Physicochemical Comparison of Rambutan Nephelium lappaceum Seed Fat and Dairy Butter Fat for Alternative Use

Rambutan (Nephelium lappaceum) seed fat is an underexplored plant-based lipid which shows potential for both functional and nutritional applications. In this study, its physicochemical properties along with its fatty acid profile were compared with those of the dairy butter. The Rambutan seed fat showed a melting point of 28.5°C, which is about 3–6°C lower than butter (32–35°C) indicating a softer consistency. Saponification value of Rambutan seed fat (201.54 mg KOH/g) was also lower than that of butter (225–240 mg KOH/g), suggesting the presence of longer-chain fatty acids. The peroxide value was less than the quantitation limit of 0.2 meq O₂/kg of fat, reflecting minimal primary oxidation at the time of analysis. The fatty acid composition was dominated by monounsaturated fatty acids (74.3%), mainly oleic and eicosenic acids, which is substantially higher than in butter (28–30%). In contrast, saturated fatty acids were markedly lower (15.2% vs. 63–65%), while polyunsaturated fatty acids were relatively higher (10.5% vs. 2–3%). These differences help explain the softer texture and lower melting behaviour of Rambutan seed fat. Overall, the findings suggest that it could serve as a viable alternative fat, although further studies on stability and application are needed.