Did you know that there are 1.14 million bacteria of 1,900 varieties per square centimeter in a normal refrigerator? Once you notice the first odors vaporing in the fridge, the bacteria growth is already out of control. Bosch’s new Triple Hygiene Guard refrigerator guards your food items from degrading by eliminating up to 99.999 percent of all bacteria. Find out how, Allen Wang and Liu Xiaodong equipped our new Bosch refrigerators!

Human life wouldn’t be possible without bacteria. We need them as part of our immune system or to create delicious cheese, for example. Despite many benefits, bacteria tend to have a bad reputation – especially when they start degrading fresh food items that we had planned to eat. Even though, refrigeration slows down the degrading process, millions of invisible bacteria continue living in our fridges. That’s why our Chinese colleagues have developed new hygiene features for the latest Bosch refrigerators that the local team launched in the end of February 2022. We asked Project Owner Allen Wang and Technical Developer Liu Xiaodong to tell us more about our new Bosch refrigerators in the following interview:

The awareness for health and hygiene has increased during the pandemic. Is that the reason for developing a fridge with a special hygiene guard?

Allen Wang: Even though, the pandemic has increased our consumers' attention for hygiene, that’s not the reason for developing our new special hygiene guard. We had conducted a comprehensive consumer survey already in 2019, showing that the most important consumer concerns for refrigeration in China are freshness and hygiene. That’s why we started our development process before the pandemic.

Please tell us more about the new refrigerator.

Allen: The Triple Hygiene Guard refrigerator includes the latest hygiene features to guard our consumers’ healthy diet. A patented gas sensor on top of the cooling area timely monitors the decay of food. Once it recognizes certain gases – so-called volatile organic compounds (VOC) – the refrigerator starts the purification process, equipped with active oxygen and negative oxygen ions. In combination, they eliminate more than 99 percent of all bacteria and viruses, sterilizing the fridge and removing 90 percent of all odors, thereby guarding your food. 

Wow, it’s exactly like a Guardian! How does it work in more detail? 

Liu Xiaodong: Active oxygen – or ozone – is a gas that can break apart many things, such as protein and DNA. The latter are essential components of bacteria and chemicals that make up various odors, like trimethylamine and methane thiol for example. This process is called oxidation. Since the affected bacteria cannot recover, the gas is a highly effective disinfectant and deodorizer. And after neutralizing the odors, the gas automatically becomes oxygen. 

Ozone sounds scary! Do consumers have to be afraid of losing healthy nutrition? 

Liu: Definitely, not! Our consumers do not have to worry a bit! The low level of ozone in the new fridge does not influence their food items in a negative way. The oxidation effect on foods only occurs at very high densities above 1,000ppb, which the Smart Hygiene module does not reach. In fact, the low level of active oxygen may even have some small benefits for freshness because it can eliminate the ethylene gas.

Which challenges did you face when integrating both the sensor and the oxygen into the fridge and how did you overcome them?

Liu: The biggest bottleneck within our development project was optimizing the software algorithm for the gas sensor’s sensitivity. We had to ensure that it correctly triggers the sterilization process, considering different using habits. Another challenge was finding suitable purification times for different odor levels to guarantee efficient sterilization. Finally, the active oxygen has a potential influence on the sensor. Thus, we had to balance detection function and oxygen concentration very carefully. In order to overcome all these challenges, we first worked out the basic algorithm. Afterwards, we simulated and tested it with various types of food, including not only fresh vegetables, fruits, and leftovers but also spoiled food items. Moreover, we conducted qualitative household tests with consumers, to get real feedback and to perfect the algorithm. 

So odors don’t stand a chance, right? Is there anything that the hygiene guard can’t tackle?

Allen: While the smart hygiene module can eliminate 90 percent of the standard odors, it can’t do magic! If consumers forget to dispose of a large amount of rotten meat, for example after the holidays, the fridge continually works on odor removal but can’t eliminate the cause. That’s why the fridge can also send push messages to consumer phones to notify them of any abnormal situations. 

We just launched the new Bosch refrigerators in China. What happens next?

Allen: Well, we are very excited about the recent launch and we hope, that our innovative cooling solution will be a hit with our local consumers. Once we know more, our global marketing and development teams will discuss further international rollouts. We can’t make any promises at the moment, though.