Effect of combined osmotic–ultrasound pretreatment on physical properties and surface microstructure of freeze‑dried apple cubes using a two‑dimensional wavelet transform approach

Baratian Ghorghi, Samira; Kashaninejad, Morteza; Heydari, Mohsen; Sarabandi, Khashayar; Vasiee, Alireza

doi:10.22104/ift.2026.8126.2270

Effect of combined osmotic–ultrasound pretreatment on physical properties and surface microstructure of freeze‑dried apple cubes using a two‑dimensional wavelet transform approach

Document Type : Research Article

Authors

Samira Baratian Ghorghi ¹

Morteza Kashaninejad ²

Mohsen Heydari ²

Khashayar Sarabandi ³

Alireza Vasiee ⁴

¹ PhD student of Food Science and Technology, Ferdowsi University of Mashhad (FUM)

² Assistant Professor, Department of Green Technologies in Food Processing, Research Institute of Food Science and Technology (RIFST), Mashhad, Iran

³ Assistant Professor, Department of Food Chemistry, Research Institute of Food Science and Technology (RIFST), Mashhad, Iran

⁴ Assistant Professor, Department of Food Safety and Quality Control, Research Institute of Food Science and Technology (RIFST), Mashhad, Iran

10.22104/ift.2026.8126.2270

Abstract

Osmotic solution concentration and ultrasonic pretreatment duration are crucial parameters influencing process efficiency and product quality in freeze-drying. Investigating the combined effect of these factors on the physicochemical properties of freeze-dried fruit is therefore essential. This study evaluated the impact of varying sucrose solution concentrations (40-60 wt%) and ultrasonic pretreatment times (10-50 min) on several characteristics of freeze dried apple cubes, including water loss after osmotic dehydration, weight loss after drying, water absorption capacity, textural properties (hardness and adhesiveness), overall color change (ΔE), surface shrinkage, edge parameters (EL and ED), and two-dimensional wavelet transform coefficients (LL, LH, HL, and HH). Response Surface Methodology (RSM) analysis revealed that increasing osmotic concentration significantly reduced surface shrinkage, overall color change, and edge parameters. Ultrasonic pretreatment duration significantly decreased hardness, while adhesiveness was unaffected by either variable. Wavelet analysis indicated that LL and HL subbands were significantly responsive to both factors, HH responded only to osmotic concentration, and LH showed no significant response. Overall, osmotic solution concentration played a dominant role in preserving visual quality and surface microstructure, whereas ultrasonic pretreatment primarily affected textural properties.The combined application of these two pretreatments may therefore improve several quality attributes of freeze dried apples simultaneously.

Graphical Abstract

Effect of combined osmotic–ultrasound pretreatment on physical properties and surface microstructure of freeze‑dried apple cubes using a two‑dimensional wavelet transform approach

Highlights

· Increasing osmotic solution concentration significantly reduced surface wrinkling, color change, and edge parameters of freeze-dried apple cubes.

· Pulsed treatment notably decreased apple cube hardness, while adhesion remained unaffected.

· Wavelet transform analysis revealed significant effects of osmotic concentration and pulsed time on the LL and HL subbands.

· The optimal combination of osmotic and pulsed treatments can improve both the appearance and surface microstructure of freeze-dried apples.

Keywords

Freeze-drying

Ultrasonication

Osmotic Dehydration

Image Processing

Wavelet Transform

Subjects

Food engineering

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