15: milk milk milk two

haven't been posting much...too much homework/ tests and procrastinating. TT"

i've been researching a bit more on foaming milk and etc. milk is commonly foamed or frothed as an addition to certain coffees and beverages.
the process used to froth milk for use in coffee is different to my method for this experiment. to froth milk, a "steam wand" forces steam into the milk and forms tiny bubbles. the milk is heated during the process and the heat can affect how well milk foams.
when you steam milk (which is what frothing milk with steam is called), the proteins in the milk is the most important element in creating the tiny bubbles of air.

When you are steaming milk you are incorporating air into the milk. Proteins are
important because they are adsorbed* by the thin film surrounding an air bubble
giving stability to the entrapped air.

*adsorb: to gather (a gas, liquid or dissolved substance) on a surface in a condensed layer [http://dictionary.reference.com/browse/adsorb]

the stability of milk foam can vary depending on the milk's fat content. at around 5% (including whole milk), foam stability is at its lowest, meaning that as the fat content increases or decreases from 5% the foam becomes more stable.
foam volume is similar to foam stability as it is at its lowest when milk contains around 5% fat (including whole milk). skim milk supposedly has the greatest potential to produce a high volume and stable foam since it contains hardly any fat. as the fat content of milk increases from around 5%, the milk's ability to produce a foam with high volume and stability also increases.
because these observations are based on steaming milk, i am not sure whether they still apply to just shaking small quantities of milk vigorously for a short period of time. in theory, whole milk is the worst choice for producing a foam with a large volume.
it is said that low fat milk takes on the most air at lower temperatures, but this also applies to whole milk and cream (although "to a lesser extent"). however, all milk, no matter of its fat content, produces the greater volume of foam at cooler temperatures (when compared to the foam production at higher temperatures). milk at room temperature also does not foam well (and it'll probably have gone off by then). therefore, cold milk (preferably straight out of the fridge) presumably gives the best foam.
[http://coffeegeek.com/guides/frothingguide/milk] <--really awesome source [http://coffeeinfo.wordpress.com/foaming-milk-without-steam/]

the coffeegeek website above also details two different types of protein found in milk that contribute to the formation of the bubbles in the foam of milk. i will probably discuss this later on, mainly for the research and to publish more posts. as most of the research from above has come mainly from the one website, i'll need to look for more sources to verify that the information i have above is accurate. :)

i also wanted to say that i've almost finished making my totally awesome test tube rack, using scrap pieces of cardboard, my chocolate crunchie box and the lid of a shoebox. just need to finish off the base.
i hope to start my experiment VERY VERY soon, since the report is due in 3 weeks (how depressing). the experiment will hopefully take no longer than a week because i'll probably need 2 weeks to analyse my results and perfect my science report.

13: milk milk milk one

i'm going to be starting some research on milk (from cows) to see if using different milks for my test liquids is a good idea.

milk is an opaque white liquid produced by the mammary glands of mammals. milk for human consumption often comes from cattle, sheep and goats. cow's milk is the most commonly consumed form of milk & is often processed into other dairy products such as cheese, cream, butter, yoghurt and ice cream. [http://en.wikipedia.org/wiki/Milk]
milk for consumption often goes through different processes before going on sale on supermarket shelves, such as pasteurisation and homogenisation.
pasteurisation is the process used to partially sterilise milk, resulting in extended shelf life. milk is heated to 72°C for at least 15 seconds and then cooled immediately. this destroys any harmful bacteria and micro-organisms.
homogenisation is a process used to prevent the cream in milk separating and rising to the surface. the process consists of passing the milk (under pressure) through very fine nozzles, allowing the fat globules to evenly disperse throughout the milk and thus creating a smooth, creamy texture and taste. [http://www.dairyaustralia.com.au/Products-and-Recipes/Dairy-Products/Milk.aspx]
milk can be separated into groups depending on what and how much of something it contains, such as fat.
regular or whole milk is milk that (usually) has nothing added or removed. it contains on average 3.8% fat and no less than 3.2%. this type of milk is both pasteurised and homogenised and has a rich creamy texture.
reduced fat milk has approximately 2% milk fat and could have added protein and calcium.
low fat milk has less than 1.5% milk fat and usually extra calcium added.
skim milk has less than 0.15% milk fat with extra milk solids added for taste. it has a more watery appearance compared to other milks and a less creamy taste.
evaporated of unsweetened condensed milk is a type of concentrated milk. the total number of milk solids is increased to 28% by the gentle evaporation of water. the milk is sterilized after being canned to eliminate harmful micro-organisms and to ensure a long shelf life. skim evaporated milk contains around 20% milk solids.
powdered milk is "an evaporated pasteurised milk concentrate, containing about 40% milk solids". it is dried to reduce the moisture content to about 3%.
[http://www.dairyaustralia.com.au/Products-and-Recipes/Dairy-Products/Milk/Types-of-Milk.aspx#]
[http://www.milk.co.uk/page.aspx?intPageID=43]
cream is the fat component of milk and contains around 48% milk fat in its natural state. it is the removed component of milk to make skim milk.
[http://www.dairyaustralia.com.au/Products-and-Recipes/Dairy-Products/Cream.aspx]

okay, i think that's enough research for now...as you can see, for all of these types of milk (& including the cream), i've mentioned the substances fat content. i'm hoping to use this to form my hypothesis. so far, i reckon that one of the thicker liquids such as evaporated milk might produce the best foam, based on the foam's volume and longevity. this still needs more research though, so i'll see. i'm not sure if i'll include the cream as a test liquid because it's not technically milk.
by the way, milk fat is "the fatty portion of milk" [http://en.wikipedia.org/wiki/Butterfat] and milk solids are "combined yield of fat and protein in the milk" [http://medical-dictionary.thefreedictionary.com/Milk+solids]. i'm hoping that knowing amount of milk solids instead of milk fat in some of the substances might not affect the order of least to most amount of fat content...i might ask ms zhang...

i'll hopefully start my experiment VERY soon, hopefully before week 6. good luck to everybody starting their experiment. :)