Upgrading the Flour Quality
09 July 201310 min reading
Gülsüm Yılmaz / Gıda Yüksek Mühendisi / Technical Manager / ABP Mühlenchemie Gıda San. ve Tic. A.Ş.
The flour quality is formed primarily depending on the quality of the wheat (aggregate) it is produced from, the quality of the used diagram and processing conditions. It is essential to analyze well the processed wheat firstly and make the process conditions suitable to these qualifications when necessary for flour production with processable quality. Even all of these conditions are provided; it is a fact that wheat quality is important for obtaining the desired quality in the flour. The problems occurred in the domestic wheat quality in the recent years have caused various quality issues in the flour. Many techniques have been developed in order to move the flour to the desired quality level together with the developments in technology, but additive using is still the mostly approved method. The view that every way can be used for producing flour with the processable quality is abandoned because of the reasons like the possible effects of some chemicals to human health, legal obligations and economic concerns. Thus today there is a gradually increasing demand for the advantageous products in accordance with specific health criteria and economic criteria.
Food Additives: Food additive substances that are not consumed as a food by themselves and not used as the characteristic component of the food whether with or without nutrition value are the substances added to the food during production, processing, preparing, packaging, carrying or storing stages in line with a technological purpose and as a result of this addition expected from itself or its byproducts to be the component of that food directly or indirectly.
The usage of each food additive in the world is determined as a result of scientific and medical studies conducted by a joint corporation led by The Food and Agriculture Organization (FAO) and World Health Organization (WHO) connected to the United Nations that Turkey is a full member of it. Formed jointly this organization’s name is Expert Committee on Food Additives. This joint committee JECFA (Joint Expert Committee on Food Additive) conducts studies on how much of these food additives can be consumed without giving any harm to the human health. This committee also decides which additive is used in which food. These determinations are made as a result of toxicological and carcinogenic researches of food additives.
Food additives are inspected by expert organizations within the union in European Union countries. The regulations about food additives in Turkey are conducted by basing on International Food Codex, FDA and European Codex.
The usage purpose of additives in flour industry is upgrading the characteristics of the flour by affecting the quality characteristics that affect negatively the processable features of the flour to the final product and via this way bringing the flour to the desired quality level.
During the processing of flour to the bread, kneaders can eliminate the quality fluctuations to some extent by changing the processing features of flour with the help of their experiences. However, today together with the increase in competition in the bread production sector, production of flour with a certain standard has started to have more importance in order to meet the consumer expectations. In this situation the biggest responsibility belongs to the flour producer and the standardization of the flour is provided by applying milling art and additives upgrading flour quality. Producing high amounts of flour continuously in the flour sector requires the usage of products with low dosages and good liquidity.
OXIDATION AND MATURATION OF FLOUR
Today wheat is processed as quickly as possible and it is not possible to wait for days in order to make flour matured by contacting with oxygen in the air. So the maturation process is accelerated with the help of oxidative substances. Oxidation firstly affects the sulfhydryl groups in the gluten and the connections between the different sections of gluten molecule or different gluten molecules strengthen the structure of the protein during the process.
Oxidation firstly affects the sulfhydryl groups in the gluten and enables the strengthening of the protein structure with the help of disulfide connections established between the gluten molecule’s different sections with long oxidation in sulfhydryl groups or different gluten molecules.
The most important additive used in strengthening the gluten in flour is ascorbic acid also called as vitamin C. actually ascorbic acid is not an oxidative substance, it is a reducing substance, but it transforms into the oxidative substance called as Dehydro L-Ascorbic Acid (DHL-AA) with the effect of the enzymes (L-Ascorbic Acid Oxidation) in the flour during kneading. While DHL-AA is reduced to L-AA again with the catalytic effect of Dehydro L-Ascorbic Acid Reductase enzyme in the flour, it helps some SH (sulfhydryl) groups to form S-S (disulfide) connections by being oxidized and plays an important role on the formation of gluten structure in the dough. During this process it makes ineffective the glutathione molecules that cause the flour weaken by breaking the disulfide bonds formed between gluten molecules. Thus in the kneading process, on one side disulfide connections are made and on the other side breaking of these connections is hindered and the desired structure of the dough is achieved by strengthening the gluten.
Pure ascorbic acid is dosed as 0,5-6 gr on average for 100 kg flour in the mills. This rate can be increased to 6-10 gr in very weak gluten flour or the lowering resistance applications like freezing the dough. According to the Turkish Food Codex Regulation on Food Additives; ascorbic acid should be added to the flour with an amount that is not higher than the one required providing the aimed purpose (Quantum Satis: Unspecified Amount).
Today ascorbic acid is mostly produced by subjecting the glucose to biochemical processes and put on the market in different particle sizes as powdered and crystallized. Vitamin C can be obtained from natural sources but it costs dozens of times more than the synthetic one.
Enzymes are biological catalyzers that accelerate the biological reactions in protein structure. Realizing the complex reactions caused the production of industrial enzymes. Microorganisms are one of these resources used for this reason. The enzymes obtained from microorganisms provide to produce many chemical substances in a very economic and fast way. These enzymes are used in many fields like medicine, textile and food in increasing amounts.
More qualified and reliable products produced by using enzymes increase the competitiveness of firms.
Enzymes have been used in every field of food sector for years. Contrary to many other food applications, in flour industry enzymes do not show their effects at the moment they are used, in other words they do not at the mill. In order to make enzymes added to flour react, it is required to switch to the next stage, in other words the baker should add water to the flour. Being customized according to the different effects and usage purpose, being able to be used in small amounts and being natural can be counted among the advantages of enzymes.
The basic enzyme preparations used in flour industry are amylases, hemicelluloses, glucose oxidases, lipases and proteases.
Alpha-amylase, beta-amylase and glucoamylase enzymes are the amylase varieties used in the flour industry at most. Just like most of the enzymes, amylases show their effect only on the substances dissolved in the water. Alpha-amylase cuts the unbranched sections of starch molecule into small pieces. These dextrins act as substrate for beta-amylase and glucoamylase. These enzymes form the sucrose like maltose and glucose that can be used by the ferment directly. As a result of the reaction, the liquidity of the dough increases, fermentation power and size rises, taste and color improve, the shelf life extends with protecting the softness of the crumb.
• Hemicellulose, pentosan, xylanase
Type 500 wheat flour includes approximately 2,5 % pentosan. Pentosan keeps ten times more than its weight. This is called as hemicellulose and consists of different sucrose like xylose, arabinose as well as glucose. An example of that is a pentosan formed of arabinose chains on xylose backbone. This formation is called as xylan or arabinoxylan and fragmentized by the xylanase, arabinoksilanase or the common name pentosanase enzymes. Nearly 1/3 of pentosan can be dissolved in the water and the rest cannot. While realizing the fragmentation of this structure, xylanase forms molecules that can dissolve in the water. This increases the water keeping and viscosity. During the process the more these molecules are fragmented the more water releases and viscosity decreases.
It is considered that pentosan has a net structure with gluten (Hoseney). As long as the pentosan rate increases, this structure tightens and thus decreases the final product size. The size can be increased significantly with the external addition of hemicellulose (an enzyme family including other enzymes that affect pentosan, xylanase and hemicellulose structure) that usually exists very little in the flour.
Especially xylanase has become one of the most important size gaining enzymes for bakery products recently. However this has different effects on arabinoxylan molecule. Different xylanases show different results like more dried or stickier dough surface, more or less water keeping, softer or harder dough, and finer or coarser pore structure.
Hemicellulose does not show much effect on FN (Falling Number) but shows an lowering resistance and increasing extensibility effect although it doesn’t have any effect on protein on Alveogram and extensogram curve. This softening effect is about loosening of pentosan-protein net structure, releasing water from pentosan gel structure and thus gluten hydration.
Most of these enzymes are obtained from Aspergillus type. Xylanase enzyme production is started to be produced from bacteria strains and to be used in flour sector.
• Glucose oxidase:
While transforming glucose in the dough into gluconic acid with the help of the oxygen in the air, this generally produced as fungal originated enzyme also provides hydrogen peroxide in the dough. As an oxidizing substance hydrogen peroxide takes place in many processes like transformation of ascorbic acid into DHAA, oxidation of glutathione and establishing disulfide connections in gluten (Note: most of the peroxide compounds are highly unstable and have flammable effect or accelerating effect on combustion. Thus usage of them directly in the flour sector is not suggested.)
Glucose + H2O + O2 Glucose Oxidase Gluconic Acid + H2O2
• Lipolytic enzymes
Enzymes like lipase, phospholipase and galactolipase are the ones whose usage is recommended in flour sector. These enzymes transform nonpolar triglycerides into mono and diglycerides and polar phospho and galactolipids into more hydrophilic (more water-soluble) lysoforms. In theory these formations show emulsifier effect but the low amount of the resulting substances usually is not enough to create this effect. However the lipids affected by the lipases are in the sections near to protein and thus are more effective than the emulsifiers added to flour externally.
These enzymes break the disulfide connections of gluten protein. Thus they cause firstly a softening and then fragmentation of the structure totally.
When a slight softening is desired in the short gluten structure, proteases can have the same function with cysteine. But the protease enzyme continues to function steadily as different from the cysteine whose effect is limited with the amount. As a result of this its effect increases together with the fermentation duration. So it is desired not to have any protease residues, even in trace amounts, in the enzyme preparations.
Proteases are used in the flour that is rich and strong in gluten with the purpose of relieving the gluten structure and facilitating the processability. As in our country usually there is no need for this type of upgrading the bread and special-purpose flour, this kind of usage is not used in the applications. Besides proteases are used effectively for providing the desired structure in the cracker, biscuit and wafer applications where gluten elasticity is not desired but the extensibility is a must.
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