Winemaking methods 35

Winemaking – 2006

Winemkaing in 2006 was carried out on grapes from the nitrogen by irrigation trial, and block A and block B Pinot Noir vigour trials. Fruit for the nitrogen by irrigation trial came from the two central measurement vines in each treated panel. Fruit in the vigour trials came from all four vines in a panel. Grapes were destemmed and transferred to a fermentation vessel (either a plastic 20 L buckets or 20 L stainless steel bucket), and potassium metabisulphite added to provide a free sulphur level of 60 ppm. Enzymes were added (Lafase HE, Laffort), prepared according to the manufacturer’s

recommendations.

Musts were allowed to warm up to at least 16 degrees prior to inoculation. Ferments were inoculated with 300 ppm RC212 yeast (Lalvin), prepared according to the manufacturer’s recommendations, including an acclimation step.

Cap management in 2006 used a punch-down system, with fermenters plunged twice a day using a potato masher and carrying out ten plunges at each session. Following the punching down, ferment temperature was recorded and density assessed by hydrometer. Fermentation was carried out in a heated insulated room, with fans being used to ensure temperature was constant throughout. Temperature was maintained at around 25°C, and were covered while not being plunged.

Fermentation proceeded until all ferments had a Baumé below 1, and then pressed. The press was a small basket press, with the pressure to be applied by hand. Wines were pressed into either two or three litre PET bottles (Caled Containers, Tasmania Australia),

with dry ice (solid CO2) used to protect the wine against oxygen. The bottles were not

completely filled to maintain a generous headspace and the lid was loosely sealed to allow

further CO2 release. They were returned to the warm room to complete primary

ferment. After fermentation had ceased, wines were settled for around three days and then racked off solids.

They were then inoculated with a standard commercial malolactic bacteria (Chr. Hansen, Denmark), and were monitored for completion of malate breakdown using thin layer

chromatography (kit available from Vintessential Laboratories, Victoria, Australia) and enzymatically with a spectrophotometer using the method outlined in the juice analysis section of this materials and methods section. Oxygen was prevented from contacting the wine by using the flexible nature of the PET bottles to squeeze gas out, before sealing the lid. This effectively reduced the headspace to a minimum.

On completion of malolactic fermentation wines were racked off lees into a fresh PET

vessel, again under protection from CO2. Potassium metabisulphite was added at a rate to

supply free SO2 levels of 57 ppm. Wines were left to settle in a cool room running at

around 4°C.

After settling for one month, wines were racked and bottled into 750mL glass bottles with screw caps. Sulphur was adjusted following racking to a level of 30ppm of free

SO2, as measured by the aeration-oxidation method (Iland, 2004). All wine movements

were conducted under dry ice protection, and by positive pressure by nitrogen gas. Sulphur was checked again in bottled wines and found to be low after about seven months in bottle. A number were checked, and on the basis of their results a blanket

addition of 20ppm of sulphur was added. CO2 was used to ensure that there was

minimal oxygen contact.

Winemaking – 2007 and 2008

Winemaking was carried out in 2006-07 on the nitrogen timing by rate trial, the irrigation by nitrogen trial, and the nitrogen by bunch exposure trial in the nitrogen application studies, and block A Pinot Noir in the vigour trials. In 2008, wines were made from the nitrogen timing by rate trial the field nitrogen and winery nitrogen comparative study in the nitrogen application studies, and block A Pinot Noir in the vigour trials.

In all nitrogen application rate and timing trials, fruit was harvested from the central two vines in the panel and the weight recorded. Where required, fruit from the buffer vines in the same panel was then harvested to bring the total fruit weight up to 12 kg. Where fruit from the two vines was greater than 12 kg fruit was removed.

In the vigour gradient trials, and field nitrogen versus winery nitrogen trials all vines were harvested. After weighing the total yield, excess fruit was removed to leave 12 kg of fruit for fermentation

Crushing of grapes was carried out using a Baesso 80kg crusher/destemmer unit (Australian Winemakers), following chilling in a 2°C cool room. Fruit was crushed directly into the fermentation vessel, and potassium metabisulphite added at equivalent rates to the previous season. Fruit was taken to a 25°C room for warming prior to inoculation, and enzymes were added as per the previous season.

Yeast preparation and addition was unchanged from 2006.

Fermentation was carried out at around 25°-26°C. Variance in temperature between fermenters was less than 2°C at any measurement period.

There were two cap management systems used in 2007 and 2008. Punch-down cap management involved twice-daily plunging sessions to break up the cap, with ten plunges using a potato masher at each session. Submerged cap management systems used a heading down board to hold the grape skins under the liquid, preventing the cap from ever becoming dry and reducing labour. Refer to p. 178 for a comparison of the two techniques.

temperature of the ferment, with minimal liquid required.

Pressing was carried out using a 20L Idro brand water bag press (Australian Winemakers) to a maximum pressure of 2 bar (200kPa). Pressure was maintained until minimal liquid continued to flow. Wines were pressed off skins at between -0.5 and 0.8 units Baumé in 2007 and at below 0 Baumé in 2008.

Wines were pressed into 3L PET containers (Caled Containers, Tasmania Australia) under dry ice protection. They were settled to remove gross lees and then racked again. The fruit volumes used allowed two 3 L PET bottles to be nearly filled; any excess was discarded.

In 2007 malolactic acid bacteria were added to wines made from fruit harvested from the vigour gradient trial. Malolactic fermentation was carried out in the PET vessels, and monitored for malate levels by a malate enzymatic analysis kit produced by Vintessential (Dromana, Australia). On completion of malolactic fermentation, wines were racked into

a blending vessel, and then into clean PET containers, with the addition of 57ppm SO2

from a 10% stock solution. They were then stored at 2°C until bottling.

Following pressing, all other wines were monitored for primary ferment progression using Clinitest tablets (Ames Division, Miles Laboratories, Illinois), until there was less than 0.25 g/L sugars remaining. They were then chilled by storing at 2°C and when settled the clear wine was racked off the solids, blending all PET bottles in each

treatment into a single blending vessel. Potassium metabisulphite was added at a rate of

57 ppm free SO2. They were returned to clean 3 L PET bottles and left at 2°C until

bottling. In 2007 bottling commenced 15 months after racking.

During bottling, wines were racked, re-blended and had free SO2 levels adjusted with potassium metabisulphite addition. Sulphur levels were tested using aeration-oxidation

(Iland, 2004) and adjusted to around 30ppm free SO2.

Final filtration and bottling took place in one movement. Wines were filtered through

two membrane cartridge filters in series (Tenco, Italy), the first with a pore size of 1µm,

and the second with a pore size of 0.25µm. They were bottled into screw cap 750 mL

wine bottles and also smaller 100 mL screw cap sample bottles for immediate colour testing. All movements were carried out under inert gas protection.