Pectin derived from underexploited pineapple peel biowaste
Pectin derived from underexploited pineapple peel biowaste
The current study deals with the pectin extraction from pineapple peel (PP) waste employing the ultrasound-assisted extraction (UAE) technique. Further, response surface methodology (RSM) was employed to determine the optimum conditions for maximum pectin extraction using independent variables like ultrasonication time (15–30 min), liquid to solid (LS) ratio (10–20 mL/g), temperature (50–80 ◦C) and pH (1–2). A maximum pectin yield (16.24%) was attained at 15.20 mL/g of LS ratio, 21.88 min of ultrasonication, 70.83 ◦C and pH 1.0. Other functional properties like emulsification, oil and water holding capacity were also measured. In addition, based on antinutritional and antioxidant properties, the extracted PP pectin was confirmed to be a toxic-free compound. A detailed structural and physio-chemical properties study confirmed the pectin from PP was of good quality and could be utilized as a value-added product in the pharmaceutical industry.
Materials and methods
Pineapple peel was obtained from a fruit juice shop, the ripened matured PP was manually removed, chopped into small pieces and sun-dried. Further, the peels were desiccated at 50 ◦C in a hot air drier until constant dry peel weight was obtained. Finally, the samples were powdered and sieved using an orbital sieve shaker. To avoid bacterial and fungal contamination, the samples were packed in airtight containers.
Ultrasonic-assisted extraction of pectin
The powdered PP (1 g DW) was dissolved in 20 mL DD H2O and 1N HCl was used to vary the solution pH (1–3). Pectin was extracted using an ultrasonicator (Sonics Vibra Cell VCX 130, USA) with a 2 cm tip probe. The process was operated at a pulse of 10s on and 10 s off-cycle, at 20 kHz of the ultrasonic frequency with 75% amplitude. The solution was cooled to 25 ◦C and centrifuged (REMI C-24 plus, India) for 15 min at 8000 rpm. The obtained supernatant was mixed with twice the amount of absolute ethanol and incubated overnight at ambient temperature. The colloidal mixture formed was filtered using Whatman No.1 filter paper, then the retentate was separated and washed twice with 96% ethanol. The content was then dried for 2 h at 50 ◦C.
Purification profile
The pectin extracted (30 mg) from the PP was dissolved in 2 mL of DD H2O and loaded in the DEAE cellulose column (25 × 2.4 cm). The fractions were eluted with DD H2O, followed by an increasing gradient (0.1–0.5 mol/L) of NaCl solution. The purified fractions were collected (1 mL/min flow rate). The eluted fractions were quantified and analyzed for the presence of polysaccharide components using phenol-sulfuric acid assay, TLC and GC-MS techniques, respectively.
Antinutritional properties
Antinutritional properties are biological components that can reduce the nutrient value of a bioactive compound. Therefore, antinutritional properties like oxalate, aflatoxin, phytic acid, saponin, and tannin content need to be studied for evaluating the application of pectin in the food or pharma industry.
Quantified Oxalate, Aflatoxin, phytic, saponin and tannin throught standard methods.Determined the physio-chemical properties like ash and moisture content, Degree of esterification, Total anhydrouronic acid (AUA) content, intrinsic viscosity and molecular weight and alkaloid. And also determined the Water holding capacity (WHC) and oil holding capacity (OHC), Emulsifying properties,Functional – rheological property and DPPH free-radical scavenging activity.
Conclusion
It was also found that an increase in sonication time above the optimum limit causes excessive heating, leading to structural changes and pectin disintegration. Above a pH of unity, the yield of pectin decreases, as above pH 1, structural degradation occurs via a hydrolyzing mechanism. Increases in the LS ratio above optimum level cause concentration differences between the external solvent and the inside plant cell, which results in the contents dissolving more effectively, leading to a rapid mass transfer rate and higher extraction yield. As the temperature rises above optimum level, the solubility and diffusivity of solid from plant material may increase, resulting in a decline in yield. The structure of PP pectin was further confirmed by GC-MS, FT-IR, TGA, XRD, SEM, 1D, and 2D NMR. Monosaccharide sugar groups like rhamnose, galactose, ribose, polyGalA are present in PP pectin. The purified PP pectin has a good gelling property due to its ash and moisture content. Purified PP pectin is quite stable, has a good emulsion binding capacity and antioxidant activity. In addition, PP pectin has very good gelling and non-toxic properties. It is thus concluded that the PP waste might be considered a high potential feedstock for pectin production due to its high extraction yield compared to previous studies and as the better properties of the pectin produced than other fruit waste. Also, pectin purified from PP has high methoxy content and can be used in the pharmaceutical industry.
Reference:
Shivamathi, C.S., Gunaseelan, S., Soosai, M.R., Vignesh, N.S., Varalakshmi, P., Kumar, R.S., Karthikumar, S., Kumar, R.V., Baskar, R., Rigby, S.P. and Syed, A., 2022. Process optimization and characterization of pectin derived from underexploited pineapple peel biowaste as a value-added product. Food Hydrocolloids, 123, p.107141.
