COMPREHENSIVE MINERAL, VITAMIN AND PHENOLIC PROFILING OF BANANA PEEL (Musa spp.) WASTE USING ICP-OES AND HPLC FOR POTENTIAL FOOD VALORISATION

ABSTRACT

Banana peel is commonly discarded as waste, although it contains valuable nutrients and bioactive compounds. This study evaluated its mineral composition, vitamins and selected phenolics using ICP-OES and HPLC. Potassium was the predominant mineral, and niacin was the most abundant vitamin. Several phenolic compounds, including apigenin and gallic acid, were identified. The results suggest that banana peel may serve as a promising raw material for functional food applications, provided that safety requirements are met.

АННОТАЦИЯ

Банановая кожура обычно рассматривается как отход, хотя содержит ценные питательные и биологически активные вещества. В данной работе были изучены её минеральный состав, витамины и отдельные фенольные соединения с использованием ICP-OES и ВЭЖХ. Основным минералом оказался калий, среди витаминов преобладал ниацин. Были также выявлены фенольные соединения, включая апигенин и галловую кислоту. Полученные данные показывают, что банановая кожура может рассматриваться как перспективное сырьё для функциональных пищевых продуктов при условии соблюдения требований безопасности.

Keywords: banana peel, mineral composition, vitamins, phenolic compounds, ICP-OES, HPLC.

Ключевые слова: банановая кожура, минеральный состав, витамины, фенольные соединения, ИСП-ОЭС, ВЭЖХ.

Introduction. Banana (Musa spp.) is one of the most widely cultivated and consumed fruits worldwide, with Cavendish cultivars dominating global production [1]. During consumption and processing, the peel accounts for about 30–40% of the fruit weight and is usually discarded as waste [2, c. 3]. The growing volume of such by-products has increased interest in their potential reuse as valuable raw materials in the food industry [3, c. 2].

Previous studies indicate that banana peel contains carbohydrates, dietary fibre, minerals, vitamins and phenolic compounds with antioxidant properties [4, c. 2; 5, c.2]. However, reported values often vary due to differences in cultivar, processing conditions and analytical methods. Moreover, many studies focus on individual compound groups rather than providing a comprehensive compositional profile.

Therefore, the present study aimed to determine the mineral composition, vitamin content and selected phenolic compounds in banana (Musa spp., Cavendish) peel using ICP-OES and HPLC, and to assess its potential for food-related applications.

Materials and methods

Plant material. Banana (Musa spp., Cavendish cultivar) fruits imported from Ecuador were purchased from local retail markets in Andijan, Uzbekistan. The peels were manually separated, thoroughly washed with distilled water, and dried at 60 °C to constant weight. The dried material was ground to a fine powder and stored in airtight containers at room temperature until analysis.

Reagents, standard substances, and analytical instruments

All reagents were of analytical or HPLC grade. Concentrated HNO₃ and H₂O₂ were used for mineral analysis, while acetonitrile, acetic acid, sodium hydroxide and ultra-pure water were applied in chromatographic procedures. Multi-element standard solutions (10 mg/L in 2% HNO₃; High-Purity Standards, USA) were used for ICP-OES calibration. Phenolic and vitamin standards were obtained from certified commercial suppliers and prepared according to analytical requirements.

Determination of mineral composition (ICP-OES)

Mineral analysis was carried out using an iCAP PRO X Duo ICP-OES (Thermo Fisher Scientific, USA) equipped with QTegra ISDS software. Approximately 1 g of dried sample was dry-ashed at 500 °C for 5 h, followed by digestion with concentrated HNO₃ and H₂O₂. The digest was diluted to 100 mL with ultra-pure water and filtered before analysis.

Operating conditions included an RF power of 1150 W, nebulising gas flow of 0.6 L/min, cooling gas flow of 12.5 L/min, auxiliary gas flow of 0.5 L/min and a 2 mm central tube. A concentric glass nebuliser with a cyclonic spray chamber was used. Each sample was measured in triplicate. Calibration curves were constructed using standard solutions in the range of 10–500 µg/L.

All measurements were performed in triplicate.

Determination of phenolic compounds (HPLC)

Phenolic compounds were determined using an LC-40 Nexera Lite HPLC system (Shimadzu, Japan) with a PDA detector and a Shim-pack GIST C18 column (150 × 4.6 mm; 5 µm). Separation was performed using a gradient of acetonitrile and 0.5% aqueous acetic acid at a flow rate of 0.5 mL/min and 40 °C, with detection at 300 nm.

For extraction, 1 g of dried sample was sonicated with 25 mL of 96% ethanol at 60 °C for 20 min. The extract was centrifuged, filtered (0.45 µm) and analysed. Quantification was carried out using external calibration with authentic standards.

Table 1.

Mobile phase gradient program

Figure 1. Chromatogram of standards at 300 nm

Determination of water-soluble vitamins (HPLC)

Water-soluble vitamins were analysed using an LC-40 Nexera Lite HPLC system (Shimadzu, Japan) with a PDA detector. One gram of the sample was extracted with 25 mL of 0.1 N HCl by sonication at 60 °C for 20 min, followed by filtration (0.22 µm).

Separation was achieved on a Shim-pack GIST C18 column using gradient elution of acetonitrile and 0.5% aqueous acetic acid. Detection was performed at 265, 291 and 550 nm depending on the vitamin. Quantification was based on calibration curves of standard solutions.

Table 2.

Mobile phase gradient program for vitamin analysis

Table 3.

Mobile phase gradient program for determining Vitamin C content

Results and discussion. Quantitative analysis of macro- and microelements in banana peel was performed using ICP-OES. Table 4 presents a concise overview of the principal experimental findings.

Table 4.

Content of macro and microelements in banana peel (µg/kg).

The mineral composition of banana peel is presented in Table 4. Potassium was the predominant element (1,799,899.78 ± 6654.59 µg/kg DW), confirming its nutritional relevance. Potassium plays an important role in electrolyte balance and cardiovascular function [6, c. 727].

Magnesium, sodium and calcium were also detected in considerable amounts. These elements are involved in energy metabolism, bone structure and osmotic regulation [7, c. 210]. Among trace elements, manganese, iron and zinc were identified, all of which contribute to antioxidant defence, oxygen transport and immune function. Copper and selenium were present in lower concentrations but remain biologically significant due to their role in redox processes.

Low levels of potentially toxic elements, including lead and cadmium, were detected. Although their concentrations were relatively small, this finding emphasises the need for safety evaluation before food application [8, c. 3].

Overall, the mineral profile suggests that banana peel contains nutritionally relevant macro- and microelements. However, quality control and toxicological assessment are necessary prior to its incorporation into food systems.

The results of determining the amount of phenolic compounds in the sample extract.

The chromatogram of the 1 g sample extract was obtained (Figure 4), and based on the results, the amount of phenolic compounds in 100 g of the sample was calculated using the following formula:

Where:

• X is the amount of phenolic compounds in 100 grams of the sample, expressed in mg.
• C_phen​ - is the concentration of phenolic compounds in the extract, determined using the HPLC method, expressed in mg/L.
• V_extract​ - is the volume of the sample extract, in litres.
• m _sample​ - is the mass of the sample used for the extraction, in grams.

The calculated results are presented in Table 5, which shows the amount of phenolic compounds in the sample (aqueous extract of banana peel) per 100 grams

Figure 2. Chromatogram for the determination of polyphenols in the sample extract

The chromatogram illustrates the separation of phenolic compounds detected in the banana peel extract. Identified peaks correspond to individual phenolics, and quantification was performed based on peak areas and retention times.

Table 5.

Amount of polyphenols in the extract and retention times

Phenolic profiling results are summarised in Table 5. Apigenin was the most abundant compound (1.283 mg/100 g DW), followed by gallic acid, salicylic acid, rutin and quercetin, while kaempferol was not detected.

The presence of these phenolic compounds indicates that banana peel possesses antioxidant potential, which may enhance its functional value [9, c. 230]. The coexistence of several flavonoids may also contribute to synergistic antioxidant effects.

The results of determining the vitamins in the sample extract.

The chromatogram of the sample extract (Figures 3, 4) was obtained, and based on the results, the amounts of vitamins in 100 grams of the fruit were calculated using the following formula:

Where:

• X is the amount of vitamins in 100 grams of fruit, expressed in mg.
• C _vit -is the concentration of the vitamin in the extract, determined by the HPLC method, expressed in mg/L.
• V_extract - the volume of the sample extract, in litres.
• m _sample -is the mass of the sample used for extraction, in grams.

The calculated results are presented in Table 6, which shows the amounts of vitamins per 100 grams of the sample.

Figure 3. Chromatogram of vitamins identified in banana peel extract

Figure 4. Determination of vitamin C content in banana peel extract

Table 6.

Amount of vitamins in the extract and retention times

Vitamin composition is presented in Table 6. Vitamin B3 (niacin) showed the highest concentration (31.843 mg/100 g DW), followed by vitamins B9, B1, PP, B2, C and B6, while vitamin B12 was not detected.

The presence of B-complex vitamins and vitamin C highlights the nutritional relevance of banana peel for potential food applications [10, c. 2]. However, further studies are needed to evaluate their bioavailability and practical dietary contribution.

Conclusion. This study shows that banana (Musa spp., Cavendish) peel contains nutritionally relevant macro- and microelements, especially potassium, magnesium and calcium, together with detectable amounts of phenolic compounds and water-soluble vitamins. The identification of flavonoids such as apigenin, gallic acid and rutin supports its potential as a source of natural antioxidants. The presence of B-complex vitamins and vitamin C further indicates that this by-product may have value for food-related applications.

At the same time, the detection of lead and cadmium emphasises the need for careful safety assessment before any practical use in food systems. Although banana peel appears to be a promising value-added raw material, its application should be supported by appropriate quality control and processing strategies.

Future research should address compound bioavailability, optimisation of extraction procedures and evaluation of its incorporation into functional food products.

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