Streaked bars

I'm so frustrated! The last four batches of chocolate I've made have been streaked, the temper is good but the face of the bars are streaked in yellow. I've tried everything. Initially I thought it was poorly tempered, but I've mixed the chocolate really well and tested for temper prior to pouring, I'm certain the temper is fine. I've scrupulously cleaned my chocolate moulds and polished with cotton wool so that isn't the problem. I've bought a fan to blow cool air across the moulds as they are cooling, and they are also cooled on a cool stainless steel surface, I previously used a fridge with the same streaked result. Can anyone shed any light on this, it's so frustrating!Katie
updated by @katie-partington: 04/11/15 03:03:42AM

Can you clarify---is it the air side or the mold side that gets streaks? If its the air side it might be too much air flow/turbulence.

It's the mould side, the air side is absolutely fine. They are large bar moulds (95g) and I've been wondering if they aren't cooling quickly enough, hence blowing air across them and putting them on a cool surface. I've been through all possibilities and close to giving up! I have pictures but no idea how to post them on here. Any advice appreciated.

They are good quality polycarbonate moulds which might make a difference?

How did you temper and how did you test the temper prior to pouring?

What was the the temperature of moulds before you poured your chocolate in?

I tested with parchment paper dipped into the chocolate, if it sets hard within three minutes I usually take take that as tempered. I use a chocovision rev v machine. The temper on the bars are fine, it's just the surface of the mould sued that is streaked.The moulds were at room temperature, which was about 12 degrees yesterday. Should the moulds be warmed or cooled prior to pouring? I've read different thinks. Any help appreciated.

We are talking 12 degrees Centigrade?

This would be a problem.

On industrial moulding lines moulds (cavity side) are beingheated up to 26-29C prior to pouring in tempered chocolate.

Reason:

Tempered chocolate will contain a certain quantity of desired cocoa butter crystals. This quantity will be sufficient to act as seeds for the crystailsation of the rest of the chocolate when cooled at the correct speed. Rest of the cocoa butter is still liquid

If you pour tempered chocolate into mould that is too cold liquid cocoa butter forms unstable crystal forms on the mould surface resulting in white areas, streaks and othe bloom.

On a more technical level following happens: when chocolate (containing liquid cocoa butter) contacts cold mould surface heat (energy) flows from chocolate into the mould. This results in the formation of cocoa butter crystals that have a melting point close to the mould surface temperature. Crystals that are formed at teperatures below 28-29C are not stable. Because this process happens very fast there is no time for the correct seed crystals created during tempering to grow and correctly crystalise the whole chocolate bar.

I would suggest warming your moulds up to 26-28C and trying again.

12C? That is probably way too cold for your chocolate. Try getting them to within a few degrees of your chocolate temp. It might help to get an IR thermometer to check the mould temp just prior to moulding.

Do you have airflow under the moulds? It is possible you could be trapping the heat given out as the chocolate sets. If not you could try putting them on wire racks whilst cooling and still use the fan, this applies if your fridge has glass or solid shelves rather than wire ones too.

Thanks so much for this, I've bought an electric blanket and we will be experimenting with heating the moulds prior to pouring and will then sit in a wire rack to allow cooling underneath as well on in the surface via a fan. Really useful info, thanks so much for your advice.

Just out of curiosity, do you know what the humidity % is in the room you're working out of? We had some issues with streakiness as well and we're able to solve it by bringing in a dehumidifier.

Just jumping in incase someone else has the issue.  I just got done dealing with this for about the past year.  Was thinking my chocolate skills after almost 8 years were in decline for some reason.  Turns out it was just my thermometer.

Sometimes I'd have streaks of lighter colored almost pale yellow on the mold side, and sometimes faint streaks on the back. Problem was it was inconsistent, even though tempering was being done consistently and it was passing the "spoon test"   After calibrating my thermometer I found that it drifted from being accurate at 32F but then was off by an inconsistent amount and wasnt accurate again until 233F.   

So, new thermometer and validating that it's properly calibrated solved the issue. Now I'm getting consistent temper anytime I try.

 

BTW: I thought it might be airflow, because I keep cieling fans on in the work area. So I turned them off with no change in temper. Some suggested humidity; but I live in a desert, where if I'm seeing 25%, it's a wet day.  But that can also affect things if you're in a humid area.  I do tend to keep my molds out at room temp, no heating or cooling of them specifically; then place them in a cold box at around 65-68F on a wire rack.