Quality testing for infant formula

Significance of the Topic

Lactose is the primary carbohydrate in human milk and a key component of infant formulas. However, lactose intolerance or glucose-galactose malabsorption in infants necessitates strict elimination of dietary lactose, with regulations demanding levels below 10 mg/100 kcal. Analytical methods that reliably quantify trace lactose in complex food matrices are therefore critical for ensuring product safety and compliance.

Objectives and Study Overview

This study aimed to develop a fast, sensitive, and robust ion chromatography method with pulsed amperometric detection (IC-PAD) for low-level lactose determination in infant formulas, baby foods, and lactose-free milk. Validation was conducted across a range of sample types, including NIST reference materials and commercial products, to demonstrate method accuracy and practicality.

Methodology and Instrumentation

Methodology:

• Sample Preparation: Homogenization of powdered or liquid matrices followed by aqueous extraction. Protein removal via Carrez precipitation or automated low-volume inline dialysis.
• Chromatographic Conditions: Isocratic separation on a Metrosep Carb 2 - 250/4.0 column using 400 mmol/L NaOH eluent.
• Detection: Pulsed amperometric detection with a Metrohm Thin-Layer cell employing a gold working electrode and palladium reference electrode.

Used Instrumentation:

• 940 Professional IC Vario ONE/Prep 1 with Metrohm Inline sample preparation options
• 945 Professional Detector Vario – Amperometry for PAD
• Metrosep Carb 2 - 250/4.0 separation column
• 858 Professional Sample Processor – Pump for sample handling
• Low Volume Inline Dialysis accessory
• Thin-Layer cell (Carb) with Au working and Pd reference electrodes
• MagIC Net 4.0 Professional software for system control and data analysis

Main Results and Discussion

• Retention: Lactose eluted in under 20 minutes, with clear separation from lactose derivatives such as epilactose and lactulose, enhancing selectivity.
• Working Range: Linear response from 0.05 to 80 mg/L in standards, equivalent to 0.2–21 000 mg/100 g across dilutions.
• Validation: Repeatability (RSDr) and day-to-day variability met AOAC criteria (<10% and <7%, respectively). Spike recoveries ranged between 98% and 111%, demonstrating method accuracy.
• Comparison of Sample Prep: Inline dialysis provided comparable results to Carrez precipitation with reduced preparation time and reagent use, showing a relative standard deviation of 2.1% in a NIST baby food sample.

Benefits and Practical Applications

• High Sensitivity: LOQ of 4 mg lactose/100 g enables detection well below regulatory thresholds for lactose-free products.
• Robustness: Automated inline sample preparation and stable baseline ensure long-term reliability.
• Versatility: Suitable for routine quality control, regulatory compliance checks, and research involving diverse milk-based matrices.
• Efficiency: Inline dialysis reduces manual processing time and chemical consumption.

Future Trends and Potential Uses

With ongoing advances in automation and detector technology, IC-PAD methods may be further optimized for higher throughput and multiplexed carbohydrate profiling. Integration with laboratory information management systems (LIMS) and emerging microfluidic sample prep modules could streamline workflows. Expanding applications in nutritional analysis, clinical diagnostics, and functional food research are anticipated.

Conclusion

The presented IC-PAD method offers a reliable, sensitive, and flexible approach for quantifying trace lactose in complex infant nutrition matrices. Compliance with stringent validation criteria and optional inline sample preparation makes it a valuable tool for quality control and regulatory laboratories.

Reference

1. EFSA. Scientific Opinion: Essential Composition of Infant and Follow-up Formulae. EFSA J. 2014;12(7):3760.
2. Facioni MS, Raspini B, Pivari F, Dogliotti E, Cena H. Nutritional Management of Lactose Intolerance: The Importance of Diet and Food Labelling. J Transl Med. 2020;18(1):260.
3. EFSA. Scientific Opinion on Lactose Thresholds in Lactose Intolerance and Galactosaemia. EFSA J. 2010;8(9):1777.
4. European Commission. Commission Delegated Regulation (EU) 2016/127 of 25 September 2015. Off J Eur Union L251. 2016.
5. FAO/WHO. CODEX Alimentarius – General Standard for the Labelling of Prepacked Foods CXS 1-1985. Int Food Stand.