stow10: Now that you’ve described it I think, as Ilana does, that the problem is more basic and related to method. As described below, simply letting chocolate to cool isn’t reliable. I think what may be missing is an idea as to why the steps in the laborious process are necessary. I’ll try explain as I understand it below.
Originally posted by Ilana
tempering is a system by which time, temperature and movemeny or agitation are all necessary. You need to heat or melt the choc to a temp instructed by that particular producer as cocoa butter of different types has different needs. In gemeral for dark choc 45-49 C is good. At this point thereshould be very few crystals of any type left in the chocolate.
The key point about tempering is, it’s all about crystallisation. Chocolate, or more specifically, cocoa butter, doesn’t have a single-phase crystallisation. Put into layman’s terms that means the shape of the crystals can vary depending on what conditions they form in. However, as it happens only one of the forms is properly stable for chocolate – that which has the highest melting point, as it turns out. What you’re trying to do with tempering is to return the chocolate, once cool, so that all of its crystals are in this phase. The complication is, that if any crystals are present in a different phase, they can act as nuclei that promote further crystallisation in the wrong phase, “breaking” the temper.
The first step, as above, is the melting. You want to be absolutely sure that every last crystal in the chocolate is melted, so that there can be no possibility a rogue crystal in the wrong phase might cause large parts of it to solidify in the wrong phase. While in theory chocolate should come pre-tempered, and since the right phase is the highest one, merely melting it at all should be sufficient, in practice you can’t count on that. So you heat it to high enough temperature that it’s definitely absolutely melted.
If you keep it at this temp for at least 2 hours- all the better. Now you need to cool it down and mix.
Step 2 is to cool it down to the point where crystals do start to form. Again, in theory you could do this simply by cooling to the solidification temperature of the right crystal phase (31C), but in practice the temperature of the next-highest (wrong) phase is so close
that again, it would be virtually impossible to be that controlled with any volume of chocolate, at least using normal confectionery equipment. So what you do is cool it down to just the point where it starts to solidify. At this point, hopefully most of the crystals will be in the right phase but perhaps a few won’t. How do you resolve this problem?
You can do this by adding callets of choc that is hard and tempered. This cools the chocolate down and adds crystals.
This is one method, otherwise known as the “seeding” technique. The idea behind this approach is to introduce a concentration of crystals already in the right phase, encouraging the right crystallisation as explained above. BTW, the term “callet” is just a Callebaut term for a small round drop. Of course the seeding technique relies on you already having an additional supply of solid chocolate of the same type, which may or may not be the case. Other techniques don’t require that – with the penalty of being perhaps finickier to master initially. The basic idea is this, however: to bring the aggregate mixture into that critical temperature range where only the right phase will remain solid.
The way to look at this is as a marginal reheat of the solidifying portion of the aggregate. The solidifying portion, whether seeded or slabbed or whatever, is actually at a temperature below the range where only the right phase is solid. So by mixing it with chocolate above that temperature, the net temperature of the whole mass goes up, into the critical range. It’s also, therefore, equally possible to temper by bringing the whole mass slightly below temperature and then slightly raising it. Whatever the case may be, this mixing or reheating is Step 3.
You also need to constantly mix.
This is crucial throughout the process for 2 reasons: first, to keep the whole mass at an uniform temperature, for otherwise some parts will be cooler than others, and second, to distribute the forming crystals throughout the mixture so that at every location there will be crystals in the right phase to act as nuclei. This is a major reason why simply letting a mass cool undisturbed almost never works: because you can’t guarantee evenness of temperature or crystal distribution.
Milk chocolate is particularly finicky because the milk fat (butter, in essence), has its own crystallisation point, slightly lower than cocoa butter, and you must temper in the range where the milk fat solidifies with the cocoa butter in the right phase, even more narrowly distributed than the difference between the right and first-wrong cocoa butter phase. It’s a very sensitive emulsion that easily separates. Furthermore, overheating definitely breaks the emulsion once and for all, so you can’t heat as high either. I’m honestly surprised that you’ve gotten away with what you’ve done in the past – you’ve been very lucky. I would say definitely, profile your chocolates, i.e. find the melting point/crystallisation point/reheat point, then try again.