Yumuşak kurabiyelerde şeker miktarının stevia ile azaltılması

Sugar content of foods is being reduced due to adverse health effects of excessive sugar consumption. Low sugar and low calorie products can be produced by using artificial sweeteners. However, natural additives are preferred to artificial ones due to possible health effects. Snack foods are one of the main sources of sugar in diet. Among the baked snack foods, cookies are known for their high ratio of sugar in their formula. Depending on the cookie variety, sometimes this ratio can be upto 65% percent of the dry matter. Stevia is a natural sweetener that can be used for sugar reduction. It contains sweet tasting compounds named as steviosides. Rebaudioside A is the sweetest compound present in stevia which is approximately 350-400 times sweeter than sucrose. In this study, development of reduced-sugar soft cookies by using stevia extract was investigated. Sweet compounds were extracted from dried stevia leaves with hot water as it is the best solvent according to the previous studies in literature. American soft cookie was chosen as a model cookie type. Buttermilk powder was used as a bulking agent and to improve the flavor, color and texture of the cookies. Other ingredients were flour, margarine, powdered granulated sugar, salt, sodium bicarbonate and water. Creamery method of production was used for cookie preparation. Amounts of water, stevia and buttermilk powder and baking duration for each formulation was determined by preliminary experiments. Four formulations were developed in which the sugar content was reduced by 30 and 60% by stevia extract with and without buttermilk powder at a level of 5%. Flour:water ratio was kept constant in all formulations. Baking time was modified to obtain a moisture content of 8% in cookies for all formulations. A control and an only buttermilk powder containing cookies were also produced for comparisons. Moisture content, water activity, spread ratio, color, textural properties and HMF content of the cookies were measured. Flavor and texture of the cookies were evaluated according to descriptive sensory analysis method. The changes in the properties of cookies after 60 days of storage in polyethylene terephthalate (PET) containers at 25°C were also determined. Spread ratio of stevia containing cookies was significantly lower than that of control sample. Only buttermilk powder containing sample had the highest spread ratio. Weight loss of cookies after baking differed in accordance with baking duration to obtain 8% moisture content. After 60 days of storage at 25°C, the greatest weight loss was determined in 30% reduced-sugar sample. Significant decrease in moisture content was observed in all of the cookies after storage. Moisture content of the 60% reduced-sugar sample was similar to that of the control sample. Highest initial water activity was obtained in the 60% reduced-sugar sample. After storage, water activity values of the control and buttermilk powder containing samples were significantly higher than those of stevia containing cookies. All cookies exhibited lower L* values than the control cookie. b* values of all the samples were close to each other. The lowest a* value was found in control cookie. Addition of buttermilk powder to the cookies resulted in an increase in a* value. Total color change values of the samples were calculated by taking the color values of control sample as reference. Total color change values of both stevia and buttermilk powder containing samples were higher than those of the other samples before storage. Highest total color change value was observed in only buttermilk powder containing sample after storage. Hydroxymethylfurfural (HMF) content of all of the cookies was found lower than those reported for commercial cookies. Initial hardness values of both stevia and buttermilk powder containing samples were similar to that of control sample. Initial hardness of only stevia containing samples was significantly higher than that of the control sample. Hardness of all of the samples increased significantly after 60 days of storage. Highest work to break down value was determined in 30% reduced-sugar sample. In sensory evaluations, sweet taste score of control and buttermilk powder containing samples was highest and that of 60% reduced-sugar sample with buttermilk powder was the lowest. Aftertaste score of 60% reduced-sugar sample with buttermilk powder was the lowest. Rest of the samples had similar aftertaste scores. Butter taste score of only buttermilk powder containing sample was significantly higher than those of others. Crispiness of 30% reduced-sugar sample was the greatest among samples. The sample with only buttermilk powder was given the highest overall acceptability score. Both stevia and buttermilk containing samples were found similar to the control sample in terms of overall acceptability. Unlike most of the artifical sweeteners, no metallic or bitter taste was observed in stevia containing samples at levels used in this study. Use of combination of stevia extract with buttermilk powder in formulation resulted in cookies with similar quality properties to those of the control sample. Therefore, stevia extract and buttermilk powder can be used for production of reduced-sugar soft cookies. Buttermilk powder contributed positively to the flavor, texture and color of soft cookies. However, it should be taken into account that buttermilk powder can undergo browning during cooking. Therefore, its usage level, baking temperature and duration should be adjusted accordingly.