Maize Maize

Maize is one of the top three cereal crops grown and consumed throughout the world. There are different types of maize grown for commercial purpose viz., sweet corn, popcorn (Zea mays everta) and baby corn. Among which, popcorn is a type of maize that expands from the kernel and pops up when heated. It is popular as a fibre rich and nutritious snack in all the parts of the world.

Normal maize starch is composed of amylase (linear) and amylopectin (branched). The amylose content in normal maize ranges from 25 to 30% but can vary among different cultivars and especially with the presence of mutant genes. Many recessive mutants of maize have been identified that alter the quantity and quality of starch components in the endosperm. According to

Each corn kernel after recording the weight was placed in a single 15-ml falcon tube containing 2 ml 0.3% sodium metabisulphite and 1% lactic acid pH 3.8. Subsequently capped tubes were incubated at 52oC for 24 h. Discarded steep liquid (down sink with plenty of water) and rinsed seed with distilled water. Carefully removed and discarded the pericarp and embryo with forceps. Placed the endosperm in eppendorf tube and grinded the contents of endosperm in 0.5 ml water with micro-pestle making in to fine paste. Made up volume to 1 ml with distilled water. Mixed well and removed 0.1 ml sample for starch analysis to second eppendorf tube. Remaining 0.9 ml extract was stored in -20oC to serve as source for subsequent repeat assay if required. Added 0.4 ml water and centrifuged at 14,000g in cold room for 5 min. Removed supernatant to second eppendorf and added 0.5 ml water mixed well and re-centrifuged as above. Pooled the two supernatants to get soluble extract. Transferred 50-μl aliquots of soluble extract to each of four screw-capped eppendorf. Resuspended the pellet of the first eppendorf tube in 1 ml water, which represented insoluble extract. Mixed well before removing 50μl aliquots of insoluble extract to each of four screw-capped eppendorf tubes. Made up the volumes in each eppendorf tube to 0.5 ml with distilled water. Autoclaved the screw caped tubes with insoluble extracts to solubilise the

Monitored OD at 340 nm, and recorded the value after the readings were stable. This represented the initial OD (OD1). Added 2.5 U G6PDH, mixed well with mini glass stirring stick. Monitored OD frequently as it was increasing rapidly and then slowly reached a stable value, which was recorded as second value (OD2). (Difference in OD)/6.22 = μmol glucose in cuvette). For computation purposes 1 μmol glucose is equivalent to 162 μg starch, was used as standard