الفهرس 
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Abstract
This study aimed to determine proximate composition, antioxidant activity, total phenols, total flavonoids, phenolic compounds, and flavonoid compounds of raw and baked sweet potatoes. Fat in the cupcake was partially replaced with different levels of baked sweet potato (20, 40, 60, and 80%). The physical properties of batter, chemical, physical and sensory properties of the cupcake were evaluated. The reduced fat cupcake was replaced the diets of obese rats at 2.5 and 5% and study their effects on the body weight gain, organs weight, lipid profile, lipoprotein profile, blood glucose, liver functions, kidney functions, and blood picture.
The obtained results can be summarized as follows:
6.1. Proximate composition of raw and baked sweet potatoes
Raw sweet potato had higher moisture (64%) and crude protein (2.09%) contents than baked sweet potato. However, baked sweet potato had higher crude fat (0.45%), total ash (1.9%), crude fiber (5.1%) and total carbohydrates (58.4%) content than raw sweet potato.
6.2. Antioxidant activity, total phenols and total flavonoids of raw and baked sweet potatoes
Baked sweet potato had higher antioxidant activity (83.3-91.1%), total phenols (81.3-88.3 mg gallic acid/100g), and total flavonoids (24.2-26.6 mg quercetin/100g) than raw sweet potato in both ethanol and methanol extracts. The methanol extract was higher in antioxidant activity, total phenols, and total flavonoids than ethanol extract in both raw and baked sweet potatoes.
6.3. Phenolic compounds of raw and baked sweet potato
Methanol extract (296854.9 ppm) and ethanol extract (51476.8 ppm) of baked sweet potatoes contained higher total phenolic compounds than methanol extract (30924.67 ppm) and ethanol extract (8243.01ppm) of raw sweet potatoes. Pyrogallol, catechin, and benzoic were the most abundant phenolic compounds in the methanol and ethanol extracts of raw and baked sweet potato.
6.4. Flavonoid compounds of raw and baked sweet potato
Methanol extract (84374.5 ppm) and ethanol extract (20618.1 ppm) of baked sweet potatoes contained higher total flavonoid compounds than methanol extract (4399.17 ppm) and ethanol extract (495.05 ppm) of raw sweet potatoes. Naringin, hesperidin, rutin, and rosmarinic were the most abundant flavonoid compounds in methanol and ethanol extracts of raw and baked sweet potato.
6.5. Physical properties of cupcake batter
The specific gravity and pH values of reduced fat cupcake were increased by increasing the level of baked sweet potato in the cupcake butter. However, viscosity values had an opposite trend. Specific gravity, pH and viscosity values of reduced fat cupcake butter were in the range of 1.18-1.37 g/cm3, 6.1-7.3 and 21.6-32.3 CPS×103, respectively.
6.6. Physical properties of cupcake
The non-significant difference was observed in the standing height of the cupcake (4.3-4.5 cm) between control cupcake and reduced fat cupcake. Weights of the cupcake (62.5-71.8 g) were increased by increasing the level of baked sweet potato in the cupcake. However, volume (62.3-79.4 cm3) and specific volume (0.8-1.1 cm3/g) had an opposite trend.
6.7. Proximate composition of cupcake
The moisture content of the reduced fat cupcake was not affected up to 40% fat replacer level. At higher fat replacer levels, moisture content was increased (33.5-34.31%). Crude protein (14.14-15.7%), total ash (2.6-4.1%), and crude fiber (15.2-16.6%) contents were increased by increasing the level of baked sweet potato in the reduced fat cupcake. Crude fat had an opposite trend. Total carbohydrates content of reduced fat cupcake was not affected up to 20% fat replacer level. At higher fat replacer levels, total carbohydrates content was increased (26.12-27.02).
6.8. Crust and crumb color of cupcake
Reduced fat cupcake had the lower crust and crumb L* values (53.8-57.03) and (69.7-73.5), and a* values (17.03-19.12) and (4.8-7.2), respectively, as compared with control cupcake. However, the b* values of the crust and crumb of reduced fat cupcake were not affected by baked sweet potato. The total color (E) of crust (8.85-13.9) and crumb (4.4-5.7) of the reduced fat cupcake was increased by increasing the level baked the sweet potato in the cupcake.
6.9. Texture profile of cupcake
Reduced fat cupcake up to 60% replacement level of baked sweet potato had similar firmness compared with control cupcake. Reduced fat cupcake at 80% replacement level of baked sweet potato had higher firmness value than control cupcake. Gumminess and chewiness values were decreased by increasing baked sweet potato up to 40%. Reduced fat cupcake at 60 and 80% replacement level of baked sweet potato had higher gumminess and chewiness values than control cupcake. Cohesiveness and springiness values were not affected by the sweet potato replacement level.
6.10. Sensory properties of cupcake
The sensory properties of reduced fat cupcake were not affected by replacing margarine in control cupcake with baked sweet potato.
6.11. Biological evaluation of cupcake
6.11.1. Effect of baked sweet potato cupcake on body weight gain of rats
Obese rats had higher initial weights than negative control rats. The final weight of rats fed reduced fat cupcake diets were decreased by increasing the replacement level of baked sweet potato in reduced fat cupcake diets as compared with positive control rats and obese rats fed control cupcake diet. Body weight gain of rats fed reduced fat cupcake diets was reduced by increasing the replacement level of baked sweet potato in reduced fat cupcake diets as compared with positive control rats and obese rats fed control cupcake diet
6.11.2. Effect of baked sweet potato cupcake on organ weight
Organ weight values were significantly decreased by the replacement level of baked sweet potato in reduced fat cupcake diets as compared with positive control rats and obese rats fed control cupcake diet. The obese rats fed reduced fat cupcake diets from 40 to 80% replacement levels for 30 days lead to restoring the normal liver, heart, lungs, and spleen weights of negative control rats. However, obese rats fed reduced fat cupcake diets at any replacement levels for 30 days lead to restoring the normal kidney of negative rats. Non-significant differences in organ weights were observed between reduced fat cupcake diets at 2.5% and 5% replacement level.
6.11.3. Effect of baked sweet potato cupcake on lipids profile
Total lipids and triglyceride values were significantly decreased by increasing the replacement level of baked sweet potato in reduced fat cupcake diets as compared with positive control rats and obese rats fed control cupcake diet. Reduced fat cupcake diets at 5% replacement level were more effective (P≤0.05) in reducing TL values than reduced fat cupcake diets at 2.5% replacement level. However, a non-significant (P>0.05) difference in TG values were observed between 2.5 and 5% replacement level. Reduced fat cupcake at 80% replacement level of baked sweet potato was more effective in reducing TL and TG values than other replacement levels of baked sweet potato. Although reduced fat cupcake diets at different replacement level of baked sweet potato decreased TL values in the obese rats, their values still higher than negative control rats. Obese rats feed with reduced fat cupcake at 60 and 80% replacement level of baked sweet potato for 30 days led to restore the normal serum TG of negative control rats.
6.11.4. Effect of baked sweet potato cupcake on lipoprotein profile
The TC, VLDL, and LDL values were significantly decreased by increasing the replacement level of baked sweet potato in reduced fat cupcake diets as compared with positive control rats and obese rats fed control cupcake diet. However, the HDL value had the opposite trend. Reduced fat cupcake diets at 5% replacement level were more effective in reducing TC and LDL values than reduced fat cupcake diets at 2.5% replacement level. Reduced fat cupcake at 80% replacement level of baked sweet potato was more effective in reducing TC, VLDL and LDL values and increasing HDL value than other replacement levels of baked sweet potato. Although reduced fat cupcake at different replacement levels of sweet potato decreased TC and LDL and increased HDL values
in the obese rats, their values still higher and lower, respectively than negative control rats. Reduced fat cupcake at a 60-80% replacement level of baked sweet potato led to restore the normal VLDL value of negative control rats.
6.11.5. Effect of baked sweet potato cupcake on blood glucose
Blood glucose level was significantly decreased by increasing the replacement level of baked sweet potato in reduced fat cupcake diets as compared with positive control rats and obese rats fed control cupcake diet. A non-significant difference in blood glucose level was observed between reduced fat cupcake diets at 2.5% and 5% replacement level. Reduced fat cupcake at 80% replacement level of baked sweet potato was more effective in reducing blood glucose levels than other replacement levels of baked sweet potato. Although reduced fat cupcake at different replacement levels decreased blood glucose levels in the obese rats, their values still higher than negative control rats.
6.11.6. Effect of baked sweet potato cupcake on kidney functions
Blood urea and serum uric acid were not affected by baked sweet potato at any replacement level. However, serum creatinine was significantly decreased by increasing the replacement level of baked sweet potato in reduced fat cupcake diets as compared with positive control rats and obese rats fed control cupcake diet. A non-significant difference in serum creatinine was observed between reduced fat cupcake diets at 2.5% and 5% replacement level. Reduced fat cupcake at 80% replacement level of baked sweet potato was more effective in reducing serum creatinine than other replacement levels of baked sweet potato. Feeding obese rats with a reduced fat cupcake at 80% replacement level of baked sweet potato for 30 days led to restoring the normal serum of negative control rats.
6.11.7. Effect of baked sweet potato cupcake on liver functions
The ALP and ALT enzymes were significantly decreased by the replacement levels of baked sweet potato in reduced fat cupcake diets as compared with positive control rats and obese rats fed control cupcake diet. A non-significant difference in ALP enzyme was observed among the replacement levels of baked sweet potato in reduced fat cupcake diets. On the other side, the AST enzyme was significantly decreased by increasing the replacement level of baked sweet potato in reduced fat cupcake diets as compared with positive control rats and obese rats fed control cupcake diet.
A non-significant difference in ALP, ALT and AST enzymes was observed between reduced fat cupcake diets at 2.5% and 5% replacement level. Reduced fat cupcake at 80% replacement level of baked sweet potato was more effective in reducing AST enzyme than other replacement levels of baked sweet potato. Feeding obese rats with a reduced fat cupcake at 80% replacement level of baked sweet potato for 30 days led to restoring the normal AST enzyme level of negative control rats. Although reduced fat cupcake at different replacement levels decreased ALP and ALT enzymes in the obese rats, their values still higher than negative control rats.
6.11.8. Effect of baked sweet potato cupcake on blood picture
Blood picture of rats was not affected by obesity and reduced fat cupcake diets at any replacement level of baked sweet potato.