Proximate composition, sensory properties and microbiological status of granola substituted with soursop flour (Annona muricta) for household consumption

Abstract

This study was undertaken to investigate the proximate composition, sensory properties and microbiological status of granola substituted with soursop flour for household consumption. Matured soursop fruits were processed into flour. Granola was prepared from blends of wheat and soursop flours using 90:10, 80:20, 70:30, 60:40, 50:50 of wheat flour to soursop flour (SSF), and 100% wheat flour as control. Samples were subjected to sensory evaluation within 30 minutes of production. Proximate analysis was carried out using standard methods. The samples were also stored for 3 weeks and evaluated at weekly intervals for total bacterial and fungal counts. Proximate analysis revealed an increase in moisture (5.21 to 7.22%), ash (1.25 to 1.79%), protein (9.56 to 12.62%), crude fibre (0.83 to 1.21%) and energy contents (418.64 to 422.22kcal) with decrease in fat (14.13 to 12.09%) and carbohydrate contents (69.02 to 65.07%) as substitution of wheat flour with soursop flour increased. Sensory analysis showed that colour, taste, texture and overall acceptability of the control granola were more preferred. Colour of control granola and sample substituted with 20% SSF were significantly (p<0.05) similar. Similarly, texture and overall acceptability of control granola and samples substituted with 10, 20 and 30% SSF were significantly (p<0.05) similar suggesting that wheat flour can be substituted with soursop flour at levels up to 30% for the preparation of granola. During storage, total bacterial counts (TBCs) and fungal counts (TFCs) were observed to increase for all granola samples. TBCs and TFCs of granola samples after 3 weeks of storage ranged from 6.00×103 to 7.00×103cfu/g and 5.00×104 to 5.20×104cfu/g, respectively. The samples presented adequate microbiological conditions and were within recommended safe limit of microbial guidelines. The findings of this study therefore show that soursop can be utilized in the preparation of granola with improved nutritional value over wheat flour thereby reducing wastage associated with soursop fruits.