Food Hydrocolloids 130 (2022) 107691 Available online 6 April 2022 0268-005X/© 2022 Elsevier Ltd. All rights reserved. Chickpea four and soy protein isolate interacted with κ-carrageenan via electrostatic interactions to form egg omelets analogue Zhou Lu a , Pin-Rou Lee c , Hongshun Yang a, b, * a Department of Food Science & Technology, National University of Singapore, Singapore, 117542, Singapore b National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou Industrial Park, Suzhou, Jiangsu, 215123, PR China c Aztech Technologies Pte Ltd, 31 Ubi Road 1, #01-05, Singapore, 408694, Singapore A R T I C L E INFO Keywords: Egg analogue Plant-based protein Gelation Rheology Interaction Microstructure ABSTRACT In recent years, demand for the plant-based egg substitutes has increased signifcantly, especially in Singapore, a country seeking for innovative food sources imminently. In the current study, chickpea four, soy protein isolate, shortening, baking powder, mono, diglyceride, transglutaminase, potassium chloride, four, and hydrocolloids (κ-carrageenan (κ-C) or gellan gum (GG)) were used to develop the eggless omelets. A formulation comprising 0.3% κ-C (0.3κ-C) best matched the physiochemical properties of egg, in terms of hardness (4437 vs. 4614 g), specifc volume (1.24 vs. 1.19 cm 3 /g), and gel strength (19.3 vs. 17.5 kPa). This could be attributed to the highest synergistic κ-C-protein interactions in 0.3κ-C, along with the most homogeneous gel structure observed under confocal laser scanning microscopy (CLSM). The addition of 0.1% κ-C induced more κ-C-protein interactions than the one without hydrocolloids, but such increase was not as dominant as 0.3κ-C. When the κ-C concentration reached 0.5%, however, the rheological synergism decreased while the electrostatic interactions increased; that signifes the increased κ-C-κ-C interactions. Contrastingly, a segregated GG-protein interaction occurred in all GG systems, as indicated from synergism and CLSM images. These differences in interactions and structures affected the macroscale properties of our plant-based egg products, explaining the different physiochemical properties among them. A schematic diagram was therefore proposed to build connections between physiochemical properties, interactions, and structure. 1. Introduction The global egg replacement ingredients market has reached USD 1.4 billion in 2021 and is expected to surpass USD 1.6 billion by 2026 (Market Data Forecast, 2021). The growing interest in the development of egg substitutes is driven by various factors, such as consumer pref- erence, reducing allergens, enhancing food safety, improving nutrition profle, reducing price volatility, and promoting environmental sus- tainability (Grizio & Specht, 2018). In Singapore, the current high egg consumption (388 pieces per capita (Singapore Food Agency, 2020)) relies mostly on importation from Malaysia (73%). The shortage of egg supplies from overseas during avian infuenza period, and the more energy required to produce eggs than that to produce milk and raise swine combined (Sabate & Soret, 2014), have driven a rapid shift in egg markets from animal products to plant-based alternative. The plant-based egg replacement category has already experienced some early harbingers, such as egg-free mayonnaise and dressings (Ali & EL Said, 2020; Armaforte, Hopper, & Stevenson, 2021), eggless cakes (Lin, Tay, Yang, Yang, & Li, 2017a; 2017b), and eggless noodles (Khouryieh, Herald, & Aramouni, 2006). Currently, several companies (e.g., Oggs Aquafaba, Just egg, Beyond egg, etc.) have launched novel plant-based egg products that successfully mimic the taste and appear- ance of eggs. From all these egg replacement applications, it was noted that the combination of proteins, hydrocolloids, and emulsifers was promised in developing egg substitutes (Keys & Goldberg, 2018). In the current study, chickpea four and soy protein isolate were selected as protein sources due to their exceptional emulsifying, foaming, and gel- ling properties, nutritional value, low cost, and wide availability (Bou- kid, 2021; Grizio & Specht, 2018; Romagnesi & Sharma, 2021; S¨ oderberg, 2013). In addition, κ-carrageenan (κ-C) and gellan gum (GG) were evaluated to further improve our eggless formulations based on their thickening, gelling, and water binding capacity (Saha & Bhatta- charya, 2010) and the successful application in eggless products (Just egg, 2019; Keys & Goldberg, 2018). * Corresponding author.Department of Food Science & Technology National University of Singapore Science Drive 2 Singapore, 117542, Singapore. E-mail address: fstynghs@nus.edu.sg (H. Yang). Contents lists available at ScienceDirect Food Hydrocolloids journal homepage: www.elsevier.com/locate/foodhyd https://doi.org/10.1016/j.foodhyd.2022.107691 Received 12 October 2021; Received in revised form 7 February 2022; Accepted 28 March 2022