Evaluation of quality attributes and antimicrobial characteristics of cold-pressed milk thistle ( Silybum marianum (L.) Gaertn) seed oil to ascertain its potential applications

Abstract

This study investigates the quality characteristics of milk thistle (Silybum marianum (L.) Gaertn.) seeds sourced from their natural habitat, as well as the oil extracted from these seeds using the cold-pressing method, and assesses its suitability for human consumption. The average levels of milk thistle seed oil (MTSO) were 22.15%, while the average levels of milk thistle seed protein were 28.5%. Among the minerals found in the seeds, the calcium concentration was the highest, at 899.14 mg/100 g. The composition of cold-pressed milk thistle oil revealed that linoleic acid accounted for 57.9% of the oil. The peroxide value was 1.33 meq O₂/kg, the acid value was 1.77 mg KOH/g, the iodine value was 101.54 g/100 g, and the saponification value was 188.12 mg KOH/g. Cold-pressed MTSO had the highest antibacterial effect against Staphylococcus aureus (14.68 mm), with the lowest minimum inhibitory concentration (MIC) of 0.035 mg/L and minimum bactericidal concentration of 0.047 mg/L observed for the same bacteria. The highest antifungal effect was observed in Rhodotorula minuta (14.92 mm), which also exhibited the lowest MIC (0.023 mg/L) and minimum fungicidal concentration (0.016 mg/L) values. This study provides not only a physical analysis of cold-pressed MTSO but also a thorough evaluation of its chemical and biological properties. In this study, the potential of oil obtained by cold-pressing – a natural method – the seeds of milk thistles collected from their natural habitat was evaluated, particularly in the food industry and related sectors. The results showed that, in addition to being consumed directly as food, it can also be used as a natural food preservative due to its antimicrobial effects. Furthermore, owing to the beneficial compounds in its composition, it can also be considered a natural raw material suitable for use in the medical, pharmaceutical, and cosmetic sectors.