112 Effect of processing conditions and composition of microencapsulated high fat powders on Dough rheology and the baking properties of wheat bread.

C. M. O’BRIEN (2), H. Grau (1,2), D. P. Neville (3), M. K. Keogh (3), and E. K. Arendt (2). (1) National Food Biotechnology Centre, University College, Cork; (2) Department of Food Science and Technology, University College Cork, National University of Ireland; (3) Dairy Products Research Centre, Moorepark, Fermoy, Co. Cork.

Microencapsulated high fat powders can be added to cereal based products as an alternative to block fat. The microencapsulation process involved the dispersion of the fat by homogenisation (4–35 MPa) and fixing of the globules by spray drying. The encapsulating agents used were WPC-75 and WPI at concentrations of 5–20% (w/w of powder). The free fat levels in the powders were also measured to determine the effects of free fat on powder performance. Differential scanning calorimetry (DSC) was carried out on each of the powders to assess their melting characteristics. The baking characteristics of the powders in wheat bread were compared to a standard bread and bread containing a commercial fat. Specific volume and texture profile analysis (TPA) values were measured for all breads The rheological properties of doughs were characterised using a controlled stress rheometer by measuring the complex modulus (G*) and the phase angle (delta) at a range of frequencies. The homogenisation pressure used in powder manufacture and the protein level in the powders were found to affect free fat levels. Similar values for specific volume were found for all batches except the standard which had values 25% lower. The hardness values from TPA varied significantly between the batches. Two of the powders tested had hardness values similar to the loaves containing commercial fat. The complex modulus varied between the dough samples tested. Two of the doughs with milk powders performed similarly to the dough containing commercial fat, while others had higher values for complex modulus. Differences in Phase angle (delta) were only significant at higher frequencies. This study shows that both processing conditions and powder composition had significant effects on powder properties. These differences in properties affected the dough rheology and baking properties of wheat bread.