for their unique flavour and acidity and a

29

good source of functional compounds like vitamin C, phenols and flavonoids. Due to non-climacteric

30

fruits, lemon produce low CO2 and ethylene that helps not to experience major softening or

31

compositional changes during storage and transport [1]. But the major problems limit postharvest life

32

of lemon is weight loss results mainly from transpiration and respiration and yellowing of peel colour

33

[2]. When excessive water loss occurs in lemons, the ethylene biosynthesis will be increased that

34

stimulate chlorophyllase which helps to break down chlorophyll and pectin methyl esterase resulting

35

in soften and changing of green colour to yellow. Shelf life of citrus can be increased through

36

controlling the rate of transpiration and respiration, skin colour and microbial infection [3]. These

37

objectives can be reached to some extent by the use of growth regulators, edible coating, waxing, and

38

storage at low temperature, use of fungicide, chemical application, oil coating, irradiation and

39

different types of packing material as postharvest treatments [4, 5]. The demand of Bangladeshi

40

farmers and traders is the extension of the shelf life of lemon with quality retaining green colour.

41

Therefore, low cost technologies that should be easily available, economically viable and feasible

42

considering health and environmental issues need to be standardized. Among the different low cost

43

technologies, the application of coating to fruit has been associated with growing attention as these

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coating protect perishables from deterioration by reducing transpiration and respiration, improving

45

textural quality, retaining colour and volatile flavour compounds and reducing microbial growth [6].

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Edible coating of fruits with pure coconut oil has gaining interest for its anti-ageing properties by

47

controlling respiration rate, transpiration rate and binding of the ethylene biosynthesis process.

48

Coconut oil is a natural food product rich in lauric acid. There is an evidence that a part of this acid

49

converts endogenously to monolaurin that is known to possess a broad spectrum of antiviral,

50

antibacterial and antifungal activities [7]. Coconut oil coating closed the opening of stomata and

51

lenticels thereby, reducing the transpiration and respiration rate and also reduce microbial activity [8].

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Citrus commercial coatings are generically known as waxes due to the fact that composition of

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initial formulations was based on paraffin wax or a combination of various other waxes such as

54

beeswax or carnauba. Their main purpose is to reduce fruit weight loss, shrinkage and improve

55

appearance, but they can also reduce the incidence of chilling injury or other citrus rind disorders [9, 2

56

10]. Citrus Wax (wood resins18%, Imazalil 0.3%, Thiabendazloe 0.5%) coating significantly (P≤

57

0.05) reduced physiological weight loss, increased shelf life and maintained the quality of fruits.

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Besides, this coating maintained relatively higher levels of vitamin C content, flavor and fruit

59

firmness; prevented disease attack; and improved juice recovery of lime fruits compared with control

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[11]. Bisen et al [8] reported that

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significantly and positively influenced by coconut oil coating up to 18 days of storage at ambient

62

condition (25–30 °C and 60–70% RH). Hence, pure coconut oil coating delay the appearance of

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moulds up to 18 days of storage and is useful for extending their shelf life with quality. Bisen and

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Pandey [3] found that coconut oil and liquid paraffin coating of Kagzi lime was found to be effective

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in keeping natural light green colour of fruits up to 24 days of storage, and was acceptable to

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consumers. This coating helps to retardation of senescence process and less degradation in the colour

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pigments (chlorophyll), which slowed the change in external colour under these treatments. However,

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according to our knowledge, there is very little study about the incorporation of natural biologically

69

active compounds in the beeswax coating, separately or as a component of some natural product as

70

the coconut oil is.

the physical and chemical parameters of kagzi lime

were

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Use of low density polyethylene (LDPE) bag for storage and transport of citrus have potentiality

72

by modifying the level of CO2 and O2 around fruit inside bag [9]. The limits for the development of

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MAP, fruit damage may occur due to high concentration of CO2 or low O2, condensation of water

74

inside bag. One strategy to decrease the risk of developing of injurious gas concentrations is to make

75

holes in bag that helps to minimise transpiration, fruit firmness and eating quality of citrus [12].

76

Keeping these in views, in the present study, a homogeneous coating has been produced from the

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mixture of melted beeswax and coconut oil or only coconut oil applied on fresh lemon and kept open

78

in crates or in MAP for prolonging postharvest quality of lemon retaining green colour at ambient

79

condition.

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2. Materials and methods

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2.1. Material

3

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Lemon (Citrus limon var.) was collected from the field of one progressive farmer of Jamalpur district,

84

Bangladesh. Lemon was harvested based on maturity, uniformity of size and absence of physical

85

damage. After harvest, it was directly brought to the laboratory. Chemicals used in this study were

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research grade. Beeswax (Origin: New Delhi, India; Molecular mass: 677.2215; Melting point 61-65°;

87

Acid value 5-8; Ester value 80-95; Total volatile matter max. 1%). Coconut oil (Origin: India; White

88

colour at solid form but colourless above 30°C; melting point 25° C; Smoking point: 177 °C).

89

2.2. Edible coating formulations

90

Coconut oil and beeswax (coconut oil 90 mL and beeswax 10g or coconut oil 80 mL and beeswax 20g)

91

were taken into beaker, put and stirred into a hot water bath until melt and make clear mixture. Three

92

types of coating were used such as a.100% coconut oil, b. coconut oil and beeswax mixture (90:10), c. coconut

93

oil and beeswax mixture (80:20). Lemons were divided into 4 lots, 1 lot lemons were without coating,

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2nd lot lemons were coated with 100% coconut oil, 3rd lot lemons were coated with coconut oil and

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beeswax mixture (90:10), and 4 lot lemons were coated with coconut oil and beeswax mixture (80:20). Half

96

of lemons from each lot were kept open in plastic crates and half were kept in MAP (0.5% perforated LDPE

97

bag). The coating was applied carefully on the fruit skin by a soft and clean brush. Lemons kept open in

98

crates or into MAP were stored at ambient condition (21±2°C and 50±5% RH). Measurements on

99

various physical and chemical attributes were done at the day of experiment setting and on 3rd, 6th, 9th,

100

12th, 15th and 18th day of storage. From each replication 10 fruits were kept separately for weight loss

101

and colour change measurement throughout the storage period.

102

2.3. Ethylene production and respiration rate measurement

st

th

103

For the measurement of respiration and ethylene production rate of lemon, five fruits per

104

replication were kept into 1000 ml sealed containers containing septa up to 2 h (incubation time) at

105

ambient condition (21±2°C). Then one ml gas was taken from the container using syringe and

106

examined by gas analyzer (CO2/O2 gas analyzer, Quantek Instrument, Model No. 902D, USA) for

107

respiration rate measurement. Syringe of ethylene gas analyzer (Ethylene Spy, Model No. ES100) was

108

pushed to the head space of the container through septa and amount of C2H4 gas was measured in

109

ppm. Finally, respiration and ethylene production rate was determined by fruit volume and weight,

110

gas volume in the container and incubation time [13]. 4

111

2.4. Measurement of fruit firmness

112

Firmness was analyzed by Fruit Texture Analyzer (GUSS, Model Number: GS-25, SA). An 8 mm

113

dia. flat end probe was pushed to a depth of 3 mm into lemon (same position of each sample) at 5 mm

114

per sec speed. The utmost penetration force was used as firmness value of lemon in Newton. Three

115

lemons (two opposite locations for each) from each replication were analyzed and the mean value was

116

used.

117

2.5. Measurements of surface colour

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External colour of lemon was evaluated with a Chroma Meter (Model CR-400, Minolta Corp.,

119

Japan) based on CIE (L*a*b*). L* is lightness whereas a* and b* values were transformed to chroma

120

(c) and hue angle (h°) automatically in this Chroma meter. Before measurement, calibration was done

121

using supplied white plate.

122

2.6. Weight loss measurement

123

Initial weight of 10 fruits from each replication was taken immediately after treatment and then 3

124

days interval throughout storage time. It was calculated by the weight difference between initial and

125

specific time interval divided by initial weight and finally denoted by percentage.

126

2.7. Ascorbic acid, pH, titratable acidity and total soluble solids (TSS) determination

127

The ascorbic acid content and titratable acidity of lemon were analyzed according to AOAC [14].

128

TSS of lemon juice was determined by using refractometer and pH was assessed by pH meter

129

(HANNA Instrument Inc, pH-211; Microprocessor, pH Meter, Italy).

130

2.8. Juice content

131

Juice content was measured by the weight of juice extracted from 5 fruits divided by total weight

132

of five fruits and finally expressed as percentage.

133

2.9. Diseases incidence

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All fruits in each treatment were examined for microbial decay in naked eye by 3 investigators

135

including pathologist during the storage. Lemon showing any symptoms of microbial incidence was

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marked as decayed. Decay incidence was calculated as the number of decayed lemons divided by total

137

number of fruits in each replication.

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2.10. Shrinkage and yellowing 5

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Lemon showing at least 10% area of skin was wrinkled or shrinked marked as shrinked fruit. Fruit

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shrinkage was calculated as the number of shrinked or wrinkled lemons divided by total number of

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fruits. Lemon showing at least 10% area of skin was turned into yellow marked as yellow fruit.

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Yellowing of fruits was calculated as the number of yellow colour lemons divided by total number of

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lemons. Both were finally expressed as percentage.

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2.11. Sensory quality

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Sensory quality of lemon was evaluated at 6th, 9th and 18th day of storage. Sensory evaluation,

146

based on visual appeals on colour, flavour, texture and overall acceptability was conducted. Nine-

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point unstructured scale ranging from 1 (dislike extremely) to 9 (like extremely) was used to evaluate

148

these sensory parameters [15]. An average score of 4.5 was considered the limit for consumer

149

acceptability. Sensory evaluation was performed by a panel of judges consisting of ten scientific

150

personnel including both male and female members.

151

2.12. Statistical analysis

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A completely randomized design (CRD) was done with three replication for each experiment and

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mean ± standard deviation was shown. Analysis of variance (ANOVA) was done according to the

154

procedures of MSTAT-C software. Comparison among data was performed using Duncan’s Multiple

155

Range Test (DMRT) (p˂0.05).

156 157

3. Results and Discussion

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3.1. Respiration rate

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Fig.1 illustrates the effect of edible coating and MAP on the respiration rate of lemon. Initial

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respiration rate of lemon was 21.17mg.kg-1.h-1 and it was reduced sharply up to 3rd day of storage in

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all treatment then increased again in some treatments. Respiration rate of coated lemon was increased

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slightly throughout the storage period but after 6th day of storage, respiration rate was increased

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significantly in uncoated open lemons. Respiration rate in uncoated lemon open or in MAP was

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maximum and it was around 18.5mg.kg-1.h-1 at 18th day of storage. Another important observation was

165

noticed from the study that respiration rate of all treatments was increased with the change of lemon

6

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peel colour from green to yellow during storage period. Ladaniya [16] reported in his book named

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citrus fruits: biology, technology and evaluation that respiration rate of lemons at 25°C is in the range

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from 20 to 28 mg. kg-1.h-1. Wounding, rotting and severe shrivelling of citrus fruits stimulate

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respiration and ethylene production [16]. Respiration and ethylene production was higher when lime

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became yellow from green during ambient storage.

Respiration rate (CO2 mg kg-1 h-1)

25

A1B1 A2B1 A3B1 A4B1 A1B2 A2B2 A3B2 A4B2

20

15

10 0

3

171

6 9 12 Storage period (days)

15

18

172 173 174 175 176 177

Fig.1. Respiration rate of lemon influenced by edible coating and MAP stored at ambient condition.

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3.2. Ethylene production

A1B1=Uncoated & kept open, A2B1= Coconut oil coated & kept open, A3B1= Coconut oil and beeswax (90:10) coated & kept open, A4B1= Coconut oil and beeswax (80:20) coated & kept open,A1B2=Uncoated & kept in MAP, A2B2= Coconut oil coated & kept in MAP, A3B2= Coconut oil and beeswax (90:10) coated & kept in MAP, A4B2= Coconut oil and beeswax (80:20) coated & kept in MAP. Vertical bars indicate standard deviation.

179

Ethylene production trends influenced by edible coatings and MAP during ambient storage of

180

lemons are represented in Fig. 2. Initial ethylene production of lemon was 0.47µl.kg-1.h-1 and it was

181

reduced slightly in coated lemons up to 6th day after that it increased slightly. In uncoated open

182

lemons, ethylene production had increased throughout the storage and it was reached up to 0.61µl.kg-

183

1

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of all treatments was increased slightly with the change of lemon peel colour from green to yellow

185

during storage period. Burg [17] has written in postharvest physiology and hypobaric storage of fresh

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produce that ethylene production of lime just after harvest was 0.33 µl.kg-1.h-1(green stage) and it was

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decreased up to 4th day of storage, at 8th day it was 1.44 µl.kg-1.h-1(yellow green stage) and at 12th day

.h-1 at 18th day of storage. From the figure, it is observed that like respiration rate, ethylene production

7

188

of storage it was 0.38 µl.kg-1.h-1(yellow stage). Win, et al. [18] also reported that ethylene production

189

rate of untreated lime was 0.3 at initial stage of storage (ambient condition). A1B1 A2B1 A3B1 A4B1 A1B2 A2B2 A3B2 A4B2

0.8

Ethylene (µl/kg.hr )

0.6

0.4

0.2

0.0 0

3

6

9

12

15

18

Storage period (days)

190 191 192 193 194 195 196 197

Fig. 2. Ethylene production of lemon influenced by edible coating and MAP stored at ambient condition.

198

Fig. 3 illustrates the effect of edible coating and MAP during ambient storage on the firmness of

199

lemon. Initially the firmness value of lemon was 5.43N and it was decreased gradually with time but

200

the rate was different for different treatments. Among the treatment, MAP lemons retained their

201

firmness in a very good way throughout the storage period. On the other hand, coconut oil-beeswax

202

(both formulations, 90:10 and 80:20) coated lemons without MAP also had a good capacity to retain

203

firmness during whole storage period. Uncoated open lemons had lost 62.62% firmness at 6th day of

204

storage while MAP lemon was as firm as initial up to 12th day during storage. Open lemons uncoated

205

or coated with coconut oil only had lost their firmness sharply up to 9 days after that it was increased

206

again. It may happen due to excessive water loss made them harder.

A1B1=Uncoated & kept open, A2B1= Coconut oil coated & kept open, A3B1= Coconut oil and beeswax (90:10) coated & kept open, A4B1= Coconut oil and beeswax (80:20) coated & kept open, A1B2=Uncoated & kept in MAP, A2B2= Coconut oil coated & kept in MAP, A3B2= Coconut oil and beeswax (90:10) coated & kept in MAP, A4B2= Coconut oil and beeswax (80:20) coated & kept in MAP. Vertical bars indicate standard deviation.

3.3. Firmness

207

Texture or firmness is an important quality parameter of fresh fruits for consumer preference.

208

Degradation of insoluble protopectin to the more soluble pectic acid and pectin contribute to a

209

decrease of firmness in many fruits. These changes occur relatively slow and are less prominent to

210

citrus fruits as compared to climacteric fruits [19]. However some softening of fruits also occurs due

211

to the change of turgor pressure and or respiratory loss of dry matters during growth, development and 8

212

senescence. Nolpradubphan and Lichanporn [20] reported that an average firmness of lime fruits was

213

0.60 to 0.80 kg/cm2. When applying the beeswax edible coating to sweet orange Shahid and Abbasim

214

[21] discovered that the coatings not only prevented the moisture loss but improved the texture and

215

the general appearance of the fruits for a long period of storage. A1B1 A2B1 A3B1 A4B1 A1B2 A2B2 A3B2 A4B2

6.0

Firmness (N)

5.0 4.0 3.0 2.0 1.0 0.0 0

216

3

6 9 12 Storage period (days)

15

18

217 218 219 220 221

Fig. 3. Firmness of lemon influenced by edible coating and MAP stored at ambient condition.

222

3.4. Weight loss

A1B1=Uncoated & kept open, A2B1= Coconut oil coated & kept open, A3B1= Coconut oil and beeswax (90:10) coated & kept open, A4B1= Coconut oil and beeswax (80:20) coated & kept open,A1B2=Uncoated & kept in MAP, A2B2= Coconut oil coated & kept in MAP, A3B2= Coconut oil and beeswax (90:10) coated & kept in MAP, A4B2= Coconut oil and beeswax (80:20) coated & kept in MAP. Vertical bars indicate standard deviation.

223

Fig. 4 illustrates the effect of edible coating and MAP on the weight loss of lemon during storage.

224

Weight loss of fruits, in general, increased with the advancement in storage period. Maximum weight

225

loss occurred in uncoated open lemon. Whereas MAP lemons coated or uncoated preserved their

226

weight nicely throughout the storage period. Around 27.22% weight loss happened at 18th day of

227

storage in uncoated open lemons stored at ambient condition (21±2°C). On the other hand, coconut

228

oil-beeswax (both formulations, 90:10 and 80:20) coated lemons without MAP also have a good

229

capacity to retain their weight; around 9% weight loss was occurred at 15th day of storage. While

230

MAP lemons coated or uncoated lost their weight even less than 5% at 18th day of storage. Coating on

231

fruits and MAP creates a barrier between fruit skin and outer atmosphere which controls movement of

232

O2, CO2, moisture, and solute movement, thereby reducing respiration, water loss, and oxidation rates.

9

233

Weight loss is a consequence of fruit dehydration due to changes in surface transfer resistance to

234

water vapour, in respiration rate, and the occurrence of small cracks connecting the internal and

235

external atmospheres [22]. Shahid and Abbasim [21] speculated that the beeswax coatings decreased

236

the respiration rate of the fruits, thus reducing the weight loss and increasing the shelf life of sweet

237

orange. Ladaniya [23] studied the shelf life of sealed packed sweet orange fruits in heat shrinkable

238

film (LDPE) and stored the fruits in CFB boxes at (25±5°)C and 40- 45%RH. He observed the weight

239

loss of 1.60% in fruits wrapped in LDPEE over the unwrapped control fruits (25.51%). Sakhale and

240

Kapse [24] found that dipping of sweet orange in the solution (150 ppm GA3 + 500 ppm bavistin) and

241

further wrapping resulted in lowest weight loss (3.9%) as against 25.7% in the fruits were given only

242

a plain water dipping treatment (control) stored for 24 days at ambient condition (27±2°C). A1B1 A2B1 A3B1 A4B1 A1B2 A2B2 A3B2 A4B2

30

Weight loss (%)

25 20 15 10 5 0 0

3

243

6 9 12 Storage period (days)

15

18

244 245 246 247 248 249 250

Fig. 4. Weight loss of lemon influenced by edible coating and MAP stored at ambient condition.

251

Colour is an important factor in the perception of fruit quality. Fig. 5 illustrates the changes in

252

surface colour of lemons influenced by edible coating and MAP during ambient storage in terms of

253

hue angle. Initial hue angle value of lemon was 125.18° that mean, lemons were shiny green colours.

254

It is clear from the figure that hue angle value is decreasing gradually with storage period as lemons

255

turns from green to yellow skin colour with storage period. The reason is there, after this period,

256

ethylene production and respiration rate was increased that stimulate to degreen lemons.

A1B1=Uncoated & kept open, A2B1= Coconut oil coated & kept open, A3B1= Coconut oil and beeswax (90:10) coated & kept open, A4B1= Coconut oil and beeswax (80:20) coated & kept open,A1B2=Uncoated & kept in MAP, A2B2= Coconut oil coated & kept in MAP, A3B2= Coconut oil and beeswax (90:10) coated & kept in MAP, A4B2= Coconut oil and beeswax (80:20) coated & kept in MAP. Vertical bars indicate standard deviation.

3.5. External fruit colour

10

A1B1 A2B1 A3B1 A4B1 A1B2 A2B2 A3B2 A4B2

130

Hue angle(°)

120 110 100 90 80 0

3

257

6 9 12 Storage period (days)

15

18

258 259 260 261 262 263 264

Fig. 5. External colour (hue angle) of lemon influenced by edible coating and MAP stored at ambient condition. A1B1=Uncoated & kept open, A2B1= Coconut oil coated & kept open, A3B1= Coconut oil and beeswax

265

especially in coconut oil-beeswax (both formulations, 90:10 and 80:20) coated lemons throughout the

266

storage period. Hue angle value was about 95 in uncoated lemons open or in MAP at 18th day of

267

storage. On the other hand, hue angle value was around 112° in coated lemons (only coconut oil or

268

both formulations of coconut oil-beeswax) with MAP at 18th day of storage. Besides 110.40° and

269

109.13° hue angle was observed in lemon coated with coconut oil-beeswax (80:20) and that coated

270

with coconut oil-beeswax (90:10) respectively in open at 18th day of storage. So it is evident that

271

coconut oil or mixture of coconut oil-beeswax (both formulations, 90:10 and 80:20) had an enormous

272

effect to retain green colour of lemon even in ambient storage. Pure coconut oil coating helps to delay

273

in ripening of fruits and uniform colour development of Kagzi lime in later period of storage [8].

274

Obeed and Harhash [25] found the similar results like our findings, changes of skin colour from green

275

to yellow in "Mexican" lime during storage. Initially hue angle value of lime had 106.57°, after 4

276

weeks of storage, it was 97.45° when fruits were treated with hot water containing calcium chloride

277

2% and stored at 12°C.

(90:10) coated & kept open, A4B1= Coconut oil and beeswax (80:20) coated & kept open,A1B2=Uncoated & kept in MAP, A2B2= Coconut oil coated & kept in MAP, A3B2= Coconut oil and beeswax (90:10) coated & kept in MAP, A4B2= Coconut oil and beeswax (80:20) coated & kept in MAP. Vertical bars indicate standard deviation.

Figure illustrates that changes of colour (from green to yellow) was less in coated lemons

278 279

11

280

3.6. Juice Content

281

Fig. 6 shows juice content of lemon influenced by edible coating and MAP during storage. The

282

percentage of juice content showed increase in all treatments during storage. In lemons coated or

283

uncoated in MAP increased juice content up to the last day of storage. On the other hand, in uncoated

284

lemon kept open, juice content was increased (48.66%) up to 12th day after that it was declined and

285

reached to 46.3% at 18th day of storage. It may be due to excessive water loss from uncoated open

286

lemons.

287

formulations) or only coconut oil and kept in MAP had gained gradual increment of juice content

288

and reached to around 53% at 18th day of storage. Obeed and Harhash [25] found the similar results

289

like our findings, increments of juice content in "Mexican" lime during storage.

Initial juice content was 29.58%, lemons coated with coconut oil-beeswax (both

290

Initially lime had 50% juice content, after ten weeks of storage, it was 60% when fruits were

291

treated with hot water containing calcium chloride 1% or 2% and stored at 12°C reported by Obeed

292

and Harhash [25]. Lemons are considered mature for export when they contain 28% juice by volume

293

[26], regardless of peel color. An increase in both juice content and acidity normally occurs during

294

storage in lemons, as well as limes [27], in contrast to other edible citrus cultivars, and is a sign of

295

their increasing maturity. A1B1 A2B1 A3B1 A4B1 A1B2 A2B2 A3B2 A4B2

60

Juice content (%)

55 50 45 40 35 30 0

296 297 298 299 300 301 302

3

6 9 12 Storage period (days)

15

18

Fig. 6. Juice content of lemon influenced by edible coating and MAP stored at ambient condition. A1B1=Uncoated & kept open, A2B1= Coconut oil coated & kept open, A3B1= Coconut oil and beeswax (90:10) coated & kept open, A4B1= Coconut oil and beeswax (80:20) coated & kept open,A1B2=Uncoated & kept in MAP, A2B2= Coconut oil coated & kept in MAP, A3B2= Coconut oil and beeswax (90:10) coated & kept in MAP, A4B2= Coconut oil and beeswax (80:20) coated & kept in MAP. Vertical bars indicate standard deviation.

12

303

3.7. Ascorbic acid, TSS, titratable acidity and pH

304

At the day of harvest ascorbic acid in lemon was 29.4 mg/100g and it was reduced in all treatments

305

throughout the storage. During storage uncoated lemons kept open, lost it severely and retained 19.8

306

mg/100g at 18th day of storage. While coconut oil-beeswax (both formulations) coated lemons open

307

or in MAP preserved maximum (around 24 mg/100g) ascorbic acid at the last day of storage.

308

Initially, pH, acidity and TSS was 2.5, 6.68 (%) and 5.8 (°Brix) observed in lemon. During storage

309

acidity was decreased while TSS and pH were increased slightly irrespective to the treatments.

310

Porras et al. [28] found that ascorbic acid content in fresh Verna lemon was 47.2 mg/100g that is

311

higher from our results may be due to varietal difference, climatic condition etc. Piga et al. [29] found

312

that after harvest “libson” lemon retained pH 2.55, acidity 7.33 (%) and TSS 6.4 (° Brix) and during

313

storage acidity value was decreased slightly.

314 315 316

Table 1 Ascorbic acid, TSS, acidity and pH of lemon influenced by edible coating and MAP stored at ambient condition. Treat ment

A1B1 A2B1 A3B1 A4B1 A1B2 A2B2 A3B2 A4B2

Ascorbic acid (mg/100g) 0 9 day 18 day day 29.4 24.5b 18.8c 29.4 26.7a 20.2b 29.4 27.8a 24.2a 29.4 26.9a 23.8a 29.4 25.1b 20.7b 29.4 27.4a 23.7a 29.4 27.8a 24a 29.4 27.6a 24.2a

TSS (° Brix) 0 day 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8

9 day 6.7a 6.6a 6.2a 6.2a 5.9a 5.9a 6a 5.9a

pH

Acidity

18 day 7.7a 7.2a 7.1a 7.2a 6.7a 6.6a 6.7a 6.8a

0 day 6.68 6.68 6.68 6.68 6.68 6.68 6.68 6.68

9 day 6.61a 6.70a 6.64a 6.73a 6.44a 6.38a 6.98a 6.72a

18 day 5.32a 5.63a 5.67a 5.89a 5.7a 5.78a 5.77a 5.85a

0 day 2.50 2.50 2.50 2.50 2.50 2.50 2.50 2.50

9 day

18 day

2.52a 2.54a 2.55a 2.53a 2.52a 2.53a 2.54a 2.55a

2.8a 2.67a 2.59a 2.61a 2.6a 2.5a 2.58a 2.58a

317 318 319 320 321 322 323

A1B1=Uncoated & kept open, A2B1= Coconut oil coated & kept open, A3B1= Coconut oil and beeswax (90:10) coated & kept open, A4B1= Coconut oil and beeswax (80:20) coated & kept open,A1B2=Uncoated & kept in MAP, A2B2= Coconut oil coated & kept in MAP, A3B2= Coconut oil and beeswax (90:10) coated & kept in MAP, A4B2= Coconut oil and beeswax (80:20) coated & kept in MAP. Means with different letters within each column are significantly different (p < 0.05).

324

Lemons have a relatively high transpiration coefficient and water is lost very quickly from

325

unpacked lemon resulting shrinkage or shriveling of fruit skin. From the table 2 it is shown that the

326

skin of 53.13% uncoated & kept open lemons was shriveled while no shrinkage was observed in all

327

MAP lemons coated or uncoated and in coconut oil-beeswax (both formulations) coated lemon at 6th

328

day of storage even in open condition. Coating has moderate effect to reduce shriveling but MAP is

3.8. Shrinkage, yellowing and diseases incidence

13

329

the main technique to protect water loss or skin shrinkage. No skin shrinkage was happened in MAP

330

lemons coated or uncoated even at the last day (18th) of storage.

331

From the table 2 it is shown that skin colour of 18.75% uncoated and kept open lemons was

332

turned to yellow whereas no yellowing was occurred in all coated lemons at 6th day of storage.

333

Coating of coconut oil and beeswax had a great effect to retain green colour in lemon. At 18th day of

334

storage 100% lemons become yellow in uncoated with or without MAP but only 6.25% lemons

335

became yellow when it was coated with only coconut oil or coconut oil-beeswax (both formulations)

336

and kept in MAP.

337 338 339 340

Table 2 Shrinkage, yellowing and diseases incidence of lemon influenced by edible coating and MAP stored at ambient condition. Treatment

A1B1 A2B1 A3B1 A4B1 A1B2 A2B2 A3B2 A4B2

Shrinkage (%) 6 day 9 day 18 day 53.13a 100a 100a (45.14) (82.91) (82.91) 6.25b 28.13b 100a (13.96) (30.90) (82.91) 0.0c 6.25c 40.43b (3.96) (13.96) (38.09) 0.0c 6.25c 37.5b (3.96) (13.96) (36.43) 0.0c 0.0d 0.0c (3.96) (3.96) (3.96) 0.0c 0.0d 0.0c (3.96) (3.96) (3.96) 0.0c 0.0d 0.0c (3.96) (3.96) (3.96) 0.0c 0.0d 0.0c (3.96) (3.96) (3.96)

Yellowing (%) 6 day 9 day 18 day 18.75a 40.43a 100a (24.75) (38.09) (82.91) 0.0c 9.38b 75b (0.71) (17.20) (57.88) 0.0c 3.13c 40.43c (0.71) (9.83) (38.09) 0.0c 3.13c 37.5c (0.71) (9.83) (36.43) 6.25b 37.5a 100a (13.96) (36.43) (82.91) 0.0c 0.0d 6.25d (0.71) (0.71) (13.96) 0.0c 0.0d 6.25d (0.71) (0.71) (13.96) 0.0c 0.0d 6.25d (0.71) (0.71) (13.96)

Diseases incidence (%) 6 day 9 day 18 day 6.25a 0 0 (2.5) 3.13b 0 0 (1.76) 3.13b 0 0 (1.76) 3.13b 0 0 (1.76) 6.25a 0 0 (2.5) 3.13b 0 0 (1.76) 3.13b 0 0 (1.76) 3.13b 0 0 (1.76)

341 342 343 344 345 346

A1B1=Uncoated & kept open, A2B1= Coconut oil coated & kept open, A3B1= Coconut oil and beeswax (90:10) coated & kept open, A4B1= Coconut oil and beeswax (80:20) coated & kept open,A1B2=Uncoated & kept in MAP, A2B2= Coconut oil coated & kept in MAP, A3B2= Coconut oil and beeswax (90:10) coated & kept in MAP, A4B2= Coconut oil and beeswax (80:20) coated & kept in MAP. Means with different letters within each column are significantly different (p < 0.05). Values in parenthesis are transformed data.

347

Lemon stalk became soft, little black or white fungus was just observed at the last stage of storage

348

period. Maximum 6.25% fruits were affected by microorganism at 18th day during storage. Hot-humid

349

temperature might help for this incidence. High-humidity storage was shown to increase lemon

350

storage potential [30], and LDPE or HDPE packaging is able to maintain a high humidity in package

351

to reduce transpiration and skin shrinkage [31]. The incidence of decay, particularly in fruits stored at

352

20°C, is a major limitation to the use of microperforation polybags for long-term storage of acid lime 14

353

[32]. Nasrin et al [33] reported that incidence of rotting in uncoated/control mandarin started at 4th day

354

of storage, while it was initiated in coconut oil coated one at 16 days of ambient storage. Coconut oil-

355

beeswax (both formulations) or only coconut oil coated lemons in MAP were greener, shiny and full

356

of juice at 18th day of storage period.

357

3.9. Sensory quality

358

Sensory evaluation was done on colour, flavour, texture and overall acceptability of lemon at 6th

359

9th and 18th day of storage. In case of overall acceptability, coated lemon (coconut oil only or both

360

formulations of coconut oil-beeswax) kept in MAP and coated lemon (both formulations of coconut

361

oil-beeswax) kept open secured the highest score (9) that was statistically similar with the score (8.5)

362

of lemon coated with coconut oil only and kept open at 6th day of storage. On the other hand, control

363

lemons (uncoated & open) secured only 4.5 that mean neither like nor dislike on the same day (6) of

364

storage. At 18th day of storage, maximum score (7.2) was obtained by the coconut oil-beeswax (both

365

formulations, 90:10 and 80:20) coated lemons kept in MAP and this score is statistically similar with

366

the value obtained by the lemon coated with coconut oil only and kept in MAP. Coconut oil-beeswax

367

(both formulations) or only coconut oil coated lemons in MAP were green and shiny throughout the

368

storage period as also shown in figure 7.

369 370

Table 3 Sensory quality of lemon influenced by edible coating and MAP stored at ambient condition. Treatment Colour Flavour Texture Overall acceptability 6 9 18 6 9 day 18 6 day 9 18 6 9 18 day day day day day day day day day day A1B1 4.2d 3.8c 1.9d 5.4c 4.6d 2.7d 4.4c 3.6c 5.1c 4.5c 3.1d 2.5c A2B1 8.5a 6.8b 3.4c 8.6a 6.8b 4.4c 7.6b 6.4b 4.9b 8.5a 7.2b 3.5c A3B1 8.8a 7.4b 5.1b 8.7a 7.4b 5.6b 7.8b 6.8b 5.5b 9a 8.1a 5.3b A4B1 8.8a 7.6b 5.0b 8.5a 7.2b 5.3b 7.9b 6.8b 5.7b 9a 8.0a 5.4b A1B2 5.3c 4.5c 3.3c 6.8b 5.7c 4.5c 8.8a 8.4a 7.8a 6.8b 4.7c 3.2c A2B2 9a 8.8a 7.5a 9a 8.8a 7.5a 9a 8.8a 8.0a 9a 8.7a 7.0a A3B2 9a 8.7a 7.9a 9a 8.7a 7.6a 9a 8.7a 8.1a 9a 8.4a 7.2a A4B2 9a 8.6a 7.9a 9a 8.8a 7.4a 9a 8.6a 8.2a 9a 8.5a 7.2a

371 372 373 374 375

A1B1=Uncoated & kept open, A2B1= Coconut oil coated & kept open, A3B1= Coconut oil and beeswax (90:10) coated & kept open, A4B1= Coconut oil and beeswax (80:20) coated & kept open,A1B2=Uncoated & kept in MAP, A2B2= Coconut oil coated & kept in MAP, A3B2= Coconut oil and beeswax (90:10) coated & kept in MAP, A4B2= Coconut oil and beeswax (80:20) coated & kept in MAP. Vertical bars indicate standard deviation. Means with different letters within each column are significantly different (p < 0.05).

15

Uncoated lemon in open condition at 6 days of storage

Uncoated lemon in MAP at 18 days of storage

Coconut oil coated lemon in open at 15 days of storage

Coconut oil-beeswax (90:10) coated lemon in open at 15 days of storage

Coconut oil-beeswax (90:10) coated lemon in MAP at 18 days of storage 376 377

Coconut oil coated lemon in MAP at 18 days of storage

Fig.7. Some pictorial views of coated and uncoated lemons kept in MAP and open in crates during storage at ambient condition (21±2°C and 50±5% RH)

378 379 380 381 16

382

4. Conclusion

383

The results of physical, chemical and sensory parameters proved that coconut oil-beeswax (90:10 and

384

80:20) or only coconut oil coating of lemons and kept in MAP had a great effect to increase the shelf

385

life maintaining quality during ambient storage. Hue angle value was about 95 (yellow) in uncoated

386

lemons open or in MAP while, it was around 112 (green) in all coated lemons (coconut oil or both

387

formulations of coconut oil-beeswax) in MAP at 18 days of storage. Uncoated open lemon was

388

acceptable up to 6 days, coconut oil-beeswax (both formulations, 90:10 and 80:20) coated lemon kept

389

open was acceptable up to 15 days and coconut oil-beeswax (both formulations) or only coconut oil

390

coated lemon in MAP was acceptable more than 18 days.

391 392

Acknowledgement: We thank head of the department of pomology division for his overall support to

393

conduct this experiment.

394 395

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396

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20

Highlights: Fresh lemons were coated with coconut oil-beeswax (90:10) or only coconut oil. Coated lemons were kept in MAP or open and stored at ambient condition. Uncoated lemons were yellow at 6th day but coated ones in MAP were green at 18th day. Lemons in MAP had gained maximum (53%) juice content while it was 29.58% initially. Uncoated open lemon was good for 6 days but coated one in MAP was good for 18 days.