Maize Authentication: Quality Control Methods and Multivariate Analysis (Chemometrics)

Abstract

Maize is one of the most important cereals because of its numerous applications in processed foods where it is the major or minor component. Apart from maize authenticity issues related to cultivar and geographical origin (national and/or international level), there is another important issue related to genetically modified maize. Various objective parameters such as fatty acids, phenolic compounds, pigments, heavy metals were determined in conjunction with subjective (sensory analysis) in order to identify the maize authenticity. However, the implementation of multivariate analysis (principal component analysis, cluster analysis, discriminant analysis, canonical analysis) is of great importance toward reaching valid conclusions on authenticity issues. This review summarized the most important finding of both objective and subjective evaluations of maize in five comprehensive tables in conjunction with the discussion.

Keywords:

• Maize
• corn
• authentication
• sensory analysis
• instrumental methods
• authentication markers
• GMOs
• geographical origin
• variety
• detection

Notes

¹The probes were labelled with the fluorescent reporter dye 6-carboxyfluorescein (FAM) at the 5′ -end, and the fluorescent quencher dye 6-carboxytetramethylrhodamine (TAMRA) at the 3′ -end.

²Three BCR samples A (BT11, NK603 and MON810 with 5% GMO) and the B (AM32 plasmid).

³Agarose Gel Electrophoresis.

⁴The following GM lines: MON810, MON863, GA21 and NK603.

⁵Primer-ampl. Prod. (bp): Q-Bt11-1F, -2R, -P:(96); Q-Bt176-1F, -2R, -P:(64); Q-GA21-1F, -2R, -P:(112); Q-MON810-1F, -2R, -P:(91); Q-MON863-1F, -2R, -P:(90); Q-NK603-1F, -2R, -P:(110); Q-CBH351-1F, -2R, -P:(96); Q-TC1507-1F, -2R, -P:(83); Q-T25-1F, -2R, -P:(90); and Q-zSSIIb-1F, -2R, -P:(88).

⁶20 copies of haploid genome.

⁷CRMs of GM MON813 and Bt176 in six different mass fractions (< 0.2, 0.1, 0.5, 1, 2, and 5%), as well as kernels of pure MON810 line.

⁸LODs were as follows: 0.764 pg/ml, 0.018% (0.357 pg/ml) and 0.056% (∼ 0.751 pg/ml) in regards to the purified protein, CRMS, and 100% MON810 protein extract dilutions.

⁹Melting temperatures of the PNA:DNA duplex measured at c = 5 μM for each strand.

¹RFLPs of 35 probe-enzyme combinations.

²Mean values of twenty maize field populations.

³From the dendrogram through the UPGMA method for 39 native populations and 19 checks based on a matrix of Euclidian distances derived from 17 morphological traits.

⁴From the dendrogram through the UPGMA method for 39 native populations and 19 checks based on a matrix of Euclidian distances derived from the combined dataset of 17 morphological traits and 29 isozyme alleles.

⁵The 25 inbred and 25 hybrid lines were separated in 2 clusters each and 6 and 7 subclusters, respectively.

⁶The 25 inbred and 25 hybrid lines were separated in 8 and 9 groups, respectively, according to their geographical origin.

⁷Genetic similarity mean values.

⁸ODx/ODt: the ratio of optic density of each band to total optic density of bands from the same lane.

⁹Based on Roger's distances.

¹⁰The 488 populations WEREseparated in 2 clusters and 5 and 6 subclusters each, respectively.

¹TAPP: meso-tetra (4-trimethylammonium phenyl) porphyrin.

²TNAA: thermal neutron activation analysis.

³FNAA: fast neutron activation analysis.

⁴(LaALC)₂F₂: alizarine complexone and La(III) complex.

⁵The experimental results showed that 1250-fold NO^{2 −}; 1000-fold K⁺, Na⁺, Ag⁺, Ca(II), Sr(II), Cl⁻ and NO^{3 −}; 500-fold Mg(II) and Br⁻; 100-fold I⁻ and SO₄ ^{2 −}; 75-fold Co(II); 50-fold Cr(III) and Mo(VI) and 40-fold As(V) have no effect on the determination of F⁻ (1 × 10⁻⁶ M).

⁶Champan and Pratt, 1961.

¹ Oyenuga, 1968.

² Bibby and Champion, 1974.

³Peak area (mg).

⁴Proteins from SDS-PAGE.

⁵Separation buffer was 80 mM phosphate glycine (pH 2.5) + 60% ACN and 0.05% HPMC. Separation conditions were: in 50-μm i.d. × 27-cm (20-cm Ld) uncoated capillaries at 12.5 kV and 45°C.

⁶Proteins were extracted with 70% ethanol + 0.5% Na acetate + 5% β -ME and separated as in (3).

¹The four groups were as follows: A). non-modified, denoted N; B) cold water swelling, denoted P; C) hydroxypropylated and phosphated, denoted R; D) acetylated and phosphated, denoted H.

²30 visible seed mutants and 55 ears used for calibration-110 samples and 2640 kernels from which spectral data were collected.

³GM (Bt176) and non-GM maize. ANN: Artificial Neural Networks; MLP: Mutlilayer Perceptron; GA: Genetic Algorithm; SA: Sensitivity Analysis.

⁴EZ6 maize line, corn gluten meal (CGM) 60%, and 25 different maize products.

⁵Osborne, T. B. The Proteins of the Wheat Kernel; Carnegie Institute: Washington, DC, 1907.

¹CIM DEAE: Convection Interaction Media Diethylaminoethyl.

²At high purity samples varies from 1.9 to 2.5.

³The Bt176, also known as “Maximizer” or “Event 176”, was the first GM maize approved in the EU (1997).

⁴TNE Buffer (10 mM Tris (pH 8.0), 150 mM NaCl, 2 mM ethylenediaminetetraacetic acid (EDTA)).

⁵Also known as “StarLink”. LOD calculated down to 5 copies of CBH-351 genome.

⁶PCR: Polymerase Chain Reaction; QC-PCR: Quantitative Competitive-PCR; LDR: Ligated Detection Reaction; RT-PCR: Real Time-PCR.

⁷Official Collection of Test Methods (2002).

⁸The PCR programmes worked under different operational conditions and, namely, were: VR1-F/IVR1-R GMO3/GMO4 Cry03/Cry04 IVS2-2/PAT-B VW01/VW03 T25-F7/T25-R3 p35s-f2/petu-r1.

⁹LIF: Laser Induced Fluorescence.

¹⁰Lipp, M.; Brodmann, P.; Pietsch, K.; Pauwels, J.; Anklam, E. IUPAC collaborative trial study of a method to detect genetically modified soybeans and maize in dried powder. J. AOAC Int. 1999, 82, 923–928.