Location: Grain Quality and Structure ResearchTitle: Rheology, microstructure and baking characteristics of frozen dough containing Rhizopus chinensis lipase and transglutaminase) Author
|Tilley, Michael - Mike|
Submitted to: Cereal Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/9/2011
Publication Date: 11/1/2011
Citation: Li, Z., Huang, W., Liu, J.G., Tilley, M. and Chung, O.K. 2011. Rheology, microstructure and baking characteristics of frozen dough containing Rhizopus chinensis lipase and transglutaminase. Cereal Chemistry. 88(6):596-601. Interpretive Summary: The frozen dough market has grown in recent years due to consumer demand for convenient, high-quality baked products. Frozen dough is thawed, proofed, and baked to serve to customers as oven-fresh bread and offers a number of advantages compared to the conventional method. However, a major shortcoming of frozen dough is that its bread-making quality deteriorates substantially as time in frozen storage increases. Additives such as enzymes are used in bakeries to facilitate processing, to compensate for variations in raw materials, to guarantee constant quality, to preserve freshness and food properties and to modify dough behavior during freezing. Transglutaminase (TG) catalyzes protein cross-linking may improve dough elasticity and crumb strength. Lipase generates glycerol that has been shown to increase freeze tolerance of yeast cells. Lipase made via conventional methods has been associated with very high production costs that it made it impractical to implement into the mainstream baking industry. Lipase from Rhizopus chinensis (RCL) could reduce production costs and make the use of lipase a possibility for the baking industry. The objectives of this study were to investigate the abilities of RCL and TG to improve frozen dough systems. Frozen storage had a negative effect on the viscoelastic properties of the doughs however TG increased the viscoelasticity of dough by protein cross-linking resulting in stronger and more resilient gluten than the control dough after 35 days of frozen storage. RCL and TG improved the water-holding capacity of dough during frozen storage thereby decreasing the amount of freezable water. RCL and TG could significantly increase available glycerol content of dough and sustain a high glycerol content after 35 days of freezing when followed by proofing. Bread from RCL and TG had a more open network and uniform crumb structure, which resulted in bigger specific volume. Sensory evaluation found that this combination also yielded a product with higher sensory scores for test breads.
Technical Abstract: The beneficial effects of a new recombinant lipase (Rhizopus chinensis lipase, RCL) and transglutaminase (TG) were investigated on frozen dough systems and their breadmaking quality. Rheological properties and microstructure of doughs were measured using a dynamic rheometer, rheofermentometer F3, and scanning electron microscopy. Measurements of viscoelastic properties showed that both G’ and G’’ of RCL- and TG-containing dough were greater than those of the control after 35 days of frozen storage. The SEM micrographs showed that dough containing RCL and TG had the most starch granules embedded in or attached to the gluten network, and the gluten seemed more powerful and resilient than the control dough after 35 days of frozen storage. Results of gas production and dough development tests indicated that RCL and TG improved the rheofermentative characteristics of frozen dough. RCL and TG could improve water-holding capacity and significantly increase the glycerol content of the control dough. Image analyses showed that bread crumbs containing RCL and TG had a more open network and uniform crumb structure, which resulted in bigger specific volume. This combination also yielded a product with higher sensory scores for test breads.