Pique the Geek 20120212: The Things that we Eat. More on Milk

(10 pm. – promoted by ek hornbeck)

Two weeks ago we began a short series on milk, in particular cow’s milk, used as a food by humans.  We mentioned that humans are the only species to drink any kind of milk after infancy (unless we feed it to animals).  We also mentioned that human milk is the very best food for human infants.  Next week we shall end the series by talking about the advantages of real milk to infants unless readers would rather see a discussion of cheese first.

Last time we pretty much focused on fresh milk and few derivatives of it.  This week we shall look at some of the derivatives of milk, either fresh or fermented.  There is a marvelous variety of liquid milk derivatives available, and some are very delicious.  In addition, there is butter which obviously is not liquid.

For a product as perishable as milk, it is amazing that so many wholesome fermented products can be made from it.  There are reasons for that, and we shall get to them in due course.

If milk is allowed to stand, the cream will begin to rise to the top (unless it is homogenized).  In modern practice, milk is separated from cream in large centrifuges to make the process faster, and then is blended back into the skim milk to provide whole milk and reduced fat milk.  It is not blended back into fat free milk.  Not too many years ago cream was in greater demand than it is now.  With much higher demand for reduced fat and skim milk, and a reduced demand for butter, cream is a bit more abundant than it was.  In the old days, some milk processors would buy milk from Jersey and Guernsey herds that have much richer (higher in butterfat content) than the milk from the by far most common dairy breed, the Holstein.  This is not needed as much now.

Cream is an interesting substance, or rather set of substances.  I have counted at least 12 different kinds, if one includes half and half.  The differences in properties is a direct function of butterfat content, starting at around 10.5% in half and half and up to 85% for some of the heavy plastic creams.  In the US we mostly see half and half, the so called heavy whipping cream at around 38% butterfat.  Once the butterfat content gets close to 50%, the cream is much more viscous than whipping cream and is used as a spread in place of butter.

In the old days, after milking the cow, the milk would be allowed to stand for a few hours and the cream skimmed off and pooled with the past day’s cream.  The milk, being much more perishable, would then be chilled (my grandmum put it in sealed jugs and lowered them into her well back when she was young) and the cream allowed to remain at room temperature overnight to “ripen”, or begin to grow lactose consuming bacteria.  If it were really hot, she would put the cream part way down the well, but not in the cold water, except for the cream that was intended to be eaten as cream and not churned.  That cream got chilled right away.  The next morning the cream would be churned into butter.  Cream that naturally separates from whole milk of around 3.5% butterfat will contain around 20% butterfat.  Jersey cows produce milk with up to 6% butterfat, so their cream is richer everything else equal, up to around 35% butterfat.

The liquid left over from making butter is authentic buttermilk.  Because of the lactose digesting bacteria, the buttermilk had a slightly sour taste and was greatly esteemed for baking because the acid in it would react with baking soda to leaven quick breads.  In those days baking powder was not available, but soda was.  Note that all of these bacteria were “wild” in that whatever was floating in the air became the culture.  Now and then some bad bugs would get to the cream and that batch would have to go to the hogs.

Now days, what passes for buttermilk is actually whole, reduced fat, or skim milk that is pasteurized and inoculated with specific bacteria cultures, kept at a controlled temperature until enough lactic acid has been produced, and then chilled.  It is quite unlike real buttermilk because the traditional buttermilk was made with cream, not milk.  You can make authentic buttermilk at home this way.

Buy a pint of whipping cream and pour it into a quart Mason jar, and leave it open and on your counter overnight.  Take a clean spoon and taste a couple of drops.  It is tastes sour, you are good to go.  If not, let it stand until it has a definite sour taste.  Now put a lid on the jar and shake it until the butter comes, usually around 15 minutes depending on your room temperature.  Modern whipping cream has some stabilizers in it so it might take a bit longer to get the butter, and since it is pasteurized it will probably take longer than overnight to sour.  You can cheat a little and add a tablespoon of store buttermilk in it as a starter.  Most commercial buttermilk is cultured with a mixture of Lactococcus lactis and Leuconostoc mesenteroides, but true home made buttermilk usually contains other lactic acid bacteria as well.

Once you strain out the butter particles, you have real buttermilk.  Chill it and enjoy.  You can also use the butter that you just made on toast or whatever you like.  This butter will not keep very long, but read further down and I shall tell you how to make it keep.

Cream has a very interesting physical structure.  The globules of butterfat are surrounded by a protective membrane composed of phospholipids and and proteins, and those keep the cream from turning into butter.  It the mechanical damage of churning that allows butter to come.  The membrane also prevents attack from enzymes in raw milk that tend to degrade fats.  This is not an issue with pasteurized cream.  Those membranes are quite robust, at least as far as heat goes.  It is easy to reduce cream by simmering it, but milk just curdles because of the proteins in milk denature and form long chains.  On the other hand, freezing either milk or cream ruptures the membranes, so whole milk and any cream curdles upon freezing.

Whilst we are talking about cream, we should look at the science behind whipping cream.  Whipped cream is very much akin to tiny air cells surrounded by very thin butter walls.  During whipping, the butterfat globule membranes are damaged, just like in churning.  However, air is rapidly introduced by the beaters, so instead of forming butter particles, the damaged membranes form a framework around the air cells.  This makes a couple of factors important.  First, you want the butter mesh to be quite stiff, so the cream needs to be very cold.  The bowl and beaters need to be cold, too.  My normal practice is to pour the cream (already cold in the refrigerator) into the mixing bowl and put them, along with the beaters, in the freezer for 15 or 20 minutes.  The sugar that you plan to use should also be put there.  Then working fast, whip the cream until it just starts to thicken, than add the sugar in divided portions until you get it sweet enough.  I have never had a batch of whipped cream to fail using this method.  Another trick, which I have not had to use, is to add a little lemon juice or cream of tarter to acidify the cream a bit.  That destabilizes the protective membrane from the butterfat globules, making the butter easier to come.  This is also why in the old days the cream was allowed to sour before churning to make butter.  Keep your whipped cream in the coldest part of your refrigerator until serving time, and put it back in the refrigerator right away.

Cream can also be whipped by dissolving nitrous oxide in it under pressure.  When the pressure is released, the nitrous oxide expands and fills the cream with bubbles.  That is the principle behind products such as Redi-Whip and the Whippets devices that can be bought for home use.  The advantage is that it is very fast, and only the amount of whipped cream needed is produced, because it is made on demand.  It is a relatively expensive method, though.

We may as well finish up butter now.  Most US butter is the sweet cream kind, meaning that it is churned from unfermented cream.  Modern churning equipment is efficient enough that greater acidity is not necessary to make the butter come, so it is cheaper to process the cream immediately rather than to take up valuable factory space and time allowing the cream to sour.  Sour cream butter is available, but not common in the US.  Pasteurized cream is cooled and aged at around 40 degrees F or lower to rupture some of the protective membranes and then warmed up a bit so that a significant portion of the butterfat is liquid.  This is important to make the globules stick together, just the opposite of whipped cream, where the globules sticking together would ruin the whipped cream.  churned until the butter “comes”.  Usually, the butter particles are a little bigger than rice grains and the buttermilk is strained off of them.  In modern practice this liquid is generally used, after dehydration, for animal food.

The grains of butter are washed with cold water and worked to make larger pieces.  After the first working, the mass is washed again, then there is more working and more washing.  The goal is to get as much of the liquid phase worked out of the butter, because butter is much, much more stable to decay than the entrained buttermilk.  In the US the legal standard for butter is no less than 80% butterfat and no more than 16% water.  The remaining four per cent is composed of leftover minerals, proteins, and lactose from the buttermilk that can not be removed completely.

Traditionally, most butter was salted, and the salt (at around 1% to 2%) acted as a preservative.  It is available in the US as either salted or unsalted, and when I read recipes that call specifically for unsalted butter and then call for salt, I sort of laugh.  Personally, I always get salted butter and just cut out a tiny amount of salt if using one of those recipes.  Salted butter DOES keep better.  Now you know why the butter that you made earlier when making buttermilk will not keep.  It needs to be washed, worked, and in my opinion salted or it will rot in a few days.  If you work the butter that you made earlier, it will keep as well as store bought.  However, with only a pint of cream, you are not going to get much butter!

We already covered one of the primary fermented milk products, buttermilk.  It is sort of an incidental result of making butter, and now we will discuss milk products that are intentionally fermented to make new products that are not a byproduct of making something else.

One of the most popular fermented products is yogurt.  This material originated in western and central Asia, and depending on the region of origin is made of the milk of different dairy animals, but cow’s milk is the most common overall.  The traditional home made yogurt has several different strains of lactococci and lactobacilli, but the commercially made material usually is cultured with only Lactobacillus delbrueckii bulgaricus and Streptococcus salvarius thermophilus.  This combination works well because the Strep is active right away, then the bacilli kick in at around 0.5% acidity.

Traditional yogurt is made just with milk and cultures, but commercial ones often use lowfat milk boosted in protein content with either dry milk or more often the cheaper whey protein concentrate.  It often contains modified food starch, gelatin, pectin, or other additives to make it thicker.  Lots of yogurt on the market also contains fruit jam and lots of sugar.

The basic process is pretty simple.  A very important step is to heat treat the milk, at 195 degrees F for ten minutes to denature the protein lactoglobulin which interferes with the net formed by casein molecules.  Without heat treatment, a grainy product results.  The next step is to add the culture and allow the milk to ferment.  Temperature makes a big difference.  At high temperatures, say over 105 degrees F, a coarse product is usually obtained, but it only takes a few hours.  At around 85 degrees F the fermentation takes longer to complete, but the result is a much smoother and less grainy product.

Lots of yogurt is advertised to contain “good” bacteria (the primary fermentation ones do not survive to make it to our intestines) such as Lactobacillus acidophilus and species of Bifidobacterium.  These DO survive the acidic environment in the stomach and are highly beneficial in the gut.  Check labels.  The heavily pitched brands are quite expensive, and I am holding a store brand container that also contains those cultures that sells for a fraction of the cost.

It is easy to make yogurt at home.  If you also can your own jam, you can have better yogurt than you can buy for a fraction of the cost.  All you need are some empty yogurt cups (7 of them), a small ice chest, milk, and a cup of plain, unflavored yogurt (make sure that it says that it has active cultures).  Take 48 ounces of milk (assuming that you have eight ounce cups) and heat it to 195 degrees and hold that temperature for 10 minutes.  Then allow the milk to cool to around 95 degrees and stir in a couple of ounces of the yogurt.  If you want, you can add some dried milk before you heat the milk to make it richer.  Fill the last cup with boiling water and put it in the middle of your cooler, then fill the other six cups with the cultured milk and arrange around the central cup.  Close the cooler and the next morning you have plain yogurt.  Add whatever flavorings you like after the fermentation is done.

Frozen yogurt, at least most of it, does not have much yogurt in it.  Most of it is around 80% ice milk and 20% yogurt.  Ice milk is similar to ice cream, but with less butterfat than the legal standard of 10% minimum in the US to be labeled ice cream.  It is good, but has a lot of sugar.

Another popular fermented product in the US is sour cream.  It is similar to the creme fraiche from France.  The French product is made from cream with a butterfat content of around 30%, and sour cream has only around 20%.  Both of them are fermented with a mixed culture of Lactobacillus lactis and Leuconostoc mesenteroides, just like commercial buttermilk.  If you have ever had creme fraiche, I think that you will agree that it is better than sour cream.  It is also distinguished from sour cream in that you can cook it without it curdling because it has less protein in it than sour cream, and protein is what makes cooked milk products curdle.  You can make either of them easily.  For creme fraiche, take heavy whipping cream and add two tablespoons of cultured buttermilk per pint, mix well, and let it sit on your kitchen counter overnight (longer if your house is cold) until it is thick and sour tasting.  To make sour cream, do the same thing, but cut your heavy whipping cream by half with milk to reduce the fat content.  You can also enhance the buttery smell by adding a quarter teaspoon of citric acid (available in the canning section of stores) per pint before fermentation.  It turns out that the lactic fermentation turns citrate to the buttery scented material diacetyl.

Reduced calorie sour cream is more like yogurt, but of course tastes different because different bacteria are used for the fermentation.  It is made like regular sour cream, but less cream and more milk is used.  The no fat ones are skim milk, usually with added whey protein concentrate or dried milk, and vegetable gums, pectin, or gelatin added to thicken it after fermentation.

Around the world there are many different fermented milks and creams, and I will take a minute to describe two more.  One is the central Asian koumiss, made from mare’s milk.  This is quite popular in Mongolia and nearby areas.  It is a “wild” product in that pure cultures are not used.  Most of the work is done by lactobacilli, but another agent, yeasts, are also used.  This ends up being a tart, rich material with up to 4% alcohol and it is effervescent because of the carbon dioxide content.  In a sense, it is mare’s milk wine!

The second is something that I used to eat as a kid when we had the cow.  It is called clabber, and also known as curds and whey from the popular nursery rhyme.  It is made from raw milk, often milk that has been skimmed of the cream for making butter.  It was naturally cultured, so it varied from time to time, but usually was similar when the milk of a single cow was used.  The way my grandmum made it, as opposed to having fresh milk, was to allow the cream to rise overnight at room temperature.  If she wanted fresh milk, she would put the containers of milk in the refrigerator to allow the cream to rise.  Usually we needed more fresh milk than clabber, so most of the milk was refrigerated whilst the cream rose.

I did not really care for it that much, but she and my parents loved it.  Part of the reason was that back in the day, there was no refrigeration so it was difficult to keep milk fresh.  Thus, clabber was sort of a necessary thing to have to preserve milk for any length of time, except for putting it in the well like I described earlier.  People developed a taste for it, like some have for stinky cheeses.  My grandmum and parents liked it was salt and pepper, and sometimes with crushed pineapple.  Personally, I prefer cultured buttermilk for a liquid and cottage cheese for a solid.  Since it was made with wild cultures, the instructions on Wikipedia for making a “…somewhat similar food…” by adding buttermilk to regular milk are quite in error.  All you get by doing that is more cultured buttermilk!  I would be particularly interested in knowing if any reader has personal experience with clabber, as I strongly suspect that anyone younger than I have even ever heard of it except for the nursery rhyme.

Now it is time for a Readers’ Choice decision.  I can either finish this series up next week by discussing the unique benefits of human milk for infants that no formula can replace, or we can extend the discussion for another week by adding a treatment on cheese.  Please indicate in the comments what you would like.  I shall attach a comment directly under my “Tips and recs for…” tip jar, and please feel free to add your comment to that so that they are all in the same place.  I would have inserted a poll, but the last couple of times I tried it the polls did not work well.

Well, you have done it again!  You have wasted many more einsteins of photons reading this greasy piece.  And even though Ron Paul realizes that he will NEVER be President of the United States when he reads me say it, I always learn much more than I could possibly hope to teach by writing this series, so keep those comments, questions, corrections, and other feedback coming.  Tips and recs are also highly treasured.  I shall stick around as long as comments warrant (unless I get an invitation to visit someone) and shall return tomorrow around 9:00 PM Eastern for Review Time.  Remember, no science or technology issue is off topic here.

One final thing.  The other day I was rooting around on the University of Arkansas site, looking to see if my doctoral dissertation were available online.  Unfortunately, it is not but I did find the library entry for it.  Here is a link to the reference.  I shall keep trying to get a copy and post it somewhere if anyone is interesting in reading it.  I can not believe that I do not have a hard copy in my possession, and since I wrote it on a Commodore 64 (using Steve Punter’s WordPro3+) and saved to single sided 5.25″ floppies.  You have to remember, this was 1978.  Even if I still had the discs, I have nothing on which to read them.  I wish that I had kept the hardware and the software now!

Warmest regards,

Doc, aka Dr. David W. Smith

Crossposted at

The Stars Hollow Gazette,

Daily Kos, and

firefly-dreaming