The purpose of the chemical and physical study of vinegars is to verify the basic product composition and to perceive its complex evolution during the aging process; both determinant aspects for appreciation of sensory organoleptic qualities.
The chemical-physical identification of “Sopraffino degli Estensi” and “Sopraffino Riserva” vinegars entails a long and complex process which comprises some phases featuring intense biologic activity and other phases that principally involve refinement in wooden barrels, which results in product concentration and natural product burnishing.
As specified for example in the graph below, the evolutionary dynamics of “Sopraffino” vinegar refined by ageing of the 2003 vintage show an initial, intense biologic development phase activated by the acetobacteria that are capable of increasing initial acidity levels up to over 30% during the first year. Over the following years, biologic activity slows down whilst the degrees Brix (dissolved sugar-to-water mass % of a liquid, measured with a refractometer) increase, which results in phenomena such as evaporation, transpiration, salification, esterification and many other phenomena that are still in study phases.
One of the effects that is directly correlated to the above processes is an increased product density, although this property is certainly of minor interest in as far as product quality goes. During refinement and ageing, the effect of the numerous phenomena already mentioned lead to a definitely more important evolution of the physical properties of the product and of the product’s sensory profile.
If we do in fact compare the sensory profile of a product at its fifth year of ageing, it will be completely different compared to initial evaluations and will show a marked increase of tertiary aromas and gradual loss of the fruity flavour typical of boiling musts.
What can be noted here is the clean-cut separation between the two product profiles. It is also easier to identify the sensory features more involved with refinement and ageing such as persistence, which is the overall complex flavours enveloping tongue and palate for a good many seconds (15”-20”), the tanninic sensation, which is the typically astringent and puckery sensation on the tongue and finally the spiciness, which mostly concerns the interaction with the various wood types during barrel ageing.
As already mentioned, the product’s physical properties also undergo an important evolutionary process. In fact, increased concentrations of soluble solids lead to increased product density. But the particular conditions occurring during the traditional grape refinement and ageing techniques of the House of Este make it so that product density also involves the formation of stable chemical compounds, with the formation of organic acid salts and complex esters and polymers. The analytic confirmation of these observations is given by the dry extract value minus the sugar contents. This parameter is a synthesis of all the molecules present in the product (minus the sugar contents) subject to the chemical changes specified under the refinement and ageing process. If the average grape must values (lying around 20 g/l) are compared with finished product values, significant increases of net, dry extract levels reaching values of over 100 g/l can be noted.
The combination of these substances make it so that the increase in density is followed by an increase in product viscosity, with enhanced visual and taste-tactile sensations.
In as far as visual product perception is concerned, it must be noted how the mellow brown colour is the result of the sugar’s natural reactions that take place gradually throughout the summer months. Making caramel additives (type E150 a,b,c,d), a widespread technique in current industrial processes, totally unnecessary.
Acid-density ratio between appreciation and trends
The high acidity levels recorded by “Sopraffino” vinegar and the inexistence of the high sugar concentrations that are currently very much the fashion are an additional guarantee that the product does not have the common problems involving vinegar crystallisation.
Sulphate Testing Analysis
