Study of baking conditions on par-baked bread properties.

摘要

The effects of par-baking conditions (three different temperatures 149, 182, and 215°C (300 360 and 420°F) with different baking times 12, 18, and 24 min) on baked bread external and internal properties were studied. Par-baked loaves were made by the straight dough method. After the first bake stage, breads were stored at 23 ± 2°C for 4 days or 7 days and then were baked-off at 215°C for 10 min. Bread first baked at the lowest temperature at 149°C had a higher oven spring during the second baking, but the loaf would shrink after cooling, resulting in lower loaf volume. Par-baked bread volume was determined by the 1st bake. Another 10% shrinkage in volume occurred during storage and the second bake. Baking loss increased as the baking time and baking temperature increased. This resulted in different moisture contents in the par-baked bread, which affected bread staling rate.; Milder baking conditions posed a risk for bread sidewall collapse after removing the par-baked bread from the oven. Ungelatinized starch in the bread center and crust might be factors that contribute to sidewall collapse. A schematic model for bread sidewall collapse was developed. There are two factors that determine sidewall collapse, one is sidewall rigidity and the other is an internal contraction force. Sidewall rigidity might be relative to crust starch gelatinization; internal contraction forces might result from the contraction of gluten protein or the lack of a starch filler to fill in the spaces in the air cell walls. Oxidizing agents did not improve the par-baked bread structure, but made it worse. Reducing agents, heat induced coagulating protein, and emulsifiers were effective ingredients for improving structure.; Freshness recovery temperature for staled bread was approximately 55°C. Freshness recovery was better for bread initially baked under milder baking conditions. Bread baked at higher temperatures and longer times had higher staling rates. After the 2nd bake, bread staled more than twice as fast as after the 1st bake. Emulsifiers had a better effect on retarding the staling of par-baked bread than did enzyme softeners.