Abstract
The aim of this study was to compare the physicochemical, rheological, and morphological characteristics of corn, nixtamalized flour, masa, and tortillas from the traditional nixtamalization process (TNP) and the extrusion nixtamalization process (ENP) and their relationship with starch. The traditional and extrusion processes were carried out using the same variety of corn. From both processes, samples of ground corn, nixtamalized flour, masa, and tortillas were obtained. The extrusion process produced corn flour with particle sizes smaller (particle size index, PSI = 51) than that of flour produced by the traditional nixtamalization process (PSI = 44). Masa from the TNP showed higher modulus of elasticity (G′) and viscosity (G″) values than that off masa from the ENP. Furthermore, in a temperature sweep test, masa from the TNP showed a peak in G′ and G″, while the masa from the ENP did not display these peaks. The ENP-produced tortillas had higher resistant starch contents and comparable firmness and rollability to those from the TNP but lower quality parameter values. A comparison of the products' physicochemical properties obtained by the two processes shows the importance of controlling the damage to starch during the milling and extrusion processes to obtain tortillas of better quality. For the first time, we propose the measurement of the viscoelastic parameters G′ and G″ in temperature sweep mode to monitor changes in the degree of starch damage.
Highlights
Adapting the extrusion nixtamalization process (ENP) to obtain different quality nixtamalized products leads to technological limitations, since unlike wet milling, dry milling conditions used in ENP such as low water content and a reduced amount of lime, affect directly the behavior of corn starch, due to exhaustive mechanical force applied several times caused higher damaged starch contents [5,6,7, 19] and increase the content of starch damaged (SD)
The physicochemical, rheological, and morphological characteristics of products from the traditional and extrusion nixtamalization processes were different from the nixtamalization extrusion process. is may be the reason that there is more damage in corn starch in EPN than traditional nixtamalization process (TNP)
Corn flour from the TNP had lower Particle Size Index (PSI), and resistant starch but higher water absorption capacity than flour from the ENP. e viscoelastic parameters ὔ and ὔὔ as a function of frequency were higher in masa from the TNP than masa from the ENP
Summary
In the traditional nixtamalization process (TNP), wet milling is used to separate the starch granules with excess of water, which reduces the damaged starch content [4,5,6,7] Both factors, moisture content and particle size, make gradual starch gelatinization possible, improving the viscoelastic behavior of the obtained masa, as well as the flexibility, rollability, firmness, structural uniformity, color, and shelf life of the tortillas; the sensory attributes are appreciated by the consumer. Some studies of extrusion nixtamalization process (ENP) for obtaining nixtamalized corn flours, have evaluated the impact of the process conditions (temperature, moisture content, and calcium hydroxide, and enzymes in the feeding, screw speed, among others) in the physical and chemical properties of flour, masa, and tortilla, with good approaches to the traditional product [6, 7, 10,11,12,13,14,15,16,17,18]. Adapting the ENP to obtain different quality nixtamalized products leads to technological limitations, since unlike wet milling, dry milling conditions used in ENP such as low water content and a reduced amount of lime, affect directly the behavior of corn starch, due to exhaustive mechanical force applied several times caused higher damaged starch contents [5,6,7, 19] and increase the content of starch damaged (SD)
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