The effect of Nitrogen and Sulphur foliar applications in hot climates

Tyrosol (TYR) and hydroxytyrosol (HYT) are bioactive phenols present in olive oil and wine, basic elements of the Mediterranean diet. TYR is reported in the literature for its interesting antioxidant, cardioprotective and anti-inflammatory properties. In wine, its concentration can reach values as high as about 40 mg/L
[Pour Nikfardjam et al. 2007] but, more frequently, this phenol – derived from yeast metabolism of tyrosine during fermentation – is present at lower levels, generally higher in red wines compared to whites. HYT was measured for the first time by Di Tommaso et al. [1998] in Italian wines – with maximum values of 4.20 mg/L and 1.92 mg/L for red and white wines, respectively – while definitely lower concentrations have been found later in Greek samples.

For several years, numerous studies aimed at limiting the use of SO2 in wines (thermal treatments, pulsed electric fields, microwaves …). Processes must be able to preserve the organoleptic qualities of wines with low energy consumption. In this context, ultraviolet radiations (UV-C), at 254 nm, are well known for their germicidal proprieties. In order to inactivate microorganisms in grape juice and wine without affecting the quality of the product, efficiency of UV-C treatment process should be optimized.

Wine is a solution containing abundant volatile compounds which contribute to their aroma. Many of them are produced by yeast as metabolism by-products. Different yeast strains produce different volatile profiles. The possibility of studying the evolution of volatile compounds during fermentation, using sampling methods that not alter the volume of fermentation media, is of great interest. In spite of this, non-invasive methods to monitoring the evolution of volatile profile during fermentation have been seldom used. The goals of this work were to use by first time the headspace sorptive extraction (HSSE) as non-invasive method to monitor the evolution of volatile profiles throughout alcoholic fermentation and to study the changes on volatile profiles produced by Saccharomyces cerevisiae and Lachancea thermotolerans during fermentation of a must with high sugar content.

All techniques usually used to assay proteins was not reliable in vegetable extract due to interferences with the components included in extracts like polyphenols, tanins, pectines, aromatics compounds. Absorbance at 280nm, Kjeldhal assay, Biuret and Lowry methods, Acid Bicinchonique technique and Bradford assay give the results depending on the composition of extract, on the presence or not of detergent and on the raw material (Marchal, 1995). Another difficulty in these extracts for the quantification of proteins comes from the large amount of water included in vegetable and the low concentration of proteins. Thus in red wines, proteins are usually not taken into account due to their low concentration (typically below 10 mgL-1) and to the presence of anthocyanis and polyphenols.

Copper and iron are known to substantially impact wine stability through oxidative, reductive or colloidal phenomena. However, the binding of metal ions to different wine components under wine conditions, and the impact of this binding on the ability of the metal ions to induce spoilage processes, is not well understood. This study surveyed a range of red and white wines for an understanding of the variability of broad metal categories within the wines. The techniques utilized included an electrochemical constant current stripping potentiometry technique (ccSP), and solid phase extraction (SPE) fractionation of wine with subsequent analysis of the metal content of each fraction by inductively coupled plasma – optical emission spectroscopy (ICP-OES).