Hygienic applications – Is the 1.5 seconds rule applicable? Visaya Weekly Episode 37

Is food that has fallen on the ground safe to eat?

Well, this is German from Visaya and we will take a closer look.

The 5-second rule states that if you pick up food from the floor within 5 seconds it will be safe to eat. Hypothetically there will not be any bacteria attached to it.

But let’s take one step back and think how do companies producing food make sure that there are no (unwanted ) bacteria on the food we eat.

Let’s take, for example, the nut and chocolate paste in this brioche!

A mixture of nuts, sugar and cocoa powder is heated up and mixed. Then it is injected into a glass jar and ready for shipment and distribution. During this process, the tasty liquid is stored in vessels, processed in mixers and of course transported through pipes. Lastly, it reaches the glass container and this pastry.

The equipment is designed so that no residue or contamination is generated or transferred to the final product. These plants have to be regularly cleaned and/or sterilized so that product residue or defective batches don’t ruin our breakfast

And just like the equipment, the instruments used in these kinds of plants are specially designed to work perfectly under these conditions.

Nutella Factory
Courtesy of Getty Images

There are 6 features that you need to take into consideration when selecting an instrument for Food and life sciences applications:

  • The Material
  • The Shape and superficial Roughness
  • The Sensor
  • The Process connection
  • Maintenance – Calibration
  • Certification

I will use this state of the art temperature sensor, the TM411 from Endress+Hauser to show this.

The Material

This sensor is made of AISI 316L or 1.4435 stainless steel. This is an ultra-low carbon stainless steel that avoids the formation of ferrite. It guarantees the best corrosion resistance properties.

The Shape and Roughness

In these kinds of instruments, you will not see sharp edges. The roughness of these devices are lower than 0,76 micrometers or 0,38 micrometers for electropolished devices. This is in order to avoid any contamination, condensation or localized corrosion.

The Sensor

In this case, we have a Doube A (AA RTD sensors acc, to IEC60751) RTD sensor that means a tolerance of  0.10 degrees Celsius (from 0-200 C).

Endress+Hauser TM401
Courtesy of Endress+Hauser

this kind of accuracy is extremely important for the food and life sciences industries.

This temperature device comes with a special fast response called Quicksense. If the sensor is used without a protection tube it has a response time of 1.5 seconds. That is 10 times faster than a standard thin film sensor!

In this case, we have a thermowell with a tip diameter of 4.3 millimeters. The response time is 3 seconds.

The Process connection

The thermowell comes with a clamp flange that allows the sensor and thermowell to be easily replaced if necessary. There are other types of process connections as well. For example, threaded connections and T corners that comply with the rules we spoke of earlier. 

This thermometer has one additional feature called QuickNeck that allows the removal of the sensor without the needing to take off the thermowell or opening the terminal head.


This is especially useful for the calibration cycle since you can remove your sensor, calibrate it and install it again without any big efforts or demounting equipment. Remember that the accuracy of the sensor is crucial for this kind of applications and the calibration is done at least once a year. In a normal plant, there are tens if not hundreds of measurement points.


The neck as per all other components of this thermometer complies with the hygiene standards established by organizations like Triple-A or FDA.

This is one of the most advanced temperature sensors available in the market today.

But is not the most advanced…

What I have here is the preview of the TrustSens from Endress+Hauser, and they were kind enough to send a demo device.

This is a self-calibration sensor. If you want to learn more about this device, subscribe to our youtube channel and newsletter.

Next week I will present TrustSens, in the meantime, thank you for watching! Until next time. 

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