Agricultural Pectin Extraction in Iranian Experimental Settings

*Roshanak Vakili*

### **Abstract**

Pectins are belonged to one important group of polysaccharides extracted from the plant cell walls. Commercial pectins are widely used in the cosmetic, pharmaceutical, and food industries, mainly as texturizing, emulsifying, stabilizing, and gelling agents. Due to rich contents of partially esterified galacturonic acid (GalA) found in agri-food waste, the valorization of recovery process needs to be further developed with economic and environmental benefits. Accordingly, in order to maximize the utilization of these residues, some researchers attempted to extract multiple valuable products from plant waste like pectin from mango peel or simultaneously extracted pectin and polyphenols from pomegranate peels, because the simultaneous extraction seems more efficient due to decreased process time and cost. The characteristics and applications of pectins are strongly influenced by their structures depending on plant species, tissues, and extraction methods. This review aims to review the optimal extraction conditions using new promising methods in order to obtain pectin from Iran's Agro waste and assess physicochemical parameters in recent Iranian experimental study designs, including microwave heating processes and ultrasonic treatment.

**Keywords:** pectin, Iranian studies, extraction methodology, agricultural waste, secondary metabolites

### **1. Introduction**

Plant pectins are complex polysaccharides with an acceptable content of galacturonic acid (GalA) determined as 65% for commercial purposes like pectin from apple pomace, citrus peels, or sugar beet pulp [1, 2] with different applications based on low (<50%) and high (>50%) methoxyl pectin [3]. High- and low-methylated pectins are often applied according to their different DE, physicochemical properties, and applications; for example, the latter are used in low-calorie products like dietetic jams and jellies [2].

There are various potential sources in pectin production like agricultural wastes [1], for instance, the extracted pectin from mango peel, pomegranate peels, or sour cherry pomace through different extraction procedures and their physicochemical, structural, and functional properties of the extracted compounds have been studied in the literature [3].

Conventionally, pectin can be easily extracted through a cheap and timeconsuming acidic hot water extraction (HWE) procedure based on mineral acids like hydrochloric acid, nitric acid, and sulfuric acid [1, 2, 4] based on some factors like raw material, the type of purposed pectin, and manufacturer's instruction [1]. Then, the pectin is recovered by precipitation using ethanol with higher extraction yield. But unfortunately, mineral acids cause serious toxicity and hazardous effect toward the environment, and organic acid like citric acid can be an alternative to this problem [2].

Hence, the extracted pectin is affected by degradation in both quantity and quality aspects with the consequent huge pollutant effluent [1, 4]. It is required to investigate highly efficient and eco-friendly alternative procedures with different plant sources and experimental settings through various optimization protocols for extraction processes [1]. An eco-friendly extraction process can maximize the use of agricultural waste, minimize the volume of the remained waste, and produce the valuable compounds from the global increased agricultural waste in order to have the sustainable waste valorization and the highest utilization of food waste. For example, a large quantity of the industrially processed fruit converts into a large volume of the inevitably produced pomace. The fruit waste is usually discarded, while this valuable source of phenolics and pectin can be extracted in order to increase the financial benefits of production units and reduce the volume of fruit waste and the subsequent environmental problems [5].

These methods include pulsating hydrodynamic action, microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), and ultrasound microwave-assisted extraction (UMAE) which lead to increased extraction yield and rate, reduced process time and costs, as well as low environmental hazards aimed to obtain the desirable pectin stability and minimized pectin degradation [1, 4]. Other MAE advantages include reduced wastewater with lower use of organic solvents, increased pectin purity, improved heating rates, decreased equipment sizes, and greater control on the extraction parameters during the process [4]. Based on the cavitation effect of ultrasound waves, eco-friendly UAE methodology is based on the increased destruction of plant cell wall, better penetration, and increased rate of mass transferring with lower consumed solvents and energy [6]. The integrated ultrasonic-microwave synergistic extraction (UMSE) utilizes high energy produced in both devices and removes the defects of HWE, MAE, and UAE at an atmospheric environment with low temperature [4].

In the food industry, serious challenges for the environment are developed with massive quantities of agri-food residues and wastes, including peel, husk, seed, pomace, etc., with the loss of extractable and re-usable valuable compounds at disposal. The designed procedures can prevent the depletion of natural resources by enhancing the economic agricultural opportunities for the rural livelihoods [5].

The average annual agricultural waste is estimated as 35% in Iran with different proposed management procedures. The highest pectin content is found in premature fruits. During ripening, pectin esterase and pectinase enzymes make the pectin percentages decreased, and hence fruits gradually soften. Chemical compounds, structure, and percentage of pectin vary in various plants. Pectin plays a role in food industries as a colloidal additive, thickening/gelling agent, stabilizer, immobilizer, condenser, and emulsifier for traditional use in the production of marmalades, jams, and fruit jellies [7, 8]. According to the experimental literature, industrial pectin can be potentially extracted from the noncommercial sources of agricultural wastes from different fruits and vegetables including peach pomace, watermelon rind, pomegranate peel, papaya peel, sisal waste, pumpkin, soy hull, sunflower oilseed, lemon sour, banana peel, husk of blackberry tree branch, grapefruit peel, Akebia trifoliata husk, peanut, cocoa bean husk, grape pulp, golden kiwi, tomato, carrot, pistachio green husk, and eggplant peel/cap [2, 7].

#### *Agricultural Pectin Extraction in Iranian Experimental Settings DOI: http://dx.doi.org/10.5772/intechopen.109935*

For example, orange can play an important role in the industry and economy of Iran with producing 2.3 Mt./y in 2019. Citrus peels contain about 20–25% pectin as one of the rich sources of commercial pectin. One of the chemical pretreatments for orange wastes is dilute acid treatment with high pectin recovery in order to hydrolyze it to GalA and other sugars and dissolve the main part of hemicellulose. The valorization of orange waste is oriented on (i) direct utilization (as fertilizer and animal feed), and (ii) extraction of pectin, enzymes, and bioactive compounds with designed biorefinery systems. The relevant studies were oriented toward (a) ultrasounds and microwave treatments to obtain pectin and limonene extraction from citrus waste and (b) to cut the high price of enzyme and its long reaction time in order to eliminate the non-eco-friendly enzymatic hydrolysis [8].
