Walnut (Juglans regia L.) kernel oil bodies recovered by aqueous extraction for utilization as ingredient in food emulsions: Exploration of their microstructure, composition and the effects of homogenization, pH, and salt ions on their physical stability

• Published in: Food research international Vol. 173; p. 113197
• Main Authors: Lopez, Christelle, Rabesona, Hanitra, Novales, Bruno, Weber, Magalie, Anton, Marc
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-11-2023; Elsevier
• Subjects: Food engineering; Homogenization; Interface; Life Sciences; Lipid droplet; Natural oil-in-water emulsion; Oil body; Oleosome; Plant based food; ω3 polyunsaturated fatty acid; Natural oil-in-water emulsion; Plant based food; Oleosome; Lipid droplet; ω3 polyunsaturated fatty acid; Oil body; Homogenization; Interface; OleosomeLipid droplet; Polyunsaturated fatty acid
• ISSN: 0963-9969; 1873-7145
• DOI: 10.1016/j.foodres.2023.113197

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•Oil bodies are natural lipid droplets abundant in walnut kernels.•Aqueous extraction by grinding permits the recover of walnut kernel oil bodies and protein bodies.•Walnut kernel oil bodies contain phospholipids, well-balanced PUFA, phytosterols and γ-tocopherol.•Oil bodies hemi-membrane is a sophisticated mixture of proteins and phospholipids.•The physical stability of oil bodies is altered by pH, NaCl and CaCl2.
Natural oil-in-water emulsions containing plant oil bodies (OBs), also called oleosomes, rich in health-promoting omega-3 polyunsaturated fatty acids (ω3 PUFA) are of increasing interest for food applications. In this study, we focused on walnut kernel OBs (WK-OBs) and explored their microstructure, composition and physical stability in ionic environments as well as the impact of homogenization. A green process involving aqueous extraction by grinding of WK allowed the co-extraction of OBs and proteins, and centrifugation was used to recover the WK-OBs. Confocal laser scanning microscopy images showed the spherical shape of WK-OBs with an oil core envelopped by a layer of phospholipids (0.16 % of lipids) and embedded proteins. Their mean diameter was 5.1 ± 0.3 µm. The WK-OBs contained 70.1 % PUFA with 57.8 % ω6 linoleic acid and 12.3 % ω3 α-linolenic acid representing 68 % and 11.6 % of the total fatty acids in the sn-2 position of the triacylglycerols (TAG), respectively. Trilinolein was the main TAG (23.1 %). The WK-OBs also contained sterols (1223 ± 33 mg/kg lipids; 86 % β-sitosterol), carotenoids (0.62 ± 0.01 mg/kg lipids; 49.2 % β-carotene), and tocopherols (322.7 ± 7.7 mg/kg lipids; 89 % γ-tocopherol), confirming their interest as health-promoting ingredients. The decrease in the size of WK-OBs under high-pressure homogenization avoided phase separation upon storage. The anionic WK-OB surface at neutral pH was affected by stressful ionic environments (pH, NaCl, CaCl2), that induced aggregation of WK-OBs and decreased the physical stability of the emulsions. Emulsions containing WK-OBs are promising to diversify the market of the ω3-rich plant-based food products and beverages.