Analysis of headspace compounds of distillers grains using SPME in conjunction with GC/MS and TGA

Chemical composition of headspace compounds of distillers grains was investigated using solid phase microextraction (SPME) along with GC/MS and TGA. Dryer feed (DF) and distillers dried grains (DDG) from a local distillery were utilised for this study. A SUPELCO 75 mum Carboxen/PDMS SPME fibre was found suitable for extraction of analytes from grains. Samples were placed in small vials (40 mL from SUPELCO) filled to one-third of their capacity. SPME was exposed to the headspace for 1 to 2 h. The fibre was then thermally desorbed in GC injection port for separation and identification. The gas chromatogram showed as many as 64 compounds eluting out of the column, the number being greater in DF as compared to DDG. Thermogravimetric analysis (TGA) was performed on the grains to study the oxidative stability of the compounds. SPME fiber was inserted directly into TGA purge gas outlet to study the compounds being evolved. Three weight loss transitions were observed in the TGX curve of DF and DDG. The components from the three transitions were captured by SPME and analysed by GC/MS for identification. TGA helped in determining the degradation stages of grains thereby indicating the temperature limits in drying grains. Difference between the heated and unheated DF and DDC have been discussed in detail. (C) 2001 Academic Press.