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dc.contributor.advisorBothma, C.
dc.contributor.advisorHugo, Arno
dc.contributor.advisorDe Witt, M.
dc.contributor.authorDu Toit, Liezl
dc.date.accessioned2018-09-11T07:03:33Z
dc.date.available2018-09-11T07:03:33Z
dc.date.issued2018-01
dc.identifier.urihttp://hdl.handle.net/11660/9278
dc.description.abstractEnglish: Mucilage from the cladodes of O. ficus-indica is under investigation for application in several foodstuffs. The first objective was to replace gelatin in marshmallows with different concentrations of fluid mucilage, combined with different concentrations of powdered hydrocolloids. Nine different formulations were prepared: control (100% gelatin); 75% mucilage + 25% xanthan (MX); 75% mucilage + 25% agar (MA); 75% mucilage + 25% guar (MG); 80% mucilage + 20% xanthan (8M2X); 80% mucilage + 20% agar (8M2A); 80% mucilage + 20% guar (8M2G); 75% mucilage + 12.5% xanthan + 12.5% agar (MXA); 75% mucilage + 12.5% xanthan + 12.5% guar (MXG); and 75% mucilage + 12.5% agar + 12.5% guar (MAG). Consistency, texture, tenderness of gel and shear measurements were determined, along with colour (L* values, as well as C* and Hº values) and aw. There were significant (p<0.05) differences between the different samples for all measurements. The best formulation for gelatin replacement was found to be the MXA combination, as it only differed significantly (p<0.05) from the control sample in regard to shear. It was significantly (p<0.05) less tender and resembled the shear of commercially available marshmallows in South Africa. All samples had a light, greyish yellow colour. The second aim was to compare consumer liking of flavoured and unflavoured marshmallows made with liquid mucilage, to that of a flavoured and unflavoured control sample (with 100 % gelatin), as well as a flavoured and unflavoured commercial brand. Ninety-two consumers tasted the following six samples: white commercial (Manhattan); white control (100 % gelatin); white MXA; pink commercial (Manhattan); pink control (100% gelatin); and pink MXA. The white MXA marshmallows had the lowest ranking for taste, aftertaste, texture and overall acceptability, and differed significantly (p<0.05) from all the other samples. The pink MXA marshmallow did not differ from the pink Manhattan (which had the highest rankings for taste, aftertaste, texture, and overall acceptability) and pink control marshmallows. The differences between the white and pink MXA marshmallows ranged between 2.75 and 2.89 on the nine point hedonic scale. Flavouring successfully masked the distinctive aroma of the mucilage in the marshmallows, thereby also increasing scores for texture and overall acceptability. Rapid visco analyser, differential scanning calorimetry and scanning electron microscopy studies were done on gelatin, mucilage (dry), xanthan, agar and MXA marshmallow samples, as well as individual hydrocolloid samples. Rapid visco analyser profiles showed very high viscosities for xanthan (< 15 000 cP) and mucilage (> 20 000 cP) samples, in contrast to gelatin (± 5 000 cP) and MXA (< 5 000 cP) samples. The addition of ingredients, such as sugar and egg whites, resulted in lowering of the general RVA viscosity, from ± 20 000 cP for mucilage-containing to 730 cP for MXA-containing marshmallows. Xanthan- and MXA-containing marshmallows had final viscosities of 237 cP and 727 cP, respectively, while almost no viscosity was measured for mucilage-containing marshmallows. A 100% mucilage sample showed no thermal events during DSC, indicating that no significant gelation occurred and no gel was formed. The four other samples showed very weak exothermal events, indicating that some phase change took place; in some cases gels were even formed before samples were placed in the DSC. For the hydrocolloid samples, gelatin and agar showed characteristic scaffolding on SEM micrographs, while xanthan appeared flaky. Mucilage had irregular pores, with thick walls and branching. Images showed sugar crystals suspended in the continuous phase for agar-, xanthan-, mucilage- and MXA-containing marshmallow samples; the crystals were the biggest for the mucilage-containing sample, while the MXA–containing sample also had clear zones like the gelatin-containing sample.en_ZA
dc.description.abstractAfrikaans: Slymgom uit die blaaie van Opuntia ficus-indica word bestudeer vir moontlike toepassings in verskeie voedselsoorte. Die eerste doelstelling was om gelatien in malvalekkers te vervang met verskillende konsentrasies vloeibare slymgom, in kombinasie met verskillende konsentrasies hidrokolloïedpoeiers. Nege verskillende formulasies is voorberei: kontrole (100% gelatien); 75% slym + 25% xanthan (MX); 75% slym + 25% agar (MA); 75% slym + 25% guar (MG); 80% slym + 20% xanthan (8M2X); 80% slym + 20% agar (8M2A); 80% slym + 20% guar (8M2G); 75% slym + 12.5% xanthan + 12.5% agar (MXA); 75% slym + 12.5% xanthan + 12.5% guar (MXG); en 75% slym + 12.5% agar + 12.5% guar (MAG). Konsistensie-, tekstuur-, sagtheid van gel en taaiheidsmetings is bepaal, asook kleur (L*-waardes, asook C*-en Hº- waardes) and aw. Daar was betekenisvolle (p<0.05) verskille tussen die monsters, vir al die bepalings. Die beste formulasie vir gelatien-vervanging was die MXA-kombinasie, want dit het net betekenisvol (p<0.05) verskil van die kontrole ten opsigte van taaiheid. Dit was betekenisvol (p<0.05) sagter en het ooreengestem met die taaiheid van kommersieel-beskikbare malvalekkers in Suid Afrika. Al die monsters het ‘n ligte grysgeel kleur gehad. Die tweede doelstelling was om die verbruikers se ‘hou van’ gegeurde en ongegeurde malvalekkers, wat slym bevat, te vergelyk met ‘n gegeurde en ongegeurde kontrole monster (met 100% gelatien), asook ‘n gegeurde en ongegeurde kommersiële handelsmerk. Twee-en-negentig verbruikers het die volgende ses monsters geproe: wit kommersieel (Manhattan); wit kontrole (gelatien); wit slym (75% slym + 12.5% agar + 12.5% xanthan); pienk kommersieel (Manhattan); pienk kontrole (gelatien); and pienk slym (75% slym + 12.5% agar + 12.5% xanthan). Die wit slymbevattende malvalekkers het die laagste posisie gehad vir smaak, nasmaak, tekstuur en algehele aanvaarbaarheid en het betekenisvol (p<0.05) verskil van al die ander monsters. Die pienk slym-bevattende malvalekker het nie verskil van die pienk kommersiële (wat die hoogste posisie gehad het vir smaak, nasmaak, tekstuur en algehele aanvaarbaarheid) en pienk kontrole malvalekkers nie. Die verskille tussen die wit en pienk slym-bevattende malvalekkers het gewissel van 2.75 en 2.89 op die hedoniese skaal. Geurbyvoeging het die kenmerkende reuk van die slym in die malvalekkers suksesvol gemasker en sodoende ook die posisies vir tekstuur en algehele aanvaarbaarheid verhoog. Rapid visco analyser, differential scanning calorimetry en scanning electron microscopy studies is gedoen op gelatien, slym (droog), xanthan, agar and MXA malvalekker monsters, sowel as individuele hidrokolloïed monsters. Rapid visco analyser profiele het baie hoë viskositeite vir xanthan (< 15 000 cP) en slym (> 20 000 cP) monsters gewys, in teenstelling met gelatien (± 5 000 cP) en MXA (< 5 000 cP) monsters. Die byvoeging van bestanddele, soos suiker en eierwitte, het gelei tot verlaging in algemene RVA viskositeit, van ± 20 000 cP vir die slym-bevattende tot 730 cP vir die MXA-bevattende malvalekkers. Xanthan-en MXA-bevattende malvalekkers het finale viskositeite van onderskeidelik 237 cP en 727 cP gehad, terwyl feitlik geen viskositeit gemeet is vir die slym-bevattende malvalekkers nie. ‘n 100% slym-monster het geen termiese gebeurtenis gewys tydens DSC nie, wat daarop dui dat geen betekenisvolle gelvorming plaasgevind het nie. Die ander vier monsters het baie swak eksotermiese gebeurtenisse getoon, wat ‘n aanduiding is dat veranderinge wel plaasgevind het; in sekere gevalle het gels gevorm selfs voordat die monsters in die DSC geplaas is. Vir die hidrokolloïed monsters, het gelatien en agar kenmerkende ‘stellasies’ getoon op die SEM mikrograwe, terwyl xanthan vlokkerig vertoon het. Slym het oneweredige porieë, met dik wande en vertakking. Mikrograwe het ook suikerkristalle gewys vir agar-, xanthan-, slym- en MXA-bevattende malvalekkers, wat gesuspendeer is die aaneenlopende fase. Die suikerkristalle in die slym-bevattende monster was die grootste, terwyl die MXA–bevattende monster ook gladde sones gehad het, soos die gelatien-bevattende monster.en_ZA
dc.description.sponsorshipResearch Directorate of the University of the Free Stateen_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectMucilageen_ZA
dc.subjectGel formationen_ZA
dc.subjectTextureen_ZA
dc.subjectConsumer acceptabilityen_ZA
dc.subjectRapid visco analyseren_ZA
dc.subjectDifferential scanning calorimetryen_ZA
dc.subjectScanning electron microscopyen_ZA
dc.subjectDissertation (M.Sc. (Consumer Science))--University of the Free State, 2018en_ZA
dc.titleCelling properties of cactus pear mucilage-hydrocolloid combinations in a sugar-based confectioneryen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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