Cereal Chem 69:567-573   |  VIEW ARTICLE

Popping Behavior and Zein Coating of Popcorn.

P. J. Wu and H. G. Schwartzberg. Copyright 1992 by the American Association of Cereal Chemists, Inc. 

Expansion ratios, extents of evaporation, popping temperatures, and heating-induced enthalpy changes were measured versus temperature and moisture content for popcorn. These were used to identify the conditions that induce popping and the levels of moisture loss needed to stabilize puffed structures. Popping probably initially occurs through expansion of vapor trapped in individual grains of starch. Pore walls rupture, vapor escapes, and pores merge when excessive vaporization occurs. The enthalpy balance during popping indicates that evaporative cooling during popping is counterbalanced almost quantitatively by release of heat as a result of melt solidification. Popping temperatures of popcorn in 200 C air inversely correlated with initial moisture content. The temperature dropped 5.4-6.2 C at popping. Coating popcorn with zein slightly reduced the rates of moisture loss during heating. Expansion bulk volumes increased 15% for coated popcorn, and the unpopped ratio decreased slightly, but only when the popcorn popper was not preheated. Expansion volume did not increase significantly when the popper was preheated. Zein coating did not significantly improve expansion bulk volume and unpopped ratios for samples with damaged pericarp.