Effect of Solid Fat Content in Fat Droplets on Creamy Mouthfeel of Acid Milk Gels

Abstract

Previous studies have shown that emulsions with higher solid fat content (SFC) are related to a higher in-mouth coalescence level and fat-related perception. However, the effect of SFC in fat droplets on the fat-related attributes of emulsion-filled gels has not been fully elucidated. In this study, the effect of SFC on the creamy mouthfeel of acid milk gel was investigated. Five kinds of blended milk fats with SFC values ranging from 10.61% to 85.87% were prepared. All crystals in the blended milk fats were needle-like, but the onset melting temperature varied widely. Blended milk fats were then mixed with skim milk to prepare acid milk gels (EG10−EG85, fat content 3.0%). After simulated oral processing, the particle size distribution and confocal images of the gel bolus showed that the degree of droplet coalescence in descending order was EG40 > EG20 > EG60 > EG10 ≥ EG85. There was no significant difference in apparent viscosity measured at a shear rate of 50/s between bolus gels, but the friction coefficients measured at 20 mm/s by a tribological method were negatively correlated with the coalescence result. Furthermore, quantitative descriptive analysis and temporal dominance of sensations analysis showed that SFC significantly affected the ratings of melting, mouth coating, smoothness and overall creaminess, as well as the perceived sequence and the duration of melting, smoothness and mouth coating of acid milk gels. Overall, our study highlights the role of intermediate SFC in fat droplets on the creamy mouthfeel of acid milk gels, which may contribute to the development of low-fat foods with desirable sensory perception.

Keywords: acid milk gel; creamy mouthfeel; in-mouth coalescence; solid fat content; tribology.

Figure 1

Polarized light micrographs of blended milk fats; scale bar 20 µm.

Figure 2

(A) Nonisothermal crystallization curves and (B) melting curves of blended milk fats; “1, 2, 3” indicate the first, second and third, respectively. (C) Nonisotermal crystallization melting temperature and total enthalpy of blended milk fats. T_1C and T_2C indicate the temperature of the first and second crystallization peaks; T_1M, T_2M and T_3M indicate the temperature of the first, second and third melting peaks, respectively; Δ_C,Total—the enthalpy of crystallization heat release; Δ_M,Total—the enthalpy of heat absorbed by melting. “—” means not detected in the sample. Results are mean ± SD (n = 3). For each column, ^a–e mean that share the same letter within the same parameter were not significantly different (p ≥ 0.05).

Figure 3

Particle size distribution of acid milk gels (A) before and (B) after simulated oral processing. (C) D₁: volume diameter determined before simulated oral processing; D₂: volume diameter determined after simulated oral processing. Results are mean ± SD (n = 3). For each row, ^a,b,c,d mean that share the same letter within the same parameter were not significantly different (p ≥ 0.05).

Figure 4

Microstructure of acid milk gels before and after simulated oral processing. Red: fat globules; green: protein; scale bar 15 μm.

Figure 5

Rheological curves of acid milk gels (A) before and (B) after simulated oral processing. (C) Tribological curves of acid milk gels after simulated oral processing.

Figure 6

Temporal dominance of sensations curves of acid milk gels with different solid fat contents. (A–E) Acid milk gels: EG10, EG20, EG40, EG60 and EG85.