Grapefruit peel powder as a functional ingredient in cake production: Effect on the physicochemical properties, antioxidant activity and sensory acceptability of cakes during storage

In this study, effects of grapefruit peel powder (GFPP) inclusion (2.5, 3.7 and 5 g) on the physicochemical properties, antioxidant activity and sensory acceptability of cakes monitored at 0, 7 and 14 days of storage was evaluated and compared with the control cake samples. According to results, increase proportion of GFPP inclusion to cakes increased the moisture, fat, fibre, ash and energy contents, whereas, protein and carbohydrate contents decreased as the proportion of GFPP increased when compared to control cakes. The physical and chemical parameters showed that cake texture, strength, weight, and free fatty acid (FFA) decreased as proportion of GFPP inclusion and storage days increased, while loaf volume, specific volume, and peroxide value (PV) increased with increase proportion of GFPP. Also, loaf and specific volumes were higher in GFPP cakes, whereas texture, strength, weight, FFA and PV were higher in control cakes. Increment of GFPP (3.7-5 g) resulted to about 2 - 3fold significant increase in %DPPH, ABTS, FRAP and total flavonoids (TF) values than in control cakes. Similarly, increase proportions of GFPP strongly inhibited yeast and mould growth when compared to control cakes. It was also found that 3.7 g GFPP cakes at the 7th day and 5 g GFPP cakes at the 14th day of storage had the same sensory acceptability to that of the control cakes. From the results, GFPP cakes resulted to better shelf stability than the control cakes due to antioxidants compound in GFPP which may be termed as functional ingredients.