Hélène H Nieuwoudt

Hélène H Nieuwoudt
Stellenbosch University | SUN · Institute for Wine Biotechnology

PhD

About

90
Publications
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2,058
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Publications

Publications (90)
Article
Full-text available
The pomegranate kernel oil has gained global awareness due to the health benefits associated with its consumption; these benefits have been attributed to its unique fatty acid composition. For quality control of edible fats and oils, various analytical and calorimetric methods are often used, however, these methods are expensive, labor-intensive, a...
Article
Full-text available
Infrared spectroscopy provides an efficient, robust, and multivariate means to measure phenolic levels during red-wine fermentations. However, its use is currently limited to off-line sampling. In this study, partial least squares (PLS) regression was used to investigate the possibility of using spectral data from minimally pre-treated or untreated...
Article
Improvements to technology which allows quantification of phenolic compounds, such as tannins, anthocyanins, and polymeric pigments, are continually being made. Currently infrared (IR) spectroscopy technology is promising due to the rapidity and multivariate nature of the measurements and its non-destructive nature. However, most developments have...
Article
Full-text available
This review covers recent developments in the field of non-invasive techniques for the quality assessment of processed horticultural products over the past decade. The concept of quality and various quality characteristics related to evaluating processed horticultural products are detailed. A brief overview of non-invasive methods, including spectr...
Conference Paper
Consumers are willing to pay significantly higher prices for food and beverage products of certain, especially valued geographic origin. The control of declared geographic origin of food and beverages thus is an important issue, as it represents protection and prevention of consumer deception and fraud. We compared wine samples from Austria and Sou...
Article
Full-text available
The fourth agricultural revolution is leading us into a time of using data science as a tool to implement precision viticulture. Infrared spectroscopy provides the means for rapid and large-scale data collection to achieve this goal. The non-invasive applications of infrared spectroscopy in grapevines are still in its infancy, but recent studies ha...
Article
Full-text available
This study investigated the effects of extraction methods on the physicochemical, phytochemical, and antioxidant properties of pomegranate juice (cv. Wonderful). In addition, the application of attenuated total reflectance Fourier transformed mid-infrared (ATR-FT-MIR) spectroscopy and chemometrics were explored in order to discriminate between diff...
Article
Full-text available
Culture is an important factor that influences how marketing interacts with food choice. This study aims at exploring the effect of consumers’ Country of Origin (COO) on wine representations and perception using Chenin blanc as a model. The first objective was to evaluate the role of origin in the construction of the representation. We used the the...
Article
Full-text available
Some of the major processed horticultural commodities subjected to adulteration are powders, edible oils and juices. This review covers the recent application in the field of vibrational spectroscopic techniques (near and mid-infrared spectroscopy, Raman spectroscopy and hyperspectral imaging) for the determination of authenticity and adulteration...
Article
Delivering table grapes that are of exceptional quality and free of any defects or disease to different export markets is vital for table grape industries. After harvest, table grapes (non-climacteric fruit) do not improve, and maintenance of the quality achieved in the vineyard up to retail shelves remains a challenge. Currently, visual inspection...
Article
Highlights In the Emission Head (EH) configuration differences in apple bruise severity were well captured. A good representation of new samples variability, in calibration, ensured robust quantitative PLS-DA models. EH mode with PLS-DA is an attractive spectroscopic option for inline apple sorting based on bruise damage. Abstract. Bruise damage...
Article
Pivot© profile (PP), a method which compares samples to a reference (pivot), has shown profiling potential for complex matrices. However, various aspects require further investigation. This study’s aim was to compare PP to frequency of attribute citation (FC) considering individual judges’ data and sample set complexity. A trained panel analysed th...
Article
Full-text available
The determination of internal maturity parameters of table grape is usually done destructively using manual methods that are time-consuming. The possibility was investigated to determine whether key fruit attributes, namely, total soluble solids (TSS); titratable acidity (TA), TSS/TA, pH, and BrimA (TSS – k x TA) could be determined on intact table...
Article
Purpose This study aims to describe South African consumers’ wine risk perception on varietal level with recommendations for Chenin blanc. Design/methodology/approach An exploratory mixed methods approach was followed where qualitative data were used to develop the questionnaire. Quantitative data were collected from 2,051 respondents using an onl...
Article
Full-text available
Wine is of great economic and cultural significance for South Africa, but some population groups were until relatively recently denied equal access to wine and alcohol products. The South African wine industry has launched various campaigns in recent years that aimed at portraying wine as an acceptable and attractive choice when alcohol consumption...
Article
Full-text available
Hanseniaspora uvarum is one of the predominant non-Saccharomyces yeast species found on grapes and in juice, but its effect on lactic acid bacteria (LAB) growth and wine flavor has not been extensively studied. Therefore, the interaction between H. uvarum, two Saccharomyces cerevisiae yeast strains, two LAB species (Lactobacillus plantarum and Oeno...
Article
Rind biochemical properties play major roles in defence mechanisms against the incidence of rind physiological disorders of citrus fruit during cold storage. Hence, multivariate calibration models were developed to rapidly and non-destructively determine rind biochemical properties of citrus fruit from visible to near-infrared (Vis/NIR) spectra acq...
Article
Spectrometric methods based on near infrared radiation (NIR) are commonly used effectively in the agricultural and food industry. However, these methods still face limitations whereby meeting requirements for application such as nondestructive quality testing of large fruits and automated sorting and grading is still a challenge. A Fourier transfor...
Article
Full-text available
Consumer preference for fruit without disorder influence purchase of fruit at both local and international markets. Recent trends in horticulture show that consumer preference is influenced by assurance that external appearance is linked with rewarding internal sensory quality. Therefore, the need for non-destructive evaluation of external and inte...
Conference Paper
South African consumers’ purchase behaviour and perceptions of wine are underexplored. During a purchase situation, wine is known to cause feelings of uncertainty, especially amongst inexperienced wine consumers that tend to be risk averse and ‘only buy what they know’. In line with the consumer-focussed goals of Wine Industry Strategic Exercise (W...
Article
Full-text available
Quality plays an important role in the criteria directing wine product development. The evaluation of sensory characteristics associated with wine quality, as perceived by industry professionals, is therefore important. We investigated the suitability of the free-sorting sensory evaluation method, in combination with wine quality scoring using a 20...
Article
Commercial harvest maturity of 'Hass' avocado fruit is estimated based on dry matter content (DM). Typically, a few samples representing the entire orchard are destructively analysed using time-consuming procedures such as oven or freeze drying the fruit's mesocarp. However, the maturity parameter of avocado, that is known to have a direct link to...
Article
Spectroscopy techniques to efficiently measure phenolic composition in grape berries may be a suitable analytical practice, provided that robust calibrations are established. A contactless FT-NIR instrument was used for on-line spectral data collection from grapes transported on a conveyor belt system. Spectral data was also collected on static sam...
Article
Near infrared (NIR) and mid infrared (MIR) spectral acquisition modes were compared for predicting organoleptic and phytochemical quality attributes of pomegranate juice. Three Fourier transform infrared (FT-IR) spectrometers namely, a FT-NIR spectrometer, FT-MIR spectrometer in attenuated total reflection mode and FT-MIR spectrometer in transmissi...
Article
Table grapes are climacteric fruit and the quality will not improve after harvest. The quality, therefore, should be maintained from harvest, through post-harvest and finally the retail shelf. However, due to the multi-faceted nature of table grape quality, it is very difficult to put a monitoring tool in place, which can measure both the chemical...
Article
Near infrared spectroscopy (NIRS) has become a versatile tool for probing the properties of biomaterials such as fruit. Employing chemometric methods has allowed the effective use of NIRS to study complex materials including foodstuff and horticultural products. However, the complexity of the NIR spectral information may require that selective meth...
Article
Full-text available
The increasingly large volumes of publicly available sensory descriptions of wine raises the question whether this source of data can be mined to extract meaningful domain-specific information about the sensory properties of wine. We introduce a novel application of formal concept lattices, in combination with traditional statistical tests, to visu...
Article
Husk scald is a physiological rind disorder that manifests during storage and commercial shipping of pomegranate fruit. Scald affects the external quality thereby reducing its marketability, causing major economic loss to the industry worldwide. The lack of understanding of the underlying physiological and biochemical mechanisms of this disorder hi...
Article
Fourier transform near infrared (FT-NIR) diffuse reflectance spectroscopy as a non-destructive method for the development of calibration models has been investigated as a means of assessing the quality of whole pomegranate fruit. FT-NIR diffuse reflectance spectrometers with different spectral acquisition modes were evaluated using direct contact b...
Article
The wine industry requires reliable methods for the quantification of phenolic compounds during the winemaking process. Infrared spectroscopy appears as a suitable technique for process control and monitoring. The ability of Fourier transform near infrared (FT-NIR), attenuated total reflectance mid infrared (ATR-MIR) and Fourier transform infrared...
Article
Full-text available
The use of non-Saccharomyces yeasts to improve complexity and diversify wine style is increasing, however, the interactions between non-Saccharomyces yeasts and lactic acid bacteria (LAB) have not received much attention. This study investigated the interactions of seven non-Saccharomyces yeast strains of the genera Candida, Hanseniaspora, Lachance...
Conference Paper
Of the white wine cultivars grown in South Africa, Chenin blanc is planted the most. Ironically, three times more Sauvignon blanc – a much lesser cultivated grape - is sold locally per 750 ml bottle. Why the most cultivated white wine, which is part of South Africa’s rich wine heritage, is lesser preferred, is a mystery and motivated this explorati...
Article
Phenolic compounds play and important role on colour, flavour and mouthfeel attributes of wines. The acquisition of information related to phenolic compounds during the winemaking process is therefore becoming a necessity. Ultraviolet-Visible (UV-Vis) spectroscopy appears as an affordable option to monitor phenolic composition and levels during win...
Article
Full-text available
This article provides an overview of perceived risk during wine decision-making, highlighting the value and previous international successes of consumer-driven marketing initiatives, while providing direction for future research on the local market.
Article
A Fourier transform NIR (FT-NIR) method was developed combining chemometrics for prediction of organoleptic and phytochemical parameters of pomegranate arils using two different FT-NIR acquisition methods; namely, an integrating sphere (IS) and an emission head (EH) used over a spectral region 800–2500 nm. Several pre-processing methods were invest...
Article
Phenolic compounds are of crucial importance for red wine colour and mouthfeel attributes. A large number of enzymatic and chemical reactions involving phenolic compounds take place during winemaking and aging. Despite the large number of published analytical methods for phenolic analyses, the values obtained may vary considerably. In addition, the...
Article
Phenolic compounds are of crucial importance for red wine color and mouthfeel attributes. A large number of enzymatic and chemical reactions involving phenolic compounds take place during winemaking and aging. Despite the large number of published analytical methods for phenolic analyses, the values obtained may vary considerably. In addition, the...
Poster
Full-text available
Sorting in combination with quality scoring as a tool to identify drivers of wine quality Wine quality and style, as perceived by winemakers, are important considerations for choosing a target market as well as future product development. Linking wine style to quality is only possible if the sensory characteristics as well as a quality score is me...
Presentation
Full-text available
Consumer preference for fruit without disorder influence purchase of fruit at both local and international markets. Recent trends in horticulture show that consumer preference is influenced by assurance that external appearance is linked with rewarding internal sensory quality. Therefore, the need for non-destructive evaluation of external and inte...
Conference Paper
From a consumer behaviour perspective, the South African wine market is under-explored as much of extant research seems to focus on viticultural and wine-making aspects. However, understanding and reaching a consumer market effectively should be as important as producing quality wine. This presentation aims to demonstrate the value of consumer rese...
Conference Paper
Full-text available
Consumers can perceive significant amounts of risk when deciding to purchase a bottle of wine. Perceived risk can be defined as the uncertainty of possible negative consequences, such as dissatisfaction with the choice upon tasting the wine, or embarrassment as a result of the purchase. On the risk continuum of food and beverage decisions, wine is...
Article
The introduction of controlled amounts of oxygen into red wines influences the composition of the phenolic substances and volatiles, and therefore the sensory properties of the wines. The main aim of this study was to evaluate the impact of a simulation of the micro-oxygenation technique through acetaldehyde addition, on colour, and on the composit...
Poster
Full-text available
This work reports on a collaborative project between industrial and research partners in South Africa to adapt the small bench-top Alpha-P FTIR-ATR spectrometer (Bruker Optics), to quantitation of quality determining parameters in grape juice, fermenting must and wine. We report on results that evaluate the performance of the instrument for quantit...
Poster
Full-text available
Organic acids are related to the pH, mouth-feel, microbial and physiochemical stability. They constitute protection against oxidation for phenolics. Organic acids have an important influence on the aroma of wine.
Poster
Full-text available
This simple method can be used for monitoring the evolution of acids during winemaking. The short analysis time allows for the testing of large number of samples. Combining the ample amount of results with statistical analysis can lead to a comprehensive study about the characterization of South African wines.
Poster
Full-text available
Polyphenolic compounds came into the spotlight recently due to their antioxidant properties. In human health these compounds, numbering over 4000 distinct species, are thought to be instrumental in combating oxidative stress, a syndrome causative of some neurodegenerative diseases and some cardiovascular diseases. For example, over sixty different...
Article
The impact of pre-fermentative cold soak, alone or in combination with dry ice addition, on colour, phenolic and volatile composition of Tempranillo wines at 12 months after bottling was studied. A control wine without cold soak was also evaluated. A sample set consisting of 66 wines was investigated. The results from ANOVA and PCA analysis showed...
Article
Full-text available
Yeast cells possess a cell wall comprising primarily glycoproteins, mannans and glucan polymers. Several yeast phenotypes relevant for fermentation, wine processing and wine quality are correlated with cell wall properties. To investigate the effect of wine fermentation on cell wall composition, a study was performed using mid-infrared (MIR) spectr...
Article
The volatile and phenolic composition of Chenin blanc wines made with different skin contact treatments was studied. One batch of grapes was used to make a dry white wine according to two different treatments, namely pre-fermentative skin contact and complete fermentation on the skins. A white wine fermented without any skin contact was used as con...
Article
The validation of ultraviolet-visible (UV-VIS) spectroscopy combined with partial least squares (PLS) regression to quantify red wine tannins is reported. The methylcellulose precipitable (MCP) tannin assay and the bovine serum albumin (BSA) tannin assay were used as reference methods. To take the high variability of wine tannins into account when...
Article
Fructooligosaccharides (FOS) are popular components of functional foods produced by the enzymatic transfer of fructose units to sucrose. Improving β-fructofuranosidase traits by protein engineering is restricted by the absence of a rapid, direct screening method for the fructooligosaccharide products produced by enzyme variants. The use of standard...
Article
Short-chain fructooligosaccharides (scFOS) are valuable health-promoting food additives. During the batch production of scFOS from sucrose the β-fructofuranosidase catalyst is subject to product inhibition by glucose. Engineering the enzyme for reduced sensitivity to glucose could improve product yields or process productivity while preserving the...
Article
Full-text available
Rapid descriptive sensory profiling methods are under active exploration in the field of sensory science. Methods such as projective mapping, sorting and Napping® are considered time and cost-effective alternatives to conventional descriptive profiling for generating sensory product maps. In this study, the feasibility of applying rapid sensory pro...
Article
Projective mapping has been validated as a practical tool for the rapid sensory profiling of brandy prod- 32 ucts, although repeatability concerns necessitate repeated measurements in larger sample sets. The rea- 33 son for poor repeatability could be linked to the complexity of the product type, as well as the physical 34 and possibly psychologica...
Article
Full-text available
The development of rind breakdown disorder (RBD) of ‘Nules Clementine’ mandarins (Citrus reticulate Blanco) limits postharvest storage capability and causes commercial losses. In this study, the use of diffuse reflectance Vis/NIR spectroscopy in the wavelength range of 350-2500 nm was explored as a non-destructive tool to predict susceptibility to...
Article
This research was conducted to examine the relationships between fruit position in the canopy, limited light by fruit bagging, rind biochemical composition and susceptibility of ‘Nules Clementine’ mandarin to rind breakdown disorder (RBD) during storage. A secondary aim of this study was to explore diffuse reflectance visible and near infrared spec...
Conference Paper
Robustness of calibration models has become a critical issue in visible to near infrared spectroscopy (Vis/NIRS) and an active area of research in postharvest technology. An important consideration in developing fruit spectral and model libraries is to ensure that calibration data sets represent variability of target prediction samples. A way to ac...
Article
Malolactic fermentation (MLF) mediated by lactic acid bacteria (LAB) has been shown to modulate chemical and sensory attributes of wine. This study investigated the relation between consumer liking, chemical and sensory attributes of Vitis vinifera L. cv. Pinotage wines that were made over two vintages by four different lactic acid Oenococcus oeni...
Article
3-AIkyl-2-methoxypyrazines are important aroma components in Sauvignon blanc wine, contributing to the typical vegetative character associated with the cultivar. The analysis of methoxypyrazines is highly challenging and, as a result, limited quantitative data are available for South African Sauvignon blanc wines. In this study, liquid chromatograp...
Conference Paper
Full-text available
Background: External and internal quality is an important aspect in the fruit industry. In recent years, consumers have become increasingly aware of the importance of quality. As a result of socioeconomic changes, the concept of quality is continuously evolving. Therefore, there is an increasing need in the main fruit producing countries to rapidly...
Article
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 obta...
Article
Colour and phenolic content of red grapes are two of the most important constituents required to produce a quality red wine. In the Robertson grape growing area, difficulty is sometimes experienced with colour development of grapes. This is especially linked to location and most probably greatly influenced by season. Forty four vineyard blocks of t...