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Is there a scientist in the house?

silvergirl Apr 1, 2012 11:16 AM

My second grader is doing his science fair project on curdling. We made paneer and then followed the same process with lactose free milk. Our hypothesis was that with no lactose to convert to lactic acid, the milk would not separate. However, it did. Is this because of the carrageenan and guar gum they add to the lactaid?

  1. jmcarthur8 Apr 2, 2012 06:27 PM

    When one of my sons was just a little tyke, he'd often come into the kitchen and ask me if he "could do a 'sparement". I'd haul out some food coloring, something liquid, some Dawn or some baking soda and vinegar, etc. and let him have at it.

    He graduated from Southern Polytechnic with a Biology degree last May, and now is in the US Navy in Nuclear Propulsion training.

    That's where 'sparementing gets you. ;-)

    1 Reply
    1. re: jmcarthur8
      nofunlatte Apr 3, 2012 06:27 PM

      Great anecdote! And it all started in the kitchen.

    2. AeroDoe Apr 2, 2012 02:46 PM

      When is your son's report due? I am trying to think of ways you can perform the experiment with a few adjustments. By heating it, you're actually helping the proteins to denature (curdling). I am trying to think of a buffer, or maybe even baking soda that would give you a chance to add an acid w/o destroying protein structure. The problem is that there are so many active compounds in milk. What I am thinking is that you leave samples A and B in refrigerator for a long time, and never add heat, and slowly add lemon juice. You wouldn't happen to have Litmus paper or a pool pH kit, would you?

      2 Replies
      1. re: AeroDoe
        silvergirl Apr 2, 2012 03:35 PM

        His project doesn't really have a due date since it's not for credit, but the science fair is Wednesday. I got him the McGee book at the library, and he found and read the curdling information, but I think too much more will be over his head. (not because he's not smart enough - he is, but science isn't on the standardize tests, so they don't teach a lot of it to second graders. So he doesn't really have a lot of background knowledge). I'm beginning to see why second graders don't generally contribute to the science fair. But I do like your idea. I may get him some litmus paper to experiment with over the summer.

        1. re: silvergirl
          AeroDoe Apr 2, 2012 06:15 PM

          I think it's wonderful that he's interested in experiments and Science at such a young age. And it goes without saying that if he wants to perform experiments, he's very intelligent. I've always considered curiosity and a desire to answer the "whys" of life as a sign of genius.

          What I like about pH, acids and bases is that it introduces him to the idea of the continuum. That in between black and white, acid and base, right and wrong, is the much more interesting gray area.

          How lucky he is to have a parent who shares his enthusiasm!

      2. AeroDoe Apr 2, 2012 01:58 PM

        That's an interesting experiment for a second-grader. Milk is made up of a lot of stuff. Usually with an experiment, you want to get a very specific product to work with. One whose properties are predictable. Milk is a soup full of Organic compounds, so there are gonna be a lot of reactions going on all the time. With lactose-free, the milk has been treated with an enzyme which breaks down the lactose, but afterward, there are still sugars in the milk. And when you add an acid to milk, the proteins denature, whether or not there is lactose in the milk. (Like cooking it with chemicals, as in Ceviche)

        1. jmcarthur8 Apr 1, 2012 05:34 PM

          Sounds like a successful experiment to me. A hypothesis is a guess, your son's object was to prove or disprove the hypothesis. Which is exactly what his experiment did. The next step in the process is to explain the outcome. It's okay if you help..as long as he learns how and why the result was what it was. I have two sons in their 20's, and they did a few science fair projects when they were kids.

          1 Reply
          1. re: jmcarthur8
            DonShirer Apr 1, 2012 08:31 PM

            JmcA is right on. I've judged state science fairs and am always sympathetic to those whose experiments don't come out the way they expected (if they are honest about it!) since the same thing happened to me when I was a kid.

          2. w
            wattacetti Apr 1, 2012 02:05 PM

            Chemicalkinetics has the correct answer so your child's theory has been disproven (not necessarily a bad thing - this is how science is supposed to work).

            The acetic acid (vinegar) drops the pH, which changes the conformation of the casein protein, causing it to come out of solution.

            1. Chemicalkinetics Apr 1, 2012 01:03 PM

              It is my understanding that curdling has much more to do with proteins than lactose. Lactose is really a disaccharide, not a protein. As such, when you denature the milk protein in acidic condition, the milk proteins will precipitate from the solution.

              2 Replies
              1. re: Chemicalkinetics
                silvergirl Apr 1, 2012 04:13 PM

                Thank you and also wattacetti

                1. re: silvergirl
                  Chemicalkinetics Apr 1, 2012 08:35 PM

                  Our pleasure. Best wishes.

              2. g
                GH1618 Apr 1, 2012 11:32 AM

                I suggest you read the explanation of curdling in On Food and Cooking by Harold McGee as a foundation for this experiment.

                What is your recipe?

                6 Replies
                1. re: GH1618
                  silvergirl Apr 1, 2012 11:41 AM

                  Thank you. I will take another trip to the library tomorrow while he's at school. It's one half gallon milk, 1/4 cup lemon juice. Heat milk to 176 degrees F, add lemon juice, watch curdle, strain.

                  1. re: silvergirl
                    GH1618 Apr 1, 2012 11:59 AM

                    The lemon juice is the acid which causes curdling, I expect.

                    1. re: silvergirl
                      PuniceaRana Apr 1, 2012 02:51 PM

                      With all due respect, since this is your sons project for the science far, shouldn't your son be doing the research, or at the very least going with you so you can assist him in doing the research?

                      1. re: PuniceaRana
                        Chemicalkinetics Apr 1, 2012 03:05 PM

                        Hmm, you have a good point, maybe I did make a mistake here. Afterall, learning science is about making mistakes and researching for answers. Answers which come too easy never really help -- in the long run.


                        It is probably better for your child to find out the answer on his own. I know it may feel tough not to help, but some time "not helping" is really true form of helping. At least, try to make the kid struggle a bit, and then maybe tell him the answer the last minute.

                        1. re: PuniceaRana
                          GH1618 Apr 1, 2012 03:07 PM

                          Come now, he's in the second grade! All she has proposed to do is get a copy of some pertinent background information, which she can then discuss with him. Give the kid a break — he has many years in which to learn how to do research.

                          1. re: PuniceaRana
                            silvergirl Apr 1, 2012 04:11 PM

                            He chose the project and performed the experiment. He is writing the report. He is reading what I give him, but highlighting what he feels is important. he is a second grader after all. He has done research, but only because the enrichment kids in his class did a special project last year. Most did not. I don't think helping him gather information is too much. Especially because the project is optional and won't be graded or judged. And if I take him to the library, I have to take my other two, smaller kids too. Which I do, just not tomorrow. My intention is to give him the book but let him find the answer. I won't help so much when he is a fourth grader and is graded/judged on his entry.

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