**3. Methods**

#### **3.1. Extraction of PSMs**

Pre‐cultures grown overnight from a liquid culture are used to inoculate bacterial cultures at 1:100 dilution.


#### *3.1.2. Extraction of PSMs from TSB and beverage for quantitative analysis*


#### *3.1.3. Extraction of PSMs from milk for quantitative analysis*


#### **3.2. Analysis of PSMs**

#### *3.2.1. Liquid chromatography methodology*

**1.** Transfer the supernatants into glass sample vials. Cool down the sample tray to 10°C and put the sample vials in it.


#### *3.2.2. Qualitative analysis of PSMs from culture*

*3.1.2. Extraction of PSMs from TSB and beverage for quantitative analysis*

**2.** Transfer 1.5 mL supernatants to 4‐mL centrifuge tubes.

**4.** Transfer 1.0 mL supernatants to 2‐mL centrifuge tubes.

*3.1.3. Extraction of PSMs from milk for quantitative analysis*

**3.** Extract water layer 1.5 mL to 4‐mL centrifuge tubes.

**5.** Transfer 1.0 mL supernatants to 2‐mL centrifuge tubes.

*3.1.4. Extraction of PSMs from pork for quantitative analysis*

10 min, 0°C) after extraction of 2 h (37°C, 200 rpm). **3.** Transfer 1.0 mL supernatants to 2‐mL centrifuge tubes.

**3.2. Analysis of PSMs**

*3.2.1. Liquid chromatography methodology*

put the sample vials in it.

coffee were not included.

138 Frontiers in Frontiers in Staphylococcus Aureus *Staphylococcus aureus*

**1.** The *Staphylococcus aureus* cells were removed by centrifugation (5000 rpm, 10 min, 4°C) after overnight growth (~16 h) in 4 mL of culture medium (TSB or beverage) at 37°C with shaking at 200 rpm. The "beverage" means pure juice or juice beverage. Soda, water and

**3.** The supernatants were incubated at a 1:1 ratio with 1‐butanol for 2 h (37°C, 200 rpm).

**6.** Filter the solution through a 0.22‐µm filter using a syringe before LC‐MS analysis.

(~16 h) in 4 mL of culture medium (milk) at 37°C with shaking at 200 rpm.

**4.** The extract was incubated at a 1:1 ratio with 1‐butanol for 2 h (37°C, 200 rpm).

**7.** Filter the solution through a 0.22‐µm filter using a syringe before LC‐MS analysis.

(~16 h) in 4 mg of culture medium (pork) at 37°C with shaking at 200 rpm.

**2.** Remove fat by frozen centrifugation technology (5000 rpm, 10 min, 0°C).

**5.** Dry the extract under nitrogen and redissolve the dried sample in 0.5 mL ultrapure water.

**1.** The *Staphylococcus aureus* cells were precipitated by acetonitrile after overnight growth

**6.** Dry the extract under nitrogen and redissolve the dried sample in 0.5 mL ultrapure water.

**1.** The *Staphylococcus aureus* cells were precipitated by acetonitrile after overnight growth

**2.** Add 1.5 mL 1‐butanol and remove fat by frozen centrifugation technology (5000 rpm,

**4.** Dry the extract under nitrogen and redissolve the dried sample in 0.5 mL ultrapure water.

**1.** Transfer the supernatants into glass sample vials. Cool down the sample tray to 10°C and

**5.** Filter the solution through a 0.22‐µm filter using a syringe before LC‐MS analysis.

