Comprehensive valorization of citrus (Kinnow Mandarin) peel through sequential microwave assisted solvent extraction of bioactive compounds and pectin for their application in food
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Date
2019-02
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Extraction of valuable products of bioactive compounds, pectin, essential oils, fibers etc. from agro industrial waste is a promising and an effective solution in resolving the problem of wastes but in contrary, current extraction techniques possess several inadequacies in terms of economy, energy and longer time requirements. Citrus fruits, after juice processing, is a major fruit that results in large quantities of wastes (peel) rich in various bioactive compounds such as pectins, bioactive compounds and essential oils. An effective, non-toxic and profitable extraction strategy could significantly promote the valorization of citrus peel and provide high quality extracted products with increased profits Present research deals with the comprehensive valorization of Citrus peel (Kinnow Mandarin) through sequential microwave assisted solvent extraction of bioactive compounds and pectin for their applications in food. Final study was conducted into three phases. In the first phase, four independent variables having five levels of each Microwave power (160, 320,480,640,800), microwave time (1, 2, 3, 4, 5), solvent (Ethanol) volume and particle size (citrus peel powder) (0.2, 0.4, 0.6, 0.8, 1.0) were selected for extraction of bioactive compounds. In the second phase for the extraction of pectin from citrus peel powder residue, Microwave power (160, 320,480,640,800), microwave time (1, 2, 3, 4, 5), solvent (citric acid solution) volume (100, 150, 200, 250, 300) and pH (1.0, 1.5, 2.0, 2.5, 3.0) were selected as Independent variables. The citrus peel residue remaining after the pectin extraction was also collected and utilized for the development of Activated Carbon. Optimization of both the processes was done based on their respective responses following Response surface methodology using Design Expert 10.0.1 software. Statistical and graphical analysis was done in both phases. In the third phase of the study, the citrus peel extract and pectin were utilized in food. The citrus peel extract, being a source of bioactive compounds, was used as an antioxidant in the flaxseed oil to check the storage stability of Flaxseed oil during 60 days of storage period. Pectin extracted from the citrus peel residue was utilized as the gelling/stabilizing agent in the preparation of mixed fruit Jam and was chemically analyzed. Results showed that the microwave assisted extraction proved very effective approach for the extraction of bioactive compounds as maximum extract yield and pectin from the citrus peel powder residue was obtained. The optimum result of Extraction of bioactive compounds was obtained when the Microwave Power was 480.173 W, Microwave Time 3.127 min, Solvent volume 103.458ml and Particle size 0.543 mm with the responses having Extract yield 30.743%, Total phenolic content 88.404 mg GAE/g, Total Flavonoid content 69.887 mg CE/g, DPPH Antioxidant activity 86.056%, ABTS Antioxidant activity 86.173%, Total carotenoids 49.533 mg BET/g and Vitamin C content 119.712 mg AA/g). On the other hand the optimized result of extraction of pectin was found when the Microwave Power was 476.58 W, Microwave Time 2.59 min, Solvent volume 155.41 ml and pH 1.05. The responses were Pectin yield 27.58%, Equivalent Weight 767.83 mg, Methoxyl Content 7.23%, Anhydrouronic Acid Content 60.42% and Degree of Esterification 64.679%. Studies also revealed that use of citrus peel extract (200 – 1000 ppm) could increase the shelf life of flaxseed oil up to 60 days and pectin extracted from citrus peel residue could be used for the jam preparation. GC-MS and SEM analysis also supported the results of extraction.
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