Terroir 2004 banner
IVES 9 IVES Conference Series 9 The use of epifluorescence versus plating to monitor the effect of different parameters on microorganisms in wine

The use of epifluorescence versus plating to monitor the effect of different parameters on microorganisms in wine

Abstract

The monitoring of the number of micro-orgranisms in wine is crucial for the wine producer. Traditional counting methods include microscopic enumeration and plating on selective media, which measures the culturability of the cells. The use of epifluorescence microscopy is, however, a method, which can measure both culturability and viability in wine. This method distinguishes between live and dead cells. Research showed that little difference existed between plating and epifluorescence numbers to enumerate lactic acid bacteria in wine. However, a difference exists between these two methods to distinguish between acetic acid bacteria numbers in wine. Plating counting numbers were lower than plate numbers for Acetobacter pasteurianus in wine under anaerobic conditions. This difference was, however, negated by the addition of oxygen to the wine. SO2 additions lowered the culturability of A. pasteurianus at dosages higher than 0.35mg/L molecular SO2, but higher dosages were required to lower epifluorescence intensity, which is an indication of viability. Brettanomyces bruxellensis culturability was inhibited at lower dosages, but total cell numbers according to epifluorescence microscopy were affected at higher molecular SO2 dosages. Epifluorescence microscopy and plating also showed that B. bruxellensis was drastically affected after 120 min after molecular SO2 addition and it’s culturability after only 30 min. An exposure time of 5 min to molecular SO2 reduced the cell’s viability drastically and 45 min completely inhibiting the viability after two days. The bonded form of sulphur dioxide did not affect both micro-organisms. Epifluorescence microscopy can thus be used as a quick alternative to assess micro-organisms numbers and culturability in wine. This technique has both advantages and disadvantages over traditional enumeration methods, which will also be discussed.

DOI:

Publication date: January 12, 2022

Issue: Terroir 2004

Type: Article

Authors

W.J. du Toit (1), I.S. Pretorius (1,2) and A. Lonvaud-Funel (3)

(1) Department of Viticulture and Oenology, Institute for Wine Biotechnology, Stellenbosch University, Victoria Street, ZA 7600 Stellenbosch, South Africa
(2)The Australian Wine Research Institute, Waite Road, Urrbrae, SA 5064 Adealide, Australia
(3) Faculté d’Oenologie, 351, Cours de la Libération, 33405 Talence, France

Contact the author

Tags

IVES Conference Series | Terroir 2004

Citation

Related articles…

Effect of biological control agents on grapevine rhizosphere microbiome and grapevine defenses

Plant diseases are a major obstacle to crop production. The main approaches to battle plant diseases, consist of synthetic chemicals to attack infecting pathogens. However, concerns are increasing about the effects of chemicals in the environment, leading to an increase in the use of biocontrol agents (BCAs), due to their assets, such as, antagonism, and competition. In this study, we tested the hypothesis that the introduction of Bacillus subtilis PTA-271 (Bs PTA-271) and Trichoderma atroviride SC1 (Ta SC1) produce distinctive modifications in the composition and network structure of the grapevine rhizosphere microbial community, as well as grapevine induced defenses.

On the stability of spectral features of four vine varieties in Brazil, Chile and France

Satellite images of vineyards in France, Chile, and Brazil are used to study spectral differences between the vine varieties Cabernet Sauvignon, Merlot, Pinot Noir, and Chardonnay, to verify if features of a given variety are conserved at vineyards in completely different terroirs.

Prediction of sauvignon blanc quality gradings with static headspace−gas chromatography−ion mobility spectrometry (SHS−GC−IMS) and machine learning

The main goal of the current study is the development of a cost-effective and easy-to-use method suitable for use in the laboratory of commercial wineries to analyze wine aroma. Additionally, this study attempted to establish a prediction model for wine quality gradings based on their aroma, which could reveal the important aroma compounds that correlate well with different grades of perceived quality METHODS: Parameters of the SHS−GC−IMS instrument were first optimized to acquire the most desirable chromatographic resolution and signal intensities. Method stability was then exhibited by repeatability and reproducibility. Subsequently, compound identification was conducted. After method development, a total of 143 end-ferment wine samples of three different quality gradings from vintage 2020 were analyzed with the SHS−GC−IMS instrument. Six machine learning methods were employed to process the results and construct a quality prediction model. Techniques that aim to explain the model to extract useful insights were also applied.

SIP and save the planet: a sensory and consumer exploration of australian wines made from potentially drought-tolerant white wine grapes

In order to attenuate the effects of climate change on the ability to cultivate quality wine grape vines in Australia, it is essential to adapt to the projected less favourable Australian climate scenarios. One response may be to convert a portion of the current grapevine plantings to those varieties that demand less water and can tolerate increased heat. This investigation aimed to (i) generate sensory profiles and (ii) obtain knowledge about Australian wine consumers’ preferences and opinions of Australian wines made from potentially drought tolerant, white wine grape varieties not traditionally cultivated in Australia. A Rate-All-That-Apply (RATA) sensory panel (n = 49) generated sensory profiles of 44 commercial white wines made from 7 different white grape varieties (Arinto, Fiano, Garganega, Greco, Verdejo, Verdelho and Vermentino), plus two benchmark examples each of an Australian Riesling, Pinot Gris and Chardonnay wine.

Functional characterisation of genetic elements regulating bunch morphology in grapevine

Vitis vinifera L., is considered one of the world’s most important cultivated fruit crops. In agriculture, bunch morphology is a grapevine-specific trait, which directly impacts fruit quality and health.
Bunch size, shape, and compactness are major aspects of bunch morphology, with the degree of compactness emerging as an important trait for grapevine genetic enhancement and vineyard management. The importance of this trait stems from its impact on disease susceptibility, berry ripening, and other grape quality properties. However, current knowledge of the genes controlling it remains limited.