(LB01-18-25) Application of Germination Pre-treatment to Improve Flavor Quality and Antioxidant Activities of Roasted Peanut Oil

Objectives: To investigate the effect of varying period of germination on the release of flavor precursors in peanut and the flavor, sensory, and antioxidant stability of roasted peanut oil

Methods: Fresh peanuts were soaked for 12 h and germinated at 25 °C with 95% humidity for 0, 12, 24, 36, and 48 h, activating endogenous enzyme activities and hydrolysis of macromolecules. 1000 g of soaked or germinated peanuts were roasted at 540 W for 8 min in a microwave oven, and oil was extracted by hydraulic pressing. The composition of soaked or germinated peanuts, including enzyme activities, protein, lipids, and sugars, was determined to participate in Maillard reaction and lipid oxidation to release flavor precursors. Oxidative stability was evaluated to maintain the flavor and improve oil quality.

Results: Biological activities of endogenous enzymes, including amylase (5.43-6.55 mg/min/g), lipase (0.2-0.38 mg/min/g), acid protease (0.65-0.83 mg/min/g), and neutral protease (0.76-0.94 mg/min/g), increased gradually with germination time (p < 0.05). Germination reduced the content of total sugars, fats, and proteins while releasing free amino acids (5.34–11.87 mg/g) and soluble sugars (9.29–11.68 g/100 g) (p < 0.05). In addition, germination positively influenced the flavor quality in peanut oil, with higher concentrations of heterocyclic compounds: pyrazines (50,321 to 87,290 μg/kg), pyrroles (715 to 2,830 μg/kg), pyridines (1,424 to 1,513 μg/kg), ketones (34 to 157 μg/kg), and phenols (5,778 to 8,217 μg/kg), while reducing aldehydes (8,265 to 1,271 μg/kg) and esters (206 to 125 μg/kg) (p < 0.05). Moreover, acid value (AV) (0.28 to 1.02 mg/KOH/g), oxidation induction time (OIT) (9.80 to 13.06 h), α-tocopherol and γ-tocopherols were slightly increased, while peroxide value (POV) reduced with germination (p < 0.05). Germination enhanced sensory characteristics (roasted, sweet nutty, burn), while soaked peanuts reduced aroma, leading to unpleasant oxidized odors (green, fatty, raw peanut) (p < 0.05).

Conclusions: This study suggests that germination can improve both the flavor and antioxidant stability of peanut oil through a biochemical action, and short-term germination time as a mean of pretreatment was found to be best to provide a rich flavor and quality of oil.

Funding Sources: This work was sponsored by Qinghai Province Key R & D and Transformation Plan of China.