Development of processing schemes for high-value utilization of pumpkin by-products

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dc.contributor.advisorChimphango, Annie Fabian Abelen_ZA
dc.contributor.authorChifomboti, Lindah Phambalaen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Process Engineering.en_ZA
dc.date.accessioned2023-11-29T07:59:48Zen_ZA
dc.date.accessioned2024-01-08T19:18:44Zen_ZA
dc.date.available2023-11-29T07:59:48Zen_ZA
dc.date.available2024-01-08T19:18:44Zen_ZA
dc.date.issued2023-12en_ZA
dc.descriptionThesis (MEng)--Stellenbosch University, 2023.en_ZA
dc.description.abstractENGLISH ABSTRACT: Pumpkin use for production of high-value products including pre-processed cuts, has increased due to consumers’ preference for healthy lifestyles. This trend is generating substantial amounts of residues, mainly peels (rich in β-carotene and protein) and seeds (rich in oil and protein), without a proper disposal strategy. Thus, value can be added to the seeds and the peels by co-production of high-quality edible oils, β-carotene, and protein through an integrated multi-feedstock biorefinery concept. Edible oils are often recovered by cold pressing extraction (CPE) to preserve bioactive compounds. However, CPE has a low extraction efficiency (< 85%), and the edible oils produced lack oxidative stability, requiring the addition of synthetic antioxidants (β-carotene), which also serve as a pigmentation agent. Notably, vegetable oils are the preferred solvents for β-carotene extraction from plant biomass. In this study, novel processing schemes were developed and assessed for co-extraction of pumpkin seed oil (PSO) and β-carotene from pumpkin seeds and peels. Residues from the oil/β-carotene extraction (rich in protein) became feedstock for protein extraction (PE) through an enzyme (protease or viscozyme-L)-assisted hydrolysis. The objective was to increase PSO yields and oxidative stability through in-situ β-carotene extraction and enrichment, and to obtain protein as an additional high-value product in a sequential process with minimal processing steps. Microwave pre-treatment (MP) of the seeds and peels was employed to enhance PSO, βcarotene, and protein extraction. Three schemes were developed by the sequential integration of CPE and PE: (1) using microwaved seeds, (2) microwaved seed-peel mixture, and (3) untreated seed-peel mixture. Process conditions for CPE and in-situ enrichment with βcarotene (seed-to-peel ratio, 50 – 90 % w/w; microwave power, 200 – 600 Watts (𝑔. 𝑚2 103 𝑠𝑒𝑐3 ⁄ ); irradiation time, 120 – 240 sec; cold pressing pressure, 10 – 20 MPa), and PE from the press residue (liquid-to-solid ratio, 10 – 30 mL/g; enzyme dose, 1 – 3 % w/w; extraction time 2 – 5 h) were optimized for maximum yields in a three-level Box Behnken Design response surface methodology. The seed composition was ~54% crude oil and 35 % protein, and that of the peel ~11% protein and ~15 mg/ 100 g β-carotene. The CPE residues from mixed feedstock had 60.92 % protein. Microwave pre-treatment increased β-carotene, and protein extraction by 7.3-fold, and 38.65 % (protease-assisted extraction), respectively. The optimized CPE conditions were 80 % w/w seeds, 600 Watts (𝑔. 𝑚2 103 𝑠𝑒𝑐3 ⁄ ), 240 sec, and 20 MPa, providing 73.58 % recovery yield, and those of PE were 26.71 mL/g, 3 % w/w enzyme dose (viscozyme-L (5.0 pH, 55 °C)), 5 h; and 20.83 mL/g, 3 % w/w enzyme dose (protease (8.0 pH, 40 °C)), 4.24 h with 74.70% and 61.76% protein recoveries, respectively. Stellenbosch University https://scholar.sun.ac.za v PSOs extracted from the mixed feedstock were pigmented with β-carotene (~5.50 mg/ 100 g oil), and had higher oxidative stability at elevated temperatures (180 °C, 6 h) than unpigmented oils (2.01 mg/ 100 g oil), making them a suitable replacement for synthetic antioxidants in fortified-vegetable oils. Furthermore, protease (4.9 – 116.6 ± 1.18 mg/L) produced essential amino acids in higher concentrations than viscozyme-L (1.2 – 47.1 ± 2.47 mg/L). Thus, the microwave-assisted processing CPO scheme with pumpkin seed-peel mixture provides a potential multi-product pathway for obtaining maximum value from pumpkin residues.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.af_ZA
dc.description.versionMastersen_ZA
dc.format.extentxv, 132 pages : illustrationsen_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/129015en_ZA
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshPumpkin -- Processingen_ZA
dc.subject.lcshAgricultural engineeringen_ZA
dc.subject.lcshBeta caroteneen_ZA
dc.subject.lcshEnzymatic extractionen_ZA
dc.subject.lcshCold pressingen_ZA
dc.subject.lcshVegetable oil pressesen_ZA
dc.subject.lcshMicrowave pressingen_ZA
dc.subject.lcshExtraction apparatusen_ZA
dc.titleDevelopment of processing schemes for high-value utilization of pumpkin by-productsen_ZA
dc.typeThesisen_ZA
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