Development of a relationship between olfactory response and major odorants from organic wastes

Determination of an averaged human olfactory response as odour concentratio n to odours by instrumental means has been sought to simplify on-site measu rement and reduce cost. Different concentrations of hydrogen sulphide, 4-me thyl phenol, ammonia and acetic acid were used to simulate livestock waste odour. A second-order uniform precision rotatable central composite statist ical design identified 31 odour mixtures to establish a human olfactory res ponse model. An odour panel containing eight people was selected according to recognised criteria. They had an average age of 43.3 years. A multiple l inear regression model accounted for 74.1% of the variance, with a decreasi ng order of influence of hydrogen sulphide>4-methyl phenol much greater tha n acctic acid within the bounds of the model described. Surprisingly, 4-met hyl phenol concentration produced a negative effect on the olfactory respon se. To enable better fitting of the complex olfactory response radial basis function, neural network modelling was used to account for 88% of the vari ance. With pig manure odours outside the studied concentration range the ne twork model did not function. Predictions using the linear regression model were on average 20% less than observed values. These findings demonstrate that this approach is appropriate to determine the odour concentration from pig manure using the main odorants. (C) 2000 Society of Chemical Industry.