Effects of potato flour on dough properties and quality of potato-wheat-yogurt pie bread

Purpose Clarify the effects of potato flour (PF) addition on dough properties and quality characteristics of pie bread, thus providing a theoretical basis for potato-wheat-yogurt pie bread processing. Design/methodology/approach The seven pie bread formulations were prepared with addition of different amount of PF (0, 10, 20, 30, 40, 50 and 60 per cent) by replacing wheat flour (WF). The influence of replacement of PF with WF on the dough development, gas behavior, microstructural, gluten-starch interaction inside dough matrix and the nutritional and textural properties of pie bread was analyzed. Findings Compared to dough with WF, dough height was decreased significantly but total gas volume showed no significant difference with the addition of PF (10-60 per cent), and the dough height was decreased gradually with the increasing addition of PF (p = 0.0012). Scanning electron microscopy and confocal laser scanning microscopy showed that dough with 10-30 per cent PF revealed smooth surface and continuous network structure was also existed between starch and gluten, this was similar to the structure of wheat dough, while the surface was rough and the connection was not continuous when the PF addition was further increased from 40 to 60 per cent. Nuclear magnetic resonance showed dough with 10-60 per cent PF presented larger content of immobilized water compared to the wheat dough, and its content was also increased with the increasing addition of PF (p = 0.0008). Pie bread with 10-60 per cent PF exhibited lower fat, carbohydrate content and energy value compared to the wheat pie bread, and the fat, carbohydrate, energy was further decreased with the increasing addition of PF (p = 0.0012, 0.0002, 0.0007, respectively), while the dietary fiber content increased (p = 0.0011). In addition, specific volume and height/diameter ratio showed no significant difference in pie bread with 0-40 per cent PF, which were 2.1-2.4 cm(3)/g and 0.16-0.19, respectively (p = 0.004), whereas they were reduced significantly when the PF was increased to 60 per cent (p = 0.001, p = 0.002). In addition, the lightness (L) of pie bread decreased gradually with the increasing amount of PF, and the browning index was increased. Pie bread with 0-40 per cent PF showed similar hardness, springness and chewiness value, which were also increased when the PF was increased to 60 per cent (p = 0.001). The above results indicated that PF could improve the nutritional quality of pie bread, and the appropriate addition amount should be no more than 40 per cent. Originality/value PF was first used to produce yogurt pie bread to improve the nutritional properties of traditional WF yogurt pie bread.