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RESEARCH
Activities of exogenous enzymes in baked products The activities of various exogenous enzymes in baked products were systematically analyzed from dough preparation, through the baking process and into storage. The texture analysis methods that were developed allowed the events occurring during the development of firmness in the wheat crumb to be differentiated into processes taking place before or after baking. The presence of the enzyme preparations examined during the project showed no detectable functional effects during storage in the crumb that was already formed, due to either previous inactivation or a lack of functionality in the end product. By Thekla Alpers, Sabina Paulik, Thomas Becker, Mario Jekle, Katrin Reichenberger, Sabine Lutz-Wahl, Lutz Fischer, Gerold Rebholz,
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Katharina A. Scherf
Endogenous enzymes occur naturally in wheat flour and yeast, and added exogenous enzymes are responsible for changes in the constituents of wheat during the manufacture of baked goods. The activities of the endogenous enzymes in cereal flours vary depending on the wheat species and variety, environmental influences in the field, and the state of ripeness at harvest time. Exogenous enzymes are used in the manufacture of baked goods to balance out these differences, improve the properties of the dough and end products, and guarantee that the baked goods have a reproducible high quality. The enzymes used for this purpose come mainly from the oxidoreductase class (EC 1), e.g. glucose- or hexoseoxidases, and the hydrolase class (EC 3) such as amylases, xylanases and lipases [1].
The legal basis for using enzymes in foodstuffs In the EU, adding enzymes to foods is permissible only if they conform to the current implementation status of Regulation (EC) No. 1332/2008. The conditions required for approval are their health safety for consumers, the technological necessity for their use, and the exclusion of consumer deception. According to Regulation (EC) No. 1332/2008, enzymes must be declared in the list of ingredients, with their class name and specific designation, if they are added to foodstuffs for technological purposes in their manufacture, processing, preparation, treatment, packing, transport or storage, and display a technological effect in the end-product. Insofar as enzymes are inactivated during processing and have no technological effect on the end product, they are exempt from the obligation to declare. In the case of baked goods, it is usually assumed that the added enzymes are inactivated as a result of heating during baking, and therefore need not be declared due to the absence of a technological effect in the end product.
Properties and technological effect of amylases α-Amylases (EC 3.2.1.1) belong to the endo-amylases that split α-(1,4)-glycosidic bonds in starch, and release lower molecular weight α-dextrins. In contrast, maltogenic amylases (EC 3.2.1.133) and malto-oligosaccharide-liberating amylases (e.g. EC 3.2.1.60 and EC 3.2.1.98) are exo-amylases that release maltose and other malto-oligosaccharides such as maltotetraoses or maltohexoses from starch. Pullulanases (EC 3.2.1.41) and iso-amylases (EC 3.2.1.68), which cleave α-(1,6)-glycosidic bonds and thus remove the side-chains of the amylopectin, are also relevant. β-Amylase (EC 3.2.1.2), on the other hand, hydrolyses the α-(1,4)-glycosidic bonds of the non-reducing ends of starch polymers, thus forming β-maltose and β-limit dextrins as the main products. Figure 1: Effect of various additives to the extraction buffer to determine a residual activity of the maltogenic amylase from G. stearothermophilus from yeast-leavened white bread using different additions to the extraction buffer (1: no addition, 2: with 1 M of maltose, 3: with 20% (w/v) of maltodextrin, 4-8: with 10% (w/v) of maltodextrin and various extraction times; 1-4: 1-hour incubation time; 5-8: 2-, 3-, 4- and 5-hour extraction time)
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The effect of amylases during the production of baked goods depends on their thermal stability and specificity, and on the products that are formed. In general, fungal amylases have low thermal stability, and their activity is lost after starch gelatinization during the baking process. On the other hand, a few bacterial amylases are stable
