Krones loading beer plastic bottle filling analysis

The key is oxygen absorption

Various kinds of information prove that the beer market at home and abroad is about to enter a period of high sales of plastic bottles including the filling of small-capacity bottles of beer. It is reported that in 2005, PET bottle filling beer will reach 3.5% of global beer sales.

The ideal filling: equal filling system

Under normal circumstances, beer is filled into plastic bottles via a bottle filling and filling machine. The rinsing process first removes the residual material from the blow-molded plastic bottle. Since the oxygen in the cleaning water is always saturated, every drop of residual moisture will increase the oxygen in the beer. Therefore, it is recommended to use an electrically controlled dual-channel rinser, rinse the plastic bottle, and blow dry with sterile air.

As far as the filling process is concerned, there is an increasing tendency to use a constant volume filling system equipped with an induction flow meter. This process is ideal for containers of the same size as plastic bottles. For the aseptic polyester bottle filling process, Krones must use this isocapacity filling system. Because it uses a long tube filling system, it is gently filled below the surface of the liquid level, and before the lid is capped, the bottle is flushed with the gas in the cylinder, and then the carbon dioxide in the clean gas channel is discharged. Prepare the pressure so that you can maintain a very good oxygen content. The air inside the PET bottle will be discharged from bottom to top and it will work well. Since the valve does not have a spring device, a very good sanitary design is formed.

The Krones VODM-L-PET filling system first uses the bottle jet. Here Krones avoids the use of a dynamic seal. Instead, it uses a folding bellows valve for static sealing, followed by back pressure with clean gas before slow filling and rapid filling. Here can also take the slow irrigation of vials, large bottles of fast irrigation. After filling, waiting for a certain period of rest time, so that large bubbles float on the liquid surface, the plastic bottle is relieved. After the bottle is lowered, the filling tube is emptied immediately. The CIP cleaning procedure is best used in this filling system. The CIP cleaning program can be freely set by the electrical control system. This procedure ensures the best flow conditions.

Advantages and disadvantages of plastic bottles

Plastic bottles for filling beer have both advantages and disadvantages. Its advantages lie in its light weight, unbreakability, flexible design, high transparency, and accurate dimensions. However, the plastic bottle cannot be fully evacuated in the filling machine, so its airtightness is not good. Since atmospheric pressure plays a major role in gas exchange, oxygen penetrates into the plastic bottle (the oxygen content in the product should be minimized) and carbon dioxide is released.
Plastic bottles cannot be overheated, which means that plastic bottles generally cannot be pasteurized. Its head compressive strength is limited, which affects the choice of caps. When pressurized and heated, its volume changes and the bottom of the bottle bulges and the bottle easily falls. Plastic bottles are generally more dimensionally accurate than glass bottles, but they are not standard containers at the specified angle. Ambient temperature, light and handling during transportation can affect plastic bottles. Other factors include the raw materials used to make plastic bottles, the selected styling design, and the bottle blowing process and bottle shrinkage.

Influence of cap type The choice of cap type has a great influence on the air in the bottle neck, the total oxygen content, and shelf life of the beer. The market currently offers a variety of different plastic closures for stoppers, aluminum caps, crown caps, spin caps, and pre-seal caps. Each bottle cap has its own advantages and disadvantages.
Pre-seal cap

There are two ways to choose from. One is to place the pre-closure on the mouth of the bottle after high-pressure sprinkling, and then thread the air to inspect the pre-closure position and seal the original cap.
The second is a built-in pre-closure cap. When the bottle cap is screwed on, the inner gasket is pressed against the bottle mouth, and then the thread injection is performed, and the cap is tightened immediately.

Differences in Oxygenation Capacity between Long Tube Filler and Short Tube Filler When the beer is filled into a PET bottle or a plastic bottle, oxygenation is an important indicator. In order to compare the filling systems and cap types, the following theoretical calculations are listed. Of course, these theoretical values ​​may deviate from the actual situation. The numerical calculation is based on 500 ml/bottle, carbon dioxide content 5.5 g/l, and filling temperature 12°C. Assuming that the initial oxygen content in the beer is 0.05 mg/L (when the bottle is rinsed), the purity of carbon dioxide within the bottle is assumed to be 96% to 98% (with a bottle of water).

The difference between the long tube machine and the short tube machine is that in the short tube type filling machine, the purity of the carbon dioxide in the rinse bottle is 95%, while in the long tube filling machine, the purity of carbon dioxide is 98%, and the amount of oxygen is increased. The short tube filling machine was 0.08 mg/l, while the tube machine was 0.03 mg/l. The latter case assumes the use of a VODM-L-PET filling machine with a pure CO?2 backup pressure. After the beer was high pressure injected into the bottles in both filling machines, the air content in the bottleneck space was 0.35 mg/bottle.

When using crown caps, screw caps or caps with pre-seal caps, the total oxygenation level is approximately 0.18 mg/l (according to Ulrich and Ulllig & Vilacha's Law).
In the other case, if aluminum caps are used, the total amount of air in the bottle caps must be about 10.5 ml. However, it is also estimated that in the extremely unfavorable circumstances, 30% of the total air volume will be bottled. The remaining leaks along the thread, causing the actual added air volume to reach 3.15 milliliters.

This is even more evident when using plastic caps without pre-sealing. Because the plastic cap is opposite to the aluminum cap, the mouth of the bottle is threaded and the gap between the thread of the bottle and the thread of the cap is very small. It is estimated that only half of the air leaks through the thread. Therefore, the worst case scenario will increase the air volume by 5.25 ml. Based on this point of view, it should be possible to use pre-seal caps, screw caps or crown caps.

Relationship between total oxygen content and bottle volume and cap type

From a series of tests, Krones used a 500-ml glass bottle with a crown cap and a 500-ml polyester bottle with a plastic screw cap to carry out a comparative measurement: the oxygen content in the liquid (unit: mg) / L), the amount of oxygen in the air in the bottleneck space (unit: mg/l) and total oxygen (total oxygen content referred to as TPO, unit: mg/l). The amount of oxygen flowing from the sake tank reaches 0.05 mg/l. By comparison, it can be clearly seen that there is a great difference between the glass bottle and the PET bottle, in which the pressure value of oxygen content from the inner space of the bottleneck inside the PET bottle is the highest.

Since the pressure within the bottleneck is related to the filling volume, the bottle size is inversely proportional to the value, and the larger the bottle, the better.

Regardless of the market demand, in order to maintain the pure taste of the filling, these technological factors will affect the selection of the filling bottle and its cap.