Effects of cissus (Cissus populnea) gum on dough rheology and quality of wheat-cassava composite bread.

摘要

Cissus gum was extracted from the stem of Cissus populnea plant using two methods designated as A and B. The specific gravity, pH, total solid, total soluble solid, refractive index and viscosity of the gums were evaluated and used as an additive in wheat-cassava bread (90:10). Specific gravity of the gums ranged from 0.988 to 1.003, and pH from 5.50 to 5.55, values for total solid (%) were 0.8-0.95 and total soluble solid (Brix) ranged from 0.1 to 0.2. Refractive indices of the gums were 1.3324 for both extracts, while the viscosity in Pa.s was 0.394 for gum A and 0.460 for gum B. Gum A and B were used in the baking process and for the alveograph studies. Alveograph studies of bread doughs gave work done (W) from 237x10-4 to 382x10-4 J, while the extensibility ratios of the doughs ranged from 0.8 to 1.2. Work done and extensibility ratio of composite flour doughs were highest in cissus gum A dough as the starch and other ingredients were more cohesive. The addition of cissus gum A increased the loaf volume of the composite bread from 763 to 1043 cm-4 (36.6%) with cissus gum B increasing it by 35.8%, i.e. from 763 to 1036.7 cm-3. Specific volume of bread loaves with cissus gum A increased by 39.2% (from 2.8 to 3.9 cm-3/g). Sensory evaluation of bread loaves showed a significant difference (P<=0.05) between 100% wheat bread and the composite loaves with or without gum for all attributes, the control bread was the most acceptable with a mean score of 7.7 for general acceptability. The composite loaves did not differ significantly in general acceptability with an average score of 6.4. Addition of cissus gum did not affect values for proximate composition.