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In vitro digestibility of soy-protein isolate containing soft candies formulated with d-psicose

Sakar, Elif Gökçen
Commercial soft candy products are known to contain high amount of sugar and therefore they are considered as not healthy and high calorie sweets. Most of the candy present in the market are made by sucrose and as a gelling agent, gelatin and sometimes starch or pectin is being used. In this study, D-Allulose (rare sugar), soy protein isolate (SPI) and pectin were used to prepare different soft candy formulations. D-Allulose was used as a replacement of sucrose at different ratios (Sucrose/D-Allulose: 0/35, 10/25, 20/15, 35/0) so that high calorie concern will be out of the subject since D-Allulose’s caloric value is approximately 0.4 Kcal/g. Furthermore, pectin is a plant based gelling agent and also known as dietary fiber. Therefore, it will be a good replacement compared to gelatin, that is an animal-based gelling agent, considering vegans, vegetarians and consumers who are trying to eat halal food. Finally, adding SPI to the formulation could definitely increase the perception of the product for the confectionary industry. Pectin was used at a concentration of 4% (w/w) whereas SPI was added at 2% (w/w). In addition to the conventional candy characterization experiments, digestion behavior of the candies in simulated gastric media were also examined and characterization experiments were also conducted during digestion. During gastric digestion, brix of the gels was recorded. Before digestion, physical properties, such as hardness, moisture, water activity, pH, color were measured for the candies and morphologies of the candies were determined using scanning electron microscope (SEM) experiments. In addition to these physical measurements, Time-Domain NMR (TD-NMR) experiments were also conducted. T2 relaxation times were measured to determine how the water distribution in the samples changed in the samples before and after digestion and to observe how the rare sugar D-Allulose changed this distribution. To observe how D-Allulose and SPI changed the molecular dynamics of the soft candies, Fast Field Cycling (FFC) NMR Relaxometry experiments (through T1 relaxation times) were conducted as well. X-ray diffraction experiments were performed to measure the crystallization behavior of the confectioneries. D-Allulose was found to increase the crystallization ability of pectin-containing candies, whereas sucrose containing samples experienced no crystallization. Higher hardness values were obtained for the soy protein containing candies due to pectin-soy protein interaction. Also, higher moisture content was obtained soy protein containing candies. Moreover, mathematical modelling was performed by using Power law model (R2>0.98) and the dissolution constant was calculated for the samples. Dissolution constant of the SPI containing candies showed no significant difference (p>0.05) as sugar type changed while for non-soy protein containing candies, it was significant (p<0.05). Sugar type and SPI addition was found to have impact on soft candy formulations.