1. Which Berry is the Most Acidic?



    Compare the acidity of different berries in search of a "champion" of acidity.  Is it true that the more sour a berry tastes, the lower is the pH–value of its juice?

    Research question

    Is it true that the more sour a berry tastes, the lower is the pH–value of its juice?


    Clean beaker or glass jar (100 ml). 
    Digital pH–probe, laboratory pH-meter, litmus paper or universal pH–indicators.

    Why use data from multiple participants?

    With GlobalLab students on-line, we will be able to explore a greater variety of berries and more effectively identify the most acid berries. With a larger data set we can better explore the relationship between the taste characteristics of different berries and pH–values of their juices. 

    Investigation Protocol

    In this project we will investigate the fresh juice of ripe, juicy berries. The study cannot use store-bought bottled or canned juices, as these may contain additives of preservatives, sugar, and dyes. The presence of these additives can change the pH of fresh real juice.

    1. Choose a berry you want to study.  It can be either collected by you or bought at a store. 
    2. Take a picture of the fruit. Be sure to sign each photograph: "This picture was taken by (your first and last name, or your GlobalLab Nickname.)"
    3. Rinse fruit and dry it, preferably using paper towels. If the fruit is a drupe, a fruit with a central stone such as plum or cherry, first remove the stone. Collect 200 g of ripe juicy fruit and then squeeze the fruit to obtain the juice. 
      To squeeze the juice of juicy fruits, they usually must first be crushed in a blender, for example, and the resulting puree then wrapped in a linen cloth or cheesecloth that is folded in several layers. Squeeze the resulting bundle strongly.
    4. Determine the acidity of the juice you have prepared. Measurements can be taken with a digital pH-probe, a laboratory pH-meter, or paper pH–test strips.
      If you are using a digital pH-probe or a laboratory pH-meter, it will help to check its calibration. (For this you can refer to the Project ‘Getting on the Same Page’). Repeat the test three times, rinsing your instrument each time between measurements thoroughly with distilled water, and wiping it dry with clean laboratory filter paper or a paper towel.

      If you use paper pH–test strip, follow the instructions of the manufacturers.

      Read off the pH value.
       Repeat the measurement three times using each time a clean paper pH–strip. Enter the results of all three measurements in the Report Form. The program will automatically calculate the average pH–value, summing three pH–readings and dividing the total number by 3. The resulting average value will automatically appear in your Report Form for this berry. 

    5. Fill in the project Report Form. For every berry you decide to investigate, you will need to fill a separate Report Form.
    6. Follow the progress of the project, participating in the discussion of the results obtained by other contributors.

    Safety tips

    Never use an unfamiliar berry as it might be poisonous.

    Report Form Before filling in the Report Form, please read the Investigation Protocol