Can hot water disinfect and sterilize bowls? Don't underestimate bacteria, try these methods to kill them →

Author: Xu Dong, Associate Professor, School of Food Science and Technology, Central South University of Forestry and Technology

Reviewer: Han Hongwei, researcher at the National Food Safety Risk Assessment Center

gossip

Many people, when eating out, are accustomed to washing dishes with boiling water or tea before the meal. They believe that scalding the dishes before the meal can disinfect and sterilize them , so they can eat with peace of mind after that.

This habit is very common across the country, especially in Guangdong. In order to cooperate with consumers' pre-meal behavior, merchants have even thoughtfully prepared special water containers. So is this behavior of scalding bowls to sterilize just a sense of ritual, or does it really have a sterilization effect?

analyze

Bacteria are really tough.

Bacteria are common factors that cause foodborne diseases, and their presence cannot be ignored. The most common pathogenic bacteria in daily life are: Salmonella, Staphylococcus aureus, Vibrio parahaemolyticus, Escherichia coli, Listeria, Vibrio alginolyticus, Bacillus cereus , etc. Due to their strong survival ability, these bacteria are widely distributed in nature. These bacteria themselves or the toxins they produce can cause various diseases and even cause death.

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The temperature and time required to kill different bacteria are different. For example, Listeria and Staphylococcus aureus are typical heat-resistant bacteria.

Listeria can grow in the range of 1-45°C, is not afraid of acid or alkali, and can withstand relatively high osmotic pressure. It can still partially survive at low temperatures of -20°C. It is also highly resistant to heat and can only be killed by temperatures of 60°C for 20 minutes or 70°C for 5 minutes [1].

The growth temperature range of Staphylococcus aureus is 6.5~46℃, and it does not require much external nutrition. It can survive for several months even in dry air, and it needs to be kept at 80℃ for 30 minutes to be completely killed. Among them, 30%-50% of Staphylococcus aureus will produce enterotoxin , which is also the main cause of foodborne diseases. Enterotoxin is extremely heat-resistant and will not be destroyed even at 100℃ for 30 minutes.

In addition, other common pathogenic bacteria need to be heated to at least 100°C for 5 minutes to be completely killed. In addition to the heat resistance of bacteria themselves, bacteria will turn into spores (a dormant body) in harsh environments. Bacterial spores have stronger environmental resistance and are highly contagious. Bacterial spores are more heat-resistant than bacteria themselves and can still survive after being boiled for 5 minutes [2].

There are many ways to sterilize

In order to fight against these tenacious bacteria and ensure human health and safety, various sterilization technologies have become increasingly mature. Currently, there are mainly physical and chemical methods for sterilization.

The most common and easy-to-use physical sterilization method is simply heating. As long as the temperature is high enough, the bacteria will die. If the temperature is high, you can bake/boil/steam for a shorter time. Otherwise, you need to heat it for a longer time. Pressurization and the presence of water can kill bacteria more efficiently.

For example, dry heat sterilization requires more than 120 minutes of continuous baking if heated to 160-170°C to achieve the purpose of sterilization. However, wet heat sterilization , such as high-pressure steam sterilization, requires only 15-20 minutes of continuous baking at a temperature of 121.3°C under a pressure of 103.4 kPa (1.05 kg/cm2) to achieve the sterilization requirement. Therefore , high-pressure steam sterilization has become the most commonly used and effective sterilization method in laboratories [3].

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In addition, there are some physical sterilization methods, such as steam disinfection, ultraviolet and ionizing radiation sterilization, filtration sterilization, etc. These are a bit far from our daily life, so I won’t go into details here.

The chemical sterilization method mainly uses some chemical drugs to penetrate into the bacteria to kill harmful bacteria. Commonly used high-efficiency chemical disinfectants include: chlorine-containing disinfectants, peroxide disinfectants, aldehyde disinfectants, alkylating agent disinfectants, etc. The chemical sterilization method has good bactericidal effect and low cost, but it is easy to leave residue. The concentration ratio needs to be controlled during use. It is generally not recommended for home use.

After reading the above labor-intensive sterilization methods, I believe you will better understand that using water to "sterilize bowls" before meals is just a psychological comfort.

Of course, there is no need to be too nervous. When facing germs, we also have sterilization methods suitable for daily use.

Sterilization at home is not difficult

So, in daily life, how can we use the existing conditions at home to effectively sterilize tableware and daily utensils?

In fact, we can also use the principle of thermal disinfection. The tableware can be placed in hot water and boiled for 10 minutes. This method is simple and easy to implement, and the effect is obvious. For tableware used by hepatitis patients, it is necessary to boil it for 10 minutes first, and then boil it for 10 to 15 minutes again to achieve the purpose of thorough disinfection [4].

Families with the means can also purchase a disinfection cabinet. Just put the cleaned dishes into the disinfection cabinet, leaving some space between the dishes, and set the time according to the instructions.

Both methods can effectively sterilize and disinfect tableware, further preventing the spread of bacteria and viruses.

In addition, we can keep the cupboards in our home clean and dry, wash the dishes in time after meals, avoid piling up dishes, and control the moisture in time after washing to let the dishes dry as soon as possible, so as to avoid the growth of bacteria to a large extent.

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Generally speaking, it is not recommended to use disinfectants on tableware. On the one hand, it is to avoid chemical residues caused by improper cleaning. On the other hand, the human body's own immune system is sufficient to eliminate small amounts of viruses, bacteria and other substances from the outside world to maintain the body's health, so there is no need for thorough disinfection.

Some friends may be worried that they are well protected at home, but what should they do when eating out? Here are some tips for you.

When dining out, you should choose catering service units that have a food hygiene license. In addition, you can choose catering units with a higher reputation level based on the country's dynamic grade (big smile, smiling and flat face) and annual grade (A, B, C) assessment of their restaurant hygiene conditions.

Before eating, you can also check whether the tableware has been disinfected. The tableware that has been cleaned and disinfected should be shiny, clean, dry and astringent. For people who are particularly concerned about hygiene or have weak immunity, they can choose to bring their own tableware when dining out . In this way, you can enjoy the delicious food while preventing "disease from the mouth" to the greatest extent.

As for the habit of boiling bowls, let it continue to add a sense of ritual to our lives.

in conclusion

Washing with hot water for just a few tens of seconds may remove some dust from the dishes, but the temperature and soaking time are far from meeting the requirements for killing bacteria, so naturally the desired sterilization effect cannot be achieved.

References:

[1] Zhao Huailong, Fu Liujie, Tang Gongchen. Major foodborne pathogens in my country[J]. Medical Animal Control, 2012, 28(11): 1212-1216.

[2] Molecular Biology[M]. Nanjing University Press: General Higher Education “Thirteenth Five-Year Plan” Planning Textbook, 201709.636.

[3] Food Microbiology Inspection Technology[M]. Chongqing University Press: A series of planned textbooks for biotechnology majors in higher vocational colleges, 201507.402.

[4] Zhao Fang. Discussion on tableware disinfection methods and disinfection effects[J]. Disease Monitoring and Control, 2013, 7(01): 48-49.

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