Image analysis and surface response methodology as tools to evaluate the effect of enzymes on dough and bread quality

Crumb characteristics are one of the factors used to evaluate bread quality. For a long time, this factor has been analyzed by baker's experience and when possible textural equipment has been used. However the basis of baker's evaluation has been subjective, qualitative and imprecise by nature. Visual evaluation of bread loaves is based on cell wall thickness, cell size, uniformity of cell size, cell shape and crumb color, and these parameters will vary depending on flour quality, ingredients, additives or process conditions. Digital image analysis offers a potential solution and its use is increasing. The objective of this work was to evaluate the effect of an enzymatic blend, added to wheat flour at different proportions, on farinographic and extensigraphic dough characteristics and also on bread quality. Image analysis was used to measure crumb characteristics and all data were evaluated by surface response methodology. A two level factorial experimental design (3FI) with 4 central point repetitions was used. Enzymes used, based on 100 g of flour, were glucose-oxidase (GOX), xylanase (XYL) and peroxidase (POX). Results showed that enzymes behaved in a different way depending on their concentration in the formula. POX and XYL increased water absorption, while GOX did not affect this parameter. When they were mixed, water absorption value decreased, independently of enzyme concentration. Maximum consistency time showed a similar behavior, increasing the response when enzymes were added alone and decreasing when they were added together. Statistical analysis showed that data could be fitted to a quadratic model (r²=0.9993). Dough stability was mainly affected by GOX and XYL with a probability value (p) greater than 0.95, while POX did not affect this parameter. Extensigraphic properties depended on the kind of enzymes and if they were added alone or blended. When they were added alone elasticity increased, while if they were added together elasticity decreased. Enzymes did not have significant effects during resting. Extensibility was affected mainly by GOX and resting time. Product density was not affected (p = 0.6933), while crumb changed with the kind of enzyme used, getting more uniform crumb with XYL. Enzymes modified dough and bread characteristics, having larger effects when enzymes were not combined. Major effects were seen during mixing.