USE OF TIME DOMAIN (TD) AND FAST FIELD CYCLING (FFC) NMR RELAXOMETRY TO DESIGN AND CHARACTERIZE SOFT CANDY PRODUCTS

2021-8-20
Poçan, Pelin
Confectionary gels are considered as composite gel systems consisting of high amount of sugar and gelling agents such as gelatin or starch. Production of low-calorie soft confectionery products has been the interest of the industry in recent years. D‐allulose is classified as one of the rare sugar; sugars which are found in rare amounts in nature. It is a C‐3 epimer of fructose and has 70% of the sweetness of sucrose with much less caloric value of 0.39 kcal/g compared to common sugars. Utilization of D‐allulose in food products is gaining particular interest due to its low caloric value. In this study, D-Allulose was used to formulate soft candies. NMR Relaxometry based methods are known as nondestructive techniques and can be used to obtain significant information on the physiochemical properties of many food systems. Time Domain (TD) and Fast Field Cycling (FFC) NMR Relaxometry are the two methods that can be used for characterization purposes. Time domain methods mostly rely on the interpretation of spin-spin (T2) and spin-lattice (T1) relaxation times at a fixed magnetic field strength whereas FFC NMR uses a changing magnetic field to obtain information at molecular level. In this dissertation, allulose containing soft candies were formulated using different gelling agents and gels were characterized by different relaxometry techniques. In the 1st part of the study, effect of D‐allulose substitution was explored on the quality of the gelatin-based candies by using Time Domain NMR methods. 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‐allulose. Time domain (TD) NMR relaxometry experiments were conducted on gel samples through the measurement of T2 and T1 relaxation times at a 20.35 MHz system. T2 results showed the presence of three distinct proton populations in the relaxation spectrum for all formulations. Spin–lattice relaxation times obtained through mono-exponential fitting (T1) were also obtained to explain some quality parameters. In the second part of the study, again effect of D-allulose substitution on gelatin based confectionery gels were studied by using Fast Field Cycling (FFC) NMR relaxometry. . For this part of the study, 1H spin-lattice relaxation (T1) experiments for gelatin-based candies prepared by different amounts of D-allulose have been performed in the frequency range of 4 kHz–40 MHz. In addition, physical properties such as moisture content and hardness were also measured. Analysis of NMR dispersion profiles showed the presence of two fractions of water: confined and free-water. The relaxation data have been associated with parameters characterizing translation diffusion and rotation of the confined-water molecules and dynamics of the free-water fraction. The translation dynamics has turned out to be about three orders of magnitude slower compared to bulk water; the time scale of the rotational dynamics was similar to that of translation diffusion. Moreover, quantitative analysis of the relaxation data provided a unique parameter, the number of water molecules undergoing translation dynamics within the confined-water fraction per unit volume. On this basis, the influence of D-allulose on the mechanisms of water motion were discussed. In the 3rd part of of the dissertation, starch based confectionery gels were examined by using both TD-NMR and FFC NMR relaxometry experiments. This time allulose was not used but focus was the use of relaxometry techniques on the starch based candies formulated using different corn syrup types. As the system of interest, Turkish delights (lokum) being starch based confectionery gels were formulated. Turkish delights are traditional confectionery products that contains mainly sucrose as the sugar source and starch as the gelling agent. However, manufacturers sometimes might prefer to use corn syrup instead of sucrose to decrease the cost. This case jeopardizes the originality of Turkish delights and led to production of adulterated samples. In this part of the study, Turkish delights were formulated by using sucrose (original one) and different type of corn syrups (SBF10, SCG40 and SCG60). For all samples, moisture content measurements, texture profile analysis (TPA), X-ray Diffraction Analysis, color analysis, TD-NMR and FFC-NMR experiments were performed. FFC experiments were also performed at two different temperature: 4 ͦ C and 25 ͦ to understand the water dynamics of the samples at different temperatures. Results clearly indicated that, corn syrups containing samples had improved textural properties and were less prone to crystallization. However, this case affected the authenticity of the products. Both TD-NMR and FFC-NMR techniques were found to be effective to discriminate the original samples from the corn syrup containing ones. According to the results of TD-NMR experiments, two distinct proton population was observed for all formulations. In addition, quantitative analysis of FFC-NMR showed that, apart from the rotational motions, molecules in Turkish delights (mainly water but also sugar molecules) undergo two types of translational dynamics. To summarize, this dissertation enlightens the possible application areas of TD-NMR and FFC-NMR to characterize the soft candy products as an alternative to the commonly used well-known methods such as X-ray Diffraction, Thermo-gravimetric Analysis (TGA) or Texture Profile Analysis (TPA). In addition, it gives deep insight to the researchers about the utilization of TD-NMR and FFC-NMR Relaxometry as an authenticity and quality detection tool for the analysis of confectionery gels.

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Citation Formats
P. Poçan, “USE OF TIME DOMAIN (TD) AND FAST FIELD CYCLING (FFC) NMR RELAXOMETRY TO DESIGN AND CHARACTERIZE SOFT CANDY PRODUCTS,” Ph.D. - Doctoral Program, Middle East Technical University, 2021.