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Dr. Dalene De Beer
Plant Bioactives Group, Post-Harvest & Agro-Processing Technologies, Agricultural Research Council, Stellenbosch, South Africa Department of Food Science, Stellenbosch University, Stellenbosch, South Africa

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Journal article
Published: 30 August 2021 in Molecules
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Green rooibos extract (GRE), shown to improve hyperglycemia and HDL/LDL blood cholesterol, has potential as a nutraceutical beverage ingredient. The main bioactive compound of the extract is aspalathin, a C-glucosyl dihydrochalcone. The study aimed to determine the effect of common iced tea ingredients (citric acid, ascorbic acid, and xylitol) on the stability of GRE, microencapsulated with inulin for production of a powdered beverage. The stability of the powder mixtures stored in semi-permeable (5 months) and impermeable (12 months) single-serve packaging at 30 °C and 40 °C/65% relative humidity was assessed. More pronounced clumping and darkening of the powders, in combination with higher first order reaction rate constants for dihydrochalcone degradation, indicated the negative effect of higher storage temperature and an increase in moisture content when stored in the semi-permeable packaging. These changes were further increased by the addition of crystalline ingredients, especially citric acid monohydrate. The sensory profile of the powders (reconstituted to beverage strength iced tea solutions) changed with storage from a predominant green-vegetal aroma to a fruity-sweet aroma, especially when stored at 40 °C/65% RH in the semi-permeable packaging. The change in the sensory profile of the powder mixtures could be attributed to a decrease in volatile compounds such as 2-hexenal, (Z)-2-heptenal, (E)-2-octenal, (E)-2-nonenal, (E,Z)-2,6-nonadienal and (E)-2-decenal associated with “green-like” aromas, rather than an increase in fruity and sweet aroma-impact compounds. Green rooibos extract powders would require storage at temperatures ≤ 30 °C and protection against moisture uptake to be chemically and physically shelf-stable and maintain their sensory profiles.

ACS Style

Chantelle Human; Dalene de Beer; Magdalena Muller; Marieta van der Rijst; Marique Aucamp; Andreas Tredoux; André de Villiers; Elizabeth Joubert. Shelf-Life Stability of Ready-to-Use Green Rooibos Iced Tea Powder—Assessment of Physical, Chemical, and Sensory Properties. Molecules 2021, 26, 5260 .

AMA Style

Chantelle Human, Dalene de Beer, Magdalena Muller, Marieta van der Rijst, Marique Aucamp, Andreas Tredoux, André de Villiers, Elizabeth Joubert. Shelf-Life Stability of Ready-to-Use Green Rooibos Iced Tea Powder—Assessment of Physical, Chemical, and Sensory Properties. Molecules. 2021; 26 (17):5260.

Chicago/Turabian Style

Chantelle Human; Dalene de Beer; Magdalena Muller; Marieta van der Rijst; Marique Aucamp; Andreas Tredoux; André de Villiers; Elizabeth Joubert. 2021. "Shelf-Life Stability of Ready-to-Use Green Rooibos Iced Tea Powder—Assessment of Physical, Chemical, and Sensory Properties." Molecules 26, no. 17: 5260.

Research article
Published: 27 July 2021 in Journal of the Science of Food and Agriculture
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BACKGROUND Ultrafiltration of green honeybush (Cyclopia genistoides) extract results in a by-product (retentate). Application of further separation processes for recovery of polyphenols would entail creation of additional waste. Repurposing the retentate as a food flavour ingredient provides an alternative valorisation approach. RESULTS The retentate, suspended in water (270 g L−1), was heat-treated at 80 °C for 2, 4, 8 and 16 h, and at 90 °C for 2, 4, 6 and 8 h to change its sensory profile. The heat-treated retentate, diluted to beverage strength (2.15 g L−1), had prominent ‘grape/Muscat-like’ and ‘marmalade/citrus’ aroma and flavour notes. Overall, heating for ≤4 h increased the intensities of positive flavour and aroma notes, while reducing that of ‘green/grass’, ‘hay’ and bitterness, whereafter further heating only had a slight effect on the aroma profile at 80 °C (P < 0.05), but not at 90 °C (P ≥ 0.05). The heat treatments, 80 °C/4 h and 90 °C/4 h, were subsequently applied to different batches of retentate (n = 10) to accommodate the effect of natural product variation. Heating at 90 °C produced higher intensities of positive aroma attributes (P < 0.05), but was more detrimental to the phenolic stability, compared to 80 °C. CONCLUSION After heat treatment, the phenolic content of C. genistoides retentate, reconstituted to beverage strength, still fell within the range of a typical fermented honeybush leaf tea infusion. The change in phenolic composition will not diminish the benefit of an improved sensory profile for the retentate by-product through heating.

ACS Style

Neil Miller; Alicia Petrus; Erika Ilette Moelich; Magdalena Muller; Dalene de Beer; Marieta van der Rijst; Elizabeth Joubert. Heat treatment improves the sensory properties of the ultrafiltration by‐product of honeybush ( Cyclopia genistoides ) extract. Journal of the Science of Food and Agriculture 2021, 1 .

AMA Style

Neil Miller, Alicia Petrus, Erika Ilette Moelich, Magdalena Muller, Dalene de Beer, Marieta van der Rijst, Elizabeth Joubert. Heat treatment improves the sensory properties of the ultrafiltration by‐product of honeybush ( Cyclopia genistoides ) extract. Journal of the Science of Food and Agriculture. 2021; ():1.

Chicago/Turabian Style

Neil Miller; Alicia Petrus; Erika Ilette Moelich; Magdalena Muller; Dalene de Beer; Marieta van der Rijst; Elizabeth Joubert. 2021. "Heat treatment improves the sensory properties of the ultrafiltration by‐product of honeybush ( Cyclopia genistoides ) extract." Journal of the Science of Food and Agriculture , no. : 1.

Journal article
Published: 24 July 2021 in Journal of Food Composition and Analysis
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Low-chill requiring (LCR) apple cultivars provide the South African apple juice industry the opportunity to mitigate the effects of climate change on production. The juicing potential (yield and physicochemical properties) of six LCR and two pink-fleshed (PF) apple cultivars, harvested in 2018, were compared to that of commercial cultivars. In 2019, the phenolic and sensory profiles of the juice of the three most promising LCR cultivars were also compared to that of the two PF and commercial cultivars. LCR and PF cultivars had similar or lower juice yields and juice with lower sugar content than the commercial cultivars. LCR cultivars produced juice containing less polyphenols than PF cultivars (p < 0.05), but similar or higher amounts than commercial cultivars. Of the PF cultivars, KAZ 95−91 juice was higher in p-coumaroylquinic acid, flavan-3-ols and procyanidins, and TC3 juice had the higher chlorogenic acid concentration (p < 0.05), but similar flavonol and anthocyanin concentrations. The ‘litchi/pear’ and ‘strawberry’ aroma notes of Afri Glo (LCR) and TC3, respectively, could offer the consumer apple juice with new aroma profiles. The less sweet juice of LCR and PF cultivars could furthermore cater for health-conscious consumers.

ACS Style

J. Hermine Stander; Magdalena Muller; Elizabeth Joubert; Iwan F. Labuschagné; Dalene De Beer. Potential of low-chill requiring and pink-fleshed apple cultivars for cloudy juice production. Journal of Food Composition and Analysis 2021, 103, 104089 .

AMA Style

J. Hermine Stander, Magdalena Muller, Elizabeth Joubert, Iwan F. Labuschagné, Dalene De Beer. Potential of low-chill requiring and pink-fleshed apple cultivars for cloudy juice production. Journal of Food Composition and Analysis. 2021; 103 ():104089.

Chicago/Turabian Style

J. Hermine Stander; Magdalena Muller; Elizabeth Joubert; Iwan F. Labuschagné; Dalene De Beer. 2021. "Potential of low-chill requiring and pink-fleshed apple cultivars for cloudy juice production." Journal of Food Composition and Analysis 103, no. : 104089.

Journal article
Published: 16 June 2021 in Journal of Food Composition and Analysis
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The elemental analysis of tea is essential since it is a commonly consumed beverage around the world. In this paper, non-destructive energy dispersive X-ray fluorescence spectrometry (EDXRF) using a standardless method based on fundamental parameters was applied in honeybush and rooibos analysis. Tea samples were measured directly in the form of loose powders. The observed element concentrations (mg kg−1) were as follows: Ca (1260–3990), Cl (914–7710), K (2270–7190), Mg (374–2510), S (474–1320), P (183−1210), Si (303−1580), Al (92–765), Fe (67–514), Mn (26–163), Cr (1.8–20), Cu (2.2–11.5), Ni (1.1–5), Rb (0.8–8), Sr (5.4–24.5), Ti (4.1–39), and Zn (4.2–18.6). What is more, the determined concentrations (mg kg−1) of selected elements in rooibos and honeybush, are statistically different: Cl (2200–7710 rooibos and 913.7–2160 honeybush); Mg (1232–3465 rooibos and 535.9–1030 honeybush); P (388.0–1566 rooibos and 244.0–403.6 honeybush); Br (12.1–52.8 rooibos and 1.6–5.3 honeybush). Multivariate analysis of variance (ANOVA) was successfully applied to the data, showing statistical significance of the concentration differences for all the elements in both types of tea. The developed method provided good precision (RSD < 6%) with an accuracy of more than 90 %, and LOD ∼ 0.5 mg kg-1- for trace elements. The method was validated using suitable certified reference materials of tea (CRM).

ACS Style

Beata Zawisza; Marcin Musielak; Dalene de Beer; Elizabeth Joubert; Beata Walczak. Non-destructive elemental analysis of herbal teas from South Africa. Journal of Food Composition and Analysis 2021, 102, 104041 .

AMA Style

Beata Zawisza, Marcin Musielak, Dalene de Beer, Elizabeth Joubert, Beata Walczak. Non-destructive elemental analysis of herbal teas from South Africa. Journal of Food Composition and Analysis. 2021; 102 ():104041.

Chicago/Turabian Style

Beata Zawisza; Marcin Musielak; Dalene de Beer; Elizabeth Joubert; Beata Walczak. 2021. "Non-destructive elemental analysis of herbal teas from South Africa." Journal of Food Composition and Analysis 102, no. : 104041.

Journal article
Published: 21 November 2020 in LWT
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Honeybush tea infusions, especially those prepared from Cyclopia genistoides, can be unacceptably bitter, given the association of this herbal tea with sweet taste. Infusions prepared from both ‘fermented’ (high-temperature oxidised) Cyclopia longifolia and C. genistoides contain high levels of the bitter xanthone, mangiferin, however, C. longifolia is generally less bitter than C. genistoides. The effect of phenolic changes during fermentation on the bitterness of infusions was determined for both species. The bitter intensity of the infusions was reduced by 34-68% for C. genistoides and 55-86% for C. longifolia. Fermentation affected the phenolic composition of the two species differently, notably the ratio of mangiferin to isomangiferin remained higher for C. genistoides. Bitterness prediction models for two data sets (126 fermented and green infusions; 122 fermented infusions) including variable selection based on phenolic content gave good performance (RMSECV < 5). Nine compounds, depending on the data set, were determined to be important for the models, including xanthones, benzophenones, flavones and flavanones. Mangiferin, two tetrahydroxyxanthone-di-O,C-hexose isomers, 3-β-D-glucopyranosyliriflophenone, vicenin-2 and scolymoside were common to both models. Future application of the model would be to screen large numbers of genotypes for the breeding of selections with low bitterness potential based on phenolic composition.

ACS Style

Lara Alexander; Erika Ilette Moelich; Dalene de Beer; Magdalena Muller; Beata Walczak; Elizabeth Joubert. High-temperature oxidation reduces the bitterness of honeybush infusions depending on changes in phenolic composition. LWT 2020, 139, 110608 .

AMA Style

Lara Alexander, Erika Ilette Moelich, Dalene de Beer, Magdalena Muller, Beata Walczak, Elizabeth Joubert. High-temperature oxidation reduces the bitterness of honeybush infusions depending on changes in phenolic composition. LWT. 2020; 139 ():110608.

Chicago/Turabian Style

Lara Alexander; Erika Ilette Moelich; Dalene de Beer; Magdalena Muller; Beata Walczak; Elizabeth Joubert. 2020. "High-temperature oxidation reduces the bitterness of honeybush infusions depending on changes in phenolic composition." LWT 139, no. : 110608.

Journal article
Published: 19 November 2020 in Food Control
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Rooibos (Aspalathus linearis) and honeybush (Cyclopia species) are popular indigenous herbal teas originating from South Africa. Both are enjoyed for their taste and aroma and more importantly, valued for their medicinal properties such as antioxidant, anti-diabetic, anti-inflammatory or immunomodulatory activity. In the European Union, rooibos and honeybush are protected as Geographical Indications. The Geographical Indication refers to products with unique characteristics that are related to their geographical origin. The authentication of products labelled as GIs is regarded as an issue of food quality and safety. Routine quality control procedures of GIs products prevent their fraud and counterfeiting on the market. However, techniques to determine adulteration or mislabelling of rooibos and honeybush do not exist yet. Therefore, in this study, the authentication of rooibos and honeybush based on their elemental composition was investigated. The methodology presented in this study combines energy-dispersive X-ray fluorescence spectrometry (EDXRF) for elemental analysis and a one-class classification approach. Elemental composition of plant material highly depends on soil on which the plant has been grown, but also on some other factors such as, e.g., atmospheric pollution, or plant metabolism. Determination of the elemental composition of the samples by EDXRF is non-destructive and does not require any complex sample preparation. One-class classification methods are well suited for authentication and origin verification problems. Based on the EDXRF data of samples from studied teas, individual class models were constructed for rooibos and honeybush. Several linear and nonlinear classification techniques were tested in order to find the model that handles the authentication task the best. For honeybush tea, the best classification results were obtained with the use of a nonlinear method based on Potential Functions. For rooibos tea, the highest classification outcomes were obtained by nonlinear One Class Partial Least Squares (OC-PLS) and the machine learning technique, Support Vector Domain Description (SVDD). The methodology implemented in the present study has the potential to be successfully applied for routine authentication of honeybush and rooibos teas.

ACS Style

Zuzanna Małyjurek; Beata Zawisza; Dalene de Beer; Elizabeth Joubert; Beata Walczak. Authentication of honeybush and rooibos herbal teas based on their elemental composition. Food Control 2020, 123, 107757 .

AMA Style

Zuzanna Małyjurek, Beata Zawisza, Dalene de Beer, Elizabeth Joubert, Beata Walczak. Authentication of honeybush and rooibos herbal teas based on their elemental composition. Food Control. 2020; 123 ():107757.

Chicago/Turabian Style

Zuzanna Małyjurek; Beata Zawisza; Dalene de Beer; Elizabeth Joubert; Beata Walczak. 2020. "Authentication of honeybush and rooibos herbal teas based on their elemental composition." Food Control 123, no. : 107757.

Research article
Published: 17 August 2020 in Phytochemical Analysis
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Introduction The minor phenolic constituents of Cyclopia pubescens Eckl. & Zeyh. are unknown and one dimensional (1D) liquid chromatography (LC) is unable to provide sufficient separation. Methodology A two‐dimensional (2D) LC method incorporating normal‐phasehigh performance countercurrent chromatography (NP‐HPCCC) in the first dimension (1D) and reversed‐phase ultra‐high‐performance liquid chromatography (RP‐UHPLC) as the second dimension (2D) was developed. The analytical HPCCC method was subsequently scaled up to semi‐preparative mode and fractions pooled based on phenolic sub‐groups. The phenolic compounds in selected fractions were subsequently isolated using RP‐HPLC on a C18 column. Isolated compounds were identified by nuclear magnetic resonance (NMR) spectroscopy. The absolute configurations of compounds were determined by optical rotation and electronic circular dichroism spectra. Sugars were identified by gas chromatography‐mass spectrometry (GC–MS) analysis. Results The comprehensive off‐line 2D CCC × LC method gave a good spread of the phenolic compounds. Orthogonality calculated using both the convex hull and conditional entropy methods were 81%. High‐resolution mass spectrometric fragmentation spectra obtained from a quadrupole‐time‐of‐flight instrument and ultraviolet‐visible (UV‐vis) spectral data were used to (tentatively) identify 32 phenolic compounds from the analytical CCC fractions. Of the seven isolated compounds, (2S)‐5‐O‐[α‐l‐rhamnopyranosyl‐(1 → 2)‐β‐d‐glucopyranosyl]eriodictyol (3) and (2S)‐5‐O‐[α‐l‐rhamnopyranosyl‐(1 → 2)‐β‐d‐glucopyranosyl]‐5,7,3′,4′‐tetrahydroxyflavan (4) were newly identified in all plants. The other isolated compounds were identified as (2S)‐5‐O‐[α‐l‐rhamnopyranosyl‐(1 → 2)‐β‐d‐glucopyranosyl]naringenin (1), R‐neo‐eriocitrin (2), 3‐O‐α‐l‐arabinopyranosyl‐3,4‐dihydroxybenzoic acid (5), 4‐O‐β‐d‐glucopyranosyl‐Z‐4‐hydroxycinnamic acid (6) and 4‐(4′‐O‐β‐d‐glucopyranosyl‐4′‐hydroxy‐3′‐methoxyphenyl)‐2‐butanone (7). Conclusions Among the 32 compounds (tentatively) identified, only six were previously identified in Cyclopia pubescens using 1D LC. Most of the isolated compounds were also identified for the first time in Cyclopia spp., improving the knowledge of the minor phenolic compounds of this genus.

ACS Style

Nico A. Walters; Dalene De Beer; André De Villiers; Ombeline Danton; Matthias Hamburger; Elizabeth Joubert. Comprehensive off‐line CCC × LC‐DAD‐MS separation of Cyclopia pubescens Eckl. & Zeyh. phenolic compounds and structural elucidation of isolated compounds. Phytochemical Analysis 2020, 1 .

AMA Style

Nico A. Walters, Dalene De Beer, André De Villiers, Ombeline Danton, Matthias Hamburger, Elizabeth Joubert. Comprehensive off‐line CCC × LC‐DAD‐MS separation of Cyclopia pubescens Eckl. & Zeyh. phenolic compounds and structural elucidation of isolated compounds. Phytochemical Analysis. 2020; ():1.

Chicago/Turabian Style

Nico A. Walters; Dalene De Beer; André De Villiers; Ombeline Danton; Matthias Hamburger; Elizabeth Joubert. 2020. "Comprehensive off‐line CCC × LC‐DAD‐MS separation of Cyclopia pubescens Eckl. & Zeyh. phenolic compounds and structural elucidation of isolated compounds." Phytochemical Analysis , no. : 1.

Research article
Published: 07 August 2020 in Oxidative Medicine and Cellular Longevity
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Mitochondrial dysfunction plays a major role not only in the pathogenesis of many oxidative stress or age-related diseases such as neurodegenerative as well as mental disorders but also in normal aging. There is evidence that oxidative stress and mitochondrial dysfunction are the most upstream and common events in the pathomechanisms of neurodegeneration. Cyclopia species are endemic South African plants and some have a long tradition of use as herbal tea, known as honeybush tea. Extracts of the tea are gaining more scientific attention due to their phenolic composition. In the present study, we tested not only the in vitro mitochondria-enhancing properties of honeybush extracts under physiological conditions but also their ameliorative properties under oxidative stress situations. Hot water and ethanolic extracts of C. subternata, C. genistoides, and C. longifolia were investigated. Pretreatment of human neuroblastoma SH-SY5Y cells with honeybush extracts, at a concentration range of 0.1-1 ng/ml, had a beneficial effect on bioenergetics as it increased ATP production, respiration, and mitochondrial membrane potential (MMP) after 24 hours under physiological conditions. The aqueous extracts of C. subternata and C. genistoides, in particular, showed a protective effect by rescuing the bioenergetic and mitochondrial deficits under oxidative stress conditions (400 μM H2O2 for 3 hours). These findings indicate that honeybush extracts could constitute candidates for the prevention of oxidative stress with an impact on aging processes and age-related neurodegenerative disorders potentially leading to the development of a condition-specific nutraceutical.

ACS Style

Anastasia Agapouda; Veronika Butterweck; Matthias Hamburger; Dalene De Beer; Elizabeth Joubert; Anne Eckert. Honeybush Extracts (Cyclopia spp.) Rescue Mitochondrial Functions and Bioenergetics against Oxidative Injury. Oxidative Medicine and Cellular Longevity 2020, 2020, 1 -14.

AMA Style

Anastasia Agapouda, Veronika Butterweck, Matthias Hamburger, Dalene De Beer, Elizabeth Joubert, Anne Eckert. Honeybush Extracts (Cyclopia spp.) Rescue Mitochondrial Functions and Bioenergetics against Oxidative Injury. Oxidative Medicine and Cellular Longevity. 2020; 2020 ():1-14.

Chicago/Turabian Style

Anastasia Agapouda; Veronika Butterweck; Matthias Hamburger; Dalene De Beer; Elizabeth Joubert; Anne Eckert. 2020. "Honeybush Extracts (Cyclopia spp.) Rescue Mitochondrial Functions and Bioenergetics against Oxidative Injury." Oxidative Medicine and Cellular Longevity 2020, no. : 1-14.

Research article
Published: 11 April 2020 in SN Applied Sciences
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Bone, skin and soft tissue chronic wounds emanating from burns or bacterial infections which persist due to prolonged tissue inflammation contribute to a delay in wound healing. Electrospun biomimetic scaffolds produced from biodegradable polymers have proven to be a better alternative due to their large surface area to volume ratio and ability to release the drug directly to the wound surface allowing fast and sustained absorbance over the affected wound area. In this study, poly lactic acid (PLA) (20% w/v) and collagen-based (PLA/C) fibrous scaffolds (electrospun at a voltage of 22 kV, flow rate of 0.1 mL/min) containing varying concentrations of silver sulphadiazine (1% w/w, 0.75% w/w) (Ag+S) and Aspalathus linearis (AL) fermented extract (0.025%, 0.1% and 0.5% w/w), were designed and fabricated to increase antimicrobial penetration and cellular biocompatibility. The elastic modulus of samples revealed that incorporating 1% Ag+S and A. linearis extract to PLA solution culminates in a fiber with the superlative stiffness of 2.1.1 GPa. The antimicrobial effect of the scaffolds was evaluated against S. aureus, P. aeruginosa, MRSA and E. coli. PLA/C–Ag+S/AL scaffolds and showed antibacterial activity against both gram +ve and gram −ve bacteria. They were nontoxic to the cells and provided favorable substrates for the neonatal epidermal keratinocytes cells to undergo cell attachment and proliferation. PLA/C–Ag+S/AL scaffolds have a great potential for use in chronic wounds as well as in tissue and bioengineering applications.

ACS Style

Margaret O. Ilomuanya; Adannaya C. Adebona; Weiguang Wang; Abimbola Sowemimo; Chioma L. Eziegbo; Boladale O. Silva; Samson O. Adeosun; Elizabeth Joubert; Dalene De Beer. Development and characterization of collagen-based electrospun scaffolds containing silver sulphadiazine and Aspalathus linearis extract for potential wound healing applications. SN Applied Sciences 2020, 2, 1 -13.

AMA Style

Margaret O. Ilomuanya, Adannaya C. Adebona, Weiguang Wang, Abimbola Sowemimo, Chioma L. Eziegbo, Boladale O. Silva, Samson O. Adeosun, Elizabeth Joubert, Dalene De Beer. Development and characterization of collagen-based electrospun scaffolds containing silver sulphadiazine and Aspalathus linearis extract for potential wound healing applications. SN Applied Sciences. 2020; 2 (5):1-13.

Chicago/Turabian Style

Margaret O. Ilomuanya; Adannaya C. Adebona; Weiguang Wang; Abimbola Sowemimo; Chioma L. Eziegbo; Boladale O. Silva; Samson O. Adeosun; Elizabeth Joubert; Dalene De Beer. 2020. "Development and characterization of collagen-based electrospun scaffolds containing silver sulphadiazine and Aspalathus linearis extract for potential wound healing applications." SN Applied Sciences 2, no. 5: 1-13.

Paper
Published: 09 March 2020 in Food & Function
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Evolution program-PLS models based on 12 compounds in green rooibos extract predicted extract bio-capacity related to anti-diabetic effects.

ACS Style

Amsha Viraragavan; Nokulunga Hlengwa; Dalene de Beer; Sylvia Riedel; Neil Miller; Sandra Bowles; Beata Walczak; Christo J Muller; Elizabeth Joubert. Model development for predicting in vitro bio-capacity of green rooibos extract based on composition for application as screening tool in quality control. Food & Function 2020, 11, 3084 -3094.

AMA Style

Amsha Viraragavan, Nokulunga Hlengwa, Dalene de Beer, Sylvia Riedel, Neil Miller, Sandra Bowles, Beata Walczak, Christo J Muller, Elizabeth Joubert. Model development for predicting in vitro bio-capacity of green rooibos extract based on composition for application as screening tool in quality control. Food & Function. 2020; 11 (4):3084-3094.

Chicago/Turabian Style

Amsha Viraragavan; Nokulunga Hlengwa; Dalene de Beer; Sylvia Riedel; Neil Miller; Sandra Bowles; Beata Walczak; Christo J Muller; Elizabeth Joubert. 2020. "Model development for predicting in vitro bio-capacity of green rooibos extract based on composition for application as screening tool in quality control." Food & Function 11, no. 4: 3084-3094.

Journal article
Published: 21 October 2019 in Antioxidants
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Consumption of rooibos (Aspalathus linearis) as herbal tea is growing in popularity worldwide and its health-promoting attributes are mainly ascribed to its phenolic composition, which may be affected by the brewing conditions used. An aspect so far overlooked is the impact of cold brewing vs regular brewing and microwave boiling on the (poly) phenolic profile and in vitro antioxidant capacity of infusions prepared from red (‘fermented’, oxidized) and green (‘unfermented’, unoxidized) rooibos, the purpose of the present study. By using an untargeted metabolomics-based approach (UHPLC-QTOF mass spectrometry), 187 phenolic compounds were putatively annotated in both rooibos types, with flavonoids, tyrosols, and phenolic acids the most represented type of phenolic classes. Multivariate statistics (OPLS-DA) highlighted the phenolic classes most affected by the brewing conditions. Similar antioxidant capacities (ORAC and ABTS assays) were observed between cold- and regular-brewed green rooibos and boiled-brewed red rooibos. However, boiling green and red rooibos delivered infusions with the highest antioxidant capacities and total polyphenol content. The polyphenol content strongly correlated with the in vitro antioxidant capacities, especially for flavonoids and phenolic acids. These results contribute to a better understanding of the impact of the preparation method on the potential health benefits of rooibos tea.

ACS Style

Elisabetta Damiani; Patricia Carloni; Gabriele Rocchetti; Biancamaria Senizza; Luca Tiano; Elizabeth Joubert; Dalene De Beer; Luigi Lucini. Impact of Cold versus Hot Brewing on the Phenolic Profile and Antioxidant Capacity of Rooibos (Aspalathus linearis) Herbal Tea. Antioxidants 2019, 8, 499 .

AMA Style

Elisabetta Damiani, Patricia Carloni, Gabriele Rocchetti, Biancamaria Senizza, Luca Tiano, Elizabeth Joubert, Dalene De Beer, Luigi Lucini. Impact of Cold versus Hot Brewing on the Phenolic Profile and Antioxidant Capacity of Rooibos (Aspalathus linearis) Herbal Tea. Antioxidants. 2019; 8 (10):499.

Chicago/Turabian Style

Elisabetta Damiani; Patricia Carloni; Gabriele Rocchetti; Biancamaria Senizza; Luca Tiano; Elizabeth Joubert; Dalene De Beer; Luigi Lucini. 2019. "Impact of Cold versus Hot Brewing on the Phenolic Profile and Antioxidant Capacity of Rooibos (Aspalathus linearis) Herbal Tea." Antioxidants 8, no. 10: 499.

Journal article
Published: 08 October 2019 in Food Research International
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The honeybush sensory wheel was revised, using a large sample set (n = 585) comprising of the major commercial Cyclopia species, i.e. C. intermedia, C. subternata and C. genistoides. Only positive and negative aroma attributes were included in the wheel. Chemicals were identified to serve as reference standards for the honeybush (Cyclopia spp.) lexicon. Similarly, chemical-based reference standards were identified for the rooibos (Aspalathus linearis) lexicon. From a comprehensive literature search and gas chromatography–mass spectrometry analyses, chemicals were screened by an expert panel for their suitability in terms of typicality of the target aroma. Each chemical was evaluated in a ‘base tea’ and compared to a specific ‘reference tea’ exhibiting a high intensity of the target aroma. A total of 30 and 44 chemicals for rooibos and honeybush, respectively, were selected for validation by a trained panel. Descriptive sensory analysis was conducted to assign typicality and intensity scores for each chemical representing a target aroma attribute. Several chemicals were identified as suitable reference standards for the following aroma notes: isophorone (‘rooibos-woody’), maltyl isobutyrate (‘caramel’), cis-3-hexenol (‘green grass’), 4-oxoisophorone (‘seaweed’) and 2,4,6-trichloroanisole (‘musty/mouldy’) for rooibos; and 2-acetyl-5-methylfuran (‘woody’), levulinic acid (‘fynbos-sweet’), maltyl isobutyrate (‘caramel’), and 2-acetylpyrrole (‘nutty’) for honeybush.

ACS Style

B.V.P. du Preez; D. de Beer; E.I. Moelich; M. Muller; E. Joubert. Development of chemical-based reference standards for rooibos and honeybush aroma lexicons. Food Research International 2019, 127, 108734 .

AMA Style

B.V.P. du Preez, D. de Beer, E.I. Moelich, M. Muller, E. Joubert. Development of chemical-based reference standards for rooibos and honeybush aroma lexicons. Food Research International. 2019; 127 ():108734.

Chicago/Turabian Style

B.V.P. du Preez; D. de Beer; E.I. Moelich; M. Muller; E. Joubert. 2019. "Development of chemical-based reference standards for rooibos and honeybush aroma lexicons." Food Research International 127, no. : 108734.

Journal article
Published: 17 September 2019 in LWT
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Green rooibos extract containing high levels of aspalathin, a dihydrochalcone antioxidant, and the carrier chitosan, both an antioxidant and antimicrobial agent, was used to produce a dual-purpose food ingredient powder by spray-drying for incorporation into processed meat products. Green rooibos extract was shown to inhibit growth of Escherichia coli, Staphylococcus aureus and Listeria monocytogenes, adding to the functionality of such a powder. Three formulations (50, 100 and 150 g chitosan/kg powder) were compared to the pure spray-dried extract and maltodextrin-containing powders (250 and 500 g maltodextrin/kg powder) in terms of physicochemical properties (particle size and morphology, moisture sorption isotherms, compatibility, bulk density and compressibility) and aspalathin stability during accelerated storage. All the formulations produced amorphous, hygroscopic powders with deliquescence at relative humidity (RH) > 65%. The moisture content of the powders was lower than their monolayer moisture content calculated using the BET and GAB models. Isothermal microcalorimetry showed no interaction between extract and carbohydrate polymers. Aspalathin degradation in the powders, subjected to accelerated stability testing (40 °C/75% RH for 96 h), followed fractional conversion kinetics. The presence of chitosan in the powders decreased the stability of aspalathin during storage compared to the pure extract and maltodextrin-containing powders.

ACS Style

Chantelle Human; Dalene de Beer; Marique Aucamp; Isa J. Marx; Christiaan J. Malherbe; Marinda Viljoen-Bloom; Marieta van der Rijst; Elizabeth Joubert. Preparation of rooibos extract-chitosan microparticles: Physicochemical characterisation and stability of aspalathin during accelerated storage. LWT 2019, 117, 108653 .

AMA Style

Chantelle Human, Dalene de Beer, Marique Aucamp, Isa J. Marx, Christiaan J. Malherbe, Marinda Viljoen-Bloom, Marieta van der Rijst, Elizabeth Joubert. Preparation of rooibos extract-chitosan microparticles: Physicochemical characterisation and stability of aspalathin during accelerated storage. LWT. 2019; 117 ():108653.

Chicago/Turabian Style

Chantelle Human; Dalene de Beer; Marique Aucamp; Isa J. Marx; Christiaan J. Malherbe; Marinda Viljoen-Bloom; Marieta van der Rijst; Elizabeth Joubert. 2019. "Preparation of rooibos extract-chitosan microparticles: Physicochemical characterisation and stability of aspalathin during accelerated storage." LWT 117, no. : 108653.

Journal article
Published: 24 June 2019 in Food Research International
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Variation in the bitter taste of Cyclopia genistoides (honeybush) herbal tea and reported modulation between its major xanthones, mangiferin and isomangiferin, prompted further investigation into the potential modulatory effects of honeybush phenolics. Combinations of crude benzophenone (BF)-, xanthone (XF)-, and flavanone (FF)-rich fractions and their major individual phenolic compounds were analysed by descriptive sensory analysis. The fractions were prepared from a bitter, hot water extract of green C. genistoides. Fraction BF, which is below the bitter threshold (intensity 10 on 100-point scale), enhanced the bitter intensity of XF and FF slightly (p < 0.05), although none of the major individual benzophenones retained this bitter enhancing effect. On the contrary, 3-β-d-glucopyranosyl-4-β-d-glucopyranosyloxyiriflophenone, the major benzophenone in BF, significantly (p < 0.05) decreased the bitter taste of XF, at a low concentration, whereas FF suppressed the bitter intensity of XF and mangiferin, the major xanthone present in XF. Hesperidin, however, had no effect on the bitter intensity of XF. In contrast, (2S)-5-[α-L-rhamnopyranosyl-(1→2)-β-d-glucopyranosyloxy]-naringenin, the major compound of FF, significantly (p < 0.05) enhanced the bitter taste of XF when added at concentrations comparable to that of 'fermented' honeybush tea infusions. The concentration-dependence of these bitter taste interactions may be responsible for the variable bitter intensity of C. genistoides herbal tea.

ACS Style

Lara Alexander; Dalene De Beer; Magdalena Muller; Marieta Van Der Rijst; Elizabeth Joubert. Potential of benzophenones and flavanones to modulate the bitter intensity of Cyclopia genistoides herbal tea. Food Research International 2019, 125, 108519 .

AMA Style

Lara Alexander, Dalene De Beer, Magdalena Muller, Marieta Van Der Rijst, Elizabeth Joubert. Potential of benzophenones and flavanones to modulate the bitter intensity of Cyclopia genistoides herbal tea. Food Research International. 2019; 125 ():108519.

Chicago/Turabian Style

Lara Alexander; Dalene De Beer; Magdalena Muller; Marieta Van Der Rijst; Elizabeth Joubert. 2019. "Potential of benzophenones and flavanones to modulate the bitter intensity of Cyclopia genistoides herbal tea." Food Research International 125, no. : 108519.

Journal article
Published: 12 April 2019 in Food Chemistry
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Ultrafiltration of Cyclopia genistoides extract was optimised to increase its benzophenone and xanthone content as quantified using HPLC-DAD. Regenerated cellulose (RC) and polyethersulphone membranes with molecular weight cut-offs of 10 and 30 kDa were evaluated in terms of compound enrichment, permeate flux and permeate yield, using dead-end ultrafiltration. Compound enrichment was subsequently optimised using the 10 kDa RC membrane and tangential flow ultrafiltration (TFU). The effect of extract composition on compound enrichment, due to natural variation in the source material, was assessed using extracts from different batches of plant material (n = 11). Transmembrane pressure and feed flow rate affected (p < 0.05) process efficiency (mean permeate flux, compound enrichment and membrane fouling). TFU achieved ≥ 20% enrichment of the target compounds, proving its suitability for preparation of a nutraceutical extract of C. genistoides.

ACS Style

Neil Miller; Stephanie C. Bosman; Christiaan J. Malherbe; Dalene De Beer; Elizabeth Joubert. Membrane selection and optimisation of tangential flow ultrafiltration of Cyclopia genistoides extract for benzophenone and xanthone enrichment. Food Chemistry 2019, 292, 121 -128.

AMA Style

Neil Miller, Stephanie C. Bosman, Christiaan J. Malherbe, Dalene De Beer, Elizabeth Joubert. Membrane selection and optimisation of tangential flow ultrafiltration of Cyclopia genistoides extract for benzophenone and xanthone enrichment. Food Chemistry. 2019; 292 ():121-128.

Chicago/Turabian Style

Neil Miller; Stephanie C. Bosman; Christiaan J. Malherbe; Dalene De Beer; Elizabeth Joubert. 2019. "Membrane selection and optimisation of tangential flow ultrafiltration of Cyclopia genistoides extract for benzophenone and xanthone enrichment." Food Chemistry 292, no. : 121-128.

Journal article
Published: 19 March 2019 in Food Research International
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Phenolic compounds of Aspalathus linearis (rooibos) are susceptible to oxidation during “fermentation”, a process characterized by the formation of a red-brown leaf color. The role of enzymes in this process is not yet understood. An experiment with dried green rooibos plant material pre-treated at 170 °C for 30 min to denature and “inactivate” endogenous enzymes was conducted to confirm the role of oxidative enzymes. The phenolic composition of “enzyme inactivated” plant material was not significantly (p ≥ .05) affected by simulated fermentation, compared to control samples, as determined using piece-wise multivariate analysis of variance for successive time intervals. This proves that rooibos enzymes participate in the oxidation of phenolic compounds during fermentation of the plant material. A kinetic modeling approach was subsequently used to establish reaction kinetic parameters for selected rooibos phenolic compounds. The degradation of aspalathin and nothofagin and formation of eriodictyol glucosides during simulated fermentation at four temperatures from 37 to 50 °C were best described by the fractional conversion model based on first-order kinetics (r2 > 0.98), which allows for non-zero equilibrium concentrations. The extent of degradation for other compounds was too low to enable kinetic modeling. Reaction rates for the degradation/formation of phenolic compounds during fermentation followed the Arrhenius law. Less phenolic degradation (higher equilibrium concentration), but a higher reaction rate constant, was observed at higher temperatures, which could possibly be attributed to inactivation of enzymes.

ACS Style

Dalene De Beer; Jade Tobin; Beata Walczak; Marieta Van Der Rijst; Elizabeth Joubert. Phenolic composition of rooibos changes during simulated fermentation: Effect of endogenous enzymes and fermentation temperature on reaction kinetics. Food Research International 2019, 121, 185 -196.

AMA Style

Dalene De Beer, Jade Tobin, Beata Walczak, Marieta Van Der Rijst, Elizabeth Joubert. Phenolic composition of rooibos changes during simulated fermentation: Effect of endogenous enzymes and fermentation temperature on reaction kinetics. Food Research International. 2019; 121 ():185-196.

Chicago/Turabian Style

Dalene De Beer; Jade Tobin; Beata Walczak; Marieta Van Der Rijst; Elizabeth Joubert. 2019. "Phenolic composition of rooibos changes during simulated fermentation: Effect of endogenous enzymes and fermentation temperature on reaction kinetics." Food Research International 121, no. : 185-196.

Journal article
Published: 14 February 2019 in Journal of Food Composition and Analysis
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Increasing demand for honeybush tea (Cyclopia spp.) and the need for industry expansion have created interest in non-utilised species such as Cyclopia pubescens Eckl. & Zeyh. Very limited information is available on the phenolic composition of this species. A reversed phase core-shell biphenyl column was used to develop and validate a quantitative HPLC diode-array detection method for separation of the major phenolic compounds in C. pubescens. Eight phenolic compounds were identified and a further six tentatively identified by comparison of retention time, UV-Vis and high resolution mass spectrometric characteristics with those of authentic reference standards and literature, respectively. Genotypic variation in the phenolic composition of C. pubescens was determined by analysing the leaves and stems of seedlings (n = 17) in a field gene bank. The xanthone and benzophenone present in the highest levels in the leaves were mangiferin and 3-β-D-glucopyranosyl-4-β-D-glucopyranosyloxyiriflophenone, respectively. The leaves contained higher quantities of all compounds, except hesperidin, the major compound in the stems, and a second hesperetin glycoside. Statistical analysis included hierarchical clustering to determine the degree of dissimilarity between genotypes, which provided valuable information for future breeding programs. Comparison of the dendrograms for leaves and stems indicated different clustering patterns for genotypes.

ACS Style

Nico A. Walters; Dalene De Beer; André De Villiers; Beata Walczak; Elizabeth Joubert. Genotypic variation in phenolic composition of Cyclopia pubescens (honeybush tea) seedling plants. Journal of Food Composition and Analysis 2019, 78, 129 -137.

AMA Style

Nico A. Walters, Dalene De Beer, André De Villiers, Beata Walczak, Elizabeth Joubert. Genotypic variation in phenolic composition of Cyclopia pubescens (honeybush tea) seedling plants. Journal of Food Composition and Analysis. 2019; 78 ():129-137.

Chicago/Turabian Style

Nico A. Walters; Dalene De Beer; André De Villiers; Beata Walczak; Elizabeth Joubert. 2019. "Genotypic variation in phenolic composition of Cyclopia pubescens (honeybush tea) seedling plants." Journal of Food Composition and Analysis 78, no. : 129-137.

Research article
Published: 13 January 2019 in Journal of the Science of Food and Agriculture
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BACKGROUND Rooibos represents 10% of the global herbal tea market. Shrinking production areas due to climate change necessitate maximum conversion of plant biomass to product. The aim of the study was to determine the potential of rooibos tea processing waste, i.e. fine dust and coarse stems, as potential flavour and herbal tea ingredients, respectively. RESULTS Hot water extraction of soluble solids from rooibos dust was optimised and extracts from different production batches (n = 20) were prepared. Their sensory profiles were similar, but less intense than that of infusions of commercial rooibos (n = 20) when diluted to the same soluble solids content. The turbidity and flavonoid content of the diluted extracts was mostly lower (P < 0.05) than that of commercial rooibos. An atypical and negative aroma attribute, “planky/pencil shavings”, was predominant in the stem infusions (n = 20), which contained less soluble solids (P < 0.05) than commercial rooibos. Blends of stem infusion and extract could not effectively mask this negative aroma note (P > 0.05). CONCLUSIONS Rooibos dust could be used to produce a rooibos flavour extract, while the prominent atypical, negative “planky/pencil shavings” aroma note of the stems would limit their inclusion in commercial rooibos blends. This article is protected by copyright. All rights reserved.

ACS Style

Manzimase Sishi; Magdalena Muller; Dalene De Beer; Marieta Van Der Rijst; Elizabeth Joubert. Rooibos agro‐processing waste as herbal tea products: optimisation of soluble solids extraction from dust and application to improve sensory profile, colour and flavonoid content of stem infusions. Journal of the Science of Food and Agriculture 2019, 99, 3653 -3661.

AMA Style

Manzimase Sishi, Magdalena Muller, Dalene De Beer, Marieta Van Der Rijst, Elizabeth Joubert. Rooibos agro‐processing waste as herbal tea products: optimisation of soluble solids extraction from dust and application to improve sensory profile, colour and flavonoid content of stem infusions. Journal of the Science of Food and Agriculture. 2019; 99 (7):3653-3661.

Chicago/Turabian Style

Manzimase Sishi; Magdalena Muller; Dalene De Beer; Marieta Van Der Rijst; Elizabeth Joubert. 2019. "Rooibos agro‐processing waste as herbal tea products: optimisation of soluble solids extraction from dust and application to improve sensory profile, colour and flavonoid content of stem infusions." Journal of the Science of Food and Agriculture 99, no. 7: 3653-3661.

Short communication
Published: 07 December 2018 in Journal of Food Composition and Analysis
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Two endemic South African herbal teas, namely rooibos (Aspalathus linearis) and honeybush (Cyclopia spp.), are especially valued for their caffeine-free status. No recent evidence based on state-of-the-art analytical methodology with low limits of detection (e.g. below 1 μg/L) is available. The current study provides such evidence. Randomly selected samples of fermented rooibos (n = 10) and honeybush herbal teas from four species (n = 10 each), namely C. intermedia, C. subternata, C. genistoides and C. longifolia, were analysed and no caffeine detected. Similarly, no caffeine was detected in green rooibos and C. genistoides herbal teas (n = 10 each) indicating that it is absent in the plant. Method specificity was shown to be important since peaks with molecular ion [M+H]+ and product ions resembling those of caffeine were detected, although the retention time and accurate mass did not match those of an authentic reference standard for caffeine.

ACS Style

Maria A. Stander; Elizabeth Joubert; Dalene De Beer. Revisiting the caffeine-free status of rooibos and honeybush herbal teas using specific MRM and high resolution LC-MS methods. Journal of Food Composition and Analysis 2018, 76, 39 -43.

AMA Style

Maria A. Stander, Elizabeth Joubert, Dalene De Beer. Revisiting the caffeine-free status of rooibos and honeybush herbal teas using specific MRM and high resolution LC-MS methods. Journal of Food Composition and Analysis. 2018; 76 ():39-43.

Chicago/Turabian Style

Maria A. Stander; Elizabeth Joubert; Dalene De Beer. 2018. "Revisiting the caffeine-free status of rooibos and honeybush herbal teas using specific MRM and high resolution LC-MS methods." Journal of Food Composition and Analysis 76, no. : 39-43.

Evaluation study
Published: 16 October 2018 in Journal of the Science of Food and Agriculture
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BACKGROUND Steam treatment of shredded, fresh C. maculata (honeybush) plant material improves the aroma of this green herbal tea with a slight impact on color and phenolic content, but the effect on storage stability is not known. RESULTS Steam‐treated (60 s before drying) and untreated (control), dried plant material were stored under normal storage conditions in semi‐permeable sachets at 25 °C and 60% relative humidity. Reference samples of treated (steamed) and untreated (control) material were stored at 0 °C in impermeable pouches for maximum retention of quality. The stability of the herbal tea was assessed in terms of sensory profile, phenolic composition and color over a storage period of 6 months. Normal storage conditions resulted in a significant (P < 0.05) decrease in green color, especially in steamed samples. Intensities of fruity and sweet‐associated aroma attributes increased progressively during storage, while the opposite was observed for vegetal and cereal‐like attributes. These changes in the aroma profile were more pronounced in untreated (control) samples. Individual phenolic content remained stable during storage. CONCLUSIONS Storage of 3 to 6 months may result in a more appealing aroma profile and enhanced product quality, despite loss of green color. This article is protected by copyright. All rights reserved.

ACS Style

Lara Alexander; Dalene de Beer; Magdalena Muller; Marieta van der Rijst; Elizabeth Joubert. Impact of steam treatment on shelf-life stability of a xanthone-rich green herbal tea (Cyclopia maculata Andrews Kies) - identifying quality changes during storage. Journal of the Science of Food and Agriculture 2018, 99, 1334 -1341.

AMA Style

Lara Alexander, Dalene de Beer, Magdalena Muller, Marieta van der Rijst, Elizabeth Joubert. Impact of steam treatment on shelf-life stability of a xanthone-rich green herbal tea (Cyclopia maculata Andrews Kies) - identifying quality changes during storage. Journal of the Science of Food and Agriculture. 2018; 99 (3):1334-1341.

Chicago/Turabian Style

Lara Alexander; Dalene de Beer; Magdalena Muller; Marieta van der Rijst; Elizabeth Joubert. 2018. "Impact of steam treatment on shelf-life stability of a xanthone-rich green herbal tea (Cyclopia maculata Andrews Kies) - identifying quality changes during storage." Journal of the Science of Food and Agriculture 99, no. 3: 1334-1341.