Acquisition strategies for fermentation processes with a low-cost miniaturized NIR-spectrometer from scratch: Issues and challenges

In recent years, low-cost miniaturized NIR spectrometers have become extremely useful for quantification, discrimination and classification problems in many field and industrial application domains. The dairy industry is showing particular interest in using portable near-infrared spectroscopy as a quality assessment method or process analytical tool but, when coming to at-line, in/on-line possibilities there is no effective and explanatory literature that presents how to approach analytical method development, even though handheld spectroscopy is invaluable to evaluate fermentation as a crucial dairy operation. In this study the potential and limits of a handheld spectrometer (1350-2550 nm) in gaining information about a dairy fermentation process were investigated. Kefir is a fermented dairy product of rising interest, due to its health beneficial effects and the complexity of the process which involved chemicals and physical trans-formations that bring to the final product starting from milk by inoculating the so-called "kefir grains"; although the chemistry and physics involved are convoluted, the process itself can be easily conducted at home. Handheld spectrophotometers could be helpful to determine early stages of fermentation, before visual changes occur; being a helpful tool for the healthy citizen. Spectral characteristics and variability related to different experimental set-up were explored first, for the starting and ending products and then, during the fermentation. Semi-skimmed milk was used as fermentation media. After adding the kefir grains, spectra were acquired at interval times during the evolution of the process that was carried out under temperature control. To catch all the information included in the spectra and to investigate the possibilities of paving the way for process monitoring, different approaches were employed.