The Effect of Fermentation, Spent Coffee Grounds and Juices of Lemon Fruits and Rosemary Leaves on Quality of Whole Wheat Bread

Abstract

Whole wheat bread is increasingly consumed in Rwanda. Bread wheat is among the top priority crops that Rwanda has promoted to boost the national economy. However, bread made from locally produced wheat varieties has been claimed to be of low acceptance. The objective of this study was to evaluate the effect of fermentation, spent coffee grounds and juices of lemon fruits and roemary leaves on quality of whole wheat bread. Whole Wheat flour (W) from wheat varieties (Gihundo, Kibatsi, Nyaruka and Reberaho) grown in Musanze, Kinigi, Rwanda, spent coffee grounds (SCG), juice from lemon fruit (L), juice from rosemary leaves (R) and fermentation duration were assessed for their effect on the physical and sensory characteristics, proximate composition, acrylamide content and microbial contamination of bread during 7 days of storage at room temperature (17-23oC). The mixture of whole wheat flour from the four wheat varieties, spent coffee grounds, juice from lemon fruit, juice from rosemary leaves, salt and water were fermented. Instant dry yeast was used as a raising agent at 34oC, 60% relative humidity for 60 min and 39oC, 85% relative humidity for 120 min. The dough was baked at 180oC for 20 min. Whole wheat flour from Gihundo variety had the highest values of ash content (1.47 %), total dietary fiber (15.97 %), water absorption capacity (89.00 %), dough development time (7.62 min) and brightness (84.67 %). Whole wheat flour from Nyaruka variety showed the lowest values of water absorption capacity (80.00 %), dough development time (6.33 min) and brightness (80.33). While whole wheat flour from Reberaho variety exhibited the lowest values of ash content (0.98 %) and total dietary fiber (12.44 %). There was no significant difference (p > 0.05) in protein content (10.00 % and 10.85 %) among whole wheat flours from the four wheat varieties. Whole flour from Gihundo wheat variety exhibited high values for most of the physicochemical characteristics determined in comparison to the other three varieties. Thus, the wheat flours from all the varieties could possibly be categorized as all-purpose since their protein contents were between 9% and 12%. It is important to select grains or flour from the wheat varieties based on the individual cultivar because their derivative products could have a more desired quality. The control breads (W breads) were made from whole wheat flour dough fermented for 60 min without incorporation of SCG and LR. The control bread samples were firmer than the breads xiii containing SCG and SCG+LR with the same time of fermentation. The long fermentation (120 min) and the inclusion of spent coffee grounds, and spent coffee grounds + juices of lemon fruits and rosemary leaves in doughs, caused the supplemented breads to have lower L*, a* and b* values than control breads. Low L*, a* and b* values indicate minimum darkness, redness and yellowness of bread. Aroma, taste and appearance of spent coffee grounds+juices of lemon fruit and rosemary leaves breads from doughs fermented for 120 min were the most liked. All whole wheat breads supplemented with spent coffee grounds, and spent coffee grounds + juices of lemon fruits and rosemary leaves, satisfied consumers’ preferences. Whole wheat breads supplemented with spent coffee grounds, and spent coffee grounds+juices of lemon fruit and rosemary leaves were low in protein, fat and ash contents and higher in dietary fiber than control breads. Control breads from Gihundo variety had the highest acrylamide content (47.00 μg/kg). Addition of spent coffee grounds + juices of lemon fruit and rosemary leaves in dough fermented for 60 min reduced significantly (p≤0.05) the acrylamide formation in control breads from 47.00 μgkg-1 to 10.50 μg kg-1. Total viable counts (TVC) and total molds and yeasts (TMY) significantly (p≤0.05) increased with the storage time of 7 days. Whole wheat bread with added spent coffee grounds + juices of lemon fruit and rosemary leaves (dough fermented for 60 min) from Nyaruka variety and whole wheat bread containing spent coffee grounds (dough fermented for 120 min) from Gihundo variety had the lowest and the highest TVC, respectively, on 7th day of storage. While whole wheat bread supplemenred with spent coffee grounds + juices of lemon fruit and rosemary leaves (dough fermented for 60 min) from Kibatsi variety and whole wheat bread containing spent coffee grounds (dough fermented for 120 min fermentation) from Reberaho wheat variety showed the lowest and highest TMY, respectively, on 7th day of storage. All whole wheat breads from dough fermented for 120 min had lower TVC than those from dough fermented for 60 min, whereas it was the opposite for TMY. TVC for all breads up to 5th and on 7th day of storage was within the satisfactory and borderline ranges which are <4 log cfu g-1, and between 4 log cfu g-1 and 6 log cfu g-1, respectively. On the 7th day, whole wheat bread supplimented with spent coffee grounds + juices of lemon fruit and rosemary leaves followed by whole wheat bread containing spent coffee grounds, showed lower TVC than control breads. The application of spent coffee grounds and juices of lemon fruit and rosemary leaves as generally recognized as safe natural ingredients can be exploited by bakeries to improve the sensory attributes and shelf stability of whole wheat bread.