Selection of level of ingredients in jaggery chocolate using response surface methodology

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Date
2005-08
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Chocolate confectionary has been a novelty food item over the years. Therefore, to remain competitive in this growing industry, confectioners are faced with the challenge of creating innovative product with unique shapes, texture and flavors. Careful choice of their functionality, ingredients provide just one aspect of the complex task of developing new products. Ingredient selection is critical, as it can prevent or invite potential problems in the finished confection. Therefore, experiments were conducted to develop chocolate based on jaggery with the objective to standardization of chocolate manufacturing process, to study the influence of levels of ingredients on its composition characteristics and sensory characteristics and to optimize the process conditions. The experimental design was based on Response Surface Methodology using Central Composite Rotatable Design in 4 variables. The cocoa powder, skim milk powder (SMP), butter and defatted soyflour in per cent were taken at 5 levels. The levels of ingredients were cocoa powder 7, 10, 13, 16 and 19%; SMP 10, 15, 20, 25 and 30%; butter 0, 5, 10, 15 and 20 and soyflour 10, 15, 20, 25 and 30% by weight. Sucrose, reducing sugar, optical density (OD) and sensory evaluation score were taken as dependent variables representing the product quality. For the storage study sucrose, reducing sugar, OD and sensory evaluation score were determined after every 15 days interval for two months. Sensory evaluation of the product was conducted using 10 member panel using 9 point hedonic scale based on color, appearance, taste, texture, flavor and overall acceptability. The experimental results were analyzed to develop second order response surface model for responses using multiple regression. Models obtained for all the responses. The value of R2 for all the models ranges between 0.86-0.99. The physico-chemical and sensory characteristics were found to be statistically significant at 1% probability level for evaluating the quality. The sensory score was taken as the average of scores ten judges. The model was further used to optimize the process conditions. Chocolate prepared in this study had the overall sensory rating ranging from 4.7-8.8 indicating that it lies from ‘Neither like nor dislike to like extremely’. The storage study data indicated that on increasing the level of ingredients and storage period there was a decrease in overall acceptability. Using the models developed for overall acceptability at optimum conditions is predicted as 8.1 with all individual ratings between 7.4-8.1 indicating a chocolate which is liked ‘moderately to very much’. The recommended optimum process conditions for making jaggery chocolate are cocoa powder 9.15%; SMP 23.87%; butter 4.30%; soyflour 26.47%, 3 minute mixing time and 80 rpm mixing speed.
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