NEW ENZYMATIC KIT FOR MAGNESIUM ASSAY ON WINE AND MUST
In buffered environment, magnesium ions activate a selected enzymatic chain, producing a chromophore which absorbs at 340 nm. Measuring the enzyme's activity is possible to calculate the magnesium concentration into the sample. Interferences from other metals are deleted by using this selected enzymatic chain.
NEW ENZYMATIC KIT FOR TOTAL POLYPHENOLS ASSAY ON WINE AND MUST
In a buffered reaction environment, the total polyphenols of sample in presence of the enzyme Polyphenol Oxidase react with a selective chromogen, producing a cromophore whose intensity is proportional to the total amount of polyphenols.
This new enzymatic method doesn't affect from the interferences present on Folin-Ciocalteus method. This assay is no time consuming, in fact the end point reaction is completed within 5 minutes.
NEW ENZYMATIC KIT FOR REDUCED GLUTATHIONE ASSAY
Reduced glutathione (GSH) is a particular tripeptide non-protein source (not derived, in fact, from the degradation of proteins) formed from glutamic acid, cysteine and glycine. It is characterized by the unusual peptide bond which participates in the γ-carboxyl group of glutamic acid (in place of the α-carboxylic acid) which gives it greater stability.
It is a natural constituent widely used in animal and plant kingdom (Friedman, 1994). This tripeptide is a powerful antioxidant, prevents the formation of free radicals, plays an important role in maintaining the redox potential of the cells and in the process of detoxification through the binding of toxins, metals, organic solvents and pesticides (Meister, 1994).
Allows plants to survive the oxidative stress caused by cold, parasites and wounds (Dufourcq, 2006). The addition of fruit juices of peptides or amino acids, to prevent them browning and deterioration of their aromas, was built and successfully tested a long time (Molnar-Perl and Friedman, 1990; and L. Naim, 1993, 1997).
Such as fruit juices, some dry white wines can manifest, in the course of their aging, changing a defective aromatic note, in the case of wines, such as atypical aging (ATA) which is characterized by the loss of aromas and flavors in the appearance of heavier reminiscent of wax or mothballs. This premature aging of dry white wines is accompanied, almost always, by a modification of their color and, in particular, by an increase in yellow-orange shades (Dubordieu, Lavigne-Cruege, 2003).
The must is put in fermentation, contains numerous polyphenols, including the cinnamic acids that can be easily oxidized in idrossicinnammati (Figure 2), in particular derivatives of caffeic acid (caffeoil-tartaric acid and cumaroil-tartaric acid) and associating between them seem to be the origin of dell'imbrunimento must, first, and wine in the bottle later. In musts or white wines like Sauvignon Blanc and the Colombard (two qualities of French wines produced from grapes of Bordeaux origin), caffeic quinone react with thiols those responsible for the particular aroma of these wines, two of which are 3-mercapto -hexanol (3MH) connected to the aroma of grapefruit, citrus and exotic fruit, and the acetate of 3-Mercapto-hexyl (A-3MH) reminiscent of tropical fruit, producing a loss of aromatic potential.
The glutathione can block these two processes, browning and loss of aroma, since it reacts with quinone to form the GRP (Grape Reaction Product: trans-2-S glutationil caffeoil tartaric acid), soluble and colorless (Singleton et al., 1984; 1985; Cheynier et al., 1986 Dudley & Hotchkiss, 1989; Vaimakis, 1995). Furthermore, it was shown that glutathione protects not only the A-3MH and 3MH but also the origin of their formation: during the process of producing white wines the hexan-1-ol and form a GSH adduct which is the S-3-(hexan-1-ol)-glutathione, which is catabolised, then, in S-3-(hexan-1-ol)-L-cysteine, compound odorless, in this state, and the precursor of 3-mercaptoesanolo that, when released, provides the aromatic characteristics described above (Du Toit, 2007). During fermentation, a part of the 3MH is acetylated by another enzyme reaction producing the A-3MH. These two compounds have been identified in many wines not only white but also red and rosť (Dufourcq, 2006).
Glutathione also seems to be related to the prevention of removal, when the wines are exposed to air of volatile terpene alcohols such as linalool and the 'α-terpineol, two very important primary aromas (Du Toit, 2007).