Galangal and ginger essential oils exerted microbial growth inhibitory activity and preservation potential on tofu

Abstract

Galangal and ginger are commonly used as spices. Interestingly, their antimicrobial activity has been reported against a wide array of microorganisms. This study aimed to evaluate the effects of essential oils of galangal and ginger on the microbial growth, physical characters, and preservation potential on tofu during 8-day storage at room temperature. The essential oils were prepared by steam-and-water distillation method, and their constituents were analyzed by Gas Chromatography-Mass Spectroscopy (GC-MS). The microbial growth on the tofu was evaluated by the indirect enumeration method. The physical characters of tofu were organoleptically observed. The preservation potentials were calculated based on the changes in tofu physical characters relative to the negative control. The main constituents of galangal essential oil were 1,8-cineole, β-farnesene, and α-pinene, while those of ginger were geranyl acetate, 1,8-cineole, and camphene. Galangal essential oil significantly inhibited microbial growth, maintained the texture of tofu until day eight, and exerted preservation potential for four days. The same preservation effect was shown by ginger essential oil at 6.26 mg/mL, however it generated a weaker microbial growth inhibitory activity and resulted in the unfavorable texture on tofu. Hence, galangal essential oil is a suitable candidate to be developed into a natural food preservative.