Analysis of Amino Acids in Fermented Food and Drinks

Significance of the Topic

Monitoring amino acid profiles in fermented foods is critical for assessing nutritional value, fermentation quality and flavor development. Accurate quantification supports quality control in the food industry and research on fermentation processes.

Objectives and Study Overview

This study demonstrates the application of post-column o-phthalaldehyde (OPA) fluorescence derivatization using the Shimadzu amino acid analysis system to quantify amino acids in fermented products. It covers simultaneous analysis of 38 standard amino acids and real-sample testing of soy sauce, mirin and miso.

Methodology

Sample Preparation:

• Soy sauce diluted 1:200 with pH 2.2 lithium citrate buffer
• Mirin diluted 1:10 and membrane filtered
• Miso extracted with water, centrifuged and supernatant diluted 1:10

Derivatization and Separation:

• Li-type cation exchange column separates amino acids
• Secondary amines converted to primary amines with hypochlorous acid
• Post-column reaction with OPA reagent at 39 °C
• Detection by fluorescence (Ex 350 nm, Em 450 nm)

Chromatographic Conditions:

• Gradient elution with amino acid mobile phase kit (Li type)
• Flow rate 0.6 mL/min, reagent flow 0.3 mL/min
• Column temperature 39 °C, injection volume 10 µL

Used Instrumentation

• Shimadzu amino acid analysis system
• Shim-pack Amino-Li column (100 mm × 6.0 mm I.D.)
• RF-10AXL fluorescence detector
• Amino Acid Reagent and Mobile Phase Kits (Li type)

Key Results and Discussion

Standard Analysis:

• Baseline separation of 38 amino acids achieved within 140 minutes

Fermented Food Analysis:

• Soy sauce and mirin chromatograms showed clear detection of key amino acids
• Miso extract yielded well-resolved peaks after simple pretreatment

These results confirm the method’s sensitivity and reproducibility for complex food matrices.

Benefits and Practical Applications

• High sensitivity and selectivity for amino acid quantification
• Minimal sample preparation and rapid derivatization
• Wide applicability in food quality control, nutritional profiling and fermentation research

Future Trends and Potential Uses

Integration with mass spectrometry for structural confirmation
Automated sample handling to increase throughput
Method miniaturization and green chemistry adaptations to reduce reagent consumption
Extension to other complex biological matrices beyond food products

Conclusion

The post-column OPA fluorescence method on the Shimadzu system provides a robust and sensitive platform for comprehensive amino acid analysis in fermented foods and beverages. Its ease of use and broad applicability make it valuable for routine quality control and research settings.