Soybean Oil Enriched with Antioxidants Extracted from Watermelon (Citrullus colocynthis) Skin Sap and Coated in Hydrogel Beads via Ionotropic Gelation

Muhammad Farooq,Monica Trif,Mahniya Sharifi,Sneh Punia Bangar,Bianca Eugenia Ștefănescu,Elham Azadfar,Zohre Bahrami,Alexandru Rusu,Yunyang Wang,Ramezan Ali Jabaleh,Naila Ilyas

doi:10.3390/coatings11111370

Abstract

Many plants and fruits are rich in antioxidant and antimicrobial compounds, such as phenolic compounds. Watermelon is one example, as various parts of the fruit present interesting phytochemical profiles. This study demonstrates that a natural C. colocynthis (watermelon) (W) skin sap (SS) extract can effectively improve the oxidative stability of microencapsulated soybean (SB) oil. By employing a combination of alginate–xanthan gums (AXG) in a matrix hydrogel bead model with WSS extract, high encapsulation efficiency can be obtained (86%). The effects of process variables on the ultrasound-assisted extraction (UAE) of phenolic compounds from watermelon (W) skin sap (SS) using the response surface methodology (RSM), as an optimized and efficient extraction process, are compared with the effects of a conventional extraction method, namely the percolation method. The WSS extracts are obtained via UAE and RSM or the conventional percolation extraction method. The two obtained extracts and synthetic antioxidant butylated hydroxytolune (BHT) are added to SB oil separately and their antioxidant effects are tested and compared. The results show the improved oxidative stability of SB oil containing the extract obtained via the optimized method (20–30%) compared to the SB oil samples containing extract obtained via the percolation extraction method, synthetic antioxidant (BHT), and SB oil only as the control (no antioxidant added). According to existing studies, we assume that the use of WSS as an effective antioxidant will ensure the prolonged stability of encapsulated SB oil in hydrogel beads, as it is well known that extended storage under different conditions may lead to severe lipid oxidation.

Highlights

In the 2020–2021 crop year, soybean (SB) oil was the most produced type of oilseed globally; worldwide, around 362 million metric tons of soybeans were produced [1]
The extraction method used for the different natural compounds had an influence on their extraction rates and efficiency levels
The results showed the effects of different concentrations of the WSS on the inhibitory activity of free radicals, while the scavenging activity of the extract significantly increased by increasing the sap concentration

Summary

Introduction

In the 2020–2021 crop year, soybean (SB) oil was the most produced type of oilseed globally; worldwide, around 362 million metric tons of soybeans were produced [1]. The oxidation reactions are the important factor involved in oil and fat spoilage, because these reactions cause unwanted changes in the flavor, color, and texture of fat- and oil-containing products [2,3]. The speed of the reaction depends on the fatty acid pattern of the oil Peanut oil > soybean oil, linseed oil, safflower oil), which increases with the number of double bonds Unsaturated fatty acids can be oxidized spontaneously by atmospheric oxygen at room temperature or at moderately elevated temperatures. The rate of reaction increases with the number of double bonds in the fat molecule. Stearic, oleic, linoleic, and linoleic fatty acids, which increases the oxidation risk [7,8]

Methods

Results

Conclusion