|Nur Zafirah A. Daud||Department of Chemical Science, Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong, BE 1410, Brunei Darussalam|
|Bazla Najlaa M. Said||Department of Chemical Science, Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong, BE 1410, Brunei Darussalam|
|Fairuzeta Ja'afar||Department of Chemical Science, Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong, BE 1410, Brunei Darussalam|
|Hartini M. Yasin|
|Eny Kusrini||Department of Chemical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, Depok 16424, Indonesia|
Citrus maxima white pith was utilized for the isolation of pectin under acidified condition using L-(+)-tartaric acid, at extraction pH in the range of 1.0 and 2.0. The extraction yield and physicochemical properties (ash content, equivalent weight, methoxy content, anhydrouronic acid, degree of esterification) of the isolated pectin was investigated. The highest yield (70.2%) obtained in this extraction was at pH 1.0, 60°C, 120 minutes. The optimized condition of the isolated pectin in this study was based on the yield and physicochemical properties, where pectin extracted at pH 2.0 and 60-80°C for 60-120 minutes resulted in a 59.6% yield, with low ash content (2.82%), highest equivalent weight (1098.8) for gelling effect and highest DE (39.2%). The findings are within the range for a good quality pectin. The FTIR spectra of the isolated pectin at different pH mediums, but at constant temperature of 70°C and extraction time of 60 minutes were compared. The presence of methyl esterified carboxyl (1696 cm-1) and carboxylate group confirms the presence of pectin. This isolated pectin as an innovative raw material is potentially applicable for adsorbents, thin films, environmentally-friendly agents and green corrosion inhibitors.
Degree of esterification; Methoxyl content; Pomelo peel; Pectin; Food waste;
Food waste (FW) has become a global problem, it is estimated about one third (1.3 billion tonnes) of the world food production is wasted. Recognizing that this staggering amount of FW can raise circular economy, extensive research has been carried out in recent years, predominantly in the utilization of fruit waste or by-products such as pomaces, rinds, peels as precursor and conversion into high value added products such as bioactive components, biobased and biodegradable products. These measures align with the current legislation on sustainable development goals (SDGs) and green chemistry principles of using renewable source as starting materials, which can be considered as environmentally friendly compounds that were less or non-toxic to human or living organisms (Mulia et al., 2019).
Citrus maxima (CM), the biggest citrus fruit and a member of the Rutaceae family, is one of the most cultivated fruits. CM is native to Southeast Asian countries and is known locally in Brunei Darussalam, Malaysia, and Indonesia as “Limau Bali.” It is known to have a high nutritional value and its by-products are potentially rich sources of functionalized molecules such as phytochemicals, dietary fibers, and pectin (Bátori et al., 2017).
CM consists of three segments, the flavedo (peel), albedo (white pith), and endocarp (pulp). The edible portion, the pulp, is usually eaten fresh while its peel is typically discarded as waste. Nevertheless, the waste portions such as the flavedo can be used for the extraction of essential oil, while the spongy white pith, which comprises up to 30% of the fruit’s total weight, is a promising source of pectin (~35%) production (Methacanon et al., 2014; Quoc et al., 2015). Pectin is a linear polysaccharide found in the majority of primary cell walls and middle lamellae of most plants and fruits. The main structure of pectin is composed of linear 1,4-linked a-D-galacturonic acid (GalA) chain molecules bonded by glycosidic linkages (Altaf et al., 2015; Rose & Abilasha, 2016). The carboxyl (COOH) groups present alongside the chain are mainly esterified with methoxy (CH3O) groups, thus it is naturally present as methyl esters. Commercial pectin is normally obtained from citrus peels (20–30%) and apple pomace (10–15%) (Raj et al., 2012). Conventionally, pectin extraction is carried out in a hot diluted acidic condition at 60–100°C, pH 1.5–3.0, using various strong mineral acids such as nitric acid (HNO3), hydrochloric acid (HCl), and sulfuric acid (H2SO4) (Yapo, 2009).
Strong acids are corrosive and the liquid waste generated from this process leads to high waste removal and treatment costs and poses hazards for the environment and health (Liew et al., 2014). Thus, the extraction of pectin from the by-products of fruits using organic acids such as citric acid, mallic acid, and tartaric acid are preferred on economic and environmental grounds. The hot extraction of pectin from sweet lemon (Mosambi) peel was found to produce a high yield of pectin when citric acid (76.0%) was used, while it was lowest with HNO3 (46.4%) at pH 1.5, 80°C, 60 min (Devi et al., 2014). Pectin quality and purity also depend on numerous other factors such as ash content, molecular weight (MW), methoxyl (MeO) content, and degree of esterification (DE) (Azad et al., 2014; Roy et al., 2017). The main objectives of this study were to: (a) determine whether the yield and the physicochemical properties of the pectin extracted from CM white pith are pH-dependent; and (b) to investigate the physicochemical properties of the extracted pectin.
The yield and physicochemical properties of the extracted pectin were significantly affected and highly dependent on pH values. The maximum yield and DE obtained in this extraction were 70.2% and 39.2%, respectively. The pectin yield has no correlation with the physicochemical properties (ash content, eq wt., and DE). In this study, the extraction of pectin derived from CM acidified using tartaric acid at pH 2.0 produced good-quality pectin with a low ash content, and the highest equivalent weight and DE for gelling properties. This optimized condition would be suitable for future studies on the extraction of pectin, for possible value-added applications.
The author acknowledges the financial assistance from Universiti Brunei Darussalam in carrying out this study.
Mohamed, H., 2016. Extraction and Characterization of Pectin from Grapefruit Peels. MOJ Food Processing & Technology, Volume 2(1), pp. 31–38