The influence of pumpkin seed roasting conditions (110–140
°C) and screw-pressing on the formation of previously undescribed
Δ7-phytosterol oxidation products and tocopherylquinone
adducts with nucleophilic phosphatidylethanolamine species was investigated.
The roasting process of pumpkin seed paste at a temperature above
120 °C for 30 min considerably enhanced the formation of Δ7-oxysterols. Targeted analysis [electron impact mass spectrometry
(MS), 1D-nuclear magnetic resonance] led to the identification of
five novel markers of pumpkin paste roasting, among which (3β,5α,22E,24S)-stigmasta-7,22-dien-6-one-3-ol (6-oxo-α-spinasterol),
stereoisomers of (3β,5α,22E)-7,8-epoxystigmast-22-en-3-ol
(7,8-epoxy-α-spinasterol), and (3β,5α)-22,23-epoxystigmast-7-en-3-ol
(7,8-epoxy-α-spinasterol) were reported in edible oils for the
first time. Simulated culinary processing provided novel stereoisomers
of (3β,5α,22E)-stigmasta-7,22-dien-3,6-diol,
unusual (3β,5α,22E)-stigmasta-7,22-dien-6,15-dione-3-ol,
and (5α,22E)-stigmasta-7,22-dien-3-one accompanied
by minor stereoisomers of (3β,5α)-7,8;22,23-diepoxystigmastan-3-ol.
Moreover, a clear relationship between the pumpkin seed oil stability
index and synergistic effect of glycerophospholipids with present
tocochromanols was found. High-resolution atmospheric pressure chemical
ionization–MS experiments clearly demonstrated the formation
of various γ-tocopherylquinone adducts with primary amines,
namely, octylamine. The mitigation strategy of potentially detrimental
oxysterols from pumpkin seed oil included optimization of processing
parameters while maintaining the formation of desirable sensory-active
compounds.