Quality Assessment of Mushroom Casing Soil Using Visible and near Infrared Spectroscopy

Abstract

Casing soil is a crucial component in the production of mushrooms ( Agaricus bisporus) and in the United Kingdom and Ireland it is prepared by neutralising raw peat with lime. The initial peat quality determines many of the physical and chemical properties of the subsequent casing product and this, in turn, significantly impacts on the yield and quality of mushrooms produced. Information on the physical and chemical properties of the casing supplied, in particular those associated with water retention and absorption, is critical to an optimal management strategy. The casing suppliers need a rapid method to evaluate key properties, but the available analytical techniques are slow and laborious, often taking 7–15 days to complete. Raw peat and casing samples were scanned for visible and near infrared (vis-NIR) spectra and the results assessed using principal component analysis. The samples (177) were also analysed for pH, electrical conductivity, moisture content, ash, water absorption, water retention and bulk density. Using partial least squares regression analysis of the spectra and the measured values of the target parameters, calibration equations were generated and cross-validated within the sample set. The equations were then validated using an independent sample set (44) collected from casing suppliers and growers. Early indications show good potential for the prediction of commercially important properties, such as dry matter, ash content, water absorption, water retention and pH. With a turnaround time of minutes, from initial scanning to the presentation of results, vis-NIR spectroscopy affords both the casing suppliers and, ultimately, the growers the opportunity to progress and improve upon current industry standards.