Processes to enhance trans-resveratrol in peanut kernels and their optimization
Sales, Jocelyn Masiglat
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Abiotic stresses including wounding through size reduction, UV, ultrasound (US), and combined US-UV were applied to peanut kernels to enhance trans-resveratrol biosynthesis. Slicing produced the highest trans-resveratrol followed by chopping, whereas whole peanuts had the least, suggesting that only mild damage to cells was needed for maximum biosynthesis. UV, US and US-UV treatments of sliced peanuts further increased trans-resveratrol from 0.37 to 3.29, 6.35 and 7.14 µg/g, respectively, corresponding to >100% that found in red wines, a known major food source. Resveratrol-enhanced peanuts (REP) had less roasted peanutty flavor and more bitter, astringent, cardboard, oxidized and fishy off-flavors resulting in lower acceptance rating (OA) ≥ 5.0 or neither like nor dislike compared to untreated controls of 7.4 or like moderately. Trans-resveratrol was positively correlated to astringent, bitter and painty flavors of REP. Optimization using response surface methodology showed that optimum US-UV produced REP with highest trans-resveratrol of 4.8 µg/g followed by US and UV with 3.8 and 2.1µg/g, respectively, with maximum consumer acceptance ≤5 or neither like nor dislike. Furthermore, US-UV had maximum 170 µg/g p-coumaric acid and 150 µM TE/g ORAC corresponding to >100% that found in red wines. The shelf life of roasted REP was 52 days at 25oC, shorter than 90 days in regular roasted peanuts due to weaker peanutty flavor and more intense off-flavors, with a Q10 value of 2.2 for lipid oxidation. REP application in peanut bars increased shelf life at 25oC to 146 days probably due to sugar’s protective effect which slowed down lipid oxidation or masked the effect on off-flavors. On a per serving basis, about 3 ½ REP bars containing 30 g peanuts/bar would provide equal resveratrol in 140 mL serving of red wine. REP will provide increased value and profitability for the food industry and health benefits to consumers.