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by Nathan Schiff, Ph.D.

Associate Editor - Institutional, FABRI CARE

I recently attended my son's wedding in Israel and saw a modified dishwashing machine which could be adapted for use in hospital and health care facilities.

The kibbutz at which I stayed is religiously observant and the Biblical laws of Kashrut, dating back 3000 years, are adhered to. Kashrut are laws dealing with what foods can and can not be eaten, and prohibits cooking or eating meat and dairy together. This separation not only includes the foods themselves, but also the utensils, pots and pans in which they are cooked and the dishwashers and the dishpans in which they are cleaned.

Breakfast at the kibbutz generally consists of a dairy meal. Most Israelis eat their heaviest or meat meal at lunch time. Dishwashing therefore poses a unique problem in such establishments, since residues or flavors from the breakfasts dairy dishes can attach themselves to trays and racks and possibly the sidewalls of the dishwashing machine. These could technically be transferred to the following batch of meat dishes, rendering the machine and all of the utensils non-kosher.

My curiosity led me into the kitchen where I noticed a unique phenomena. The orange color-coded racks seemed to be entering into the 2-compartment tunnel dishwashing machine in a clockwise direction whenever meat dishes were being cleaned. Dairy soiled dishes and their green color-coded racks were carried by the conveyor into the dishwashing tunnel in a counterclock wise direction.

Tunnel dishwashers are designed to handle large quantities of dishes over a short period of time; typically 300 to 600 meals per day. The machine is divided into various compartments; each one separated by a curtain through which the dish trays pass on their 3 to 5 minute trips. Prewashing and removing heavy or loose soil is carried out at the beginning of the cycle. From there the rack is moved along a conveyor where the actual washing takes place. This compartment contains a matched series of upper and lower jets from which high-pressure water maintained at 160 F is sprayed onto the trays and dishes. Detergent is simultaneously metered into this compartment. The resulting mechanical actions of high-pressure water spraying and detergent activity serves to loosen and remove adhering residues.

The tray is then carried along into a second hot water rinsing compartment where the emulsified soils are washed off. A rinse aid chemical is then applied in order to prevent water-spotting stains from occurring. Sanitization in high temperature machine occurs by virtue of the 180 F temperature during the water rinse cycle.

The dishwashing equipment on this kibbutz consisted an extra wide tunnel washer; and appeared as if 2 tunnel dishwashing machines had been constructed into a single unit. The compartments from each half of the machine were totally isolated from each other. Each half of the machine maintained separate detergent and rinse additive feed mechanisms and solenoid valves. The automatic water fill tanks and electric heating booster used to raise the water temperature to 180 F; was common to both sections of the machine. A single control panel serviced both sections of the machine with pre-programmed instructions relating to cycle time, water temperature and detergent and rinse additive concentrations. At the flick of a switch marked "M" (for meat), the conveyor carried the trays in a clockwise direction into the designated compartments where the prewashing, washing, rinsing and high temperature sanitization cycles was carried out; all within 3 to 5 minutes. Activating the "D" (dairy) switch resulted in the conveyor moving the soiled dishes in a counterclockwise direction and into the dairy section of the machine.

A dishwashing machine so designed could also be economically for use in hospital and health care facility kitchens. These institutions often care for patients with suspected contagious diseases or experience outbreaks of nosocomial infections. These are hospital-acquired illnesses in which uninfected individuals, contract illnesses during their stay in a health care facility. Patients in restrictive isolation also require special handling of their cutlery and utensils in order to prevent the transmission of infectious agents to others.

Despite the fact that the short, 180 F hot water rinse is generally considered sufficient to sanitize dishes and equipment, spores and some pathogenic bacteria can survive these temperatures. They can then exert their activity at a later time when conditions for their multiplication are more favorable.

A second source of potential cross infection occurs as a result of biofilm formation. Certain bacteria secrete a sticky polymer, which imbeds itself on utensils and equipment as a very thin but strongly adherent film and is not readily removed during the course of a normal dishwashing washing cycle.

The bacteria responsible for this secretion are usually non-pathogenic, but their secretion serves as glue in order to attract and harbor pathogenic microorganisms such as Lysteria monocytogenes. The resulting combination is referred to as a biofilm. Disease causing organisms can be transferred from a biofilm, onto otherwise suitably cleaned wares. By maintaining a separation of utensils and dishes from patients with suspected contagious diseases, using the equipment described above, harmful bacteria are not afforded the opportunity to contaminate wares destined for use by the staff or general hospital population.

The old saying that you are what you eat can be expanded to include: You remain as healthy as dishes from which you eat off.


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