Rapid measurement of macronutrients in breast milk: How reliable are infrared milk analyzers?

Abstract

SUMMARYBackground & aimsSignificant biological variation in macronutrient content of breast milk is an important barrier that needs to be overcome to meet nutritional needs of preterm infants. To analyze macronutrient content, commercial infrared milk analyzers have been proposed as efficient and practical tools in terms of efficiency and practicality. Since milk analyzers were originally developed for the dairy industry, they must be validated using a significant number of human milk samples that represent the broad range of variation in macronutrient content in preterm and term milk. Aim of this study was to validate two milk analyzers for breast milk analysis with reference methods and to determine an effective sample pretreatment. Current evidence for the influence of (i) aliquoting, (ii) storage time and (iii) temperature, and (iv) vessel wall adsorption on stability and availability of macronutrients in frozen breast milk is reviewed.MethodsBreast milk samples (n = 1188) were collected from 63 mothers of preterm and term infants. Milk analyzers: (A) Near-infrared milk analyzer (Unity SpectraStar, USA) and (B) Mid-infrared milk analyzer (Miris, Sweden) were compared to reference methods, e.g. ether extraction, elemental analysis, and UPLC-MS/MS for fat, protein, and lactose, respectively.ResultsFor fat analysis, (A) measured precisely but not accurately (y = 0.55x + 1.25, r2 = 0.85), whereas (B) measured precisely and accurately (y = 0.93x + 0.18, r2 = 0.86). For protein analysis, (A) was precise but not accurate (y = 0.55x + 0.54, r2 = 0.67) while (B) was both precise and accurate (y = 0.78x + 0.05, r2 = 0.73). For lactose analysis, both devices (A) and (B) showed two distinct concentration levels and measured therefore neither accurately nor precisely (y = 0.02x + 5.69, r2 = 0.01 and y = −0.09x + 6.62, r2 = 0.02 respectively). Macronutrient levels were unchanged in two independent samples of stored breast milk (−20 °C measured with IR; −80 °C measured with wet chemistry) over a period of 14 months.ConclusionsMilk analyzers in the current configuration have the potential to be introduced in clinical routine to measure fat and protein content, but will need major adjustments.

Preterm human milk macronutrient concentration is independent of gestational age at birth

“…In this study we employed the MIRIS Human Milk Analyser, which requires only 2 mL of breast milk for investigation, making it feasible for bedside use. Silvestre et al 27 and Fusch and coworkers28 tested the reliability of the infrared milk analysers (including MIRIS Human Milk Analyser) using reference milk analysis, and despite some limitations they stated that midinfrared measurement of human milk macronutrients revealed good linearity and precision and reached acceptable results for clinical use.…”

Protein Evolution of Human Milk

“…Additionally, we are not the only ones to raise the question over the accuracy of data generated by mid-infrared spectroscopy. Many researchers have posed a similar question and published their independent observations [19][20][21] . To overcome this challenge, we explored the BCA kit assay that also requires a very low volume of sample for analysis and could also be considered a fairly high-throughput setup.…”

Preterm human milk composition: a systematic literature review

“…The strength of the calibration depends on the reference chemistry used and the number and range of samples (63) . Homogenisation is an important step in preparing milk samples as it decreases the variability in fat globule size and subsequent light-scattering effect of larger globules, improving the accuracy of measurement (25) . Reducing the diameter of the fat globule to <3 µm can be achieved through either manual or ultrasonographic methods; however, utilising an ultrasound processor is associated with high measured values for N, energy and particularly fat and lactose (69) .…”

“…Fusch et al (25) highlighted that the near-and mid-IR spectroscopy equipment had variable accuracy when calibrated against micro analyses methods (0·2 g/100 ml for protein, 0·5 g/100 ml for lipid and inaccurate measurements of lactose), which can be significant when feeding at low volumes. These values were similarly found in another study reviewing mid-IR spectroscopy, with lactose again being overestimated (26) .…”

“…Bedside milk analysis with the potential for targeted fortification is under development, with a recent study evaluating the accuracy of using IR analysis for small aliquots of milk, clinically relevant due to the smaller volumes of milk sometimes expressed by preterm mothers (25) . Fusch et al (25) highlighted that the near-and mid-IR spectroscopy equipment had variable accuracy when calibrated against micro analyses methods (0·2 g/100 ml for protein, 0·5 g/100 ml for lipid and inaccurate measurements of lactose), which can be significant when feeding at low volumes.…”