ARTICLE Characterization of alkaline-cooked quality protein maize as raw material for noodle processing Marie Anna Dominique R. Bibat, Olivia M. del Rosario, Lotis E. Mopera, Lilia S. Collado, and Floirendo P. Flores* Institute of Food Science and Technology, University of the Philippines Los Baños, College, Laguna 4031 Philippines uality protein maize (QPM) possesses high trypto- INTRODUCTION phan and lysine contents and may be processed into food products with improved protein content. Alka- Alkaline cooking or nixtamalization is a common method in Q line cooking enhances the functional and nutritional processing tortillas, tamales, tortillas, and pozole from corn properties of corn and can be employed as an inter- (Méndez-Montealvo et al. 2008). The interactions among the mediate step in processing corn products. In this study, we aimed maize components during the alkaline cooking and steeping to evaluate the textural, sensorial, and cooking characteristics of processes may influence the final characteristics of the processed noodles prepared from two white QPM varieties (SWQ 11 and products from the masa. Alkaline cooking promotes total gelati- SWQ 15) with different kernel characteristics. The QPM varie- nization of the external layers of the starch granule and the par- ties had different starch, protein, fiber, and fat contents. The tial gelatinization of the inner layers of the endosperm (Cornejo- QPM varieties were nixtamalized and the resulting masa was Villegas et al. 2013). Proteins surrounding the starch granules used for noodle production. The QPM noodles had lower cook- are solubilized during alkaline cooking and allow the release of ing yields (2.5%) than yellow alkaline noodles (YAN) from starch (Rodríguez-Miranda et al. 2011). However, the steeping wheat (3.8%) and corn starch noodles (CSN) (5%). Cooking loss process may inhibit amylose release and promote cross-linking. of the SWQ 11 noodles (3.9 %) was lower than SWQ 15 noodles The calcium content increases and lipids are saponified (Guzmán (6.8 %) and YAN (6.9 %). CSN had the greatest cooking loss et al. 2011, Mondragón et al. 2004a). Calcium directly affects (15%). Among texture parameters, hardness and cutting stress the gelatinization temperature as it binds with the hydroxy values of the QPM noodles (7 kgf and 0.6-1.4 kgf, respectively) groups in the starch molecule that ionize at high pH values were greater than YAN (4 kgf, and <0.1 kgf, respectively), but (Bryant and Hamaker 1997). Lime solution used in nixtamaliza- gumminess and cohesiveness values were equivalent. Sensory tion may also promote calcium-protein and protein-calcium- characteristics showed that the QPM noodles had similar flavor protein interactions and increase the thermal resistance of pro- absorbance as the control, but YAN and CSN were still pre- teins (Guzmán et al. 2011). Further, it was found that the swell- ferred. Amylose content significantly influenced the properties ing power, solubility, and degree of gelatinization increased at of the noodles. The cooking properties of the corn noodles were low lime concentrations (Mondragón et al. 2004a). Other alkali satisfactory, but the sensory attributes could still be improved. sources may be used, as long as the resulting masa is sufficiently The results of this study can be used to diversify the food use of cohesive to allow sheeting and shaping (Guzmán et al. 2009, QPM. Ruiz-Gutiérrez et al. 2012). Amylose, amylopectin, and proteins form a cohesive system that links the non-gelatinized starch and the endosperm in the resulting masa (Guzmán et al. 2009). It was *Corresponding author theorized that amylose-lipid complexes form during cooking and Email Address: [email protected] are reorganized during steeping (Mondragón et al. 2004b). Over- Submitted: July 29, 2014 all, alkaline cooking improves the protein quality of corn, in- Revised: November 24, 2014 Accepted: November 26, 2014 KEYWORDS Published: December 15, 2014 noodles, alkaline cooking, nixtamalization, quality protein Guest Editor: Maria Leonora dL. Francisco maize, food texture, sensory evaluation 413 Philippine Science Letters Vol. 7 | No. 2 | 2014 creases calcium content and niacin bioavailability, and may even Starch content be used to develop other food products, such as extruded snacks Undamaged and intact corn kernels were soaked in distilled (Rodríguez-Miranda et al. 2011). water for 2−3 h or until the hull could be easily peeled off manu- ally. Degermed and dehulled corn samples were blended for The Philippines utilizes a large amount of corn for process- 0.5−1 min using a commercial food grinder (Shimono Technol- ing. Data from 2002-2012 showed the country imported 127 ogy Electronic Co., Ltd, Anhui, China). The ground sample (0.1 thousand metric tons (MT)/y. Approximately 838 thousand MT/ g) was placed in a centrifuge tube and 5 mL of distilled water y were processed, resulting in an average per capita utilization of were added and vortexed to disperse the residue. Perchloric acid 16.1 kg/y (DA-BAS 2014). In some areas, more maize is con- (6.5 mL, 52% v/v, Univar, Ajax Finechem Pty., Ltd, NSW, Aus- sumed than rice, and corn varieties with higher nutritive and tralia) was then added. The solution was placed in an ice bath for better eating qualities are desired. Clark et al. (1977) reported 30 min and stirred continuously for 5 min and occasionally that lysine and tryptophan are the two limiting amino acids in the thereafter for 15 min. Distilled water (20 mL) was added and the maize endosperm. Hence, diets rich in corn need to be supple- solution was centrifuged at 2000 rpm for 10 min. After centrifu- mented with other protein sources. Compared to other types of gation, the supernatant was decanted. The solid residue was re- corn, quality protein maize (QPM) varieties contain twice as extracted as described previously. The collected supernatant flu- much tryptophan and lysine, and thus possess improved protein ids were pooled in a 100-mL volumetric flask and diluted to content (Prasanna et al. 2001). Further, the leucine:isoleucine mark with distilled water. The sample was then filtered through ratio is improved, which increases niacin bioavailability (Clark sintered glass. et al. 1977). An aliquot (0.5 mL) of the extract was combined with 2 mL Corn is employed in manufacturing local noodles called distilled water in a borosilicate test tube. The solution was “bihon”, which are produced mostly from corn starch. Corn sam- cooled in an ice bath and combined with 5 mL of cold anthrone ples that contain 27−28% amylose yield the best noodles (Tam et reagent (HiMedia Lab., Pvt., Ltd., Mumbai, India). The sample al. 2004). Structurally, corn-based noodles differ texturally from was mixed well, covered with marbles, and placed in a boiling wheat noodles because corn proteins are hydrophobic, whereas water bath for 7.5 min. The solution was cooled to 25 ºC before wheat proteins are hydrophilic. However, zein-starch dough was the absorbance was measured at a λ of 630 nm using a spectro- found to exhibit significant viscoelasticity at 60 °C, above the photometer (Spectronic 20, Milton Roy Company, Rochester, glass transition temperature of zein (Lawton 1992), and may NY). A standard curve was prepared with glucose (Mallinckrodt yield noodles of comparable quality to wheat. Waniska et al. Chemical Works, St. Louis, MO) and perchloric acid (6.76% v/ (1999) were able to produce corn-based noodles by extruding v) as blank. Glucose and starch content (in percent) were calcu- corn flour heated to 90 ºC and corn meal to 95 ºC. The process lated as follows: variables during alkaline cooking (such as cook time, tempera- ture, steeping time, and alkali concentration) may be modified to manufacture products of different textural attributes (Guzmán et al. 2011, Méndez-Montealvo et al. 2008, Rodríguez-Miranda et al. 2011, Sahai et al. 2001). This study explored the suitability of alkaline cooking as a preparatory step in noodle processing, and aimed to evaluate the cooking and eating quality attributes of the QPM noodles. Apparent amylose content The extraction procedure was adapted from Tam et al. MATERIALS AND METHODS (2004) with some modifications. The kernels (200 g) were soaked in 0.45% (m/v) sodium metabisulfite (JT Baker Chem. The QPM used in this study were open-pollinated varieties Co., Phillipsburg, NJ) solution acidified with 0.5% (m/v) lactic cultivated by the Institute of Plant Breeding, University of the acid (Univar, Ajax Finechem Pty., Ltd, NSW, Australia) and Philippines Baños. Two white QPM cultivars (SWQ 11 and incubated at 52 ºC for 36 h. The soaked kernels were drained, SWQ 15) with different endosperm hardness values (60% and blended at medium speed for 1 min with an equal volume of 88%, respectively) measured by floatation technique and distilled water in a Waring blender, and strained through a coarse grit:germ ratios (5.5 and 4.7, respectively) were used. All chemi- 20-mesh sieve (850 μm) to collect the starch milk. The residue cals used were reagent-grade. was re-extracted and the combined starch milk was filtered using a 100-mesh sieve (75 μm). The starch suspension was washed Kernel characteristics repeatedly with distilled water until both residue and supernatant Proximate analysis were clean. The starch particles were air-dried at room tempera- Standard methods of analysis from the Association of Offi- ture, ground using a mortar and pestle, passed through a 60-mesh cial Analytical Chemists (AOAC 2000) were used to determine sieve (250 μm), and kept in polyethylene bags at −20 ºC prior to moisture content (Method Number: 925.10), ash (Method Num- use. ber: 923.03), fat (Method Number: 920.39C), crude fiber (Method Number: 962.09), and protein (Method Number: The method previously presented by Juliano (1971) and 920.87). modified by Han et al.