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Pol. J. Food Nutr. Sci. 2007;57(Special issue 2A):89–94
The objective of this study was to compare properties of walnuts roasted at different technological parameters. Effects of roasting temperature (100-180oC), the roasting time (5-30 min) as well as the type of heating medium (hot air or boiled vegetable oil) on sensory and physical characteristics were determined. Experiment was conducted according to Response Surface Methodology. Nuts were analyzed for moisture content, colour, texture parameters, FFA and PV and sensory attributes. It has been stated that properties of walnuts were dependent on temperature and time of roasting. As roasting temperature and time increased nuts moisture decreased. Nuts roasted in oil showed darker colour than the samples treated in hot air. The colour changed and was getting darker together with higher roasting temperature and longer roasting time. Nuts roasted in oil exhibited harder texture than those roasted in hot air. As roasting temperature and time increased nuts texture was more crispy and delicate, independently on type of roasting. Roasting influenced the quality of nuts oil fraction – in all analysed samples FFA content increased, however PV increased mainly in nuts roasted in oil. Samples roasted at 130-150oC for 15-20 min exhibited the best sensory properties in both methods. Nuts roasted at lower temperatures showed too hard texture, light colour and taste and flavour typical of fresh nuts. Nuts roasted at the highest temperatures and for longer time were too dark and exhibited burned taste and flavour.