African Journal of
Agricultural Research

  • Abbreviation: Afr. J. Agric. Res.
  • Language: English
  • ISSN: 1991-637X
  • DOI: 10.5897/AJAR
  • Start Year: 2006
  • Published Articles: 6578

Full Length Research Paper

The effect of harvest conditions and drying temperature on drying kinetics of two popcorn genotypes

Fernanda Machado Baptestini
  • Fernanda Machado Baptestini
  • Departamento de Engenharia Agrícola e Ambiental, Universidade Federal de Viçosa, CEP 36570-000, Viçosa, MG, Brazil.
  • Google Scholar
Paulo Cesar Corrêa
  • Paulo Cesar Corrêa
  • Departamento de Engenharia Agrícola e Ambiental, Universidade Federal de Viçosa, CEP 36570-000, Viçosa, MG, Brazil.
  • Google Scholar
Gabriel Henrique Horta de Oliveira
  • Gabriel Henrique Horta de Oliveira
  • Instituto Federal de Brasília, Campus Gama. DF 480, Lote 01, Setor de Múltiplas Atividades, Brasília/DF, Brazil.
  • Google Scholar
Aline Almeida da Paixão
  • Aline Almeida da Paixão
  • Departamento de Engenharia Agrícola e Ambiental, Universidade Federal de Viçosa, CEP 36570-000, Viçosa, MG, Brazil.
  • Google Scholar
Patrícia Fontes Machado
  • Patrícia Fontes Machado
  • Departamento de Engenharia Agrícola e Ambiental, Universidade Federal de Viçosa, CEP 36570-000, Viçosa, MG, Brazil.
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  •  Received: 29 May 2014
  •  Accepted: 10 September 2014
  •  Published: 23 September 2014

Abstract

The present work aimed to assess the effect of the initial moisture content of grains (at harvest), velocity of the harvester cylinder and air temperature on the diffusion coefficient, as well as to achieve the activation energy of the drying process of two popcorn cultivars. Grains of popcorn from the cultivars Zélia and CMS 43 were mechanically and manually harvested and thrashed. The rotations of the threshing cylinder were fixed at 500, 600 and 700 rpm, with initial moisture contents of 0.235 and 0.175 db. They were dried with drying air temperatures of 40, 50 and 60ºC, until reaching the final moisture content of 0.137 db. The diffusion coefficient increased with increased air temperature, presenting average values from 6.345 × 10-11 to 3.075 × 10-13 m2s-1 for the temperature range studied, depending on the initial moisture content, cultivar and level of mechanical damage. The cultivar CMS 43 (C2) is more resistant to the mechanical damage caused by the threshing cylinder, and the structural changes caused by it increased the diffusion coefficient. The relation between diffusion coefficient and temperature can be described by the Arrhenius expression, which presents activation energy for liquid diffusion in the grains of popcorn from 1.50 to 45.92 kJ mol-1.

 

Key words: Mechanical damage, initial moisture content, diffusion coefficient.