## 1 Introduction  
Meat consumption has a long history in human evolution, likely going back to the earliest known human-like ancestor living 5-7 million years ago [1]. Environmental but also health and animal welfare concerns regarding conventional meat production and consumption are the main drivers for developing meat alternatives [2, 3, 4, 5]. To appeal to the largest consumer segment that is not committed to vegetarian or vegan diets, the food industry is placing extra emphasis on introducing meat alternatives to consumer markets. One of the aims is formulating plant-based products with similar sensorial (texture, color, flavor) [6, 7] and nutritional characteristics to conventional meat [7].  
Flavor and aroma are complex attributes of meat palatability. Cooking meat involves a series of reactions resulting in the development of various volatile compounds. These include Maillard reactions, lipid oxidation, interactions between Maillard reaction products and lipid oxidation products, and thiamine degradation [8]. Hundreds of volatile compounds result from these reactions, e.g., aldehydes, alcohols, carboxylic acids, ketones, pyrazines and esters. Saturated and unsaturated aldehydes, especially those containing 6-10 atoms of carbon, are a major contributor to the volatile profile and flavor development of cooked meat [9, 10]. Roast flavors in foods are usually associated with the presence of heterocyclic compounds such as pyrazines, thiazoles and oxazoles. In well-done grilled meat, pyrazines are reported to be the major class of volatiles [11].  
The inherent flavor and aromas of a meat product can be influenced by its lipid content [12] and pH [13], the diet, age and gender of the animal [14], and the presence of myoglobin [15]. Myoglobin is a globular heme protein found in muscles, capable of reversible oxygen binding via a heme-bound iron atom [16]. It is important for the sensory quality of meat and has been associated with a serum-like taste and metallic mouthfeel of beef [17]. The close relationship of heme proteins (hemoglobin and myoglobin) with lipid oxidation during cooking has been extensively studied [18; 19; 20]. Myoglobin has long been proposed to contribute to aroma development by catalyzing lipid oxidation reactions [21; 22]. Lipid oxidation products in turn promote myoglobin oxidation and alter its stability [23].  
Upon cooking, myoglobin unfolds, exposing the heme cofactor. The cofactor then catalyzes a series of reactions that transform amino acids, nucleotides, vitamins and sugars in the meat into a variety of flavor and aroma compounds characteristic of the complex aromatic profile of cooked meat. Consistent with the important role of heme iron in meat aroma, a plant heme protein, is now commercially used to optimize flavor in ground beef analogues intended to be cooked [24]. This heme protein, called Leghemoglobin, is originally found in the root nodules of leguminous plants.  
Some published studies assess the safety, toxicity, and allergy potential of plant heme-protein in plant-based meat alternatives [25; 26]. However, to our best knowledge, there is no publicly available data on the influence of myoglobin, the muscle heme protein, on the aromatic profile of meat alternatives. In the present proof-of-concept study, we used gas chromatography-mass spectrometry (GC-MS) to assess the effect of myoglobin on the formation of volatile compounds. The perspective here is to evaluate the potential of fermentation-derived, animal-free myoglobin as functional ingredient for plant-based meat alternatives. The information presented here could therefore be of value to plant-based food manufacturers interested in ameliorating the sensory properties of their products and formulating a product closer to conventional meat.