Effect of processing conditions on the production of nixtamalized corn flours by the traditional method

Figures & data

Table 1 Independent variables (coded and uncoded) and factor levels for full factorial design 2 ^k .Variables independientes (codificadas y no codificadas) y niveles de variación para el diseńo factorial completo 2^k.

Uncoded variables or factors	Coded variables or factors	Factor levels
		–1	0	+1
Cooking temperature (^°C)	A	72	82	92
Cooking time (min)	B	25	45	65
Steeping time (h)	C	3	7	11

Figure 1. Effect of cooking temperature, cooking time, and steeping time on a) the residual calcium concentration, b) yield, and c) energy consumption in nixtamalized corn flour prepared by using the traditional method.Efecto de la temperatura de cocción, el tiempo de cocción y el tiempo de reposo en a) la concentración de calcio residual, b) rendimiento y c) consumo de energía en harina de maíz nixtamalizado elaborada empleando el método tradicional.

Table 2 Analysis of variance (ANOVA) and regression coefficients of response variables for (independent variables) factors.Análisis de varianza (ANOVA) y coeficientes de regresión para las variables de respuesta correspondientes a las variables independientes estudiadas.

	Calcium (mg/g)		Yield (g)		Energy consumption (kWh/kg)
Term	Coefficient	p-value	Coefficient	p-value	Coefficient	p-value
β0	1.576^a	0.000	54.05^a	0.000	1.638^a	0.000
β1	0.165^a	0.000	14.93^a	0.000	−0.233^a	0.000
β2	0.008^ns	0.594	1.835^a	0.000	−0.088^a	0.000
β3	0.078^a	0.000	13.77^a	0.000	−0.175^a	0.000
β11	−0.075^a	0.001	−1.007^a	0.006	0.028^ns	0.123
β22	−0.113^a	0.000	−0.534^ns	0.091	0.090^a	0.000
β33	−0.008^ns	0.594	−0.180^ns	0.540	0.005^ns	0.741
β123	−0.021^ns	0.171	−0.920^ns	0.010	−0.015^ns	0.369
R ^2	97.89		99.84		97.71
R ^2-adj	96.02		99.69		95.67
Note: βo= Regression coefficient; βi = Lineal coefficient; βii = Quadratics coefficient; and βij = Interaction coefficients; ^ns Not significant term (p > 0.05); ^aSignificant term (p < 0.05).

Table 3 Mathematical models for response variables.Modelos matemáticos par a las variables de respuesta.

Response variables	R ^2	Equations
Calcium (g/100g)	97.89	−2.28 + 0.004A + 0.016C – 1.867^−5 A.B – 1.598^−4 A.C
Yield (g)	99.84	−93.905 + 145A – 0.139B + 0.395C + 0.003A.B – 0.001A.B.C
Energy consumption (kWh/kg)	97.71	6.40–0.052A – 0.028B – 3.05C + 0.003A.C

Figure 2. Predictions of the experimental design for calcium content in nixtamalized corn flour prepared by the traditional method and maximum response at the central point.Predicciones para el modelo experimental correspondiente al contenido de calcio en harina de maíz nixtamalizado empleando el método tradicional y la respuesta máxima en el punto central.

Figure 3. Particle size analysis of instant corn flour CICF, TICFC, and TICFWC.Análisis del tamańo de partículas en harina de maíz instantánea CICF,TICF y TICFWC.

Table 4 Chemical proximate analysis of instant corn flours (g/kg of dry matter).Análisis químico proximal de las harinas instantáneas (g/kg de materia seca).

Samples	Moisture	Crude protein	Ether extract	Crude fiber	Ash	NFE
CICF	95.7 ± 6.4^a	82.1 ± 1.7^a	30.6 ± 1.6^a	41.4 ± 8.2^a	10.2 ± 1.3^a	748.5 ± 4.3^b
TICFC	92.2 ± 1.9^a	86.3 ± 4.3^a	28.7 ± 3.2^a	30.7 ± 2.9^b	18.0 ± 2.4^b	737.0 ± 2.6^a
TICFWC	93.1 ± 2.5^a	86.6 ± 4.2^a	28.4 ± 7.2^a	39.2 ± 3.4^a	11.6 ± 1.1^b	741.5 ± 2.5^a
Notes: CICF = Commercial instant corn flour; TICFC = Traditional instant corn flour with calcium; TICFWC = Traditional instant corn flour without calcium; and NFE = Nitrogen free extract. This value was calculated by the addition of moisture, crude protein, ether extract, crude fiber, ash, and the difference to 1000; Assays were performed in triplicate. Mean ± SD values followed by the same letter in each column are not significantly different (p < 0.05).

Figure 4. Micrographs of the morphology of instant corn flour (a) CICF, (b) TICFC, and (c) TICFWC.Micrografías de la morfología de harina de maíz instantánea (a) CICF, (b) TICFC, and (c) TICFWC.