The effects of oxygen, nitrogen, and carbon dioxide steeping regimes on endosperm modification and embryo growth of germinating barley seeds

Abstract

A study has been made of the effects ofO2, N 2, CO 2, and air treatment during steeping of two varieties of barley, Nordal from Denmark and Tokak from Turkey. Steeping time was varied from I to 3 days and the seeds subsequently germinated on sand for 7 days. Water uptake, endosperm modification (measured as cell wall breakdown), and embryo growth (measured as root and shoot growth) were monitored throughout germination.The results showed that steeping in the presence of pure 02 and CO2 were toxic and inhibited subsequent water uptake, modification, and embryo growth. Anaerobic steeping in the presence ofN 2 had little inhibitory effect on these three parameters when compared to steeping in well aerated water. It is confirmed that removal of CO 2 from grains during steeping is more important than addition of oxygen.

Oxygen Deficiency in Barley (Hordeum vulgare) Grain during Malting

“…If the barley in the present experiments had a similar consumption rate, the oxygen concentration in the malting drum headspace would still be above 19% after 16 h. It therefore seems more likely that the carbon dioxide concentration, which rose to 1% during the air rest, was responsible for the delayed germination. CO indeed previously been shown to impair germination and modification (28), and extraction of CO 2 during the air rest has been found to improve the malt extract content on the industrial production scale (29). Another possibility is that the absence of aeration left a thicker water film on the grains during the air rest, leading to decreased oxygen uptake rates.…”