Optimize textural characteristics, shelf life of bread.

Bread makers benefit from techniques that increase the shelf life of bread by slowing the staling process. The effects of baking protocols and various formulations on staling must be characterized in order to determine and control certain critical parameters and processes, which will, in turn, improve the textural shelf life of bread.

Ohio State University scientists and colleagues wanted to determine how the increased crumb density of white pan bread would affect the bread's rate of staling. Researchers studied the effects of using glycerol, protease, amylase enzymes and a modified baking process. They developed a technique that restricted the rise of the bread, while at the same time increasing the crumb density.

Loaves of both a high-density and control bread were vacuum-packaged and held for 10 weeks in an incubator at 23 C. The densities of the control bread crumb and high-density bread crumb were 0.29 to 0.34 and 0.36 to 0.41 g per cm3, respectively. The researchers monitored the effects of the formulation and baking protocol on starch crystallization and the texture of the bread using differential scanning calorimetry (DSC) and texture analysis.

DSC was also used to monitor melting endotherms of recrystallized starch. In addition, compression studies helped to quantify the elastic modulus at various intervals up to 10 weeks. Water activity for the breads with and without glycerol was 0.83 to 0.88 and 0.90, respectively. DSC analysis showed three irreversible endotherms that occurred at approximately 66 C, 99 C and 138 C. The appearance of endotherms at 99 C and 138 C was interpreted as the melting of amylose-lipid complex and uncooked starch, respectively. Investigators believed the 66 C endotherm to be the melting of amylopectin that had recrystallized and increased when the product was stored.

Bread firmness was evaluated in terms of elastic modulus, which increased with crumb density without any apparent relation to starch crystallization. The modified baking process that was used to create higher-density bread may have decreased the extent of crystal formation and the firmness of the crumb, thereby improving the textural characteristics and shelf life of the bread.

Further information. Gonul Kaletunc, Department of Food, Agricultural and Biological Engineering, The Ohio State University, 210 Agricultural Engineering Building, 590 Woody Hayes Dr., Columbus, OH 43210; phone: [phone]; fax: [phone]; email: [e-mail].