Sensory and rheological properties of reduced-fat rock buns and mango pie containing a papaya (carica papaya)-derived fat replacer

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Two perishable fruits Papaya (Carica papaya) and mango (Keit variety) which are locally abundant in Ghana were selected for this study. Freeze dried papaya was used as a fat replacer in two pastry products, namely rock buns and mango pies (with dried mango and mango puree as filler). The effect of fat reduction on the sensory and rheological properties of the rock buns and mango pies were determined. The dried fruits were also assessed for their physicochemical properties. Five rock buns treatments (full (100%)-fat, 25%, 50% and 75% reduced-fat and fat- free (0%) treatments) were produced as well as two pie crust treatments(full (100%)-fat and 25% reduced-fat treatments). Trained sensory panellists determined that the 25 % reduced-fat rock buns treatment was more similar in sensory attributes to the full-fat control, whilst the 50 % reduced-fat treatment was found to be satisfactory in comparison to the other reduced-fat treatments. With the exception of mouth feel in which differences between the full-fat control and the fat-free treatment were not significant (p > 0.05), there were significant differences (p ≤ 0.05) in sensory attributes between the control and the fat-free treatment for all other attributes. In the pie crust as well, sensory results showed that the reduced-fat treatment was not significantly different (p > 0.05) from the full-fat control for most attributes. Texture profile analysis of rock buns showed that hardness, springiness, cohesiveness, gumminess, chewiness and resilience increased with increasing fat reduction; however, values for fracturability and modulus of deformation decreased with increasing fat reduction. In the pie, texture analysis indicated that the reduced-fat treatment was not significantly different (p > 0.05) in hardness from the full-fat control; nevertheless, for fracturability, differences between them were found to be significant (p ≤ 0.05). Colorimetric measurements revealed that the 25 % reduced-fat treatment was more similar in appearance (colour) to the control than the other reduced-fat treatments which were dull in appearance. Notwithstanding the colorimetric results, sensory results also proved that the 50 % reduced-fat treatment was also not significantly different (p > 0.05) in colour from its full-fat complement. Dried fruits and puree produced from mango were more shelf stable than the unprocessed fruit. Analytical results indicated that the fat replacer contains 2.51 g/100 g and 12 % pectin and total nutrition fibre respectively. This is an indication that the pawpaw-derived fat replacer could be a viable additive for fat replacement.
A thesis submitted to the Board Of Postgraduate Studies, Kwame Nkrumah University of Science and Technology in partial fulfilment of The requirements for the award of the Master of Science (Msc) Degree in Food Science and Technology.