Pre-fermentation Wine Treatments & Techniques Presented by Stephen Skelton MW
Units of measurement - Area 1 hectare (ha) =10,000 000 square metres I hectare = approx. 2.47 acres 1 are = 100 square metres 1 acre = 43,560 sq. ft., 4,840 sq. yds. or approx. 4,047 sq. m.
Units of measurement- Weight I kilogram (kg) = weight of 1 litre water 1 tonne = 1000 kilograms 1 ton (UK) = 2240 lbs or approx. 1016 kg 1 ton (US) = 2000 lbs or approx. 907 kg
Units of measurement- Volume I litre = 1/1000 th of a cubic metre 1000 litres = weight of 1000 kg of water at sea-level at 20 C. 1 hectolitre (hl) = 100 litres
Units of measurement - Yield 1 tonne per hectare = approx. 7 hl/ha when grapes fully pressed. I tonne per acre = approx. 17 hl/ha
+ acids + flavours + colour + water = wine
Primary constituents of grapes and grape juice Sugars glucose & fructose Acids tartaric & malic, mainly in flesh Mineral salts potassium Polyphenols tannins, skins, stems & pips Flavour compounds cells near skin Proteins & colloids throughout grape
Determination of picking date Sugar content predicts alcohol level and degree of ripeness. Field readings practical. Acidity can be tasted. Physiological ripeness look, feel and taste. Very winemaker/wine style dependent.
Sugar measurements Relative density (RD) not specific gravity Babo (same as KMW) Brix (Ballung) Baumé Oeschle (OE) Klosterneuburg degrees (KMW)
Concentration of grapes Freezing natural ice wine Freezing artificial Noble rot pourriture noble natural or artificial Drying Vin Santo, Vin de Paille etc Passerillage dehydration on the vine
Control of oxidation SO2 -at picking, iki crushing or pressing Cooling night harvesting, refrigeration Dry Ice frozen CO2 at -78.5 C Clean grapes selection (triage)
Skin contact white grapes None whole bunch pressing None de-stem, crush and press De-stem, crush and drain De-stem, crush and soak
Skin contact red grapes None usually only for sparkling Partial for rosé wines Complete typical red fermentation
Thermovinification Grapes de-stemmed, crushed & heated to 65-75 C through heat exchanger. Roto-fermenter Rototank, Vinomatic. i
Flash détente (rapid expansion under vacuum) De-stalked, crushed grapes heated to 85-90 C and subjected to a vacuum. Water is instantly sucked out & grapes explode releasing more flavour & phenolics. G l t 35 C d th t t d i Grapes cool to 35 C and are then treated in usual way.
Flash détente
Flash détente
Saignée (bleeding) Proportion of juice (10-20%) is bled off for production of rosé wine Remainder is fermented normally to produce a fuller bodied wine
Pressing techniques Vertical basket presses
High pressure Clean juice Labour intensive Slow throughput
Pressing techniques Vaslin horizontal hydraulic screw press Easy to load/unload, cloudy juice
Willmes horizontal pneumatic press. Low pressure, clean juice.
Willmes tank press
Pressing techniques Continuous membrane (belt) presses usually only found in wineries i with large throughput.
Pressing techniques Continuous (Archimedes) screw presses. Usually only suitable for bulk wines and for extracting maximum output from red fermentation residues
Settling (débourbage) Clean juice is preferable for clean ferments. Juices usually settled for 24 hrs, although h 48-72 not uncommon when cooling & space available. Longer settling time has big impact on tank space. Pre-fermentation battonage with the use of a lees snake.
CROSS-FLOW MICROFILTRATION Pressure Feed Concentrate Polarization concentration Membrane Cake Pore blocking Internal adsorption Permeate 5/20
Juice clarification - RDV filter Rotary Drum Vacuum Filter for continuous clarification of very dirty juice, lees, tank bottoms
Centrifuge
Juice clarification - Flotation Flotation systems for large- ag scale wineries
Sweetening - enrichment, chaptalisation Alcohols can be increased by sweetening musts within certain limits. Sucrose usual product used, although concentrated grape must (CGM) and RCGM (Rectified CGM) also used. Around 16.5 grams sucrose required for 1% in 1 litre.
Sweetening - enrichment, chaptalisation EU limits enrichment to +3.5% in Zone A and +2% in Zone B. An additional 1% allowed in certain years. Sugar additions only allowed once per fermentation. Careful measurements required for reds.
Must concentration Cryo-extraction (freeze concentration). Reduction of water content by forming ice and removing it. Subject to limits in EU. Reverse osmosis - removal of water by filtration through membranes under pressure. Also used on wine for alcohol & volatile acidity reduction and removal.
Cryo-extraction (freeze concentration)
Reverse osmosis
Reverse osmosis
Acidification of must Lowers ph, increases acidity, improves balance, aids SO2 effectiveness, increases life of wine. De-acidification of must Improves balance of wine Must dilution Reduction of alcohol content
Enzymes - Improve yield rates at pressing - Better flavours in aromatic varieties - Release of terpenols - Glycerol levels raised for better mouth-feel - Tannins & polyphenols softened - Btt Better extraction ti of tannins, colours & flavours for long lasting reds - Preventing growth of malo-lactic bacteria
Fining - Bentonite removes proteins - Enzymes - Pectinolytic for breaking down pectins - Beta-glucanase for botrytis infected grapes - Lysozyme for controlling lactic acid bacteria - Charcoal for tainted t grapes: moulds, frost - PVPP (Polyvinylpolypyrrolidone) controls ( y yp ypy ) astringency, browning, off-flavours
Hyperoxidation Deliberate oxidation of juice to reduce later SO2 content, improve colours & increase keeping potential Filtration Rotary Drum Vacuum (RDV) filter used on tank bottoms, settlings & juice lees. Also on juices that have been treated. Pasteurisation Aids clarification, reduces enzyme use & improves fruit flavours.