Whip cream too much and you’ll end up with butter – sometimes desirable, and sometimes not!!! Using nitrous oxide cream chargers eliminates this as a potential problem because of the way that the whipping actually takes place – all explained in some detail on www.creamchargers.org.uk but I’ll summarize it here for your benefit
Cream is separated form milk and is effectively a mixture of milk and fat. This i turn has an aqueous and a fat based component. The interaction of these two is what gives cream its viscosity. To get the cream from the milk you simply let it float to the top and then skim it off – well that’s how to do it if you’re being old-fashioned – in the modern world it is centrifuged to speed up the process and make it easier to separate the cream into the different types (single, double, whipping etc)
Whipping Cream and making butter
Unless you are using the cream chargers and dispenser method then these two things are actually exactly the same process – so let me help you understand exactly what is going on…
Cream contains fat and proteins, these proteins surround the fat molecules – see a photo of it here – the process of whipping using a whisk is a manual process that literally strips away the protein from the fat blobules – this allows the fat globules to stick together so they can hold onto the air that is pushed into them during the whipping process.
Making butter is just a natural extension of this idea – it is just that you strip away so much of the proteins than the fats can actually stick together to form a solid – which is the butter – the protein completely separates into the aqueous layer to form the buttermilk – which is why buttermilk is so healthy, it contains the goodness of the cream (protein) but not the bad (fat)
Whipping with cream chargers
This process involves forcing nitrous oxide under great pressure so that it dissolves it the fat component of the cream. It remains inert and dissolved as long as the high-pressure is maintained (usually within a whipped cream dispenser). Once the pressure is reduced by squirting t out of the whipper and returning it to standard air pressure then the nitrous oxide can no longer be dissolved and will expand – as it does so then it explodes the protein/fat linkages which lets the fatty globules coalesce, however only partially which is why the cream created in this way wil only last for a few hours before gravity does its thing and pulls that lovely foam back down flat.
more about the science of making butter later but for now check out this reference here