Consistent quality of liquid metering

Storing and supplying viscous and liquid dough ingredients for bakeries is a complex subject. Bühler AG showcases solutions for flexible, recipe-controlled supply.

“Ordinary” bread contains numerous constituents, some added as raw materials (flour, water, yeast etc.) and others as intermediate products (brine, bread slurry, cold- or hot-soaked grain). Correct handling and accurate metering of all these liquids according to the recipe are decisive requirements for consistent dough quality.

Liquid metering technology

Medium-sized industrial operations and large-scale bakeries use partly or fully automated processes to produce bread. These processes can take place continuously or batch-wise. Depending on the level of automation, a variety of production, processing and storage plants are used to implement the various baking recipes to yield a clean, hygienically faultless product and a reproducible process. The focus is always on a flawless, consumer-oriented end product.

Liquid raw materials are often delivered to the bakery in ready-to-use form. Depending on the quantity required, transport takes place in road tankers, IBC containers, drums or canisters. Suitable acceptance, conveying, storage and metering systems are available for each of these delivery units. The configuration of liquid systems in the areas of temperature adjustment, product activation, cleaning etc. is implemented in a customer-specific way. The emphasis is on handling raw materials hygienically and in accurate compliance with the recipe.

A few of the raw materials are used as intermediate products. Liquid yeast, for example, is prepared by dissolving block yeast in process water directly at the customer’s premises, after which it is stored, then added to the downstream process.

Sugar dissolver plants are used to produce various sugar syrups or invert sugar on the spot. Production of salt brine by the factory itself avoids transporting water, since only the crystalline component is delivered. These intermediate products, which can also include sourdough production, are then correctly stored and fed into the manufacturing process in the correct amount required in a given time.

Process water

In addition to flour, the second main constituent of bread dough is water. Water is used in a variety of forms. As well as direct addition as cold water, warm water or temperaturecontrolled water, a non-negligible proportion of water is also contained in liquid yeast or brine. Further amounts of water occur when processing cold-soaked grain or in residual bread recycling, and these must be balanced with the recipe. The simplest implementation of water metering is directly from a ring main. This necessarily involves monitoring the throughput flowrate and temperature and adjusting these in accordance with the recipe. For accurate, reproducible metering, the water should be provided at a consistent pressure and constant temperature, and in the amount needed per unit time. If the water temperature is optimum, the dough can be processed as required in the following process steps. The WinCos recipe control system calculates the correct water temperature by evaluating the various raw materials temperatures relative to the recipe-based dough setpoint temperature specifications. The energy input in the mixer and the subsequent dough resting time must also be taken into account as influencing factors. The result: a consistent quality of dough that accurately reflects the recipe and has optimum characteristics for further processing.

Constant conditions

In the bread dough manufacturing process, depending on the recipe, a proportion of yeast equal to approx. 2 – 4 kg of block yeast or 10 – 20 liters of liquid yeast (depending on the solution concentration) is added to 100 kg of flour. Liquid yeast can be delivered by road tanker or in smaller packages each holding 1,000 liters (IBC), or can be manufactured as a yeast solution from block yeast and water on the spot in a dissolver plant. In the latter situation, a mixing ratio of 1:4 (yeast to water) is aimed at in order to dissolve the yeast completely in the shortest possible time.

Because liquid yeast is extremely temperature-sensitive, the entire handling must take place under temperature-monitored conditions. The temperature is always already checked at the time of delivery/production of the liquid yeast in the context of quality control. Yeast is always kept at 3 – 8°C up to the mixer, to suppress the yeast’s “working”. A precondition for this on the plant side is functioning cooling and suitable storage, pipework and metering systems. Double-wall and/or insulated tanks and pipework ensure optimum process conditions.

After being blended into the dough, the yeast should become active. Best results in the dough in this respect are obtained at 30 – 38°C. The resulting fermentation gases form gas bubbles in the dough, which are subsequently responsible for the bread’s porosity. The yeast also forms fermentation byproducts, whose effect is to create flavor. In conjunction with acids, the resulting fermentation alcohol forms compounds that create flavor (esters), or evaporates during the baking process without leaving any residue and is no longer detectable in the finished bread.

Because yeasts are a critical hygiene factor in a bakery, special attention must be paid to suitable, successful cleaning. The whole system is regularly cleaned using a CIP (Clean In Place) cleaning process, and the results of cleaning are constantly checked during validation and in the framework of Quality Control.

Components of the recipe

As for yeast, attention must be also paid to strict maintenance of the cold chain for liquid egg or whole egg. An elevated hygiene risk exists here, since egg is an almost perfect nutrient substrate for a very wide variety of microorganisms, and the entire handling must be monitored accordingly. Quality control for temperature and microbial count is performed when product is received. All plant components must be cleaned regularly and at short intervals of time. The liquid egg is also passed through a sieve and over a magnet to retain residues of shell and other contaminants from the product. Tanks and pipework have a double-walled and/or insulated design, and maintain the prescribed operating temperature of 3 – 8°C.

Fats and oils in liquid or solid form are used in the production of bread dough. The proportion used is normally less than

1% relative to the flour. Lipids represent a special form of added fat, since they are used exclusively in molten form, are solid at room temperature, and denature at a temperature of 45 – 50°C and above. Handling them is correspondingly more demanding, because the operation must be carried out in a small temperature range to achieve a perfect result. The use of suitable plant is especially important here, and it must also not generate any excessively temperatures at the temperature boundary layer, so as not to damage the raw material.

Sugar and sugar products are frequently used in bakeries in dissolved form. Heated storage and transport conditions are often created for “liquid” sugars such as glucose syrup, invert sugar, honey or other flavored sugar solutions due to their high product viscosities. A temperature of approx. 40°C reduces viscosity enormously and provides a noticeable improvement in handling and metering the liquids. Special conveying and metering technologies can also be used to handle extremely temperature-sensitive raw materials at 20°C.

If bread is to be enriched by adding grains or flakes, a process is used to ensure the swelling of these products. The background to this is the addition of cereals to the dough in a way that promotes their consumption. If these ingredients do not undergo a swelling step and thus a water-absorption process beforehand, the grains could extract water from the dough and thus from the bread as well after baking, leading to dry, brittle end products. Another important reason is to soften the grains. What is known as a scalding process at a controlled temperature is often used for this purpose, in which a temperature increase both favors water absorption and causes slight denaturing of the constituents of the grain, leading to a softer result.

Optimum use of resources

Industrial bread manufacture produces offcuts and end products rejected at the quality control stage (size, appearance, color etc.), which can be recycled to the ongoing or planned future manufacturing process. In most cases, this so-called scrap bread is dried and stored, or sometimes even fed directly into a downstream dissolving process in which the residual bread is mixed with process water and dissolved by the input of mechanical energy. This results in a bread slurry that is fed into the mixer during dough preparation. This process is very vulnerable to microbial infection, because the bread slurry promotes germ growth due to its many nutrients and the presence of water. So hygienically faultless handling and implementation of bread recycling is ensured by suitable temperature management, possibly combined with a pigging system and suitably adapted CIP cleaning.

Depending on the recipe, a proportion of recycled bread below 6 – 20 kg is added to 100 g of flour when manufacturing bread. In this case there are country-specific definitions of the maximum permitted amounts that can be added. In Germany, for example, they are max. 20% for wheat breads and max. 6% for rye breads.

Bühler offers complete solutions for residual bread recycling: freshly-produced reject material is reduced in size, dried and ground to fine particles. The dry rework thus produced can be stored without mixing bread types, and added together with the other dry components of the recipe. Tests in Bühler’s Bakery Innovation Center have shown that it is possible to use dry rework without sacrificing quality, and with a simultaneous increase in dough yield by at least 2 percentage units. Baking loss is also reduced by approx. 5%. There is potential for a further increase in dough yield at the same time, thus allowing the water content to be increased further by up to 10% through the use of dry rework, while retaining constant product quality.

Reproducible sponge dough production

Wheat sponge doughs, wheat sourdoughs or rye sourdoughs influence the structure and texture of the dough, improve the bread’s aroma, and give it a characteristic flavor. Sponge doughs also extend the shelf life and microbial stability of baked goods. Bühler’s newly-developed sponge dough process using a JetMix guarantees the production and use of singlestage or multistage sponge doughs with consistent quality and dough yield. These sponge doughs are “started” correctly for the process and schedule by using a WinCos ® central plant controller and are fed directly into the mixer.

Through the 360° wetting of the flour curtain, the JetMix ensures maximum dough consistency and homogeneity at the same time. Metering the dry and liquid components takes place fully automatically, and their matching to one another is optimum. The dough is metered directly into the mixer or pumped into fermentation tanks. After production is complete, the whole system can be cleaned by pressing a button.

Cleaning in Place

Plants used for food production must be cleaned at regular intervals. This cleaning can take place manually, i.e. by hand, or an automatic cleaning system can be used. The “Cleaning in Place” (CIP) cleaning process adapted by Bühler for the bakery industry is an integral component of Bühler plants that process liquid recipe ingredients. The use of CIP ensures the highest level of hygiene and food safety in risk-prone process zones, e.g. in liquid yeast and wheat sponge dough plants. Use of CIP guarantees a safe, efficient cleaning process with reproducible results that can be validated.

Two different processes can be used for CIP cleaning. Noncirculatory cleaning (a one-tank system in most cases) discards the whole of the cleaning solution and rinse water after the cleaning cycle. In cascade cleaning (multi-tank system), the cleaning fluids are collected and used several times. A process known as “reactivation” allows the cleaning solutions to be used several times, i.e. until the contamination level is too high and a new solution must be started. The last rinse water of a cleaning cycle can also be reused as the first rinse water for the next cleaning. In the medium term, water consumption and the chemical requirement and thus the wastewater value are significantly reduced, with the same cleaning result. The personnel cost is also demonstrably lower due to the higher level of automation.

Successful cleaning depends on many different factors. The Sinner’s Circle originally drawn up for this process takes four factors into account:

+ Concentration (of the cleaning solution / 0.5 – 5%)

+ Time (for which the cleaning solution acts)

+ Mechanics (flow velocity / 1.5 – 2.5 m/s)

+ Temperature (of the cleaning solution / 20 – 95°C)

Because these factors are directly dependent on one another, when one of the factors is changed, one or more of the other factors must compensate for this change to achieve the same cleaning result. For some time, two more factors that also affect the cleaning result have been added to supplement these four factors:

+ The contamination (nature and intensity)

+ The structure/cleanability of the plant that is to be cleaned (materials, surface qualities, design).

The cleaning process can be assisted by using pigging systems or formulated cleaning agents.

Bühler has many years of experience in processes to provide liquids in industrial bakeries. Tried and tested all-in-one solutions, centralized production control adapted to the needs of bakeries, and plant components fabricated to Bühler’s usual high standards decisively support the industrial production of all types of baked goods. Bühler plants offer high product and production safety/reliability, process solutions precisely matched to the liquid, and thus also consistent, high-quality end products. +++

++ Aldi Italy and baked products

For a long time, fresh baked products played only a secondary role in Italian supermarkets. The daily walk to the baker or confectioner in the locality or village was too ingrained in consumers’ habits. That’s changing slowly but surely, quicker in the north than in the south. The German discounter Aldi Süd, which has now opened its first 16 markets in northern Italy, also displays a baking station with bread, rolls, baguettes, freshly-baked slices of pizza and focaccia, croissants and other pastries. The product range also includes sandwiches.

Products are sold by weight, as is usual in Italy. By the way, the competing discounter Lidl has already operated on the other side of the Alps for rather longer, and reached 8th position in the Italian retail landscape in 2017 with gross sales of EUR 4.3bn. and 579 branches in that country. At the head of the list is Coop Italia with revenues of EUR 12.8bn. and 1,205 branches. +++

++ Cetravac expands sales network

The use of vacuum conditioning in bakeries is currently the sector’s most important innovation. Adapting this technology to the needs of bakeries is due principally to the market leader Cetravac AG. Cetravac AG has now enlarged its marketing network early in 2018 through cooperation with Miwe GmbH in Arnstein, Franconia. In future, the latter’s team will now be available for advice, installation and customer service for Cetravac AG’s product portfolio. Cetravac AG already concluded a similar cooperation contract with the Austrian machine constructor König Maschinen GmbH in Graz a year ago. The two cooperation partners MIWE Michael Wenz GmbH and König Maschinen GmbH focus on the needs of medium-sized and large artisan businesses worldwide. At the same time, Cetravac AG’s team will use its specialist knowledge to give competent assistance to the cooperation partners, and will supply customized plant technology. Moreover, the entire industrial business will be concentrated at the Altstätten site. Cetravac itself is currently intensifying its own marketing activities through additional staff. Cetravac’s founder Adolf Cermak says: “Partnership with these two top firms brings us a market coverage that we would not have achieved so quickly through our own efforts. Our competence in turnkey business handled through our sister company bakeXperts AG is also increased to a very high level by pooling our strengths with these two partners.” +++