Thesis (MScFoodSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: In light of the limited and inconsistent supply of good quality honeybush tea, a species-specific sensory profile and the physicochemical characteristics of Cyclopia intermedia (honeybush) tea were determined to ultimately establish the optimum fermentation parameters for this herbal tea on laboratory-scale and to validate these findings on commercial-scale. The characteristic sensory profile of C. intermedia can be described as sweet tasting and slightly astringent with a combination of “fynbos-floral”, “fynbos-sweet”, “fruity” (specifically “apricot jam”, “cooked apple”, “raisin” and “lemon/lemon grass”), “woody”, “caramel/ vanilla” and “honey-like” aromas. The flavour can be described as distinctly “fynbos-floral”, “fynbos-sweet” and “woody”, including hints of “lemon/lemon grass” and “hay/dried grass”. The results of the sensory study were used to create a C. intermedia sensory wheel and lexicon, and an elementary grading system that categorised samples into “good”, “average” and “poor” sensory quality was proposed. Physicochemical parameters, i.e. soluble solids (SS) content, absorbance as a measure of colour, and turbidity, were evaluated as possible rapid predictors of sensory quality. High SS content, absorbance and turbidity correlated strongly with “poor” sensory quality. A linear relationship existed between the physicochemical parameters. The effect of fermentation temperature (70, 80 and 90°C) and time (12, 16, 24, 36, 48 and 60 h) on the sensory and physicochemical characteristics of C. intermedia was determined on laboratory-scale. Increasing fermentation time increased the intensity of positive sensory attributes, while decreasing the intensity of negative sensory attributes. The SS content, colour and turbidity of infusions decreased with increasing fermentation time, while the SS content and turbidity of infusions increased with increasing fermentation temperature. Fermentation at 90°C for 36 h on laboratory-scale produced C. intermedia with the best sensory properties, while preserving the SS content and colour of infusions. Fermentation at 70°C and 80°C required longer fermentation times for development of positive sensory attributes. Fermentation at 90°C was subsequently validated on commercial-scale. Laboratory-scale fermentation of the same batches of plant material was also carried out concurrently to allow direct comparison of the scale of fermentation on tea quality. Commercial-scale fermentation, despite increased variability as a result of increased batch volumes and heating difficulties, produced C. intermedia of “good” sensory quality after 24 and 36 h of fermentation. Increasing fermentation time had little effect on the SS content and colour of infusions of tea produced on commercial-scale, but turbidity increased significantly after 36 h. Thus, to produce C. intermedia with consistently good quality on commercial-scale, fermentation at 90°C for 24 to 36 h is recommended. Increasing fermentation time past 48 h should be avoided to prevent turbidity and the development of sensory attributes characteristic of over-fermented tea. However, due to the large variability of commercial-scale honeybush tea production, it is recommended that each batch be monitored between 24 and 36 h to determine when optimum fermentation has been obtained. / AFRIKAANSE OPSOMMING: Beperkte en wisselvallige beskikbaarheid van goeie gehalte heuningbostee noodsaak die optimisering van fermentasie parameters vir Cyclopia intermedia. Optimisering van fermentation parameters is op laboratorium skaal gedoen, gevolg deur validasie van die parameters op kommersiële skaal. Vooraf is die spesie-spesifieke sensoriese profiel en die fisies-chemiese eienskappe van C. intermedia tee bepaal. Die kenmerkende sensoriese profiel van C. intermedia kan beskryf word as soet en effens vrank met 'n kombinasie van "fynbos-blomagtige", "fynbos-soet", "vrugtige" (spesifiek "appelkooskonfyt", "gekookte appel", "rosyntjie” en “suurlemoen/sitroen gras"), "houtagtige", "karamel/vanilla" en "heuningagtige" aromas. Die smaak kan beskryf word as "fynbos-blomagtig", "fynbos-soet" en "houtagtig", met 'n tikkie "suurlemoen/sitroen gras" en "hooi/gedroogde gras". Die resultate van die sensoriese studie is gebruik om 'n C. intermedia sensoriese wiel en leksikon, asook 'n basiese graderingstelsel wat tee monsters in "goeie", "gemiddelde" en "swak" sensoriese kwaliteit klassifiseer, te ontwikkel. Fisies-chemiese parameters: oplosbare vastestof (SS) inhoud; absorbansie as 'n maatstaf van kleur; en troebelheid, is geëvalueer as moontlike indikasies van sensoriese kwaliteit. Hoë SS inhoud, absorbansie en troebelheid waardes het sterk met "swak" sensoriese kwaliteit gekorreleer. 'n Lineêre verwantskap bestaan tussen die fisies-chemiese parameters en kwaliteit. Die effek van fermentasie temperatuur (70, 80 en 90°C) en -tyd (12, 16, 24, 36, 48 en 60 h) op die sensoriese en fisies-chemiese eienskappe van C. intermedia is op laboratorium skaal bepaal. Verlenging van fermentasie tyd het die intensiteit van die positiewe sensoriese eienskappe verhoog, terwyl dit die intensiteit van negatiewe sensoriese eienskappe verminder het. Die SS inhoud, kleur en troebelheid van die tee het met verlengde fermentasie tyd afgeneem, terwyl die SS inhoud en troebelheid met verhoging van fermentasie temperatuur toegeneem het. Fermentasie by 90°C vir 36 h op laboratorium skaal het tee met die beste sensoriese eienskappe geproduseer, met behoud van die SS inhoud en kleur. Fermentasie by 70°C en 80°C het 'n langer fermentasie tyd vir die ontwikkeling van positiewe sensoriese eienskappe vereis. Fermentasie by 90°C is daaropvolgens op kommersiële skaal uitgevoer, met gelyktydige laboratorium skaal fermentasie van dieselfde plantmateriaal lotte om die direkte effek van die skaal van fermentasie op tee kwaliteit te bepaal. Kommersiële fermentasie, ten spyte van verhoogde wisselvalligheid as gevolg van groot volumes tee en probleme met verhitting, het tee van "goeie" sensoriese kwaliteit na fermentasie periodes van 24 en 36 h geproduseer. Verlenging van fermentasie tyd het min uitwerking op die SS inhoud en kleur van kommersiel gefermenteerde tea gehad, maar troebelheid het beduidend na 36 h toegeneem. Fermentasie by 90°C vir 24 - 36 h word gevolglik aanbeveel om tee met goeie gehalte op kommersiële skaal te produseer. Fermentasie vir langer as 48 h moet vermy word om troebelheid te voorkom en die ontwikkeling van sensoriese eienskappe kenmerkend van oor-gefermenteerde tee te vermy. As gevolg van faktore wat groot variasie in kommersiële skaal heuningbostee produksie kan teweegbring, word aanbeveel dat elke produksielot tussen 24 en 36 h gemonitor word om die optimum fermentasie tyd te bepaal.

Thesis (MSc Food Sc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Application of steam treatment to green Cyclopia maculata and C. longifolia to modulate their aroma and flavour profile, without detrimental effects on colour and individual phenolic content, was investigated. Steam treatment (96 °C, atmospheric pressure) of different time periods was applied to the shredded, fresh plant material before drying (STBD; 0, 30, 60, 90 and 120 s) or the herbal tea product after drying (STAD; 0, 1, 2, 3, and 4 min). Steam treatment of 60 s or longer resulted in a significant (p < 0.05) decrease in vegetative (‘green grass’ and ‘hay/dried grass’) and cereal (‘oats/porridge/grains’) aroma and flavour intensities, with an increase in some fruity (‘tropical fruit’ and ‘guava’) and ‘fruity-sweet' aroma intensities. These changes manifested to a greater degree for plant material subjected to STBD, while they were less prominent for C. longifolia compared to C. maculata. Additionally, 19 aroma compounds were instrumentally identified in the volatile fraction of C. maculata infusions prepared from STBD plant material. Of these, seven correlated well with green honeybush vegetative and cereal aroma attributes associated with unsteamed samples. Steaming thus resulted in the rapid loss of some of these highly volatile ‘green’-associated aroma compounds. Steam treatment of more than 60 s, regardless of STBD or STAD, was not detrimental to green colour, and individual phenolic content was not greatly affected. The 30 s STBD treatment of C. maculata, however, led to the rapid loss of green colour and oxidation of phenolic compounds, without considerable aroma improvement. This highlights the need for process control during green honeybush production. Storage stability of steamed (60 s, STBD) and unsteamed green C. maculata was investigated under low (0 °C; moisture impermeable packaging) and normal (25 °C at 60% relative humidity (RH); semi-moisture-permeable sachets) temperature storage conditions (LTS and NTS, respectively) over 6 months and high temperature storage (HTS) conditions (40 °C at 75% RH; semimoisture- permeable sachets) for 1 month. HTS conditions, after 1 month, seemed to emulate changes occurring over 6 months at NTS conditions, with little change detected at LTS conditions. Despite noticeable green colour loss over the respective storage periods at NTS and HTS conditions, individual phenolic compounds were not severely affected. NTS and HTS led to the progressive development of sought-after fermented honeybush sensory attributes, especially in unsteamed samples. These include prominent fruity (‘stewed fruit’, ‘apricot jam’ and ‘marmalade’) aromas and flavours, ‘general sweet’ and ‘fruity-sweet’ aromas and a sweeter taste. The collated descriptive sensory data were used to generate a preliminary sensory wheel for green honeybush aroma, and another for flavour, taste and mouthfeel. The sensory profile of green honeybush was finally described as a dominant vegetative aroma and flavour, prominent sweetassociated and slightly fruity aroma, with sweet and notably bitter tastes and an astringent mouthfeel. By combining the sensory data, it was clear that the major effects of storage outweighed those of steam treatments, suggesting that storage of 3 to 6 months may improve sensory quality, although colour may be slightly compromised. Immediate sensory manipulation and thus improvement, however, may be achieved to a lesser degree in the short term by STBD. / AFRIKAANSE OPSOMMING: Die toepassing van stoombehandeling van groen Cyclopia maculata en C. longifolia vir die modulasie van hul aroma en geur profiel, sonder gepaardgaande nadelige gevolge op kleur en individuele fenoliese inhoud, is ondersoek. Stoombehandeling (96 °C, atmosferiese druk) van verskeie tydstippe is toegepas op die gekerfde, vars plantmateriaal voor droging (SBVD; 0, 30, 60, 90 en 120 s) of die groen teeproduk ná droging (SBND; 0, 1, 2, 3 en 4 min). Stoombehandeling van 60 s of langer het tot 'n betekenisvolle (p < 0.05) afname in vegetatiewe (‘groen gras’ en ‘hooi/gedroogde gras’) en graan (‘hawer/pap/graan’) aroma en geur intensiteite gelei, met 'n toename in sommige vrugtige (‘tropiese vrugte’ en ‘koejawel’) en ‘vrugtige-soet’ aroma intensiteite. Hierdie veranderinge was meer merkbaar in die SBVD behandeling, terwyl C. longifolia minder vatbaar vir hierdie veranderinge was as C. maculata. Daarbenewens is 19 aromaverbindings in die vlugtige fraksie van C. maculata aftreksel voorberei van SBVD plantmateriaal instrumenteel geïdentifiseer. Sewe hiervan het goed gekorreleer met heuningbos vegetatiewe en graan aromas wat verband hou met ongestoomde monsters. Stoombehandeling het dus gelei tot die vinnige verlies van sommige van hierdie baie vlugtige ‘groen’-geassosieërde aromaverbindings. Stoombehandeling vir langer as 60 s, ongeag van SBVD of SBND, het nie die groen kleur en individuele fenoliese inhoud grootliks nadelig beïnvloed nie. ‘n SBVD behandeling van 30 s het egter tot die vinnige verlies van groen kleur en oksidasie van fenoliese verbindings, sonder aansienlike aroma verbetering van C. maculata gelei. Dít beklemtoon die noodsaaklikheid vir prosesbeheer tydens groen heuningbosproduksie. Stabiliteit van gestoomde (60 s, SBVD) en ongestoomde groen C. maculata tydens opberging onder lae (0 °C; vog-ondeurlaatbare verpakking) en normale (25 °C by 60% relatiewe humiditeit (RH); semi-vogdeurlaatbare sakkies) temperatuur opbergingtoestande (LTO en NTO, onderskeidelik) oor 6 maande en hoë temperatuur opbergingtoestande (40 °C by 75% RH; semivogdeurlaatbare sakkies; HTO) vir 1 maand, is ondersoek. HTO het na 1 maand soortgelyke veranderinge teweeggebring as NTO na 6 maande, terwyl min verandering by LTO bespeur is. Ten spyte van merkbare groen kleur verlies oor die onderskeie tydperke by NTO en HTO is individuele fenoliese verbindings min beinvloed. NTO en HTO het gelei tot die progresiewe ontwikkeling van gesogte sensoriese eienskappe van gefermenteerde heuningbos, veral in ongestoomde monsters. Dit sluit in prominente vrugtige (‘gestoofde vrugte’, ‘appelkooskonfyt’ en ‘marmelade’) aromas en geure , ‘algemene soet’ en ‘vrugtige-soet’ aromas en 'n soeter smaak. Al die beskrywende sensoriese data is saamgestel om 'n voorlopige sensoriese wiel vir groen heuningbos aroma op te stel, asook een vir geur, smaak en mondgevoel. Die sensoriese profiel van groen heuningbos kan beskryf word as 'n oorheersende vegetatiewe aroma en geur, prominente soet-verwante en effens vrugtige aroma, met soet en veral bitter smaak en ‘n vrank mondgevoel. Deur die sensoriese data te kombineer kon duidelik uitgewys word dat die belangrikste gevolge van opberging dié van stoombehandeling oortref. Dit dui daarop dat opberging van 3 tot 6 maande sensoriese kwaliteit kan verbeter, hoewel kleur effens benadeel kan word. In die kort termyn kan onmiddellike sensoriese manipulasie en dus verbetering egter in 'n mindere mate deur SBVD bereik word.