###### Abstract  
The processing conditions for ready-to-proof (RTP) and ready-to-bake (RTB) frozen sweet bread doughs were optimized using response surface methodology. A central composite design determined four factors and the tested range for each factor: a first fermentation time of 15-45 min, a second fermentation time of 30-90 min, a freezing temperature of \(-45\)\(\sim\)\(-25\)\({}^{\circ}\)C, and a freezing time of 30-90 min. Sweet bread produced with these doughs was evaluated by bread weight, moisture content, crust color, height, volume, and firmness. Both the RTP and RTB doughs resulted in equal bread volume and height to the fresh dough, indicating excellent frozen stability. The first and second fermentation times were the significant processing factors for the RTP and RTB doughs influencing representative bread quality attributes based on quadratic models and ANOVA. Fermentation steps appeared to more significantly contribute to the quality of sweet bread made of frozen dough than freezing steps. The optimized RTP and RTB sweet bread dough processing conditions were the long first and second fermentation times for the dough based on a multiple response method and desirability. The optimum processing conditions for the RTP and RTB doughs were 44.7 min for the first fermentation time, 86.3 min for the second fermentation time, a \(-32.8\)\({}^{\circ}\)C freezing temperature, and an 85.5 min freezing time.  
f 2021 11 7904. [[https://doi.org/10.3390/app1117904](https://doi.org/10.3390/app1117904)]([https://doi.org/10.3390/app1117904](https://doi.org/10.3390/app1117904))  
10 August 2021 25 August 2021 27 August  
To improve the stability of frozen dough, numerous efforts have been made using supplementing ingredients, such as gums [10; 11; 12], emulsifiers [13], starch [14], vital wheat gluten [15], and vitamin C, and enzymes [16; 17]. Additionally, numerous studies on the effect of processing conditions of frozen dough on bread quality have been reported [18]. As processing factors related to frozen dough production, mixing time, fermentation temperature and time, freezing speed, freezing and thawing temperature, and thawing speed of dough have been considered [11; 19]. The freezing rate and temperature affect the quality of frozen croissant dough by influencing ice crystal formation and yeast viability in a frozen dough matrix [20]. The fermentation process also affects the quality of frozen dough through various complex biochemical reactions, which provide a distinctive bread flavor. Dough frozen after fermentation produces inferior quality bread than that produced by dough frozen before fermentation [21]. Studies on the processing conditions of frozen dough have mainly focused on bread or croissants, but those focusing on the briche type of sweet bread popularly consumed in Korea are scarce and are worth exploring. In addition, our previous study explored the formula optimization of RTP and RTB frozen sweet bread dough with major ingredients and identified sugar and water as the significant factors for all types of dough, leading to the enhanced frozen stability of RTP dough and the deteriorated stability of RTB dough [22].  
In the present study, a similar experimental approach as that in our formula optimization study was used to explore the effect of the primary processing conditions on the quality of sweet bread made from RTP and RTB dough, and the optimization of the processing conditions of each dough was evaluated using response surface methodology (RSM). The quality parameters that were analyzed for bread made from RTP and RTB dough were weight, moisture, top crust color, volume, height, and firmness, which were compared to those for bread made from fresh dough.