As consumers and, to an even greater extent, the grocery trade demand food products that keep as long as possible, producers are finding themselves compelled to develop new preservation techniques with minimal adverse effects on their products. Clean room technology is one of the responses to this demand. Industrial clean rooms originated in the USA in the 1960s. During this period, it was recognized that space flight requires highly integrated microelectronic circuitry that is only adequately reliable when manufactured in extremely clean conditions. Today, all microchips are manufactured in environments with low particle counts. As a general-purpose technology, clean rooms are now being used in other sectors too, including the food industry.

The clean room - a bell jar for foods
Clean rooms are always constructed according to the same principle. The clean room is entered by passing through a "dirty" zone, the "grey area", and then through individual air locks which lead to the core - the actual clean room portion with the highest level of cleanliness. A clean production environment is guaranteed by a cleverly devised system for routing the air flow, an arrangement based on high-quality submicron particulate air filters that trap the smallest particles and micro-organisms. These systems use special HEPA filters (high efficiency particulate air filters) that filter out suspended particles only 0.5 micrometers in diameter. By way of comparison, the average bacterium cell has a size of approximately two micrometers.

Not all clean rooms are the same, however. Clean rooms are defined by ISO clean room classes. The standard ISO 14644-1 defines how many particles of what size are allowed in a cubic metre of air. ISO Class 1 lays out the most stringent standards of air purity, and Class 9 defines the least stringent. As long as there are no germs clinging to them, dust particles don't represent any great danger in food production. Germ content is the primary factor that determines air cleanliness, and this is expressed by the number of colony-forming units (CFUs). Which clean room class is needed depends on the product. The production environment for biscuits doesn't have to be as hyper-clean as that for semiconductors, for example. In the food industry, clean rooms are normally of ISO classes 5, 6, 7, or occasionally 8. For Class 5, for instance, each cubic meter of air must contain no more than 3,520 particles measuring 0.5 micrometers in diameter (3.5 particles per litre). This represents a microbial contamination level of less than one germ per cubic metre of air, which can be considered practically germ-free.

Foods from the refrigerated section become less perishable
By ruling out the possibility of germs, manufacturers remove from their production and packaging methods many factors that would otherwise cause losses in quality or even premature spoilage of foods. Another benefit is that the foods can be transported or stored for longer periods of time, which gives producers more freedom and could allow them to export to new markets, for example. Clean room technology is also the basis for the development of new products with improved properties with regard to freshness and preparation. The principle that applies here is: the less treatment the fresh products undergo, the more important it is to ensure that the production environment is as hygienic as possible. Chilled foods are a good example. In contrast to tinned goods or frozen foods, these increasingly popular fresh food products from the refrigerated section keep no more than a few days or weeks. On the other hand, if the pasta specialties, salads, and potato dishes are produced and packaged in clean rooms under germ-free conditions, they can keep up to 50 per cent longer.

Because of the high costs of large clean rooms, alternative clean room designs are gaining ground. There is a trend toward keeping clean rooms as small as possible in order to reduce the outlays for technical equipment and cut costs. Furthermore, smaller clean rooms entail proportionally lower risks of contamination. Ideally, therefore, clean room conditions would be in place only right at the point where food is processed. This trend is being addressed by "mini-environments" or "flow boxes" - small, enclosed, clean room units, some of which are modular in design or even transportable.

Cold bottling in sterile environments
When it comes to miniaturizing clean rooms, the manufacturers of beverage-bottling equipment have moved into the big leagues. More and more non-carbonated beverages and sensitive products that are in the only weakly acidic pH range because they lack carbonic acid are now being bottled in germ-free environments. Thanks to rapidly growing demand for these alcohol-free beverages, bottlers have for several years been making increased use of a technique ultimately based on clean room technology: aseptic cold bottling.

In the early days of this technique, the whole bottling system was located in a clean room, but today only a minimum of clean room technology is needed. Only the path taken by the sanitized bottles lies inside an insulator, a sealed chamber systematically isolated from the ambient air. In modern bottling plants, only ten percent of the original clean room space is located in this critical insulated area. Here as well, HEPA filters are used to remove germs from the air fed into the insulator, which results in a sterile atmosphere inside. The clean room area around the filling and sealing machines is implemented as an ISO Class 5 clean room, germ-free in other words. Furthermore, a room-in-room concept, in which a second, isolated Class 6 clean room is installed, provides protection against re-contamination from the ambient air and the grey zone. Room-in-room designs of this sort not only lead to lower investment and operating costs, they also frequently guarantee a higher level of cleanliness than large-area solutions. Regardless of which solution is used, whether large or small: clean rooms are likely to become increasingly important for food producers who want to safeguard their competitiveness and expand their market share.

Quelle: Koelnmesse