INTRODUCTIONIn recent years, snack foods have gained importanceand popularity worldwide and become part of modernfood culture. However, they have a low nutritionalvalue due to high carbohydrate and fat contents and alow protein content [1]. Moreover, the dependence onconvenience snacks has exposed consumers to a higherrisk of obesity, cardio-vascular disease, and cancer [2].Recently, with the revolution in food marketing and theconsumer trend towards healthier low sodium, low oil,and low calorie foods, it is necessary to develop newproducts that offer quality, variety, cost-efficiency,convenience, and nutritive value [3].The current trend in the food industry is to developmore nutritive snack foods, rather than eliminatesnacks from the diet, largely due to their economicvalue [1]. Snacks has become very popular all over theworld, especially among children [4]. Tortilla chipsand corn chips are the most popular corn-based snackproducts. Corn chips are fried products made fromcorn flour, while tortilla chips are Mexican corn snackstraditionally manufactured from nixtamalized corngrains with or without frying [5]. The resulting snacks,even fried after baking, have a lower oil content, firmertexture, and a stronger alkaline flavor compared tocorn chips. They are convenient, ready-to eat, andinexpensive corn products with digestive and dietaryprinciples of vital importance [6].Nixtamalization is a process that involves alkalinecooking and steeping of corn kernels, which arethen washed and ground to produce masa (soft andmoist dough). Corn masa is kneaded and molded, andthen baked on a hot griddle for tortilla chips [7−8].Nixtamalization provides nutritional, technological, and safety benefits to corn grains. The nutritional benefitsinclude improved protein quality, increased calciumand B-vitamins availability, and reduced phytic acidand tannins contents [9]. Technologically, nixtamalizedgrains are more easily ground due to softer pericarp andendosperm, with gelatinized starch and improved aroma.In addition, nixtamalization reduces mycotoxin contentsin corn grains [10].Maize is a vital crop for both human food andlivestock feed, and the demand for maize and itsproducts grows day by day due to its versatile uses,including medicine, textile, and biofuel production[11−12]. By 2025, maize will be the most common cropproduced all over the world [13]. Water and productiveland limitation leads plant breeders to vertical expansionthrough improving the efficiency of water use andincreasing unit area productivity [14−15].In this regard, maize production programs arecontinuously trying to increase yield, quality, andstability under water deficit conditions [16]. While grainyield is a commonly investigated parameter, qualityand technological parameters have less attention [17].Therefore, we aimed to investigate the possibility ofusing nixtamalized corn flours – obtained from the bestyellow corn hybrids based on grain yield under droughtconditions – in baked corn snacks production.STUDY OBJECTS AND METHODSRaw materials. For this study, we used materialsplanted under normal and water stress (drought)conditions in the Experimental Farm of AgriculturalResearch Centre (ARC), Delta region, EL-KalyubiaGovernorate, Egypt. We selected six of the best yellowmaize crosses (Y ̶Y6) according to their superiorityin grain yield under drought conditions in the fieldexperiment (yield and irrigation data publishedin Esmail et al.) [14]. They were obtained fromhybridization between the imported CIMMYET parentallines following the half-diallel crossing system. Singlecross Giza 178 was used as a chick variety. Chemicalsand other ingredients for ready-made snacks productionwere purchased from the local market.Chemical composition. Moisture, ash, fiber, protein,and fat contents in corn hybrids were determined bymethods recommended by the Association of OfficialAnalytical Chemists [18]. Total carbohydrates werecalculated by difference.Preparation of nixtamalized corn flour.Nixtamalized corn flour was prepared according tothe method of Quintanar-Guzman et al. with somemodification [19]. In particular, corn kernels wereboiled in a 1% calcium hydroxide solution (percentby grain weight) for 2 h, soaked in boiled water for14 h, and washed with excess tap water followed bydecantation using a sieve. The washed nixtamalizedgrains were dried for 8−10 h at 60°C and then cooledto 25°C. The dried grains were milled in an analyticalmill (Brabender mill, Junior) to pass a 60 meshscreen (0.0028 in sieve opening), and a minimum of0.102 ± 0.06 cm of free space between the shaft and thestationary body of the mill. The masa prepared fromgrains was packed in polyethylene bags and stored in arefrigerator (4°C) until use.X-ray diffraction. Starch crystallinity wasevaluated by X-ray diffraction patterns of the samplesusing monochromatic CuK radiation on a PhilipsX-ray diffract meter at 35 kv and 15 mA (Central Lab,National Research Centre, Egypt). Lyophilized sampleswere placed on the l cm2 surface of a glass slide andequilibrated overnight at * a relafive humidity of 91%and run at 2–32 θ (diffraction angle 2 θ). The spacingwas computed according to Bragg’s law [20].Pasting properties of flours. Pasting propertiesof nixtamalized corn flours were determined using arapid visco analyzer starch master R&D pack V 3.0(Newport Scientific Narrabeen, Australia) according tothe methods approved by the American Association ofCereal Chemists [21]. The measured parameters werepasting temperature, peak viscosity, trough viscosity,final viscosity, breakdown and setback viscosity.Preparation of snacks. Snacks were preparedaccording to Agrahar-Murugkar et al. by mixing 100 gNCF and 3 g salt in a planetary mixer for 2 min at a lowspeed using a flat blade, then adding 15 mL sunflower oiland mixing for another 6 min [2]. After this, we changedthe mixer blade to a hook type, added 50 mL water,and mixed the dough for about 2 min at a low speed,followed by a medium speed for 2−4 min until soft,cohesive and pliable dough developed. The prepareddough was covered with wet muslin cloth and left torest for 5 min at room temperature. Then, we sheetedit manually, cut in a circular shape (1.50 mm thick) andbaked at 180°C for 8 min on one side and another 5 minon the other side. The chips were then dried for 1 h at70°C and cooled to room temperature.Color quality of processed snacks. The colorparameters of snacks were evaluated using a Huntercolor meter (Hunter Associates Lab Inc. (Model No:LabScan XE, USA). The instrument was calibratedwith a white standard tile of Hunter Lab color standard(LX N o. 1 6379): x = 7 7.26, y = 8 1.94 a nd z = 8 8.14(L* = 92.43, a* = −0.88, b* = 0.21). The results wereexpressed in accordance with the CIELAB system forL* (L* = 0 [black], L* = 100 [white]), a* (−a* = g reenness,+a* = redness), and b* (−b* = blueness, +b* = yellowness).In addition, the total color difference (ΔE)between the control snacks (made from SC178 plantedunder normal irrigation conditions) and those made fromcorn genotypes planted under drought conditions wascalculated as follows:ΔE = [(ΔL)2 + (Δa)2 + (Δb)2] 0.5Along with this, we calculated Hue angle, Chroma,and Browning Index (BI) using the following expression:394Yaseen A.A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 392–401Chroma = [(a*)2 + (b*)2] 0.5Hue angle = tan−1 (b*/a*)Browning Index (BI) =[100 (x − 0.31)]0.17Where, x =(a* + 1.75L*)(5.645L* + a* − 3.012b*)Sensory evaluation. Snacks were evaluated fortheir sensory characteristics by 15 trained panelists.The tested characteristics included color, flavor, taste,crispiness, appearance, and overall acceptability [22].Statistical analysis. The obtained data werestatistically analyzed using the SAS Systems forWindows software, version 6.12 TS020 (SAS, StatisticalAnalysis System, Institute Inc., Cary, NC, 1996). Weperformed analysis of variance (ANOVA) and the leastsignificant difference (LSD) test (P < 0.05) to determinesignificant differences between the treatment means.RESULTS AND DISCUSSIONChemical composition of yellow corn hybrids.The chemical composition of tested corn samplesplanted under normal irrigation and drought conditionsis presented in Table 1. We found significant genotypedifferences in moisture, protein, fat, fiber, ash, andcarbohydrates. The moisture contents of corn genotypesvaried in a narrow range from 11.33 to 12.70%. Wenoticed a slight decrement in moisture among all cornhybrids planted under drought conditions compared tonormal conditions. This decrement was insignificantin some genotypes (SC178, Y1, Y2, and Y5) andsignificant in others (Y3, Y4, and Y6). The proteincontent, however, varied in a wide range: its highestvalue (13.28%) was found in Y4 genotype plantedunder drought conditions and the lowest (9.52%), in Y6genotype planted under normal conditions. Also, thefat content varied from 4.28 to 5.50% for Y6 and Y2genotypes planted under normal conditions, respectively.Generally, we found that the corn genotypes plantedunder drought conditions had higher protein and fatcontents compared to those planted under normalconditions. Each genotype showed higher protein andfat contents under water stress conditions compared tonormal conditions. Carbohydrate contents, however,showed a reverse trend. Similar results were reportedby Barutcular et al. for maize and Rharrabti et al. forwheat [12, 23]. Mousavi et al. reported that water stress,especially during the flowering stage, affected thephotosynthesis process and thus greatly decreased thestarch content while increasing protein and fat contentsin the grains [24].The fiber contents of corn genotypes varied from2.95 to 3.30% for Y2 planted under water stress andSC178 planted under normal conditions, respectively.At the varietal level, there were no significantdifferences between the fiber contents of Y1, Y2, Y4,and Y5 genotypes under both irrigation conditions. Fibercontents of SC17 and Y6 genotypes showed a significantdecrement under drought conditions compared tonormal conditions. By contrast, Y3 genotype revealed asignificant increment in fiber under drought conditions.Regarding ash, we found that SC178 showed the highestTable 1 Chemical composition of yellow corn genotypes (% on dry weight basis)Genotype Moisture Protein Fat Fiber Ash CarbohydratesYellow corn hybrids planted under normal conditionsSC178 11.82BCD 10.15F 4.39F 3.30A 1.65A 80.51ABY1 11.95BC 9.75G 5.20B 3.12BC 1.44BC 80.49ABY2 11.09E 10.90CD 5.21B 3.19ABC 1.30D 79.40BCDY3 12.22AB 10.65DE 4.80D 2.98EF 1.31CD 80.26ABY4 12.70A 10.50EF 4.50EF 3.10CDE 1.26DE 80.64ABY5 11.70CD 10.51E 4.30F 3.20ABC 1.32CD 80.67ABY6 12.50A 9.52G 4.28F 3.29A 1.19DEF 81.72AYellow corn hybrids planted under drought conditionsSC178 11.50CDE 11.80B 4.90CD 3.10CDE 1.12F 79.08BCDY1 11.56CDE 10.78CDE 5.10BC 3.10CDE 1.49B 79.53BCDY2 11.51CDE 11.69B 5.50A 2.95F 1.19DEF 78.67CDY3 11.40DE 13.01A 4.50EF 3.17ABC 1.25DE 78.17CDY4 11.33DE 13.28A 4.70DE 3.20ABC 1.22DEF 77.60DY5 11.65CD 11.05C 4.79E 3.25AB 1.30D 79.61BCY6 11.59CDE 10.89CD 4.80E 3.03DEF 1.15EF 80.13ABCLSD 0.5103 0.3591 0.2536 0.1345 0.1397 1.9701SC178 = Single Cross Giza 178, Y1–Y6 = new yellow corn hybridsMeans with the same letters in the same column are not significantly different395Yaseen A.A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 392–401value (1.65%) under normal irrigation and the lowestvalue (1.12%) under drought conditions. However,there were no significant differences between the ashcontents of the six new genotypes under both irrigationconditions.The high protein and fat yielding genotypes andthe comparable fiber and ash contents under droughtconditions may be due to the drought tolerance of thenew hybrids. The chemical composition of yellowmaize (on a dry weight basis) was previously reportedby Watson as 71.7% starch, 9.5% protein, 4.3% fat,and 1.4% ash [25]. Compared to these data, all the corngenotypes in our study had high protein and fat contents.Similar values for these macronutrients were also foundamong 1245 corn samples from different locationsall over the world [26]. Also, the reported values formoisture and fat contents of yellow corn are close tothose reported by Yaseen et al. and Hussein et al.,being 12.50 and 5.15%, respectively [27, 28]. However,they reported lower values for crude protein (7.88%),ash (0.5%), crude fiber (2.5%), and total carbohydrates(76.0%).Starch crystallinity of yellow corn genotypes.The X-ray diffraction pattern diagrams for raw andnixtamalized corn samples are shown in Fig. 1a andB, respectively), and the respective crystallinities areillustrated in Fig. 1c. All raw corn genotypes plantedunder normal and drought conditions showed A-typediffraction peaks around 9.9, 5.8, 5.1 and 3.8 Å at 8.8°,15.0°, 17.4° and 22.9° (at 2θ), respectively. There were noclear differences between the diffractograms of yellowcorn genotypes.Similar results were previously reported in [29–32].They stated that X-ray diffractions of native cerealstarches showed pure “A” type peaks. In addition, Abd-Allah et al. mentioned that the calculated “d” spacingof yellow corn starch ranged between 5.4004 and3.4767 Å [29]. Also, they assumed that symmetric X-raydiffraction patterns of the tested samples could be dueto the fact that cereal starch is a homogeneous materialmainly composed of amylose and amylopectin. On theother hand, the specified diffracting angle (at 2θ) foreach peak in each starch type could be explained by themolecular weight and the amylose/amylopectin ratiovariations.As we can see in Fig. 1b, a diffraction peak at about4.4 Å was developed in the nixtamalized samples.It is also clear that the specified peaks in the NCFdiffractograms were characterized by decreasedintensity and broad background compared to thosein the raw samples (Fig. 1a). The peak at 4.4 is thefirst indication of a V-type amylose-lipid complexpattern [33].Arambula et al. revealed that an amylose–lipidcomplex developed as a result of starch gelatinizationduring extrusion or nixtamalization of corn flour [31].Besides, Mondragon et al. mentioned that amylose–lipidcomplexes might develop during alkali steeping [34].Finally, Agrahar-Murugkar et al. noted that the locationof this peak was slightly displaced from the strong 4.4 ÅFigure 1 X-ray diffraction diagrams for raw corn samples (a) and nixtamalized corn samples (b), and crystallinity values for rawcorn samples (c). NSC178 = Single Cross Giza 178 planted under normal conditions, DSC178 = Single Cross Giza 178 plantedunder drought conditions, Y1–Y6 = new yellow corn hybrids planted under drought conditions(a) (b) (c)396Yaseen A.A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 392–401to around 4.5–4.7 Å in the X-ray pattern of fried tortillachips [2].Beside the transition from pure “A” pattern in rawcorn flour to “A + V” pattern in NCF, the decreasedpeak intensity and its broad background indicatedthe transition from the semi-crystalline phase to theamorphous phase resulting in a partial disruption ofthe crystalline starch structure [31, 34]. As we can seein Fig. 1c, Y2 genotype had the highest crystallinityvalue (87.11%), followed by Y6 and Y4 genotypes(64 and 60%, respectively). Y3 genotype had a lowercrystallinity value (24.58%), with the lowest recorded forY5 (21%). In general, starch crystallinity in corn floursmay be affected by mechanical (milling process) andamylolytic activity, as it decreases with damage causedto starch granules [32, 35].Pasting properties of hybrid nixtamalized cornflour. The pasting properties of NCF dough wererheologically evaluated by a rapid visco analyzer (Table2). The results showed wide variations in peak viscosity,trough value, breakdown, final, and setback viscosity ofyellow corn hybrids planted under drought conditions.However, all corn hybrids showed the same peak time.For instance, the peak and final viscosity values rangedfrom 151 cp to 660 cp and from 250 cp to 1186 cp forY2 and Y3 genotypes, respectively. The trough value,breakdown and final viscosity ranged from 128 cp to 541cp, from 23 cp to 119 cp, and from 122 cp to 645 cp forthe same genotypes, respectively. All parameters weregreater for Y3 genotype, while Y2 genotype had lowerparameters.Pasting properties are measurements of starchbehavior (gelatinization and retrogradation) duringprocessing [36]. These properties could be affected bythe molecular structure of amylopectin (branch chainlength and distribution) [37] and the granule size [38].Amylopectin contributes to swelling and pasting ofstarch during heating. Amylose contributes to starchretrogradation during the cooling stage through itsaggregation by hydrogen bonds [39].It was indicated that the presence of lipids restrictsthe swelling of starch granules and amylose leaching,resulting in reduced viscosity of the corn flour pasteduring gelatinization, whereas amylose and lipids inhibitthe swelling [40, 41]. In our study, the lower viscosityvalues of Y2 hybrid could be due to its high fat content(Table 1) and a higher crystallinity degree (Fig. 1c).On the other hand, Sefa-Dedeh et al. reported a drasticreduction in the pasting properties of NCF compared toraw flour [9]. They attributed the reduction in viscosity,especially during the cooling stage, to the saturation ofhydroxyl groups on the starch molecules with calciumions (Ca2 ). The resulting Ca(OH) ions prevent anyfurther association of the starch molecules in the cookedpaste viscosity.Color attributes of corn snacks. The color ofnixtamalized corn flour-based products is an importantquality parameter which directly influences theconsumer’s acceptability of the product. Table 3 and Fig.2 show the color quality of snacks manufactured fromNCF of SC178 genotype planted under normal and waterstress conditions, as well as the new hybrids (Y1–Y6)planted under water stress conditions. We found a widerange of significant differences for all color parametersof the snacks: 61.58 ̶ 69.91, 3.35 ̶ 9.17 and 25.02–32.12for lightness (L*), redness (a*) and yellowness (b*),respectively.Noteworthily, the snacks produced from SC178genotype planted under normal irrigation conditionsshowed the lowest L* and the highest a* and b* values.The highest L* was recorded for snacks produced fromY1, while the lowest a* and b* values were recordedfor snacks produced from Y4 genotype. The totalcolor differences (ΔE), chroma (C*), hue angle (H*)and browning index (B.I.) varied between 8.23 ̶ 11.96,25.24 ̶ 33.40, 74.05 ̶ 83.32 and 47.36 ̶ 82.16, respectively.The snacks produced from corn hybrids plantedunder drought conditions tended to have higher L* andH* values and lower a*, b*, C* and BI values, comparedto those produced from SC178 planted under normalconditions. Similar previous studies stated that the colorof NCF ranged from white to dark yellow, depending onthe alkali concentration, processing conditions, and corntype [2, 42, 43]. In addition, Sefa-Dedeh et al. stated thatthe yellowish color in NCF-based products, even whenproduced from white corn, was closely related to theTable 2 Pasting properties of nixtamalized corn flourSample Peak Time, min Peak Viscosity, c.p. Trough, c.p. Breakdown, c.p. Final Viscosity, c.p. Setback, c.p.NSC178 7.0 535 430 93 932 502DSC178 7.0 569 471 98 952 481Y1 7.0 430 354 76 784 430Y2 6.9 151 128 23 250 122Y3 7.0 660 541 119 1186 645Y4 7.0 214 172 42 344 172Y5 7.0 577 482 95 980 498Y6 7.0 177 145 32 287 142NSC178 = Single Cross Giza 178 planted under normal conditions, DSC178 = Single Cross Giza 178 planted under drought conditions,Y1–Y6 = new yellow corn hybrids planted under drought conditions397Yaseen A.A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 392–401Table 3 Color attributes of snacks from drought-tolerant corn genotypesSamples Lightness (L*) Redness(a*)Yellowness(b*)Total colordifferences (ΔE)Chroma(C*)Hue angle(H*)Browningindex (B.I.)NSC178 61.58D 9.17A 32.12A 0.00E 33.40A 74.05D 82.16ADSC178 69.53AB 3.33G 28.45D 10.53B 28.64D 83.32A 54.75DY1 69.91A 3.82E 29.53C 10.23B 29.78C 82.63A 57.42CY2 69.03AB 4.99B 26.24F 10.37B 26.71F 79.24C 52.09EY3 66.93C 3.55F 27.26E 9.16C 27.49E 82.58A 54.85DY4 69.25AB 3.35G 25.02G 11.96A 25.24G 82.38A 47.36FY5 68.58B 4.88C 30.06B 8.46D 30.45B 80.78B 61.34BY6 66.37C 4.49D 27.34E 8.23D 27.71E 80.68B 56.74CLSD 1.1735 0.0859 0.4883 0.6242 0.4982 1.3986 1.0263NSC178 = Single Cross Giza 178 planted under normal conditions, DSC178 = Single Cross Giza 178 planted under drought conditions,Y1–Y6 = new yellow corn hybrids planted under drought conditionsFigure 2 Snacks processed from drought-tolerant corn genotypes. NSC178 = Single Cross Giza 178 planted under normalconditions, DSC178 = Single Cross Giza 178 planted under drought conditions, Y1–Y6 = new yellow corn hybrids plantedunder drought conditions398Yaseen A.A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 392–401lime concentration [9]. This observation could be due tothe varietal performance of yellow corn hybrids (yellowpigments content) under drought conditions.Browning index (BI) is the most important colorattribute in baked products because it affects theirfinal quality [44]. With respect to the yellow pigmentscontent, browning coloration could be due to bothenzymatic and non-enzymatic reactions. Duringnixtamalization, once cell walls and cellular membraneslose their integrity, enzymatic oxidation of phenoliccompounds rapidly takes place by polyphenolsoxidase [45]. However, the non-enzymatic Maillardreaction takes place between reducing sugars andproteins during the baking process.Sensory evaluation of corn snacks. The meanscores of sensory characteristics (Table 4) showedsignificant differences (P ≤ 0.05) between the genotypesfor color, crispiness, odor, taste, appearance, and overallacceptability. The snacks produced from SC178 plantedunder normal conditions and Y5 planted under droughtconditions were rated highest in all sensory attributes,while those produced from Y2 were rated lowest. As wesaid above, color is a very important quality parameterof baked products that reflects raw material formulationand processing.The brown-yellow color measured by the Hunterinstrument (Table 3) for the snack samples manufacturedfrom SC178 and Y5 NCF confirmed the results ofsensory analysis. The favorable taste and aroma of thesesamples could be due to the Millard reaction that takesplace during baking. In a similar work by Agrahar-Murugkar et al., nixtamalization improved the sensoryproperties of chips [2]. Further, in a study to identify themarket demand for corn-based snacks, Menis-Henriqueet al. found a need for snacks with a lower fat contentand a better nutritional value [46]. Therefore, we canconclude that nixtamalized corn flour is organolepticallysuperior and this technology could be used on acommercial scale.CONCLUSIONWe found that Y3 and Y5 genotypes grown underwater stress conditions provide corn grains with superiorquality that can be used in snack production. Also, wecan conclude that baked snacks made from nixtamalizedcorn flour are a healthy alternative to fried snacks.Finally, these findings could contribute to achieve bothfood and nutritional security, especially in water scarceareas.CONTRIBUTIONThe authors were equally involved in designing theresearch plan. Prof. Ramadan Esmail was involved in theproduction and cultivation of new yellow corn hybrids.Ahmed Hussein and Ayman Mohammad took part inthe production of NCF, as well as in the manufactureand evaluation of snacks. Attia Yaseen and AymanMohammad were involved in writing the manuscript,and Ayman Mohammad checked it for plagiarism.CONFLICT OF INTERESTThe authors declare no conflict of interest.