Aquaphotomics group of Biomeasurement Technology Laboratory at Kobe University, Japan, has started functioning as Aquaphotomics Research Department since April this year.

Our first publication, under the new name is opening a new venue of using Aquaphotomics for cell development studies. Therefore it deserves a somewhat special treatment. The article “Water Spectral Patterns Reveals Similarities and Differences in Rice Germination and Induced Degenerated Callus Development” has been published in MDPI’s Journal Plants few days ago, and can be downloaded at the links provided below.

The paper is a part of the Special Issue Seed Physiology focused on the latest findings in this research area. The topic may seem mundane and ordinary, but translated into the everyday language we could say the title of the paper is “what is wrong with this rice?” and “can I predict if this rice will grow normally or not?”. If only thing that we worry about is how to produce rice, it may not seem much. But, as the guest editor of the special issue nicely put it “Plants start out their life as a seed” – to look at seed is to look at the origin of life.

In the paper, we found out what happens in the seed that determines if it will develop normally into a nice rice plant, or if it will degenerate and form callus. The collaborative effort of aquaphotomics groups in Hungary and Japan, resulted in finding that the healthy seeds, despite many individual differences, will go through orchestrated phases in water structuring and restructuring during normal growth. On the other hand, the degenerated growth showed random changes in water structure, without any specific patterns, without phases, without common characteristics.

The promising results of SWNIR spectroscopy coupled with aquaphotomics suggest the strong potential of the technique for rice seed authentication and characterization, and beyond that, for detection of abnormalities in cell growth and development, which may offer excellent feedback for variety of early warning systems in different areas of research.

Abstract: https://www.mdpi.com/2223-7747/10/9/1832
PDF Version: https://www.mdpi.com/2223-7747/10/9/1832/pdf

Peanuts are one of the most common allergens, causing very severe allergic reactions. Peanut allergy accounts for 59% of the total number of food allergies and affects approximately 3 in every 100 children. The exact cause of allergy is not clear, but at least 11 specific proteins are recognized as peanut allergens. The allergen proteins can be made hypoallergenic after heating, which is called desensitization treatment. Essentially, this treatment can make modifications in protein structure, and the body no longer recognizes it as a pathogen, thus avoiding the allergic reaction.

The research group of Prof. Hengchang Zang at School of Pharmaceutical Sciences, Shandong University is dedicated to unraveling the relationship between the structure of proteins and their functionality, using aquaphotomics. Among many other biomolecules, this laboratory also explored the changes of the peanut allergen during heating process. In a recent publication, “Research on the Structure of Peanut Allergen Protein Ara h1 Based on Aquaphotomics” they applied aquaphotomics, using water as the probe to explain the detailed structural changes of peanut allergen protein Ara h1 during the heating process.

The first author of the article, published in June issue of Frontiers in Nutrition, is young Miss Mengqi Zhang, who is interested in applying Aquaphotomics to understand the structural information of natural products that could affect its function.

Aquaphotomics processing tools including principal component analysis (PCA), continuous wavelet transform(CWT), and two-dimensional correlation spectroscopy (2D-COS) were utilized for better understanding the thermodynamic changes, secondary structure, and the hydrogen bond network of Ara h1. The results showed that about 55 ^oC could be a key temperature which was the structural change point. During the heating process, the hydrogen bond network was destroyed, free water was increased, and the content of the protein secondary structure was changed. This discovery revealed the interaction between the water and Ara h1 from the perspective of water molecules and explained the effect of temperature on the Ara h1 structure and hydrogen-bonding system. Thus, it described a new way to explore the thermodynamic properties of Ara h1 from the perspective of spectroscopy and laid a theoretical foundation for the application of temperature-desensitized protein products.

The research was published June 18, 2021 in Frontiers of Nutrition, as a part of the research topic The Future Food Analysis. (https://doi.org/10.3389/fnut.2021.696355)

This research showed that during the heating process, the water spectra of the Ara h1 aqueous solution gradually shifted from high wavelength to low wavelength (Figure 1). The structures of Ara h1 and its spectra were changed under the influence of temperature. During the heating process, the strong hydrogen bonds were destroyed gradually, weak hydrogen bonds and other structures were formed. Under the influence of this effect, the water molecules were bounded by weak hydrogen bonds increasing. As the temperature rose again, the weak hydrogen bonds were also destroyed, the absorbance was weakened there, and the free water structure was formed. When the temperature was below 55^oC, the WAMACS of the aquagram was mainly biased towards high wavelengths. At this time, the hydrogen bond network structure of Ara h1 aqueous solution was stable, and the hydration was strong between water and the protein surface, which had little effect on the protein structure. When the temperature was higher than 55^oC, the aquagram tended to be at low wavelengths, the hydrogen bond network was broken, hydration was weakened, the structure of Ara h1 aqueous solution was greatly changed, and the protein precipitated and aggregated, and the hydrophobicity of the protein increased. It led to the decrease of sensitization ability.

The structures of Ara h1 had undergone major changes at around 55 ^oC, causing a rapid increase in the β-sheet content of the amide A /III (Figure 2 and Table 1). The α-helical content had been rising during the heating process. The secondary structures of the protein changed, and the side chain structures of the protein were broken, resulting in corresponding decreases of the sensitization ability of Ara h1.

Table 1  Characteristic absorption of Ara h1 aqueous solution in NIR spectra

number	Wavelength (nm)	characteristic absorption band
1	2060	the N-H bending vibration； the second overtone of an -OH bending vibration of water
2	2183	Amide B / II
3	2210	β-fold
4	2288	α- helix
5	2342	-CH2 side chain

A method for characterizing the regularity of protein structural changes without labeling was established through this research. Compared with the conventional analysis method for structural changes, it was easy to operate and had high sensitivity. At the same time, it was based on the interaction between the allergen protein Ara h1 and the water structure, revealed the temperature point of the Ara h1 protein structural changes. It laid a theoretical foundation for food processing technology, and also provided a new idea to explore the interaction of various molecules in the life system.

For more information about this research, please contact the corresponding authors.

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 .