Genetic material

The amaranth genotypes used were experimental lines called opaca and cristalina (Amaranthus hypochondriacus), which were provided by the amaranth improvement program of CEVAMEX-INIFAP. The bread wheat varieties Fuertemayo F2016 and Urbina S2007 were used to make bread and cookies, respectively, both varieties were provided by the wheat improvement program of CEVAMEX-INIFAP and released for irrigation conditions. Fuertemayo F2016 is characterized by presenting average values of pearling index of 48%, so it was classified as semi-hard grain, for the strength of its dough of 350 x 10^-4 J it was classified as strong, while for its tenacity-extensibility ratio, PL= 1.1, it was classified as balanced.

So, the Fuertemayo F2016 variety is suitable for the mechanized bakery industry and can be used to improve mixtures with weak dough flours. On the other hand, the Urbina S2017 variety was classified as soft grain for its pearling index close to 60% and for its W less than 200 x10^-4 J and its PL less than 1 is considered as weak-extensible dough, so it is suitable for making cookies and can also be used as an improver of wheats with strong and tenacious gluten.

Obtaining flours and mixtures

The flours were obtained in the wheat quality laboratory of CEVAMEX-INIFAP. To obtain the whole flour of opaca (WFOA) and cristalina (WFCA) amaranth, the raw grain was ground in a UDY-type mill using a 0.5 mm mesh to obtain some flour with homogeneous particle size. To obtain the refined wheat flour (RWF), the milling was carried out in a Bhuler mill (Brabender OHG, Germany) according to method 26-31 of the ^{AACC (2005)}. The grain was conditioned by adding water to the grain according to the hardness and initial moisture of the grain, left to stand for 24 h and subjected to grinding. The flour produced by the grinding was sifted in a 10xx mesh to obtain the refined flour.

The mixtures to analyze the baking quality were: 100% RWF, 5% WFCA/95% RWF, 10% WFCA/90% RWF, 15% WFCA/85% RWF, 5% WFOA/95% RWF, 10% WFOA/90% RWF and 15% WFOA/85% RWF. On the other hand, the mixtures to evaluate the cookie quality were: 100% RWF, 25% WFCA/75% RWF, 50% WFCA/50% RWF, 75% WFCA/25% RWF, 100% WFCA, 25% WFOA/75% RWF, 50% WFOA/50% RWF, 75% WFOA/25% RWF, 100% WFOA.

In the case of the mixtures used to make the bread, it was possible to determine alveograph variables due to their low percentages of whole amaranth flour. These alveograph variables were the strength (W), tenacity (P), extensibility (L) and the tenacity-extensibility ratio (PL) of the dough, which were calculated from the alveogram, which was obtained from 60 g of the flour mixture using Chopin’s Alveograph (Tripette & Renaud, France) using the method 54-30A of the ^{AACC (2005)}.

In the case of the mixtures for making the cookies, due to the high percentages of whole amaranth flour incorporated, it was not possible to determine the alveograph variables of the doughs and it was decided to determine mixograph variables. The mixograph variables measured were kneading time (min), kneading stability (min) and mixogram height (mm), which were estimated by the mixograph (National Manufacturing Co., Lincoln, NE) using the method 54-40A of the ^{AACC (2005)} in samples of 10 g of the mixture.

Baking quality was measured as volume of bread (ml) by the straight-dough method (method 10-09, AACC, 2005) from 100 g of the mixture and determined on a volutometer by displacement of rapeseed (Brassica campestris L.). Additionally, the weight of bread (g), color of the crumb and structure of the crumb were determined. The cookie quality estimated as a cookie factor was determined using the method 10-54 (^{AACC, 2005}). The dough was laminated to 0.9 cm thick and molded with a diameter of 5.5 cm then baked for 25 min at 220 °C.

The cookie factor was determined using five cookies, homogeneous in terms of size and shape, the diameter of each one and its height were measured with a vernier. The cookie factor was calculated using the formula W/L where: W= sum of the averages of five diameters and L= height of the five cookies one above the other and the mixtures were classified based on: cookie factor, excellent= 5-6, very good= 4.5-4.9, good= 4-4.4, regular= 3.5-3.9 and not suitable <3.4. A triplicate analysis was performed for each mixture. With the measured variables, an analysis of variance was performed with the SAS statistical package and the Tukey test ≤0.05 was used to indicate the differences between the mixtures.

Alveograph variables and baking quality

Table 1 shows the averages of the variables of strength, tenacity, extensibility, and tenacity-extensibility ratio of the dough. The strength of the dough ranged from 193.3 to 434.3 x 10^-4 J. The highest value was shown by the sample of 100% refined wheat flour corresponding to the Fuertemayo F2016 variety, which was classified as strong dough for its value greater than 300 x 10^-4 J; while the mixture with 15% whole flour of cristalina amaranth was associated with the lowest value, in this way, for its value less than 200 x 10^-4 J, it was classified as a weak dough. The rest of the mixtures were classified as medium strong dough for their values between 200 and 300 x 10^-4 J.

Based on the above, it is observed that, as the percentage of whole flour of cristalina or opaca amaranth increased, the strength of the dough decreased; nevertheless, it was observed that the decrease in strength was greater when whole flour of cristalina amaranth was added. This is consistent with ^{Vásquez-Lara et al. (2016}), who found that substituting quinoa flour by 2.5 to 10% in mixtures with wheat flour decreased the strength of the dough.

On the other hand, based on their tenacity-extensibility ratio (PL), all doughs were classified as tenacious for their values greater than 1.2. However, the highest values for PL were shown by combinations with percentages of 10 and 15 of whole flour of cristalina and opaca amaranth, respectively, with the highest (PL= 6.2) being for the mixture with 15% whole flour of opaca amaranth, the increase in PL is due to the increase in its tenacity (P) and decrease in its extensibility (L), since this mixture had the highest and lowest values for these variables (Table 1). While the lowest values for the tenacity-extensibility ratio were for combinations with 5% amaranth and for 100% refined wheat flour, which is due to their higher extensibility values.

In the specific case of extensibility, a general decrease was observed for all mixtures compared to 100% refined wheat flour. Based on the above, mixtures with whole flour of cristalina and opaca amaranth decrease the extensibility and strength of the dough, which is due to the presence of proteins and amaranth bran that do not allow the formation of the gluten network, which interferes with the optimal development of the dough. This is consistent with what was indicated by ^{Cotovanu and Mironeasa (2021}), who found similar results when replacing refined wheat flour with whole amaranth flour with different particle sizes and percentages of addition from 5 to 20%.

Table 2 shows the averages of the variables of bread volume, bread weight, crumb color and crumb structure. The bread volume of the mixtures varied from 485 to 700 ml; the difference is graphically represented in Figure 1. The highest value corresponded to the 100% refined flour of the control variety, followed by the mixture with 5% whole amaranth flour, which was the one that less decreased the volume of bread, the above is consistent with ^{Sanz-Penella et al. (2013}), who indicated that the proportion of the substitution of whole flour of Amaranthus cruentus can be up to 20 g per 100 g of wheat flour to maintain the quality of the cookie and take advantage of the nutritional value of amaranth.

The lowest values corresponded to combinations with 15% whole flour of opaca and cristalina amaranth. Most mixtures with whole flour of opaca and cristalina amaranth showed values less than 600 ml, which is consistent with ^{Ayo (2001}), who reported a decrease in the baking index for percentages of substitution of up to 50% with amaranth flour. However, combinations with whole flour of opaca amaranth of 5 and 10% exceeded in volume the same percentages with whole flour of cristalina amaranth.

Figure 1 Graphic representations of bread volume of mixtures of refined wheat flour (RWF) and whole amaranth flour, a) 700 ml (100% RWF); and b) 485 ml (15% WFOA/85% RWF). 

For the specific case of the mixture with the combination with 15% whole flour of opaca amaranth, it was associated with the lowest volume of bread, which is due to its higher value of tenacity (Table 1), which disfavors the volume of bread according to ^{Nash et al. (2006}), who indicated that the decrease in strength and extensibility, as well as the increase in tenacity decrease the volume of bread. On the other hand, ^{Miranda-Ramos et al. (2019}); ^{Cotovanu and Mironeasa (2021}) indicated that the presence of amaranth proteins hinders the gluten network and detract from the expression of bread volume. However, these authors also reported an increase in the concentration of protein, lipids, minerals, and fiber in bread products made with amaranth flour mixtures.

In general, the weight of bread increased as refined wheat flour was replaced with whole flour of opaca and cristalina amaranth. For the color of the crumb, the sample of 100% refined flour presented yellow-cream color, while for the rest of the mixtures, they presented brown and dark color. In the case of the crumb structure, it was regular for 100% refined wheat flour, as well as mixtures with 5% whole flour of opaca and cristalina amaranth, the rest of the combinations showed poor crumb structure (Table 2). The coloration and structure of the crumb was modified due to the presence of amaranth bran and flour, the above agrees with what was indicated by ^{Álvarez-Jubete et al. (2010}), who reported its darkening due to the presence of amaranth and quinoa flour. Likewise, ^{Coțovanu and Mironeasa (2021}) indicated that the crust of bread enriched with chia presented dark coloration. Figure 2 graphically presents the cream-yellow color of the crumb and the type of crumb found in some mixtures analyzed.

Figure 2 Graphic representation of the color and structure of the crumb, a) yellow-cream color and regular (100% RWF); and b) brown color and poor (15% WFOA/85% RWF). 

Mixograph variables and cookie quality

Table 3 shows the averages for the kneading variables obtained from the mixogram of the different mixtures. Kneading times ranged from 1 to 3 min. The sample of 100% refined flour of the control variety Urbina S2007 presented a value of 1.6 min of kneading, characteristic of weak dough. In general, the substitution of refined flour for whole flour of cristalina amaranth decreased the kneading time. However, the sample with 100 and 75% whole flour of opaca amaranth increased the kneading time.

On the other hand, the height of the mixogram is associated with the concentration of protein in refined wheat flour, in such a way that the sample with the highest value corresponded to 100% refined flour and by decreasing its percentage of wheat flour in the different mixtures, it generally reduced the height of the mixogram. Osella et al. (2008) indicated that low strength values indicated by short kneading times favor cookie quality measured as cookie factor. This is corroborated by what was found in this study since mixtures 75 and 25% whole flour of cristalina amaranth with short kneading times were associated with high values of cookie factor, while the samples 100% and 75% opaca amaranth flour with longer kneading times showed the lowest cookie factors.

Table 4 presents the averages of the variable of cookie factor, which varied from 4.5 to 5.8, in this way all mixtures were classified as very good to excellent based on their cookie factor. Figure 3 graphically represents the cookie factor. Most of the mixtures were classified as excellent for their value greater than 5, except for the combination with 75% whole flour of opaca amaranth and the sample of 100% whole flour of opaca amaranth, which were classified as very good for their values of 4.7 and 4.5, respectively.

It is important to indicate that these samples presented the highest values of kneading time, which is indicative that the strength increased and therefore the cookie factor decreased, which agrees with Duyvejonck et al. (2012), who reported that the greater strength of the dough is negatively related to the diameter of the cookie and consequently to the cookie factor. On the other hand, it was identified that the combinations with 25% whole flour of opaca and cristalina amaranth, as well as that of 75% whole flour of cristalina amaranth exceeded the rest of the combinations and the control variety in cookie quality. This contradicts what was indicated by ^{Sindhuja et al. (2005}), who reported a decrease in the cookie factor with substitution of 10 to 35% Amaranthus gangeticus flour.

Figure 3 Graphic representations of the cookie factor of mixtures of refined wheat flour (RWF) and whole amaranth flour, a) 4.5 (100% WFOA); and b) 5.8 (25% WFOA/75% RWF). 

However, this may be due to the different species of amaranth used in the preparation of cookies. On the other hand, ^{Man et al. (2017}) agrees with our results since they found that the incorporation of amaranth flour favored the cookie factor and increased the protein and fiber contents. Based on the above, the substitution of whole flour of opaca and cristalina amaranth in the production of cookies maintained the cookie factor and even improved it, which consequently maintains the cookie yield that is commercially reflected in the number of cookies per unit of flour used.