Optimization and Preliminary Physicochemical Characterization of Pectin Extraction from Watermelon Rind (Citrullus lanatus) with Citric Acid

Abstract

Watermelon rind was used for the pectin extraction with citric acid as the extractant solvent. The effects of pH (2.0-3.0), extraction time (45-75 min), and liquid-solid ratio (10 : 1 to 40 : 1 mL/g) on the pectin yield, degree of esterification, methoxyl content, and anhydrouronic acid content were investigated using Box-Behnken surface response experimental design. The pH was the most significant variable for the pectin yield and properties. The responses optimized separately showed different optimal conditions for each one of the variables studied in this work. Therefore, the desirability function was used to determine the sole theoretical optimum for the highest pectin yield and highest anhydrouronic acid content, which was found to be pH of 2.0, extraction time of 62.31 min, and liquid-solid ratio of 35.07 mL/g. Under this optimal condition, the pectin yield, degree of esterification, methoxyl content, and anhydrouronic acid content were 24.30%, 73.30%, 10.45%, and 81.33%, respectively. At optimal conditions, watermelon rind pectin can be classified as high methoxyl and rapid-set pectin with high quality and high purity. Practical Applications. This study evaluated the pectin extraction from watermelon rind and carried out an optimization of multiple responses as a function of pH, time, and liquid-solid ratio to obtain the best preliminary quality parameters (pectin yield and anhydrouronic acid content). The results revealed that watermelon rind waste can be an inexpensive source to obtain good pectin quality and high purity. According to the chemical characterization and physicochemical properties studied, the extracted pectin from watermelon rind would have a high potential to be used in food industry.

Pharmaceutical Assessment of Watermelon Rind Pectin as a Suspending Agent in Oral Liquid Dosage Forms

“…The analysis of the FTIR spectra of the extracted watermelon pectin depicted a high degree of similarity when peak positions were compared with commercial rapid-set pectin and reported analogous works on pectin from watermelon rind [28,[33][34][35] (Figure 1). The presence of intra-and intermolecular hydrogen bonding, C-H and C = O stretching vibrations of esterified carboxyl groups, and free carboxyl groups was observed at spectra frequencies 1600-1300, 2926.91 cm -1 , and 1709.55 cm -1 , respectively [28,33,34]. Moreover, the weak peaks (889.67-504.55 cm -1 ) are linked possibly to the αand βconfigurations of pyranose cycles.…”

“…The amount of pectin obtained ( Table 2 ) from the watermelon rind was similar to the yields reported by centrifugation (14.3%) and higher than that reported from cheesecloth methods (10.6%) indicating that an efficient extractive procedure was used [ 26 ]. The proximate composition obtained ( Table 2 ), which are essential factors in the utilization and storage of pectin, showed low values when compared to standards [ 27 , 28 ]. The low moisture content indicates that the extracted pectin can be safely stored for a longer duration with lower susceptibility to microbial growth while the low ash content indicates lower levels of inorganic impurities, an indication that the watermelon pectin was of satisfactory quality [ 28 , 29 ].…”

“…The proximate composition obtained ( Table 2 ), which are essential factors in the utilization and storage of pectin, showed low values when compared to standards [ 27 , 28 ]. The low moisture content indicates that the extracted pectin can be safely stored for a longer duration with lower susceptibility to microbial growth while the low ash content indicates lower levels of inorganic impurities, an indication that the watermelon pectin was of satisfactory quality [ 28 , 29 ]. The high total carbohydrates compared to the crude protein and fat indicate that carbohydrates are the highest calorie contributor [ 30 ].…”

High-Intensity Ultrasound-Assisted Extraction of Pectin from Mango Wastes at Different Maturity

“…Pectin is the most widely used polysaccharide in the food industry [7]. Pectin is a plant cell wall polysaccharide, consisting mainly of D-galacturonic acid, followed by D-galactose and L-arabinose [8]. Raw materials such as citrus peels and apple pulp have been used for pectin production [9], although mango also contains pectin in its peel [10].…”

“…Raw materials such as citrus peels and apple pulp have been used for pectin production [9], although mango also contains pectin in its peel [10]. Traditionally, pectin extraction uses an acid solution and heat [8]; however, emerging technologies such as high-intensity ultrasoundassisted extraction (HIUAE) can improve the efficiency of the process [11].…”