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Like Water for Chocolate - Testing Double Jackets for Leaks

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Posted 19 January 2015 - 11:59 AM

So this is a "chocolate" centric question I've had for a while -


I've been told a few billion times that water and chocolate is a bad combination.  I've said it a few billion times.  When we did our annual tank clean out we did not clean so much as scrape empty, let sit over night,  and look in with a flashlight.  Our mechanic (and our other site's mechanic) are vehement that if there was a leak in the water jacket "you'd know right away" because "water and chocolate don't mix". 


When we were doing our annual capex stuff, I requested $$ for pressure testing the double jackets.  Apparently we can't do this because none of them are pressure rated, and pressurizing them will cause them to burst.  Again, I was assured this was just fine because if water hits chocolate, it will turn the chocolate black and solid, and cause the resulting mix to clog the filters or self seal the hole.   Then the other site's mechanic said "Try it!  Just put some water in some chocolate and see how it turns into a black lump."


I happened to have some water and some liquid chocolate around, so I put it in a sample cup. It did not harden or turn black. I made chocolate mousse.  Actually adding water to it only thinned it and kept it from solidifying.  So I find it hard to believe that a pin hole leak would be instantly detected in a giant tank of chocolate. 


A few questions :


If money and time were infinite, would it be ideal to clean these out with a wet clean and let it dry?


We're doing to be installing some new tanks (hooray), isn't there usually a wet clean after installation?


We have a chance in April to scrape the tanks down again, and this time I want to dye the water so if there is a leak it will be easy to see after sitting over night.  Has anyone done this?  Does anyone have double jackets that they can not pressure test? 


Is visual inspection during an annual scraping an adequate control for leaking double jackets?  I understand the risk side of the risk assessment (leak = micro risk  + reduced quality), but I'm not fully confident in that as a control. 



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Posted 20 January 2015 - 07:02 AM

Magenta if you are not aware Cadbury chocolate had a large problem with salmonella caused by water dripping on a line a few year's back.  I know the consultant went in there to help address their food safety issues.  It was estimated the recall, loss in sales etc. cost them £40 million.  Just FYI until you get a response.

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Posted 22 January 2015 - 07:06 PM

Magenta, as chocolate mass is a water-in-oil emulsion, we can imagine that the amount of water you put in the cup was high enough to invert it and so, the formerly continuous phase (cocoa butter) became the dispersed phase and vice versa. That's why that 'chocolate' did not harden. On the contrary the more water you were adding the thinner (less viscous) the chocolate was.


When you have a leak in a tank the water proportion is much smaller. What usually happens is that viscosity will start increasing dramatically, the stirrer will stop and chocolate will eventually harden.


Hope it helps.

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Posted 22 January 2015 - 07:45 PM

Pandu is right. 


I have years of experience with chocolate tanks.  Double-jacketed tanks are not designed for pressure, so any pressure (above atmospheric) can cause the walls will bow, which in turn, causes all kinds of problems.


We clean our tanks regularly using scrapers and cocoa butter, then wipe clean with towels to bare metal.  We use an ATP tester and have, in the past, taken swabs for environmental monitoring.  We almost never wet clean them because ours are made from carbon steel, not stainless.  You can clean with water but make sure the tanks are nice and warm, and dry them immediately to prevent rust.


Even a small leak in a tank wall will cause chocolate to behave abnormally. If you suspect a leak, I'm sure you can clean the tank and conduct a bubble leak test to identify the location, but it might be easier to let the tank sit empty and unheated for a few hours and look around with a flash light.  I don't think you need to dye the water because any water in a dry tank (or even a scraped tank) should be visible, and if the tank isn't heated, the moisture should stick around long enough to spot.


If you are concerned about potential micro problems, test the water that is being circulated in the tank's jacket. That way, on the very remote chance that you have a leak, you'll know that no nasty stuff is getting into your chocolate.

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