Resumen de Microbiological stabilisation of grape musts and wines by high hydrostatic pressures
C. Delfini, L. Conterno, G. Carpi, P. Rovere, A. Tabusso, C. Cocito, A. Amati
High hydrostatic pressure (up to 1000 MPa) is a new microbiological stabilisation process that can contribute to wine and grape must stabilisation. Experiments on grape must and wine microbiological stabilisation using high pressures were undertaken. A high pressure pilot plant mod. QFP6 of the ABB (Asea‐Brown‐Boveri) Society (Sweden) working up to 900 MPa was used. Flexible polyethylene bags (20–50 ml sample volume) were immersed in water contained in a 1‐l treatment steel cylinder. Different pressures (300–900 MPa) were tested, combined with different oenological conditions (pH, content of alcohol, SO2, sugars and acetaldehyde) both with must and wine added with 106 cells per millilitre of each of 13 wine yeast species, 1 Leuconostbc oenos, 1 Lactobacillus sp., 1 Acetobacter and 1 Botrytis cinerea as vegetative and sporified cultures. Micro‐organism inhibition and organoleptic consequences were determined. The results show that all the micro‐organisms added to a Moscato wine (8.22% alcohol, 50.5g l‐1 residual sugars, 146mg l‐1 acetaldehyde, pH3.0 and 3.5, 64 mg l‐1 SO2) were killed in 2 min with pressurisation at 400 MPa and an initial temperature of 20°C. In contrast, in a Barbera grape must (pH 3.0, sugars 177.2 gl‐1, without SO2, ethyl alcohol totally absent) at 600 MPa there were some survivors of Schizosaccharomyces pombe. Samples of Asti Spumante sparkling wine were treated at 600 MPa for 2 min in comparison with an equal series of untreated samples. After 6 and 24 h and 10, 20, 40 and 90 days, pressurised and control samples were analysed for dissolved oxygen content, colour intensify and tonality, and tasted for organoleptic quality. Notwithstanding a stronger decrease of dissolved oxygen found after 6 h in pressurised samples after 5 min from air injection, no significant taste and olfactor differences were observed between control and pressurised samples after 90 days of anaerobic storage.
