Whey permeate analysis with NIRS

Significance of the Topic

In dairy manufacturing, real-time monitoring of whey permeate is crucial for optimizing product yield and ensuring consistent quality. Near-infrared spectroscopy (NIRS) provides a rapid, non-destructive, and reagent-free approach to quantify multiple components simultaneously, reducing analysis time and resource consumption.

Objectives and Study Overview

This study aimed to develop and validate NIRS-based prediction models for key quality parameters of whey permeate, including lactose, moisture, pH, ash, phosphate, and protein content. By leveraging multivariate calibration, the method seeks to support at-line and off-line process control in dairy production.

Methodology and Instrumentation

158 whey permeate samples were scanned in diffuse reflection mode over 1000–2250 nm using a Metrohm NIR Analyzer with a small cup accessory. Spectral preprocessing and wavelength selection improved the robustness of partial least squares regression models. A 75/25 calibration/validation split ensured independent assessment of model performance.

Main Results and Discussion

The NIRS models achieved high correlation with reference laboratory measurements (R2 > 0.80) for most parameters, with the exception of lactose (R2 = 0.689). Figures of merit included standard error of calibration (SEC), standard error of cross-validation (SECV), and standard error of prediction (SEP), demonstrating adequate precision for routine quality control:

• Protein: R2 = 0.899, SEC = 0.18 %, SEP = 0.21 %
• Lactose: R2 = 0.689, SEC = 1.22 %, SEP = 1.41 %
• Moisture: R2 = 0.864, SEC = 0.13 %, SEP = 0.11 %
• Ash: R2 = 0.813, SEC = 0.09 %, SEP = 0.11 %
• Phosphate: R2 = 0.909, SEC = 158 ppm, SEP = 156 ppm
• pH: R2 = 0.862, SEC = 0.07, SEP = 0.08

The validation results confirm NIRS as a reliable tool for rapid compositional analysis of whey permeate.

Benefits and Practical Applications

Implementing NIRS enables:

• Simultaneous quantification of multiple constituents without sample preparation
• Rapid analysis (seconds per sample) suitable for at-line or offline use
• Non-destructive measurement preserving sample integrity
• Streamlined quality control workflows in dairy processing

Instrumental Setup

The analysis employed a Metrohm NIR Analyzer equipped with a small cup accessory for diffuse reflection measurements in the 1000–2250 nm range. Data acquisition and model calibration were performed using dedicated Metrohm software.

Future Trends and Applications

Advances in calibration algorithms, such as machine learning and adaptive models, will further enhance NIRS accuracy and robustness. Integration of inline NIR probes can allow continuous monitoring of whey permeate streams. Emerging hyperspectral imaging techniques may extend capabilities to spatially resolved quality assessment.

Conclusion

This application demonstrates the feasibility of NIRS for efficient, multi-parameter quality control of whey permeate in dairy production. The method reduces analysis time, eliminates chemical reagents, and supports real-time monitoring, contributing to improved process optimization and product consistency.

References

ISO 22662:2024 Milk and milk products – Determination of lactose content by high-performance liquid chromatography
ISO 8968-1:2014 Milk and milk products – Determination of nitrogen content (Kjeldahl method)
ISO 5537:2023 Dried milk and dried milk products – Determination of moisture content (loss on drying)
ISO/DIS 9877 Milk and milk products – Determination of ash content by incineration