Use of heat treatment to improve the aroma and flavour of Cyclopia products
| dc.contributor.advisor | Joubert, Elizabeth | en_ZA |
| dc.contributor.advisor | Moelich, Erika Ilette | en_ZA |
| dc.contributor.advisor | De Beer, Dalene | en_ZA |
| dc.contributor.author | Petrus, Alicia | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science. | en_ZA |
| dc.date.accessioned | 2021-02-24T07:38:36Z | |
| dc.date.accessioned | 2021-04-22T10:12:32Z | |
| dc.date.available | 2022-04-30T03:00:11Z | |
| dc.date.issued | 2021-04 | |
| dc.description | Thesis (MScFoodSc)--Stellenbosch University, 2022. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: There is a need for efficient use of available honeybush plant material through the reduction of waste caused by processing and rejection due to poor quality resulting from production errors. In the present study, heat processing was used to convert an ultrafiltration waste stream into a food flavour ingredient. The retentate waste stream obtained from the ultrafiltration of C. genistoides extract was subjected to a range of temperature-time combinations (80°C for 2, 4, 8 and 16 h; 90°C for 2, 4, 6 and 8 h) to determine conditions for optimal aroma and flavour development when reconstituted to “cup-of-tea” strength and subjected to descriptive sensory and physicochemical analysis. An increase in heating time of the retentate increased the colour development of the beverage and the intensities of fruity and sweet attributes, while decreasing its turbidity, bitterness, astringency and the intensities of taints. Heating induced degradation of phenolic compounds, which followed first order reaction kinetics. Based on the sensory profile, the optimum heating conditions were 80°C/4 h and 90°C/4 h. Subsequent validation of these conditions on other batches of retentate (n = 10) showed that 90°C/4 h was more effective for the development of desirable fruity and sweet attributes, though degradation of phenolics was more extensive. The current high-temperature oxidation (“fermentation”) step used in the production of traditional honeybush tea is a slow process (16 h and longer), leading to poor control and product rejection due to poor quality. Ultra-high temperature oxidation (UHTO) of C. genistoides and C. subternata was investigated with the aim to shorten the processing time. Dried, green plant material, rehydrated to ca. 53% moisture content, was autoclaved at 110°C (2, 4, 6 h), 120°C (1, 2, 3 h) and 130°C (0.5, 1, 1.5 h), while conventionally prepared tea (80°C/24 h and 90°C/16 h) served as controls. The effect of UHTO on the sensory and physicochemical characteristics of the “cup-of-tea” infusions was assessed using descriptive sensory analysis and instrumental methods. UHTO increased the intensities of fruity and sweet attributes, but if the heat treatment was too severe, samples developed a “burnt caramel” taint, while samples treated for the shortest period at each temperature retained a “green” honeybush-like character. The dark-brown colour of the UHTO samples intensified with heating time. UHTO infusions were more turbid than the controls. Similar trends were observed for the two Cyclopia species, but C. genistoides needed more time to develop optimal sensory characteristics. The optimum temperature × time regimes for C. subternata and C. genistoides were 120°C/2 h and 120°C/3 h respectively. Validation of UHTO conditions was performed on other batches (n = 10) of C. subternata, with oxidation at 90°C/16 h serving as a control. Both fresh and rehydrated, dried green plant material were used to determine the effect of preservation (drying) of the plant material prior to oxidation on the quality of the beverage. Quality was assessed similarly to the optimisation experiment. Preservation had no detrimental effect on the sensory profile of the infusions and they were less turbid, while their colour was slightly lighter and less saturated. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Daar is ‘n behoefte aan doeltreffende gebruik van beskikbare heuningbosplantmaterial deur die vermindering van afval wat veroorsaak word deur verwerking en afkeur weens swak gehalte en produksiefoute. Die toepassing van hitte is in die huidige studie gebruik om ‘n ultrafiltrasie- afvalstroom om te skakel na ‘n voedselgeurbestandeel. Die retentaatafvalstroom verkry van die ultrafiltrasie van C. genistoides-ekstrak is onderwerp aan ‘n reeks temperatuur-tyd kombinasies (80°C vir 2, 4, 8 en 16 h; 90°C vir 2, 4, 6 en 8 h) om toestande te bepaal vir optimale aroma- en geurontwikkeling wanneer dit teen “koppie-tee”-sterkte opgelos is en aan beskrywende sensoriese (DSA) en fisiese-chemiese analise onderwerp is. Toepassing van die verhittingstyd van die retentaat het meer kleurontwikkeling van die drankie tot gevolg gehad en die intensiteit van vrugtige en soet eienskappe verhoog, terwyl dit die troebelheid, bitterheid, vrankheid sowel as die intensiteit van wangeure verminder het. Verhitting het afbraak van fenoliese verbindings veroorsaak, wat eerste orde reaksiekinetika gevolg het. Die optimale verhittingstoestande gebaseer op die sensoriese profiel was 80°C/4 h en 90°C/4 h. Die daaropvolgende validering van hierdie kondisies met ander retentaat lotte (n = 10) het getoon dat 90°C/4 h meer effektief is vir die ontwikkeling van die wenslike vrugtige en soet aroma eienskappe, alhoewel die afbraak van fenole meer omvangryk was. Die huidige hoëtemperatuur-oksidasiestap (“fermentasie”) wat gebruik word in die produksie van tradisionele heuningbostee, is ‘n stadige proses (16 uur en langer) wat lei tot swak beheer en verwerping van produkte as gevolg van swak gehalte. Ultra-hoë temperatuur oksidasie (UHTO) van C. genistoides en C. subternata is ondersoek met die doel om die verwerkingstyd te verkort. Gedroogde, groen plantmateriaal, gerehidreer tot ongeveer 53% voginhoud, is onder druk by 110°C (2, 4, 6 h), 120°C (1, 2, 3 h) en 130°C (0.5, 1, 1.5 h) geoksideer, terwyl tee wat volgens die gewone proses (80°C/24 h en 90°C/16 h) voorberei is as kontroles gedien het. Die effek van UHTO op die sensoriese en fisiese-chemiese eienskappe van die “koppie-tee” infusies is beoordeel deur middel van DSA en instrumentele metodes. UHTO het die intensiteit van vrugtige en soet eienskappe verhoog, maar as die hittebehandeling te intensief was, het monsters ‘n “gebrande karamel”- wangeur ontwikkel, terwyl monsters wat vir die kortste periode by elke temperatuur behandel is, ’n “groen” heuningbosagtige karakter behou het. Die donker bruin kleur van die UHTO-monsters het verdiep met verhittingstyd. UHTO-infusies was meer troebel as die kontroles. ‘n Soortgelyke tendens is waargeneem vir die twee Cyclopia spesies, maar ‘n langer verhittingstyd was nodig om die optimale sensoriese eienskappe van C. genistoides te ontwikkel. Die optimale temperatuur × tyd kondisies vir C. subternata en C. genistoides was onderskeidelik 120°C/2 h en 120°C/3 h. Validering van 120°C/2 h is op ander C. subternata- lotte (n = 10) uitgevoer, met oksidasie by 90°C/16 h as ‘n kontrole. Beide vars en gedroogde plantmateriaal wat gerehidreer is, is gebruik om die effek van preservering d.m.v. droging van die vars plantmateriaal voor oksidasie op die kwaliteit van die ‘koppie-tee’-infusie te bepaal. Kwaliteit is soos vir die optimiseringseksperiment beoordeel. Preservering d.m.v. droging het geen nadelige uitwerking op die infusies se sensoriese profiel gehad nie, en het tot minder troebelheid asook ‘n ligter en minder versadigde kleur gelei. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.embargo.terms | 2022-04-01 | |
| dc.format.extent | x, 167 pages : illustrations (some color), maps | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/110286 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Cyclopia products | en_ZA |
| dc.subject | Honeybush tea -- Effect of high temperatures on | en_ZA |
| dc.subject | Ultra high temperature oxidation (UHTO) | en_ZA |
| dc.subject | Retentate | en_ZA |
| dc.subject | Sensory profile | en_ZA |
| dc.subject | Cyclopia -- Effect of heat on | en_ZA |
| dc.subject | Honeybush (Cyclopia spp.) -- Therapeutic use | en_ZA |
| dc.subject | Honeybush tea -- Flavor and odor | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Use of heat treatment to improve the aroma and flavour of Cyclopia products | en_ZA |
| dc.type | Thesis | en_ZA |