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Article

Effect of Whey Protein Edible Coating Incorporated with Mango Peel Extract on Postharvest Quality, Bioactive Compounds and Shelf Life of Broccoli

by
Nesren Elsayed
1,
Ashwak Abdel-moneim Hassan
2,
Suzy M. Abdelaziz
3,
Emad A. Abdeldaym
4,* and
Omaima S. Darwish
4
1
Food Science Department, Faculty of Agriculture, Cairo University, Giza 12613, Egypt
2
Dairy Science Department, Faculty of Agriculture, Cairo University, Giza 12613, Egypt
3
Cross Pollinated Vegetable Research Department, Horticulture Research Institute, Giza 12611, Egypt
4
Department of Vegetable Crops, Faculty of Agriculture, Cairo University, Giza 12613, Egypt
*
Author to whom correspondence should be addressed.
Horticulturae 2022, 8(9), 770; https://doi.org/10.3390/horticulturae8090770
Submission received: 31 July 2022 / Revised: 16 August 2022 / Accepted: 24 August 2022 / Published: 26 August 2022
(This article belongs to the Special Issue Postharvest Handling of Fruits and Vegetables)
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Abstract

:
The present study evaluated the impact of edible coatings based on whey protein concentrate (WPC) and mango peel extract (MPE) on the shelf life, physicochemical, and microbial properties of minimally processed broccoli preserved at 5 ± 1 °C for 28 days. The variations in the physicochemical and microbial properties of the broccoli fresh-cuts were evaluated by determining the following parameter changes: weight loss, color, respiration rate, ascorbic acid content (AsA), sulforaphane content (SF), total phenolic content (TPC), antioxidant activity (AOA), total bacteria, fungi counts, and sensory evaluation. Broccoli fresh-cuts were treated with WPC alone or in combination with MPE (WPC/MPE) at 1% or 3%, and uncoated broccoli fresh-cuts were a control. The obtained results revealed that all the coated broccoli fresh-cuts showed lower weight loss than the uncoated broccoli fresh-cuts. The coating with WPC/MPE at 3% recorded the lowest weight loss among all treatments; however, it wasn’t significantly lower compared to WPC/MPE at 1%. The addition of MPE to WPC in coating solution at 1% and 3% resulted in a higher value of the (-a*), indicating better green color retention and decreased floret yellowing. All applied coatings significantly conserved the bioactive compounds (AsA, SF, and TPC) and AOA of broccoli fresh-cuts compared to uncoated ones. At the end of the storage period, the maximum values of the aforementioned bioactive compounds were recorded in the broccoli fresh-cuts coated with WPC/MPE at 3% followed by WPC/MPE at 1%, and WPC alone compared to uncoated broccoli fresh-cuts. The broccoli fresh-cuts coated with WPC/MPE at 3% recorded a higher score on sensory evaluation than those coated with WPC/MPE at 1%, followed by broccoli fresh-cuts coated with WPC alone. The WPC-based edible coating combined with MPE (WPC/MPE) at 3% showed the highest reduction in the total fungi and bacterial counts compared to all the other treatments.

1. Introduction

Broccoli (Brassica oleracea var. Italica), a member of the cabbage family (Brassicaceae), is an important vegetable crop. Broccoli is rich in health-promoting compounds, i.e., flavonoids, glucosinolates, and vitamins C, E, and A, mainly referring to their antioxidant and free-radical scavenging stimulants [1]. In recent years, the demand for fresh or ready-to-eat broccoli salad has increased. The attention being paid to consuming vegetables, especially fresh broccoli, is due to the health benefits of their compounds [2]. The main problems that affect the postharvest quality of broccoli florets are surface dehydration and yellowing, accompanied by chlorophyll breakdown and tissue hardening [3]. Additionally, broccoli is considered a highly perishable product, and cutting operations increase tissue destruction, which causes the release of intracellular contents with losses in bioactive compounds while increasing the activity of pathogenic microorganisms. These factors reduce the shelf life of the florets and result in a low-quality product [4]. These facts explain the need to develop new technologies that reduce broccoli deterioration during cold storage.
Therefore, in recent years, the application of edible coatings, either in whole fruits or fresh-cuts, has been given attention as a novel approach for increasing the shelf life of fruits and vegetables i.e., strawberries [5,6], mango [7], apple fresh-cuts [8,9], artichoke bottoms [10], and broccoli [11]. Edible coatings, which may be consumed together with food or without further removal, are materials used for wrapping foods to prolong the product’s shelf life. Edible coatings offer several advantages compared to synthetic materials, such as environmental friendliness and biodegradability [12]. Some edible coatings have the potential to enhance food appearance, nutritional quality, and delay or inhibit the growth of pathogenic and spoilage microorganisms by several mechanisms, acting as a barrier against water vapor and gas transport, thereby combatting the effects of storage under a controlled atmosphere [13,14].
Several polymers have been used to formulate edible coatings or films, including polysaccharides, proteins, and lipids [15]. Proteins are of great interest in edible coating technology because of their abundance as food processing by-products. Milk proteins, such as casein and whey proteins (WP), have several important physical qualities (e.g., water solubility and emulsifying ability) that make them suitable for edible films [16,17]. The abundance of WP piques the curiosity of the packaging industry and supports their use as films/coatings on food surfaces to protect goods from chemical or microbial degradation, thereby extending shelf life and maintaining excellent product quality. WP films are garnering increased attention for their mechanical and barrier qualities, as they outperform polysaccharides and other protein-source-based films [18].
Nowadays, the trend is to use unconventional and renewable material sources such as by-products from fruit and vegetables [19,20,21,22]. By-products of the mango processing industry, such as peels and kernels, are an example of by-products that can be used to formulate biodegradable packaging. Peel is a by-product of fruit processing and presents about 15–20% of the whole fruit weight [23]. Mango peels are also rich in valuable components such as phenolic compounds, minerals, and fibers [24]. Mango peels contain bioactive compounds such as xanthones, flavonoids, gallic acid, gallates, benzophenones, and their derivatives [25], which contribute to the antioxidant ability of the mango peels. It is worth mentioning that few investigations have been conducted to study the effectiveness of WPC coating with or without mango peel extract (MPE) on the vegetables’ quality and shelf life during storage. Therefore, this study aimed to develop bio-films by incorporating two concentrations of MPE into the WPC coating solution and evaluating their effect on the postharvest quality content of bioactive compounds (antioxidant, total phenolic, sulforaphane, and ascorbic acid), and by performing a microbiological evaluation of broccoli fresh-cuts.

2. Materials and Methods

2.1. Chemical and Plant Materials

Whey protein concentrate (WPC) (WP, 80%), glycerol (99.5%), 1,1-diphenyl-2-picrylhydrazyl (DPPH), meta-phosphoric acid, L-ascorbic acid (U.S.P. grade, ≥99.0%), solvents, folin-Ciocalteu reagents, and sulforaphane (95%) were purchased from CP Kelco (Atlanta, GA, USA) and Sigma-Aldrich (St. Louis, MO, USA). On the other hand, broccoli heads (Brassica oleracea L. var. Italica) cv. Naxos F1 hybrid were taken from the experimental and research station, Faculty of Agriculture, Cairo University, Giza, Egypt. Healthy heads (free from damage and defects) were harvested using a sharp knife and immediately transported to the postharvest laboratory at the Department of Vegetable Crops, Faculty of Agriculture, within 60 min of harvesting.

2.2. Preparation of Mango Peels Extract

Mango peels (Mangifera indica cv. Ewiss) were gathered from markets in Egypt. The peels were washed with tap water to remove the dust and other unacceptable substances. Then, they were dried at 50 °C, milled, and sieved at 50 mesh. About 200 g of mango peel powder was extracted by ethanol 80% at a ratio of 1:20 (w/v) using a homogenizer for 30 min. The extract was passed through a filter paper (Whatman No. 1). A rotary evaporator was used to concentrate the filtrate at 40 °C, and the concentrate was lyophilized and stored at 5 °C before coating application.

2.3. Preparation of WPC–Mango Peel Extract Coatings

The WPC-MPE coating solution was prepared according to the method described by Hammad et al. [9]. WPC 10% (w/v) was dissolved in distilled water at 45 °C for 30 min with continuous stirring, then 3% (w/w) glycerol was added and heated at 45 °C for 15 min. MPE concentrations (1 and 3%) were added to the previous solution, with continuous mixing for another 60 min. The broccoli florets were split into 4 groups. The first group was immersed in distilled water and served as a control. The second group was immersed in an aqueous solution of 10% (w/w) WPC and 3% (w/w) glycerol. The third and fourth groups were coated with the same solution incorporated with 1, or 3 % of MPE, respectively. After 3 min of immersion, the treated broccoli fresh-cut was dried for 10 min in a laminar air flow hood. The samples were then placed in non-perforated polypropylene bags that were thermally sealed (each containing about 250 g of florets) and stored at 5 °C and 80% RH for 28 days. The bags for each treatment were divided into two groups. The first group was continuously stored through the storage period to record the weight loss. The second group was used to determine the rest of the parameters. All the selected parameters were measured at the following intervals: 0, 7, 14, 21, and 28 days post-application of the different coatings (treatments). The experiment was repeated twice, with six replicates for each treatment, and the averages were used.

2.4. Phenolic Compounds Profile of Mango Peel Extract

The phenolic compounds of MPE were determined using an Agilent 1260 series HPLC system. The separation was carried out using a Zorbax Eclipse plus C18 column (100 mm × 4.6 mm, particle size 5 µm; Agilent Technologies Co. Ltd., Denver, CO, USA). The mobile phase involved (A) water 0.2% H3PO4, (B) methanol, and (C) acetonitrile at a flow rate of 0.6 mL/min. The detection wavelength was monitored at 284 nm. The injection volume was 20 μL of gallic acid and the column temperature was kept at 30 °C.

2.5. Antimicrobial Activity of Whey Protein and Mango Peel Extract Coating Solutions

The antimicrobial activity of WPC and MPE without mixing was assessed using the disk diffusion method against different kinds of harmful microorganisms (Salmonella typhimurium ATCC 14028, Staphylococcus aureus MRSA, Listeria mono-cytogenes, Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 33018, Aspergillus niger NRRL 2035, and Aspergillus flavus NRRL 3357). The Petri plate’s surface of Mueller Hinton agar (MH) was inoculated by spreading 100 μL (108 CFU/mL) of microbial suspension and a 6-mm diameter well was punched aseptically onto the MH agar. 100 μL of WPC and WPC–Mango peel extract coating solutions were seeded into the well and the plate was incubated at 37 °C for 24–48 h. The inhibition zone diameter around the wells was calculated in millimetres (mm) whereby, zone of inhibition (ZOI) = diameter of growth inhibited zone−diameter of the well. The absence of a zone of inhibition was considered to represent that there was no activity [26].

2.6. Physicochemical and Microbial Properties of Broccoli Fresh-Cut

2.6.1. Weight Loss

Weight loss of treated broccoli fresh-cuts was determined in triplicates after 7, 14, 21, and 28 d of storage using this equation [27].
Weight loss (%) = (initial weight − final weight) × 100
           (initial weight)

2.6.2. Color Measurement

The surface color of broccoli fresh-cuts were determined by a chromameter Minolta CR-400 (Minolta. Inc., Tokyo, Japan) using the CIE color parameters a* (greening), b* (yellowing), chroma (C*), and hue angle (h◦). The color was measured on 5 florets per replicate after 0, 7, 14, 21, and 28 d of storage. A standard white paper was used to celebrate the Chromameter [28].

2.6.3. Respiration Rate

Respiration rate was defined as a concentration of carbon dioxide and oxygen inside the gas jar holding the broccoli samples. The respiratory rate of broccoli fresh-cuts was determined using the oxygen and carbon dioxide analyzer (Model 902P, Quantek Instruments, Grafton, MA, USA) connected with oxygen/carbon dioxide sensor PS-2110. This measurement was performed in a glass jar holding two fresh cuts of broccoli. After 120 min, the respiratory rate was determined on days 0, 7, 14, 21, and 28 for each treatment, using four replicates per treatment [29].

2.6.4. Ascorbic Acid Content

Ascorbic acid (AsA) content was determined using the titrimetric method with 2, 6-dichlorophenol indophenol, as mentioned in AOAC [30]. The amount of AsA was expressed as mg/100 g of broccoli fresh weight.

2.6.5. Sulforaphane Content

Approximately 0.5 g of broccoli sample was homogenised with 5 mL of distilled water before being hydrolyzed in a water bath at 37 °C for 3 h. After hydrolyzing, 20 mL of dichloromethane was added to extract the sulforaphane in the mixture. A rotary evaporator was used to remove dichloromethane at 37 °C. Dry samples were re-dissolved in acetonitrile (chromatographic grade, 2 mL) and filtered through a 0.45 μm membrane filter for determination. Then, the sulforaphane content was determined by the Agilent 1260 series HPLC system (Agilent Technologies Inc., Santa Clara, CA, USA). The separation was carried out using a C18 column (5 µm, 250 × 4.6 mm particle size). The solvent system consisted of 20% acetonitrile in water, was then changed linearly over 10 min to 60% acetonitrile, and then was maintained at 100% acetonitrile for 2 min to purge the column. The column oven temperature was set at 30 °C. The flow rate was 1 mL/min. The detection wavelength was set at 254 nm, the injection volume was 20 μL and the column temperature was maintained at 30 °C. The sulforaphane quantity in samples was based on the standard curve of sulforaphane and the content was represented as µg/g FW [31].

2.6.6. Total Phenolic Content

The extract of the treated broccoli fresh-cuts was obtained through the procedure reported by Dávila-Aviña et al. [32] with minor modifications. Briefly, 30 g of broccoli sample was homogenized with 10 mL of ethanol 80%, using a homogenizer (IKA Works, Wilmington, NC, USA). Then homogenate was centrifuged at 14,000 rpm for 15 min. The supernatant was collected and the precipitate was extracted again with 5 mL of ethanol 80%, under the previous conditions. The obtained supernatants were filtered using filter paper (Whatman No. 1). The filtrate was stored at −10 °C until using it in the determination of the total phenolic content and antioxidant activity.
Total phenols of broccoli extract and coating solutions were determined spectrophotometrically using folin–Ciocalteu reagent with gallic acid as a standard. The finding of mango peel was defined as mg gallic acid equivalent/g dry matter while it was expressed as mg gallic acid/100 g for fresh cuts of broccoli.

2.6.7. Antioxidant Activity

The antioxidant activity of coated broccoli fresh-cuts and coating solutions was determined using an examination of the free-radical scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH, from Sigma Company, St. Louis, MO, USA), as stated by Elsayed et al. [33]. For this analysis, the previous extract was mixed with methanol DPPH solution. The acquired mixture was shaken vigorously and kept in darkness for 30 min. The absorbance was measured at 510 nm with a spectrophotometer (model UV-2401 PC, Shimadzu, Milano, Italy) against a blank. The antioxidant capacity was expressed as percentage inhibition of the DPPH radical (%).

2.6.8. Microbiological Analysis

Microbiological analysis, including total bacterial count (TBC), psychrotrophic, yeast, and mold counts on broccoli fresh-cuts exposed to the various treatments was estimated at days 0, 7, 14, 21, and 28. Briefly, 10 g of broccoli from each treatment was transferred into sterile flasks. Samples were homogenized with 90 mL of sterilized saline solution using an electric blender (IUL Instruments, Barcelona, Spain) for 1 min. Serial dilutions were performed for each treatment. After that, one millimetre of diluted sample was transferred into Petri dishes containing nutrient agar for total count bacteria and potato dextrose agar (PDA) for mold and yeast. Then, Petri dishes were incubated at 32 °C for 2 days to evaluate mesophilic, 7 days at 5 °C for psychrophilic, and 4 days at 28 °C for yeast and mold counts [34]. Colonies were counted and the findings were stated as log CFU g-1 of broccoli.

2.6.9. Sensory Evaluation

Sensory evaluation of coated and uncoated broccoli fresh-cuts was estimated by adjudicators who regularly consume broccoli. Twenty panelists from the staff of the food science and vegetable crops departments at the Faculty of Agriculture, Cairo University, Egypt, were recruited. The sensorial traits such as odor, taste, texture, and overall acceptability were estimated using a 10-point hedonic scale to award a score from 10 (like extremely) to 1 (dislike extremely).

2.7. Statistical Analysis

The results were expressed as mean ± standard deviation. All data were analyzed in 6 replications for each parameter. Data were analyzed statistically utilizing analysis of variance (ANOVA) by MSTAT-C software (Michigan State University, East Lansing, MI, USA). Differences between means were considered significant at a 95% (p < 0.05) confidence level according to Duncan’s multiple range test.

3. Results

3.1. Chemical and Antimicrobial Properties of Used Coating Solutions

3.1.1. Total Phenolic Content and Antioxidant Activity

The chemical properties of the coating solution based on WPC were significantly affected by the MPE addition (p < 0.05), as shown in Table 1. Whereas, the quantity of total phenolic content (TPC) and the antioxidant activity (AOA) of the coating solutions increased after the incorporation of MPE. The concentration of TPC in the coating solutions increased by 84.21% and 90.48% after the addition of MPE extract at ratios of 1% and 3%, respectively. A similar trend was observed in the percentage of AOA. The ratio of AOA significantly increased (p < 0.05) when the MPE concentration increased from 1% to 3% (Table 1).
A tentative characterization of the optimal MPE was performed using HPLC to determine which compounds could be responsible for its outstanding antioxidant and anti-microbial activity. The data in Table 2 illustrates 18 identified components. Furthermore, phenolic acids such as pyrogallol, gallic acid, catechol, p-hydroxybenzoic acid, chlorogenic acid, vanillic acid, syringic acid, p-coumaric acid, benzoic acid, ferulic acid, o-coumaric acid, mangiferin, resveratrol, cinnamic acid, rosmarinic acid, and flavonoid derivatives such as catechin and quercetin were identified. The MPE contained high amounts of resveratrol (1278 µg/g), quercetin (318.58 µg/g), rosmarinic acid (259.22 µg/g), mangiferin (235.96 µg/g), and pyrogallol (212.40 µg/g).

3.1.2. Antimicrobial Activity of WPC and WPC/–MPE Coating Solutions

The data in Table 3 show the antimicrobial activity of coating solutions based on WPC and MPE without mixing against the following eight pathogenic microorganisms. The pathogen strains (gram-positive, gram-negative bacteria, and yeasts) were chosen to reflect the study’s target area, including microbial inhibition of enteric pathogens, food-borne pathogens, and spoiling microbes (contaminants). The results showed that coating solutions based on WPC or MPE without mixing exhibited different influences on the aforementioned pathogenic microorganisms. Although MPE coating solution had strong antimicrobial activity on both Listeria monocytogenes and Staphylococcus aureus, WPC coating solution was not a powerful antimicrobial against Listeria monocytogenes, however, it did inhibit the growth of Staphylococcus aureus and Escherichia coli. Additionally, it was found that the WPC coating solution did not show crucial inhibition in the experiments related to Staphylococcus aureus MARSA, Bacillus cereus ATCC 33018, and Aspergillus niger NRRL 326. However, it can be concluded that both WPC and MPE coating solutions have an antimicrobial effect on Aspergillus flavus NRRL 1957 by showing zones of inhibition of 29 and 20 mm, respectively.

3.2. Effect of Coatings on Physicochemical and Microbial Properties of Broccoli Fresh-Cut

3.2.1. Weight Loss

Weight loss of either uncoated or coated broccoli fresh-cuts was increased with increasing storage periods (Figure 1). The increment was the highest on the uncoated broccoli compared to all coated broccoli at all storage periods. This increase reached 30.55% after 28 days of storage, while the broccoli treated with WPC/MPE 3% or 1% recorded 13.44% and 18.44%, respectively. All treatments with coatings obtained weight loss at all storage periods lower than the uncoated samples. The coating with WPC/MPE 3% recorded the significantly lowest weight loss among all treatments at all storage periods, except after 21 days. However, it was not significant compared with WPC/MPE 1%. The broccoli coated with WPC/MPE 1% ranked with the second lowest weight loss across all storage periods, and then broccoli coated with WPC alone.

3.2.2. Color Measurement

The external color was assessed by recording greenness (-a*), yellowness (b*), chroma (C*), and hue angle (h◦). The greenness (-a*) values gradually decreased as the storage periods were extended (Figure 2A). At zero and seven days, the applications with WPC/MPE 1% or 3% conserved a* values of broccoli compared to the uncoated ones. The same effect was observed after 14 days of cold storage, although the coatings with WPC recorded a* insignificant value compared to the uncoated ones. After 21 and 28 days, all coatings obtained a* values higher than the uncoated samples. In addition, WPC/MPE 1% or 3% recorded significantly higher values of a* compared with WPC.
The yellowness values (b*) of all treated florets and the control were increased by increasing the storage days (Figure 2B). No significant differences were recorded among all treatments at zero time. After 7 days of cold storage, WPC/MPE 3% recorded the significantly lowest b* compared to uncoated and WPC, though no differences were recorded between WPC/MPE 1% and WPC/MPE 3%. After 14 or 21 days of storage, the uncoated broccoli showed the highest values of b* compared to WPC/MPE 1% and 3%. After 28 days of storage, the differences were more obvious: the b* values of all coating applications declined compared to the control samples. WPC/MPE 3% obtained the lowest value of b*, and then WPC/MPE 1% placed second. Chroma values (C*) were increased with an increasing storage period (Figure 2C). No significant differences were obtained among all treatments at zero or after 7 days of storage. While after 14 days of storage, the treated broccoli with WPC/MPE 3% recorded the lowest C* value compared to the WPC and uncoated treatment. Additionally, after 21 days of storage, the coatings with WPC/MPE 1% or 3% obtained significantly lower C* values compared to the uncoated treatment, but without a significant difference from one another or WPC only. After 28 days of cold storage, the treatment with WPC/MPE 3% showed the lowest value of C* compared to the uncoated, and without significance compared to WPC/MPE 1%.
After 7 days of storage, WPC/MPE 3% obtained the highest value of h◦ compared to uncoated and WPC, but without significance compared to WPC/MPE 1% (Figure 2D). Conversely, after 14 days, insignificant differences were recorded among all coating applications; however, all of them were significantly higher than uncoated. In the last two storage periods, WPC/MPE 3% was significantly higher than uncoated and other treatments.

3.2.3. Respiration Rate

Fresh-cut products have a high respiration rate and are greatly influenced by temperature and storage period [35,36]. Figure 3 shows the changes in the respiration rate on days 0, 7, 14, 21, and 28. From day 14 until day 28, the coated broccoli samples gradually displayed a significant (p < 0.05) difference in respiration rate compared with the uncoated samples. The respiration rate of all coated broccoli samples with WPC, WPC + 1% MPE, and WPC + 3% MPE was significantly reduced compared to the uncoated samples. After 28 days of the storage period, a minimum respiration rate value was detected in the coated broccoli samples with WPC + 3% MPE, followed by WPC + 1% MPE and WPC compared to the uncoated samples.

3.2.4. Ascorbic Acid Content

Ascorbic acid (AsA) plays a vital role in the conservation of fruit fresh-cuts during storage [36]. Changes in the AsA of broccoli fresh-cuts during storage periods is shown in Figure 4. AsA was reduced during cold storage for both uncoated and coated broccoli fresh-cuts. At zero time, before storage, no significant differences in the AsA content were recorded between the coated and uncoated treatments. However, after 7 days of storage, the AsA content of all coating treatments was significantly higher than the uncoated treatment. Compared to the uncoated treatment, the maximum content of AsA was shown in broccoli fresh-cuts treated with WPC/3% MPE followed by WPC/1% MPE and WPC coated. This trend was observed at all storage points up to 28 days of cold storage.

3.2.5. Sulforaphane Content

The change in the sulforaphane content (SF) of stored broccoli fresh-cuts treated with WPC alone or in combination with MPE is presented in Figure 5. The sulforaphane content (SF) of all coated and uncoated samples of broccoli fresh-cuts decreased with an increase in the length of the storage periods. Furthermore, after 28 days of storage, the maximum SF content was observed in samples coated with WPC/MPE 3%, followed by WPC/MPE 1% and WPC alone, compared to uncoated ones.

3.2.6. Total Phenolic Content

The total phenolic content (TPC) was influenced by all the treatments and storage periods (Figure 6). The initial TPC varied, 80.08, 101.2, 138.2, and 158.7 mg/100 g FW for uncoated, WPC coated, WPC/MPE 1%, and WPC/MPE 3%, respectively. These differences were due to the variation in phenolic content that was involved in the composition of the coated solution. At the end of preservation period, all coatings had varying positive effects on decreased TPC degradation in coated broccoli compared to uncoated broccoli. The incorporation of coating solution with MPE at both concentrations of 1% or 3% maintained TPC as intact as possible compared with WPC coating only. Furthermore, the broccoli samples coated with WPC/MPE at 3% showed the lowest decrease in TPC, while the uncoated broccoli samples showed the highest decrease in TPC (78.6 and 18.6 mg/100 g FW) compared to other treatments.

3.2.7. Antioxidant Activity

The variation in the antioxidant ratio of broccoli samples coated with WPC alone or combined with MPE during the storage periods is revealed in Figure 7. The antioxidant activity gradually reduced as the storage periods were extended. The reduction in the antioxidant activity of uncoated broccoli samples was extremely rapid compared with WPC, WPC/MPE 1%, and WPC/MPE 3%. At the end of storage periods, the maximum activity of antioxidants was recorded in the broccoli fresh-cuts coated with WPC/MPE 3%, followed by WPC/MPE 1% and WPC alone, compared to the uncoated ones.

3.2.8. Microbiological Analysis

This study assessed the effects of WPC and WPC incorporated with MPE coating materials on total bacterial, psychrotrophic, and fungal counts. The total bacterial counts (TBC) of uncoated broccoli increased as the length of the storage period increased from 2.0983 log CFU/g at initial storage to 4.39 log CFU/g after 28 days of storage (Figure 8). The TBC of coated samples was 4.40 log CFU/g for samples coated with WPC and 4.05 log CFU/g for samples treated with WPC/MPE 1% at 28 days of storage, while the TBC of coated samples with WPC/MPE at 3% was 2.99 log CFU/g at 28 days of storage. From these results, it can be observed that the WPC/MPE 3% and WPC/MPE 1% coating materials significantly inhibited the rate of bacterial proliferation compared to the uncoated samples. At the end of the storage period, the maximum reduction in TBC was recorded in the broccoli samples coated with WPC/MPE 3% while the minimum inhibition was observed in broccoli samples coated with WPC alone.
The psychrotrophic bacterial counts in coated broccoli were determined and compared with uncoated samples during the storage period (Table 4). The results indicate that the psychrotrophic bacterial counts gradually increased as the storage period was extended. No growth of psychrotrophic bacteria was detected in broccoli samples coated with WPC/MPE 3% from day 7 until day 21 of storage. At the end of storage periods, the minimum growth of psychrotrophic bacteria was recorded in the broccoli samples coated with WPC/MPE 3% (1.84 log CFU/g), followed by the samples coated with WPC/MPE 1% (2.29 log CFU/g) and WPC (2.72 log CFU/g), compared to the uncoated samples (4.34 log CFU/g).
Regarding fungal counts, the total count of fungi in the uncoated samples increased from 2.2 log CFU/g to 3.89 log CFU/g after 28 days of storage (Table 5). At the end of the storage periods, the fungal count of the coated samples was 3.46 log CFU/g for samples coated with WPC, while it was 2.23 and 1.95 log CFU/g for samples coated with WPC/MPE 1% and WPC/MPE 3%, respectively. In this respect, the incorporation of MPE into WP is effective in reducing fungal growth during cold storage. In addition, the reduction in fungal growth increased when the ratio of MPE increased from 1% to 3%.

3.2.9. Sensory Evaluation

The sensory attributes of coated and uncoated broccoli samples, including taste, texture, odor, and overall acceptability, are shown in Figure 9A,B. Before storage, there were no significant differences in the sensory attributes between the coated and uncoated samples. At the end of the cold storage period, all coated broccoli samples showed higher acceptability for the sensory characteristics than did the uncoated ones. Furthermore, there were significant differences in sensory attributes between the coated broccoli samples. The coated broccoli samples with WPC/MPE at 3% had greater acceptance regarding sensory characteristics assessed against the broccoli samples coated with WPC/MPE at 1% and samples coated with WPC alone.

4. Discussion

Broccoli can be classified as a climacteric vegetable, which quickly deteriorates after harvesting. Furthermore, its shelf life is extremely short due to yellowing, water loss, softening, and off-odor occurrences [37]. Broccoli quality losses are mostly related to floret degreening and reduction of nutritional values [38]. The application of edible coatings improves the quality and extends the shelf life and safety of minimally processed foods by reducing the transfer of water vapor, gases, and aromas from or into them [39].
Whey protein (WP), which has lately garnered abundant attention for its health, safety, and biodegradability and as an eco-friendly substitute for chemical polymers, is considered one of the most promising edible coatings used for food preservation, particularly for vegetables and fruits [18]. Furthermore, edible coating materials made from whey proteins are characterized by transparency, odorlessness, flexibility, mechanical resistance, low viscosity, low tensile strength and high gas and water permeability in comparison to polysaccharide materials [18,40,41]. WP-based edible coatings have been applied to several vegetables and fruits, such as bananas, strawberries, apples, carrots, potatoes, and fresh spinach, to improve their quality [16]. Additionally, combining active ingredients (e.g., antimicrobials, antioxidants, probiotics/prebiotics, and flavor) into WP coating materials is a new technique in the industry, which aims to provide health benefits to consumers [18,42,43,44].
Several investigators reported that the addition of mango peel extract to polysaccharide or whey protein coatings significantly improved the physicochemical and biological properties, including opacity, moisture content, thickness, oxygen and water vapor barriers. Additionally, the total phenol content, antioxidant, and antimicrobial activity were increased too [18,45,46]. The results of the previous studies were in accordance with the findings of the current study; the antioxidant and total phenolic content of used WPC edible coatings increased after the incorporation of mango peel extract (Table 1 and Table 2). The maximum antioxidant activity and TPC content were recorded in the WPC/MPE 3% coating followed by WPC/MPE 1% and WPC alone (Table 1). These results could be associated with an increase in the ratio of MPE, the source of polyphenol compounds, from 1% to 3% (Table 1). In addition, the applied edible coating solutions demonstrated significant inhibition of some foodborne pathogens (Table 3). MPE has great antimicrobial activity against various food-borne pathogens, and this effect could be attributable to phenolic acids [47,48,49].
Polyphenol acids are quite vital compounds for the quality of vegetables, not only due to their contribution to the aroma and the color of most vegetables [50], but also due to their assistance to the conservation of the quality of vegetables during preservation. Polyphenol compounds have antimicrobial, anti-aging, and antioxidant properties, making these compounds a vital indicator to assess their impact on vegetable preservation [51]. The results of this study confirmed that a WPC edible coating incorporated with MPE could play an important role in maintaining postharvest quality and extending the shelf life of broccoli fresh-cuts during cold storage.
Weight loss has a high effect on fresh fruits and vegetables’ appearance because of shrinkage [11,52]. This phenomenon is prominent in processed and fresh-cut products [53], which leads to economic loss during storage. In the present study, all tested coatings conserved the weight loss of broccoli fresh-cuts compared to uncoated during 28 days of storage at 5 °C (Figure 1). Similar findings were also stated by Ansorena et al. [11] and Marquez et al. [53] regarding coated fresh-cuts of broccoli, apple, potato, and carrot. In addition, they stated that the coated samples with whey protein/pectin were superior for reducing weight loss compared with the uncoated samples.
In this study, the data in Figure 2A indicate that all the negative values of a* (-a* = greening,) indicate greening, and more dark green was observed in the WPC/MPE 3% application, followed by WPC/MPE 1% and WPC treatments. These results were in agreement with those reported by Ansorena et al. [11], who found that treated broccoli florets with edible coatings reduced the chlorophyll degradation and delayed the senescence phenomena. The reduction in chlorophyll deterioration of coated broccoli samples could be associated with the ability of used edible coatings to reduce the diffusion of O2 and increase the accumulation of CO2 around the broccoli surfaces, thus delaying the activity of oxidative enzymes (chlorophyllase) and reducing the oxidative processes that are responsible for chlorophyll degradation [54]. Furthermore, several studies reported that the edible coating application delays the color degradation of different vegetables or fruits i.e., strawberries [6,55], mango [7], broccoli [11], and fresh-cut apples [56].
The results presented in Figure 3 showed that the application of WPC or WPC/MPE edible coatings significantly reduced the respiration rate of stored broccoli in a similar technique to storage under a modified atmosphere. This could be attributed to antioxidant activity and the gas permeability of used WPC or WPC/MPE covering the food surface, possibly altering the internal content of CO2 and O2 gas, thus reducing the respiration rate of coated fruits [57]. Similar results were reported by Ansorena et al. [11], who reported that the use of chitosan edible coating causes a significant reduction in the respiration rate of minimally processed broccoli compared to the uncoated samples.
At the end of storage, the reduction in the contents of ascorbic acids (AsA), sulforaphane (SF), and total phenolic content (TPC) in the coated broccoli samples was lower than in the uncoated samples (Figure 4, Figure 5 and Figure 6). In addition, the treatment of broccoli samples with WPC/MPE (at 3%) coating maintained higher values of AsA, SF, and TPC in broccoli samples compared to all other treatments. In agreement, Ansorena et al. [11], Nguyen et al. [20], Shehata et al. [5], and Muley and Singnal [6] found that the treatment with edible coating alone or in combination with by-products significantly delayed the hydrolysis of bioactive compounds i.e., AsA and SF during the cold storage. This was possibly related to the antioxidant property of the edible coating (Table 1), which reduced the deteriorative oxidation reaction of those compounds via decreasing the activity of their enzymes. Consequently, this retarded AsA and SF degradation in the coated broccoli samples (Figure 4 and Figure 5). Furthermore, the maximum content of TPC was noted in broccoli samples coated with WPC/MPE 3%, followed by samples coated with WPC/MPE at 1% and WPC alone. This result is related to the amounts of polyphenol compounds existing in MPE (Table 1 and Table 2) that had been added to the coated broccoli through coating solutions. Peng et al. [58] reported that mango peel is an important by-product that is characterized by a high content of polyphenol compounds. On the other hand, the lowest value of TPC in the uncoated broccoli samples at the end of storage could be linked to the respiration rate and the breakdown of cell structure [59,60].
A similar trend was observed in total antioxidants. The improvement in the antioxidant capacity of the coated broccoli samples, especially WPC/MPE, could be attributed to the polyphenol content and other antioxidant compounds such as AsA and carotenoids existing in added MPE, which prevent the formation of free radicals [61]. In addition, Chatterton et al. [62] stated that the antioxidant characteristic of mango peel as an ingredient of edible coating originated from the high content of polyphenols, vitamins (C and E), carotenoids, and phytochemicals that prevent the formation of free radicals. As for WPC, the antioxidant capacity may be due to chelating metal ions by lactoferrin and serum albumin. Additionally, amino acids or peptides in the WPC can act as electron donors and might interact with free radicals to be more stable [63].
The findings of microbial counts showed the effectiveness of WPC and MPE as antimicrobial agents (Table 3). The antimicrobial properties of MPE and WPC have been stated by other authors in regard to different foods [18,42,44,64]. The reduction/inhibition of microorganisms’ growth (total bacterial, psychrotrophic, and fungi) in coated broccoli could be related to the modified atmosphere created by the edible coating, as well as the antimicrobial effect of WPC’s and MPE’s positively charged amino and polyphenol groups, which negatively charge microbial cell membranes, leading to the leakage of proteinaceous particles and other components of harmful microorganisms [65,66]. A high reduction of microbial counts (total bacterial, psychrotrophic, and fungi) was observed in broccoli samples coated with WPC and MPC/MPE (Figure 8, Table 4 and Table 5). In agreement with the findings noted by Shehata et al. [5] and Kandasamy et al. [18], the application of edible coatings was found to result in a lower inhibition of the growth of harmful microorganisms as compared to the uncoated samples.
WP edible coatings incorporated with MPE can be used as natural bio-conservatives in minimally processed broccoli because they do not introduce deleterious impacts on sensorial acceptability (Figure 9). These results agree with Cheng et al. [67], who reported that a polylactic/mango peel film coating enhanced the sensory attributes of fresh strawberries.

5. Conclusions

The edible coatings, WPC alone or in combination with MPE, seemed to have a favourable impact on the quality retention of minimally processed broccoli by delaying the changes in their weight loss, respiration rate, bioactive compounds (i.e., AsA, SF, TPC), total antioxidants, and yellowing processes. Furthermore, the application of WPC edible coating based on MPE (WPC/MPE) also significantly inhibited microbial growth (total bacterial count, psychrotrophic bacteria, and fungi counts) on the surface of minimally processed broccoli. However, significant differences were found between these coatings: WPC/MPE (at 3%) was superior during preservation, conserving broccoli at higher quality levels relative to WPC/MPE (at 1%) and WPC coatings by decreasing total microbial counts, respiration rate, and weight loss, and by improving appearance, bioactive compounds (i.e., AsA, SF, TPC) and total antioxidant retention. Findings of the sensory assessment of broccoli samples coated with WPC/MPE (at 3%) showed higher scores in almost all of the parameters examined. In conclusion, the quality preservation and the shelf life prolongation of minimally processed broccoli show that WPC coating, either combined or not combined with an MPE (at 3%), can be considered a better tool for commercial application, promoting the preservation and marketing of fresh and minimally processed broccoli. Further studies should be conducted on the impacts of coatings formed by whey protein concentrate and mango peel extract on fungi and bacteria species described as significant causal agents of postharvest diseases in economically important vegetables.

Author Contributions

Conceptualization, N.E., O.S.D. and A.A.-m.H.; methodology, N.E., O.S.D., S.M.A. and A.A.-m.H.; software, O.S.D., A.A.-m.H. and E.A.A.; validation, N.E., O.S.D., S.M.A. and A.A.-m.H.; formal analysis, O.S.D., A.A.-m.H. and E.A.A.; investigation, N.E., O.S.D., A.A.-m.H. and S.M.A.; resources, N.E., O.S.D., S.M.A., E.A.A. and A.A.-m.H.; data curation, O.S.D., A.A.-m.H., N.E. and E.A.A. writing—original draft preparation, N.E., O.S.D. and A.A.-m.H.; writing—review and editing, E.A.A., O.S.D. and N.E.; visualization, E.A.A., S.M.A., N.E. and O.S.D.; supervision, N.E. and O.S.D.; project administration, N.E. and O.S.D. All authors have read and agreed to the published version of the manuscript.

Funding

This paper is funded by the authors.

Data Availability Statement

Data sharing is not applicable to this article.

Acknowledgments

The authors are grateful to Faculty of Agriculture, Cairo University (Food science, Vegetable crops and Dairy Science Departments) for providing some facilities and equipment to finalize this work.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on weight loss percentage of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
Figure 1. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on weight loss percentage of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
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Figure 2. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on (A) greenness (-a*), (B) yellowness (b*), (C) chroma (C*), and (D) hue (h◦) of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
Figure 2. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on (A) greenness (-a*), (B) yellowness (b*), (C) chroma (C*), and (D) hue (h◦) of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
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Figure 3. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on respiration rate of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
Figure 3. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on respiration rate of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
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Figure 4. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on ascorbic acid (AsA) of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
Figure 4. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on ascorbic acid (AsA) of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
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Figure 5. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on sulforaphene content of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
Figure 5. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on sulforaphene content of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
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Figure 6. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on total phenolic content of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
Figure 6. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on total phenolic content of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
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Figure 7. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on antioxidant activity of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
Figure 7. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on antioxidant activity of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
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Figure 8. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on total bacterial count of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
Figure 8. Effect of whey protein concentrate combined with mango peel extract (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein concentrate + mango peel extract at 3%) on total bacterial count of broccoli fresh-cuts at 5 °C. Vertical bars indicate standard deviation (n = 6). Means and different letters indicate significant difference between treated and control broccoli for each storage period (Duncan’s multiple range test at 95%).
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Figure 9. A hedonistic scale of broccoli fresh-cuts (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein whey protein concentrate + mango peel extract at 3%) on period (P) = 0 day (A) and P = 28 day (B).
Figure 9. A hedonistic scale of broccoli fresh-cuts (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein whey protein concentrate + mango peel extract at 3%) on period (P) = 0 day (A) and P = 28 day (B).
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Table
Table 1. Total phenolic content and antioxidant activity of used edible coatings (WPC = whey protein concentrate alone, WPC + 1% MPE= whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein whey protein concentrate + mango peel extract at 3%).
Table 1. Total phenolic content and antioxidant activity of used edible coatings (WPC = whey protein concentrate alone, WPC + 1% MPE= whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein whey protein concentrate + mango peel extract at 3%).
Edible Coating SolutionsTotal Phenolic Content (mg GAE/g film)Antioxidant Activity (%)
WPC3.52 ± 0.53 c67.25 ± 0.48 c
WPC + 1%MPE22.29 ± 1.00 b90.25 ± 0.64 b
WPC + 3%MPE36.96 ± 0.39 a98.15 ± 0.53 a
Mean values in the same column with different small letters indicate significant differences according to Duncan’s multiple range test (p < 0.05). Values reported are the means ± standard deviations (n = 6).
Table
Table 2. Identification of the main phenolic compounds present in Mango Peel Extract (MPE).
Table 2. Identification of the main phenolic compounds present in Mango Peel Extract (MPE).
Phenolic CompoundRetention Time (min)Concentration (µg/g)
Pyrogallol2.919212.40 ± 1.053
Gallic acid3.47864.51 ± 0.202
Catechol5.6339.616 ± 0.005
p-hydroxybenzoic acid7.56240.65 ± 0.608
Catechin8.7994.64 ± 0.055
Chlorogenic acid9.02510.3188 ± 0.006
Vanillic acid9.55549.24 ± 0.554
Syringic acid10.7159.62 ± 0.100
p-Coumaric acid12.9333.5198 ± 0.577
Benzoic acid14.28687.91 ± 0.152
Ferulic acid15.3553.5818 ± 0.0115
Rutin16.09692.58 ± 0.571
O-Coumaric acid17.308128.39 ± 1.040
Mangiferin18.630235.96 ± 0.586
Resvertol19.8781278 ± 1.527
Cinnamic acid20.49821.304 ± 0.001
Quercetin21.416318.58 ± 0.563
Rosemarinic21.893259.22 ± 1.154
Table
Table 3. Antimicrobial activity of whey protein concentrate (WPC) and mango peel extract (MPE) against 8 clinical pathogenic microorganisms.
Table 3. Antimicrobial activity of whey protein concentrate (WPC) and mango peel extract (MPE) against 8 clinical pathogenic microorganisms.
Pathogenic BacteriaZones of Inhibition (mm)
WPCMPE
Escherichia coli ATCC 3521820.7 ± 0.896 aNo inhibition
Salmonella typhimurium ATCC 1402814.3 ± 0.450 b15 ± 1.25 a
Staphylococcus aureus MRSANo inhibition20 ± 0.09 a
Listeria monocytogenesNo inhibition23 ± 1.15 a
Staphylococcus aureus ATCC 2592319.6 ± 0.321 b22 ± 0.57 a
Bacilluscereus ATCC 33018No inhibition18 ± 0.00 a
Aspergilus niger nrrl 326No inhibitionNo inhibition
Aspergilus flavus nrrl 195729 ± 0.57 a20 ± 1.15 b
Mean values in the same column with different small letters indicate significant differences according to Duncan’s multiple range test (p < 0.05). Values reported are the means ± standard deviations (n = 6).
Table
Table 4. Psychrotrophic bacterial count (CFU/g) of broccoli fresh-cuts treated with different coating (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein whey protein concentrate + mango peel extract at 3%) during 28 days of cold storage.
Table 4. Psychrotrophic bacterial count (CFU/g) of broccoli fresh-cuts treated with different coating (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein whey protein concentrate + mango peel extract at 3%) during 28 days of cold storage.
Psychrotrophic Bacterial Count (Log CFU/g)Storage Period (Day)
Treatments07142128
ControlND *2.95 ± 0.16 a4.04 ± 0.32 a4.05 ± 0.29 a4.34 ± 0.18 a
WPCND2.67 ± 0.11 b2.67 ± 0.12 b2.67 ± 0.11 b2.72 ± 0.06 b
WPC + 1%MPE NDND2.20 ± 0.07 c2.25 ± 0.12 c2.29 ± 0.01 c
WPC + 3%MPE NDNDNDND1.84 ± 0.01 d
Mean values in the same column with different small letters indicate significant differences according to Duncan’s multiple range test (p < 0.05). Values reported are the means ± standard deviations (n = 6). ND * = Non-detected.
Table
Table 5. Fungal count (CFU/g) of broccoli fresh-cuts treated with different coating (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein whey protein concentrate + mango peel extract at 3%) during 28 days of cold storage.
Table 5. Fungal count (CFU/g) of broccoli fresh-cuts treated with different coating (WPC = whey protein concentrate alone, WPC + 1% MPE = whey protein concentrate + mango peel extract at 1% and WPC + 3% MPE = whey protein whey protein concentrate + mango peel extract at 3%) during 28 days of cold storage.
Fungal Count
(Log CFU/g)		Storage Period (Day)
TreatmentsZero7 days14 days21 days28 days
Control2.20 ± 0.00 a2.34 ± 0.18 a2.73 ± 0.03 a3.8 ± 0.25 a3.89 ± 0.11 a
WPC1.07 ± 0.00 b2.00 ± 0.13 b2.07 ± 0.00 b2.34 ± 0.18 b3.46 ± 0.17 ab
WPC +1% MPE ND *1.30 ± 0.02 c1.84 ± 0.02 c2.00 ± 0.10 c2.23 ± 0.04 c
WPC +3% MPE NDNDND1.47 ± 0.11 c1.47 ± 0.03 d
Mean values in the same column with different small letters indicate significant differences according to Duncan’s multiple range test (p < 0.05). Values reported are the means ± standard deviations (n = 6). ND = Non-detected.
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Elsayed, N.; Hassan, A.A.-m.; Abdelaziz, S.M.; Abdeldaym, E.A.; Darwish, O.S. Effect of Whey Protein Edible Coating Incorporated with Mango Peel Extract on Postharvest Quality, Bioactive Compounds and Shelf Life of Broccoli. Horticulturae 2022, 8, 770. https://doi.org/10.3390/horticulturae8090770

AMA Style

Elsayed N, Hassan AA-m, Abdelaziz SM, Abdeldaym EA, Darwish OS. Effect of Whey Protein Edible Coating Incorporated with Mango Peel Extract on Postharvest Quality, Bioactive Compounds and Shelf Life of Broccoli. Horticulturae. 2022; 8(9):770. https://doi.org/10.3390/horticulturae8090770

Chicago/Turabian Style

Elsayed, Nesren, Ashwak Abdel-moneim Hassan, Suzy M. Abdelaziz, Emad A. Abdeldaym, and Omaima S. Darwish. 2022. "Effect of Whey Protein Edible Coating Incorporated with Mango Peel Extract on Postharvest Quality, Bioactive Compounds and Shelf Life of Broccoli" Horticulturae 8, no. 9: 770. https://doi.org/10.3390/horticulturae8090770

APA Style

Elsayed, N., Hassan, A. A. -m., Abdelaziz, S. M., Abdeldaym, E. A., & Darwish, O. S. (2022). Effect of Whey Protein Edible Coating Incorporated with Mango Peel Extract on Postharvest Quality, Bioactive Compounds and Shelf Life of Broccoli. Horticulturae, 8(9), 770. https://doi.org/10.3390/horticulturae8090770

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