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Valentin, A. A., Robert, N. B., & Sawaliho, B. E. H. (2021). DFT Investigation of Carbon Dioxide Effects with Temperature on Hydrated Tetra and

Penta-Saccharide Complexes. European Journal of Applied Sciences, 9(5). 142-161.

URL: http://dx.doi.org/10.14738/aivp.95.10896

implements different cultivation techniques to improve its productivity. However, it struggles

to cover the needs of its inhabitants; post-harvest losses are quantified at nearly 30% of

production [2]. The theoretical chemistry team wants to suggest ways to increase the green life

of this fruit. Its researchers are trying to understand the degradation modalities of mass- produced foods. Subsequently, they recommend the properties of candidate molecules that

could reduce these huge losses. Before, it presents and discuss preceding work.

Starch represents the main constituent of green plantain. It consists of two polysaccharides,

amylose and amylopectin. These polymers comprise chains of α-D-glucose linked by osidic

bridges. Water hydrolyzes them into disaccharides or monosaccharides during ripening [3.4].

It establishes hydrogen bonds with the hydroxyls of D-glucose [5.6]. It contributes to its rapid

alteration. The team’s previous work sheds light on this mechanism. Temperature also acts role

in this process.

Its increase accelerates the maturing of the banana. Cold plays an important role in retarding

its metabolism [7], [8]. It prolongs the duration of the green state and maintains the quality of

the fruit [9, 10, 11]. Furthermore, carbon dioxide participates in the preservation process of

bananas in a controlled atmosphere [12.13]. Its enzymatic hydrolysis decreases if stored in an

environment with 10% CO2 [14]. But previous works reveal that water, temperature, and

carbon dioxide constitute three factors that can elucidate the degradation of green bananas.

They remain silent on the mechanisms shaping their effects. This research wants to fill this gap.

It targets to answer the following question:

What are the mechanisms underlying the effects of temperature and carbon dioxide on

green bananas?

This work aims to explain the role of temperature and carbon dioxide in starch degradation. It

generates and analyzes geometric, thermodynamic, and spectroscopic parameters using

quantum calculations on complexes of four (AM4G) and five (AM5G) amylose synthons. It

calculates and discusses them for the AM4G-H2O, AM4G-H2O-CO2, AM5G-H2O, and AM5G-H2O- CO2 complexes. It performs the calculations at 298 K and 286 K. The article includes four main

parts.

The first one follows this introduction. It describes the compounds and the method of study.

The second presents the results. The third comments on these. It explains the effects of

temperature and CO2 on geometric, thermodynamic, and spectroscopic parameters of the

complexes and hydrogen bonds (HB) related to the formation of these. A conclusion closes this

presentation in the fourth.

COMPOUNDS AND METHOD

This section deals with the procedures of the calculations. First, it presents the polysaccharides

under study and their geometrical, energetic, or spectroscopic parameters.

Compounds

Starch comprises two polysaccharides, amylose, and amylopectin. The first corresponds to a

linear polymer of D-glucose in α (1–4). The second is another from D-glucose (1–4). It has

branches in α (1–6) amylose. This study focuses on complexes of four or five D-glucose units

with water. They have three and four osidic bridges respectively. Figure 1 shows the 3D

molecular structure of AM4G (four synthons) and AM5G (five synthons). All oxygen are sp3

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European Journal of Applied Sciences (EJAS) Vol. 9, Issue 5, October-2021

Services for Science and Education – United Kingdom

hybridized. The bridge is numbered from 1 to 3 for first polysaccharides and to 4 for the second

one. These numerals also correspond to the names of the different HB complexes. Quantum

Methods permit identifying them.

Method

All calculations perform using the ONIOM (Own N-layered Integrated Molecular Orbital)

method developed by Morokuma and all [15]. Our previous work utilizes it to highlight the HB

sites of amylose and amylopectin [16]. The ONIOM method suits here for this reason. It consists

of splitting any complex into two parts. Each part behaves at different levels of calculation

(figure 2).

For AM4G-H2O and AM5G-H2O, the water, and the carbons of the osidic bridge and their

hydrogen constitute the first (internal) part. This division makes it possible to describe the HB

precisely. The calculations carry out at a high level (B3LYP/6–311++G [d, p]). The diffuse and

polarization functions consider the isolated pairs of oxygen and their interactions with the

hydrogen in water. For the second (external) part, the semi-empirical AM1 approach helps to

capture the remainder of the complex environment in a less rigorous way.

AM4G AM5G

Fig. 1: 3D image of the AM4G and AM5G

Fig. 2: Calculation scheme according to the ONIOM method