Advances in Agriculture
Volume 2021 (2021), Article ID 8859144, 12 pages
https://doi.org/10.1155/2021/8859144

Research Article

Effectiveness of Selected Cold Chain Management Practices to Extend Shelf Life of Mango Fruit

Emmanuel M. Amwoka,¹ Jane L. Ambuko,¹ Hutchinson M. Jesang’,¹ and Willis O. Owino²

¹Department of Plant Science and Crop Protection, University of Nairobi, P.O. Box 29053-00625, Kangemi, Nairobi, Kenya
²Department of Food Science and Technology, Jomo Kenyatta University of Agriculture & Technology, P.O. Box 62000–00200, Nairobi, Kenya

Correspondence should be addressed to Jane L. Ambuko; ambuko@yahoo.com

Received 12 September 2020; Accepted 31 May 2021; Published 8 June 2021

Academic Editor: Jiban Shrestha

Copyright © 2021 Emmanuel M. Amwoka et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

An on-farm study was conducted among smallholder mango farmers in Embu County of Kenya to demonstrate the effectiveness of simple harvest and postharvest handling practices to attain cold chain and extend mango shelf life. The recommended cold chain practices were compared with common farmers' practices. 'Apple', 'Ngowe', 'Kent', and 'Tommy Atkins' harvested at the mature green stage were used in the study. To demonstrate proper cold chain, fruits were harvested before 8 am, transported in crates lined with dampened newspapers, precooled in an evaporative charcoal cooler, and then transferred to a Coolbot™ cold room (10 ± 2°C). To demonstrate common farmers’ practices, fruits were harvested at noon, transported in open crates, and stored at ambient room conditions (25 ± 7°C, 55 ± 15%RH). The air and fruit pulp temperatures were monitored regularly using HUATO® data loggers. During the storage period, a random sample of 3 fruits (per variety) per treatment was taken after every 3 days to evaluate ripening related changes including physiological weight loss, colour, firmness, and total soluble solids. Proper cold chain practices resulted in low fruit pulp temperature (average 11°C) compared to 25°C for fruits handled using common practices by farmers leading to faster ripening as evidenced by lower peel/pulp colour and firmness, higher physiological weight loss, and higher total soluble solids. For example, flesh firmness of fruits under poor cold chain practices decreased from initial 36.6 N, 45.9 N, 66.5 N, and 46.8 N to 3.1 N, 2.4 N, 3.2 N, and 3.1 N for ‘Apple’, ‘Ngowe’, ‘Kent’, and ‘Tommy Atkins’ varieties, respectively, at the end of storage while that of fruits under proper cold chain practices reduced to 2.3 N, 1.5 N, 3.9 N, and 2.9 N, respectively, for the four varieties at the end of storage. Overall, proper cold chain management extended mango shelf life by 18 days. Application of simple harvest and handling practices coupled with simple storage technologies can attain and maintain the cold chain required to preserve quality and extend shelf life. This could increase the marketing and storage periods for later selling and processing, respectively, of mango fruits.

1. Introduction

Mango (Mangifera indica L.) is one of the main fruits produced in Kenya mainly for the domestic market and to a small extent for export. It is ranked 2nd in both value and export market after banana and avocado, respectively [1]. Mango production has increased over the past years as evidenced by the area under production increasing by 1,452 ha from 2016 to 2017, a 3% rise. This increase can be attributed to increased demand for fresh market, fruit processing, and health concerns among the consumers [1]. However, despite the increase in production and mango's growing economic importance in recent years, its value has not been fully exploited due to various factors, including high postharvest harvest losses along the mango value chain. It is reported that at least 40–45% of the mango fruits are lost due to poor handling of harvest and postharvest handling practices [2].

Mango is a highly perishable fruit with a short shelf life after harvest. Ripening and subsequent deterioration of the fruit are attributed to various physiological processes, including respiration, softening, and colour changes. The rate of ripening and deterioration of the fruit due to these physiological processes is affected by environmental factors including temperature and relative humidity [3]. In handling perishable commodities such as fruits and vegetables, maintenance of low but safe temperatures during handling of the produce from harvest to the end-user (cold chain) is critical for preserving the quality. Cold chain for perishable products is the continuous handling of the produce in cool temperatures during postharvest handling from harvest, collection, transport, storage, processing, and marketing until they reach the final consumers [4]. Components of a proper cold chain are divided into seven, namely, on-farm cooling, initial cooling, storage, transportation, distribution, retail, and consumer, with possible temperature management. An increase in temperature by 10°C above optimum increases the deterioration rate in perishable commodities 2-3-fold. Delays between harvesting and cooling or processing can result in quantitative losses (due to water loss and decay) and qualitative losses (losses in ﬂavor and nutritional quality) [5]. Proper cold chain management reduces respiration thus lessens perishability, reduces transpiration and hence lessens water loss and shriveling, reduces ethylene production and increases resistance to ethylene action slowing ripening and natural senescence, decreases the activity of microorganisms, and reduces browning and loss of texture, flavor, and nutrients [4]. Cold chains have been used to maintain postharvest quality of fruits during shipment, marketing, and storage before consumption.

Besides temperature, relative humidity is another environmental factor contributing to the deterioration of harvested perishable produce such as fruits and vegetables. Physiological water loss that results in shriveling contributes significantly to the production of deterioration and postharvest losses in perishable commodities. At harvest, the harvested crop may lose water due to several factors including harvest maturity, environmental conditions and harvest techniques, and physical injury [6]. Harvesting fruits during hot times of the day will result in high heat load in harvested produce, leading to high respiration and transpiration and hence increased water loss during prolonged storage [7]. This is due to increased vapour pressure deficit within the produce tissue that may cause fruit cracking and hence peel permeance allowing increased water loss after harvest. Physiological water loss is further aggravated by poor postharvest handling practices [6]. Low temperature and high relative humidity are key in reducing water loss from the fruit to the surroundings, suppress enzymatic and respiratory activities leading to ripening and senescence, and slow pathological activities creating a safe environment for fruit preservation. On the contrary, high temperatures and low relative humidity at harvest time result in water loss causing fruits to shrivel, lowering quality [8].

Most farmers perceive cold chain management as a complex system that requires high-cost infrastructure including conventional cold rooms and refrigerated transport. However, smallholder farmers can achieve the same benefits of the conventional cold chain management practices by applying simple harvest and postharvest handling practices coupled with low-cost storage technologies.

Harvesting produce during cooler times of the day reduces heat load which would otherwise result from high temperatures and exposure to direct sunlight during hotter times of the day [9]. Harvesting early in the morning when plant cells are turgid minimizes water loss and significantly enhances shelf life and preserves quality. Studies in French beans showed that harvesting during hotter hours lost significantly higher water during storage [10]. Immediately after harvest, the use of field shades to keep the produce cool also reduces the amount of heat load in the produce. Field shades cool produce, thus decreasing metabolic reactions in harvested produce [11]. Harvested produce should be transported from the field to storage immediately. Delays in the field may expose the produce to more heat and hence high heat load in harvested crops, affecting shelf life and quality [10]. For produce destined for cold storage, the longer the duration to cooling, the longer the time to attainment of set storage temperature. Past studies show that a delay by one hour between harvest and precooling causes a loss of one day in the shelf life [12]. Precooling before cold storage is necessary to remove field heat in harvested produce [4]. Removal of field heat by precooling reduces postharvest decay, controls the development of physiological disorders, and decreases metabolic activities such as respiration rate and ethylene production, thus delaying ripening, ageing, and senescence [13]. 25–30% postharvest losses are recorded in unprecooled commercial fruits and vegetables while only 5–10% postharvest losses are recorded for precooled produce [14]. Precooling coupled with other cool chain practices and technologies has been used to extend shelf life and preserve the quality of harvested tomatoes [15].

Cold storage in perishable produce can be achieved through the application of low-cost cold storage technologies. Examples of low-cost technologies that have been used successfully to preserve the quality of perishable produce include the CoolbotTM cold room, solar-powered coolers, and evaporative cooling technologies. The CoolbotTM cold room is a low-cost cold storage alternative to conventional cold rooms. The CoolbotTM cold room is composed of the Coolbot™, a compatible air conditioner (AC) and an insulated room. The CoolbotTM is an electronic gadget that overrides the thermostat of the AC, thereby enabling it to cool the room to lower than set temperatures (usually 18oC) without ice buildup on the evaporator coils [16]. CoolbotTM cold room has been utilized to extend mango's shelf life [17] and other produce such as turnips, potatoes, tomatoes, and beans. The CoolbotTM cold room's advantage over conventional cold rooms is that it is relatively affordable (compared to the conventional cold room), electricity-efficient, and environmentally friendly [16]. For the off-grid smallholder farmers, evaporative cooling provides a feasible alternative. Evaporative coolers work on the principle of evaporative cooling whereby when water held in a wetted medium (charcoal or sand) evaporates, it draws heat from the surroundings, creating a cooling effect [18]. Evaporative coolers are considered feasible and appropriate for smallholder rural farmers because they can be made from locally available materials and the costs of running them are low. However, the cooling achieved by evaporative coolers is dependent on the surrounding environment, temperature, and relative humidity and the cooling attained is often not low enough to slow down some of the deteriorative processes [19]. Evaporative cooling is effective for precooling and short-term storage of harvested produce. Different evaporative coolers have been used to extend shelf life and preserve the postharvest quality of horticultural crops such as leafy vegetables [19] and tomato [20].

Application of cold storage technologies can extend the marketing period of perishable produce such as mango, thereby avoiding distress sales by smallholder farmers who are otherwise vulnerable to middlemen. This study's objective was to evaluate the effectiveness of selected cold chain management practices and technologies to achieve effective cooling and extend the shelf life of mango fruit.

2. Materials and Methods

2.1. Study Site

The study was conducted in Karurumo area (S 0°28′11.6184″ E 37°39′47.466″), Runyenjes subcounty, Embu County in Kenya. Embu County is located in a medium potential region, agroecological zone (AEZ) III. It receives a total annual rainfall of averagely 1067.5 mm (received twice in a year) at an altitude of 700 m–6500 m above sea level, and the temperatures range from 26°C to 35°C.

2.2. Experimental Design

Uniform mature green mango fruits of 'Apple', 'Ngowe', 'Kent', and 'Tommy Atkins' varieties were harvested at two different times of the day from 3 selected farms. To demonstrate proper cold chain practices, all the four mango varieties were harvested in the morning (before 8 am) and transported to the experimental site in crates lined with dampened newspapers to simulate evaporative cooling during transit. Upon arrival at the aggregation centre, fruits were sorted for uniformity based on size and freedom from damage. They were then precooled in an evaporative charcoal cooler until temperatures stabilized at 22.2°C, 22.03°C, 22.1°C, and 22.07°C for 'Apple', 'Ngowe', 'Kent', and 'Tommy Atkins' varieties, respectively, and then stored in the CoolbotTM (12 ± 2)°C) in open crates. In the second harvest, in order to demonstrate farmers’ practices, fruits of the same varieties were harvested the same day at midday (noon) and transported to the experimental site in open crates. At the centre, the fruits were sorted for uniformity and stored directly under ambient conditions (25 ± 7°C), with relative humidity of 55 ± 15%. The experiment was laid down as a completely randomized design (CRD) with a factorial treatment arrangement. Factor 1 was cold chain practices with two levels: cold chain (Treatment 1) and no cold chain (Treatment 2). Factor 2 was variety with 4 levels: 'Apple', 'Ngowe', 'Kent', and 'Tommy Atkins'. The treatments were replicated three times.

2.3. Data Collection

2.3.1. Air Temperature and Air Relative Humidity (%)

The air temperature and percentage relative humidity inside the CoolbotTM cold room and ambient room were regularly monitored using HUATO® data loggers (Model HE17x, Huato Electric Co., Ltd., Shenzhen, China) after every one hour. The loggers’ data were retrieved at the end of the experiment by downloading recorded data using HUATO® app.

2.3.2. Pulp Temperature

The pulp temperature of the fruits was recorded at harvest time, upon arrival at the centre, after every one hour for precooled fruits till temperatures stabilized, and then after every three days in both treatments. This was done by plunging the temperature probes’ tip into the 3 sample fruits and measurement on the probe taken. The 3 measurements were averaged and presented as the internal pulp temperature.

2.3.3. Percentage Cumulative Weight Loss

In each treatment, three fruits per variety numbered 1 to 3 were used to measure cumulative weight loss using a digital weighing scale (Model Libror AEG-220, Shimadzu Corp., Kyoto, Japan). The mango fruits' initial weight at day 0 after harvest was recorded; then the new weight of the same fruit on each sampling day was noted. Data were collected every 3 days in both treatments. Percentage cumulative weight loss was calculated using

2.3.4. Peel and Flesh Colour

Peel and flesh colour were determined by sampling three fruits per treatment and measuring two different spots along the equator using a Minolta colour meter (Model CR-200, Osaka, Japan), calibrated with a standard white piece of paper. To access the flesh, the three sampled fruits were cut open longitudinally and measurements were taken at two different spots. Data were collected every 3 days in both treatments. Colour coordinates (L, a, and b) were obtained and then hue angles (h°) were calculated by converting a and b as shown in

2.3.5. Peel and Flesh Firmness

Three fruits per treatment were sampled and peel and flesh firmness were measured at two different, intact, and peeled mango spots using a penetrometer (Model CR-100D, Sun Scientific Co., Ltd., Japan) fitted with a 5 mm probe. For the flesh firmness, the probe was allowed to penetrate to a depth of 1.5 mm and the corresponding force required to penetrate this depth was determined. Data were collected every 3 days in both treatments. Firmness was expressed as Newton (N).

2.3.6. Total Soluble Solids (TSS)

Three fruits per treatment were sampled and total soluble solids were determined using an Atago hand refractometer (Model 500, Atago, Tokyo, Japan). On each sampling time, 3 ml of the fruit juice was extracted from three different fruits by pressing and placed on the hand refractometer to obtain the Brix level. Data were collected every 3 days in both treatments. The total soluble solid was then expressed as oBrix.

2.3.7. Overall Shelf Life

The mango fruits' total shelf life was determined by counting the number of days taken to reach the end-stage. End-stage was based on firmness and visual appearance at which the fruit was saleable.

2.4. Data Analysis

The data collected was analyzed using the GenStat 15th Edition statistical program. Analysis of variance (ANOVA) was used to test for significant differences among treatments for each parameter and means separated using Fischer's protected least significant difference at  = 0.05.

3. Results

3.1. Changes in Air Temperature and Percentage Relative Humidity in the Coolbot™ Cold Room and Ambient Room

The initial temperature in the Coolbot™ cold room 16.9°C was preset (10 ± 2)°C, which is the recommended cold storage temperature for mango fruits. The preset temperature was attained within an hour and remained stable/constant during the 24-hour observation period. In the ambient room, the temperatures fluctuated between 24.9°C and 32.8°C. The percentage relative humidity in the Coolbot™ cold room and ambient room ranged between 80.6%–92.6% and 40.4%–71.5%, respectively (Figure 1).

Figure 1: Differences in temperature (°C) and relative humidity (%) in the Coolbot™ cold room and ambient room during the first 24 hours of storage.

3.2. Fruit Pulp Temperature

The average internal pulp temperatures were 16.4°C and 31.4°C for fruits harvested during the cool morning hours versus hot afternoon, respectively. Upon arrival at the centre, pulp temperature of the fruits harvested in the morning averaged 27.5°C while that for fruits harvested at midday averaged 33.4°C. After precooling, the pulp temperatures stabilized at 22.2°C, 22.03°C, 22.1°C, and 22.07°C for ‘Apple’, ‘Ngowe’, ‘Kent’, and ‘Tommy Atkins’ varieties, respectively, after 6 hours. There was a significant difference ( > 0.05) in pulp temperature for fruits under proper cold chain practices and those under farmer practices (no cold chain). However, there was no significant difference ( > 0.05) between pulp temperatures of the different mango varieties used in the study (Table 1).

Table 1: Differences in pulp temperature (°C) of four mango varieties as affected by cold chain management practices.

Variety
Treatment
Days in storage
Means

T0
T1
3
6
9
12
15
18
21
24
27
30
33

Apple
Cold chain
16.3b
27.4c
10.9a
10.6b
11.8a
11.5a
11.5b
11.2a
11.4a
11.5ab
11.9ab
12.6b

13.2

No cold chain
31.6a
33.5a
23.5b
24.2d
24.8d
22.3c

26.7

Kent
Cold chain
16.5b
27.8b
10.8a
10.5b
12a
11.4a
11.5b
11.3a
11.4a
11.7bc
12.1b
12.5ab
12.8
13.3

No cold chain
31.5a
33a
23.5b
22.9bc
23.6b
22.2c
20.7e

25.3

Ngowe
Cold chain
16.3b
27.5c
11a
11.2c
12a
11.5a
10.6a
11.1a
11.8a
11.9c
11.7a
12.4a

13.3

No cold chain
31.6a
33a
23.5b
24.4de
24.3c
22.8d

26.6

Tommy Atkins
Cold chain
16.3b
27.3c
11a
9.9a
11.7a
11.2a
11.3b
11.3a
11.8a
11.3a
11.9ab
12.5ab

13.1

No cold chain
31a
34a
23.6b
23.7e
24.1c
25.8b

27.0

Treat x variety (LSD 0.05) %CV
0.66
0.66
0.48
0.46
0.45
0.37
0.48
0.4
0.6
0.27
0.4
0.19
0.2

1.5
1.2
1.6
1.8
1.4
1.3
1.9
1.5
2.7
1.2
1.8
0.8
0.4

T0: pulp temperature immediately after harvest in the field; T1: pulp temperature upon arrival at the aggregation centre. Means within each column followed by different letters differ significantly at  > 0.05.

3.3. Physiological Weight Loss (PWL)

Physiological weight loss was recorded to be high in fruits under farmer practice. There was a significant difference ( > 0.05) in percentage cumulative weight loss between fruits under proper cold chain practices and farmer practices. At the end of storage (days 30–33), fruits under proper cold chain practices recorded %PWL of 11.59%, 11.15%, 12.72%, and 7.79% for Apple, Ngowe, Kent, and Tommy Atkins varieties, respectively. The fruits under farmer practices recorded significantly high PWL at the end of storage (days 12–15) averaging 14.96%, 13.46%, 17.71%, and 12.96% for ‘Apple’, ‘Ngowe’, ‘Kent’, and ‘Tommy Atkins’ varieties, respectively (Table 2).

Table 2: Changes in % cumulative weight loss of four mango varieties as affected by cold chain management practices.

Variety
Treatment
Days in storage
Means

0
3
6
9
12
15
18
21
24
27
30
33

Apple
Cold chain
0.00
1.66a
2.57a
3.19a
4.51a
5.00a
7.70b
8.47b
9.58b
10.62b
11.59b

5.90

No cold chain
0.00
4.09b
8.35c
11.30c
14.96b

7.74

Kent
Cold chain
0.00
1.52a
3.10a
3.79a
4.57a
5.63a
7.26ab
7.99b
9.62b
10.57b
11.51b
12.72
6.52

No cold chain
0.00
3.45b
7.68bc
10.47bc
13.98b
17.71c

8.88

Ngowe
Cold chain
0.00
1.75a
2.65a
3.54a
4.77a
5.58a
6.99ab
7.99b
9.22b
10.16b
11.15b

5.80

No cold chain
0.00
3.75b
8.01c
10.85bc
13.46b

7.21

Tommy Atkins
Cold chain
0.00
1.76a
2.19a
2.58a
3.07a
3.90a
5.10a
5.43a
6.53a
7.19a
7.79a

4.14

No cold chain
0.00
3.62b
6.78b
9.40b
12.95b

6.55

Treat x variety (LSD 0.05) CV (%)
0.97
1.38
1.79
2.31
2
2.2
1.52
1.89
1.6
1.8
3.61

20.8
15.3
14.9
14.7
13.1
11.4
10.8
13.9
8.8
9.1
8.1

Means within each column followed by different letters differ significantly at  > 0.05.

3.4. Peel and Flesh Colour

The peel colour of the fruits gradually changed from green to yellow as the fruits ripened while the flesh colour gradually changed from whitish-yellow to full yellow. Hue angles for fruits under farmer practices steadily decreased as the fruits ripened faster as compared to fruits under proper cold chain practices. Peel colour of fruits decreased from initial hue angle value of 110.33°, 130.72°, 112.28°, and 111.12° for ‘Apple’, ‘Kent’, ‘Ngowe’, and ‘Tommy Atkins’ varieties, respectively, to 73.89°, 101.29°, 77.34°, and 85.11° at the end of storage for fruits under proper cold chain management as compared to fruits under poor cold chain management that recorded 61.85°, 102.37°, 55.8°, and 52.30°, respectively, at the end of storage (Table 3).

Table 3: Changes in peel hue angles (Ho) of four mango varieties as affected by cold chain management practices.

Variety
Treatment
Days in storage
Means

0
3
6
9
12
15
18
21
24
27
30
33

Apple
Cold chain
110.33a
104.87bc
102.67cd
98.05d
96.66b
96.09a
90.46a
82.29a
81.41a
74.60a
73.89a

91.94

No cold chain
110.33a
96.96a
86.75a
74.20b
61.85a

86.02

Kent
Cold chain
130.72b
130.53e
128.63e
124.49f
123.83c
122.69c
122.07d
120.28b
119.58b
108.09b
104.22c
101.29
119.70

No cold chain
130.72b
130.47e
128.53e
119.04f
108.42c
102.37c

119.92

Ngowe
Cold chain
112.28a
111.40cd
104.14d
103.07de
98.81b
98.14ab
96.47ab
94.53a
86.30a
81.41a
77.34abc

96.72

No cold chain
112.28a
98.95ab
94.45bc
84.14c
55.80a

89.12

Tommy Atkins
Cold chain
111.12a
111.01d
105.92d
103.06e
102.08b
98.61ab
97.94ab
96.02a
95.89a
88.74a
85.11ab

99.59

No cold chain
111.12a
97.85ab
72.74ab
70.15a
52.30a

80.83

Treat x variety (LSD 0.05) CV (%)
4.12
7.78
11.10
6.63
9.93
11.95
15.30
16.95
18.86
19.39
24.16
61.30

2.00
4.00
6.10
3.90
6.40
6.10
8.20
9.10
10.80
11.80
16.30
18.20

Means within each column followed by different letters differ significantly at  > 0.05.

Similarly, flesh colour also decreased from initial hue angle value of 87.19°, 89.41°, 91.22°, and 89.12° for ‘Apple’, ‘Kent’, ‘Ngowe’, and ‘Tommy Atkins’ varieties, respectively, to 66.87°, 62.19°, 73.58°, and 64.20° at the end of storage for fruits under proper cold chain management. On the other hand, hues of fruits under poor cold chain management decreased to 63.80°, 66.52°, 66.0°, and 71.95°, respectively, at the end of storage, approximately 18 days earlier compared to fruits under proper cold chain practice (Table 4).

Table 4: Changes in flesh hue angles (Ho) of four mango varieties as affected by cold chain management practices.

Variety
Treatment
Days in storage
Means

0
3
6
9
12
15
18
21
24
27
30
33

Apple
Cold chain
87.19a
85.05c
84.24c
83.18de
77.29c
73.96bc
72.05ab
71.88a
70.80a
67.68a
66.87a

76.38

No cold chain
87.19a
71.75a
71.51a
66.98a
63.80a

72.25

Kent
Cold chain
89.41bc
89.30d
88.99e
88.64f
87.85d
84.56e
84.33f
83.48d
81.12c
78.98c
77.99c
62.19
83.07

No cold chain
89.41bc
89.41d
82.04d
81.50cd
71.62c
66.52a

80.08

Ngowe
Cold chain
91.12ab
88.33d
86.73e
85.94ef
84.66d
84.00e
83.67e
81.99c
81.61c
74.96bc
73.58b

83.33

No cold chain
91.12ab
80.46b
78.39b
75.17b
66.00b

78.23

Tommy Atkins
Cold chain
89.12abc
87.60d
83.42be
83.20f
80.74d
80.00de
78.94de
76.92d
73.69b
71.22b
64.20b

79.00

No cold chain
89.12abc
81.76c
80.77c
75.66c
71.95b

79.85

Treat x variety (LSD 0.05) CV (%)
10.15
3.82
2.73
3.13
3.13
3.62
3.82
2.47
3.24
3.90
6.19
11.82

6.20
2.50
1.90
2.20
2.30
2.50
2.70
1.60
2.20
2.70
4.50
4.40

Means within each column followed by different letters differ significantly at  > 0.05.

3.5. Peel and Flesh Firmness

Peel and flesh firmness decreased gradually as the fruits ripened, irrespective of the treatment and variety. Peel firmness of fruits under poor cold chain practices decreased from the initial 110.2 N, 153.1 N, 118.5 N, and 115.1 N to 22.7 N, 18.9 N, 30.1 N, and 29.6 N for ‘Apple’, ‘Ngowe’, ‘Kent’, and ‘Tommy Atkins’ varieties, respectively, at the end of the storage. Fruit under proper cold chain practices decreased to 7.7 N, 6.7 N, 15.9 N, and 9N for ‘Apple’, ‘Ngowe’, ‘Kent’, and ‘Tommy Atkins’ varieties, respectively, at the end storage, 18 days earlier compared to fruits under proper cold chain management (Table 5).

Table 5: Changes in peel firmness (N) of four mango varieties as affected by cold chain management practices.

Variety
Treatment
Days in storage
Means

0
3
6
9
12
15
18
21
24
27
30
33

Apple
Cold chain
110.22a
103.08bc
95.73bc
85.42d
65.28c
63.47cd
54.20ef
50.22b
30.48b
15.02a
7.78a

61.90

No cold chain
110.22a
55.47b
45.91a
27.13a
22.68a

52.28

Kent
Cold chain
153.08c
146.13e
122.47e
117.02f
101.97e
101.33e
86.95g
72.52c
49.93c
40.68b
16.22b
15.92
85.35

No cold chain
153.08c
141.43e
116.90d
67.78d
40.15b
30.08ab

91.57

Ngowe
Cold chain
118.52ab
107.90d
103.22c
64.98c
60.27c
58.22bc
44.75de
42.43a
22.72a
7.93a
6.73a

57.97

No cold chain
118.52ab
34.88a
32.77a
25.28a
18.92a

46.07

Tommy Atkins
Cold chain
115.08ab
105.93cd
102.42c
95.10e
94.62d
64.32d
61.30f
41.97a
24.45ab
10.93a
9.02a

65.92

No cold chain
115.08ab
113.90c
84.95b
47.10b
39.57b

80.12

Treat x variety (LSD 0.05) CV (%)
16.97
13.25
14.45
12.14
14.23
12.46
12.34
6.43
7.70
15.05
4.44
0.78

7.40
7.30
8.90
9.70
13.80
11.50
15.70
6.70
12.80
22.60
23.00
1.60

Means within each column followed by different letters differ significantly at  > 0.05.

Similar trends were recorded in flesh firmness of fruits under the study. Flesh firmness of fruits under poor cold chain practices decreased from initial 36.6 N, 45.9 N, 66.5 N, and 46.8 N to 3.1 N, 2.4 N, 3.2 N, and 3.1 N for ‘Apple’, ‘Ngowe’, ‘Kent’, and ‘Tommy Atkins’ varieties, respectively, at the end of storage while fruits under proper cold chain practices decreased to 2.3 N, 1.5 N, 3.9 N, and 2.9 N for ‘Apple’, ‘Ngowe’, ‘Kent’, and ‘Tommy Atkins’ varieties, respectively, on the final day of storage (Table 6).

Table 6: Changes in flesh firmness (N) of four mango varieties as affected by cold chain management practices.

Variety
Treatment
Days in storage
Means

0
3
6
9
12
15
18
21
24
27
30
33

Apple
Cold chain
36.55a
32.50b
31.90b
25.13c
22.85c
17.13bc
14.58abc
6.73a
5.96a
4.60ab
2.27a

18.20

No cold chain
36.55a
10.12a
6.92a
3.62a
3.13a

12.07

Kent
Cold chain
66.47b
49.57d
42.57c
31.07d
20.48d
20.43d
17.50c
10.92a
9.05b
6.13b
5.85b
3.95
23.67

No cold chain
66.47b
41.78cd
11.22a
8.05ab
6.80ab
3.20ab

22.92

Ngowe
Cold chain
45.98a
36.35bc
32.67b
19.13bc
11.88b
9.52abc
8.82abc
7.57a
6.02a
2.78a
1.49a

16.56

No cold chain
45.98a
6.45a
4.82a
4.68a
2.42a

12.87

Tommy Atkins
Cold chain
46.75a
40.82bc
35.63b
33.02c
25.58c
18.60c
15.25bc
11.27a
6.53a
3.59a
2.95a

21.82

No cold chain
46.75a
38.22b
7.05a
6.48a
3.15ab

20.33

Treat x variety (LSD 0.05) CV (%)
12.78
13.47
9.87
11.58
8.38
12.9
10.88
9.31
1.8
8.3
2.16
4.1

15
22
25.3
28.1
23.2
21.6
27.6
21.3
12.6
22.5
23.3
28.5

Means within each column followed by different letters differ significantly at  > 0.05.

3.6. Total Soluble Solids (TSS)

Total soluble solids increased as the fruits ripened irrespective of the treatment and variety. The TSS for fruits under poor cold chain practices increased from the initial 8.47°Brix, 6.7°Brix, 5.63°Brix, and 8.7°Brix to 22.63°Brix, 20.23°Brix, 13.9°Brix, and 18.23°Brix for Apple, Ngowe, Kent, and Tommy Atkins varieties, respectively, at the end of storage while for fruits under proper cold chain practices they increased to 19.43°Brix, 20.2°Brix, 14.03°Brix, and 15.90°Brix for ‘Apple’, ‘Ngowe’, ‘Kent’, and ‘Tommy Atkins’ varieties, respectively, at the end of storage (Table 7).

Table 7: Changes in total soluble solids (TSS) of four mango varieties as affected by cold chain management practices.

Variety
Treatment
Days in storage
Means

0
3
6
9
12
15
18
21
24
27
30
33

Apple
Cold chain
8.47c
8.60bc
10.03b
10.10b
10.20b
12.13b
13.13bcd
14.20bc
15.00b
15.10b
19.43b

12.40

No cold chain
8.47c
9.07bc
12.93c
13.37d
22.63g

13.29

Kent
Cold chain
5.63a
6.63a
6.67a
6.80a
8.97a
9.20a
10.43a
11.17a
11.53a
13.00a
13.33a
14.03
9.78

No cold chain
5.63a
7.10bc
9.40b
11.50bc
12.80c
13.90cd

10.06

Ngowe
Cold chain
6.70b
10.10c
10.93b
11.53c
14.80d
15.90e
16.63de
16.93c
17.83c
18.03c
20.20b

14.51

No cold chain
6.70b
13.67e
17.47d
19.73e
20.23f

15.56

Tommy Atkins
Cold chain
8.70c
9.00b
9.33a
9.73b
10.40a
11.33cd
12.07ab
13.17ab
13.20a
14.67b
15.90a

11.59

No cold chain
8.70c
11.97d
12.23c
15.20d
18.23e

13.27

Treat x variety (LSD 0.05) CV (%)
0.85
1.34
1.53
1.66
1.13
1.07
2.93
3.00
1.59
1.65
3.18
2.68

6.70
8.00
8.30
7.60
4.50
4.50
11.90
12.00
5.90
5.60
9.80
5.40

Means within each column followed by different letters differ significantly at  > 0.05.

3.7. Overall Shelf Life

The overall shelf life was determined by the number of days to a predetermined end-stage for the fruits based on firmness and visual appearance at which the fruit was saleable. Fruits under poor cold chain practices had a shorter shelf life of 12 days for ‘Apple’, ‘Ngowe’, and ‘Tommy Atkins’ varieties and 15 days for ‘Kent’ variety. On the other hand, fruits under proper cold chain practices had a longer shelf life of 30 days for ‘Apple’, ‘Ngowe’, and ‘Tommy Atkins’ varieties and 33 days for ‘Kent variety’ (Figure 2).

Figure 2: Overall shelf life of four mango varieties (‘Apple’, ‘Kent’, ‘Ngowe’, and ‘Tommy Atkins’) handled either under proper cold chain management or under poor cold chain management practices. Top bars represent SE of means ( ≤ 0.05).

4. Discussion

Temperature management to maintain a proper cold chain for fresh horticultural produce is key to preserving quality and reducing postharvest losses in perishable commodities [21]. For smallholder horticultural farmers with limited resources, simple harvest practices coupled with low-cost cold storage can be used to achieve a desirable cold chain. In the present study, the effectiveness of these practices and technologies was evaluated in mango fruits. The study evaluated proper cold chain practices or poor cold chain practices (farmer practices) in four mango varieties, namely, ‘Apple’, ‘Ngowe’, ‘Kent’, and ‘Tommy Atkins’. The effect of the two cold chain options (proper and poor cold chain) on ripening related changes (physiological weight loss, hue angle, firmness, and total soluble solids) and the overall shelf life of the fruits was evaluated.

Harvest time greatly affected the pulp temperature with fruits harvested during hotter hours of the day recording high pulp temperatures due to high heat load. Horticultural produce accumulates heat during harvesting and postharvest handling, which reduces their storage quality [22]. High heat load is one of the major causes of deterioration in harvested commodities. Harvesting and handling the harvested produce under cool temperatures are critical for postharvest quality preservation [12]. Harvested produce should be precooled or cooled immediately after harvest. Fruits harvested during hot hours of the day should be precooled immediately to remove field heat and slow physiological processes [23]. Previous studies have shown that delayed cooling for just one hour can result in a one-day loss of shelf life [24]. Precooled fruits have reduced metabolic activities rate leading to quality preservation and shelf life extension [17]. Precooling can be done either by hydrocooling, vacuum cooling, or forced air cooling, depending on the commodity and cost-benefit associated with it [25]. For smallholder farmers, evaporative coolers can be used to precool fruits and vegetables prior to refrigerated transport and storage. Precooling also improves cold-resisting ability and minimizes chilling injury on fresh produce. A rapid removal of field heat by precooling before storage is critical for the efficient running of the cold storage facility. Evaporative coolers have been used to achieve cool temperatures necessary for precooling and short-term storage of harvested horticultural produce [26].

Proper cold chain management significantly reduced the rate of ripening-related changes, including physiological weight loss, peel and flesh colour, peel and flesh firmness, and increase in TSS, ultimately increasing the shelf life of mango fruits by an additional 18 days.

Although there was a gradual increase in physiological weight loss during storage irrespective of the treatment, the rate was slower under proper cold chain management. Physiological weight loss in harvested commodities results in shorter shelf life and loss of quality through wilting and shriveling [27]. The higher weight loss in fruits under poor cold chain management practices can be attributed to high temperatures and low humidity. The rate of physiological weight loss and shriveling is dependent on respiration and transpiration and is accelerated with high temperature and low humidity [28]. Under proper cold chain management practices, minimal water loss through transpiration and substrate breakdown during respiration resulted from low temperatures and high humidity. This condition creates a low vapour pressure deficit (VPD) for the fruits and the area around the fruit, leading to slowed water loss from the fruits to the surrounding air. Similar results of reduced water loss under low temperatures and high humidity have been reported in mango [17] and avocado [29].

Colour is an important indicator of ripeness and freshness among fruits. In the present study, peel and flesh color (measured as hue angle) gradually decreased as fruits ripened irrespective of the treatment (cold chain practice) and variety. The decrease in hue angles was steady in fruits subjected to poor cold chain management practices, hence shorter shelf life. The slower color change in fruits under proper cold chain management practices can be attributed to low temperatures leading to reduced metabolic activities. Low temperatures also slow down ethylene biosynthesis and processes triggered by ethylene in ripening fruits chlorophyll degradation by chlorophyll oxidase [30]. Artes et al. [31] also attribute the colour change to delay in the biosynthesis of anthocyanins and carotenoids resulting from the reduced metabolic processes due to low temperatures in proper cold chain practices. The inhibition of metabolic and enzymatic reactions responsible for ripening due to low temperature has previously been reported in mango [32] and indigenous fruits such as Ber [33].

Peel and flesh firmness decreased as fruits ripened irrespective of the treatment and variety. At the end-stage for fruits under poor cold chain practices, firmness had decreased to less than 50% while those under proper cold chain practices remained firmer till day 30 ('Apple', 'Ngowe', and 'Tommy Atkins') and day 33 ('Kent') varieties, respectively. The decrease in fruit firmness is attributed to activities of enzymes involved in cell metabolism, depolymerization of cell wall pectin [34]. The enzymes include pectin methylesterase (PME), polygalacturonase (PG), endo-B-1,4-glucanase (EGase), and pectate lyase [35]. The high firmness retention in fruits under proper cold chain management practices results from low temperatures that could have slowed down the activities of the enzymes involved in ripening. Reduced transpiration in fruits under proper cold chain due to high humidity and low temperature could also explain the high firmness in fruits stored under such conditions since they remained turgid due to minimal moisture loss [36]. The finding of the present study is in line with previous studies on the effect of low temperatures on the firmness of mango [17] and avocado [29].

Total soluble solids increased gradually in all the treatments. An increase in TSS is attributed to starch breakdown into simple sugar as ripening progress [37]. Fruits under poor cold chain practices had a faster increase in TSS and over a shorter period of time as compared to those under proper cold chain practices. For example, 'Apple' mango under poor cold chain practices had TSS of 22.63oBrix on day 12, compared to 19.43oBrix on day 30 under proper cold chain management. A high increase in TSS of fruits under warmer conditions in poor cold chain management could be attributed to a high respiration rate and other metabolic activities. The increase can also be attributed to higher activity on enzymes (sucrose synthase, invertase, and amylase) involved in starch breakdown [38]. TSS is varietal-dependent, hence the observed significant difference among the four mango varieties used in the present study [36]. The finding of this present study concurs with similar studies previously done on mango [17] and grapefruit [39].

Overall, proper cold chain practices extended the shelf life of mango fruits (all varieties) which remained saleable until day 30 ('Apple', 'Ngowe', and 'Tommy Atkins') and day 33 ('Kent'). This was 18 more than fruits under poor cold chain practices. The shelf life of fruits under proper cold chain practices was enhanced by a synergistic effect of proper time of harvest, precooling, storage at low temperature, and high humidity. This in turn reduced the rate of ripening and deterioration of the fruits during storage.

5. Conclusion

Application of simple harvest and postharvest handling practices coupled with simple low-cost cold storage technologies can achieve desirable cold chain in perishable commodities such as mango. Proper cold chain practices significantly maintained lower internal pulp temperatures (averaging 11°C) when compared to poor cold chain practices (averaging 25°C), thus lowering metabolic reactions that still take place in harvested fruits that result in faster ripening and deterioration. This can in turn extend the shelf life of the perishable commodities and significantly increase their marketing period while reducing postharvest losses. Overall, proper cold chain management preserved quality (water loss, firmness, colour, and TSS) and extended shelf life of harvested mango fruits by 18 days more when compared to handling practices common among smallholder farmers. These practices and technologies can be adopted by smallholder farmers especially those doing aggregation of fruits for later selling and/or processing, thus enabling high bargaining power that results in better returns.

Data Availability

The data used in this manuscript are available upon request to the first author (emmanuelamwoka@gmail.com) and the corresponding author (ambuko@yahoo.com).

Conflicts of Interest

The authors declare that there are no conflicts of interest.

Acknowledgments

The authors are grateful to the Karurumo horticultural farmers’ self-help group for allowing them to use their aggregation centre during this study. The funding of this research was provided by the Rockefeller Foundation under Yieldwise Initiative (Grant number: 2016 YWS 328) awarded to Prof. Jane Ambuko of the University of Nairobi.

References

Horticultural Crops Directorate (HCD), Validated Report 2016-2017, Horticultural Crops Directorate (HCD), Kenya, 2017.

FAO, “Food losses and waste in the context of sustainable food systems. High Level Panel of Experts (HLPE),” FAO, Rome, Italy, 2014, Report 8.

M. Reid, J. Thompson, and C. Chih-Ham, Small-scale Coolrooms and Cool Transport for Limited Resource Farmers, 2010.

L. Kitinoja, Use of Cold Chains for Reducing Food Losses in Developing Countries, no. 13, AMAIZZ, Tel Aviv, Israel, 2013.

A. A. Kader, “Postharvest technology of horticultural crops,” Agriculture and Natural Resources, vol. 3311, pp. 533–535, 2002.

R. Lufu, A. Ambaw, and U. L. Opara, “Water loss of fresh fruit: influencing pre-harvest, harvest and postharvest factors,” Scientia Horticulturae, vol. 272, 2020.

S. Tyagi, S. Sahay, M. Imran, K. Rashmi, and S. Mahesh, “Pre-harvest factors influencing the postharvest quality of fruits: a review,” Current Journal of Applied Science and Technology, vol. 23, no. 4, pp. 1–12, 2017.

H. Deirdre, Water Relations in Harvested Fresh Produce, University of California, Davis, Davis, CA, USA, 2015.

V. Kiaya, “Post-harvest losses and strategies to,” The Journal of Agricultural Science, vol. 149, no. 3–4, pp. 49–57, 2014.

O. gumo, C. N. Kunyanga, J. W. Kimenju, and M. W. Okoth, “Effects of harvest time and duration before cooling on the post-harvest quality and shelf-life stability of French bean (Phaseolus Vulgaris L.),” Journal of Nutrition & Food Sciences, vol. 8, no. 5, 2018.

Z. S. Ilić, L. Milenković, L. Šunić, and M. Manojlović, “Color shade nets improve vegetables quality at harvest and maintain quality during storage,” Contemporary Agriculture, vol. 67, no. 1, pp. 9–19, 2018.

I. Kojo, A. Harrison, K. Ernest Kodzo, and H. Ofori, “Preharvest and postharvest factors affecting the quality and shelf life of harvested tomatoes: a mini review,” International Journal of Agronomy, vol. 2015, Article ID 478041, 6 pages, 2015.

E. Pressman, M. M. Peet, and D. Mason Pharr, “The effect of heat stress on tomato pollen characteristics is associated with changes in carbohydrate concentration in the developing anthers,” Annals of Botany, vol. 90, no. 5, pp. 631–636, 2002.

Z. Yang, Z. Ma, C. Zhao, and Y. Chen, “Study on forced-air pre-cooling of longan,” in Proceedings of the 2007 ASAE Annual Meeting American Society of Agricultural and Biological Engineers, Minneapolis, MI, USA, June 2007.

K. Cherono, M. Sibomana, and S. W. Tilahun, “Effect of infield handling conditions and time to pre-cooling on the shelf-life and quality of tomatoes,” Brazilian Journal of Food Technology, vol. 21, 2018.

N. Dubey, Technologies for Horticultural Development: CoolBot Provides Inexpensive, Effective Cooling, University of California, Davis, Davis, CA, USA, 2011, http://hortcrsp.ucdavis.edu/main/media/technologies_CoolBot.pdf.

J. Ambuko and E. Karithi, “Postharvest shelf life of mango fruits stored in a CoolbotTM cold room,” Acta Horticulturae, vol. 1225, 2018.

A. lal Basediya, D. V. K. Samuel, and V. Beera, “Evaporative cooling system for storage of fruits and vegetables - a review,” Journal of Food Science and Technology, vol. 50, no. 3, pp. 429–442, 2013.

A. Jane, F. Wanjiru, G. N. Chemining’wa, W. O. Owino, and E. Mwachoni, “Preservation of postharvest quality of leafy amaranth (Amaranthus spp) vegetables using evaporative cooling,” Journal of Food Quality, vol. 2017, Article ID 5303156, 6 pages, 2017.

F. Manyoo and J. Ambuko, “Effectiveness of evaporative cooling technologies to preserve the postharvest quality of tomato,” International Journal of Agronomy and Agricultural Research, vol. 13, 2018.

M. M. Aung and Y. S. Chang, “Temperature management for the quality assurance of a perishable food supply chain,” Food Control, vol. 40, pp. 198–207, 2014.

J. H. Venema, P. Linger, A. W. Heusden, P. R. Hasselt, and W. Brüggemann, “The inheritance of chilling tolerance in tomato (lycopersiconspp.),” Plant Biology, vol. 7, no. 2, pp. 118–130, 2005.

C. T. Kathryn and W. R. James, Harvesting and Handling Peaches, University of Georgia, Athens, Georgia, 2004, http://www.ent.uga.edu/peach/peachhbk/harvest/harvestandhandle.pdf.

G. I. Johnson and P. J. Hofman, “Postharvest technology and quarantine treatments,” in The Mango: Botany, Production and Uses, R. E. Litz, Ed., p. 529605, CABI, Wallingford, UK, second ed. edition, 2009.

B. J. Jobling, “Correct cool chain management is essential for all fruit and vegetables,” Sydney Postharvest Laboratory, Sydney, Australia, 2001.

B. G. Jahun, S. A. Abdulkadir, S. M. Musa, and H. Umar, “Assessment of evaporative cooling system for storage of vegetables,” International Journal of Science and Research (IJSR), vol. 5, no. 1, pp. 1197–1203, 2016.

H. A. Rathore, T. Masud, S. Sammi, and A. Hussain Soomro, “Effect of storage on physico-chemical composition and sensory properties of mango (mangifera indica L.) variety dosehari,” Pakistan Journal of Nutrition, vol. 6, no. 2, pp. 143–148, 2007.

E. Abiso and N. AtheeshH. Addisalem, ““Effect of storage methods and ripening stages on postharvest quality of tomato ( lycopersicom esculentum mill ) cv . Chali effect of storage methods and ripening stages on postharvest tomato (Lycopersicom Esculentum L .) is botanically classified as a Fr.,” Annals Food Science and Technology, vol. 16, no. 1, pp. 127–137, 2015.

R. J. Blakey, J. P. Bower, and I. Bertling, “Importance of cold chain maintenance and storage temperature to avocado ripening and quality,” Acta Horticulturae, vol. 911, no. 911, pp. 555–564, 2011.

R. M. Beaudry, “Responses of horticultural commodities to low oxygen: limits to the expanded use of modified atmosphere packaging,” HortTechnology, vol. 10, no. 3, pp. 491–500, 2000.

F. Artés, P. A. Gómez, and F. Artés-Hernández, “Modified atmosphere packaging of fruits and vegetables,” Critical Reviews in Food Science and Nutrition, vol. 28, pp. 1–13, 2006.

O. Hafeez, “Impact of different packaging types and low temperature shipping durations on fruit quality and marketability of Pakistani mangoes,” International Journal of Agriculture and Biology, vol. 14, no. 1, pp. 47–54, 2012.

L. Tembo, “Storage temperature affects fruit quality attributes of ber (Ziziphus mauritiana lamk.) in Zimbabwe,” African Journal of Biotechnology, vol. 7, no. 17, pp. 3092–3099, 2008.

B. Jarimopas and U. Kitthawee, “Firmness properties of mangoes,” International Journal of Food Properties, vol. 10, no. 4, pp. 899–909, 2007.

H. Lazan, M. K. Selamat, and Z. M. Ali, “beta-Galactosidase, polygalacturonase and pectinesterase in differential softening and cell wall modification during papaya fruit ripening,” Physiologia Plantarum, vol. 95, no. 1, pp. 106–112, 1995.

M. Tigist, T. S. Workneh, and K. Woldetsadik, “Effects of variety on the quality of tomato stored under ambient conditions,” Journal of Food Science and Technology, vol. 50, no. 3, pp. 477–486, 2013.

M. W. Siddiqui and R. S. Dhua, “Standardization of ethrel treatment for inducing ripening of mango var. Himsagar,” in Proceedings of the International Conference on Horticulture, Nanjing, China, January 2009.

S. Kumar, D. K. Das, A. K. Singh, and U. S. Prasad, “Sucrose metabolism during maturation and ripening of mango cultivars,” Plant Physiology and Biochemistry, vol. 21, no. 1, pp. 27–32, 1994.

O. Pailly, G. Tison, and A. Amouroux, “Harvest time and storage conditions of 'Star Ruby' grapefruit (Citrus paradisi Macf.) for short distance summer consumption,” Postharvest Biology and Technology, vol. 34, no. 1, pp. 65–73, 2004.