Flavor characteristics of peeled walnut kernels under two-steps roasting processes

Area of Science:

• Food Science
• Sensory Science
• Chemical Analysis

Background:

• The impact of different roasting techniques on the flavor profile of peeled walnut kernels (PWKs) is not well-understood.
• Understanding these effects is crucial for optimizing walnut processing and product development.

Purpose of the Study:

• To investigate and compare the effects of three roasting methods—hot air binding (HAHA), radio frequency (HARF), and microwave irradiation (HAMW)—on the flavor profile of PWKs.
• To identify key odor-active compounds responsible for sensory differences.

Main Methods:

• Evaluated PWKs roasted using HAHA, HARF, and HAMW via olfactory, sensory, and textural analyses.
• Utilized Solvent Assisted Flavor Evaporation-Gas Chromatography-Olfactometry (SAFE-GC-O) to identify and quantify odor-active compounds.
• Employed partial least squares regression (PLSR) and VIP values to correlate compounds with sensory attributes.

Main Results:

• HAMW roasting yielded the highest total concentration of odor-active compounds (499 μg/kg), significantly more than HAHA (229 μg/kg) and HARF (273 μg/kg).
• HAMW produced the most pronounced nutty flavor, characterized by 2-ethyl-5-methylpyrazine.
• While HARF increased chewiness and brittleness, these textural properties did not significantly contribute to the flavor profile.

Conclusions:

• Microwave irradiation (HAMW) is the most effective roasting method for enhancing the flavor quality of peeled walnut kernels.
• Specific odor-active compounds identified through SAFE-GC-O are key drivers of the sensory differences observed between roasting methods.