Optimisation of the Quantification of Total Soluble Solids, pH and Titratable Acidity in South African Grape Must using Fourier Transform Mid-infrared Spectroscopy

Calibration models for Fourier transform mid-infrared (FT-MIR) spectroscopy were developed for the simultaneousquantification of total soluble solids (TSS, measured as °Brix), pH and titratable acidity (TA, expressed as g/Ltartaric acid) in South African (SA) grape must. An exploratory data analysis of the FT-MIR spectra of 1170 grapemust samples (647 for °Brix, 252 for pH and 271 for TA) was done by principal component analysis, and partialleast squares regression was used for the computation of the regression models. The prediction errors for TSS (0.34°Brix), pH (0.04 units) and TA (0.51 g/L) provided analytical data of satisfactory accuracy. The evaluation of readyto-use global calibrations to quantify these three parameters in SA samples presented standard error of prediction(SEP) values of 0.46°Brix, 0.10 pH units and 3.13 g/L for TA. After slope and intercept adjustments of the originalglobal calibration algorithms, the SEP values were reduced to 0.38 °Brix, 0.05 pH units and 0.49 g/L for TA. Theseresults show the necessity for optimisation of the global FT-MIR WineScan calibrations to provide a better fit tosamples of South African origin. The results demonstrate that FT-MIR spectroscopy is a useful technique for therapid quantification of major grape must parameters and for quality control purposes in an industrial cellar

Data-driven Determination of Disease Markers' Threshold Values in Rot-affected Wine Grapes

[EN] Grapevine bunch rot is detrimental to grape and wine quality. Traditionally, detecting and quantifying the severity of rot infection is executed visually. This study aimed at defining local, area-specific threshold values of rot-associated disease markers. This is a first step towards making informed decisions about the quality of grapes delivered at winery intake. Viticulturists visually assessed on-vine rot infection in nine white wine grape cultivars. Results showed that severity ratings were consistent between assessors.Chemical analyses of the grape must from these assessed samples were done. Multiple factor analysis (MFA)showed that rot severity was positively correlated with glycerol, alcohol, gluconic acid and acetic acid concentrations. As severity increased, gluconic acid, glycerol, alcohol, Brix, acetic acid and total titratable acidity (TA) concentrations also increased. Following the probability chosen for sensitivity and specificity,grape rot indicators' threshold values in white grape must are as follow: Alcohol >= 0.10 %v/v; acetic acid >= 0.17 g/L; glycerol >= 0.79 g/L; gluconic acid >= 0.99 g/L; TA >= 8.86 g/L. Statistical determined threshold values differentiating between rot-affected and healthy grape must, would eliminate the subjectivity and bias associated with visual assessments.Cornelissen, R.; Kidd, M.; Aleixandre Tudo, J.; Nieuwoudt, H. (2022). Data-driven Determination of Disease Markers' Threshold Values in Rot-affected Wine Grapes. South African journal of enology and viticulture. 43(1):85-95. https://doi.org/10.21548/43-1-4960859543

Prediction of ‘Nules Clementine’ mandarin susceptibility to rind breakdown disorder using Vis/NIR spectroscopy

The use of diffuse reflectance visible and near infrared (Vis/NIR) spectroscopy was explored as a non-destructive technique to predict ‘Nules Clementine’ mandarin fruit susceptibility to rind breakdown (RBD) disorder by detecting rind physico-chemical properties of 80 intact fruit harvested from different canopy positions. Vis/NIR spectra were obtained using a LabSpec® spectrophotometer. Reference physico-chemical data of the fruit were obtained after 8 weeks of storage at 8 °C using conventional methods and included RBD, hue angle, colour index, mass loss, rind dry matter, as well as carbohydrates (sucrose, glucose, fructose, total carbohydrates), and total phenolic acid concentrations. Principal component analysis (PCA) was applied to analyse spectral data to identify clusters in the PCA score plots and outliers. Partial least squares (PLS) regression was applied to spectral data after PCA to develop prediction models for each quality attribute. The spectra were subjected to a test set validation by dividing the data into calibration (n = 48) and test validation (n = 32) sets. An extra set of 40 fruit harvested from a different part of the orchard was used for external validation. PLS-discriminant analysis (PLS-DA) models were developed to sort fruit based on canopy position and RBD susceptibility. Fruit position within the canopy had a significant influence on rind biochemical properties. Outside fruit had higher rind carbohydrates, phenolic acids and dry matter content and lower RBD index than inside fruit. The data distribution in the PCA and PLS-DA models displayed four clusters that could easily be identified. These clusters allowed distinction between fruit from different preharvest treatments. NIR calibration and validation results demonstrated that colour index, dry matter, total carbohydrates and mass loss were predicted with significant accuracy, with residual predictive deviation (RPD) for prediction of 3.83, 3.58, 3.15 and 2.61, respectively. The good correlation between spectral information and carbohydrate content demonstrated the potential of Vis/NIR as a non-destructive tool to predict fruit susceptibility to RBD

Male circumcision and Neisseria gonorrhoeae, Chlamydia trachomatis and Trichomonas vaginalis: observations after a randomised controlled trial for HIV prevention

International audienceOBJECTIVE: To assess the association between male circumcision and Neisseria gonorrhoeae, Chlamydia trachomatis and Trichomonas vaginalis using data from a male circumcision randomised controlled trial. METHODS: We used data collected during the male circumcision trial conducted in Orange Farm (South Africa) among men aged 18-24 years. Altogether, 1767 urine samples collected during the final follow-up visit were analysed using PCR. Prevalence of N gonorrhoeae, C trachomatis and T vaginalis was assessed as a function of male circumcision using odds ratios (OR) given by univariate and multivariate logistic regression. RESULTS: In an intention-to-treat analysis, prevalence of N gonorrhoeae, C trachomatis and T vaginalis among intervention and control groups were 10.0% versus 10.3% (OR 0.97; p = 0.84), 2.1% versus 3.6% (OR 0.58; p = 0.065) and 1.7% versus 3.1% (OR 0.54; p = 0.062), respectively. The association between T vaginalis and male circumcision remained borderline when controlling for age, ethnic group, number of lifetime partners, marital status, condom use and HIV status (AOR 0.48; p = 0.069). In the as-treated analysis, this association became significant (OR 0.49, p = 0.030; AOR 0.41, p = 0.030). CONCLUSIONS: This study demonstrates for the first time that male circumcision reduces T vaginalis infection among men. This finding explains why women with circumcised partners are less at risk for T vaginalis infection than other women. The protective effect on T vaginalis is an additional argument to recommend male circumcision in Africa where it is acceptable

Quantitative Survey of 3-alkyl-2-methoxypyrazines and First Confirmation of 3-ethyl-2-methoxypyrazine in South African Sauvignon blanc Wines

3-Alkyl-2-methoxypyrazines are important aroma components in Sauvignon blanc wine, contributing tothe typical vegetative character associated with the cultivar. The analysis of methoxypyrazines is highlychallenging and, as a result, limited quantitative data are available for South African Sauvignon blancwines. In this study, liquid chromatography-tandem mass spectrometry was applied for the sensitivequantification of the three principal methoxypyrazines in 881 South African Sauvignon blanc wines. Thetotal wine methoxypyrazine concentration exceeded the combined recognition threshold for the vegetativearoma in more than 60% of the samples, demonstrating the involvement of these compounds in the typicalaroma of the cultivar. The analytical method was adapted to allow the accurate quantitation and spectralconfirmation of 3-ethyl-2-methoxypyrazine in Sauvignon blanc wines for the first time. Concentrationsranged between 1.1 and 4.9 ng/L. Statistically significant relationships between wine methoxypyrazineconcentrations and parameters related to the maturity of the grapes and to the climate, as well asgeographical origin and vintage, were found

Aspects of the skin morphology in the sub-Antarctic fur seal Arctocephalus tropicalis

DATA AVAILABILITY : The original database no longer exists. The photomicrographs on which the histological descriptions and parameter definitions are based will be available upon request.SUPPLEMENTARY FILE 1—ESM 1a. Photomicrograph (no scale available) of a cross section through the furred skin of a sub-Antarctic fur seal showing the two principal layers: (a) the outer epidermis, (b) the underlying dermis, (c) a common pilary canal, (d) a guard hair, and (e) associated under hairs. The glandular nature of the dermis is evident, although the poor resolution and low magnification complicates the clear separation of (f) sebaceous glands (usually adjacent to pilosebaceous units) and (g) sweat glands (usually around base of pilosebaceous units). ESM 1b Photomicrograph (no scale available) of a cross section through the naked skin of a sub-Antarctic fur seal showing the coiled, tubular nature of the secretory portion of a sweat gland. ESM 1c Photomicrograph (no scale available) of a cross section through the dermis of the furred skin of a sub-Antarctic fur seal, parallel to the surface of the skin, showing (a) guard hairs and (b) associated under hairs. In the one instance (c) both the guard hair and the associated under hairs are situated in the common pilary canal close to opening up at the surface of the skin. (DOCX 5680 KB)SUPPLEMENTARY FILE 2—ESM 2 Table 1. Common pilary canal density of sweat glands in the furred and naked skin of adult male sub-Antarctic fur seals. ESM 2 Table 2 Volume of the secretory section of sweat glands in the furred and naked skin of adult male sub-Antarctic fur seals (DOCX 30 KB)The present study examined whether sweat glands are present in the skin of sub-Antarctic fur seals, Arctocephalus tropicalis, using standard histological procedures and light microscopy. Aspects of the microanatomy and histology of skin were described to elucidate structure and function. Sweat glands were present both in the furred areas of the body trunk, as well as in naked skin areas of the flippers. The density of the apocrine sweat glands appeared higher in fur-covered areas than in naked areas, while the size of sweat glands was similar amongst naked and fur-covered skin. The superficial position of sweat glands in the dermis of naked skin areas and the large, coiled, tubular nature of the secretory portion seem to indicate sweat gland activity in contrast to the deep lying, narrow sweat glands in fur-covered areas.Open access funding provided by University of Pretoria.https://link.springer.com/journal/435hj2023Mammal Research InstituteZoology and Entomolog

Fermentation-derived Aroma Compounds in Varietal Young Wines from South Africa

The volatile composition of 925 single cultivar young Sauvignon blanc, Chardonnay, Pinotage, Merlot, Shirazand Cabernet Sauvignon wines of vintages 2005 to 2007, was determined using gas chromatography – flameionisation detection. Compositional data were compared to published data on young wines from South Africa andother countries. South African young wines analysed in this study had a largely similar volatile composition tothat reported in the literature. Significant between-vintage and between-cultivar differences were observed in thevolatile composition of the wines investigated in this study. The concentration ranges of four compounds in redwines, hexanol, propanol, diethyl succinate and ethyl lactate, and four compounds in white wines, 2-phenylethanol,hexanoic acid, isoamyl acetate and propanol, were not influenced by vintage effects. This finding was interpretedas the first indication that typical concentration ranges for some aroma compounds can be established for SouthAfrican young cultivar wines. A trend was observed in the white wines that the alcohols and their respective acetateesters, as well as fatty acids and their ethyl esters, were responsible for the vintage-related effects. Differences involatile composition between Chardonnay and Sauvignon blanc wines could also largely be explained on the samebasis. Classification models were established to discriminate between individual red wine cultivars and between thetwo white wine cultivars and correct classification rates of respectively, 79 % and 85 % were achieved

Probing structural relaxation in complex fluids by critical fluctuations

Complex fluids, such as polymer solutions and blends, colloids and gels, are of growing interest in fundamental and applied soft-condensed-matter science. A common feature of all such systems is the presence of a mesoscopic structural length scale intermediate between atomic and macroscopic scales. This mesoscopic structure of complex fluids is often fragile and sensitive to external perturbations. Complex fluids are frequently viscoelastic (showing a combination of viscous and elastic behaviour) with their dynamic response depending on the time and length scales. Recently, non-invasive methods to infer the rheological response of complex fluids have gained popularity through the technique of microrheology, where the diffusion of probe spheres in a viscoelastic fluid is monitored with the aid of light scattering or microscopy. Here we propose an alternative to traditional microrheology that does not require doping of probe particles in the fluid (which can sometimes drastically alter the molecular environment). Instead, our proposed method makes use of the phenomenon of "avoided crossing" between modes associated with the structural relaxation and critical fluctuations that are spontaneously generated in the system.Comment: 4 pages, 4 figure