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pH levels vary among bacterial species. For example; acidophillic bacteria grow best at low pH. While alkalophiles grow better at alkaline (high) pH. Most bacteria grow best at high aw (>0.90). While few bacterial species such as xerophiles grow best at an aw of 0.6-0.7
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What pH and water activity levels do bacteria grow?
pH levels vary among bacterial species. For example; acidophillic bacteria grow best at low pH. While alkalophiles grow better at alkaline (high) pH. Most bacteria grow best at high aw (>0.90). While few bacterial species such as xerophiles grow best at an aw of 0.6-0.7
What pH and water activity (aw) levels do bacteria grow best?
pH levels vary among bacterial species. For example; acidophillic bacteria grow best at low pH. While alkalophiles grow better at alkaline (high) pH. Most bacteria grow best at high aw (>0.90). While few bacterial species such as xerophiles grow best at an aw of 0.6-0.7
Does bacteria grow quickly with potential hazardous foods with water activity .85 or higher?
Yes, bacteria can grow quickly in high water activity foods with a water activity of 0.85 or higher. This level of water activity creates a favorable environment for bacterial growth and can lead to food spoilage or foodborne illness if proper handling and storage practices are not followed.
Why do bacteria not grow in dry flour of powder milk?
Bacteria require water for growth and reproduction. Dry flour and powdered milk have very low water activity levels, which creates an environment where bacteria struggle to extract enough water to thrive. As a result, the lack of available water prevents bacterial growth in these dry powders.
Is it safe to eat feta cheese that is older than 6 weeks?
Probably not. Feta cheese is a soft cheese, which means there is a relatively high level of water activity in the final product. This high water activity means that there should be enough water in the product for some bacteria to grow. Over the course of one year, the bacteria in the cheese and any bacteria that may have contaminated the cheese would have had plenty of time to multiply to dangerous levels.
What are the benefits of high water activity?
It is easy to see the shortfalls of high water activity when you look at water activity only as a way to control the growth of bad bacteria, but what if you want bacteria to actually grow in your product? The other thing is that texture depends upon water activity, so if you need to change your texture, you could raise the water activity. Another thing that is important to remember is that browning reactions occur at different water activities and you can change the water activity to control browning reactions.
How does jam last for months?
Due to the high sugar content, the water activity is so low that bacteria will not grow. However, if given the opportunity, molds will grow on the surface.
What is the relationship between microbial growth and water activity?
Bacteria need water to stay alive that is why a very dry surface (or beef jerky) have no growing bacteria. Note that is for growing bacteria. If the surface or food gets wet, they can to begin to grow.
Bacteria do not grow well in food with high levels of moisture such as meat and cheese?
It is a false statement that bacteria do not grow well in food with high levels of moisture such as meat and cheese.
Can bacteria grow in distilled water?
Yes, bacteria can grow in distilled water if it is exposed to contaminants or nutrients that support their growth. Distilled water itself does not contain nutrients for bacteria to thrive, but if it comes into contact with substances that provide nutrients, bacteria can grow in it.
How does sugar lower water activity?
When sugar is added to a solution, it competes for water molecules, thus reducing the amount of available water for microbial growth. This lower water activity (aw) makes it harder for bacteria, yeast, and mold to thrive since they need water to grow and reproduce.
What laboratory apparatus will determine if a bacteria is alive or not?
One method is a petri dish because the bacteria would grow or not grow in a warm environment. Or a microscope because you could see any activity of the bacteria.
