Del Mar Photonics

AOTF Infrared Spectrometer to measure lactose, fat and proteins in milk - request a quote

Customer inquiry:

what can you tell about potential use of AOTF to measure lactose, fat and proteins in milk?

Del Mar Photonics reply:

Yes, it is possible, see for example, publication below. Obtaining the spectrum takes a few seconds. It could be on-line, with a liquid flow-cell. One of the systems was built for the US Department of Agriculture.

Near infrared spectroscopy for biomonitoring: cow milk composition measurement in a spectral region from 1,100 to 2,400 nanometers (pdf)
R. Tsenkova*, S. Atanassova†, K. Itoh‡, Y. Ozaki§, and K. Toyoda*
*Department of Environmental Information and Bio-production Engineering, Kobe University, Kobe 657, Japan;
†Department of Mathematics and Physics, Thracian University, Stara Zagora 6000, Bulgaria;
‡Laboratory of Agricultural Process Engineering, Hokkaido University, Sapporo 060, Japan; and
§Department of Chemistry, Kwansei Gakuin University, Nishinomiya 662, Japan

ABSTRACT: The potential of near infrared spectroscopy (NIRS; 1,100 to 2,400 nm) to measure fat, total protein, and lactose content of nonhomogenized milk during milking and the influence of individual characteristics of each cow’s milk on the accuracy of determination were studied. Milk fractions were taken during milking, twice per month, for 6 mo. Samples were taken every 2nd and 4th wk at the morning and the evening milkings. Teatcups were removed at each 3 L of milk yield as determined with a fractional sampling milk meter. A total of 260 milk samples were collected and analyzed with an NIRSystem 6500 spectrophotometer with 1-mm sample thickness. Partial least squares (PLS) regression was used to develop calibration models for the examined milk components. The comparison with the reference method was based on standard error of cross validation (SECV). The obtained SECV varied from .107 to .138% for fat content, from .092 to .125% for total protein, and from .066 to .096% for lactose content, and the accuracy of the reference method (AOAC, 1990, method No 972.16) was .05% for all measured milk components. The obtained models had lower SECV when an individual cow’s spectral data were used for calibration. The reduction of SECV for each cow’s individual calibration, when compared with SECV for the set of all samples, differed with the different constituents. For fat content determination, the reduction reached 22.46%, for protein 26.40%, and for lactose 31.25%. This phenomena was investigated and explained by principle component analysis (PCA) and by comparing loading of PLS factors that account for the most spectral variations for each cow and the measured milk components, respectively. The results of this study indicated that NIRS (1,100 to 2,500 nm, 1-mm sample thickness) was satisfactory for nonhomogenized milk compositional analysis of milk fractions taken in the process of milking
Key Words: Milk, Fat, Protein, Lactose, Spectroscopy

AOTF Infrared Spectrometer - request a quote

Del Mar Photonics offer a handheld infrared spectrometer based on the acousto-optic tunable filter (AOTF). This instrument is about the size and weight of a video camera, and can be battery operated. This unique, patented device is all solid-state with no moving parts. It has been sold for a wide variety of applications such as liquid fuel analysis, pharmaceutical analysis, gas monitoring and plastic analysis.


• Portable
• High Speed
• NO moving parts
• Fiber Probe Option
• Infrared (1.2 – 2.5 µm)
• Diffuse reflectance and transmission


• Plastics identification RAVEN – Portable Plastic Identifier
• Pharmaceutical analysis
• Environmental Monitoring
• Research & Development
• Liquid fuel analysis
• Gas monitoring

Del Mar Photonics develop and supply dedicated AOTF Spectrometers. Send us the identification problem that you want to solve and we'll estimate suitability of AOTF technology for the job.

Del Mar Photonics, Inc.
4119 Twilight Ridge
San Diego, CA 92130
tel: (858) 876-3133
fax: (858) 630-2376
Skype: delmarphotonics