Tissue structure and nutritional composition of tree peony (Paeonia suffruticosa Andr.) seed during germination and evaluation of lipid concomitants of the oils

Germination as flexible pretreatment enhances oilseed processing. This study investigated whether germination changes the structure and processing performance of tree peony seed (TPS). Structurally, the number and fiber structure of oil bodies were increased and became more visible, and oil was more easily extracted after germinated. And sugars, proteins and lipids are main metabolic sequences of energy substances in TPS. Germination increased TPS's internal water freedom, causing total sugar content to rise initially and then decrease, while protein and oil contents peaked on 15 d at 24.02 g/100 g and 57 g/100 g, respectively. Moreover, glycerolipids and glycerophospholipids dominated the lipid metabolites of TPS, and germinated alter the expression of Diglyceride, Triglyceride, and Phosphatidylcholine. Tree peony seed oil exhibited elevated lipid concatenation post-germination, boasting 4130.74 mg/kg of phytosterols and 94.68% unsaturated fatty acids. Consequently, moderate germination enhanced the nutritional quality of TPS, with a 15-day germination period being optimal for its application as an oilseed in the production of superior nutritious oils.