Are curds good for humans? Or is it bad?

[chiazuohui]

Hello everyone, my group is doing a project on curds and curdling of milk. Our project title is "How do the amount of acid and amount of fats in fresh UHT cow milk affect the amount of curds produced".

We are now conducting our research and we would like to find out more about curds and whether is it good for us humans. However, we could not seem to find any relevant websites on this, so we would like some help.

The question we want to ask is: Are curds beneficial to human health? Why or why not?
Also, we have been pondering over this question: Can we measure the amount of fats in the milk by looking at the nutrition facts of the packaging? (we will look at amount of fats per 100ml)

We hope you are able to help us with these questions. Thank you!

[chiazuohui]

Oops , sorry. I forgot we have more questions. Anyway, this is the procedure for our experiment. We have not confirmed it though as we are still researching.
(this is for the acid part)
1) Slowly warm and whisk the milk in a saucepan until it comes to a simmer.
2) Add varying amounts of acid to 100ml of each type of milk. [is 100ml of milk suitable?]
3) Remove milk from heat.
4) Allow milk to cool and then strain it.
5) Measure the contents of the strainer (curds) by weight and record them down.
6) Repeat experiment 3 times to ensure the accuracy. Record the results down.[should we repeat 3 times? or more/less?]

[after calculating the amount of fats, we will check which milk produces the least curd and which produces the most curds. e.g XXX milk -- fats: xx grams, acid: 10ml < -- x grams of curd. Then we will try out another amount of acid ( should we use lemon juice?) and check which combination produces the least curds etc]

for the fats part, we are still not sure how to calculate the amount of fats in the milk. We are considering counting the percentage of fats, but we do not know how to do so. Hope this does not take up too much of your time! And thank you once again for helping!

[deleted-71827]

Hi!
Great question- I found some websites online that might be of use to you:
http://3webinfo.com/search.php?q=curds%20human%20health
http://www.enotalone.com/article/7992.html
Keep in mind that yogurt is really just another name for "curds". Also, if you are interested in measuring the fat content of milk, I think that the nutrition label would definitely be a good way to start, since there are much more high-tech ways out there which may/may not be accessible to you (as you can see in this article: http://jds.fass.org/cgi/content/full/88/2/478)
Hope this helps!

[chiazuohui]

We changed our project idea. Now we are trying to find out whether natural acid or rennet would curdle the milk faster. However, we do not know where to find rennet, and how to measure how fast the milk curdles. How do we recognise whether the milk has curdled until the maximum point?

[deleted-71588]

we do not know where to find rennet

Try searching for "rennet" in your favorite commercial search engine. Using Google, I found several adds offering rennet for sale.

how to measure how fast the milk curdles. How do we recognise whether the milk has curdled until the maximum point?

Enzyme reactions tend to start slow, speed up and then slow down with a long depletion tail. This usually means there isn't a well defined "maximum point". Coming up with a repeatable means of measuring how much curdling has occurred is going to be a challenge. You might try using a strainer or cheese cloth. Measure the tare weight of identical containers, start the reaction in one, at some point in time, pour the contents through a strainer into another container and weigh the liquid that passed through. You can do this at several times at different points in time and plot the remaining liquid weight at those points in time. If you use this method, you should think about the inherit errors that will occur and try and minimize them. For instance, cheese cloth is absorbent so you will want to use the same cloth for each of the time measurements for a given sample so you only have one "wetting" loss. You will want to use a different piece of cloth for each sample so that the initial measurement conditions are replicated and not affected by previous measurements of a different sample.

[deleted-2574]

Hi chiazuohui,

To find places to buy rennet, please see:
http://www.answers.com/rennet?shop.x=1

Note: pepsin seems to replaced rennet, please see:
http://jds.fass.org/cgi/reprint/2/6/482.pdf

To find places to buy pepsin, please see:
http://www.answers.com/pepsin?shop.x=1

Thanks.

[deleted-2574]

Hi chiazuohui,

A better reference is:
https://www.sciencebuddies.org/science- ... p041.shtml

Please see the Bibliography and Materials and Equipment sections.

Thanks.

[chiazuohui]

Thank you to all experts who have answered our questions. We appreciate it a lot. We are doing our experiment now.

[deleted-2574]

Hi chiazuohui,

You are very welcome!

By the way, where are located (approximate location is fine, e.g. I'm located in NJ/USA)? I only ask because your post is timestamped 3:06 am!

[chiazuohui]

oh, I am located in Singapore

Anyway, our first experiment was a failure, but we learnt quite a number of things from it. For example, check whether the electricity is working before using it. Because we did not check, we wasted quite some time before realising that the electricity does not work. However, we are going to try again next week with some changes and improvements.

[chiazuohui]

Oh yes, we changed our project question again. We are testing different kinds of fruit juices as coagulator and substitute for rennet in places where rennet is hard to find.

Is the control for this project using rennet as coagulator? Is a control very important?

How do we know when the milk is simmering? Is it when there is steam and water vapour coming out, but not yet bubbling?

Thank you for taking time to answer our questions

[deleted-2574]

Hi chiazuohui,

I can answer one of your questions:

Simmering is the stage where there are tiny bubbles in the liquid and some steam, but before the liquid is in a full boil.
(The above comes from my wife who does all the cooking.)

I can't research your other questions for about a day, and maybe someone else can help out.

[chiazuohui]

Thank you! That was a great help

[deleted-71490]

chiazuohui :

A control is the standard you are testing against to see if the treatment has any effect. In your case there could be two controls -simmered milk only and rennet.

Good luck,

Matt Mulanax

[donnahardy2]

Hi Chiazuohui,

This is a very interesting project. I have just a couple of suggestions for your project. You will be comparing two methods of curdling milk in your project, so it’s important to understand the chemistry of what is happening in your experiment. When you write up your project, you will need to explain the science of your experiment. Milk contains a protein called casein, and the element calcium and casein will precipitate, or curdle only when calcium is available. Calves stomachs contain the enzyme rennin or chymotryptin, which curdles the milk as the first step in digestion after the milk is eaten. The curdling process allows the milk to stay in the digestive track longer, to allow better absorption of the nutrients. Rennin is a protease (protein-cleaving) enzyme, and its specific activity is to hydrolyze the peptide bond between phenylalanine and methionine (two amino acids). If calcium is present, the casein will precipitate.

http://en.wikipedia.org/wiki/Rennin

http://www.vivo.colostate.edu/hbooks/pa ... ennin.html

The isoelectric point of casein is about 4.6, and most proteins are least soluble at their isoelectric point. Milk has a slightly acidic pH of 6.7 and the casein is very soluble at this pH, and adding acid will lower the pH to the isoelectric point, causing the casein to come out of solution.

http://www.itisacqui.it/sitob/formagette/curdling.htm

http://classes.ansci.uiuc.edu/ansc438/M ... otein.html

Since you will be doing your experiment again, you might want to check the pH of the milk solution after you add the acid to see if it is close to pH 4.6

I have included a lot of chemistry here, and since you are in high school, I am hoping that you have had some chemistry. However, please let me know if you need a more detailed explanation of any of the terms. We do want you to have a very successful project.

Donna Hardy

[chiazuohui]

Hi,

What is isoelectric point? And thanks for the advice, I didn't know that there was a point where proteins are least soluble

[donnahardy2]

Hi Chiazuohui,

Good question. Proteins are composed of amino acids, which can have free carboxyl (COOH) groups or amino (NH2) groups, (all amino acids have at least one amino and one carboxyl group, but these are combined in a covalent peptide bond in proteins). Above a pH of 4.5, and carboxyl groups will have a negative charge (COO-), and below pH 7, the amino groups will have a positive charge (NH3+). The pH at which the negative and positive charges are balanced and give the protein a net neutral charge is called the isoelectric point.

Here is a website that explains the general principle of isoelectric point:

http://en.wikipedia.org/wiki/Isoelectric_point

Here is some additional information about isoelectric point and characteristics of proteins:

http://www.chemistryquestion.com/Englis ... ation.html

Casein has an isoelectric point of 4.6, so is least soluble at this pH. In milk at pH 6.7 the casein would have more carboxyl groups ionized compared to protonated amino groups, so would have an overall net negative charge.

Does this information give you any ideas for your experiment?


Donna Hardy