Chocolate Temper

Cereal Bars – Efficiency & Waste Improvement


Cereal Bars – Efficiency & Waste improvementLauras International was asked by a major manufacturer of cereal bars to carry out an improvement project in their largest cereal bar plant. Much of the product range had chocolate coating, either as a drizzled pattern on top of the bar and / or a skirt along the bottom and sides. In the months leading up to the project the plant kept having problems with chocolate temper causing significant downtime. Tempering is a heat treatment for chocolate to lock in the right crystal structure and getting it right is important for quality. Properly tempered chocolate has a nice gloss on its surface, a snap when it breaks and a long shelf life. The equivalent annual cost of the temper problem was running at nearly £70,000 and even though the most experienced internal problem solvers had been involved and discussions had taken place with the tempering equipment suppliers the problem had not been solved.


The line was equipped with the leading equipment for chocolate tempering, enrobing and drizzling, and the plant had many years of successful experience running chocolate. The problem the plant were having with chocolate temper normally started half way into a production run, at which point they could not achieve the correct temper index when checked with a temper meter. As the run continued the temper index was dropping even though all the control point temperatures were in specification and stable. To overcome the problem the line had to be stopped and all the chocolate in the system had to be reheated, which lasted 2 hours during which no production was possible. The problem was occurring on every run and had been doing so for 4 months although it had been an occasional problem up to that point.

As the problem became worse adjustments had been made to the temper settings to levels outside the specification. Whilst this could help at times it had not solved the problem. People on site were blaming a change in the type of chocolate being used, some said it was the tempering unit and others thought there was a problem with the enrober.


The team used PCS and found a single root cause which was de-seeding, an area that had been previously overlooked. De-seeding works by raising the temperature of the chocolate to a level that removes all of the crystals in chocolate returning from the enrober to the hold tank. Only de-seeded chocolate can be given the correct temper as it flows through the tempering unit back to the enrober. The team found that the de-seeder chocolate temperate was too low. Inside the de-seeder chocolate flows through a number of tubes where it is heated to above 45 degrees but it was found that a number of these tubes had become blocked with product crumb and raisins. This led to increased flow rate through the remaining tubes and a lower chocolate de-seeding temperature. This also explained why reheating all the chocolate in the system solved the problem for a short period and then the issue returned during the next run. The reheat de-seeded all the chocolate in the system but during the run seeded chocolate was then building up in the hold tank which could not be properly tempered.

The de-seeding unit was unblocked over a weekend and on restart the problem did not re-occur and has not happened since.


  • By eliminating unstable chocolate temper the associated unplanned downtime has been eliminated saving £70k per year
  • The driver tree from the project is now available as a detailed problem solving guide in case further problems arise in future
  • The function and importance of the de-seeding unit is now understood and controls are in place to prevent further blockage
  • A temperature monitoring system on the out feed of the de-seeder is in place to give an early warning of any issues