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Supercritical fluid extrusion shortens bread production time.

Bread-making relies mainly on yeast and carbon dioxide production for leavening purposes. A sponge-and-dough process with a production capacity of 150 loaves per minute averages seven hours from the start of mixing to the production of the first loaf. It would facilitate matters if we could reduce production time and improve dough consistency, while maintaining product quality.

Research has shown that supercritical fluid extraction is a feasible process for leavening dough. Scientists at Cornell University have adopted, improved and extended the process to bread-making. They wanted to show that bread-making based on supercritical fluid extraction economically produces rolls that are comparable to commercially available samples. They found that up to an 80% savings in equipment investment, a 78% reduction in process time and an 86% decrease in processing space may be realized by using supercritical technology. Furthermore, supercritical carbon dioxide injection can create a variety of bread types, thus increasing flexibility in a production line.

The investigators extruded a bread formulation with 1.5% wt supercritical carbon dioxide (SC-[CO..sub.2]) under 9 MPa through a twin-screw, co-rotating extruder operating at 120 rpm. The specific mechanical energy they used was260 kJ per Kg. The supercritical dough was maintained at 33 C to 35 C when [CO..sub.2] was injected into it in order to maximize solubilization. Commercial refrigerated doughs were characterized and baked, and then were compared to supercritically processed dough and bread.

The investigators evaluated the economics of the process. Baking the product at 180 C for 30 min yielded bread with density of 0.33g per mL and a bake-off loss of 11%. The dough, bread moisture and density of samples produced using supercritical extraction and by the sponge-and-dough processes were not statistically different, at a 95% confidence level.

Researchers evaluated the cell morphology of the dough and bread using scanning electron microscopy and found them to be similar to commercial products. The supercritical process improves control over production and optimizes consistency. The technology reduces the need for dough handling and rework, and it minimizes operator dependency.

Further information. Syed Rizvi, Department of Food Science, Cornell University, 114 Stocking Hall, Ithaca, NY 14853; phone: 607-255-7913; fax: 607-254-4868; email:
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Publication:Emerging Food R&D Report
Date:Mar 1, 2006
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