**2.1. Materials**

**1. Introduction**

102 Wastewater Treatment Engineering

been investigated.

for maize wastewater utilization are needed.

mer), and dietary fiber nature [9, 10, 14].

microstructural characteristics of the gels formed.

Nixtamalization is a process widely used in Mexico, the southern United States, Central America, Asia, and parts of Europe. This process consists of cooking maize grains in a lime solution, after soaking for 2–15 hours, the supernatant called maize wastewater or commonly known as "nejayote" is discarded [1, 2]. The remaining material is then ground to obtain nixtamal (dough or masa), used to prepare a variety of food products such as tortillas and related products [3]. A typical maize nixtamalization facility, processing 50 kg of maize every day, uses over 75 L of water per day and generates nearly the equivalent amount of alkaline wastewater on a daily basis [4]. Nejayote is considered an environmental pollutant because it is an alkaline wastewater, with high chemical and biological oxygen demand. The estimated monthly volume of nejayote generated in Mexico is about 1.2 m3 [1, 5, 6]. Thus, alternatives

Nejayote is rich in maize bran residues as during the nixtamalization process this tissue is removed from the maize kernel. Non-starch polysaccharides are major constituents of maize bran, 30% of which are ferulated arabinoxylans (AX) [2, 7, 8]. Therefore, nixtamalization degrades and solubilizes maize cell wall components, mainly AX, which can be recovered in maize wastewater [4]. Nixtamalization conditions such as cooking temperature, lime concen‐ tration, and soaking period could affect the structural and functional characteristics of AX but, to our knowledge, the effect of maize nixtamalization conditions on AX properties has not

AX are the main non-starchy polysaccharides of cereal grains, constituted of a linear backbone of β-(1→4)-linked D-xylopyranosyl units to which α-L-arabinofuranosyl substitu‐ ents are attached through O-2 and/or O-3. Some of the arabinose residues are ester linked on (O)-5 to FA (3-methoxy, 4 hydroxy cinnamic acid) [9, 10]. AX can form covalent gels by oxidation of FA resulting in the formation of dimers (di-FA) and trimers (tri-FA) of FA as covalent cross-linking structures [11]. AX gels are stabilized by covalent linkages, which make them stable to temperature, pH or ionic strength changes; these characteristics would allow their passage through the gastrointestinal tract being further fermented by colonic microflora [12, 13]. In addition, AX gels could have potential application as a microencap‐ sulation system for colon-specific delivery due to their porous structure (mesh size from 48 to 400 nm), high water absorption capacity (up to 100 g of water for gram of poly‐

The molecular features of AX depend on the source and the process extraction [10]. This characteristics as chemical structure, molecular weight and FA content affect their gelling ability and therefore functional properties of gels [11]. The purpose of this research was to extract AX from maize wastewater generated under two different maize nixtamalization conditions and investigate the polysaccharide gelling capability as well as the rheological and Nejayote was provided by two tortilla-making in Northern Mexico and used to extract AX. Laccase, which is copper-containing oxidase enzyme (benzenediol:oxygen oxidoreductase, E.C.1.10.3.2) extracted from *Trametes versicolor* and the other chemical products were pur‐ chased from Sigma Co. (St. Louis, MO, USA).
