DOI: https://doi.org/10.55373/mjchem.v25i1.11

Keywords: Shorea; mineral content; anti-nutritive; extraction method; antioxidant activity

Abstract

Shorea macrophylla (S. macrophylla) and Shorea palembanica (S. palembanica) are known as “Engkabang Jantung” and “Engkabang Asu”, respectively, by natives in Sarawak, Malaysia. The oilseeds remain underused due to a lack of scientific approach. This study aimed to determine proximate compositions and antinutritional factors of S. macrophylla and S. palembanica seeds and compare the fatty acid profiles, chemical properties and antioxidant activity between mechanical extraction (ME) and Soxhlet extraction (SE). The proximate compositions of S. macrophylla and S. palembanica seeds were 21.47% and 27.25% (moisture); 0.67% and 1.98% (ash); 41.37% and 49.06% (total lipid); 79.44% and 82.37% (total carbohydrate); 15.67% and 7.72% (crude fiber), respectively. Seeds of S. macrophylla and S. palembanica contained high levels of K (1186.50 and 400.17 mg/100 g), Ca (238.31 and 128.62 mg/100 g), Mg (300.50 and 117.17 mg/100 g), and Na (75.12 and 30.14 mg/100 g). The antinutritional factor phytate was detected in small concentrations in both species. At the same time, oxalate was found at a higher concentration in S. palembanica (2.43 mg/100 g) than in S. macrophylla (1.91 mg/100 g). The bioavailability of Ca and Zn influenced by antinutritional factors phytate and oxalate was calculated based on their molar ratios. The bioavailability of minerals affected by phytate did not exceed the critical value, suggesting adequate mineral absorption. However, high oxalate content exceeded the critical value of bioavailability (2.5), indicating insufficient mineral availability. SE was more efficient in extracting Shorea oils. Stearic, oleic and palmitic acids were the major fatty acids in S. macrophylla and S. palembanica oils, with no significant difference in fatty acid profiles between types of extraction (p>0.05). The acid (AV) and peroxide (PV) values of ME oils (AV: 3.47 to 4.75 mg NaOH/g; PV: 7.96 to 10.62 meq O2/kg) were lower than SE oils (AV: 4.69 to 8 mg NaOH/g; PV: 9.92 to 14.58 meq O2/kg). Therefore, mechanical extraction is considered the method of choice to extract Shorea oils. The iodine value (IV), AV, and PV of Shorea oils do not meet the required standards of the Indonesian National Standard (SNI) of Tengkawang butter and Cocoa Butter standards. Thus, a further refining process is suggested to increase the quality of S. macrophylla and S. palembanica oils.