Value addition of pomegranate seed oil: Effect of seed pretreatment methods on yield, quality attributes and functional properties
| dc.contributor.advisor | Opara, Umezuruike Linus | en_ZA |
| dc.contributor.advisor | Fawole, Olaniyi Amos | en_ZA |
| dc.contributor.advisor | Sigge, G. O. | en_ZA |
| dc.contributor.author | Kaseke, Tafadzwa | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science. | en_ZA |
| dc.date.accessioned | 2021-02-23T09:38:30Z | |
| dc.date.accessioned | 2021-04-22T10:11:45Z | |
| dc.date.available | 2021-12-31T03:00:08Z | |
| dc.date.issued | 2021-04 | |
| dc.description | Thesis (PhDFoodSc)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Efficient and cost-effective processing protocols which enhance oil recovery and quality are required by processors in the seed oil industries. Currently, there is no established pomegranate seed oil processing procedure in South Africa, which could be one of the reasons hindering the development of pomegranate seed oil industry, despite the readily available fruit raw material. Furthermore, cold pressing, which is the current and most preferred pomegranate seed oil extraction technique by oil processors and consumers is associated with low recovery of oil. Physical or chemical pretreatment of seeds has been demonstrated to improve oil recovery and quality in other fruit seeds and field crops; however, the application of these pretreatments to enhance pomegranate seed oil extraction efficiency and quality is limited. Therefore, the overall aim of this study was to establish a suitable pomegranate seed pretreatment method for high oil yield, quality, and functional properties. In Theme B, the effect of seed pretreatment on three common pomegranate cultivars in South Africa was examined. To evaluate if blanching as a pretreatment technique for oil extraction adds value to pomegranate seed oil (PSO), seeds of ‘Wonderful’ pomegranate fruit were blanched at 80, 90, and 100 °C for 3 and 5 min. Blanching pomegranate seeds at 90± 2 °C for 3 to 5 min significantly improved oil yield, stigmasterol, punicic acid, total phenolic content (TPC) and 2.2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging capacity. Given the significance of cultivar on seed pretreatment efficacy and oil quality, blanching (95± 2 °C for 3), microwave heating (261 W for 102 s) and enzyme pretreatment (1.7 %, 40 °C, pH=4.5 and 5 h) were investigated on the seeds of three different pomegranate cultivars (‘Wonderful’, ‘Herskawitz’, and ‘Acco’). Blanching and microwave heating of ‘Wonderful’ and ‘Acco’ seeds improved the oil yield and colour, whilst they enhanced the antioxidant capacity of oil extracted from ‘Herskawitz’ seeds. However, oil extracted from ‘Acco’ after seed enzyme pretreatment exhibited higher oil yield, total carotenoids content (TCC) and, DPPH radical scavenging capacity relative to ‘Wonderful’ and ‘Herskawitz’. The results showed that the quality of PSO from pretreated seeds is cultivar dependent. The study reported in Theme C investigated the influence of blanching (95± 2 °C/3 min) and microwave heating (261 W for 102 s) pomegranate seeds on the quality of oil extracted by cold pressing, the most preferred seed oil extraction technique by oil processors and consumers but with low oil yield. Both blanching and microwave pretreatment of seeds prior to pressing enhanced oil yield, TCC, TPC, DPPH and 2.2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity. Although the levels of oil oxidation indices were significantly higher in microwaved than blanched seeds, they remained within the limits of Codex Alimentarius Commission (CODEX STAN 19-1981) standard on cold pressed vegetable oils. The oil palmitic acid, oleic acid, and linoleic acid significantly increased after microwave heating of seeds, whilst punicic acid decreased, which could be attributed to increased heat penetration and oxidation of the fatty acid. Conversely, the fatty acid composition of PSO was not significantly altered by seed blanching, indicating that the nutritional quality of the oil was not affected. Blanching of seeds is, therefore, a valuable step that could be incorporated into the PSO production process. The studies in Theme D, focused on blanched seed storability, oxidative stability, shelf-life and functionality of PSO from blanched seed and blended oils. Blanching pomegranate seed did not cause significant deterioration of the oil quality after seed storage. More so, storing pomegranate seed at 25 and 35 °C for 6 months did not result in a considerable reduction in oil quality, with respect to peroxide value, anisidine value and total oxidation value. In paper 9, the lipid oxidation kinetics, thermodynamics parameters, and shelf-life were estimated, given the improved extractability of bioactive compounds and enhanced antioxidant capacity of PSO from pretreated seeds. The Arrhenius model and activated complex theory were applied to calculate the activation energy (Ea), enthalpy (ΔH‡), entropy (ΔS‡) and Gibbs free energy (ΔG‡), which ranged from 6.2 to 8.59 kJ mol⁻¹, 3.69 to 6.38 kJ mol⁻¹, -146.62 to -155.06 J K⁻¹ mol⁻¹ and 48.13 to 64.74 kJ mol⁻¹, respectively. These thermodynamic parameters showed that the lipid oxidation reactions in all PSO extracts were non-spontaneous, endothermic, and endergonic. Moreover, the developed Arrhenius models established that blanching seeds may increase the PSO shelf-life at 25 °C from 21 to 24 days. In contrast, microwave heating may not change the shelf-life. The higher initial level of peroxide value and increased polyunsaturated fatty acids could explain the insignificant effect of seed microwaving heating on the oil shelf-life. The study provided valuable insights useful in the design of PSO packaging, the establishment of storage conditions and application of novel technologies to preserve the storage life. In paper 10 (Theme D) the functionality and oxidative stability of PSO from unblanched and blanched seeds (95± 2 °C/ 3 min) were investigated by blending with semi-refined sunflower oil (SO) considering the detrimental health effects of synthetic antioxidants. The study showed that blended oils (85: 15 w/w) had better oxidative stability, a lower rate of antiradical activity depletion and concentration of volatile oxidation compounds than SO, although this did not significantly (p > 0.05) vary between the blended oils. Despite this, the formulation of PSO blends is a novel and desirable development for the food industry, which is currently interested in specialty oils and functional foods formulations to improve human nutrition and health. Overall, this study has established that the improvement of PSO quality through seed pretreatment is a function of cultivar. This could be ascribed to the genetic variation of the pomegranate cultivars investigated. The study has also demonstrated that seed pretreatment is essential to improve the performance of safe and green but low oil yielding technologies such as cold pressing. Blanching of pomegranate seed may enhance the oxidative stability and shelf- life of PSO. Furthermore, the study provides scientifically based information that can be used to develop strategies to improve the storability of PSO from pretreated seeds and retain the health promoting properties. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Doeltreffende en koste-effektiewe verwerkingsprotokolle wat olieherwinning en -gehalte verbeter, word deur verwerkers in die saadoliebedryf vereis. Tans, is daar nog geen gevestigde prosesseringsprosedure vir granaatpitolie in Suid-Afrika nie, wat een van die redes kan wees wat die ontwikkeling van die granaatpitolie-industrie kan belemmer, ondanks die geredelik beskikbare vrugte-grondstof. Verder, hou koue pers, wat die huidige en mees gewilde ontginningstegniek vir granaatpitolie is deur olieverwerkers en verbruikers, word verband met lae herwinning van olie. Daar is getoon dat fisiese of chemiese voorbehandeling van sade die olieherwinning en -kwaliteit in ander vrugtesade en veldgewasse verbeter; egter, die toepassing van hierdie voorbehandelings om die doeltreffendheid en kwaliteit van die ekstraksie van granaatpitteolie te verhoog, is egter beperk. Daarom was die algemene doel van hierdie studie om 'n geskikte voorbehandelingsmetod vir granaatjiesaad daar te stel vir hoë olie-opbrengs, kwaliteit en funksionele eienskappe. In Tema B, is die effek van saadvoorbehandeling op drie algemene granaatkultivars in Suid-Afrika ondersoek. Om te evalueer of blansjering as 'n voorbehandelingstegniek vir olie- ekstraksie waarde toevoeg tot granaatpitolie (PSO), is sade van 'Wonderful' granaatvrugte gedurende 3 en 5 minute by 80, 90 en 100 °C geblansjeer. Blansjering van granaatpitte by 90 ± 2 °C gedurende 3 tot 5 minute het die olie-opbrengs, stigmasterol, puniciensuur, totale fenoliese inhoud (TPC) en 2,2-difeniel-1-pikrielhidrasiel (DPPH) radikale verwyderingsvermoë aansienlik verbeter. Gegewe die belangrikheid van kultivar op die effektiwiteit van die saad en oliegehalte, blansjeer (95 ± 2 °C vir 3), mikrogolfverhitting (261 W vir 102 s) en ensiemvoorbehandeling (1,7%, 40 °C, pH = 4,5 en 5 uur) is ondersoek ingestel na die sade van drie verskillende granaatappelkultivars ('Wonderful', 'Herskawitz' en 'Acco'). Blansjering en mikrogolfverhitting van 'Wonderful' en 'Acco'-sade het die olie-opbrengs en - kleur verbeter, terwyl dit die antioksidantvermoë van olie wat uit' Herskawitz'-sade onttrek is, verbeter het. Egter, olie wat uit 'Acco' na voorbehandeling van saad-ensieme onttrek is, het egter 'n hoër olie-opbrengs, totale karotenoïedinhoud (TCC) en DPPH-radikale opvangvermoë vertoon in verhouding met 'Wonderbaar' en 'Herskawitz'. Die resultate het getoon dat die kwaliteit van PSO van voorbehandelde sade afhanklik is van die kultivar. Die studie wat in Tema C gerapporteer is, het ondersoek ingestel na die invloed van blansjering (95 ± 2 °C / 3 min) en mikrogolfverwarming (261 W vir 102 s) granaatpitte op die kwaliteit van die olie wat deur koue pers geëxtraheer is, die mees gewenste saadolie- ontginningstegniek. deur olieverwerkers en verbruikers, maar met 'n lae olieopbrengs. Beide blansjering en mikrogolfvoorbehandeling van sade voor persing verhoogde olie-opbrengs, TCC, TPC, DPPH en 2.2-azino-bis (3-etielbenzotiasolien-6-sulfonzuur) (ABTS) radikale opvangvermoë. Alhoewel die vlakke van olie-oksidasie-indekse aansienlik hoër was in mikrogolfoond as geblansjeerde sade, het dit binne die perke van die Codex Alimentarius- kommissie (CODEX STAN 19-1981) standaard op koudgeparsde plantaardige olies gebly. Die olie palmitiensuur, oliesuur en linolzuur het aansienlik toegeneem na die mikrogolfverhitting van sade, terwyl die puniciensuur afgeneem het, wat toegeskryf kan word aan die verhoogde oppervlakarea van die olie wat aan oksidasie blootgestel is as gevolg van saadmaling. Omgekeerd is die vetsuursamestelling van PSO nie beduidend deur saadblansjering verander nie, wat daarop dui dat die voedingsgehalte van die olie nie beïnvloed is nie. Blansjering van sade is dus 'n waardevolle stap wat in die PSO-produksieproses opgeneem kan word. Die studies in Tema D het gefokus op geblansjeerde saadopberging, oksidatiewe stabiliteit, rakleeftyd en funksionaliteit van PSO uit geblansjeerde saad en gemengde olies. Die blansjering van granaatpit het nie die oliegehalte na die saadopslag beduidend verswak nie. Meer so, die bewaring van granaatpitte by 25 en 35 °C vir 6 maande het nie 'n aansienlike verlaging in die oliegehalte tot gevolg gehad nie, met betrekking tot peroksiedwaarde, anisidienwaarde en totale oksidasiewaarde. In vraestel 9, is die kinetika vir lipiedoksidasie, termodinamika en rakleeftyd geskat, gegewe die verbeterde uithaalbaarheid van bioaktiewe verbindings en die verbeterde antioksidantkapasiteit van PSO uit voorbehandelde sade. Die Arrhenius-model en geaktiveerde komplekse teorie is toegepas om die aktiveringsenergie (Ea), entalpie (ΔH‡), entropie (ΔS‡) en Gibbs vrye energie (ΔG‡) te bereken, wat wissel van 6.2 tot 8.59 kJ mol⁻¹, 3.69 tot onderskeidelik 6.38 kJ mol⁻¹, -146.62 tot -155.06 J K⁻¹ mol⁻¹ en 48.13 tot 64.74 kJ mol⁻¹. Hierdie termodinamiese parameters het getoon dat die lipiedoksidasie- reaksies in alle PSO-ekstrakte nie-spontaan, endotermies en endergonies was. Boonop, het die ontwikkelde Arrhenius-modelle vasgestel dat die blansjering van sade die PSO-houdbaarheid by 25 °C van 21 tot 24 dae kan verhoog, terwyl mikrogolfverhitting nie die rakleeftyd kan verander nie. Hoër aanvanklike vlak van peroksiedwaarde en verhoogde poli-onversadigde vetsure kan die onbeduidende effek van saadmikrogolfverhitting op die olie se rakleeftyd verklaar. Die studie het waardevolle insigte verskaf wat nuttig is in die ontwerp van PSO- verpakking, die opstel van bewaaromstandighede en die toepassing van nuwe tegnologieë om die bewaringstyd te bewaar. In vraestel 10 (Tema D) is die funksionaliteit en oksidatiewe stabiliteit van PSO uit ongeblansjeerde en geblansjeerde sade (95 ± 2 °C / 3 min) ondersoek deur te meng met semi-verfynde sonneblomolie (SO), met inagneming van die nadelige gevolge vir die gesondheid van sintetiese antioksidante. Die studie het getoon dat gemengde olies (85: 15 gew / w) beter oksidatiewe stabiliteit gehad het, 'n laer tempo van uitputting van antiradikale aktiwiteit en konsentrasie van vlugtige oksidasieverbindings as SO, alhoewel dit nie beduidend (p> 0,05) verskil tussen die gemengde olies nie. Ten spyte hiervan, is die formulering van PSO-mengsels 'n nuwe en wenslike ontwikkeling vir die voedselbedryf, wat tans in spesiale olies en funksionele voedselformulasies belangstel om menslike voeding en gesondheid te verbeter. Oor die algemeen, het hierdie studie vasgestel dat die verbetering van die PSO-gehalte deur die behandeling van saad 'n funksie van kultivar is, en dit kan toegeskryf word aan die genetiese variasie van die granaatappelkultivars wat ondersoek is. Daarbenewens, het die studie getoon dat voorbehandeling van saad noodsaaklik is om die prestasie van veilige en groen, maar lae olie-opbrengstegnologieë soos koue pers, te verbeter. Blansjering van granaatpitte kan die oksidatiewe stabiliteit en rakleeftyd van PSO verhoog. Verder, bied die studie wetenskaplik gebaseerde inligting wat gebruik kan word om strategieë te ontwikkel om die opbergbaarheid van PSO van voorbehandelde sade te verbeter en die gesondheidsbevorderende eienskappe te behou. | af_ZA |
| dc.description.version | Doctoral | en_ZA |
| dc.embargo.terms | 2021-12-31 | |
| dc.format.extent | xi, 303 pages : illustrations | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/110267 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Pomegranate seed oil | en_ZA |
| dc.subject | Seed pretreatment | en_ZA |
| dc.subject | Total phenolic content | en_ZA |
| dc.subject | Antioxidant activity | en_ZA |
| dc.subject | Pomegranate -- Seeds -- Quality | en_ZA |
| dc.subject | Pomegranate seeds -- Effect of heat on | en_ZA |
| dc.subject | Pomegranate -- Effect of temperature on | en_ZA |
| dc.subject | Pomegranate -- Storage | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Value addition of pomegranate seed oil: Effect of seed pretreatment methods on yield, quality attributes and functional properties | en_ZA |
| dc.type | Thesis | en_ZA |