**1. Introduction**

Cereals, from the Latin word *'cerealis'* which means 'grain', comprise starchy grains from the grass family known as *Gramineae* [1]. They are a key component of the human diet and are the most widely used crop [2]. Some grains from this family are wheat, rice, maize, sorghum, millet, barley, and rye. Rice, wheat, and maize provide at least 30% of the food calories to more than 4.5 billion people in 94 developing countries [3]. Among them, maize (*Zea mays L*.) was the most produced crop in 2019 with 1,148,487,291 tons, compared to wheat and rice, with 765,769,635 and 755,473,800 tons, respectively [4]. Maize was domesticated in what is now Mexico approximately 7000 years ago and was spread across the world shortly after the European discovery of the Americas. Currently, the United States, Brazil, Mexico, Argentina, India, France, Indonesia, South Africa, and Italy produce 79% of the world's maize production [5].

In Mexico, maize is considered the most representative crop for its economic, social, and cultural importance [6, 7], with a production of 27,228,242 tons in 2019 [8], which places it as the eighth producer in the world [9]. Unlike the United States, where "yellow" corn is industrially produced to be used as animal feed or to make industrial corn derivatives ranging from sweeteners to plastics, in Mexico the vast majority of maize grown is "white" and it is destined for human consumption [10]. Most of the maize in Mexico is consumed as tortillas, being the basis of the daily diet [7].

There are different ways in which tortillas can be elaborated, traditionally nixtamalized maize is used [11]. The nixtamalization process consists on cooking the grains in an alkaline solution, followed by overnight steeping [6]. Afterwards, the maize is washed and stone ground to obtain a wet dough, known as *masa* [6, 12]. The *masa* can be used to prepare tortillas or to produce instant maize flour [12]. During this process, calcium is incorporated into the maize, the bioavailability of niacin (B3) improves, and mycotoxins' presence is reduced [12, 13].

The nutritional value of maize is affected by the variety, environment, and sowing conditions [14], and can also be modified after nixtamalization [15]. In general, maize is considered to be a source of vitamins (B-complex, A, C, and K), ß-carotene and selenium [2], but its protein content is considered to be of low nutritional quality as the concentration of lysine and tryptophan is low [14]. When compared to other cereals as wheat, oats, and rice, maize has a higher antioxidant capacity, attributed to a higher total phenolic content [13, 16]. The main component of tortillas are carbohydrates, mainly starch and fiber. While the protein, lipid and niacin (B3) content has been reported to increase after nixtamalization, phytochemicals like carotenoids, polyphenols, and anthocyanins can decrease [15].

Tortillas are an excellent vehicle to enhance nutrition options for maize consumers [17]. In fact, tortillas have been fortified with grasshopper (*Sphenarium purpuracens)* [18], nopal (*Opuntia ficus-indica*) [19], faba-bean (*Vicia faba*), white-bean (*Phaseolus vulgaris*), [14] and muicle (*Justicia spicigera* Schechtendal) [6], among others. With this additions, the mineral [18, 19], protein, [14, 18] and dietary fiber [14, 19] contents increased, as well as the antioxidant capacity [6].

In the last decades, seaweeds have gained attention as potential sources for the elaboration of food and feed products [20, 21]. Seaweeds are marine, photosynthetic algae that are prolific in every ocean. They are divided into three main classes, or phyla: *Phaeophyta* (brown algae), *Rhodophyta* (red algae), and *Chlorophyta* (green algae) [22]. Brown algae are a source of unsaturated fatty acids, alginate, biopolymers, and phlorotannins, which are polymeric structures of the monomer phloroglucinol [23]. *M. pyrifera* is a brown seaweed found in the Pacific Ocean, mainly used as feed for abalone and hydrocolloid production [20]. In this study, the seaweed *M. pyrifera* was used to partially substitute nixtamalized corn *masa* to elaborate functional tortillas, with an increased phenolic content and antioxidant activity. Therefore, the effect of incorporating different concentrations of seaweed into white maize tortillas in terms of chemical composition, color, texture, phenolic compounds, and antioxidant capacity was analyzed.
