# Encapsulation of onion volatile compounds through spray drying process: Effects on volatile retention and structural modifications Results & Discussion Materials and Methods

Maryam Hanif, Ali Assifaoui, Elias Bou-Maroun, Céline Lafarge, Abdelhay El, Hassan Hajjaj, Hamid Mazouz

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Maryam Hanif, Ali Assifaoui, Elias Bou-Maroun, Céline Lafarge, Abdelhay El, et al.. Encapsulation of onion volatile compounds through spray drying process: Effects on volatile retention and structural modifications Results & Discussion Materials and Methods. Agriculture et monde Rural: L'Eau au coeur du développement durable, Apr 2025, Meknès, Morocco. . hal-05247296

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Submitted on 9 Sep 2025

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# Encapsulation of onion volatile compounds through spray drying process: Effects on volatile retention and structural modifications

Maryam HANIF¹, Ali ASSIFAQUI, Elias BOU-MAROUN², Céline LAFARGE², Abdelhay EL HARRAK¹, Hassan

1. Biotechnology and Valorization of Biological Resources Laboratory, Faculty of Science of Meknes, University of Moulay Ismail, P. B. 11201 Zitoune, Meknes, Morocco

2. Université Bourgogne Europe, Institut Agro, INRAE, UMR PAM, F-21000 Dijon, France.

## Introduction

* Onion (Allium cepa L.) is widely known for its flavor and medicinal properties. Onion cultivation covers an area of 25 392 ha, producing 802 388 tons in Morocco.

* The Fes-Meknes region contributes to more than 60% of the national production, with 454 600 tons (FAOSTAT 2022, FAO).

* Significant post-harvest losses (production losses reaching 40%) and loss of volatile compounds during drying (aroma and flavor).

* This study investigates the microencapsulation of volatile compounds present in red onion, aiming to enhance their stability, prolong their release, and preserve their bioactive properties for potential applications in food.

<figure><img src="image_2.png" /></figure>

<figure><img src="image_3.png" /><figcaption>Fes-Meknes Region</figcaption></figure>

Fresh onion

Drying process

Blanched dried onion

Optimization of onion drying technique

## Materials and Methods

<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

Fresh dried onion

<figure><img src="image_8.png" /></figure>

Loss of aroma
(volatile compounds)

<figure><img src="image_9.png" /></figure>

Fresh onion + β-cyclodextrin/ HM Pectin

<figure><img src="image_10.png" /></figure>

Spray dryer

<figure><img src="image_11.png" /></figure>

Encapsulated powder

<figure><img src="image_12.png" /></figure>

SPME GC-MS
Analysis

Sample incubation
(40°C/15min)

+

Fiber exposure(40°C/30min)

+

Fiber desorption
(240°C/5min)

Encapsulation of volatile compounds by spray drying

## Results & Discussion

<figure><img src="image_13.png" /></figure>

All spray-dried samples exhibited a marked reduction in volatile compounds compared to fresh onions. This loss may be due to either encapsulation or degradation, and solvent extraction is required to distinguish between the two.

The FTIR spectra show characteristic peaks of organosulfur compounds in fresh onion, particularly around 600–700 cm⁻¹ (C–S) and 1030–1070 cm⁻¹ (S=O), indicating the presence of sulfoxides and thiosulfinates. These peaks decrease notably in the spray-dried samples, especially with β-cyclodextrin, suggesting degradation or encapsulation of sulfur compounds during processing.

<figure><img src="image_14.png" /><figcaption>Fourier transform infrared spectroscopy (FTIR) spectra</figcaption></figure>

<figure><img src="image_15.png" /><figcaption>Comparison between fresh and spray dried onion + β-CD+ HM Pectin</figcaption></figure>

<figure><img src="image_16.png" /></figure>

## Conclusion

* Spray drying led to a reduction in volatile compound content across all samples compared to fresh onion. Therefore, solvent extraction is necessary to determine whether the aroma compounds were successfully encapsulated or degraded during the process.

* The FTIR spectra demonstrates that spray-drying, particularly with β-CD and pectin, significantly alters the molecular volatile profile of onion compared to its fresh state, indicating structural changes and interactions with added components.