Modified Versus Producer Milk Calibration: Mid-Infrared Analyzer Performance Validation

Abstract

Our objective was to determine the validation performance of mid-infrared (MIR) milk analyzers, using the traditional fixed-filter approach, when the instruments were calibrated with producer milk calibration samples vs. modified milk calibration samples. Ten MIR analyzers were calibrated using producer milk calibration sample sets, and 9 MIR milk analyzers were calibrated using modified milk sample sets. Three sets of 12 validation milk samples with all-laboratory mean chemistry reference values were tested during a 3-mo period. Calibration of MIR milk analyzers using modified milk increased the accuracy (i.e., better agreement with chemistry) and improved agreement between laboratories on validation milk samples compared with MIR analyzers calibrated with producer milk samples. Calibration of MIR analyzers using modified milk samples reduced overall mean Euclidian distance for all components for all 3 validation sets by at least 24% compared with MIR analyzers calibrated with producer milk sets. Calibration with modified milk sets reduced the average Euclidian distance from all-laboratory mean reference chemistry on validation samples by 40, 25, 36, and 27%, respectively for fat, anhydrous lactose, true protein, and total solids. Between-laboratory agreement was evaluated using reproducibility standard deviation (s R ). The number of single Grubbs statistical outliers in the validation data was much higher (53 vs. 7) for the instruments calibrated with producer milk than for instruments calibrated with modified milk sets. The s R for instruments calibrated with producer milks (with statistical outliers removed) was similar to data collected in recent proficiency studies, whereas the s R for instruments calibrated with modified milks was lower than those calibrated with producer 2833 milks by 46, 52, 61, and 55%, respectively for fat, anhydrous lactose, true protein, and total solids.

Total Protein Methods and Their Potential Utility to Reduce the Risk of Food Protein Adulteration

“…After MIR equipment is calibrated the method is simple and rapid (0.5 to 2 min per sample). Calibration strategies include analysis of at least 8 samples covering the expected food matrix range that has been previously analyzed for protein using chemical reference methods (Kaylegian and others 2006). The primary reported application for this method is fluid milk analysis, and it has been adopted by AOAC International (2005) as method 972.16.…”

“…The accuracy of this method for milk protein analysis depends on instrument, calibration uncertainty, and sample deterioration (Kaylegian and others 2006). The AOAC method for this procedure indicates that a high level of accuracy is possible with a mean error of less than 0.05% (AOAC International 2005).…”

“…The precision of mid‐IR measurements depends on the selection of a suitable sample. Although manufacturer‐supplied validation samples achieved a reproducibility of 0.028%, optimized validation samples improved the reproducibility to 0.01% (Kaylegian and others 2006). AOAC International (2005) method 972.16 for the mid‐IR determination of protein and other constituents of milk includes reproducibility of ≤ 0.02% as an acceptance criterion.…”

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

“…These findings were attributed to the modified milk set's larger component concentration ranges, its more-even distribution of concentrations within those ranges, and its relative lack of collinearity among components of interest (i.e., fat and protein) compared with the producer milk sets. Calibration improvements were verified during a validation study (Kaylegian et al, 2006b), which indicated that using the modified milk set for calibration reduced fat, lactose, protein, and total solids reproducibility values (i.e., the differences between 2 MIR instruments measuring the same sample) by 46, 52, 61, and 55%, respectively.…”

Infrared Spectrophotometry, Infrared Spectroscopy and Infrared Spectrometry in Diary Spectral Qualimetry: Contemporary Ideas and Retro-Engineering

“…В связи с этим целесообразно отметить воздействие "стерических" протекторов на конформационные и физико-химические свойства молока и молочных компонент, регистрируемое также и с помощью инфракрасной спектроскопии -известны работы по Фурье-ИК-исследованию систем с молочной липазой в обращенных мицеллах [61], и изучению молекулярного уровня организации бета-лактоглобулинов при взаимодействии с фосфолипидными бислоями [62], выполняющими подобную функцию. Более того, протеолиз и липолиз, сопровождающиеся, как известно, конформационными изменениями, используют для специфической калибровки анализаторов молока ближнего инфракрасного диапазона [63], наряду с другими принципами калибровки анализаторов в инфракрасном диапазоне, разрабатываемыми той же международной группой [64][65][66], что дает возможность рассматривать конформационные изменения молочных компонент как весьма достоверный принцип контроля и автоматической юстировки в ИК-диапазоне при анализе молока и молочных продуктов.…”