Fortification of Wheat Flour with Decorticated Pigeon Pea Flour and Protein Isolate for Bakery Products

Abstract

Australian wheat (Triticum aestivum) flour (Extraction rate 72%); for bread (BrdF) and biscuit (BisF) were used as a base mixed with decorticated pigeon pea (Cajanus cajan L.) flour (DPPF) and pigeon pea protein isolate (PPPI) for making fortified bread and biscuit. Ratios of DPPF used in wheat flour for making bread and biscuit were ranging between 5 to 25%, where as ratios of PPPI in wheat flour for making bread and biscuit were adjusted to protein levels of 15, 20 and 25 %. All blends were then examined for rheological and functional properties as well as proximate composition, apparent nutritive value of protein and organoleptic quality of the end products. The wet gluten of wheat flour was significantly (PX04;0.05) reduced with increase incorporation of DPPF (from 32.45 to 25.50%); (from 30.25 to 23.18%) and inclusion of PPPI (from 29.0 to 24.50%) and (from 29.2 to 22.5%) for BrdF and BisF, respectively. Increasing levels of DPPF resulted in a significant (PX04;0.05) increase in falling number from 614 to 663 sec and from 614 to 697 sec.; while PPPI significantly (PX04;0.05) decreased the falling number from 523 to 458 and 388 sec; also from 515 to 478 and 443 sec. for (15, 20 and 25% protein levels) for (BrdF) and (BisF), respectively. Water retention capacity (WRC) and bulk density (BD) were significantly (PX04;0.05) increased by addition of DPPF to wheat flour. Water absorption values range were 65.9 to 65.1% and 63.7 to 61.6 %; dough development time was 5.0 to 4.0 min and 4.4 to 4.0 min; dough stability was 4.0 to 2.4 min and 4.1 to 2.3 min for BrdF and BisF, respectively, compared to their respective control. On the other hand, addition of PPPI resulted in an increase in water absorption range of 66.3 to 74.8 and 66.7 to 71.0%; dough development time of 7.5 to 12.8 min and 4.5 to 7.3 min and dough stability of 2.6 to 8.6 min and 1.7 to 5.8 min for BrdF and BisF, respectively. The extensogram showed that the dough strength, extensibility and dough resistance to extension were decreased with increasing levels of DPPF and PPPI for the BrdF and BisF. The Fermentograms showed that the time taken to produce CO2 through the first and the second hours of fermentation were 45 and 40 min for BrdF dough; and for different blends of DPPF and PPPI ranged from 43 to 58 min and 35 to 55 min. On the other hand, values obtained for BisF dough were 52 and 43 min and for different blends range were 48 to 60 min and 36 to 50 min, respectively. Incorporation of DPPF in BrdF beyond 10% had a negative effect on loaf bread specific volume (3.20cc/g). However, incorporation of PPPI showed significant increase (PX04;0.05) and higher values of bread specific volume were 4.63, 4.72 and 3.897cc/g for (15, 20 and 25% protein levels), respectively, compared to wheat bread (control) (3.45 cc/g). Higher values of spread ratios of biscuit for 10 and 20% DPPF in the blends were 6.262 and 6.288, respectively, compared with wheat flour biscuit 5.849. Incorporation of PPPI in the blends showed no significant differences on the spread ratios of the biscuit. Bread supplemented with DPPF was found significantly (PX04;0.05) more acceptable in all quality attributes at 10% level of supplement, compared to the control bread. Addition of PPPI at 15% protein level in BrdF was found superior in all its sensory characteristics compared to the control bread. Significant differences (PX04;0.05) in color were observed in biscuit supplemented with PPPI at 25% protein level, and also in odor, after taste and overall quality for biscuit supplemented at 20% protein level. Bread supplemented with DPPF significantly increased (PX04;0.01) in ash, protein and caloric values with high levels of DPPF. Highest levels of DPPF (25%) resulted in the highest protein and calories (16.97% and 390.10 kcal/100 g, respectively) compared with 14.62% and 386.0 kcal/100 g for wheat bread. Inclusion of PPPI significantly increased (PX04;0.01) the protein content to 16.19, 21.16, and 25.86 % for protein levels 15, 20 and 25%, respectively and the caloric values reduced from 391.7 to 385.4 kcal/100 g for 15 and 20% protein level, respectively. Biscuit supplemented with DPPF and PPPI showed significant increase (PX04;0.05) in ash, protein with high levels of incorporation; while significant decrease (PX04;0.05) in carbohydrates and caloric value were found when biscuit wheat was supplemented with high level of PPPI. Levels of essential amino acids in supplemented products increased except for methionine and valine, with increasing levels of DPPF. The protein quality has improved and lysine chemical scores increased gradually from 50% for wheat bread to 71% when supplemented with high levels of DPPF and from 62 to 74 and 98% when supplemented with PPPI ( 15, 20 and 25% protein level), respectively. Incorporation of DPPF in wheat flour improved its protein quality and lysine chemical scores increased gradually from 35 for wheat biscuit to 60% for (25% DPPF) blend and from 58 to 62 and 85 in blends containing PPPI 15, 20 and 25% protein levels, respectively.