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Food Chemistry 100 (2007) 1209–1216

FoodChemistry

Effects of processing on the nutraceutical profile of quinoa

Kevin Brady, Chi-Tang Ho, Robert T. Rosen, Shengmin Sang, Mukund V. Karwe *

Department of Food Science, Rutgers, The State University of New Jersey, 65 Dudley Road, New Brunswick, NJ 08901, USA

Received 18 March 2005; received in revised form 5 November 2005; accepted 1 December 2005

Abstract

Quinoa flour was subjected to a variety of thermal processes. Both unprocessed and processed quinoa samples were subjected to suc-cessive extractions in methanol and ethyl acetate solvents. Effects of processing were gauged via comparison of HPLC chromatograms ofthe quinoa extracts. Quinoa flour subjected to processing via roasting and extrusion resulted in a significant impact on the chemicalprofile when compared to unprocessed quinoa flour. Steam pre-conditioning had minimal effects on the chemical profile of quinoa flour.Process-enhanced isolate from roasted and extruded quinoa possessed a molecular weight of 480 D, was dissolved in methanol and ethylacetate, and possessed a NMR spectra reminiscent of a terpenoid compound. This research suggests that thermal processing ofquinoa flour can result in degradation of saponin molecules. Saponin decomposition may influence sensory or pharmacologicalproperties.� 2005 Elsevier Ltd. All rights reserved.

Keywords: Quinoa; Chenopodium quinoa; Roasting; Processing; Extrusion; Saponins

1. Introduction

Quinoa (Chenopodium quinoa) is a pseudo-cereal withorigins dating to the Incas. The pre-Colombian Andeanpeople used the seed as a staple food component, and attimes, replaced the animal protein in their diet with quinoa(Koziol, 1992). Today, quinoa is mainly cultivated inArgentina, Bolivia, Chile, Colombia, Ecuador, and Peru,locations that mostly coincide with the limits of the IncaEmpire. Quinoa has also shown promise in tests of farm-scale cultivation in high altitudes of Colorado, and nearsea level in Washington and Oregon, as well as in Englandand in Scandinavia (National Research Council, 1989).

The quinoa plant grows from 3 to 6 ft., in height andbears leaves that extend from the stalk. Quinoa seeds growin large clusters at the end of the stalk, and seed color var-ies from pink, orange, red, purple, tan, to black. Quinoaseeds, shape of which resembles sesame seeds, can be con-sumed whole or ground into flour. Quinoa is commonly

0308-8146/$ - see front matter � 2005 Elsevier Ltd. All rights reserved.

doi:10.1016/j.foodchem.2005.12.001

* Corresponding author. Tel.: +1 732 932 9611x224; fax: +1 732 9326776.

E-mail address: karwe@aesop.rutgers.edu (M.V. Karwe).

referred to as a pseudo-cereal since it is not a member ofthe grass family, but produces seeds that can be milled intoflour and used much like a cereal crop.

The shortage of provisions in needy countries can poten-tially be solved by cultivation of quinoa (or otherwise actas an ideal human food supplement) since it can survivethe most barren farming conditions (potential for cultiva-tion in marginal lands and temperate regions) while main-taining a high nutritive value and supplying a reasonableyield (Prakash, Nath, & Pal, 1993). Quinoa can survivelow rainfall, high altitudes, thin cold air, hot sun, sub-freez-ing temperatures, salinity, and poor sandy alkaline soils(Przybylski, Chauhan, & Eskin, 1994). The adaptabilityof different cultivars to salt stress merits special note(National Research Council, 1989). However, growth formost strains is optimized with short day lengths and cooltemperatures.

Quinoa has economical potential to be realized since theentire plant can be utilized. The leaves can be consumed ina salad and are rich in various minerals. The seeds can beconsumed whole or ground into flour for a variety of foodapplications (Coulter & Lorenz, 1990). Seeds are usuallysoaked in water to remove the soapy saponins, bitter

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glucoside–triterpenoid compounds that cover the surface ofthe seeds. The residual water can be used to shampoo thehair. The leaves, roots, and stalks can be used for animalfodder.

Research efforts in quinoa have been focused on itschemical composition, with considerable attention paidto saponins in quinoa. There has been some work accom-plished in processing quinoa, focused mainly on theeffects of dehulling and washing on changes in chemicalcomposition; specifically removal of saponins. Usually,quinoa is processed by means of soaking, rubbing, rins-ing, and boiling in the domestic setting. It is industriallyprocessed by means of wet and dry milling (Becker &Hanners, 1990).

Today’s health conscious consumers are illustrating apreference towards value added products, and in general,more nutritious food items. The opportunity to supplementor completely replace common cereal grains (corn, rice andwheat) with a cereal of higher nutritional value (such asquinoa) is inherently beneficial to the public interests.

In this study, quinoa flour was subjected to steam pre-conditioning, extrusion, and roasting. Effects of theseprocesses on quinoa were determined via HPLC analysis.Process enhanced compounds were characterized withinstrumental analysis.

2. Materials and methods

2.1. Materials

Quinoa. Quinoa seeds (Chenopodium quinoa Willd) werepurchased from Quinoa Corporation, Gardena, CA.

Solvents. HPLC grade methanol, HPLC grade ethyl ace-tate, HPLC grade acetonitrile, HPLC grade water, and for-mic acid were purchased from Sigma-Aldrich, St. Louis,USA.

Extraction medium. Sample extraction for HPLC analy-sis was prepared with Whatman # 42 filter paper, ashless70 mm circles. Acrodisc 0.45 lm · 3 mm syringe filters fur-ther refined extracts prior to direct HPLC injection.

Table 1Screw configuration and extrusion elements

Extrusion zones*

Feed zone (84 mm) Zone 1 (196 mm) Zone 2 (210 mm) Zone 3 (1

SK 42/42 42/21 T 28/28 28/14SK 42/42 42/42 28/28 KB 45/5/

42/42 IGEL 42 20/2042/21 28/28 20/20IGEL 42 28/28 20/2028/28 KB 45/5/28 20/20

28/14 20/2028/14 KB 45/5/

20/10 LH20/1020/10

KB, kneading block; LH, left-handed (reverse) element; SK, feed element; T,* IGEL, mild kneading element.

2.2. Methods

Milling. Quinoa seeds were pulverized with a model DFitz Mill (W.J. Fitzpatrick Co., Chicago, USA) to producequinoa flour.

Steam pre-conditioning. Steam pre-conditioning wasperformed with a 57 l Varimixer (Welbilt, South Plainfield,NJ, USA) modified for steam injection. 11 kg of milled qui-noa flour were mixed while being exposed to 100 �C steamfor 15, 30, 45 and 60 min. Temperature of the flour wasrecorded using an Omega Microprocessor Thermometer,model HH21, complete with Omega type T thermocouple(Omega Engineering, Stamford, CT, USA). The thermo-couple was placed at the center of the kettle.

Extrusion. Extrusion was performed with a twin screwextruder (model ZSK-30 from Coperion, formerly Wernerand Pfleiderer Corp., Ramsey NJ, USA). The extruder hastwo co-rotating, self wiping screws (30.7 mm diameter,4.7 mm channel depth, and 878 mm processing length; L/D = 28.6) in a steel barrel with five zones. Each zone isheated by resistive electric heaters and the temperature ofeach zone can be controlled independently. The screw con-figuration used in extrusion experiments consisted of for-ward conveying elements, mild mixing elements, kneadingelements, and reverse elements (Table 1). The die hadtwo circular orifices (3 mm diameter, 5 mm long). Quinoaflour was metered into the feed section of the extruder witha volumetric feeder from K-Tron Corporation (Pitman,NJ, USA). Water was injected into the feed section of theextruder immediately after the feed port using a tripleaction piston pump from US Electric Corporation(Milford, CT, USA). Both the feeder and the pump werecalibrated prior to extrusion runs to determine the setpoints required for desired mass flow rates of quinoa flourand water, respectively. The total mass flow rate (flour +water) was kept constant at 300 g/min for all experiments.Temperatures at zones I, II, and III were set to roomtemperature, 80 and 120 �C, respectively, while the temper-atures at zones IV and V were adjusted such that thedesired die temperatures could be maintained.

78 mm) Zone 4 (98 mm) Zone 5 (84 mm) Die zone (28 mm)

20/10 KB 45/5/14 14/1414 20/10 KB 45/5/14 LH 14/14

KB 45/5/20 14/1420/10 LH 14/1420/10 14/1420/10 14/1414/14

20 14/14

transition element.

Table 2HPLC program gradient

Time (min) Solvent A (%) Solvent B (%)

Initial 80 2025 10 9055 10 9060 80 20

Solvent A, HPLC grade acetonitrile; Solvent B, solution of 0.05% formicacid in HPLC grade water.

K. Brady et al. / Food Chemistry 100 (2007) 1209–1216 1211

Extrusion was performed at a range of temperatures,moisture contents, and screw speeds. The die temperaturewas varied between 130 and 170 �C, moisture contentbetween 16% and 24%, and screw speed between 250 and500 rev/min.

Roasting. Roasting was performed with a Isotemp Vac-uum Oven, model 282A from Fisher Scientific (Pittsburgh,PA, USA). Approximately 100 g of milled quinoa flour wasplaced uniformly in a baking sheet, 34 cm · 24 cm· 1.5 cm, at 200 �C for 10 min.

Extraction for HPLC analysis. Fifty grams of quinoasample were placed into a 500 ml Erlenmeyer flask with150 ml of methanol and a magnetic rod. After samplewas stirred, using a Lab-Line Multi-Magnestir, andexposed in methanol for 24 h, the slurry was subjected tovacuum filtration with a Buchner funnel and filter paper(Whatman # 42). Solid sample residue from the filter wasscraped off and placed back into the original Erlenmeyerflask. Filtered liquid residue was set aside and covered.The solid residue was subjected to a second extraction withmethanol (100 ml). After sample was magnetically stirredfor 24 h, vacuum filtration was performed again with Buch-

Fig. 1. HPLC chromatogram of the

ner funnel and filter paper. Liquid residues from successiveextractions in methanol were merged into a 500 ml flask.Solid residues were discarded. The methanol extracts (inthe 500 ml flask) were exposed to rotary evaporation tocompletely remove methanol solvent, using a Buchi Rota-vapor R110 with Meyer N-Evap Analytical Evaporatorwater bath, model 112.

The dried extract was then subjected to 100 ml ethyl ace-tate and magnetically stirred for 24 h. After exposure to ethylacetate, sample was vacuum filtered with Buchner funnel andfilter paper. Liquid residue was covered and set aside. Solid

extract of unprocessed quinoa.

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residue in flask was exposed to a successive extract with ethylacetate (100 ml) and stirred for 24 h. After exposure, vacuumfiltration was performed again with Buchner funnel and filterpaper. Liquid residues from successive extractions in ethylacetate were merged into a 500 ml flask. The ethyl acetateextracts (in the 500 ml flask) were exposed to rotary evapora-tion to completely remove ethyl acetate solvent.

Residue (in flask) was exposed to methanol aliquots andconveyed to a 25 ml graduated cylinder using a 3 ml syringewith Acrodisc 0.45 lm filter. Process was repeated (approx-imately seven times) until 15 ml of methanol dissolved-qui-noa extract was obtained. The 15 ml filtered extracts weretransferred into labeled vials and placed in a �5 �C freezer.

Moisture analysis. Moisture analysis was performedwith a moisture analyzer from Sartorius (model MA 30,Edgewood, NY, USA). Approximately 2 g of pre-conditioned sample was uniformly placed in an aluminumdish and placed in the unit. The unit drives off moistureusing a 130 �C oven and automatically calculates themoisture content of the sample in approximately 15 min.

TLC. TLC was performed on Sigma-Aldrich silica gelTLC plates (250 lm thickness, 2–25 lm particle size).

Fig. 2. HPLC chromatogram of the extract of quinoa flour exposed to extrusiomoisture content.

Compounds were visualized by spraying a 10% (v/v)H2SO4 ethanol solution under heat (Zhu et al., 2002).

HPLC. Quinoa extracts were analyzed with reversephase high performance liquid chromatography (HPLC).Mobile phases, including HPLC grade acetonitrile (SolventA) and a solution of 0.05% formic acid in HPLC gradewater (Solvent B), were conveyed with two Waters, model510, pumps. A Discovery C18 column by Supelco (25 cm ·4.6 mm · 25 mm) was utilized for compound separation.The program gradient (determines the mobile phase com-position), encoded by a Waters Automatic Gradient Con-troller, is available in Table 2. Twenty microliter sampleswere loaded into the Waters (Milford, MA, USA) modelU6K, injector port. Analysis of samples was performedwith a Waters, model 484, Tunable Ultraviolet AbsorptionDetector at 254 nm wavelength. Data was interpreted andprinted with a Spectra-Physics, model SP4290 integrator.

Nuclear magnetic resonance spectroscopy. NMR spectrawere recorded with a Varian AM-600 NMR spectrometer(Varian, Inc., Palo Alto, CA), with TMS as an internalstandard . Isolated compounds were dissolved in methanolfor carbon NMR spectroscopy. Analyses were performed

n at die temperature of 170 �C, screw speed of 375 rev/min, and 16% (w/w)

K. Brady et al. / Food Chemistry 100 (2007) 1209–1216 1213

at the City University of New York, Staten Island, NewYork.

Mass spectrometry. The mass spectra of the isolated pro-cess enhanced compound were obtained using both chemi-cal ionization and atmospheric pressure chemical ionization.Chemical ionization mass spectrum was recorded with aFinnigan MAT 8230 (Finnigan, Bremen, Germany) high-resolution, double focusing magnetic sector mass spectro-meter using direct probe sample injection. Atmosphericpressure chemical ionization (positive ion mode) mass spec-trum was recorded with a Micromass Platform II LC-MSinstrument, sample was introduced through an empty col-umn and methanol was used as a solvent.

3. Results and discussion

Pre-conditioning with steam, before extrusion, is oftenused to make extruded products. Pre-conditioning withsteam increases the temperature and moisture content ofthe raw materials going into the extruder, thereby reducingthe load on the extruder. It allows additional residence timefor the moisture to penetrate into the flour grains.

Fig. 3. HPLC chromatogram of the extract of quino

Fig. 1 shows the HPLC chromatogram of raw quinoaextract. This chromatogram illustrates the profile of com-pounds that are eluted from the HPLC between 0 and44.7 min. A large peak area correlates to a strong presenceof a particular compound, and a small peak area correlatesto a weak presence of a particular compound. If the detec-tor does not register the presence of a compound, there willbe the absence of a peak on the chromatogram.

The HPLC chromatograms of extracts of quinoa flourprocessed by steam for 15, 30, 45, and 60 min are nearlyidentical to the chromatogram of unprocessed quinoaextract. Therefore, it was concluded that processing bymeans of steam pre-conditioning results in no significantimpact on the chemical profile of quinoa. The minimaleffect of steam pre-conditioning on the chemical profile ofquinoa can probably be attributed to the relatively mildprocessing temperatures.

Processing by means of extrusion significantly impactedthe chemical profile of quinoa flour as compared to raw qui-noa extract. Fig. 2 shows the HPLC chromatogram ofextruded quinoa extract. This chromatogram illustrates theprofile of compounds that are eluted from the HPLC

a flour exposed to roasting for 10 min at 200 �C.

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between 0 and 45.52 min. A duplex of peaks, with retentiontimes of approximately 18 min, was enhanced extensively byextrusion. In addition, peaks with retention times between 25and 30 min, were diminished considerably via extrusion.This phenomenon was magnified under application of amore intense extrusion process. Extrusion processes con-ducted at a higher temperature, lower moisture content,

Fig. 4. APCI-LC-MS spectra for isolated process enhanc

Fig. 5. CI-MS spectra for isolated process enhanced c

and faster screw speed produced a more dramatic escalationof peak height and area for the duplex of peaks eluted at18 min, and a more dramatic reduction of peak height andarea for the series of peaks eluted between 25 and 30 min.The extrusion conditions, which revealed the most dramaticchanges in the profile, were die temperature of 170 �C, screwspeed of 375 rev/min, and 16% (w/w) moisture content.

ed compound (retention time at 18.09 min in Fig. 2).

ompound (retention time at 18.09 min in Fig. 2).

Fig. 6. NMR spectra for isolated process enhanced compound (retention time at 18.09 min in Fig. 2).

K. Brady et al. / Food Chemistry 100 (2007) 1209–1216 1215

The roasting process also produced significant changesin the chemical profile of quinoa flour, as compared toraw quinoa flour. Fig. 3 shows the HPLC chromatogramof roasted quinoa extract. This chromatogram illustratesthe profile of compounds that are eluted from the HPLCbetween 0 and 38.38 min. A duplex of peaks, with retentiontimes of approximately 19 min, was enhanced extensivelyby roasting. A series of peaks that elute from 10 to14 min, and another series that elutes from 35 to 38 min,were also enhanced via roasting.

Of significant interest was the process enhanced com-pounds that appeared in both roasting and extrusion pro-cesses. These processes significantly enhanced a duplex ofpeaks with a retention time of 18 min. Extrusion and roastingexposed flour to much higher temperatures, which presum-ably resulted in the dramatic changes of profile for extrudedand roasted quinoa. These compounds were isolated andaccumulated by HPLC for characterization studies.

Mass spectra revealed the isolate to have a molecularweight of 480 D. The molecular weight was confirmedusing APCI-LC-MS and CI-MS techniques. Spectra forboth MS techniques can be seen in Figs. 4 and 5. Previousresearch (Gee, Price, Ridout, Wortley, & Hurrell, 1993),which examined saponins in processed quinoa, identifiedan aglycon compound with a molecular weight of 480 Dusing FAB-MS. The compound was a mass fragment ofphytolaccagenic acid, present in the methanolic extract ofbitter quinoa.

Examination of the NMR spectra (Fig. 6) reveals thatthe spectral signal has characteristic of a terpenoidstructure.

TLC of the isolate displayed a white color when exposedto UV radiation. This color is indicative of a terpenoidcompound.

4. Conclusions

Analysis of the extrusion and roasting enhanced isolatestrongly suggests characterization as terpenoid compound.Extraction was performed using methanol and ethyl ace-tate, solvents with the ability to dissolve terpenoids. HPLCprofile indicated a strong presence of the compound atwavelength of 254 nm. MS data reveals a molecular weightof 480 D, which is in the range of triterpenoid structures.NMR data reveals a terpenoid signature in the spectra.Saponins in quinoa are of the triterpenoid variety. Theexperimentally determined molecular weight of theenhanced compound suggests it may be the dehydrationproduct of phytolaccagenic acid, the aglycon of a majorsaponin found in quinoa. It is hypothesized that saponinspresent in raw quinoa flour are cleaved and dehydratedwhen placed under the extreme heat duress produced inextrusion and roasting processes. This could also explainwhy compounds enhanced in extrusion and roasting pro-cesses were not enhanced in quinoa pre-conditioned withsteam.

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Saponin degradation would directly alter sensory per-ception and pharmacological properties. The bitter tasteimparted by saponins could potentially be reduced throughextrusion and roasting processes. The nutraceutical proper-ties of saponins could also be reduced through extrusionand roasting processes.

Acknowledgments

This paper is dedicated to our co-author Robert T.Rosen who passed away in May 2005. The research wassupported by a Grant from the Center for Advanced FoodTechnology, Rutgers University, NJ, USA. Authors thankMr. Joe Lech for technical support.

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