Impact of high-intensity ultrasound, cooling rate, and storage temperature on physical properties and oil binding capacity in fully hydrogenated palm-kernel lipid matrices

Abstract

The ability of a fat crystal network to entrap liquid oil is known as oil binding capacity (OBC) and is an imperative property in semi-solid fats for use in confectionary, bakery, and snack products. Understanding the factors that increase the OBC of fats is crucial for developing fat-based foods that are more resistant to unwanted oil migration. In this study, fully hydrogenated palm-kernel based (FHPKO) lipid matrices were crystallized under different processing conditions to generate samples with a wide range of physical properties and OBC. Three dilutions were created by combining FHPKO with soybean oil (SBO)—75% FHPKO (containing 25% SBO), 50% FHPKO (50% SBO), and 20% FHPKO (80% SBO) and were crystallized at 33, 30, and 22°C; respectively. All the samples were crystallized using fast (FCR; 4.6°C/min) and slow (SCR; 0.1°C/min) cooling rates, as well as with (w) and without (wo) high-intensity ultrasound (HIU; 20 kHz). These processing conditions resulted in four different sets of samples—FCR wo HIU, FCR w HIU, SCR wo HIU, SCR w HIU. Immediately after processing, the sample's hardness, solid fat content (SFC), viscoelasticity (G′, G″, δ), microstructure, melting behavior (Tpeak, enthalpy), and OBC using a centrifuge method (labeled OBC_c) were analyzed. Samples were then stored at 22 and 5°C for 48 h and the aforementioned properties were measured again as well as OBC using a filter paper method (labeled OBC_p). Results show that both OBC_c and OBC_p were positively correlated with the sample's SFC (r_s = 0.912, p < 0.001; r_s = 0.777, p < 0.001), storage moduli (G′) (r_s = 0.674, p < 0.001; r_s = 0.526, p = 0.017), hardness (r_s = 0.793, p < 0.001; r_s = 0.812, p < 0.001), enthalpy (r_s = 0.842, p < 0.001; r_s = 0.812, p < 0.001), and the number of crystals (r_s = 0.655, p < 0.001; r_s = 0.728, p < 0.001); respectively. While no correlation between OBC_p and the sample's peak melting temperature and microstructure was recorded, a negative association between the sample's peak melting temperature (r_s = −0.782, p < 0.001), phase angle (δ) (r_s = −0.801, p < 0.001), and crystal diameter (r_s = −0.470, p = 0.004) was documented for OBC_c. These results suggest oil binding capacity of palm-kernel based crystallized fats can be increased by formulating harder fats that are elastic, contain more crystals, and have higher SFC and enthalpy. Additionally, the FCR with HIU processing conditions was the most effective in increasing the OBC.