INFORM September 2024

SOFT MATERIALS

inform September 2024, Vol. 35 (8) • 15

OIL BEHAVING LIKE SOLID FAT An oleogel is a liquid oil that has been structured through the formation of an internal network. Primarily composed of liquid oil, they do not impart the negative health effects of solid fat, yet the gelling network gives the material solid-like properties. These solid-like properties are directly related to the strength of the network formed by the gelling agent. Since the early 2000s when Gandolfo, Bot and Flöter (https://doi.org/10.1007/ s11746-004-0851-5) used small molecules (fatty acids, fatty alcohols and their mixtures) to gel edible oils, the field of oleo gelation has exploded with new modes of gelation being dis covered each year. Simply forming an oleogel is not enough to replace solid fat. In fact, replacing one solid fat with another in food formulation is unlikely to produce the desired effects of the original fat. This is because each fat has specific properties based on its composi tion, like melting temperature and morphology (crystal shape). To complicate this further, fats are polymorphic which means that they can crystallize in several crystal structures, each with a distinct melting temperature and crystal morphology. To replace solid fats with an oleogel, understanding the structure-function relationships in each material is imperative. The most widespread gelator for oils are natural waxes, such as bee, rice bran, or candelilla which are upcycled, waxy byproducts of current agricultural processing. These waxes recrystallize to form an interconnected network of wax crys tals and gel at a concentration as low as one percent. However,

North America

Europe

Oceania

South America

World

Asia

Africa

140g

120g

100g

80g

60g

40g

20g

0g

1961

1970

1980

1990

2000

2010

2021

Increase in average fat supplied per household between 1961 and 2021. Source: https://tinyurl.com/2kzwdpyt

these gels are delicate and leak liquid oil after the network is broken during spreading, scooping, or mixing. Adding more wax improves the structural and oil binding properties, but gives the oleogel a waxy mouthfeel, increases the melting tem perature of the gel, and imparts off flavors. In addition, the interaction of oleogels with particles and other components of a food matrix is not well understood, but relevant given the compositional variety of formulations. So, how do we face