Sanitising Sealed Mains-Fed Water Coolers

Sanitising sealed mains-fed water coolers can be difficult but not impossible.  The main issue is how to get the descaling and disinfectant liquids into the unit. Typical units are the direct chill or spiral chill type.  Frequency for sanitising and filter changes is every 6 months.

The filter housing can be disconnected from the microbore tubing and a small device known as a venturi doser put in its place.  The doser is filled with the recommended amount of descaler and the hot tap actuated.  This will draw descaling acid solution into the tank.  After descaling, flush with at least 4 litres of water and test with pH paper until neutral.

The spiral chill pathways can be descaled and then disinfected using the same technique with respectively phosphoric acid (for example) and hydrogen peroxide.  The chemical is drawn from the doser by actuating the chill tap.  When the chemical begins to run from the tap (you can check this with pH paper or peroxide test strips), turn the tap off and wait for ten minutes.  Then flush with water until the test strips are clear.

This is not a detailed procedure and coolers vary considerably in design, however it will serve as a guideline.  Always check with your cooler supplier if in doubt.

Descaling and Disinfecting Water Coolers

The hot tank of coolers can be descaled using an acid such as phosphoric or citric. Sometimes other internal  parts of coolers need to be descaled and disinfected.  Scale build up in reservoirs, for example, is usually not severe but can lead to microbiological problems if left.  Attachment of micro-organisms and ultimately formation of a biofilm can rapidly cause deep-seated contamination which is not always easy to remove.

It is common practice to use a descaler, accompanied by mechanical action such as brushing, followed by a disinfectant such as hydrogen peroxide.  This will remove the scale and destroy the biofilm.  In some practices it is considered that one application of acid is sufficient to descale and destroy biofilm.  This is not always the case and is very dependent on the strength of acid used.  Very strong acids will do the job but these are usually applied diluted.

Diluted acids will remove scale more slowly and much of the acid is used up in this process.  In this case biofilm will not be removed.  If you want to use acid alone, then either use very strong acid (not recommended from a safety point of view) or use the acid in two steps, one to descale and the other to kill bacteria.

An alternative is to use an acid containing a disinfectant component which can then act as a sanitiser while removing scale.  These are available on the market.  However, the preferred method is to descale and then disinfect, in two separate steps.

Rapid Testing of Water Samples in the Bottling Plant

Following on from the ATP article in a recent blog, this section describes the procedure for rapid microbial testing of water samples.

Because water samples contain very few bacteria, an enrichment technique is employed. This involves taking a sample aseptically, and expelling it via a syringe through a special filter.

After waiting for 30 minutes to allow the microorganisms to recover from the stress of filtration, the filter housing is opened and the filter swabbed, using the special swab used in the ATP meter.

The swab is put back into the swab tube and activated using the snap and squeeze action. The swab is placed in the ATP meter and the measurement started. Results are recorded from the display.

Simple Microbiological Testing in the Bottling Plant

A new type of dipslide has recently appeared on the market which is double sided and able to detect 4 different groups of organisms:
1. Nutrient agar on one side to detect total counts.
2. Chromomeric coliform, E. Coli and pseudomonas aeruginosa on the other side.

It is a very versatile slide that can be used to dip into liquid samples or used as a contact plate on solid surfaces. The nutrient agar reacts with enzyme to produce a colour change which is specific to the bacteria type, allowing easy enumeration.

When sampling fluids, the sample is taken by immersing both sides of the paddle into the fluid to be tested. Excess sample should be gently shaken from the paddle before replacing in the container.

Surfaces can be sampled by allowing direct contact between the agar surface and the test material. The paddle is flexible and can be bent at the upper end to allow both surfaces to come into intimate contact.

Bacterial recovery rate is about 50% so that sweeping an area approximately twice that of the paddle will give a more accurate result. Afterwards incubate at 30/35 deg C for 24-48 hours, when full enumeration should be complete.

Apart from an indicator of aerobic bacteria (TVC), as shown in the picture above, the reverse side will give an indication of coliforms and Pseudomonas according to the following colour scheme: blue/purple or blue/green colonies = E.coli; pink/magenta colonies = other coliforms; buff colonies = Pseudomonas.

Recycling Plastics from the Bottling Plant

I previously attended a seminar run by the Food and Drink Association in the South West of the UK, entitled “Make Money, Not Waste”. This gave an up-to-date picture of latest developments in recycling and sustainability in general. My interest and perspectives were naturally focused on bottled water applications.

The main waste issues for bottlers are caps, 19L bottles and chemical drums, particularly the 25L size. Unfortunately all three items are made of different kinds of plastic which sometimes deters recyclers from collecting smaller quantities. If you are fortunate enough to be near a recycling site there may be an opportunity to drop off unwanted drums during the course of a delivery round by your drivers. However, this is not always convenient.

The organisation WRAP (Waste and Recycling Action Programme) currently has a study underway to collect plastics from smaller companies and deliver them to recycling points. This is useful for those companies who find it difficult to persuade recyclers to collect smaller quantities.

ATP Meters

Over the past ten years or so, a great deal of emphasis has been placed on the use of bioluminescence technology in the detection of microorganisms.

The mechanism by which fireflies produce a flash of light was first analyzed and identified by William McElroy in 1947. McElroy found that central to the light emission process was a specific enzyme reaction catalyzing the consumption of adenosine triphosphate (ATP).

In microbes, ATP can only be detected when living cells are present. It has since been established that the amount of light emitted from this reaction is directly proportional to the amount of ATP present. A high reading of relative light units (RLUs) indicates that the sample contains a high number of micro-organisms, provided that the background ATP level is low.

Unlike traditional testing methods, results from a bioluminescent reaction can be obtained quickly. Light is produced within seconds and can be measured with a luminometer (ATP Meter).

The current palm-sized instruments bring together state-of-the-art photodiode technology with simple user-friendly design to produce an affordable hygiene-monitoring system. Used with  ATP swabs, levels of contamination can be determined in just 15 seconds.

Key features of luminometers include, low cost, high sensitivity, compactness, simplicity in use, self- calibration with background check. Readings may be downloaded onto a PC or, as an optional extra, analysis software will provide spreadsheet-compatible data.

Preferred Bottle Wash/Sanitiser for Polycarbonate

New products specially designed for washing polycarbonate bottles are a rarity on the market. However, one new product provides many benefits for the bottler and gives that added confidence that the bottle is clean and germ-free. The product contains a food-safe disinfectant as well as the cleaning power of other products.

Extensive testing and trials have been carried out which show low TVCs, as expected, but also a reduction in the incidence of green bottles returning to the plant. The new product may be used under adverse conditions, for example, if the heater stops working or the throughput of bottles has to be increased because of production demand. If the concentration of the product is cranked up further, it behaves like a disinfectant and will pass the requirements for EN 1276.

The product generates slightly more foam than a regular bottle wash product, but rinsing is very rapid under normal conditions and the foam is controlled, particularly at normal wash temperatures.

The foam tracer makes the wash solution easier to see and provides reassurance that all parts of the bottle are being thoroughly washed.