Precalibration Evaluation Procedures for Mid-Infrared Milk Analyzers

Abstract

The purpose of this paper is to present a detailed account of the precalibration procedures developed and implemented by the USDA Federal Milk Market Administrators (FMMA) for evaluating mid-infrared (MIR) milk analyzers. Mid-infrared analyzers specifically designed for milk testing provide a rapid and cost-effective means for determining milk composition for payment and dairy herd improvement programs. These instruments determine the fat, protein, and lactose content of milk, and enable the calculation of total solids, solids-not-fat, and other solids. All MIR analyzers are secondary testing instruments that require calibration by chemical reference methods. Precalibration is the process of assuring that the instrument is in good working order (mechanically and electrically) and that the readings before calibration are stable and optimized. The main components of precalibration are evaluation of flow system integrity, homogenization efficiency, water repeatability, zero shift, linearity, primary slope, milk repeatability, purging efficiency, and establishment of intercorrection factors. These are described in detail and apply to both filter-based and Fourier transform infrared instruments operating using classical primary and reference wavelengths. Under the USDA FMMA Precalibration Evaluation Program, the precalibration procedures were applied longitudinally over time using a wide variety of instruments and instrument models. Instruments in this program were maintained to pass the criteria for all precalibration procedures. All instruments used similar primary wavelengths to measure fat, protein, and lactose but there were differences in reference wavelength selection. Intercorrection factors were consistent over time within all instruments and similar among groups of instruments using similar primary and reference wavelengths. However, the magnitude and sign of the intercorrection factors were significantly affected by the choice of reference wavelengths.

Effectiveness of mid-infrared spectroscopy to predict fatty acid composition of Brown Swiss bovine milk

“…Mid-infrared spectroscopy (MIR) is widely used in official milk recording schemes to determine the chemical composition of milk (Lynch et al, 2006). Its potential has also been demonstrated to predict coagulation properties of bovine milk (Dal Zotto et al, 2008;De Marchi et al, 2009b), detail milk protein composition (De Marchi et al, 2009a) and -E-mail: mauro.penasa@unipd.it acetone content for the detection of subclinical ketosis (Heuer et al, 2001).…”

A novel statistical approach to detect differences in fat and protein test values among mid-infrared spectrophotometers

“…This process is known as precalibration and Lynch et al (2006) provide a detailed description of these procedures for MIR instruments used to test fluid milk samples. During precalibration, the instrument's flow system, homogenizer, repeatability on water, zero shift (cuvette condition), linearity, primary slope, repeatability on milk, purging efficiency, and intercorrection factors are inspected .…”

Glutamine and glutamate (AminoGut) supplementation influences sow colostrum and mature milk composition

“…Samples were either immediately chilled on ice for proximate and cell analysis or deproteinized with an equal volume of 10% (v/v) perchloric acid, followed by neutralization before amino acid analysis. Proximate analyses, total protein, lipid, lactose and total solids, were carried out at the Laboratory of Management Program of the Northeast Brazil Dairy Herds (PROGENE), UFRPE, using Fourier transformed infrared spectroscopy (FTIR) (Bentley 2000 Lactoscoper) as documented for the determination of milk composition (Lynch et al, 2006;Rodriguez-Saona and Allendorf, 2011), milk fat (Soyeurt et al 2006), and milk protein (MCP) (Bonfatti et al, 2011a,b;Díaz-Carrillo et al, 1993;De Marchi et al, 2009,a,b). The somatic cell count (SCC) was determined by the Fossomatic SCC method (FSCC) using fluorescence flow cytometry (SomaScope MKII/Somacount 300, Delta Instruments), as validated by Gonzalo et al (2004) for ovine milk.…”