Multiscale assessment of food lipid structures

Abstract

In these storage organelles lipids exist in liquid and liquid-crystalline (LC) phases, the latter as interfacial layers. In order to use plant lipids in food ingredients and products, they must undergo several structural and compositional conversions in the "farm-to-fork" chain. These processing routes have schematically been depicted for several fat-continuous food products in Figure 1.1. Industrial processing involving shear, temperature and pressure can significantly modulate the self-assembly of lipids (Leser, Sagalowicz, Michel, & Watzke, 2006; Farnaz Maleky, 2015). Lipids can organise themselves in a wide range of hierarchical crystalline and LC structures, which can span multiple scales from nano-, via meso-to macro (Kulkarni, 2012; Leser et al., 2006; Michalski et al., 2013). The organisation of both multiscale crystalline and LC lipid systems is governed by interplay of molecular and colloidal interactions. These underlie the physical properties of lipid systems when they undergo melting, crystallisation, and flow. Figure 1.1. Schematic example of lipid structures as they occur changes throughout the farm-to-fork supply chain of fat-continuous foods. 10 Chapter 1 colloidal dispersions (water-in-oil (W/O) and oil-in-water (O/W) emulsions) which can present a route for effective manufacturing of emulsified food products (Rousseau, 2000; Sato & Ueno, 2011). Current insights in the hierarchical multiscale architecture of fats are schematically summarized in Figure 1.2 (Farnaz Maleky, 2015; Marangoni et al., 2011). The formation of fat crystal network starts with the self-assembly of the TAG molecules into crystalline lamellar mesostructures. These lamellae stack epitaxially to form a crystalline domain, known as a crystalline nanoplatelet (CNP) (Acevedo & Marangoni, 2014). The CNPs can aggregate to larger microstructures that are plate-like, needle-like or spherulitic. Many factors affect the formation and the properties of fat crystal networks (Marangoni et al., 2011). The structural properties of TAG CNPs are influenced by the molecular properties of TAGs and their composition. Traditionally, formation of fat crystal networks via industrial processing routes involves melting and cooling steps. It is well known that changes in the shear rate and temperature during these steps lead to changes in the multiscale crystal network structures in fat-based systems (Farnaz Maleky & Mazzanti, 2018). They determine an intricate interplay between formation of fat crystals and their aggregation into larger structures. The strong coupling of the crystallisation and aggregation is adding significant complexity to the industrial manufacturing of fat-based food products. Figure 1.2. Structural levels present in a triacylglycerol (TAG) crystal network. Adapted from (Marangoni et al., 2019) with permission from Springer. 12 Chapter 1 1.2. Assessment of multiscale lipid structures The heterogeneous composition and structure of lipid-based foods put them among the most challenging systems to be studied at different length scale...