Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
Honeybush tea quality: Effect of water source and evaluation of NIR hyperspectral imaging as a tool to predict quality
Thesis (MScFoodSc)--Stellenbosch University, 2022.
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | en_ZA |
| Published: |
Stellenbosch : Stellenbosch University
2022
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867614064807510016 |
|---|---|
| access_status_str | Open Access |
| author | Van Schoor, Helene Mijas |
| author2 | Moelich, Erika Ilette |
| author_browse | Moelich, Erika Ilette Van Schoor, Helene Mijas |
| author_facet | Moelich, Erika Ilette Van Schoor, Helene Mijas |
| author_sort | Van Schoor, Helene Mijas |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MScFoodSc)--Stellenbosch University, 2022. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/125065 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:46:06.004Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/125065 Honeybush tea quality: Effect of water source and evaluation of NIR hyperspectral imaging as a tool to predict quality Van Schoor, Helene Mijas Moelich, Erika Ilette Joubert, Elizabeth De Beer, Dalene Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science. Honeybush tea -- Quality NIR hyperspectral imaging Water quality Cyclopia -- Sensory evaluation Fermentation Honeybush tea -- Biotechnology Thesis (MScFoodSc)--Stellenbosch University, 2022. ENGLISH ABSTRACT: Regulation of honeybush tea quality for supply to the local and export markets is essential to ensure the continual success of this indigenous South African product. Therefore, the present study investigated the use of near infrared hyperspectral imaging (NIR-HSI) to predict quality, based on the quality grading system, as well as the potential negative effect of poor water quality on honeybush tea. NIR-HSI was investigated as a tool to predict the quality grades (High, Moderate, Low and Poor) of honeybush tea, using a comprehensive sample set (n = 522), which consisted of C. intermedia, C. subternata and C. genistoides samples. The descriptive sensory analysis (DSA) and colour data of the infusions were used to calculate a grade for each sample, by mapping the data to the quality grading scorecard, developed for the assessment of honeybush tea. The validity of the mapping process was tested by performing sensory analysis on a subset of the samples (n = 59). It was concluded that the mapping process could correctly classify High and Poor grade samples. The NIR- HSI spectra of the samples were used to firstly differentiate between species and secondly between quality grades. Partial least squares discriminant analysis (PLS-DA) and soft independent modelling of class analogies (SIMCA) models were developed to classify the samples based on the previously mentioned criteria. The use of NIR-HSI in combination with chemometrics could successfully classify the Cyclopia species, but not the quality grades. This was due to low concentrations of aroma and flavour compounds, which causes changes in the quality of honeybush tea infusions, are unlikely to be detected by NIR-HSI. The effect of brewing water (n = 6) on the final honeybush infusion quality was also investigated. The waters, which differed in pH and mineral composition, were used to prepare infusions of C. intermedia (n = 6), C. subternata (n = 6) and C. genistoides (n = 6). The infusions were characterised in terms of their sensory profiles, determined by DSA, and their physicochemical properties, namely CIEL*a*b* colour values, turbidity, soluble solids (SS) and phenolic content. Brewing water with a high pH (> 8) caused the presence of a new aroma and palate attribute namely ‘date pudding’ in the infusions. These infusions were also visually darker in colour, due to lower L* and higher a* and b* values, and lower concentrations of some of the major phenolic compounds. Brewing water with a high electrical conductivity resulted in infusions with new palate attributes namely salty taste and thick mouthfeel and the infusions were darker in colour, due to high turbidity and SS values. Infusions prepared with the above-mentioned waters also had lower intensities of the characteristic honeybush attributes. Water used to brew a cup of honeybush tea should ideally have a slightly acidic or neutral pH and low electrical conductivity to produce infusions with the characteristic sensory profile and the dark red-brown colour associated with a good quality product. AFRIKAANSE OPSOMMING: Die regulering van heuningbosteekwaliteit vir die voorsiening aan die plaaslike en uitvoermarkte is noodsaaklik om die voortdurende sukses van hierdie inheemse Suid-Afrikaanse produk te verseker. Die huidige studie het die gebruik van naby-infrarooi hiperspektrale beeld analise (NIR-HSI) ondersoek om kwaliteit, gebaseer op die kwaliteitgraderingstelsel, te voorspel, asook die potensiële negatiewe effek van swak watergehalte op heuningbostee. NIR-HSI is ondersoek as 'n instrument om die kwaliteits grade (Hoog, Matig, Laag en Swak) van heuningbostee te voorspel. 'n Omvattende datastel (n = 522), wat bestaan het uit monsters vir Cyclopia. intermedia, C. subternata en C. genistoides is gebruik. Die beskrywende sensoriese analise (DSA) en kleurdata van die tee-infusies is gebruik om 'n graad vir elke monster te bereken, deur die data te karteer na die kwaliteitgradering telkaart, wat ontwikkel was vir die assessering van heuningbostee. Die geldigheid van die karteringsproses is getoets deur sensoriese analise op ʼn verkleinde groep geselekteerde monsters (n = 59). Die karteringsproses het monsters wat as Hoog en Swak gradeer is, korrek geklassifiseer. Die NIR-HSI spektra van die monsters is gebruik om eerstens tussen spesies te onderskei en tweedens tussen kwaliteit grade. Gedeeltelike kleinste kwadrate diskriminant analise (PLS-DA) en “soft independent modelling of class analogies” (SIMCA) modelle is ontwikkel om die monsters te klassifiseer gebaseer op die voorheen genoemde kriteria. Die gebruik van NIR-HSI in kombinasie met chemometrie kan die Cyclopia spesie suksesvol klassifiseer, maar nie die kwaliteit grade nie. Die lae konsentrasies aroma- en geurverbindings, wat veranderinge in die kwaliteit van heuningbostee-infusies veroorsaak, sal waarskynlik nie deur NIR-HSI waargeneem kan word nie. Die effek van die kwaliteit van water (n = 6)33 op die finale heuningbosinfusiekwaliteit is verder ondersoek. Water monsters, wat verskil het in pH en mineraalsamestelling, is gebruik om infusies van C. intermedia (n = 6), C. subternata (n = 6) en C. genistoides (n = 6) voor te berei. Die infusies is beskryf in terme van sensoriese profiel, bepaal deur DSA, en fisies-chemiese eienskappe, naamlik CIEL*a*b* kleurwaardes, troebelheid, oplosbare vastestowwe (SS) en fenoliese inhoud. 'n Nuwe aroma en smaak eienskap, naamlik 'dadelpoeding' is waargeneem in infusies berei van water met 'n hoë pH (> 8). Hierdie infusies was ook visueel donkerder van kleur, as gevolg van laer L* en hoër a* en b* waardes, en laer konsentrasies van sommige van die belangrikste fenoliese verbindings. Tee berei met water met 'n hoë elektriese geleidingsvermoë het gelei tot infusies met ‘n sout smaak en ‘n dik mondgevoel en die aftreksels was donkerder van kleur as gevolg van hoë troebelheid en SS waardes. Aftreksels wat met bogenoemde waters berei is, het ook laer intensiteite van die kenmerkende heuningbos- eienskappe gehad. Water wat gebruik word om 'n koppie heuningbostee te berei, moet ideaal 'n effens suur of neutrale pH en lae elektriese geleidingsvermoë hê om infusies te berei met die kenmerkende sensoriese profiel en die donker rooi-bruin kleur wat met 'n goeie kwaliteit produk geassosieer word. Masters 2022-03-01T07:29:32Z 2022-04-29T12:52:28Z 2023-03-18T03:00:13Z 2022-03 Thesis http://hdl.handle.net/10019.1/125065 en_ZA Stellenbosch University xi, 191 pages : illustrations (some color) application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Honeybush tea -- Quality NIR hyperspectral imaging Water quality Cyclopia -- Sensory evaluation Fermentation Honeybush tea -- Biotechnology Van Schoor, Helene Mijas Honeybush tea quality: Effect of water source and evaluation of NIR hyperspectral imaging as a tool to predict quality |
| title | Honeybush tea quality: Effect of water source and evaluation of NIR hyperspectral imaging as a tool to predict quality |
| title_full | Honeybush tea quality: Effect of water source and evaluation of NIR hyperspectral imaging as a tool to predict quality |
| title_fullStr | Honeybush tea quality: Effect of water source and evaluation of NIR hyperspectral imaging as a tool to predict quality |
| title_full_unstemmed | Honeybush tea quality: Effect of water source and evaluation of NIR hyperspectral imaging as a tool to predict quality |
| title_short | Honeybush tea quality: Effect of water source and evaluation of NIR hyperspectral imaging as a tool to predict quality |
| title_sort | honeybush tea quality effect of water source and evaluation of nir hyperspectral imaging as a tool to predict quality |
| topic | Honeybush tea -- Quality NIR hyperspectral imaging Water quality Cyclopia -- Sensory evaluation Fermentation Honeybush tea -- Biotechnology |
| url | http://hdl.handle.net/10019.1/125065 |
| work_keys_str_mv | AT vanschoorhelenemijas honeybushteaqualityeffectofwatersourceandevaluationofnirhyperspectralimagingasatooltopredictquality |