A visit to an industrial bakery in Britain will usually reveal that its processing lines are continuous, from the make-up plant through to packaging. However, it is not often that you encounter a continuous or fully automated batch mixing system, although there are rare exceptions.
With plant bakers increasingly striving for a seamless highly efficient production process, it is surprising that more have not fully automated the dough mixing process. Increasing numbers, however, are beginning to evaluate continuous and carousel mixing systems for new plant or when refurbishing or replacing lines.
When doughs are mixed correctly, downstream processing should, all being equal, proceed smoothly. Make a mistake during the mixing phase and you can end up with issues to deal with all down the line.
Continuous automated mixing can improve the consistency of doughs - everything from stiff to highly developed - by helping to eradicate those variables caused by human error. By delivering continuously consistent dough, the dividers, sheeters, moulders, ovens and other plant elements can operate at their full potential without adjustments having to be constantly made. The result is a consistently produced quality product.
Moreover, with the built-in metering systems now available, any error is indicated and the opportunity to correct the problem - such as an ingredients error - is available before the dough goes down the line.
In a batch manual mixing system, the error may not be found until quality control tests are carried out at the end of the line, wasting valuable time and probably a lot of product.
Over recent years, a number of major producers have installed continuous automated mixing systems and this has focused the attention of the industry on continuous and carousel mixing and why bread, morning goods and savoury manufacturers have gone down this route.
So what are the other advantages of continuous automated mixing? Stewart Morris, a director of Epsom-based European Process Plant says that labour issues have always been top of the agenda. "Recruiting, training and retaining skilled labour remains a challenge and training is a thorny issue," he says. "If a new, partly trained employee makes a mistake, the results can be costly. Even when fully trained staff change shift or take their holiday, maintaining a process in which skilled workers play a key role, it can be very hard to guarantee product consistency over a period of time."
Dough as needed
Morris admits that many bakers can initially feel uneasy because they are used to seeing a large amount of dough being prepared for processing, whereas with continuous mixing they only get it when they need it. But he says that, in his experience, they soon get used to it. He also points out the benefits of this when there is a problem with a downstream piece of equipment.
EPP installs and maintains VMI carousel systems both rotary and in-line. This automated system comprises a loading station, one to six stations mounted on feet, a bowl elevator and a dough conveyor. A dough resting station can be added if required. The bowl passes from one station to the next by rotating around a motorised circle. The system can handle up to 6,000kg of dough an hour and is available with fork, single or double spiral mixers
The VMI in-line carousel combines a number of stations: dosing, mixing, dough transfer and resting and can automatically sequence the recipes. It is guided by an integrated process control system.
EPP also offers the VMI Verymix continuous mixer. The whole process - from gravimetric dosing through pre-mixing to final mixing - is run continuously. The Verymix guarantees dough of even consistency, says the company, and problems of scrap dough, variations in mixing, resting and fermented doughs can be avoided.
In the Verymix system, the mixing rotor can be adapted and the shape of the bowl designed for continuous mixing. Flexible and high-precision dosing with pieces of fat or liquid fat, scraps, special flours, eggs, dried or candied fruit and chocolate chips is straightforward, adds the firm. A triple- jacketed mixing bowl with liquid cooling to regulate the dough temperature with glycol ensures dough consistency and means a wide mix of doughs from 8?C to 30?C in capacities up to 8,000kg can be produced.
Morris concludes: "Installing a continuous mixing system is not as radical as many bakers may first think. All you are doing is bringing what is happening downstream back to the mixing. And the benefits can be huge."