Effects of Calcium and pH on Rheological Thermal Resistance of Composite Xanthan Gum and High-Methoxyl Apple Pectin Matrices Featuring Dysphagia-Friendly Consistency

Abstract

High-methoxyl apple pectin (AP) derived from apple was employed as the main ingredient facilitating rheological modification features in developing dysphagia-friendly fluidized alimentary matrices. Xanthan gum (XG) was also included as a composite counterpart to modify the viscoelastic properties of the thickened system under different thermal processes. The results indicate that AP is extremely sensitive to thermal processing, and the viscosity is greatly depleted under a neutral pH level. Moreover, the inclusion of calcium ions echoed the modification effect on the rheological properties of AP, and both the elastic property and viscosity value were promoted after thermal processing. The modification effect of viscoelastic properties (G' and G″) was observed whne XG was incorporated into the composite formula. Increasing the XG ratio from 7:3 to 6:4 (AP:XG) triggers the rheological transformation from a liquid-like form to a solid-like state, and the viscosity value shows that the AP-XG composite system exhibits better thermal stability after thermal processing. The ambient modifiers of pH (pH < 4) and calcium chloride concentration (7.5%) with an optimal AP-XG ratio of 7:3 led to weak-gel-like behavior (G″ < G'), helping to maintain the texture properties of dysphagia-friendly features similar to those prior to the thermal processing.

Keywords: dysphagia; high-methoxyl pectin; rheological properties; texture profile analysis; thermal processing; xanthan gum.

Figure A1

The measured center temperature profile of the 2 wt% high-methoxy AP matrix experienced the preset thermal processes with different time-temperature combinations.

Figure A2

The effects of pH on storage modulus (G′) and loss modulus (G″) of the 2% AP matrices experiencing different thermal processing conditions: (A) prior to thermal process, (B) after a 95 °C for 5 min process and (C) after a 105 °C for 5 min process; (a) oscillatory strain sweeps at the frequency of 50 rad/s, and (b) angular frequency sweeps at 1% strain.

Figure A3

The effects of added calcium chloride anhydrous on storage modulus (G′) and loss modulus (G″) of the 2% AP experiencing a 95 °C thermal process for 5 min: (a) oscillatory strain sweeps at the frequency of 50 rad/s, and (b) angular frequency sweeps at 1% strain.

Figure 1

Storage modulus (G′) and loss modulus (G″) of composite xanthan gum and high-methoxy apple pectin (XG-AP) formula and the corresponding standalone XG thickened matrices based on a 2% weight constraint experiencing different thermal processing conditions: (A). prior to thermal processes, (B). after a 95 °C for 5 min process and (C). after a 105 °C for 5 min. (a) oscillatory strain sweeps at the frequency of 50 rad/s, and (b) angular frequency sweeps at 1% strain.

Figure 2

The effects of 2.5% and 7.5% calcium chloride anhydrous on storage modulus (G′) and loss modulus (G″) of the composite XG–AP (XG0.6AP1.4) thickened matrix experiencing different thermal processing conditions: (A) prior to thermal process, (B) after a 95 °C for 5 min process and (C) after a 105 °C for 5 min process with (a) oscillatory strain sweeps at the frequency of 50 rad/s, and (b) angular frequency sweeps at 1% strain.

Figure 3

The effects of the pH of 2.5% and 7.5% calcium chloride anhydrous on storage modulus (G′) and loss modulus (G″) of the composite XG0.6AP1.4 thickened matrix with 7.5% calcium chloride anhydrous addition (XG0.6AP1.4-Ca.7.5) experiencing different thermal processing conditions: (A) prior to thermal process, (B) after a 95 °C for 5 min process and (C) after a 105 °C for 5 min process with (a) oscillatory strain sweeps at the frequency of 50 rad/s, and (b) angular frequency sweeps at 1% strain.