Shelf-life studies of flavour characteristics in model UHT liquid systems enriched with wholegrain oat

Development of malodourous compounds, hexanal and p-vinyl guaiacol (PVG), in UHT model liquid systems fortified with wholegrain oat were evaluated. Single and mixed systems using oat powder (3, 5, and 7% w/w), skim milk powder (SMP, 2.8% w/w) and sucrose (6.7% w/w) were subjected to UHT treatment and 29 days ambient storage. Both chromatographic analyses and panellists' perceived aroma intensity show a positive relationship between the content of hexanal and PVG, storage time and oat concentrations trialled. Ratio of the odour activity values (OAV) plotted against time shows that although PVG aroma initially is dominant, hexanal aroma, with a ratio of about 0.5, has twice the intensity of the PVG aroma for the remaining 29 days. Oat samples (with skim milk) were unacceptable when hexanal concentration was 3-5 times its threshold whilst the PVG level was still below its threshold in the same samples.