Development of sensory tools for green rooibos (Aspalathus linearis (Burm.f.) R.Dahlgren) and changes in quality attributes during shelf-life storage.

BACKGROUND: Green rooibos (Aspalathus linearis (Burm.f.) R.Dahlgren) herbal tea is popular due to its health-promoting properties. Information on its characteristic sensory profile is scarce and sensory tools to define product variation are needed. The storage conditions and time during its shelf-life are hypothesized to affect the product quality. RESULTS: Production batches from two producers spanning 5 years (n = 57) were analyzed using descriptive sensory analysis. Primary attributes (>30 median intensity; 100% occurrence frequency) included 'hay/dried grass', 'cooked oats', 'tobacco', 'honey' and 'caramel' aromas, and astringent mouthfeel. 'Cooked vegetables', 'green grass', 'stewed fruit', 'rooibos-woody', 'marmalade' and 'cardboard' aromas, sweet taste and bitter taste were secondary attributes (10-20 median intensity; 100% occurrence frequency). The same flavor attributes were present, except for sweet-associated and fruity notes. A sensory lexicon and sensory wheels for aroma and palate attributes were constructed from the data. The shelf-life stability of green rooibos was evaluated in moisture-impermeable (pouches) and moisture-permeable (sachets) packaging at 25 and 40 °C at 60% relative humidity over 24 weeks. Green rooibos samples stored in pouches at 4 °C were also evaluated. Storage in sachets led to moisture uptake (~10 g (100 g)-1 dry basis) and an increase in water activity (>0.6), causing degradation of chlorophyll and dihydrochalcones. Changes in color and sensory profile (decreased vegetal, cereal and cardboard aromas and increased sweet-associated and fruity aromas) were evident and more pronounced at the higher storage temperature. CONCLUSIONS: Storage at ≤25 °C in moisture-impermeable packaging material is recommended for green rooibos herbal tea. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effect of Sampling Time, Quantification Method, and Tree Sample Pooling on Phytophthora cinnamomi Root Quantities in South African Avocado Orchards.

Phytophthora cinnamomi is a destructive soilborne pathogen causing Phytophthora root rot on avocados worldwide. Little is known about the effect of root sampling time, root quantification method (quantitative real-time PCR [qPCR] versus baiting), and tree sample pooling strategies on the quantification of the pathogen in roots in avocado orchard trees. This was investigated in six avocado orchards in two climatically different production regions (Mooketsi and Letaba) in the Limpopo Province, South Africa, over a 2-year period. Two different tree sample pooling strategies, consisting of either a four-pooled group (four groups each containing five pooled trees) or a single-pooled group (20 trees pooled) per 1 ha, were both shown to be suitable for quantifying P. cinnamomi in tree roots using qPCR or root baiting. P. cinnamomi root quantities from the two tree sample pooling strategies were significantly correlated for both quantification methods. Both quantification methods were suitable for quantifying the pathogen in roots, although qPCR was superior to root baiting at identifying significant differences in P. cinnamomi quantities among root sampling time points. The effect of sampling time was dependent on the investigated year. In 2017, root quantities, which were only evaluated using qPCR, did not reveal a consistent trend of a specific sampling time yielding the highest root quantities for most of the orchards. However, five of the orchards in 2018, based on the qPCR analyses, contained significantly higher P. cinnamomi root quantities in May (late autumn) than in March (early autumn), August (late winter), and October/November (late spring). In 2018, P. cinnamomi root DNA quantities were significantly positively correlated with the number of soil temperature hours at 20 to 24 and 20 to 29°C 2 months preceding the root sampling dates and negatively correlated with the number of hours at 15 to 19°C 2 months preceding root sampling. Our study has identified P. cinnamomi root quantification methods and tree sample pooling strategies, which will be useful for understanding the biology of the pathogen and when disease management strategies should be in place.

Food-grade phytosome vesicles for nanoencapsulation of labile C-glucosylated xanthones and dihydrochalcones present in a plant extract matrix-Effect of process conditions and stability assessment.

Phytosomes consist of a phytochemical bound to the hydrophilic choline head of a phospholipid. Their use in food products is gaining interest. However, literature on the use of food-grade solvents, crude plant extracts as opposed to pure compounds, and unrefined phospholipids to prepare phytosomes is limited. Furthermore, studies on compound stability are lacking. This study aimed to develop nano-phytosome vesicles prepared from inexpensive food-grade ingredients to improve the stability of polyphenolic compounds. Cyclopia subternata extract (CSE) was selected as a source of phenolic compounds. It contains substantial quantities of C-glucosyl xanthones, benzophenones, and dihydrochalcones, compounds largely neglected to date. The effect of process conditions on the complexation of CSE polyphenols with minimally refined food-grade fat-free soybean lecithin (PC) was studied. The PC:CSE ratio, sonication time, and reaction temperature were varied. This resulted in phytosomes ranging in vesicle size (113.7-312.7 nm), polydispersity index (0.31-0.48), and zeta potential (-55.0 to -38.9 mV). Variation was also observed in the yield (93.5%-96.0%), encapsulation efficiency (3.7%-79.0%), and loading capacity (LC, 1.3%-14.7%). Vesicle size and LC could be tailored by adjusting the sonication time and PC:CSE ratio, respectively. Chemical interaction between the lipid and the phenolic compounds was confirmed with nuclear magnetic resonance. Phytosomal formulation protected the compounds against degradation when freeze-dried samples were stored at 25 and 40°C for 6 months at low relative humidity. The study provided valuable information on the importance of specific process parameters in producing food-grade phytosomes with improved phenolic stability.

Reaction kinetics of aspalathin degradation and flavanone isomer formation in aqueous model solutions: Effect of temperature, pH and metal chelators.

The poor stability of aspalathin in aqueous solutions is a major challenge in delivering a shelf-stable ready-to-drink (RTD) green rooibos iced tea. The kinetics of aspalathin degradation and the formation of eriodictyol glucoside isomers [(S/R)-6-ß-D-glucopyranosyleriodictyol and (S/R)-8-ß-D-glucopyranosyleriodictyol] in aqueous buffers were modeled to understand and predict aspalathin losses during heat processing. The effects of temperature and pH on the rate constants of aspalathin degradation and eriodictyol glucoside isomer formation were determined in a 0.1 M phosphate buffer with 5.7 mM citric acid. The zero-order model best described the reaction kinetics of aspalathin degradation and eriodictyol glucoside isomer formation. Increasing the temperature and pH increased the reaction rate constants. The activation energies of the reactions were much lower at pH 6 than at pH 4, indicating that pH affected the temperature dependence of the reactions. The 8-C-glucosyl eriodictyol derivatives (RE8G and SE8G) formed at much lower rates than the 6-C-glucosyl eriodictyol derivatives (RE6G and SE6G). The metal chelators, citric acid, citrate and EDTA, drastically reduced the reaction rate constants, indicating the catalytic role of metal ions in aspalathin autoxidation. The results of the study could assist manufacturers to improve the shelf life of rooibos RTD beverages by changing the formulation and adjusting heat processing conditions.

Heat treatment improves the sensory properties of the ultrafiltration by-product of honeybush (Cyclopia genistoides) extract.

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 valorization 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 those 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' (oxidized) 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. © 2021 Society of Chemical Industry.

Shelf-Life Stability of Ready-to-Use Green Rooibos Iced Tea Powder-Assessment of Physical, Chemical, and Sensory Properties.

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.

Pathogenicity Testing of Fungal Isolates Associated with Olive Trunk Diseases in South Africa.

A recent olive trunk disease survey performed in the Western Cape Province, South Africa, identified several fungi associated with olive trunk disease symptoms, including species of Basidiomycota, Botryosphaeriaceae, Coniochaetaceae, Calosphaeriaceae, Diaporthaceae, Diatrypaceae, Phaeomoniellaceae, Phaeosphaeriaceae, Symbiotaphrinaceae, Togniniaceae, and Valsaceae. Many of the species recovered had not yet been reported from olive trees; therefore, the aim of this study was to determine their pathogenicity toward this host. Pathogenicity tests were first conducted on detached shoots to select virulent isolates, which were then used in field trials. During field trials, 2-year-old olive branches of 15-year-old trees were inoculated by inserting colonized agar plugs into artificially wounded tissue. Measurements were made of the internal lesions after 8 months. In total, 58 isolates were selected for the field trials. Species that formed lesions significantly larger than the control could be considered as olive trunk pathogens. These included Biscogniauxia rosacearum, Celerioriella umnquma, Coniochaeta velutina, Coniothyrium ferrarisianum, isolates of the Cytospora pruinosa complex, Didymocyrtis banksiae, Diaporthe foeniculina, Eutypa lata, Fomitiporella viticola, Neofusicoccum stellenboschiana, Neofusicoccum vitifusiforme, Neophaeomoniella niveniae, Phaeoacremonium africanum, Phaeoacremonium minimum, Phaeoacremonium oleae, Phaeoacremonium parasiticum, Phaeoacremonium prunicola, Phaeoacremonium scolyti, Phaeoacremonium spadicum, Pleurostoma richardsiae, Pseudophaeomoniella globosa, Punctularia atropurpurascens, Vredendaliella oleae, an undescribed Cytospora sp., Geosmithia sp., two undescribed Neofusicoccum spp., and four Xenocylindrosporium spp. Pseudophaeomoniella globosa can be regarded as one of the main olive trunk pathogens in South Africa because of its high incidence from olive trunk disease symptoms in established orchards and its high virulence in pathogenicity trials.

Physicochemical Stability of Enriched Phenolic Fractions of Cyclopia genistoides and ex vivo Bi-directional Permeability of Major Xanthones and Benzophenones.

Fractions of an ultrafiltered Cyclopia genistoides extract, respectively enriched in xanthones and benzophenones, were previously shown to inhibit mammalian α-glucosidase in vitro. The present study investigated ex vivo intestinal transport of these fractions, using excised porcine jejunal tissue, to determine whether the gut could be a predominant in vivo site of action. The major bioactive compounds, the xanthones (mangiferin, isomangiferin) and benzophenones (3-ß-D-glucopyranosyliriflophenone, 3-ß-D-glucopyranosyl-4-O-ß-D-glucopyranosyliriflophenone) exhibited poor permeation in the absorptive direction with a relatively high efflux ratio (efflux ratio > 1). The efflux ratio of 3-ß-D-glucopyranosyl-4-O-ß-D-glucopyranosyliriflophenone (3.05) was similar to rhodamine 123 (2.99), a known substrate of intestinal P-glycoprotein 1 efflux transporters. Low epithelial membrane transport rates, coupled with efflux mechanisms, would effectively concentrate these bioactive compounds at the target site (gut lumen). Storage stability testing and moisture sorption assays of the xanthone-enriched fraction, benzophenone-enriched fraction, and ultrafiltered Cyclopia genistoides extract were performed to determine their susceptibility to physical and chemical degradation during storage. Hygroscopicity of the powders, indicated by moisture uptake, decreased in the order: benzophenone-enriched fraction (22.7%) > ultrafiltered Cyclopia genistoides extract (14.0%) > xanthone-enriched fraction (10.7%). 3-ß-D-Glucopyranosylmaclurin, a minor benzophenone, was the least stable of the compounds, degrading faster in the benzophenone-enriched fraction than in ultrafiltered Cyclopia genistoides extract, suggesting that the ultrafiltered extract matrix may provide a degree of protection against chemical degradation. Compound degradation during 12 wk of storage at 40 °C in moisture-impermeable containers was best explained by first order reaction kinetics.

Potential of benzophenones and flavanones to modulate the bitter intensity of Cyclopia genistoides herbal tea.

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-ß-d-glucopyranosyl-4-ß-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)-ß-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.

Phenolic composition of rooibos changes during simulated fermentation: Effect of endogenous enzymes and fermentation temperature on reaction kinetics.

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.

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.

BACKGROUND: Rooibos represents 10% of the global herbal tea market. Shrinking production areas as a result of climate change necessitate the maximum conversion of plant biomass to product. The present study aimed 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 (SS) from rooibos dust was optimised and extracts from different production batches (n = 20) were prepared. Their sensory profiles were similar, although less intense than that of infusions of commercial rooibos (n = 20) when diluted to the same SS 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 SS (P < 0.05) than commercial rooibos. Blends of stem infusion and extract could not effectively mask this negative aroma note (P > 0.05). CONCLUSION: Rooibos dust could be used to produce a rooibos flavour extract, whereas the prominent atypical, negative 'planky/pencil shavings' aroma note of the stems would limit their inclusion in commercial rooibos blends. © 2019 Society of Chemical Industry.

Impact of steam treatment on shelf-life stability of a xanthone-rich green herbal tea (Cyclopia maculata Andrews Kies) - identifying quality changes during storage.

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 was 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. © 2018 Society of Chemical Industry.

Electrospraying as a suitable method for nanoencapsulation of the hydrophilic bioactive dihydrochalcone, aspalathin.

The bioactive hydrophilic dihydrochalcone, aspalathin, has poor stability and bioavailability hampering its use in functional food ingredients with standardised aspalathin content. The aim of the study was to produce nanoparticles with controlled release to overcome these obstacles. Nanoencapsulation was investigated using both natural (chitosan and lecithin) and synthetic (poly(lactide-co-glycolide) and Eudragit S100® (ES100)) polymers by suitable conventional methods and electrospraying for all polymers. All polymer-method combinations produced particles smaller than 1.1 µm. Electrospraying produced more favourable results than conventional methods for the synthetic polymers, resulting in spherical particles with higher (p < 0.05) encapsulation efficiencies (>50%) and loading capacities (>10%). Opposite trends were observed for natural polymers. An in vitro release study revealed biphasic aspalathin release profiles at pH 7.4 with ES100 electrosprayed nanoparticles having the slowest (p < 0.05) release rate (1.67 h-1). Overall, ES100 electrosprayed nanoparticles showed the most favourable combination of parameters.

Bitter profiling of phenolic fractions of green Cyclopia genistoides herbal tea.

The bitter taste of Cyclopia genistoides infusions is unacceptable to consumers, who are used to the slightly sweet taste of the herbal teas produced from other Cyclopia species. Bitter taste intensities of crude phenolic fractions of a bitter hot water extract of C. genistoides were determined by a trained panel to identify the fraction contributing most to the bitter taste. Fractions, enriched in benzophenones (B), xanthones (X) and flavanones (F), and each tested at their infusion equivalent concentration (IEC) scored 5, 31 and 13 (on a 100-point scale), respectively. Fraction B, containing mostly iriflophenone glucosides, was perceived as not bitter. The major xanthone in fraction X, mangiferin, was significantly (p < 0.05) more bitter than its regio-isomer, isomangiferin, at equal concentration. A mixture of isomangiferin and mangiferin at their IECs was significantly (p < 0.05) less bitter than the mangiferin solution alone, indicating bitter suppression by isomangiferin.

Quality characteristics of Warthog (Phacochoerus africanus) meat.

Warthogs are hunted for trophies and damage reprisal whilst the meat is consumed. Little is known about the quality profile of the meat, therefore, this study investigated the effect of age (yearlings and adult) and sex on the sensory, physical, and chemical attributes of cooked meat. The meat was high in protein (~32%) and low in total fat (< 2%), while the meat from yearlings tended to be tenderer than adults. Age appeared to have a more pronounced influence than sex on the sensory attributes. Warthog meat had a pork aroma and flavour. Undesirable odours and flavours were described as sour/sweaty and fishy, and adults differed from yearlings regarding sour/sweaty (P = .025) and fishy aromas (P = .006), and fishy flavours (P = .045). Small differences (< 0.5 mg/g) in palmitoleic (P = .047) and arachidonic (P = .038) acids were found between adults and yearlings. Warthog meat can be regarded as a lean and healthy source of protein.

Sensory quality and fatty acid content of springbok (Antidorcas marsupialis) meat: influence of farm location and sex.

BACKGROUND: Springbok are harvested for meat production irrespective of farm location or sex from which the meat is derived. The present study investigated the influence of farm location (three farms containing different vegetation types) and sex on the sensory quality of springbok longissimus thoracis et lumborum muscle. The sensory profile (aroma, flavour and texture) was determined by descriptive sensory analysis, in addition to determination of the physical meat quality, proximate and fatty acid composition. RESULTS: Farm location had a significant influence on the sensory quality (gamey and liver-like aroma; beef, liver-like, lamb-like and herbaceous flavour; sweet taste; tenderness; residue; mealiness; Warner-Bratzler shear force; moisture, protein and intramuscular lipid content) and fatty acid content (oleic acid; α-linolenic acid; total saturated and monounsaturated fatty acids; polyunsaturated to saturated fatty acid ratio; total omega-3 polyunsaturated fatty acid; and omega-6 to omega-3 polyunsaturated fatty acid ratio) of springbok meat. Sex influenced the chemical composition of springbok meat; however, the influence on the sensory profile was minor (sweet taste; P < 0.001). CONCLUSION: Farm location could influence the sensory quality and composition of springbok meat and should be considered when harvesting for meat production. Sex does not have to be considered for the marketing of springbok meat. © 2017 Society of Chemical Industry.

Phenolic and physicochemical stability of a functional beverage powder mixture during storage: effect of the microencapsulant inulin and food ingredients.

BACKGROUND: The need for a convenience herbal iced tea product with reduced kilojoules merited investigation of the shelf-life of powder mixtures containing a green Cyclopia subternata Vogel (honeybush) extract with proven blood glucose-lowering activity and alternative sweetener mixture. RESULTS: Prior to long-term storage testing, the wettability of powder mixtures containing food ingredients and the compatibility of their components were confirmed using the static sessile drop method and isothermal microcalorimetry, respectively. The powders packed in semi-sealed containers remained stable during storage at 25 °C/60% relative humidity (RH) for 6 months, except for small losses of specific phenolic compounds, namely mangiferin, isomangiferin, 3-ß-d-glucopyranosyliriflophenone, vicenin-2 and 3',5'-di-ß-d-glucopyranosylphloretin, especially when both citric acid and ascorbic acid were present. These acids drastically increased the degradation of phenolic compounds under accelerated storage conditions (40 °C/75% RH). Accelerated storage also caused changes in the appearance of powders and the colour of the reconstituted beverage solutions. Increased moisture content and aw of the powders, as well as moisture released due to dehydration of citric acid monohydrate, contributed to these changes. CONCLUSION: A low-kilojoule honeybush iced tea powder mixture will retain its functional phenolic compounds and physicochemical properties during shelf-life storage at 25 °C for 6 months. © 2017 Society of Chemical Industry.

Stable isotope ratio analysis: A potential analytical tool for the authentication of South African lamb meat.

Stable isotope ratios ((13)C/(12)C and (15)N/(14)N) of South African Dorper lambs from farms with different vegetation types were measured by isotope ratio mass spectrometry (IRMS), to evaluate it as a tool for the authentication of origin and feeding regime. Homogenised and defatted meat of the Longissimus lumborum (LL) muscle of lambs from seven different farms was assessed. The δ(13)C values were affected by the origin of the meat, mainly reflecting the diet. The Rûens and Free State farms had the lowest (p ⩽ 0.05) δ(15)N values, followed by the Northern Cape farms, with Hantam Karoo/Calvinia having the highest δ(15)N values. Discriminant analysis showed δ(13)C and δ(15)N differences as promising results for the use of IRMS as a reliable analytical tool for lamb meat authentication. The results suggest that diet, linked to origin, is an important factor to consider regarding region of origin classification for South African lamb.

Oogonial biometry and phylogenetic analyses of the Pythium vexans species group from woody agricultural hosts in South Africa reveal distinct groups within this taxon.

Pythium vexans fits into the internal transcribed spacer (ITS) clade K sensu Lévesque & De Cock (2004). Within clade K, P. vexans forms a distinct clade containing two enigmatic species, Pythium indigoferae and Pythium cucurbitacearum of which no ex-type strains are available. In South Africa, as well as in other regions of the world, P. vexans isolates are known to be heterogeneous in their ITS sequences and may consist of more than one species. This study aimed to investigate the diversity of South African P. vexans isolates, mainly from grapevines, but also citrus and apple using (i) phylogenetic analyses of the ITS, cytochrome c oxidase (cox) I, cox II, and ß-tubulin regions and (ii) seven biometric oogonial parameters. Each of the phylogenies clustered P. vexans isolates into a single well-supported clade, distinct from other clade K species. The ß-tubulin region was phylogenetically uninformative regarding the P. vexans group. The ITS phylogeny and combined cox I and II phylogenies, although each revealing several P. vexans subclades, were incongruent. One of the most striking incongruences was the presence of one cox subclade that contained two distinct ITS subclades (Ib and IV). Three groups (A-C) were subjectively identified among South African P. vexans isolates using (i) phylogenetic clades (ITS and cox), (ii) univariate analysis of oogonial diameters, and (iii) multivariate analyses of biometric oogonial parameters. Group A is considered to be P. vexans s. str. since it contained the P. vexans CBS reference strain from Van der Plaats-Niterink (1981). This group had significantly smaller oogonial diameters than group B and C isolates. Group B contained the isolates from ITS subclades Ib and IV, which formed a single cox subclade. The ITS subclade IV isolates were all sexually sterile or produced mainly abortive oospores, as opposed to the sexually fertile subclade Ib isolates, and may thus represent a distinct assemblage within group B. Although ITS subclade Ib included the P. indigoferae ex-type sequence, this group was considered to be P. vexans since South African isolates in this clade produced globose sporangia. Group C contained four apple isolates that were related to, but distinct from P. cucurbitacearum. Although P. vexans groups A-C might be distinct species, they are not described here as such due to (i) these groups only representing some of the known diversity in P. vexans, (ii) conflicting gene tree phylogenies preventing phylogenetic species identification, and (iii) sexually sterile isolates preventing the broad application of biometrical data.