Lubricative properties of semi-crystalline lipid systems

Abstract

Fat crystals provide the structural framework of lipid-continuous foods through the generation of a multiscale network. The role of the crystalline lipid phase during oral processing remains largely unexplored, despite being present in a multitude of products. This study explored this role in relation to the macroscopic behavior of full-lipid systems at temperatures relevant to oral processing. Hereto, blends of palm (PO) and canola (CO) oil were crystallized through slow, medium and fast cooling to induce microstructural variations. The crystalline phase at 35°C was characterized and linked to the sample’s rheological and tribological behavior. The solid fat content (SFC) at 35°C was proportionate with the PO level, presenting as particles of various sizes and distinct shapes as revealed through light and electron microscopy. The crystalline fraction impacted the rheological behavior, as demonstrated by the non-Newtonian behavior controlled by the sample’s SFC. The Stribeck curves obtained from tribological analysis showed significant differences between samples, predominantly in the boundary and mixed regime. A novel approach was proposed to interpret the tribological data, which was based on fitting of power functions and evaluation of lubrication regime areas, with the former allowing for the quantification of the progression of friction factors in the lubrication regimes. Tribological behavior was affected by various factors depending on the lubrication regime, including SFC, rheological parameters as well as particle size. Given that PO is the cornerstone of a vast array of food products, insights into a potential relationship with sensory attributes could aid in the product reformulation.