Effect of Natural Edible Oil Coatings and Storage Conditions on the Postharvest Quality of Bananas

Abstract

Increasing the shelf-life of fruits and vegetables using edible natural substances after harvest is economically important and can be useful for human health. Postharvest techniques help maintain the quality of edible tissues resulting in extended marketing periods and reduced food waste. The edible coating on perishable commodities is a common technique used by the food industry during the postharvest supply chain. The objective of this research was to study the effect of edible oil to minimize the loss of postharvest physio-chemical and nutritional attributes of bananas. The study selected two banana cultivars (Musa, ‘Cavendish’ and ‘Milk’) to conduct this experiment, and two edible oils (olive oil (Olea europaea) and moringa oil (Moringa peregrina)) were applied as an edible coating under two different storage conditions (15 and 25 °C). The fruit’s physio-chemical properties including weight loss, firmness, color, total soluble solids (TSS), pH, titratable acidity (TA), TSS: TA ratio, and mineral content were assessed. The experiment lasted for 12 days. The physicochemical properties of the banana coated with olive and moringa oils were more controlled than the non-coated (control) banana under both storage temperatures (15 °C and 25 °C). Coated bananas with olive and moringa oils stored at 15 °C resulted in further inhibition in the ripening process. There was a decrease in weight loss, retained color, and firmness, and the changes in chemical parameters were slower in banana fruits during storage in the olive and moringa oil-coated bananas. Minerals were highly retained in coated Cavendish bananas. Overall, the coated samples visually maintained acceptable quality until the final day of storage. Our results indicated that olive and moringa oils in this study have the potential to extend the shelf-life and improve the physico-chemical quality of banana fruits.

1. Introduction

Banana (Musa sp.) belongs to the Musaceae family and it is considered one of the important tropical fresh fruit worldwide. Banana fruit is one of the delicious and favored fruits by consumers of all ages that is eaten in various forms (dry and fresh) [1]. In addition, it is the cheapest, highly nourishing fresh fruit, a rich source of energy, and easy to digest compared to other fresh fruit, namely, apples. Banana is also known for its popular aroma, texture, and ease to peel and eat [2]. Banana serves as a stable food product for more than 4 hundred million people worldwide [3], with documented 12.2 million tonnes of global export in the period of January to July 2020 [4]. Also, the banana is a fruit with the highest production (127.3 million tonnes) worldwide and ranked fourth in terms of other agricultural commodities values (63.6 billion US$) after rice, wheat, and milk [5].

Bananas are categorized as climacteric fruit, and they continue to ripen after harvest. Thus, banana bunches are collected and gathered when they become fully green to tolerate postharvest handling like storage, transport, etc. [6]. The high nutritional content of banana fruit makes it extremely susceptible to diseases resulting from microorganisms. Storing banana fruit at low temperatures can lead to banana damage and this will have a critical influence on the storage and marketing of the fruit [7]. When a banana begins to ripen, it suffers many chemical and physical alternations and synthesizes various volatile compounds that directly change the visual color of the fruit. These changes could occur during the process of fresh produce distribution. Thus, ripening and browning are considered series quality problems during banana storage [8]. Generally, the postharvest storage of bananas is short, which can lead to huge economic and postharvest losses resulting in a global challenge of banana agriculture [9].

The rising demand for fresh produce forces food industries to provide better and new ideas and techniques for controlling the quality and extending the shelf life of fresh produce [10]. Many postharvest technologies were used to enhance the quality and improve the shelf life of bananas like chemical treatments, controlled atmosphere storage, ethylene antagonists, low storage temperature, and edible coatings. Some of the mentioned techniques in banana fruit preservation can lead to unexpected consequences and customers’ dissatisfaction as living standards have progressively improved [9]. The majority of these techniques have several limitations including uneven ripening, high cost, and chilling injuries [11]. Also, consumers around the world need to consume food of high quality with no use of chemical preservatives [10]. Among these methods, edible coating, as a natural preservative, has emerged as a promising option because of its cost-effectiveness, eco-friendliness, safety, and other extra characteristics like antimicrobial and antioxidant activity [11].

An edible coating (EC) is known as a thin layer coating on the surface of fresh produce via dipping, spraying, brushing, etc., to offer physical protection while barring the permeation of water vapor, gas, and solvents [10,12]. In addition, edible coating (EC) can be classified into polysaccharide-based, lipid-based, and protein-based coatings. EC may also be used as composites or in a layer-by-layer approach. Previous studies have proved that the application of EC provided an excellent block to moisture, gas, and solute migration, and extended the quality of fresh produce [13]. The thin layers can produce a modified atmosphere surrounding the coated fruit because of their semi-permeable layer to different gases like O₂, CO₂, and C₂H₄ [14]. Extensive research has demonstrated the efficiency of EC (polysaccharides and proteins) like pectin/agarose-based coating [15], aloe vera, starch, and Arabic gum [16], and soybean protein [17] in preserving banana fruit by protecting it from microbial and mechanical damage, improving the fruit’s appearance, retaining volatiles, and delaying quality deterioration [15,16,17,18]. Also, EC can enhance the appearance of fresh fruit, providing it with gloss features and avoiding changes in color attributes. It has been reported that edible coating can provide an effective performance in delaying the ripening, prolonging the storability of bananas [19], and retaining flavor sugars, and organic acids [7]. Shrimp chitosan is one of the polysaccharide-based edible coatings applied for banana fruit as investigated by [20]. Their study recorded delayed changes in acidity, pH, and weight loss. The application of chitosan coating prevents microbial decay and Maintains sensory qualities during storage.

Vegetable oils like olive oil, sunflower oil, maize oil, and rapeseed oil are highly accessible, nonvolatile, inexpensive, nontoxic, non-depletable, and a source of monounsaturated fatty acids; thus, their application as an edible coating on fresh fruit and vegetables has been related to a diversity of health advantages [21]. Also, it has been stated that edible oils like coconut, olive, custard, butter, paraffin, etc., are utilized for fruit and vegetable coating [22]. Moringa oil is another edible coating that is specifically extracted from moringa seeds. Moringa oils consist of various compositional properties like antioxidants, phenolic content, proteins, etc. Moringa oil is a promising low-cost material that is applied to reduce detrimental microorganisms from fresh produce. It was stated that the application of moringa oil decreases and eliminates decay, elevates the marketability of tomato [23], prolongs the postharvest shelf life, and maintains the quality of mango fruit [24] by controlling the physicochemical and physical attributes during storage compared to the control treatment. In addition, coating the fruit with moringa oil slows down the breakdown of pigments, allowing the coated fruit to gain shine [25]. Olive oil is another natural edible coating applied to fresh produce that has antifungal properties for enhancing postharvest life [26]. Olive oil (alone or in combination) has been used to increase the shelf life and maintain the quality of apples [27], bananas [22], table grapes [28], and sweet cherries [29]. The study by [28] stated that Xanthan gum combined with olive oil decreased the weight loss, decay incidence, and accumulation of total soluble solids and total sugars by dropping the rate of respiration and metabolism in the coated fruit.

Although bananas are a widely consumed tropical fruit, they are extremely perishable because of their climacteric nature and sensitivity to moisture loss, mechanical damage, microbial spoilage, and fast ripening [2]. Edible natural coatings like moringa oil and olive oil have emerged as an effective, eco-friendly postharvest strategy to extend the shelf life of fruits by acting as semi-permeable barriers to moisture and gases [21]. Despite their potential, only a few studies have examined the influence of moringa and olive oil edible coatings on the quality of banana fruit. Thus, this research was carried out to understand the effect of these natural edible coatings on the physiochemical quality characteristics (weight, color, texture, total soluble solids, titratable acidity, sugar: acid ratio, pH, and mineral content) of two banana cultivars, namely, milk and cavendish, during 12 days at 15 and 25 °C.

2. Material and Methods

2.1. Fruit Supply

Two banana cultivars were obtained during the summer season in the month of June from the central fruit and vegetable market in Al-Mawalih, Muscat, Oman. The two cultivars were ‘Milk’ (locally produced in Dhofar, Oman) and ‘Cavendish’ (imported from India). The fruits were transported in an air-conditioned vehicle to the Crop Production Research Laboratory located in the College of Agricultural and Marine Sciences at Sultan Qaboos University, Oman. Bananas selected for this study were at the mature green stage, the stage available in the market for wholesale. The selected fruits were uniform in shape, size, and color. All samples were washed with distilled water and then sterilized with chlorine (10%), then left to dry before treatment. A total of 144 banana fruits were used from each cultivar.

2.2. Edible Coating and Storage Treatments

In this study, locally produced olive oil and moringa oil (M. peregrina oil) (100% purity—virgin) were applied to the banana fruits as an edible coating. The olive oil was purchased from a farmer from Wilayat Jabal Al Akhdar, Ad Dakhiliyah Governorate, Oman, and moringa oil (M. peregrina) was purchased from Abna Freish Centre, Seeb, Muscat, Oman. A camel hairbrush was used to apply oils to all samples once, taking into account covering all parts of the fruit evenly.

Fruits were randomly divided into three groups (48 fruits per group), the first group was set as control (not coated), the second group was coated with olive oil, and the third group was coated with moringa oil. They were further divided into two sub-groups (24 fruits in each), one group was placed at room temperature (25 °C and 82–85% RH) and the second half was placed in refrigerated storage (15 °C and 95.5% RH), which is the approximate banana storage temperature [30]. Both temperature and relative humidity were monitored and controlled during the 12 days storage period by using the temperature meter (Model: TES 13604, TES Electrical Corp., Taiwan, China).

2.3. Measurements of Fruit Quality Attributes

The experiment was conducted for 12 days, and the measurements were taken every two days. The total number of treatments was 12, where 3 replicates were used per treatment per day. The measurements of physical properties (weight loss %, color, and firmness), and chemical properties (total soluble solids (TSS), titratable acidity (TA), TSS: TA ratio, pH), and minerals composition (K, Na, Ca) were analyzed.

2.3.1. Physical Properties

Weight Loss (%)

The weight loss (%) and mass (g) of three samples per treatment was measured every 2 days using an electronic balance (PM-2000, Mettler, Tokyo, Japan). The changes in fruit mass were expressed as a percentage of weight loss using the following equation (Equation (1)):

$$\mathrm{Weight}\mathrm{loss}(\%)={\displaystyle \frac{Initialweightofsample-finalweightofsample}{Initialweightofsample}}\times 100$$

(1)

Color

Fruit images were taken using the camera of the iPhone X (Apple Inc., Cupertino, CA, USA) device by installing the device at a fixed height in a lightbox. During the image capture, samples were placed manually on a white background. The white background was used to provide high contrast between the banana sample and the background. Then, the images were transferred to a computer for analysis [31]. Two images were taken, one from each side for each sample. ImageJ software (v. 1.53) was used to determine RGB color values that were then converted to CIE L*, a*, b* values. The mean of individual values of L* is a measure of lightness: L* = 0 (black) to L* = 100 (white), a* (−a* is greenness, +a* is redness) and b* (−b* is blueness, +b* is yellowness) [31], hue angle (h*^ab) and (C^ab) chromaticity (saturation) calculations were expressed by the following equations (Equations (2) and (3)):

C^ab = (a*² + b*²)^1/2

(2)

h*^ab = tan⁻¹(b*/a*)

(3)

Hue angle (h*^ab) describes the color perception and chroma (C^ab) describes the saturation of color [32].

Texture

The texture (firmness) of the banana fruit was evaluated using a digital fruit firmness tester (Model: FHP-803, Agriculture Solution, Franklin, ME, USA), and the value was expressed in kgf. Three readings were taken per sample.

2.3.2. Chemical and Nutritional Properties of Banana

Sample Preparation

A sample of 30 g of banana pulp tissue was blended with 90 mL of distilled water in a kitchen blender (OT-MJ176, GEEPAS, Guangzhou, China) for 2 min. The diluted banana juice was centrifuged (Centrifuge 5702R, Eppendorf, Hamburg, Germany) for 2 min at 23 °C. Thereafter, the supernatant was used to measure TSS, pH, and TA.

Total Soluble Solids (TSS)

TSS was measured using a pocket refractometer (Model: PAL-1 Digital Hand-Held, Atago, Tokyo, Japan). Three readings were taken from each sample, then multiplied by three because the sample was diluted three times during preparation [1].

Titratable Acidity (TA)

The TA of banana juice was obtained by titration method [33]. From each sample, 20 mL were titrated against 0.1 N NaOH, using 3 to 4 drops of phenolphthalein as an indicator. The endpoint was recorded (color change to light pink). TA was recorded as a percentage of malic acid as calculated using the following equation (Equation (4)):

$$\%\mathrm{Acid}={\displaystyle \frac{(C\times 100\times \mathrm{mL}ofNaOH\times NofNaOH)}{\mathrm{mL}ofsample}}\times D$$

(4)

(C = 0.067 (constant of malic acid), mL of NaOH = volume of NaOH used, N of NaOH = 0.1, D (dilution factor) = ${\displaystyle \frac{finalvolume}{wtofsample}}$).

TSS: TA Ratio

The ratio between TSS and TA was calculated by dividing TSS values by the TA values of the same sample fruit.

pH

The pH of the diluted banana juice was measured by using a bench pH meter (Jenway 3510, Fisher Scientific Ltd., Loughborough, UK).

Mineral Content

Banana pulp and peel were dried in the oven for 24 h at 120 °C, then 0.2 g of dry pulp and peel samples were weighed, placed in 10 mL of nitric acid added, and left until all tissues dissolved. Samples were then transferred to a 45 mL tube and filled with distilled water. Concentrations of 0 were analyzed using a flame photometer (Techne 500701 Pfp7 Industrial, 230V, Staffordshire, UK). Mineral content analysis was performed for pulp and peel samples from fruits on day two and day four of the experiment [34].

2.4. Data Analysis

The data presented in this paper was statistically analyzed by SAS 17 software (SAS Institute, Cary, NC, USA) and the mean and standard deviation (SD) were calculated. The statistical significance of the data was assessed by the Analysis of Variance to determine the significant effect of the four factors (independent variables) including edible coating, cultivars, storage temperature, and storage time on banana fruit physical (weight, firmness, color) and chemical (pH, TSS%, TA%, TSS: TA ration) quality parameters (dependent variables). Duncan Multiple Range Test (DMRT) was applied to determine the significant differences between treatment means. A p-value of 0.05 was used for all the analyses in this study.

3. Results and Discussion

3.1. Physical Properties

3.1.1. Weight Loss

Figure 1 shows the weight loss % of coated (moringa oil, olive oil) and non-coated (control) two banana cultivars (Cavendish, Milk) stored at 15 and 25 C for 12 days. The changes in banana weight loss differed significantly and were affected by the studied factors (coating, cultivar, storage temperature, and storage time) (

Table 1. Physical properties values and significance levels for two banana cultivars stored under two temperatures and treated with different edible oils. Means with different uppercase letters indicate a significant difference at p < 0.05.

Physical Parameters	Weight Loss (%)	Firmness (kgf)	Color Measurements
			L*	a*	b*	Chroma	Hue
Coating
C	6.23 A	3.18 C	66.78 A	2.89 B	52.31 C	52.58 C	1.07 A
Mo	5.29 B	4.14 A	63.39 B	2.93 B	59.43 B	59.92 B	0.87 B
Oo	5.28 B	4.02 B	63.68 B	3.47 A	60.41 A	60.87 A	0.87 B
p-value	>0.001	>0.001	>0.001	>0.001	>0.001	>0.001	>0.001
Cultivar
Cav	5.49 B	3.37 B	62.30 B	5.71 A	58.45 A	58.89 A	1.23 A
Milk	5.71 A	4.20 A	66.93 A	0.49 B	56.31 B	56.69 B	0.65 B
	=0.01	>0.001	>0.001	>0.001	>0.001	>0.001	>0.001
Storage temp.
15 °C	4.47 B	4.46 A	65.23 A	1.87 B	58.04 A	58.48 A	0.79 B
25 °C	6.73 A	3.11 B	64.00 B	4.34 A	56.73 B	57.10 B	1.09 A
p-value	>0.001	>0.001	>0.001	>0.001	>0.001	>0.001	>0.001
Interaction
Tem*Cult	=0.990	=0.800	>0.001	>0.001	>0.001	>0.001	>0.001
Tem*Coat	=0.420	>0.001	>0.001	>0.001	>0.001	>0.001	>0.001
Cult*Coat	=0.010	>0.001	>0.001	>0.001	=0.070	=0.090	=0.22
Tem*Cult*Coat	>0.001	>0.001	>0.001	>0.001	>0.001	>0.001	0.00

Cav = Cavendish banana, Milk = Milk banana, C = control (non-coated), Mo = moringa oil, Oo = olive oil, Tem = temperature, Cult = cultivar, Coat = coating.

). The differences in weight loss (%) were significant between untreated and oil-coated bananas (6.23%, 5.28%, and 5.29% for control, olive, and moringa oil, respectively), and no significant difference between olive and moringa oils treatments (Figure 1A). This indicates that the non-coated bananas showed a higher reduction in weight during the 12 days of storage compared to the coated ones. In terms of banana cultivar, Cavendish bananas had significantly lower weight loss than Milk bananas (Figure 1B) which was highly observed after 8 days of storage. Furthermore, at a temperature of 15 °C, the weight loss of banana fruit was significantly less than that at 25 °C (Figure 1C). The oil-coated bananas had lower weight loss compared to the control under both temperatures. The lowest weight loss was found in fruits coated with moringa oil and stored at 15 °C. Results also indicated that the fruit weight loss decreased as temperature decreased in the examined cultivars as the experiment lasted. At 15 °C, the Cavendish banana indicated a significant reduction in weight loss by 34.29% compared to 25 °C. The Milk banana, at 15 °C, showed a reduction of 33.04% in weight loss. Compared to the uncoated fruits, the Cavendish banana showed a reduction in weight loss by 13.37% and 18.27% when coated with moringa and olive oil, respectively. On the other hand, the Milk banana showed 16.77% and 12.02% reduction when coated with moringa oil and olive oil, respectively, compared to the non-coated bananas.

This observed reduction in bananas could be generally attributed to a reduction in the transpiration rate. It has been confirmed that the transpiration increment during storage can cause a decrease in the water content of banana fruit peels. Thus, water will be transported to the pulp of the fruit which decreases the weight of the peel. Also, ethylene can affect the water content of the fruit by accelerating polysaccharides hydrolysis cell wall forming water on the fruit and increasing water in the fruit during the ripening process [1], which is highly recorded at higher storage temperatures. Regarding coating, similar findings were found by [35] who reported that olive oil decreased ‘Ber’ fruit (Ziziphus mauritiana) weight loss and extended their storage life. The reduction in weight loss for olive oil-coated fruits is likely attributed to the coatings acting as semi-permeable barriers, limiting the movement of carbon dioxide, oxygen, moisture, and solutes, which in turn decreases respiration rates and moisture loss, leading to overall weight retention [36].

Another study by [22] stated that edible coating significantly reduces respiration and transpiration rates, resulting in a weight loss decrease of up to 65% compared to control samples in Tsugaru apples. The non-coated apples experienced greater weight loss due to higher rates of transpiration and respiration, while coating creates a barrier between the internal and outer environment that assists in maintaining fruit weight during storage. Also, the outcomes of the study align with research by [37], which highlights that oil coatings (butter) possess hydrophobic properties, effectively minimizing weight loss in mangoes.

3.1.2. Firmness

The firmness of the banana fruit gradually reduced throughout the storage time (Figure 2). The firmness values of this study were statistically significant (p < 0.05) with all independent variables (coating, cultivar, storage temperature, and storage days) (Table 1). Firmness showed a significant change between bananas with the coating (moringa oil and olive oil) and with no coating (control) (Figure 2A). Bananas coated with olive oil showed less reduction in firmness during the first 6 days of storage, while bananas coated with moringa oil had the highest firmness values on days 8, 10, and 12. The non-coated bananas showed a gradual reduction in the firmness status during the whole storage period especially in those stored at ambient conditions. Furthermore, firmness was significantly higher in Milk bananas compared to Cavendish (Figure 2B). The firmness value of banana fruit stored at 15 °C was statistically higher than those stored at 25 °C (Figure 2C). Banana fruit that coated with moringa oil and stored at 15 °C had the highest firmness (4.85 kgf), whereas the lowest firmness value was observed in the non-coated bananas stored at 25 °C (2.36 kgf). Significantly, the firmness declined as temperature increased in coated Cavendish and Milk bananas. For Milk bananas, the firmness was reduced by 54.06% and 38.65% when coated with moringa oil at 25 °C and 15 °C, respectively.

Fruit firmness is the main determinant of the shelf life and quality of bananas. Firmness changes are commonly related to the hydrolysis of starch to sugar and degradation of pectin during fruit ripening, so, cell turgor pressure decreases [38]. Other studies found that banana fruit coated with Aloe vera gel with garlic essential oil was firmer than the uncoated fruit [39]. Firmness as a quality parameter is temperature dependent. This study revealed a delay in firmness reduction in moringa oil-coated banana fruit stored at 15 °C which agreed with the outcomes of [40] who reported that the firmness of bananas decreased less during low-temperature storage. Another study found that the application of composite edible coatings (moringa leaf extract (MLE) combined with carboxymethyl cellulose (CMC)) reduced the reduction in firmness of “Hass” avocado fruit during 35 days of storage [41]. This effect may be due to the reduced activity of enzymes like pectin methylesterase, which play a key role in fruit softening [42]. The coating likely acted as a gas barrier, lowering oxygen and increasing carbon dioxide levels, thereby slowing ripening and helping maintain fruit firmness [42].

3.1.3. Color

The color values of L* (lightness), a* (greenness), b* (yellowness), chroma, and hue for coated (moringa oil and olive oil) and non-coated bananas cultivars (Cavendish and Milk) under 15 °C and 25 °C are shown in Figure 3, Figure 4, Figure 5, Figure 6 and Figure 7. All color parameters were significantly (p < 0.05) affected by all factors (coating, cultivar, storage temperature, and storage days) (Table 1). Bananas coated with edible oil showed a reduction in L* and Hue values and increment in a* (Figure 4), b* (Figure 5), and chroma values. On the last day of the experiment, there was no significant change in L* and Hue values between coated bananas with moringa oil and olive oil (Figure 3A and Figure 7A). The non-coated bananas showed a rapid decline in L* value after day 6. Also, bananas coated with olive oil had higher values of a* value, b* value, and Chroma.

The coated banana shows a lower L* value than the control at both temperatures. The lowest L* value was (47.53) in coated Cavendish banana at 25 °C, while the highest L* value was (69.51) in non-coated Milk banana at 15 °C. The values for L*, b*, and Chroma were significantly higher at 15 °C in contrast to the values for a* and Hue where they were lower at the same temperature [1]. The L* increased at first and then decreased during storage, due to the banana’s color change from dark (green) to light (yellow) and then to dark (brown spots) on the last day of storage (Figure 8). L* value was higher in Milk banana than in Cavendish (Figure 3B). In all experiment cases, the a* value increased (from −values to +values) because of a decline in fruit greenness (Figure 4), also b* had a slight upward over the first eight days and then declined because the fruit color changed from green to yellow (Figure 5).

There was no significant change in b* value, chroma, and hue between coated bananas with moringa oil and olive oil at different temperature storage (Table 1). Also, the cultivars had significant changes in L* value, a* value, chroma, and hue and had no significant difference in b* value at the end of the experiment on day 12 (Figure 3B, Figure 4B, Figure 5B, Figure 6B and Figure 7B). The a* value decreased as temperature decreased in both cultivars. In the Cavendish cultivar, L*, b*, chroma, and hue values increased when the temperature decreased. The study revealed that storage at 15 °C delayed the changes in all color parameters. Overall, coating bananas with edible coating (oil and moringa) and storing them at a lower temperature (15 °C) resulted in significantly lower changes in L* value, higher a* value, higher b* value, higher chroma, and lower hue (Figure 3A, Figure 4A, Figure 5A, Figure 6A and Figure 7A).

Banana color parameters were significantly better when coated with edible oils and stored under 15 °C compared to non-coated bananas under 25 °C (Table 1), across both tested banana cultivars, Cavendish and Milk. The change in color from green to yellow in banana peel is one of the physical parameters of ripening and may be due to the decomposition of chlorophyll during ripening (Figure 8) [6]. Oil-coated bananas had positive results in slowing the discoloration of the peel compared to untreated fruits. Similar results were observed in other studies regarding banana and other fruit color changes when coated with natural edible [22,25,41]. In the study by [22], they found significant differences among the edible oil coating as well as storage life in terms of the fruit color of a banana. Also, ref. [41] indicated that edible coating potentially delays the transition of chloroplasts into chromoplasts that contain yellow and red pigments, thereby inhibiting color change and enzymatic browning of “Hass” avocado fruit. The results of [25] revealed that moringa oil combined with beeswax edible coating had a significant impact on color values, with distinct patterns in lightness, redness–greenness, and yellowness values of cucumber at various temperatures and days. The formation of the brown portion in banana peel especially in non-coated fruit in the last days of storage is properly due to the loss of cell compartmentalization that makes phenolic oxidation take place by enzymes including peroxidase and polyphenol oxidase [43].

3.2. Chemical Properties

3.2.1. pH Values

The pH of the fruit was significantly affected (p < 0.05) by the application of the coating, storage temperature, storage duration, and cultivar as shown in

Table 2. Chemical properties values and significance levels for two banana cultivars stored under two temperatures and treated with different edible oils. Means with different uppercase letters indicate a significant difference at p < 0.05.

Chemical Parameters	pH	TSS (°Brix)	TA (%)	TSS: TA (%)
Coating
C	4.96 B	12.29 A	0.17 A	74.85 A
Mo	5.26 A	10.38 B	0.15 B	72.01 B
Oo	5.28 A	10.20 B	0.15 B	71.13 B
p-value	<0.001	<0.001	<0.001	<0.001
Cultivar
Cav	5.11 B	11.68 A	0.16 A	78.63 A
Milk	5.22 A	10.24 B	0.15 B	66.70 B
p-value	<0.001	<0.001	=0.040	<0.001
Storage Temp.
15 °C	5.13 B	10.21 B	0.16 A	66.52 B
25 °C	5.20 A	11.70 A	0.16 A	78.80 A
p-value	<0.001	<0.001	=0.880	<0.001
Interactions
Tem*Cult	<0.001	<0.001	<0.001	<0.001
Tem*Coat	<0.001	<0.001	=0.010	=0.240
Cult*Coat	<0.001	=0.010	<0.001	<0.001
Tem*Cult*Coat	<0.001	<0.001	<0.001	<0.001

Cav = Cavendish banana, Milk = Milk banana, C = control (non-coated), Mo = moringa oil, Oo = olive oil, Tem = temperature, Cult = cultivar, Coat = coating.

and Figure 9. There were significant changes in pH values between coated (moringa and olive oils) and non-coated bananas stored at 15 °C and 25 °C for 12 days (Table 2). The pH in the non-coated (control) bananas was lower than the coated bananas (Figure 9A). However, there were no significant differences between bananas coated with moringa and olive oil (Table 2), where the change in pH in both coated bananas was not highly varied. Milk bananas had a higher pH than Cavendish. There were no significant changes recorded on day six in pH in both cultivars at both storage conditions (Figure 9B,C). The pH of bananas was significantly higher at 25 °C compared to 15 °C after day 6 of storage. The application of moringa oil edible coating recorded a reduction in pH during the experimental period on the Cavendish banana. The Milk banana had a significant increase in pH by 13.1% compared to the control when coated with moringa oil. Overall, the pH value was higher when using edible coating at 25 °C in both cultivars but at 15 °C the coated Milk banana had more pH value than the control. The coated Cavendish banana had a lower pH value than the control.

In general, the pH of the banana pulp is higher when the banana fruits are harvested in the green ripening stage, but it decreases as the banana ripens [44,45]. The high pH in the initial unripe stage that decreased during the ripening process is perhaps due to the accumulation of organic acid content in the fruits [46,47]. Statically, coated banana samples had significantly greater pH than non-coated samples, which agreed with another study by Malmiri, Osman [44].

3.2.2. Total Soluble Solids (TSS) Content

The statistical data regarding the TSS of bananas is shown in Table 2. The results show that there were significant effects (p < 0.05) of coating and storage temperatures on TSS among the tested banana cultivars during storage. In terms of coating, the non-coated bananas showed a higher increment in TSS values as they increased gradually during storage. However, a slow increase in TSS of both moringa oil and olive oil-coated bananas was recorded in this study (Figure 10A). Regarding cultivar, the Cavendish bananas showed a high concentration of TSS till day 8 of the storage and then started to reduce to day 10 and increased on day 12. From day 2 to day 8, Milk banana had significantly lower TSS compared to Cavendish than in the last 4 days of the experiment Milk banana had higher TSS than Cavendish (Figure 10B). The TSS content of bananas stored at 25 °C was significantly higher than that of those stored at 15 °C (Figure 10C). There were significant differences between control and coated bananas in TSS at both 25 °C and 15 °C (Table 2). Statistical analysis showed significant changes in the TSS of bananas when coated with moringa oil as the temperature changed. In contrast, there were no significant changes in the TSS of bananas when treated with olive oil as the temperature changed. However, there was an increment of 18.40% and 20.49% in TSS when coated with moringa oil and olive oil, respectively, in comparison to the control, which was higher (Table 2). There were no significant differences in TSS of the Cavendish banana at 15 °C and the Milk banana at 25 °C. TSS of the Cavendish banana was higher than in the Milk banana by 12.32% (Table 2). Generally, the difference in the types of oil coating used in this experiment did not cause any difference in its effect on TSS.

Oil-coated fruits can slow down the metabolic function related to ripening and aging during the postharvest period to extend the shelf life of fresh fruit. In our experiment, control banana samples had higher TSS compared to treated banana samples, indicating that oils slow down changes in the TSS. Accordingly, as mentioned earlier, coating fruit with oils slows respiration, leading to delayed synthesis, which leads to a decrease in the content of TSS [48,49]. This result is in agreement with those of Joshi and Rao [49,50] who concluded that the fruit treated with edible layers significantly reduced the TSS.

3.2.3. Titratable Acidity (TA)

The results in Table 2 indicated that the changes in TA% were affected (p < 0.05) by coating and cultivar, but not by storage temperature. Among all three study factors of variability, TA means of banana fruits ranged between 0.15% and 0.17% for 12 days of storage. There were significant changes in TA between fruits coated (moringa and olive oils) and non-coated bananas. On the other hand, there were no significant differences in TA between bananas coated with moringa oil and olive oil (Figure 11A). From day 2 to day 6, Milk banana had significantly lower TA than Cavendish; however, it started to increase from day 8. The TA in Cavendish was higher compared to the Milk banana till day 6 and it showed a continuous decline during the 12 days of storage (Figure 11B). TA did not significantly differ between bananas stored at 25 °C and 15 °C (Figure 11C). The results showed a significant change in TA between control and coated bananas when stored under the storage temperatures of 25 °C and 15 °C (Table 2). In contrast, there was no significant change in the TA of bananas when treated with moringa oil and olive oil as the temperature changed.

The decrease in acidity in the fruit during ripening is accompanied by the decrease in organic acids. El-Anany, Hassan [51] stated that this decrease is due to an increase in metabolic activities such as ethylene production and a higher respiratory rate. Also, ref. [22] stated that since organic acids such as malic or citric acid are primary substances for respiration, a reduction in acidity and hence an increasing pH are expected in highly respiring fruits. Our findings are in agreement with Saleem, Ejaz [52] and Alali, Awad [53] who found that coated persimmon and banana, respectively, retained a higher TA level compared to the uncoated ones. The study of [22] confirmed that coating may reduce respiration rates and may, therefore delay the utilization of organic acids in bananas.

3.2.4. TSS: TA Ratio

The ratio of TSS to TA is one of the main characteristics that determine the taste of fresh fruit. The TSS: TA ratio was affected (p < 0.05) by all studied factors (Table 2). At all tested conditions, the TSS: TA ratio was increasing over time (Figure 12). The changes in TA% varied between the coated and the non-coated bananas (Figure 12A); however, there was no variation between the olive and moringa oils coating. In terms of coating, no significant effects were noticed on the TSS: TA ratio between the Cavendish and Milk bananas during the complete storage time, excluding days 10 and 12 (Figure 12B). Also, the TA% differed significantly (p < 0.05) between the two studied storage conditions.

The non-coated bananas increased rapidly during the experimental period and they showed the highest values of TSS: TA ratio compared to the coated fruit. There was an increase of 3.94% and 5.23% in TSS: TA when coated with moringa oil and olive oil, respectively. Figure 12B shows a significant change in TSS: TA ratio in both banana cultivars (Cavendish and Milk Banana) on the 8th day of storage. Moreover, Milk bananas had a significantly lower TSS: TA ratio compared to (Figure 12B).

The effect of 25 °C in banana TSS: TA ratio was significantly higher than 15 °C (Figure 12C). The experiments showed a significant difference (p < 0.05) in TSS: TA of the banana cultivars (Cavendish and Milk) at 25 °C and 15 °C (Table 2). Taken together, more TSS: TA ratio indicates more flavor during fruit ripening [1]. In this experiment, control banana samples had more TSS: TA than coated banana samples, indicating that coating fruit with oils slows down chemical changes in fruit tissue which results in delayed decomposition and lower TSS: TA ratio [49,50].

3.3. Banana Mineral Content

Table 3. Mineral content values and significance levels for two banana cultivars (Milk, Cavendish) stored under two temperatures (15 °C, 25 °C) and treated with different edible oils (moringa oil, olive oil) after 12 days of storage.

Temperature	Treatment	K (mg/g)	Na (mg/g)	Ca (mg/g)
25 °C	control	66.77 aA	7.99 aA	3.46 aA
	Moringa oil	68.38 aA	7.85 aA	3.41 aA
	olive oil	81.21 aA	8.79 aA	3.61 aA
15 °C	control	75.22 aA	8.14 aA	3.62 aA
	Moringa oil	69.07 aA	7.54 aA	3.73 aA
	olive oil	69.08 aA	7.48 aA	3.46 aA
Average of	control	70.99 a ± 4.89	8.06 a ± 0.73	3.54 a ± 0.43
	Moringa oil	68.73 a ± 4.16	7.70 a ± 0.67	3.57 a ± 0.43
	olive oil	75.14 a ± 6.4	8.14 a ± 0.78	3.54 a ± 0.41
Treatments	Cultivars
control	Cavendish	71.25 aA	8.89 aA	3.84 aA
	Milk	70.74 aA	7.24 bC	3.24 aA
Moringa oil	Cavendish	70.18 aA	8.47 aAB	3.71 aA
	Milk	67.27 aA	6.92 bC	3.43 aA
olive oil	Cavendish	70.42 aA	8.81 aAB	3.81 aA
	Milk	79.86 aA	7.46 aBC	3.27 aA
Average of	Cav	70.62 a ± 3.40	8.72 a ± 0.58	3.79 a ± 0.37
	Milk	72.62 a ± 4.9	7.21 b ± 0.58	3.31 a ± 0.30
Cultivars	Temperature
Cavendish	25 °C	68.31 aA	9.3 aA	3.7 aA
	15 °C	72.92 aA	8.15 bB	3.87 aA
Milk	25 °C	75.92 aA	7.12 aB	3.30 aA
	15 °C	69.32 aA	7.29 aB	3.33 aA
Average of	25 °C	72.12 a ± 4.68	8.21 a ± 0.59	34.98 a ± 0.33
	15 °C	71.12 a ± 3.82	7.72 a ± 0.59	3.60 a ± 0.35

Means in the same column with the different uppercase letters indicating a significant difference between interactions. Different lowercase letters within the column indicate a significant difference in the relationship within the variable at p ≤ 0.05 (means ± SE).

shows the findings of mineral content (potassium (K), calcium (Ca), and sodium (Na)), of coated (olive oil and moringa oil) and non-coated ‘Milk’ and ‘Cavendish’ banana fruit stored at 15 and 25 °C after 12 days of storage. The highest concentrations of mineral content were detected in bananas stored at 25 °C in the range of 66.38–81.21 mg/g (K), 7.85–8.79 mg/g (ca), and 3.41–3.61 mg/g (Na), while comparatively lower values were noted at 15 °C, generally ranging between 69.07 and 75.22 mg/g, 7.48 to 8.14 mg/g, and 3.46 to 3.62 mg/g for K, ca, and Na, respectively. Regarding the effect of coating, all minerals were most abundant in olive oil-coated bananas stored at 25 °C. At 15 °C, non-coated (control) bananas showed the highest levels of potassium (K) and sodium (Na), whereas moringa oil-coated bananas exhibited the highest calcium (ca) content after 12 days of storage. In terms of cultivar performance, both coated and non-coated Cavendish bananas retained higher mineral levels compared to Milk bananas, indicating better mineral preservation across treatments.

Table 4. The concentration of minerals compassion on the peel and pulp of banana fruit.

	K (mg/g)	Na (mg/g)	Ca (mg/g)
Peel	84.38 a ± 3.52	11.02 a ± 0.24	5.22 a ± 0.24
Pulp	58.85 b ± 3.83	4.91 b ± 0.33	1.88 b ± 0.11

Means of different lowercase letters within the column indicate a significant difference in mineral composition between the peel and pulp of banana fruit at p ≤ 0.05 (means ± SE).

indicated that the banana peel indicated a significant increase of 30.25% in K, 55.44% in Na, and 63.98% in Ca, compared to the banana pulp.

These findings aligned with the results obtained by [35] who recorded that edible coating (2% Sodium alginate and 0.2% Olive oil with a combination of 1% ascorbic acid and 1% citric acid) has the potential to improve its valuable nutritional characteristics. It has been stated by [54] that coating acts as a protective layer and regulates the permeability of O₂ and CO₂, resulting in a reduction in the autooxidation potential of fresh fruit. Based on the study, it is also important to note that the Milk banana fruit has a thinner peel compared to the Cavendish bananas, which may probably contributed to the lower mineral content mineral contents during storage, as the thinner peel offers less protection against moisture reduction and nutrient degradation compared to the other cultivar with thicker peels.

In addition, the nutritional value and the chemical composition of the banana can be affected by various factors, for example, cultivar, soil composition, growing area, agricultural practices (fertilizers, methods of cultivation, quality of water, pesticides), and storage [55,56]. Our results for coating bananas with oils and stored under different temperatures showed no effect on the concentration of minerals for banana fruit. The peel had more content of minerals than the pulp. This confirmed that the peel is being recognized for its nutritional value and potential applications in food, feed, and bio-based products [57,58,59].

4. Conclusions

Two banana cultivars were coated with two oils: olive and moringa (Moringa peregrina) oil and then stored at two different temperatures (15 and 25 °C) for 12 days. The results showed that the investigated natural oils can act as an important factor in controlling and delaying the postharvest quality of the banana and ripening process. The non-coated (control) banana fruit had lower firmness, higher weight loss percentage, and faster color change than the moringa and olive oil-coated banana fruit. Coated banana samples had significantly greater pH than non-coated samples. Coating the fruit with moringa and olive oils did not vary significantly on the TSS, TA, and TSS: in TA content, however, both oils showed the potential to sustain and slow down the alternations of the chemical attributes of both Milk and Cavendish banana cultivars. Storage at higher temperatures (25 °C) increased the changes in both chemical and physical attributes of both cultivars during the 12 days of storage. The mineral contents (K, Na, Ca) were most abundant in olive oil-coated bananas stored at 25 °C. Minerals were highly retained in coated Cavendish bananas. Moringa oil and olive oil coatings have shown great potential in preserving the quality of bananas and can be effectively applied to other fresh produce to reduce postharvest losses across the supply chain. When combined with proper temperature management, these coatings help maintain the fruit’s overall quality, thereby extending shelf life and enhancing marketability.