ARS | Publication request: Effect of Different Time/Temperature Roast Combinations on Peanut Flavor-Descriptive Sensory, Electronic Nose and Electronic Eye Characterization

Submitted to: Institute of Food Technology
Publication Type: Abstract Only
Publication Acceptance Date: June 10, 2011
Publication Date: June 10, 2011
Citation: Effect of Different Time/Temperature Roast Combinations on Peanut Flavor-Descriptive Sensory, Electronic Nose and Electronic Eye Characterization. Institute of Food Technology. 1.

Technical Abstract: Roasting is of central importance to peanut flavor. Standard industry practice is to roast peanuts to a specific surface color (Hunter L-value) for a given application; however, equivalent surface colors can be generated using different temperature/time roast combinations. To better understand the effects of roast temperature and product color on peanut flavor, a standard lot of runner peanuts was roasted using 5 roast temperatures to 3 post-blanch surface colors corresponding to light, medium and dark. Samples were roasted in triplicate and evaluated in duplicate by a trained sensory panel using a 15 point universal scale for 17 attributes. Descriptive sensory analysis (DSA) was compared to volatile data collected from the same samples using various Electronic Nose instruments (E-Nose - Gemini/aFox/Heracles) in triplicate. As expected, samples roasted to different colors were differentiated (p<0.05) using DSA terms including, roasted peanutty, sweet aromatic, dark roast, raw beany, bitter, and ashy. Dark roast, bitter, ashy and raw beany attributes were correlated with E-Nose sensor data (R2 >0.70). Principal component analyses of E-Nose data revealed a clear distinction for volatiles among peanuts roasted at 147, 157, 167, 177 and 187 °C, whereas the sensory panel noted clear differences only between 147 and 187 °C. GC analyses (Heracles) suggested the majority of discrimatory volatiles were Maillard products such as pyrazines and dimethyl pyrazine. Hexanal was another important discriminatory compound identified and was more prominent in samples roasted to the lighter color. Generally, the DSA panel found peanuts roasted at higher temperatures to have decreased intensities (p<0.05) for attributes, such as ashy, which are typically associated with negative peanut flavor. Low temperature long time roasting may accelerate peanut oil oxidation leading to changes in hexanal concentrations. Hunter L-value data was also compared to electronic-Eye data. A Global Statistical Quality Control Model was developed to evaluate degree of roast.