It is a pleasure to announce the recent publications which could be of immense importance for aquaphotomics researchers. Both publications originate from the group of Jean-Michel Roger, (INRAE, UMR ITAP, Montpellier University and ChemHouse Research Group, France) one of the world experts in preprocessing and analysis of spectral data.  The first author on both publications is Alexander Mallet, a young PhD researcher, who is working on revealing both physical and chemical effects of the water on the near infrared spectra, and who spent few months in the Biomeasurement Technology Laboratory, of Prof. Dr. Tsenkova at Kobe University, last year.  The works are of particular importance for correct spectroscopic assignments, correct modeling and interpretation of the structure of water. 

The first publication describes the results of the dynamic study of near-infrared spectra acquired during a drying process with a focus on the first overtone OH absorbance region:    

Mallet, A., Tsenkova, R., Muncan, J., Charnier, C., Latrille, É., Bendoula, R., Stayer, J.P. & Roger, J. M. (2021). Relating Near-Infrared Light Path-Length Modifications to the Water Content of Scattering Media in Near-Infrared Spectroscopy: Toward a New Bouguer–Beer–Lambert Law. Analytical Chemistry, 93(17), 6817-6823. 

https://doi.org/10.1021/acs.analchem.1c00811

The second one continues to analyze and compare moisture content effects in one comprehensive experiment with a wide variety of biochemical and physical types in order to understand water effects and how they relate to the substrate properties. 

Mallet, A., Charnier, C., Latrille, É., Bendoula, R., Steyer, J. P., & Roger, J. M. (2021). Unveiling non-linear water effects in near infrared spectroscopy: A study on organic wastes during drying using chemometrics. Waste Management, 122, 36-48.

https://doi.org/10.1016/j.wasman.2020.12.019

Both publications are heartily recommended and we expect to see their influence on aquaphotomics development. Most sincere congratulations to French group from the Aquaphotomics Research Department in Kobe. We are eagerly awaiting more. 

We are very pleased to announce that a new article on Aquaphotomics has been published in “Sensors” (Volume 21, Issue 1, December 2020).

“Real-Time Monitoring of Yogurt Fermentation Process by Aquaphotomics Near-Infrared Spectroscopy” by Jelena Muncan, Kyoko Tei, Roumiana Tsenkova.

“Automated quality control could have a substantial economic impact on the dairy industry. At present, monitoring of yogurt production is performed by sampling for microbiological and physicochemical measurements. In this study, Near-Infrared Spectroscopy (NIRS) is proposed for non-invasive automated control of yogurt production and better understanding of lactic acid bacteria (LAB) fermentation. UHT (ultra-high temperature) sterilized milk was inoculated with Bulgarian yogurt and placed into a quartz cuvette (1 mm pathlength) and test-tubes. Yogurt absorbance spectra (830–2500 nm) were acquired every 15 min, and pH, in the respective test-tubes, was measured every 30 min, during 8 h of fermentation. Spectral data showed substantial baseline and slope changes with acidification. These variations corresponded to respective features of the microbiological growth curve showing water structural changes, protein denaturation, and coagulation of milk. Moving Window Principal Component Analysis (MWPCA) was applied in the spectral range of 954–1880 nm to detect absorbance bands where most variations in the loading curves were caused by LAB fermentation. Characteristic wavelength regions related to the observed physical and multiple chemical changes were identified. The results proved that NIRS is a valuable tool for real-time monitoring and better understanding of the yogurt fermentation process.”

The article can be viewed and downloaded at https://doi.org/10.3390/s21010177.

We are very pleased to announce that a new article on Aquaphotomics has been published in “Food Control” (Volume 122, April 2021, 107805).

“Near infrared aquaphotomics study on common dietary fatty acids in cow’s liquid, thawed milk” by Jelena Muncan, Zoltan Kovacs, Bernhard Pollner, Kentarou Ikuta, Yoshihisa Ohtani, Fuminori Terada, Roumiana Tsenkova.

“This study was aimed at two objectives: 1) explore the possibility of near infrared (NIR) spectroscopy to determine the content of common dietary fatty acids (FAs) and fat content in cow’s liquid milk for better individual cow’s feed management; 2) using aquaphotomics obtain better understanding of interaction between water molecular structure and FAs and gain more insight into their functionality.
For these purposes, 252 milk samples were collected from 9 cows during 14 weeks and FAs content measured using gas chromatography as a reference method. Applying aquaphotomics NIR spectral analysis, quantification was attempted using 1300–1850 nm region where both water and FAs absorbance bands are located. The results showed possibility of quantification for 8 common dietary FAs which was more accurate when spectral region was narrowed to 1600–1800 nm. In the external validation, good predictions (R²> 0.75, RPD>1.5), were obtained for caproic and caprylic and acceptable for capric, lauric, myristic, myristoleic, palmitoleic and oleic acid (0.55<R²<0.75, RPD>1.5). Interpretation of influential variables in regression models revealed contribution of water absorbance bands related to protonated and hydration water, which originate from the water-FAs interaction and are important for their self-organization into assemblies with different morphologies.”

The article can be viewed and downloaded at https://doi.org/10.1016/j.foodcont.2020.107805 .

We are very pleased to announce that a new article on Aquaphotomics has been published in “Journal of Chemometrics” (23 June, 2020).

“Near-infrared multivariate model transfer for quantification of different hydrogen bonding species in aqueous systems” by Jun-Li Xu, Ronan M. Dorrepaal, Jose Martinez-Gonzalez, Roumiana Tsenkova, Aoife A. Gowen.

It is challenging to achieve consistent quantification of hydrogen-bonded water species by fitting Gaussian bands on spectra collected from different instruments, especially when the spectral resolution is low. Therefore, this work aims to propose a near-infrared (NIR) multivariate calibration model transfer method to obtain reliable, consistent, and reproducible results from different spectroscopic instruments. A composite method of Gaussian deconvolution, multivariate curve resolution-alternating least squares (MCR-ALS), and partial least squares (PLS) was developed to quantify five water species (labeled as C1, C2, C3, C4, and C5), respectively, assigned to non-hydrogen-bonded, singly hydrogen-bonded, doubly and triply hydrogen-bonded species, distorted icelike structures in the liquid phase, and fully hydrogen-bonded species showing ice-like structure. Primary instrument (iS50) was selected due to the highest spectral resolution and spectra (7500–5845 cm−1 with spectral resolution of 0.5 cm−1) were acquired from four types of salt solutions. The developed PLS model yielded a high prediction performance when applied on two independent prediction sets with R2P higher than 0.95 and RMSEP less than 0.009 for prediction of C1-5. Model built with primary spectra was successfully transferred to spectra of secondary instrument (iN10), producing RMSEP less than 0.010. Transferred model applied on secondary instruments (NIRECO and MPA) showed that fully H-bonded species in deionized water decreased as temperature increased, while non-hydrogen-bonded and singly hydrogenbonded demonstrated an opposite temperature dependence. Our results confirmed that it is promising to transfer the calibration model from a sophisticated spectrometer to a simple spectroscopic instrument in terms of quantification of hydrogen-bonded water species.

The article can be viewed and downloaded at https://doi.org/10.1002/cem.3274 .

We are very pleased to announce that a new article on Aquaphotomics has been published in “Substantia” as part of the Special Issue Article (Substantia Vol 3 No 2 Suppl. 3 2019).

“Aquaphotomics – Origin, concept, applications and future perspectives” by Everine B. van de Kraats, Jelena Muncan, and Roumiana Tsenkova.

Aquaphotomics is a novel scientific discipline which has made rapid progress in just 14 years since its establishment in 2005. The main novelty of this field using spectroscopy is placing the focus on water, as a complex molecular matrix and an integral part of any aqueous system. Water is sensitive to any change the system experiences – external or internal. As such, the molecular structure of water revealed through its interaction with light of all frequencies becomes a source of information about the state of the system, an integrative marker of system dynamics.

This novel field shifts the paradigm of seeing water in a system as a passive, inert molecule to one which can build various structures with various functionalities, giving water an active role in biological and aqueous systems. Owing to the high sensitivity of hydrogen bonds, the water molecules are incredibly adaptive to their surroundings, reshaping and adjusting in response to changes of the aqueous or biological systems, and this property in aquaphotomics is utilized as a key principle for various purposes of bio-measurements, bio-diagnostics and biomonitoring.

This paper will present the origin and concept of aquaphotomics and will, through a series of examples of applications, illustrate many opportunities and directions opened for novel scientific and technological developments.

The article can be viewed and downloaded at https://doi.org/10.13128/Substantia-702 .