DETERMINATION OF VITAMINS IN MELON AND ITS POWDER USING SPECTROPHOTOMETERY

ABSTRACT

In this scientific work, the concentration of the main 5 vitamins (C, A, E, B2, B6) was determined in two varieties of melons grown in the Khorezm region (Uzbekistan) – Gurvak and Aknovot. Melon raw materials were also dried and ground into powder. To obtain melon powder, thermal treatment is necessary, and the degree of preservation of vitamins in the powder was also studied. For the analysis of vitamins, spectrophotometric methods were used, mainly infrared and ultraviolet spectrophotometric equipment, as well as standardization methods. Vitamins C and B6 have been found to be more common than other vitamins. Vitamin A, on the contrary, is present in very small amounts.

АННОТАЦИЯ

В данной научной работе определена концентрация основных 5 витаминов (С, А, Е, В₂, В₆) в двух сортах дынь, выращенных в Хорезмской области (Узбекистан) – Гурвак и Акноввот. Также сырье дыни высушивали и измельчали ​​в порошок. Для получения порошка дыни необходима термическая обработка, а также изучалась степень сохранности витаминов в порошке. Для анализа витаминов использовались спектрофотометрические методы, в основном инфракрасное и ультрафиолетовое спектрофотометрическое оборудование, а также методы стандартизации. Обнаружено, что витамины С и В6 встречаются чаще, чем другие витамины. Витамин А, напротив, присутствовал в очень малых количествах.

Keywords: melon, vitamin, melon powder, Gurvak, spectrophotometer, FTIR, infrared, ultraviolet spectroscopy, data analysis

Ключевые слова: дыня, витамин, дынный порошок, Гурвак, спектрофотометр, инфракрасная спектроскопия с Фурье-преобразованием, инфракрасная, ультрафиолетовая спектроскопия, анализ данных.

Abbreviations:

FTIR – Fourier transform infrared spectroscopy

UV-Vis – Ultraviolet–visible spectrophotometry

PCA – principal component analysis

INTRODUCTION

Melon (Cucumis melo L.) belongs to the pumpkin family and is widely consumed as a dessert vegetable/fruit. In addition to sugars and water, melon contains a complex of vitamins, minerals, dietary fiber and biologically active compounds (carotenoids, phenolic compounds). According to reviews of the nutritional value of melons [1-3], melon is considered a source of provitamin A (β‑carotene), a significant source of vitamin C, an additional (but not the main) source of B vitamins and folate, a product with low energy value and high hydration capacity.

Most sources indicate that melon contains from 15 to 40 mg of vitamin C per 100 g of fresh weight, depending on the variety (nutmeg, honey, cantaloupe, etc.), the degree of maturity and growing and storage conditions [4].

According to studies on the stability of vitamin C in melons [5], there is a significant decrease in the content of ascorbic acid during long—term storage and heat treatment; the maximum concentration is in fully ripe fruits consumed fresh.

The color of the melon pulp is closely related to the content of carotenoids, especially beta‑carotene. Varieties with orange/bright yellow flesh (for example, cantaloupe) contains more beta‑carotene, while light yellow and greenish varieties contain less.

According to phytochemical reviews, the beta‑carotene content in melon can vary from 0.1 to 3-4 mg/100 g, depending on the variety [6]. Studies of the carotenoid profile of melon crops show that melon also contains other carotenoids (lutein, zeaxanthin), however, it is beta‑carotene that is the main provitamin A [7].

Melon does not contain many B vitamins, among them: B1 (thiamine) is involved in carbohydrate metabolism and the work of the nervous system, B2 (riboflavin) is important for energy metabolism and antioxidant protection, B3/PP (niacin) is involved in the metabolism of proteins, fats and carbohydrates, B6 (pyridoxine) is associated with with amino acid metabolism and the functioning of the nervous system. Compared to other foods, they are found in melon in moderation, but in combination with other vegetables and fruits, melon helps to form the overall vitamin balance of the diet.

Some studies indicate the presence of folate in melon in amounts up to 20-40 micrograms/100 g (depending on the variety and method of analysis) [9]. Although melon is not the main source of folic acid, it is considered as an additional component of the diet, increasing the total intake of folate.

In the literature on the chemical composition of melon, there is a low content of vitamin K (phylloquinone) and trace amounts of vitamin E (tocopherols) [10]. These vitamins are present in melon in smaller quantities than, for example, in leafy greens (vitamin K) or vegetable oils and nuts (vitamin E). However, the overall antioxidant effect can be enhanced by the interaction of vitamin C, carotenoids, and small amounts of tocopherols.

A review of experimental studies shows that the vitamin composition is significantly influenced by the genetic characteristics of the variety, agro-climatic conditions, degree of maturity, storage and processing conditions [1, 2].

Modern research is aimed at breeding highly sensitive varieties and developing technologies to preserve the vitamin complex during storage and processing [1, 3, 6].

Melon is grown in large quantities in the Khorezm region. The harvest in 2024 was in Khorezm 172.7 million tons and in Uzbekistan the harvest in 2024 was 2683.8 million tons. In 2025, melon&watermelon exports amounted to 232.9 thousand tons and it’s was in Khorezm 12,2 thound tons. This requires a more extensive and accurate study of their chemical composition every year. This is very important when exporting products to countries that have strict chemical requirements for importing products into their own country.

Our main purpose is to study the vitamin content of melon varieties grown in the Khorezm area (Uzbekistan), and to study the composition of vitamins which obtained from melon powder after thermal processing.

Initially, Calibration standards with specific concentrations of the above mentioned vitamins were imported, they were adjusted to different percentages in the laboratory and the absorbance level was determined. A linear regression graph was constructed for each vitamin.

MATERIALS AND METHODS

In this scientific study, water-soluble vitamins B₂, B₆, C and fat-soluble vitamins A and E in melon products were quantified using FTIR equipment and Ultraviolet spectroscopy methods. The FTIR (model: Jasco FT/IR-4600) equipment was used to determine the amount of vitamins C and E, and the UV-Vis (model UV 755) equipment was used to determine the amount of vitamins B₂, B₆, and A.

Preprocessing method for vitamins C, B₂, B₆:

1) Approximately 10 g of melon pulp was taken.

2) Mechanical homogenization.

3) Water extraction in a rotary evaporator (42–45 ℃)

4) Add 20 mL of distilled water

5) Vortex for 5 minutes

6) Filter 0.45 μm

7) Analyze the extract in a spectrophotometer.

Preprocessing method for vitamins A and E:

1) Approximately 10 g of melon pulp was taken.

2) The pulp was crushed and mixed with ethanol to extract lipids.

3) The organic phase was separated by adding 30 mL of hexane. (For vitamin E – 96% ethanol was added in a 1:2 ratio)

4) Centrifugation (5000 rpm, 10 min)

5) Filtration 0.45 μm. The filtrate was stored in the dark.

6) Analysis of the extract in a spectrophotometer.

Mean centering of the data, Savitzky-Golay 2^nd derivative, and obtaining a Linear regression graph from the control samples. Determination of the concentrations of the prepared melon samples were based on the absorbance.

RESULTS AND DISCUSSION

Initially, the absorption of the standard solutions was determined. 5 standard samples of vitamin A, 6 samples of B₂, and 6 samples too of B₆ with different concentrations were prepared in the laboratory (Table 1). Vitamin B₆ gives a peak at 290 nm ultraviolet. B₂ at 223-267 nm [11, 12]. Vitamin A gives a peak at 325 nm ultraviolet wavelength [13]. The phenolic radical (C-O) of vitamin E shows a peak in the range of 1260-1190 nm. We adopted 1210 nm.

Table 1.

Different concentrations of standard samples of vitamin A, B₂, B₆

In the laboratory, standard samples of Vitamin C were brought to 8 different concentrations. Their FTIR spectra were measured and their concentration is shown in Table 2. Each sample was spectrally analyzed 3 times. FTIR indicators: Resolution: 4. Sample scan time: 64. Background scan time: 64. Background was scanned once every 5 analyses.

The intensity values of the 1720 nm peak are shown in Table 2.

Table 2.

Concentrations of standrt samples of vitamine C after pre-procecing of data (Mean centred and Savitzky-Golay2^nd derivative):

The intensity values of the peak at 1708 nm are shown in Table 3.

Table 3.

Vitamin C concentration determined in Melon samples

Similarly, a standard sample of vitamin E was prepared in the laboratory at 6 different concentrations and pick are of vitamins in yellow area (Table 4). The concentration of vitamin E in their content was determined from the Table 5.

Table 4.

Concentrations of standrt samples of vitamine E

The intensity values of the 1210 nm peak are presented in Table 5.

Table 5.

Vitamin E concentration determined in Melon samples

You can also compare the amount of vitamins in melons grown in Khorezm region with the indicators determined in liquid chromatograms in our previous experiments [14, 15] and about the technique and thermodynamics of obtaining Powder from Melon [16].

PCA scores of the whole spectrum by FTIR of melon samples were also obtained (Fig. 1). PCA analysis was performed separately for the part of the spectrogram related to vitamin C (1735 nm — 1700 nm) (Fig. 2) and the part of the spectrogram belonging to vitamin E (1260 nm — 1190 nm) (Fig. 3).

Further, PCA data analysis was performed in Figures 1-3. Figure 1 shows the PCA result of the FTIR spectrogram of melon samples, in which the melon powder and the melon itself are located in a separate area. Figure 2 shows the PCA analysis of the FTIR spectrum of vitamin C (1800-1690 nm), in which the powder and the melon sample are also located in a separate region. Figure 3 shows a PCA analysis of the area of vitamin E (1330-1150 nm). This analysis will help us determine whether the samples are well cleaned in the laboratory.

Figure 7. PCA Scores for Melon Samples and its Powder

Figure 8. PCA Scores for the area of vitamin C on Melon Samples

Figure 9. PCA Scores for the area of vitamin E on Melon Samples

Also the determined concentrations of vitamins are shown in Table 6. They were determined by the intensity of the object using a linear regression equation of the standard samples.

Table 6.

The results of the analysis

CONCLUSION

Among the vitamins contained in melons, C and B₆ were found to be more common than other vitamins. It was found that vitamin A was absent in this study, or they were present in very small quantities. We considered it good to choose a liquid chromatogram device for determining vitamin A. Also, when determining the content of vitamins B₂, B₆ and A in Melon Powder using UV-Vis, their peaks were not visible.

The method used above is considered an economical method because it uses few reagents and gives quick results. It is very important to correctly apply preprocessing methods in the laboratory from cultivated melon varieties and to be able to use reagents cleanly. OriginPro 2021 software was used to perform statistical methods.

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