Ice Cream and Biotechnology

In my effort to whip up enthusiasm for the new academic year at the UTC, I thought I would draw your attention to the recent work by a group of scientists in Scotland. I was waking up to the Today programme on Radio 4 when I heard Professor Cait McPhee from the University of Edinburgh discussing how a protein could delay the melting of ice cream. Since I love the use of common concepts for teaching Biochemistry, I thought what a perfect combination: much better than milk and proteins that I have been using for a few years. I hope I have whetted your appetite; so what is the science behind this interesting news story?

The key to the Science is two fold. First, understanding the interfaces between air, water and oil (the three main ingredients of ice cream (well if you are a Biophysicist!). And second the way in which proteins can "bridge" different chemical environments through the inter-digitation of amino acid side chains. The reason that ice cream melts is owing to a break down in a structure, which is stabilised at low (freezing) temperatures. So how can we stabilise ice cream at higher temperatures; just for a little longer, to stop the above happening?

First what holds water molecules together? For this you can visit one of my old

Molecules of the Month: Water: Hydrogen Bonds of course! In order to keep the water molecules and oily fats "happy"  at the same time, Nature makes "amphipathic" proteins (from the Greek amphi (both sides) and pathos (experience: although this has a more specific meaning if you study literature and drama, perhaps "compassion" works for both?). The structure of BsIA (a bacterial hydrophobin) give us the answer. And work from the laboratories of Professor Cait McPhee in Edinburgh and Dr. Nicola Stanley-Wall in Dundee in Dundee, reveals the power of collaboration between disciplines (Biophysics and Microbiology). The two images above are taken from a paper describing the molecular basis for the amphipathic nature of this class of molecules called hydrophobins. The amino acid side chains shown in black at the top of this view of the molecule are the hydrophobic residues that interact with the oily components, while the underpinning parts have an affinity with the polar (water:compatible) elements of the ice cream. As Prof MacPhee said BsIA works by keeping oil and water mixed together, stops air from escaping and coats the ice crystals in ice cream which stops them from melting so quickly. She told BBC Radio 5 live: "This is a natural protein already in the food chain. It's already used to ferment some foods so its a natural product rather than being a 'Frankenstein' food. By using this protein we're replacing some of the fat molecules that are currently used to stabilise these oil and water mixtures so it can reduce the fat content, but it shouldn't taste any different. 

She went on to say, it also had the prospect of reducing the sugar content and could be used in other foods such as chocolate mousse and mayonnaise to help reduce the calories. So there you have the power of Biochemistry! By studying Molecular Sciences, you too can improve everyone's quality of life!