Odabir vinskih kvasaca prema sposobnosti adsorpcije pigmenata

The aim of this research is to improve an existing low-cost and simple but consistent culturing technique for measuring the adsorption of grape skin pigments on yeasts, comprising: (i) growing yeasts in Petri dishes on chromogenic grape-skin-based medium, (ii) photographing the yeast biomass, (iii) measuring its red, green, and blue colour components, and (iv) performing the statistical analysis of the data. Twenty strains of Saccharomyces cerevisiae were grown on different lots of the chromogenic medium, prepared using grape skins from dark cultivars Greco Nero, Magliocco and Nero d’Avola. Microscale wine fermentation trials were also performed. Wide and significant differences among wine yeasts were observed. The chromogenic grape-skin-based medium can be prepared using any grape cultivar, thus allowing the specific selection of the most suitable strain of Saccharomyces cerevisiae for each grape must, mainly for red winemaking. The research provides a useful tool to characterize wine yeasts in relation to pigment adsorption, allowing the improvement of wine colour.Svrha je ovoga rada bila poboljšati jednostavnu i jeftinu metodu mjerenja adsorpcije pigmenata iz kožice grožđa na površinu kvasaca. Metoda se sastoji od sljedećih postupaka: uzgoj kvasaca u Petrijevoj zdjelici na kromogenoj podlozi što sadržava kožice grožđa; fotografiranje biomase kvasca; mjerenje crvene, zelene i plave komponente boje; te statistička obrada podataka. Uzgojeno je 20 sojeva kvasca Saccharomyces cerevisiae na različitim kromogenim podlogama, pripremljenim od kožica crnoga grožđa sorata Greco Nero, Magliocco i Nero d’Avola. Nakon mikrofermentacije primjećene su bitne razlike između vinskih kvasaca. Kromogena se podloga koja sadržava kožice grožđa može pripraviti od bilo koje sorte, pa se može odabrati najbolji soj Saccharomyces cerevisiae za svaki mošt, što je naročito važno u proizvodnji crnog vina. U ovom je istraživanju razvijena korisna metoda odabira vinskih kvasaca prema sposobnosti adsorpcije pigmenata, a radi poboljšanja boje vina

A Rain Estimation System Based on Electromagnetic Propagation Models and DVB-S Opportunistic Sensors

Weather conditions have in general huge impact on the global economy, in particular on agriculture, industry, transport, and so forth. In recent years, also the occurrences of rapid and localized heavy rainfall in complex topographic areas became more frequent, possibly due to global warming. These facts cause injuries and deaths, and an accurate and early alert system is required to warn people and operators. In this chapter, we describe a real-time and low-cost system for precipitation detection, aimed at collecting additional data with respect to those obtainable from traditional sensors. Such a system is based on the opportunistic usage of satellite digital video broadcasting (DVB-S) microwave signals and estimates the rain intensity from the detected attenuation. Our system proved to accurately obtain results comparable with rain gauges located in the experimentation area, with much tighter spatial and temporal scales than traditional schemes

Selection of Escherichia coli-inhibiting strains of Lactobacillus paracasei subsp. paracasei

The aim of this study was to select Escherichia coli-inhibiting strains among lactic acid bacteria. On the basis of phenotypical and technological characteristics, 20 strains of lactic acid bacteria were screened from a total of 225 isolates, obtained from nine samples of artisanal Caprino d'Aspromonte cheese, made from raw goats' milk. The antagonistic activity of these 20 strains was detected in plates against three different strains of E. coli. Two strains of Lactobacillus paracasei subsp. paracasei showed a marked anti-E. coli activity against all three strains tested; the other lactic acid bacteria did not exhibit inhibiting activity. The E. coli inhibition can be ascribed to production of bacteriocin-like compounds. The use of L. paracasei subsp. paracasei strains to increase the safety of the cheeses made from raw milk is recommended because these cultures strongly inhibit E. coli, without foreseeable adverse sensory changes

Effect of Protectants on the Fermentation Performance of Wine Yeasts Subjected to Osmotic Stress

During alcoholic fermentation of must from dried grapes, yeasts are subjected to very high sugar concentrations, besides other environmental stresses, and they modify their metabolic behaviour giving low ethanol yield and abnormally high acetic acid production. To investigate the protective effect of catechin, inositol, and SO2 on wine yeasts, three thermotolerant strains of Saccharomyces cerevisiae, selected for wine making of must from dried grapes, and three strains of Saccharomyces selected for the production of wine, were inoculated in a sample of must at very high osmotic strength. A significant (p<0.01 or p<0.05) relationship between the addition of 100 mg/L of catechin, inositol or SO2 to the grape must and the change in the metabolic behaviour of the yeasts was observed. Compared to the control and depending on strain and protectant, the fermentation rate after 3 days increased up to 55 %, the ethanol content of the wines increased up to 16 %, the unitary succinic acid production increased up to 55 %, the unitary acetic acid production decreased up to 53 %, and the unitary glycerol production decreased up to 69 %. So by adding catechin, inositol or SO2 to the grape must it is possible to minimise the abnormal fermentation performance that wine yeasts exhibit in wine making of must from dried grapes

In-vitro screening ofSaccharomyces strains for ochratoxin A removal from liquid medium

The aptitude of twentySaccharomyces sensu stricto strains to remove ochratoxin A from a synthetic medium containing 1.1 ng/mL, about half of the European Community limit, was evaluated using four to six mg of biomass (wet weight)/mL. Seven satins show high levels of ochratoxin A removal, 0.72-1.10 ng/mL, equivalent to 66–100% of the available toxin, and unitary removing ativity of 14.31–27.24 pg/mg of biomass. Further research will be carried out to study the mechanism of OTA removal and to confirm the ability of the most efficacious strains ofSaccharomyces sensu stricto to remove OTA from contaminated wort and grape must during alcoholic fermentation

Influence of Yeast on Polyphenol Composition of Wine

Two strains of Saccharomyces cerevisiae were employed for winemaking of must from red grapes. Twenty-two parameters were determined in the red wines produced. Very significant (p<0.01) differences were observed for colour intensity, total polyphenols, and non-anthocyanic flavonoids. Moreover, significant (p<0.05) differences were observed for colour and monomeric anthocyanins

Assessment of color adsorption by yeast using Grape Skin Agar and impact on red wine color

Aim: Evaluating Saccharomyces cerevisiae strains for their color adsorption aptitude by using Grape Skin Agar in order to protect the phenolic compounds responsible for the color of red wines; proposing a suitable and innovative medium to be included among the tests currently used for wine strain selection.Methods and results: The strains were identified by fluorescence-Internal transcribed spacer (f-ITS) PCR and PCR-Restriction fragment length polymorphism (RFLP), confirmed by sequencing of ITS fragment, and tested for the parameter "aptitude to adsorb polyphenolic compounds" on the innovative chromogenic medium Grape Skin Agar. Laboratory-scale fermentations were carried out in must with and without SO2. The SO2 determined a decrease in tint, color intensity, and total polyphenol content. The strains M2V CHU7 and M2F CHU9 produced wines with the lowest color intensity, with and without SO2, respectively. By contrast, the strains M2F VUP4 and M2V CHU1, with and without SO2, respectively, produced wines with the highest color intensity, and therefore, they could improve the production of red wines.Conclusion: The study highlights great variability and significant differences among strains in regard to their aptitude to modulate wine color. Grape Skin Agar should be a useful medium to be included in the selection tests currently performed for S. cerevisiae strains.Significance and impact of the study: Our study confirms that yeast strains can modulate the chromatic properties of red wines according to their aptitude to adsorb polyphenols, as tested on Grape Skin Agar. Combining colored polyphenolic compound adsorption assay on Petri plate and laboratory-scale fermentation trials provides an effective way to test yeasts for their capability to improve the chromatic quality of the wines

Selection of Wine Saccharomyces cerevisiae Strains and Their Screening for the Adsorption Activity of Pigments, Phenolics and Ochratoxin A

Ochratoxin A is a dangerous mycotoxin present in wines and is considered the principal safety hazard in the winemaking process. Several authors have investigated the ochratoxin A adsorption ability of Saccharomyces cerevisiae yeasts, and specifically selected strains for this desired trait. In the present work, a huge selection of wine yeasts was done starting from Portuguese, Spanish and Italian fermenting musts of dierent cultivars. Firstly, 150 isolates were collected, and 99 non-redundant S. cerevisiae strains were identified. Then, the strains were screened following a multi-step approach in order to select those having primary oenological traits, mainly (a) good fermentation performance, (b) low production of H2S and (c) low production of acetic acid. The preselected strains were further investigated for their adsorption activity of pigments, phenolic compounds and ochratoxin A. Finally, 10 strains showed the desired features. The goal of this work was to select the strains capable of absorbing ochratoxin A but not pigments and phenolic compounds in order to improve and valorise both the quality and safety of red wines. The selected strains are considered good candidates for wine starters, moreover, they can be exploited to obtain a further enhancement of the specific adsorption/non-adsorption activity by applying a yeast breeding approach

Long-term effects of different starter yeasts on colour and natural antioxidant power of red wines

AbstractEighty-seven red wines produced from red grapes of the grape variety Gaglioppo from the Calabria region (vintage 2009) were analysed by standard methods after 4 and 120 months of ageing. So, a total of 29 selected starters of Saccharomyces cerevisiae—3 wild type, 12 monoclonal cultures, and 14 hybrids—inoculated in triplicate were studied for their effects on colour and natural antioxidant power keeping of red wine. Wine ageing decreased the red component, the colour intensity, and the DPPH values while the colour hue values increased. This research has shown that the evolution of wine ageing is affected in a very different way by the starter yeast used and has allowed choosing the best yeast strain useful to produce red wine able to endure very long-time ageing, until 10 years

A field assessment of a novel rain measurement system based on earth-to-satellite microwave links

This work presents the performance of an innovative environmental monitoring system - Smart Rainfall System (SRS) - that estimates rainfall in real-time by means of the analysis of the attenuation of satellite signals (DVB-S in the microwave Ku band). SRS consists in a set of peripheral microwave sensors placed on the field of interest, and connected to a central processing and analysis node. It has been developed jointly by the University of Genoa, with its departments DITEN and DICCA and the University spin-off \u201cArtys Srl\u201d. The rainfall intensity measurements accuracy and sensitivity performance of SRS are discussed, based on preliminary results from a field comparison experiment at the urban scale. The test-bed is composed by a set of preliminary measurement sites established since Autumn 2016 in the Genoa (Italy) municipality and the data collected from the sensors during a selection of rainfall events is studied. Point-scale rainfall intensity measurements made by calibrated tipping-bucket rain gauges constitute the reference for the comparative analysis of the system performance. The dynamic calibration of the reference rain gauges has been carried out at the laboratories of DICCA using an automatic calibration rig and the measurements have been processed taking advantage of smart algorithms to reduce counting errors. Additional information about the spatial distribution of precipitation have been provided by the WSR radar of Monte Settepani. An objective of this investigation is the optimization of the specific attenuation model parameters for rain with respect to those recommended by the International Telecommunication Union standard ITU-R P.838-3. In addition, the experimental set-up allows a fine tuning of the retrieval algorithm and a full characterization of the accuracy of the rainfall intensity estimates from the microwave signal attenuation as a function of different precipitation regimes