FACTORS AFFECTING RAPID VISCO ANALYZER CURVES FOR THE DETERMINATION OF MAIZE KERNEL HARDNESS

The effects of grinding condition, solids content and beating rate on apparent viscosity measured with a Rapid Visco Analyzer (RVA) For maiz e kernel varieties with different endosperm hardness were investigated , Maize hardness was measured with a tangential abrasive dehulling dev ice (TADD), density, flotation, and subjective ratings. Harder maize k ernels gave rise to coarser particles that took longer to reach peak v iscosity and had lower peak heights than the finer particles from soft kernels. Finely ground samples produced distinct viscosity curves. Hi gher solids content increased peak viscosity. A low heating rate produ ced the highest peak viscosities. The viscosity characteristics of dec orticated, degermed maize kernels were similar to those observed for w hole maize samples. Peak viscosity and slope were significantly correl ated with kernel hardness values. Evaluation at 18 % solids concentrat ion with 10 degrees C/min heating rate for soft kernels and 2.4 degree s C/min for hard kernels resulted in the greatest sensitivity to diffe rences in endosperm hardness. Maize samples can be initially separated into hard and soft categories by flotation or density. RVA parameters can then be adjusted to distinguish between samples within each group . The RVA technique is sensitive to differences in maize kernel endosp erm hardness with the advantages of small sample size, short testing t ime, simple procedure, easy data management and versatility for screen ing kernels. (C) 1997 Academic Press Limited