Zein Characterisation of South African Maize Hybrids and Their Respective Parental Lines Using MALDI-TOF MS

Abstract

Zeins are important storage proteins and play a role in grain texture and impact on processing. Having a technique to accurately quantify the individual zeins and the size of these proteins would allow for more precise understanding of the impact these individual protein have on grain texture and/or processing. Matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) was used to characterise zein protein profiles of five South African maize hybrids, grown at three locations, and their respective parental lines. A new, simplified and shortened zein extraction method was used to characterise the zein profiles and to determine any possible relationship between the hybrids and their parents. A matrix solution comprising two matrices, α-cyano-4-hydroxy-cinammic acid (CHCA) and 2-(4-hydroxyphenylazo) benzoic acid (HABA), was required to detect all major zein (α, β, γ and δ) classes. Within the set of hybrids and parents, additional peaks with molecular weights not previously reported were observed. These were identified as belonging to the δ-zein, β-zein and γ-zein. Relationships between the hybrids and their respective parental lines were observed indicating genetic variation for these zein classes exists. The MALDI-TOF MS method identified differences in individual zein proteins and these differences were observed between hybrids. The method shows a potential for accurately quantifying the presence and molecular size of zein proteins which may be important in milling and food processing. Storage proteins play an important role not only in grain composition but also in some processes such as milling, and variation in these individual proteins may impact on efficiency of processing.