Effect And Possible Mechanism Of Macromolecular Hydrocolloids On Sweetness Intensity Of Aspartame

Food is a complicated system which contains protein, polysaccharide and other additives and most researches focused on the sweetness variation have been always performed in pure water. Therefore the effects of hydrocolloids on the sensory properties of food have been the subject of thorough investigations. The study involved the effects of hydrocolloids on sweetness variation of sweeteners mainly concentrated on the sensory evaluation and most of the sweeteners used were natural sweeteners, so there were little study referred to the effects of hydrocolloids on aspartame and the mechanism was still unclear.It is well known that the initial event of sweetness sensation generally involves stereo specific binding of sweet compounds packed with water to the sweet taste receptor. Therefore, the relationship between chemical structure of sweeteners with various sweetness intensities and its interaction with the taste receptor has always been an important subject of keen interest to chemists. Since the pure receptor protein is not available now, we tried to use fullerenols as an artificial sweet taste receptor model for the thermodynamic research of the interaction of sweeteners with the receptor by use of Isothermal Titration Calorimetry (ITC) and found that thermodynamic parameters were correlated well with the sweet intensity of some sweeteners. The thermodynamic basis for the initiation of sweetness inhibition as well as that for sweetness differences between the enantiomers of amino acids and monosaccharides were also proposed subsequently.In this study we continued to employ fullerenols as artificial sweet taste receptor to study the change of sweet intensity of aspartame in different concentrations of ydrocolloids. Based on the sensory variation of aspartame in different concentrations of hydrocolloids, we systematically studied the possible influence factors about the binding thermodynamics between aspartame and fullerenols, the diffusion and relaxation properties in solution, as well as the change of moisture distribution and viscosity. Our study aims to further understand the mechanism of sweet taste variation in the presence of hydrocolloids and provide the theoretical basis for designing food formula and developing new products.(1) Experimental study for the mechanism of sweet intensity variation in the presence of cationic hydrocolloidsWe chose sodium carboxymethylcellulose (CMC-L) and sodium alginate (SA) to study the effects of cationic hydrocolloids on sweet intensity of aspartame and found that the taste suppression occurred in the high concentrations of CMC-L, while the sweet taste in SA was not changed. We also found that the binding constants of interaction between fullerenols and aspartame decreased as the concentrations of CMC-L and SA increased, which implied that the presence of SA or CMC-L weakened the binding strength between aspartame and fullerenols in the key step. The variation in moisture distribution and relaxation properties of CMC-L or SA after addition of aspartame was subsequently investigated and the results suggested that the amount of bound water in CMC-L was remarkably enhanced and the diffusion of molecules was suppressed, while in the case of SA, the decreased viscosity due to the presence of aspartame and the comparatively higher amount of free water facilitated the diffusion of sweetener. And all of these facilities of viscous solution might compensate for the decreased binding constant between aspartame and receptor, which made SA not show significant suppression on the sweetness intensity. Besides, we investigated the effects of sodium ions, potassium ions, calcium ions, magnesium ions on the interaction between aspartame and fullerenols and elicited that all the four ions decreased the primary binding affinity of the interaction between aspartame and fullerenols.(2) Experimental study for the mechanism of sweet intensity variation in the presence of ionic hydrocolloidsFurther study on the effects of guar gum (Guar) and locust bean gum (LBG) on sweet intensity of aspartame, we found that the sweet taste suppression in the presence of Guar and LBG was similar to CMC-L which exhibited the sweetness inhibition of aspartame. The binding strength between aspartame and fullerenols in the key step weakened with the enhanced concentration of CMC-L and SA, and the binding constant for the interaction between aspartame and fullerenols showed a sharp reduction when the concentrations of hydrocolloids were higher than their coil overlap concentrations (C). And by the study of variation in moisture distribution and diffusion properties, we concluded that the amount of bound water in Guar and LBG increased with the enhanced concentrations of hydrocolloids and the amount of bound water was apparently increased when the concentrations of hydrocolloids were higher than C*. The diffusion properties in the solution also changed with the addition of Guar and LBG Thus, the variation of moisture distribution and diffusion properties might both reduce the sweet intensity of aspartame. It is worthy to notice that the viscosity and the amount of bound water of LBG were higher than Guar, so the inhibition effect was much more obvious in LBG...