Monitoring Changes in Volatile Organic Compounds during Apple Puree Processing by Varying Thermomechanical Conditions

This study examined how the concentrations of volatile organic compounds (VOCs) evolve in apple puree during processing under various temperature and grinding conditions. A full factorial experimental design was applied, combining two temperatures (70 and 95 °C) with two grinding speeds (300 and 1000 rpm). VOCs were identified and quantified by a dynamic headspace analysis coupled with GC-MS, with calibration carried out at four critical stages of the process. Results showed that after cooking, higher grinding speeds led to a significant increase in aldehydes such as (E)-2-hexenal (from 0.06 to 0.13 mg/kg at 70 °C and from 0.016 to 0.054 mg/kg at 95 °C) and hexanal (from 0.53 to 0.70 mg/kg at 70 °C and from 0.14 to 0.30 mg/kg at 95 °C). In contrast, acetaldehyde concentrations decreased. Raising the temperature from 70 to 95 °C significantly reduced the concentrations of most VOCs (p-value <0.001), with the exception of furfural, which began to form at temperatures above 82.5 °C. This overall reduction in VOCs is likely due to chemical or enzymatic transformations rather than volatilization. These findings represent an initial step toward developing a decision-support tool aimed at identifying optimal processing conditions based on VOC changes to enhance quality control in fruit purees.