Effects of hydrocolloids on pasting behavior and gelling properties of banana flour and its application in bread

Abstract

Bananas have a high potential in becoming a future staple crop due to its rapid growth rate, short harvest time, and high starch content. However, banana flour is highly retrograded which is its major limitation. The objective of this study was to study the effects of selected hydrocolloids on the pasting and gelling properties as related to the gelatinization and retrogradation of banana flour as well as its application in bread as a wheat flour substitute. Xanthan gum (XG), gum arabic (GA), hydroxypropyl methylcellulose (HPMC), and guar gum (GG) were added to banana flour at different concentrations (0.5, 1.0, and 1.5%). Regarding the pasting behavior, XG and GA decreased the peak viscosity with increasing concentration while HPMC and GG increased the peak viscosity with increasing concentration. All of the hydrocolloids reduced the setback viscosity except for GG which increased it. There were slight increases in pasting temperature but this was not significantly different except for XG at 1.5% and GG at 1.0%. In terms of gelatinization, although all of the hydrocolloids showed no effect on the gelatinization temperature, it did increase the gelatinization enthalpy (DHG). Concerning retrogradation, the addition of hydrocolloids did not significantly affect the retrogradation enthalpy (DHR). As for the gel firmness, hydrocolloids did not show a significant effect on firmness of the freshly prepared gels. However, after being stored at 4°C for 7, 10, and 14 days, XG at 0.5%, GA at 1.5%, HPMC at 0.5%, and GG at 1.0% resulted in a significant reduction in gel firmness. Other concentrations may cause an increase in firmness or have no effect at all. In summary, different types of hydrocolloids at different concentrations affected the pasting and gelling properties of banana flour in a different way. From the results mentioned above, the optimum concentration of each hydrocolloid (XG at 0.5%, GA at 1.5%, HPMC at 0.5% and GG at 1.0%) was selected to add to white pan breads with 30% banana flour substitution to investigate the quality of freshly prepared breads (Day 0) and breads stored at room temperature for 7, 10 and 14 days. Moisture content of the bread was found to decrease as the storage time increased. HPMC-added breads showed significantly higher moisture content than the control during the beginning of the storage time. As for the water activity, addition of hydrocolloids did not affect water activity of the bread samples. In terms of specific loaf volume, HPMC-added breads resulted in the lowest specific loaf volume for all storage days. However, there were no significant differences observed in the crumb structure. For the crumb texture, freshly prepared GA-added breads resulted in lower hardness than the control. An increase in crumb hardness was observed in all samples during storage. All the breads showed no obvious difference in terms of color.