ATR-MIR spectroscopy to predict commercial milk major components: A comparison between a handheld and a benchtop instrument

There is a growing need of measurement technologies that can be used close to the sample source and optical spectroscopy is an excellent example of this genre of technology: from the lab to the field. This study investigates the possibility to quantify the major components and to detect the presence or absence of lactose in commercial milks with ATR-MIR spectroscopy. We explored the possibility to use a portable and economical ATR-MIR instrument, comparing the results with a benchtop system. Commercial milk samples from Italy, Switzerland and Spain were chosen covering the maximum range of variation for protein, carbohydrate and fat content. The analytical protocol was optimized to make it as fast and useable as possible for both instruments, from the sample pretreatment to the instrumental parameters. Multivariate calibration was used to correlate the recorded spectra to the content of the major milk components, while a classification was done in order to classify samples with or without lactose. A comparison was performed between the predictive capabilities of the models built with different data pretreatments, different variable selection methods and different validation systems to obtain the best results and to assure robust models.