Article in «Fleischwirtschaft» magazine: Smoking with ionisation follows different rules

by | Nov 25, 2022

Recently, an electrostatic filter can be retrofitted directly into a smoking unit. The smoke is electrically charged as it flows in. The electromagnetic forces cause it to settle faster on the product. This brings sustainable and economic advantages such as lower energy consumption, shorter smoking times and significantly lower fine dust emissions. The new Ionsmoke system is already in use more than 35 times worldwide.

This article was published in Fleischwirtschaft magazine in the september 2022 issue.

The refinement of a meat product through smoking is also a topic in the environmental discussion. On the one hand due to the energy consumption, on the other hand due to the environmental impact of emitted smoke. Traditional smoke is produced by incomplete combustion – after the smoking process it has to be filtered in an elaborate way. New legal requirements in the course of environmental protection make it new ideas have to be introduced to the market. One of these ideas comes from a small butcher’s shop in a village in Switzerland. The butcher there installed an electrostatic filter on the roof of his butcher’s shop to reduce the fine dust pollution of his open smoking system. When he understood the principle of the electrostatic filter, he had the idea to build this filter directly into the chamber. There had already been tests with electrostatic smoking over the past decades. But it was only now that a sophisticated patent was ready for the market. Today, the modules can react to the various external influences in a plant in millisecond cycles via high-performance chips. Insulators and cables are built more robustly and can withstand the extreme conditions in a chamber. And the process is more sophisticated. The process technology and the treatment sequences for smoking with ionisation follow different rules than those for open or closed, classic smoking systems. High voltage must be introduced dynamically for each product, and the treatment then runs completely automatically. HACCP specifications are still adhered to.

Economic advantages with Ionsmoke

The main advantage is the faster smoking time. Most of the other advantages are derived directly from this. Traditionally, the smoke chamber is filled with smoke. Then follows the exposure time. The smoke settles on the product due to the long standing time in the chamber. When smoking with ionisation, the smoke is actively used up in the chamber. This is why ionisation can be called active smoking instead of the previous passive smoking. Empirical evidence has shown that ionisation halves the smoking time in most cases. Since the smoking time tends to be related to the drying time, it is possible that this will also be shorter – for example, if the smoking step and the drying step run in the same interval. In this case, entire smoking and drying cycles can potentially be shortened. The effect on the total time can therefore be greater than the pure effect of ionisation on the smoking time. The general recommendation is that ionisation becomes efficient for a traditional total smoking time of 30 minutes or more. That weight is lost during warm and hot smoking is quite desirable. But there is a required weight loss and an unnecessary weight loss. For example, a product may have already reached its desired weight loss before the colour is right. With each additional minute of smoking, the weight is then unnecessarily reduced further – the product literally goes up in smoke. With the faster smoking times in ionising, this weight loss can be prevented or at least better controlled. A faster process also saves electricity for smoke generators and heating rods. Shorter smoke times result in a longer life. If afterburning exists, natural gas can be saved.

Smoke density monitoring helps quality assurance to ensure consistent colour throughout the year. The technical department is immediately informed if there are problems with the smoke density. The return on investment has to be calculated individually. There is a savings calculator for the two main savings criteria, time and weight. The graphic shows the process of a typical smoking unit with ionisation in five steps:

  1. Due to high voltage, the particles contained in the smoke are electrostatically charged at the electrode when flowing through the smoke chamber.
  2. Due to this charge, the particles are quickly and evenly attracted by the product in the smoke chamber.
  3. In recirculation mode, practically all smoke particles are thus absorbed by the product and the system in a very short time.
  4. The control unit with a high-voltage source is mounted on the outside of the smoke chamber. The high voltage generated there is directed to the electrode inside the smoke chamber.
  5. The two insulators mounted on the side prevent short circuits and are designed to ensure that a stable high voltage can be applied even under changing temperatures, humidity and contamination.

Analysing smoke density

The smoke density can be measured with the ionisation method. Several factors play a role: chamber size, temperature and humidity. The two available measurands are voltage and current. Their ratio shows how much smoke is in the chamber. If there is a lot of smoke in the chamber, the electrons do not have to travel as far. That means it takes less current to reach the desired voltage. If there is no smoke in the chamber, the electrons travel further. It takes more current to reach the same voltage. The curve of current and voltage is recorded. In a glow smoke installation with a feed motor, this can be easily seen: After the pause time, when new glow material comes onto the glow spot, it can be read from the current curve when fresh smoke enters the chamber. The curves are automatically checked for typical indicators and compared with existing curves. The system detects a lower smoke density. A significant deviation may indicate a malfunction of the smoke generator. This message can already be communicated during the smoke step.

Smoke generators and products

In the meantime, retrofitted plants with daily production run with smoulder smoke, smoulder smoke generators or friction smoke. For example, raw sausages, bacon or sockeye salmon are treated with ionisation in cold smoke units. Gourmet ham and pork ribs (Rippli) are treated with warm smoke and trout, wiener and ham sausage (Ham Sausage) with hot smoke. For sausage, a wide variety of calibres are processed with different casings. There are also the first fish factories that work only with ionisation. Cheese is also smoked with it. Initial tests with liquid smoke were promising. However, the economic advantages tend to be smaller – because the high investment costs of both liquid smoke and ionisation mean that the return on investment comes later. Recently, products have been regularly run with steam smoke generators. This also works with the latest high-voltage modules and gives a significant saving.

Safety during operation

With ionisation, the voltage (volts) is very high, but the current (amperes) is very low. This is comparable to an electric fence: this generates up to 15 000 volts, but the current flow is so low that it is harmless. Released smoke, with or without ionisation, is toxic to humans. Installations in smokehouses therefore already have existing safety standards. The door can be opened from the inside and emergency switches are fitted everywhere. With ionisation, a coded door switch must additionally be installed at every facility for safety. If someone opens the door during operation, the ionisation is interrupted. In addition, every system needs an earth measurement. Pure proximity switches are not allowed, as they can be bypassed too easily. Proper earthing prevents the chamber from getting an altered potential due to the high voltage. With correct earthing, the chamber and chamber door can be touched without any problems in any case – even during operation. Ozone is produced during the ionisation process. The ozone can only be detected when the ionisation is operated without smoke supply. Ozone is harmful to humans in high concentrations. The chamber must be well vented after ionisation. However, ozone also has a positive side effect: the disinfecting effect of ozone can also eliminate viruses, bacteria and mould. These ideas have not been pursued so far. However, they could be interesting, since in many air-conditioned rooms the air is already treated with UV light up to now.

Environmental effect

The smoke produced is released into the outside air via the chimney after the product has been recirculated. In the process, fine dust pollution of the environment takes place. In many countries and regions, this is now prohibited by law. To meet environmental protection requirements, the market offers various solutions. Often, thermal afterburning is used: In a thermal afterburner – either in a chamber or with an open flame in the chimney pipe – the smoke is burnt out at 800 °C. The energy source for this is typically a fuel oil. The energy source for this is typically natural gas. And natural gas is expensive, and despite the absence of particulate matter, CO2 pollution remains. In most cases, total carbon emissions are measured to measure the pollution. An electrostatic fine dust filter, i.e. ionisation, cannot reduce the total carbon, regardless of whether it is installed in the chamber or in the chimney. Total carbon shows up in gaseous form, and ionisation only filters particles out of the air. However, at least in countries or areas where particulates are measured instead of total carbon, post-combustion can be eliminated if the system is operated with ionisation. Particulate matter in a closed system can be reduced by up to 98% through ionisation. However, what ionisation can also bring in terms of areas and countries where total carbon is crucial: Less smoke is produced due to shorter smoke times. This results in fewer operating hours of, for example, a gas-fired afterburner and, of course, the smoke generator itself.

Food safety

Food companies regularly send their products to the laboratory to be tested for food safety. So do the customers where Ionsmoke is used. Polycyclic aromatic hydrocarbons (PAHs) are also relevant for smoked products. Food safety has always been a given with ionisation. If the same product colour was achieved, the measured values were also similar. Substances such as benzo[a]pyrene were not detectable in laboratory tests after just under two hours of smoke. In direct blind tests, it was not recognisable whether the product was smoked traditionally or with ionisation.

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