Tween 80

The β-carotene bleaching method was used as described by Kassim et al. [25 (link)] with some modifications. The β-carotene solution was composed of linoleic acid (132 μL), β-carotene (6 mg), and Tween 80 (600 μL) (Samchun Co., Seoul, Korea) with 20 mL of chloroform. The chloroform in the solution was removed using a rotary evaporator. The absorbance of solution at 470 nm was adjusted to 1.20 with distilled water. Two hundred microliters of bacterial samples, gamju extracts dissolved in distilled water (50 mg/mL), and 1 mg/mL ascorbic acid (positive control) was mixed with 4 mL of the solution and incubated at 50 °C for 2 h. The absorbance of the supernatant was measured at 470 nm for 0 and 2 h and calculated using the following equation: $\mathrm{Inhibition}\mathrm{of}\mathsf{\beta }-\mathrm{carotene}\mathrm{and}\mathrm{linoleic}\mathrm{acid}\mathrm{oxidation}(\%)=\frac{{\mathrm{A}}_{\mathrm{sample},2\mathrm{h}}-{\mathrm{A}}_{\mathrm{control},2\mathrm{h}}}{{\mathrm{A}}_{\mathrm{control},0\mathrm{h}}-{\mathrm{A}}_{\mathrm{control},2\mathrm{h}}}\times 100\%$
where A_{sample, 2 h} and A_{control, 2 h} are absorbance values of the sample (bacterial or gamju) and distilled water after 2 h of the reaction, respectively. A_{control, 0 h} is the absorbance of distilled water at the initial time.