Infrared spectroscopy and chemometric applications for the qualitative and quantitastive investigation of grapevine organs.

[EN] 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 have reported its feasibility. This review examines near infrared and mid infrared spectroscopy for the qualitative and quantitative investigation of intact grapevine organs. Qualitative applications, with the focus on using spectral data for categorization purposes, is discussed. The quantitative applications discussed in this review focuses on the methods associated with carbohydrates, nitrogen, and amino acids, using both invasive and non-invasive means of sample measurement. Few studies have investigated the use of infrared spectroscopy for the direct measurement of intact, fresh, and unfrozen grapevine organs such as berries or leaves, and these studies are examined in depth. The chemometric procedures associated with qualitative and quantitative infrared techniques are discussed, followed by the critical evaluation of the future prospects that could be expected in the field.The authors gratefully acknowledge the Oppenheimer Memorial Trust. A local scholarship (OMT Award Ref. 21579/01) was awarded to EW.Wyngaard, EV.; Blancquaert, E.; Nieuwouldt, H.; Aleixandre Tudo, J. (2021). Infrared spectroscopy and chemometric applications for the qualitative and quantitastive investigation of grapevine organs. Frontiers in Plant Science. 12:1-16. https://doi.org/10.3389/fpls.2021.7232471161

The Role of UV-Visible Spectroscopy for Phenolic Compounds Quantification in Winemaking

Phenolic compounds are bioactive substances present in a large number of food products including wine. The importance of these compounds in wine is due to their large effect on the organoleptic attributes of wine. Phenolic compounds play a crucial role in the colour as well as mouthfeel properties of wines. UV-visible spectroscopy appears as a suitable technique for the evaluation of phenolic compounds’ properties and content. The ability of the phenolic ring to absorb UV light and the fact that some of the phenolic substances are coloured compounds, i.e. show absorption features in the visible region, make UV-visible spectroscopy a suitable technique to investigate and quantify grape and wine phenolic compounds. A number of analytical techniques are currently used for phenolic quantification. These include both simpler approaches (spectrophotometric determinations) as well as more complex methodologies such liquid chromatography analysis. Moreover, a number of spectroscopy applications have also been recently reported and are becoming popular within the wine industry. This chapter reviews information on the UV-visible spectral properties of phenolic compounds, changes occurring during wine ageing and also discusses the current UV-visible based analytical techniques used for the quantification of phenolic compounds in grapes and wine

A chemometric approach to the evaluation of the ageing ability of red wines

CITATION: Aleixandre-Tudo, J. L. & du Toit, W. 2020. A chemometric approach to the evaluation of the ageing ability of red wines. Chemometrics and Intelligent Laboratory Systems, 203. doi:10.1016/j.chemolab.2020.104067The original publication is available at https://www.sciencedirect.com/journal/chemometrics-and-intelligent-laboratory-systemsOne of the most important quality attributes of red wines is its ability to withstand and ageing process. The multidimensionality of the ageing ability concept, which includes a combination of colour, taste, mouthfeel, and aroma was reported in previous studies. Phenolic compounds are largely or partially involved in most of these wine attributes and have been proposed as potential candidates to evaluate the ageing ability of red wines. The phenolic and colour properties of a large number of wines were measured during a barrel and bottle ageing process of 24 months. To our understanding, a wine that needs the longest time to reach optimal phenolic quality is considered a wine with higher ability to age (concentration assumption). Moreover, a wine that is able to maintain its optimal phenolic quality for longer will also be a wine with high ageing ability (stability assumption). Based on the formulated assumptions a scoring system was used to identify those wines with theoretically high ability to age. As expected, these wines contained initial high levels of tannins, total phenols and anthocyanins, including high polymeric pigment presence and enhanced colour properties. Interestingly, high ageing ability wines showed a smaller change in the colour properties over time which might be indicating slower pigment formation rates. In addition, a chemometric attempt was undertaken to explore an ageing index based on initial phenolic content. The evolution of the index over time using a multi-block approach showed stability for the index values, in line with the short term stability of tannin and total phenol levels. Finally, promising results were obtained as two thirds of the wines were correctly classified when a validation task between the ageing index and the score values was attempted.https://www.sciencedirect.com/science/article/pii/S0169743919306409Publishers versio

Bibliometric and social network analysis in scientific research on precision agriculture

CITATION: Aleixandre-Tudo, J. L., et al. 2018. Bibliometric and social network analysis in scientific research on precision agriculture. Current Science, 115(9):1653-1667, doi:10.18520/cs/v115/i9/1653-1667.The original publication is available at https://www.currentscience.ac.inPrecision agriculture (PA) is used to improve agricultural processes. A better understanding of PA as well as the evolution of the research status through the available literature are reported and discussed in this study. The Web of Science (WoS) was used to obtain the research records under study. Indicators of scientific productivity, collaboration between countries and research impact were evaluated through a social network analysis. The keywords included in the publications and subject areas under which the research was published were also evaluated through subject analysis. A total of 2027 articles were analysed from 1994 to 2014. The most productive journals were ‘Computers and Electronics in Agriculture’ (n = 191) and ‘Precision Agriculture’ (n = 110). The most frequent keywords were ‘management’ (n = 243), ‘yield’ (n = 231), ‘soil’ (n = 198) and ‘variability’ (n = 190). The collaboration network showed the United States occupying a central position, in combination with some leading countries such as Brazil, Germany, People’s Republic of China, Canada, Australia and Spain. A steady increase in PA research was identified during the last decade, which was even more sharp between 2010 and 2014. The increased importance of PA research has recently led to the birth of specific journals such as Precision Agriculture. The increasing number of journals that publish articles related to the topics included in the WoS must also be considered. The network analysis identified a number of developed countries in the hotspot of international collaboration.https://www.currentscience.ac.in/php/toc.php?vol=115&issue=09Publisher's versio

Unravelling the complexities of wine: A big data approach to yeast assimilable nitrogen

Aim: Assimilable Nitrogen (YAN) has been identified as one of the main drivers of wine quality, influencing the production of various aromas and ensuring a successful fermentation to dryness. Due to the number of factors affecting YAN concentration and composition, paired with the complexities of yeast metabolism, more data is required to enable a comprehensive understanding of this important component of the grape juice matrix. The use of high throughput and information-rich techniques such as InfraRed spectroscopy can lead to a fast generation of a large amount of data. In addition, there is a possibility to maximise the information output of the generated data when combined with various descriptive and exploratory statistical techniques. Conclusion: Given the recent developments in the fields of analytical equipment and chemometrics, the review explores the possibility of a Big Data approach for the research of one of the most important and versatile grape juice parameters, namely YA

Partial least squares calibrations and batch statistical process control to monitor phenolic extraction in red wine fermentations under different maceration conditions

The extraction of phenolic compounds during maceration is of utmost importance in red winemaking. However, the monitoring of phenolic extraction is often hampered by analytical and statistical constraints. The aim of this study was to monitor phenolic extraction kinetics with the use of PLS phenolic calibrations and batch statistical process control. Eight batches of Cabernet Sauvignon and Shiraz grapes during alcoholic fermentation under different maceration conditions (pressing at 1/3rd, 2/3rd and end of fermentation) and punch down regimes (low vs. high frequency) were evaluated in the study. Cabernet Sauvignon appeared to be a more suitable cultivar for longer maceration conditions with increased tannin extraction observed. Similar trends were observed for punch down for both cultivars. The use of PLS calibrations and batch level modelling provided an enhanced interpretation and understanding of phenolic extraction during red wine fermentations

Unravelling the complexities of wine : a big data approach to yeast assimilable nitrogen using InfraRed spectroscopy and chemometrics

CITATION: Petrovic, G., Aleixandre-Tudo, J.-L. & Buica, A. 2019. Unravelling the complexities of wine : a big data approach to yeast assimilable nitrogen using InfraRed spectroscopy and chemometrics. OENO One, 53(2):107-127, doi:10.20870/oeno-one.2019.53.2.2371.The original publication is available at https://oeno-one.euAim: Assimilable Nitrogen (YAN) has been identified as one of the main drivers of wine quality, influencing the production of various aromas and ensuring a successful fermentation to dryness. Due to the number of factors affecting YAN concentration and composition, paired with the complexities of yeast metabolism, more data is required to enable a comprehensive understanding of this important component of the grape juice matrix. The use of high throughput and information-rich techniques such as InfraRed spectroscopy can lead to a fast generation of a large amount of data. In addition, there is a possibility to maximise the information output of the generated data when combined with various descriptive and exploratory statistical techniques. Conclusion: Given the recent developments in the fields of analytical equipment and chemometrics, the review explores the possibility of a Big Data approach for the research of one of the most important and versatile grape juice parameters, namely YAN.https://oeno-one.eu/article/view/2371Publisher's versio

Effect of skin contact before and during alcoholic fermentation on the chemical and sensory profile of South African Chenin Blanc white wines

CITATION: Aleixandre-Tudo, J. L., et al. 2015. Effect of Skin Contact Before and During Alcoholic Fermentation on the Chemical and Sensory Profile of South African Chenin Blanc White Wines. South African Journal for Enology and Viticulture, 36(3):366-377, doi:10.21548/36-3-969.The original publication is available at http://www.journals.ac.za/index.php/sajevThe 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 control. Fermentation on the skins and skin contact before fermentation led to significantly lower levels of terpenes, esters, acids and thiols, and the highest significant levels of alcohols and phenolic compounds. However, this effect was less pronounced in wines with skin contact before fermentation. Sensory analysis of all the experimental wines was also performed. The results showed a significant shift from the sensory attributes of fresh and tropical fruits of the control Chenin blanc wines towards riper fruit notes in the skin contact treatments. This observation was correlated with the length of the skin contact period. Possible reasons to explain the results observed in this study are discussed.http://www.journals.ac.za/index.php/sajev/article/view/969Publisher's versio

Spectrophotometric Analysis of Phenolic Compounds in Grapes and Wines

[EN] 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 existing scientific knowledge needs to be updated, but also critically evaluated and simplified for newcomers and wine industry partners. The most used and widely cited spectrophotometric methods for grape and wine phenolic analysis were identified through a bibliometric search using the Science Citation Index-Expanded (SCIE) database accessed through the Web of Science (WOS) platform from Thompson Reuters. The selection of spectrophotometry was based on its ease of use as a routine analytical technique. On the basis of the number of citations, as well as the advantages and disadvantages reported, the modified Somers assay appears as a multistep, simple, and robust procedure that provides a good estimation of the state of the anthocyanins equilibria. Precipitation methods for total tannin levels have also been identified as preferred protocols for these types of compounds. Good reported correlations between methods (methylcellulose-precipitable vs bovine serum albumin) and between these and perceived red wine. astringency, in combination with the adaptation to high-throughput format, make them suitable for routine analysis. The bovine serum albumin tannin assay also allows for the estimation of the anthocyanins content with the measurement of small and large polymeric pigments. Finally, the measurement of wine color using the CIELab space approach is also suggested as the protocol of choice as it provides good insight into the wine's color properties.Aleixandre-Tudó, JL.; Buica, A.; Nieuwoudt, H.; Aleixandre Benavent, JL.; Du Toit, W. (2017). Spectrophotometric Analysis of Phenolic Compounds in Grapes and Wines. Journal of Agricultural and Food Chemistry. 65(20):4009-4026. https://doi.org/10.1021/acs.jafc.7b01724S40094026652