Elucidation of refrigerated dough syruping mechanism and improvement of frozen dough bread quality by enzyme treatments : Elucidation of refrigerated dough syruping mechanism and improvement of frozen dough bread quality by enzyme treatments
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Refrigerated and frozen dough industry is fast growing due to the convenience and to the freshness during storage, and thus various types are consumed to save time and cost. However, one of the problems encountered with refrigerated dough is the formation of brownish liquid, so-called 'dough syrup' that migrates to the surface of the dough during the storage and causes a quality loss. Frozen dough also has several baking problems such as poor bread volume and lower texture properties that have been ascribed to dough weakening and reduced yeast viability. The objectives of this study were to elucidate the mechanism of refrigerated dough syuping via endoxylanase in wheat flours and to search for a way to prevent the syrup formation. For doing so, the effects of α-amylase (Aamyl) and endo-xylanase (Exyl) treatment on the bread quality of frozen dough were studied and compared with fresh dough. Doughs were made of strong, weak, and Korean cultivar (jopoommil) wheat flours and stored at 5C for 35 days, respectively. Dough syrup increased up to 6.5, 6.9, and 17.2% in weak, strong, and jopoommil flour, respectively, after 35 days of storage. Significant changes in molecular size distribution of water soluble arabinoxylan (WS-AX) were observed from all 3 types of flours by HPSEC. Especially, the relative proportion of low molecular weight fraction (1.8-49.1 kDa) drastically increased from 25.1 to 68.3% in jopoommil. The addition of carboxyemethylcellulose, β-glucan and xylan effectively reduced the syrup formation in jopoommil dough by 32, 47 and 50%, respectively, compared to the untreated dough after 35 days of refrigeration. The effect of combination of enzymes on bread quality was determined by texture, volume and color measurement. Aamyl increased specific volume and improved crumb firmness. Exyl was ineffective on specific volume but, improved crumb firmness. So, A positive synergist effect on crumb firmness was observed by the combined use of Aamy and Exyl. These results suggested that the structural changes of WS-AX induced by Exyl hydrolysis would have a significant influence on the syrup formation. The polysaccharides could be utilized in commercial dough formulations to decrease the syrup during refrigerating storage.