Most bacteria grow best within certain ranges of temperature, and have specific requirements related to their need for air, the proper amount of water, acid and salt. By controlling nutrients, water, temperature and time, air, acidity, and salt, you can eliminate, control, or reduce the rate at which bacteria grow.
A widely used method for heat sterilization is the autoclave, sometimes called a converter or steam sterilizer. Proper autoclave treatment will inactivate all resistant bacterial spores in addition to fungi, bacteria, and viruses, but is not expected to eliminate all prions, which vary in their resistance.
Generally, two methods of disinfection are used: chemical and physical. The chemical methods, of course, use chemical agents, and the physical methods use physical agents. Historically, the most widely used chemical agent is chlorine.
There are three levels of disinfection: high, intermediate, and low. The high-level disinfection (HLD) process kills all vegetative microorganisms, mycobacteria, lipid and nonlipid viruses, fungal spores, and some bacterial spores.
The autoclave has to be maintained at a temperature and pressure of 121 degrees Celcius at 15 psi for 15-20 minutes for the complete sterilization. Therefore, it cannot be used for the sterilization of heat-labile (heat sensitive) materials because these materials will melt and get damaged due to the pressurized steam.
The optimum temperature range for bacterial growth is between 5-63℃. This is known as the danger zone as it is dangerous for some foods to be in this temperature range for prolonged periods of time.
Examples of
high-
risk foods include : Dairy products (milk, cream, cheese, yogurt, and products containing them such as cream pies and quiches)
Examples of low risk foods include :
- Fresh fruits and vegetables.
- Bread.
- Most baked goods.
- Candies.
- Pickles.
- Honey.
- Jam and preserves.
- Syrups.
To use the two-stage cooling method, food must be cooled from 140 to 70 degrees Fahrenheit within two hours and to 41 F or lower within four hours. Using the cooling method ensures that food is cooled quickly and safely.
As a general rule, it is recommended foods enter their proper temperature zones within 2 hours. For cold foods, the food safe temperature is 40 degrees Fahrenheit and below. For hot foods, the safe temperature is above 140 degrees Fahrenheit.
The 'Danger Zone'
The coldest part of your fridge should be at 5°C or below as some bacteria can grow at lower temperatures than 8°C.Hot temperatures can kill most germs — usually at least 140 degrees Fahrenheit. Most bacteria thrive at 40 to 140 degrees Fahrenheit, which is why it's important to keep food refrigerated or cook it at high temperatures.
In dry air, the droplets remain smaller and lighter, allowing them to spread further. However, in more humid conditions, droplets can be larger and heavier, making them fall to the ground faster. On the other hand, hot temperatures are more likely to kill viral germs.
Wash at a temperature as high as you can – the higher the temperature the better the germ kill! 60°C or higher. Wash towels and bedding at temperatures above 60°C to till bacteria, viruses and dust mites. Tumble drying on hot will help kill the bugs too.
Bacteria on the surface of the bacon can multiply even when you store bacon in the refrigerator; cooking to 145 degrees Fahrenheit normally kills bacteria and parasites. Since it's hard to check the temperature of a thin meat such as bacon, cooking it crisp ensures that it's been heated enough.
160°F/70°C -- Temperature needed to kill E. coli and Salmonella.
To sanitize water for drinking, the Environmental Protection Agency (EPA) recommends boiling the water for at least 1 minute, at altitudes up to 5,000 feet. At higher elevations, water should be boiled for 3 minutes. So that's 212 degrees F (at sea level) to reliably kill bacteria and pathogens to make water potable.
The “Danger Zone” (40 °F-140 °F)
This range of temperatures is often called the “Danger Zone.” That's why the Meat and Poultry Hotline advises consumers to never leave food out of refrigeration over 2 hours. If the temperature is above 90 °F, food should not be left out more than 1 hour.The 2 Hour/ 4 Hour Rule tells you how long freshly potentially hazardous foods*, foods like cooked meat and foods containing meat, dairy products, prepared fruits and vegetables, cooked rice and pasta, and cooked or processed foods containing eggs, can be safely held at temperatures in the danger zone; that is between
As a general rule, it is recommended foods enter their proper temperature zones within 2 hours. For cold foods, the food safe temperature is 40 degrees Fahrenheit and below. For hot foods, the safe temperature is above 140 degrees Fahrenheit.
Foods that are potentially hazardous inside the danger zone:
- Meat: beef, poultry, pork, seafood.
- Eggs and other protein-rich foods.
- Dairy products.
- Cut or peeled fresh produce.
- Cooked vegetables, beans, rice, pasta.
- Sauces, such as gravy.
- Sprouts.
- Any foods containing the above, e.g. casseroles, salads, quiches.
The USDA says food that has been left out of the fridge for more than two hours should be thrown away. At room temperature, bacteria grows incredibly fast and can make you sick. Reheating something that has been sitting at room temperature for longer than two hours won't be safe from bacteria.
Before using any foods, check your refrigerator and freezer thermometers. If the fridge is still at or below 40 °F, or the food has been above 40 °F for only 2 hours or less, it should be safe to eat. If you're unsure how long the temperature has been at or above 40 °F, don't take a chance.
5 Answers. The USDA says refrigeration temperature should be 40°F (4.4°C) or below. If food is in there at a higher temperature (such as the 43-45°F the question mentions), for longer than 2 hours, and they're saying the food isn't safe.
The only way to kill bacteria by temperature is by cooking food at temperatures of 165 degrees or more. Bacteria also die in highly acidic environments like pickle juice.
Temperature abuse occurs when food items are not refrigerated promptly for storage or after cooking, or are refrigerated, but not at the right temperature setting.
5 Answers. The USDA says refrigeration temperature should be 40°F (4.4°C) or below. If food is in there at a higher temperature (such as the 43-45°F the question mentions), for longer than 2 hours, and they're saying the food isn't safe.
