Introduction

Self-standing solid-like structures from liquid vegetable oil, the so-called oleogels, has recently received significant attention due to its potential to replace trans-fat and reduce saturated fats in confectionery, baked products, and processed meats (Marangoni, Van Duynhoven, Acevedo, Nicholson and Patel, 2020) In conventional oleogels, the structure-forming agents are typically small molecule oleogelators, such as plant waxes, fatty esters, monoacylglycerols, and ethyl cellulose (Patel and Dewettinck, 2016, Singh, Auzanneau and Rogers, 2017). However, with more attention towards ‘clean label’ and ‘healthy’ alternatives, the use of food hydrocolloids such as gums, and proteins as oleogelators has recently gained more consideration (Doan, Van de Walle, Dewettinck and Patel, 2015, Gravelle, Blach, Weiss, Barbut and Marangoni, 2017, Gravelle and Marangoni, 2018, Lim, Hwang and Lee, 2017). However, these hydrophilic biopolymers are unable to form a crosslinked network via intermolecular interactions if directly added into the oil; therefore, indirect approaches are required to form a structured oil phase. DeVries and coworkers successfully converted whey protein stabilized hydrogels into oleogels by a step-wise solvent exchange process (de Vries, Hendriks, van der Linden and Scholten, 2015, de Vries, Wesseling, van der Linden and Scholten, 2017). κ-Carrageenan stabilized hydrogels were also converted into aerogels using supercritical carbon dioxide and then into oleogels by allowing the aerogel to adsorb liquid oil (Manzocco, Valoppi, Calligaris, Andreatta, Spilimbergo and Nicoli, 2017). Combinations of surface active and non-surface active biopolymers, such as hydroxypropyl methylcellulose (HPMC) or methylcellulose (MC) with xanthan gum (Patel, Cludts, Bin Sintang, Lewille, Lesaffer and Dewettinck, 2014); and soy protein isolate with κ-carrageenan (Tavernier, Patel, Van der Meeren and Dewettinck, 2017) were also used to develop emulsion-templated oleogels by removing the water using freeze-drying or vacuum-drying process. Patel and coworkers were the first to use an HPMC foam-templated approach to obtain oleogels (Patel, Schatteman, Lesaffer and Dewettinck, 2013). The freeze-dried HPMC foam was able to hold an oil 98 % of the foam weight. However, one of the most popular biopolymers, pulse proteins, such as those from pea, lentil and faba bean have not been explored significantly for oleogelation, despite their nutritional and functional quality and higher consumer acceptance.
Our recent studies demonstrated that freeze-dried foams stabilized by combinations of a pea or faba bean protein concentrates with xanthan gum (XG) can be used to structure canola oil (CO) (Mohanan, Tang, Nickerson and Ghosh, 2020). The foams prepared with 5 wt% faba bean protein concentrate (FPC) or pea protein concentrate (PPC) with 0.25 wt% XG at pH 7 and pH 9 were able to hold an oil more than 20 – 30 times of their weight. However, about 30-40% of the added oil was leaked out of the oleogel upon centrifugation (Mohanan, Tang, Nickerson and Ghosh, 2020). Due to the poor oil binding capacity of the protein foam-templated oleogels, their rheological properties were unreliable. Higher oil leakage during rheology measurements of the oleogels led to a significantly higher storage modulus (G’) compared to the oleogels with higher oil content (or higher oil binding capacity). Also, the baking quality of the cakes baked using the oleogels was poor due to significantly higher hardness and chewiness compared to a cake baked using conventional high-melting shortening (Mohanan, Tang, Nickerson and Ghosh, 2020). Therefore, the objective of the present study was to improve the oil binding properties of the pulse protein foam-templated oleogels using small quantities of conventional oleogelators, such as high-melting monoacylglycerols (MAG) and candelilla wax (CW). We hypothesized that the oleogelators would act as fillers in the protein network to reduce the oil loss (OL) and improve the rheology of the oleogels and therefore improve the textural properties of the cakes. The overall goal was to see how much of the conventional high-melting shortening functionality can be mimicked by the pulse protein-based oleogels.