Sandwich loaf production requires high-protein wheat flour. But since mills in Zimbabwe constantly contend with shortages of strong imported wheat, a promising alternative is mixing imported with homegrown wheat or even gluten-free maize or cassava flour. The poorer baking properties of these flours can be compensated for with special enzyme systems.

The most common staple food in Zimbabwe is sadza — a nutritious maize porridge served with almost every hot meal. But bread plays an important role in the diet, too. Best of all, consumers like fluffy-soft slices of wheat bread, which they enjoy as toast for breakfast and as a succulent filled sandwich for lunch.

However, the availability of sandwich loaves cannot be taken for granted in Zimbabwe. Since the country’s own farms are far from being able to cover the total demand for wheat, and because the local varieties do not have optimum baking properties for the production of pan bread with high baking volume, wheat with high protein quality has to be imported. Because of the permanent recession, however, the country is repeatedly faced with foreign exchange shortages that interfere with imports and push up the price of food. The crisis reached its peak in the autumn of 2019, when Zimbabwe introduced a new currency and bread prices suddenly tripled.

“Bread has become a luxury article,” daily newspapers proclaimed.

Raw material procurement challenges

For the milling industry, the volatile situation with the procurement of raw materials poses a major challenge. In many other African states besides Zimbabwe, mills are looking for new strategies and concepts to make themselves less dependent on fluctuating prices, qualities and availability.

One cost-saving option is to mix high-protein lots with cheaper batches or local wheat varieties. In the production of sandwich loaves, though, this practice can result in loss of quality. Among other things, weaker flour mixtures impair fermentation stability, the appearance and texture of the crumb and the size of the baked product.

On the other hand, consumers’ expectations concerning their favorite bread are clearly defined: the loaves must have a high volume, a fine, even texture and a soft, fluffy crumb.

Individualized flour treatment

When the proportion of quality wheat in the grist is reduced, fine-tuning of the flour with enzymes such as amylases, hemicellulases, lipases or glucose oxidases is essential in order to maintain the expected quality standard.

The Mühlenchemie toolbox holds innovative solutions that make it possible to use weaker flours and nevertheless meet the sophisticated demands of sandwich loaf production.

The lower gluten and protein levels can be compensated for with the hemicellulase Alphamalt HC and the lipase EFX Swift, for example. The specific enzymes and quantities to be used in a particular case will depend on individual requirements, indicated by the results of rheological analyses and laboratory-scale baking trials. The Enzyme Designers draw up a separate master plan for each flour. Whereas the finely adjusted enzyme system of Alphamalt HC 13045, for instance, results in high volume yields and extremely extensible doughs, the lipolytic esterases of EFX Swift have the effect of stabilizing the gas retention and improving the stability of the dough and hence increasing the volume and the texture.

Alphamalt Gloxy is a tried-and-tested quality booster for “on top” treatment of flour for sandwich loaves. This glucose oxidase has a strengthening and stabilizing effect on the gluten strands and is beneficial for the overall baking process. The doughs have a drier, silkier surface and are easier to work either by hand or mechanically. Moreover, they have much better fermentation stability and are less sensitive to long proof times and mechanical stress.

Reducing raw material costs

Economic considerations are prompting the African milling industry to turn its attention to composite flour, in addition to the possibility of adding locally grown wheat or imported, low-cost and therefore often low-protein wheat. Flours from starchy tubers like cassava, yams or sweet potatoes are being considered as well as non-bread cereal flours from, for example, corn, rice and millet.

Zimbabwe has a long tradition of growing and processing maize, so the use of maize flour is the obvious choice. For mills with flexible plant systems that are able to grind maize as well as wheat grains, the production of maize flours is an interesting niche application. On one hand, this option gives the mills greater scope for using different grain varieties, but on the other, it widens their profit margin, since domestic maize is usually cheaper than imported wheat from the United States, Canada or Europe.

However, from the point of view of baking, a large proportion of maize flour has a negative effect on the processability of the doughs and the quality of the baked products. The lack of the gluten component in the protein diminishes the water absorption and fermentation stability of the dough and results in sandwich loaves with a denser crumb structure and a lower volume. The color, taste and shelf life of the bread are different, too.

To prevent such losses of quality, millers need a sure instinct in determining the right ratio when mixing bread and non-bread flours. Moreover, it is essential to compensate for the poorer baking properties with suitable enzymes and flour treatment agents.

Boosting baking performance

At the Mühlenchemie Technology Centre, the company’s raw material experts have carried out comprehensive application trials with composite flours. Their main objective was to produce flours for sandwich loaves that differed very little in respect of processing properties and bread appearance from products made solely from wheat. Products from the Powerzym range proved to be the optimal choice.

With modifications geared specifically to the particular composite flour, the experts devised highly functional solutions for the production of loaves with those flours. It became possible to improve important quality parameters such as volume, water binding capacity, machinability, oven rise and crumb elasticity so significantly that 10% of maize flour, for example, could be used without causing problems.

Powerzym also showed itself to be highly effective in trials with cassava. In this case, up to 30% of the wheat flour could be replaced with the high-starch alternative flour.

Problems and solutions

In many emerging and developing countries, the partial use of non-bread flours or domestic wheat varieties may be a promising way toward more independence in the supply of raw materials.

Whether such milling strategies lead to success or failure is not just a matter for the mills alone, it also depends on those who work with the flours on the spot. Since novel flour mixtures may often result in differences in processing properties and fluctuations in product quality at bakeries, Mühlenchemie’s technologists are ready to help and advise the baking industry, too.

The main problems in the production of sandwich loaves are the unsatisfactory formation of the crumb structure and the shape of the loaf. In some cases, a specific analysis of all process parameters is necessary to find the source of the faults. Nevertheless, it is possible to give some basic recommendations that may help to avoid such product defects. The following is an overview of the most common weaknesses in the production of sandwich loaves:

Problem: Large pores and uneven texture of the crumb.

Solution: More intensive kneading and longer proofing; adjust the fat content of the recipe. Add emulsifiers (e.g. Mulgaprime SSL / Mulgaprime 90) and enzymes (e.g. Alphamalt EFX Mega).

Problem: Collapse of the side walls of the loaves.

Solution: Change the mixing/kneading time; reduce the proof time; reduce amylases; increase the ascorbic acid content (e.g. ELCO C-100 K); improve the structure of the dough with EMCEgluten Enhancer. Shape the dough by the four pieces or twist method.

Problem: Rapid staling, inadequate shelf life.

Solution: Optimize pasting of the starch; improve water binding in the dough. Increase the amylase activity (e.g. with Alphamalt A 15140). Prolong the softness and elasticity of the crumb with maltogenic amylases (e.g. Alphamalt Fresh).

Problem: Sticky dough.

Solution: Adjust water addition, add improver that increase the water retention and reduce the dough stickiness (e.g. EMCEbest WA).

Problem/challenge: A wish for general quality improvement in respect of volume, browning, machinability, texture and shelf life.

Solution: Treat the flour with “all-in” improvers from the Powerzym range (e.g. Powerzym 29066).

Sven Mattutat is a product manager with Mühlenchemie. He may be contacted at