The business said the number of bread products that are frozen directly after manufacturing - either as dough, part-baked or bread - is growing.
Freezing normally results in a decreased quality of the properties of the bread because it is harder and dryer and does not feel as fresh as freshly baked bread, suggested SP Food and Bioscience microbiology and process hygiene head Dr Elisabeth Borch.
SP Food and Bioscience, which is a unit of SP Technical Research Centre of Sweden (formerly known as SIK - The Swedish Institute for Food and Biotechnology), is a research center that bridges the gap between research and commercialization.
Bread baking from frozen dough
The project, ‘Bread baking from frozen dough’, which has now finished, started in 2011 and has been the subject of five masters projects and two publications in the journal of Cereal Science.
A third paper has now been published in LWT called Food Science & Technology, ‘Quality of bread baked from frozen dough – effects of rye and sugar content, kneading time and proofing profile’. It was co-authored by Camilla Öhgren and Nieves Fabregat of SP Food & Bioscience, and Maud Langton of Swedish University of Agricultural Sciences.
Dr Borch said doughs for two types of bread were prepared, rye bread and sweet bread, and frozen at a bakery for further processing and evaluations at SP Food and Bioscience and SLU, Uppsala.
Common industrial conditions
The doughs were prepared under common industrial conditions by mixing, kneading, resting and shaping. The formed buns were treated in three different ways before freezing; not proofed, half-proofed and fully proofed. (Proofing is the final rise of shaped bread dough before baking.)
The non-proofed doughs were thawed before full proofing and baked at 250°C for rye bread and 200°C for 12 minutes for sweet bread 60g buns; the half-proofed doughs were either thawed or only conditioned before baking; and the full-proofed doughs were either thawed or only conditioned before baking.
To study the combined effects of sugar content and kneading times for sweet bread, the researchers prepared dough with three different concentrations of sugar in a Reomixer and kneaded bread at three different times from between 2.5 and 10 minutes.
Laser scanning microscopy
The baked breads were evaluated for volume and texture, and bread slices photographed to visualize the shape of the baked buns. Doughs were studied with confocal laser scanning microscopy and three-dimensional micro-computed tomography.
- Breads baked from unproofed frozen dough that was allowed to proof after thawing showed the highest volume and the softest crumb structure.
- The pre-proofed sweet bread had firmer crumb and lower volume than the pre-proofed rye bread.
- Staling was significantly higher for bread that was stored frozen as fully-proofed dough.
The study on sugar content and kneading time showed more kneading is required when sugar content is raised. Microscopy data has revealed kneading gives a more homogenous gluten distribution.
Microscopy also showed frozen storage affects gluten distribution negatively.