Soy Leghemoglobin: A review of its structure, production, safety aspects, and food applications

Leghemoglobin (LegH) protein from soy (Glycine max) has recently gained attention for its various applications, including serving as a cellular oxygen carrier, providing bioavailable iron, and acting as a food-grade coloring and flavoring agent. Currently, the food industry is facing a major challenge in creating meat analogs that can replicate the texture, flavor, and mouthfeel of meat. In this context, soy LegH production using Pichia pastoris has emerged as a promising option to enhance the flavor and color of meat analogs to meet the growing demand of consumers. This paper focuses on the structure and production stages of LegH preparation including production strain (Pichia pastoris), up-regulation of the heme biosynthetic pathway, and fermentation, recovery and stability processes of LegH. Then the safety aspects and food applications of soy LegH as a flavoring and coloring agent as well as the nutrient content and dietary intake are reviewed. Lastly, the market forecast, conclusion and future trends such as novel strategies to improve biosynthesis and large-scale production of LegH are also highlighted. Although several scientific papers published on various aspects of soy LegH, it remains an area of limited exploration. The efforts of developing meat analogs with enhanced flavor and aroma profile, as well as enriching them with coloring and nutrient contents of LegH should be extended. Through biological pathways, it may be possible to develop high-yield and non-toxic processes for maximizing LegH production. There is also a need to increase LegH production and applications in microbial hosts.