Monday, December 13, 2010

I Scream, You Scream, We All Scream For Ice Cream!

I got myself an ice cream machine. The final choices were the cuisinart ice-50bc and the venetto classic. I read somewhere that the cuisinart production has been discontinued (indicating a possbile lack of spare parts in the future) and when I tested the machine at the shop, it was really noisy. Those reasons and the $700 price tag made me go with the venetto.

First thing I made was an apple blackberry sorbet. I used my own standard recipe which gives pretty decent results as a frozen block blended with a hand blender before a JAM service. The results were pretty good, except that I didn't churn the mix long enough so after ripening in the freezer, the texture wasn't as smooth as it could have been due to the formation of larger ice crystals.

After that pretty successful run, I decided to try my hand at ice cream. There was no other way but the vanilla way. I'm not a big fan but I do believe that the best way to judge the quality of an ice cream label is by tasting it's vanilla flavour. I made a standard creme anglais custard I learned at the coriander leaf and churned it. I didn't have vanilla pods so I used extract. The texture was amazing but the lack of real pods really showed in the flavour of the ice cream, it was also a little too rich. Probably too much heavy cream.

I had anticipated this though and only churned half the custard. I loaded up the other half with a copious amount of Irish cream and churned it, curious to see just how the alcohol content would affect the texture. The results were stunning. The alcohol lowered the freezing point even further and after ripening overnight, the ice cream was incredibly smooth. The liqueur had tempered out the richness of the custard and because of the amount I added, putting a spoonful into your mouth immediately released a bold but pleasant alcohol 'cloud'. Unlike the alcoholic ice creams from Skinny Pizza which were a little overpowering, this recipe is definitely a keeper.

Irish Ice Cream & Chocolate Fondant

The next day I decided to try something a little more exciting and prepared some salted caramel. I increased the proportion of whole milk to heavy cream and at the last minute decided to go gelato style as a further experiment so corn flour instead of egg yolks were used to thicken the custard. The custard tasted awesome after being cooled down in the fridge but after churning, the caramel flavour became too prominent. I must have burned it a bit too much. The texture though was really nice and I think the gelato style works best for me. The egg yolks in Singapore have a really eggy smell even when they're fresh from the market and this flavour becomes detectable in the ice cream, something I personally don't like. Gelato it is.

In the churner right now, I'm trying out a barley gelato. No corn flour here, just really thick barley water sweetened with melon sugar. Adding some lemon juice to make lemon barley might make it a nice local flavour palate cleanser. Next up is a water chestnut sorbet :)

Will post a recipe for gelato once I get the proportions right.

Wednesday, December 8, 2010

Sous Vide @ Home - Part 1

So it's my birthday in 2 days and instead of studying thin films and quality control, I spent the day online, reading up on sous vide functional principles, looking for equipment online and getting in touch with my inner geek :) damn the things people do when they have too much time..

Because a thermomix is just too expensive right now ($2500, but if you think that's bad, a pacojet costs $6000), I decided that one last birthday treat was in order but couldn't decide on whether to get a high power food processor, an ice cream machine or a sousvide supreme. Getting any of them would contribute a lot in the kitchen and getting all would be swell but at an average price of $700 each, it wasn't going to happen.

The food processor was last on the wish list and while the sousvide supreme is a really nice toy, $800 for the set up, EXCLUDING the vacuum sealer, was just too much. So, I decided to buy the ice cream machine and a low end vacuum sealer and build my own sous vide rig. I am studying to be an engineer after all, may as well put all that tuition to some use :)

A sous vide set up requires 3 basic components. Something to hold the conducting liquid(water bath), something to heat the conducting liquid (incandescent light bulb or heating element from an old electric kettle) and most importantly something that makes sure the temperature stays the same by switching the heating element on and off (equipment with a feedback loop to control the heater). I studied the product reviews and as much online literature about sous vide machines and decided to use the sousvide supreme, convection circulated design as opposed to the open top, thermal immersion circulators I used at the brewery which cost abt US$1200 for just that small box (PID controller) at the top left of the picture below. Wish I had this now :(

Beer kept overnight at 19°C for daily testing

The convection design costs less because it requires less equipment, you depend on convection currents as opposed to pumps to circulate the water in your bath. My own rig will use an old school mechanical rice cooker as the bath and heating element. The heat coming from the bottom should also create good convection circulation of the conducting liquid. The rice cooker is well insulated and has a fitted cover that will help maintain the higher than ambient temperatures with less energy. On the flip side, cooling it down will also be harder.

I study materials science and not electrical engineering so all the circuit diagrams for the amplifiers and other feedback units we study are truncated to black boxes on our diagrams. In any case, Singapore doesn't have a 'radio shack' analogue and sourcing all the individual parts seemed like too much work to complete my home sous vide machine. Instead, I got a PID controller unit online and 2 sets of platinum resistive thermal device probes. I chose to use RTD probes because sous vide is a process that can take a long time, up to 72 hours in some recipes and this requires high long term accuracy. After a bit of research, I found the appropriate circuit diagrams and process codes here. Now all the GPA hammering shit from first and second year engineering, like C++ programming and electrical circuitry is reaping returns.

According to wikipedia, A proportional–integral–derivative controller (PID controller) is a generic control loop feedback mechanism (controller) widely used in industrial control systems – a PID is the most commonly used feedback controller. A PID controller calculates an "error" value as the difference between a measured process variable and a desired set point. The controller attempts to minimize the error by adjusting the process control inputs.

In essence, Proportional calculations set an initial or present platform to achieve the desired outcome. These are supplemented by the Integral calculations which using previous data, calculate feedback based on previous data and Derivative feedback are predictions worked out from current rates of change to ensure that the temperature stays constant to within 0.1°C with proper calibration. Compare this with a simple thermostat in an oven that switches on and off within a sinusoidal range of about 15°C peak amplitude.

I HATE math so I'm glad there're pre-written formulas from the circuit diagram site and that's why Man invented the computer, to do all that calculus :) $300, 4 hours and programming software courtesy of NTU later, I'm ready to rock and roll. This works out so much better than buying a sousvide supreme. By changing the size of the rice cooker, which costs less than $100, I can easily adjust the set up to sous vide items for 2 or 25 people in a snap. All this for less than half the price that the sousvide supreme is being sold at. I can already see myself cooking a 4kg ribeye sous vide and then searing the outside on the cooking plate I bought today.

Will update when I can, probably when the PID controller arrives. I hope this works! In the meantime, I will be reading up on this great free resource for sous vide cooking data.