Steps in the packaging process
After a wine has completed all pre-packaging adjustments, including filtration, it travels through the different components of the bottling line. Sanitation of these components is covered in the bottling line sanitation page.
Bottle rinser
The bottle rinser is used to remove any unwanted material that may be present in the empty bottles. Traditional rinser equipment picks up and inverts individual bottles while a jet of filtered (and sometimes UV-treated) water is injected into the bottle. The water is then drained from the bottle with shaking while inverted, removing any particles at the same time. The bottle is then reverted to the upright position and moved or sent by conveyor to the filler equipment. The rinser water can be collected, sterile-filtered and re-used to reduce water wastage. Today, bottles are more likely to be rinsed using filtered air, reducing water wastage and preventing water contamination issues. Bottles are inverted and shaken while being injected with pressurised air which aids in removal of any foreign particles.
Wine filler
In small bottling operations, filling can be achieved by gravity, with a filler bowl positioned vertically above the filler heads. Wine is pumped in stages from a bottling tank via a filtration set-up into the filler bowl as required. The filler bowl is generally blanketed with an inert gas. Bottles are placed on a base plate underneath a filler head containing a filling spout. The base plate and bottle rise, which opens the filling valve and wine enters the bottle until the desired fill level is reached.
Wine fillers on continuous lines (such as those in large bottling facilities) have multiple filler heads arranged around a rotary carousel. Some fillers have up to 120 filler heads that fill bottles at the same time. The rinsed bottle is picked up and placed on a base plate underneath a filler head containing a filling spout. Isobaric filling (counterpressure), counterpressure with a vacuum and counterpressure with double inert gas pre-evacuation technology can all be used on continuous lines. Counterpressure processes require the bottle to be sealed against the filling spout. Inert gas can be injected into the bottle or a vacuum applied. Pressurised wine enters the bottle and displaces any inert gas through a restricted gas venting valve. Once the bottle is filled, inert gas is injected into it to create sufficient pressure to drive any excess liquid back into the holding tank through another inlet in the valve. Vacuum units draw a vacuum in the bottle before filling. Electro-pneumatic glass filling valves and level probes or cameras also ensure consistent fill heights from each filler head.
The fill volume is controlled by filling bottles to a designated fill height and using an appropriate closure suited to the bottle. This varies by bottle type and by wine temperature; equipment needs to be adjusted to meet these requirements prior to the start of a bottling run.
Wine should be circulated from the bottling line filler bowl to the filler tank for 5 – 15 minutes. Wine should be tasted on start-up to ensure no dilution or foreign taints and signed off as acceptable prior to the start of bottling. The first dozen or two, subject to filler head number, should be isolated and checked later and/or reincorporated into the run or returned to the wine in tank. Dissolved oxygen should be measured in these bottles at start-up to ensure gas cover/control is adequate. Gas measurements are then often performed hourly.
Occasionally, if a filler head falls off, or other foreign object enters the wine, then these bottles will be omitted from the line by weight non-conformance as they pass over a balance. Broken bottles during bottling can cause broken glass residues and the line should be stopped and cleaned of these materials, and the area spot-sanitised before restart. Visual inspection, infrared scans, balances and metal detectors are also often integrated into packaging lines to capture non-conformances.
Fill volumes
The fill volume for a standard wine bottle is 750 mL ± a set tolerance. This tolerance must conform to minimum labelled volume under weights and measures legislation, which can differ between states within Australia. Different bottles have different tolerances, and these details can be found on the bottle specification sheet provided by the glass manufacturer. It is also important that the appropriate closure is used with the appropriate bottle as these can affect these regulatory requirements as well as the packaging effectiveness and storage of the wine.
There are cost implications of overfilling bottles. For example, if bottling 1,000 L of wine with exactly 750 mL of wine per bottle, this equates to 1,333 bottles. For a $30 bottle, this equates to $40,000 value. Consider if all bottles of this wine were overfilled to 795 mL, this would equate to just 1,250 bottles and $37,500 in value, or a 6% decrease in value of stock produced. Overfills can also result in quality and storage implications, including leakage.
Wine losses during packaging
Some wine loss is expected during filtration and bottling. Losses occur due to transfer, recirculation and removal of any water from the line, wetting of membrane or cartridge filters, bottles excluded because of low fill volumes, non-conforming product, analysis samples or samples taken for physical measurements. Volumes lost can vary from approximately 0.5 to 5% of the total wine volume, with larger volume losses occurring during the packaging of smaller batches due to economies of scale. An Ask the AWRI: How much wine to expect per tonne of grapes? (PDF article) details further information about typical juice extraction volumes, juice and wine losses and gains throughout the winemaking process and final extraction rates of bottled wine to expect from the initial tonnes crushed.