Clarifying Stock - Ice/Gelatin Filtration Part 2

So I explained in part 1 yesterday the process of Ice/Gelatin Filtration in this post, today I will show you how I got on when I put the theory into practice.

Lightly colouring veg for the stock

I started by making brown chicken stock using some chicken wings, an onion (skin left on to aid the colour of the stock), a diced carrot, few bay leaves, garlic cloves and whole peppercorns. I roasted the chicken wings first to help with the flavour and colour of the stock, and brown the veg in a saucepan for the same reason.

Lightly roasted chicken wings, I could have gone for more colour if I wanted

I added the chicken to the veg, making sure to scrape the sticky 'juicy bits' from the tray and added water to just cover everything, then set it over a moderate until it boiled, then turned it down to a simmer for about an hour. I made the point of not skimming any impurities and fat from the stock as I wanted to really test how well this method would 'clean' my stock.

 Un-skimmed stock being brought to the boil
 

After an hour a drained the stock and passed it through a sieve to remove any large particles.  It is CRITICAL that the stock is well seasoned  at this point to how you want the final product to taste, any seasoning added after the stock is clarified will cloud the stock. Allow the stock to cool completely and freeze overnight.  

Sieving the stock
 

The following afternoon I removed the stock from the freezer and placed it on some muslin that had been folded three times and set that in a sieve. I place the sieve on a large pan and place it all in the fridge to slowly defrost for the next 24hrs. Remember that defrosting in the fridge is crucial to ensure gelatin remains solid so it can filter the melting liquid, and the fat stays solid so it doesn't re-emulsify back into the liquid and leave us with a greasy stock.

Frozen stock on muslin - the white stuff is frozen fat. Tasty

All we need now is time... time and patience. Fortunately I had a day at Tante Marie to complete allowing me to be distracted by other matters before returning home to see the results... and here they are....

The stock had nearly all melted leaving a nasty looking residue on the muslin

Spot the difference... no prizes will be awarded.

I had the foresight to save some of the original stock for comparison purposes, and as you can see the experiment was a resounding success and I am very very happy with the outcome. Even the smell of the cold stocks vary considerably, with the clarified stock smelling fresher, or maybe crisper would be a better description!

So what are your thoughts on this technique?  do you think as I do that it could be a valuable tool in the kitchen or a waste of time?  Let me know below in the comments section....

Dylan

Clarifying Stock - Ice/Gelatin Filtration

Late on friday night I stumbled across an episode of Heston Blumenthals 'In search of perfection' on Youtube. In this particular episode Heston was trying to create the perfect Peking Duck, and one of the courses he was creating involved making a stock, a clarified one at that.



The traditional method (simplified) to clarify a stock would involve blending some meat in a food processor (if its a chicken stock you would blend chicken breast, for a beef stock... beef) along with some egg whites and add this mix to the cold stock.

The next stage would be to whisk the stock continuously with the egg-meat mix and slowly heat it all up on the stove. When it boils you would stop whisking, reduce the heat to a slow simmer for 45-60mins and keep an eye on it, too heavy a simmer will destroy your work to this point. As the mixture simmers, the egg white mixture will form a soft crust on top of the stock through which the impurities will rise and be filtered. (If there is no natural break in the crust through which the stock can bubble up, gently clear a hole with a ladle.)

Next, scald a clean tea towel or muslin in boiling water and wring out to remove the moisture. Line a colander or sieve with the tea towel and set it over a bowl. Slowly ladle the stock through the strainer being careful not to disturb the crust. Do not squeeze or press down on the contents of the strainer, or the stock will become cloudy; leave it to filter through the tea towel and strainer. Remove the strainer carefully and discard the contents. You may then degrease the stock in the bowl by pulling strips of paper towel across the surface. You would then admire your crystal clear consommé that you have created.

The difference between what Heston did and what I noted above, is that Heston uses a technique called 'Ice Filtration' or 'Gelatin Filtration' which appears to achieve the same result but with a number of differences. The process involves making a stock, straining it roughly and then freezing it. Once frozen you place it onto of a few pieces of muslin that you have lined a colander with, place it over a bowl, and put the whole lot in a fridge for a day or two until melted

The way this technique works is to exploit the gelatin in the stock. If you have ever made a jelly and tried to freeze it you will know it wont set properly. This is due to the ice crystals formed during freezing effectively tearing through the bond the gelatin has created. The same thing happens with the stock. The second part the gelatin plays is to then filter the stock.

As the stock slowly melts the muslin traps the gelatin, the gelatin then forms a net like structure that will allow water to slowly pass through it, but not all the impurities in the stock such as the sediment from the meat, veg and the fat. It has to be defrosted in the fridge to keep the gelatin solid so it can act as a net, and to keep the fat solid so it doesn't end up back in the stock.

Once complete one should end up with a crystal clear stock that is full of vibrant and undiluted flavour...

Tune in tomorrow and see the step by step process I followed to inorder to try and recreate this technique at home.  Below is the stock I made yesterday and the froze over night... will it indeed become crystal clear, or will be a complete failure!?!?!?!?!

Part 2 is available by clicking here 

 Simple brown chicken stock ready to go in the freezer

I would love to hear your thoughts on this method or the traditional one....

Dylan