Effect of d‐psicose substitution on gelatin based soft candies: A TD‐NMR study

Abstract

Confectionary gels are considered as composite gel systems composed of high amount of sugar and gelling agent such as gelatin or starch. d‐Psicose is classified as a type of rare sugar, which is a C‐3 epimer of fructose and has 70% of the sweetness of sucrose with a caloric value of 0.39 kcal/g. Utilization of d‐psicose in food products is gaining particular interest due to its low caloric value. In this study, gelatin‐based soft candies were formulated, and the effect of d‐psicose substitution was explored on the quality of the products. For characterization of the soft candies, moisture content, water activity, color, hardness, and glass transition temperature of samples were investigated. X‐ray diffraction analysis was also performed to explain the crystallization tendency of jelly candies. Results showed that, the softest sample with the highest moisture content and the smallest crystallization tendency was the sample that included the highest amount of d‐psicose. Time domain (TD) NMR relaxometry experiments were also conducted on gel samples, and three distinct proton populations were observed in the relaxation spectrum for all formulations. Spin–lattice relaxation times obtained through monoexponential fitting (T1) were also obtained to explain some quality parameters.

Understanding the role of d‐Allulose and soy protein addition in pectin gels

“…In addition to higher hardness values of soy protein containing gels, due to soy protein-pectin gelation, it was observed that addition of D-Allulose also increased the hardness values. This result was not expected since D-Allulose is not good at water binding, 18,28 thus gel matrix was supposed to have still free water which could also hinder the gelation ability of pectin. Considering HMP gel mechanism, sugar is usually added to dehydrate the system, so possible pectin-water interaction, which can result in weak gel structure is not expected.…”

“…This result was not expected since in another study where similar experiments were conducted with gelatin-based candies, D-Allulose had more tendency to retard crystallization while sucrose did not. 18 Moreover, there were numerous studies showing that sucrose had a distinct crystal region and had tendency to crystallize easily. [33][34][35] The previous study conducted with starch, SPI, D-Allulose, and sucrose also showed that in starch gels, sucrose containing gels crystallized more than D-Allulose containing ones which was exactly the opposite of what was observed in this study.…”

“…First proton pool with very short relaxation times (0.7-2.5 ms) was attributed to the protons that were tightly associated with the solid fractions in the sample. 18,38 The second proton pool with longer T 2 (>1.5 ms) was associated with the entrapped water in the gel matrix. T 2 value of the peak 1 was lower than peak 2 for all formulations.…”

“…15,16 T 2 relaxation time gives information about moisture content, formation of new proton pools due to the interaction in the surroundings, and the changes on the state of the water in a system. 17,18 In previous studies, food systems generally showed a multicomponent relaxation behavior. 15,[17][18][19][20] The T 2 results in the present study were discussed in terms of both multicompartmental and noncompartmental perspectives.…”

“…17,18 In previous studies, food systems generally showed a multicomponent relaxation behavior. 15,[17][18][19][20] The T 2 results in the present study were discussed in terms of both multicompartmental and noncompartmental perspectives. Characterization of D-Allulose and soy protein containing starch based gels by using time domain-NMR (TD-NMR) was also investigated in a previous study.…”