Mechanisms of the detergency: products, methods, evaluations and controls

Washing and disinfecting refillable bottles is part of the general hygiene framework for the food industry and industrial cleaning, and requires the use of equipment that is often cumbersome and mechanized, as well as consumables such as detergents and antiseptics. The aim is to achieve a physical and chemical action which, combined with a thermal action, will produce containers compatible with food hygiene.

Five essential factors come into play when washing containers:

• detergents ;

• their operating temperature ;

• duration of treatment ;

• mechanical action, mainly performed by internal or external pressurized injections, with simultaneous draining during this operation.

Washing always ends with a final rinse in clear drinking or sterile water, usually chlorinated.

Washing must be controlled at the washer outlet by candling the containers. In the past, this candling was carried out by one or more operators; today, it is carried out by machines called candling machines which, in real time, control all the elements processed. This control even extends to the use of so-called "sniffer" machines or "artificial noses" capable of detecting suspicious odors. However, continuous control needs to be confirmed on a one-off, random basis by physico-chemical control, with samples taken and processed on the packaging line.

The detergents used in the treatment process may be alkaline, acidic, oxidizing or enzymatic, combined with a surfactant.

Numerous authors have studied the mechanism of detersion applied to bottle washing, and have proposed quantified evaluations of this operation. Others have defined the optimum conditions of use for detergent baths, in order to extend their service life before they have to be renewed, and to eliminate used baths rich in mineral (e.g. aluminum from labels and stanioles) and organic soiling. Because of these thermal and chemical discharges, washing refillable containers is a polluting operation for the environment.

A particularly dangerous zone in a bottle washer has been identified: the "warm water tank", where the rinsing and detergent injection zones on the washing machine meet.

Chlorination is preferred for final rinsing on bottle washers. The use of chlorine requires certain precautions to optimize its effectiveness, notably a sufficiently long action time before the washed container is filled.