CO₂ levels, technical breakage and quality of maize grains stored under different conditions¹

Níveis de CO₂, quebra técnica e qualidade dos grãos de milho armazenados em diferentes condições

ABSTRACT

The use of CO₂ sensors has been reported as an effective tool in the early detection of signs of deterioration, allowing good accuracy in decision-making about the quality of stored grains. The objective of this study was to quantify the CO₂ levels produced by maize grains stored at ambient temperature in a prototype silo, with initial moisture contents of 14, 16 and 18% w.b., and to evaluate the quality of the product over time and the technical breakage. Analyses of moisture content, ash, proteins, lipids, Hue Angle (color), germination and electrical conductivity were performed. Inside the silos, the amount of CO₂, relative air humidity and temperature were monitored every hour. Grain quality evaluations were carried out at four storage times (0, 30, 60 and 90 days). A completely randomized design in a 3 × 4 factorial scheme with six replicates was used. Grains with higher moisture contents showed higher technical breakage and losses associated with CO₂ emissions. Moisture content, protein, lipids, germination, bulk density, lightness and chroma decreased over time, while the electrical conductivity increased, resulting in greater damage to membranes and loss of quality of maize grains. Monitoring of CO₂ in the grain mass is a good tool to assess the quality of grain, and higher initial moisture content caused greater level of CO₂ emission and reduction in quality of maize grains.

Key words:
Zea mays L.; deterioration; carbon dioxide; respiration

HIGHLIGHTS:

CO₂ dynamics is associated with respiration of maize grains.

High CO₂ levels increase maize grain losses during storage.

High moisture contents increase respiration and technical breakage of stored grains.