In a developed society, health problems such as the risk of weight gain, diabetes, and heart diseases are often associated with a high-sugar diet. Food product reform is seen as one of the tools to promote healthier eating. Calorie-reduced product processing not only targeted diabetics but now also focuseds on human health. The experiments were designed based on the response surface methodology using the three-level-three-factor BoxBehnken design with total soluble solid (TSS) (40%50%), low methoxyl pectin (LMP) (0.1%0.3%), and kappa-carrageenan (k-carrageenan) (0.1%0.3%) at a constant fruit batch of 10 kg. In the evaluation of jam, the viscosity, water activity, and bioactive compounds (anthocyanin, total polyphenol, and vitamin C) were determined and optimized in order to produce reduced-calorie blackberry jam (filling type) with favorable viscosity, water activity, and bioactive compounds. The results showed that the model fit was significant (p < 0.05); a satisfactory correlation between the experimental and the predicted values was found (high coefficient of determination R2). All three factors affect the quality of the products, with sugar showing significant influence on physical characteristics, maintaining bioactive compounds and overall acceptability of the product. The overlay contour plot of quality attributes showed that the reduced-calorie blackberry jam should use 0.18% LMP , 0.22% k-carrageenan, and 45% TSS. Thus, the reduced-calorie jam produced from these optimum levels had better characteristics than the others.
Key words: reduced-calorie jam; blackberry; response surface methodology; optimization; Box-Behnken design.
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