الفهرس 
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Abstract
Dietary fat is a major energy source, essential for growth and development, and provides essential fatty acids needed for maintaining structure of cell membrane and for prostaglandin synthesis. Also, fat aids in the absorption of fat-soluble vitamins and other phytochemicals. Fats are responsible for the aroma and texture of many foods, thereby affecting the overall palatability of diet. Although fat in food may increase acceptance, high-fat foods and diets are also high in calories, which may be problematic for health, such as obesity, cancer, cardiovascular disease, and type 2 diabetes. So, new trends in food science take the reduction of the fat content of foods as an aim. Modification of the food supply through the use of fat replacers is often viewed as an efficacious way to achieve this goal. Several bakery products such as cakes and cookies are known for their high fat content. Therefore, the present study was carried out to investigate the effect of using some fat replacers on the physical, chemical and sensory properties of such products. Two types of fat replacers (flaxseed gum and okra gum) were used to replace 25, 50, 75 and 100% of fat (butter) used in the production of cakes and cookies.
The results obtained from the present study could be summarized as follows:
Effect of using flaxseed gum on cake characteristics:
1- The proximate chemical analysis showed that fat-replaced cakes had higher moisture and carbohydrate contents, while fat content was significantly lowered by increasing fat replacement level by percentages of 15.93, 32.92, 56.83 and 86.70% of original cake fat content at fat replacement levels of 25, 50, 75 and 100%, respectively. The associated reduction in caloric value was 3.84, 8.11, 13.82 and 21.22% for the above mentioned replacement levels, respectively.
2- Physical properties of cake indicated that replacing butter in cake formula with flaxseed gum caused a decrease in cake weight, volume, height and specific volume as fat replacement level increased. The pH of cake was not affected by fat replacement.
3- Texture profile analysis (TPA) showed that fat-replaced cake had significantly low hardness, gumminess and chewiness, while cohesiveness, springiness and resilience were not affected by the fat replacement levels.
4- The sensory evaluation results, of replaced cakes indicate that fat replacement did not have any significant effects on colour, whereas, flavour and texture and overall acceptance were highly accepted up to fat replacement levels of 75%.
Effect of using okra gum on cake characteristics:
1- Moisture content was higher in fat-replaced cakes when compared to the control cake, while fat content was significantly lowered by increasing fat replacement level by percentages of 19.19, 35.31, 52.99 and 74.59% than the control for fat replacement levels of 25, 50, 75 and 100%, respectively. The caloric value of cakes was decreased by 4.61, 8.35, 12.78, and 19.42% for the above mentioned replacement levels, respectively.
2- Replacing butter in cake formula with okra gum did not have any significant effects on volume of cake up to fat replacement level of 75%, while weight and height were significantly lowered by increasing fat replacement level.
3- Texture profile analysis (TPA) showed that fat-replaced cakes had significant low hardness, gumminess and chewiness, while cohesiveness, springiness and resilience were not significantly affected by fat replacement level.
4- Sensory evaluation results indicated that okra gum replacement did not have any significant effects on colour and flavour, as for texture and overall acceptance it was highly accepted up to fat replacement level of 75%.
Effect of using flaxseed gum on cookies characteristics:
1- Proximate chemical analysis results showed that cookies with flaxseed gum had higher moisture and carbohydrate, and lower fat contents. The caloric value of the produced cookies was lower than the control cookies by 3.49, 7.37, 13.41 and 18.98% than that of control cookies at fat replacement levels of 25, 50, 75 and 100%, respectively.
2- Cookies prepared with flaxseed gum as a fat replacer showed higher volume and specific volume, but on the other hand, the height and width of cookies were significantly different as compared to control.
3- Texture profile analysis (TPA) showed that hardness was not affected by fat replacement level up to 50%.
4- The sensory evaluation of cookies showed that, colour, flavour and overall acceptance were not significantly affected by fat replacement levels, and texture up to 75%.
Effect of using okra gum on cookies characteristics:
1- Cookies made with okra gum as a fat replacer had higher moisture, protein and carbohydrate contents than the control cookies. The caloric value of the produced low fat cookies was lower by percentages of 2.70, 7.59, 12.00 and 18.68% than the control cookies for fat replacement level of 25, 50, 75 and 100%, respectively.
2- Physical properties results indicated that low-fat cookies with okra gum had higher volume and specific volume, while their weight, height and width were lowered.
3- Texture profile analysis (TPA) showed that hardness was not affected by fat replacement level up to 75%.
4- The sensory evaluation results showed that fat replacement did not have any significant effects on colour, flavour, texture and overall acceptance.
Finally, it could be concluded that fat replacers under investigation (flaxseed gum and okra gum) can be used effectively to replace portions of fat up to 75% in cakes and cookies while keeping the good sensory quality characteristics. Additionally, such replacement has achieved many economical, nutritional and health benefits when consuming the produced low-fat bakery products.