Water has been called the universal solvent as it is a requirement for growth, metabolism, and support of many chemical reactions occurring in food products. Free water in fruit or vegetables is the water available for chemical reactions, to support microbial growth, and to act as a transporting medium for compounds. In the bound state, water is not available to participate in these reactions as it is bound by water soluble compounds such as sugar, salt, gums, etc. Comparing this vapour pressure with that of pure water at the same temperature results in a ratio called water activity aw.
Cup of water Procedure: Before you head out for your outdoor exploration and testing, collect your materials.
It would best if you had a small backpack or a friend to help you carry everything. Find a garden where you can collect about half a cup of soil. Make sure that the top of the soil does not contain any garbage.
Collect your soil sample from the soil that is a few inches below the surface. The best "garden soil" will be soil surrounding planted flowers. If the soil was actually bought from a store for the purpose of gardening, even better!
Label your sample with masking tape and a pen.
Next, decide on a more natural place to collect soil. This might be a river, beach, desert, grassland, or forest.
The best thing to remember about your "wild soil" sample is that the soil should be largely untouched by humans, hopefully from a place away from roads and buildings. Once again, make sure there is no garbage in the soil.
Label this sample as well. As you visit each site, make notes about the plants, wildlife, and other factors that might influence the soil in that area. If you were a tiny creature sitting on top of the soil, what would be falling on you?
Set up your science lab somewhere outdoors where no one will mind a bit of spilled dirt.
Pour out a small amount of soil from both samples. Use your magniftying glass to observe each sample. What is in the soil? Can you see chunks of plant? Make notes about your observations. Which sample do you think will have the higher levels of pH? Write down your guess, often called a hypothesis, in your notebook.
Now it's time to check the pH. The pH tells you how acidic or alkaline a substance is. Substances that are acidic measure less than 7 on the pH scale, and substances that are alkaline measure higher than 7.
A pH of 7 is neutral, which means it is in the middle. Take out the soil pH test kit. Place a tiny quantity of soil up to the line at the bottom of the kit. Remove the pH test capsule and sprinkle it on top of the soil. Add water until it reaches the top line on the kit.
Place the lid on the kit, and shake the contents. Continue to shake it for a few minutes, until it is thoroughly mixed. Let the contents settle before matching the color in the container with the color chart on the kit. What is the pH of your first soil sample?
Now repeat this pH process for your second soil sample and write down the results in your notebook.Microbiological controls using pH, water activity, inhibitors, and atmosphere will be described in this section.
Measuring pH. If a processor is using acidification, they must measure pH. including the approved uses and use levels, are included in the FDA’s Food Additive Status List. Water activity (A w) is a measure of the available water in a food matrix.
Water which is not bound to food components is available for microbial growth, so reducing the water activity is a reliable method of limiting the growth of pathogenic and.
pH-Control Problems of Wastewater Treatment Plants The control of water-PH plays an important role in these treatments, since each step takes place in a separate tank and the entire treatment requires several control loops to adjust the PH and is a primary measuring element and like other.
The technical definition of pH is that it is a measure of the activity of the hydrogen ion (H+) and is reported as the reciprocal of the logarithm of the hydrogen ion activity. Therefore, a water with a pH of 7 has moles per liter of hydrogen ions; whereas, a pH of 6 is moles per liter.
Tools for Measuring pH 7 Mandatory Tools 7 Optional Tools 7 How a pH Meter Works 9 pH levels can be used to determine the quality of meats. For example, 6 The Guide to pH Measurement in Food Drink pH can be measured one of two ways: By litmus paper, (sometimes referred to as pH .
Water activity or a w is the partial vapor pressure of water in a substance divided by the standard state partial vapor pressure of water. In the field of food science, the standard state is most often defined as the partial vapor pressure of pure water at .