Comparative analysis of different measurement techniques for assessing porous structure of food products dehydrated by several technologies

Several techniques are used to characterize the porous structure of dried foods, including helium pycnometry, mercury intrusion porosimetry (MIP), X-ray microtomography (micro-CT), and scanning electron microscopy. The strengths and weaknesses of each technique are critical to consider when selecting the appropriate one. Each method has strengths and limitations, yet discrepancies in measurements remain poorly understood. This study aimed to investigate the agreement and differences among these techniques in characterizing dried apples and pears dehydrated using hot air-drying (HAD), blast freeze-drying (BFD), and liquid nitrogen freeze-drying (FDN). The bulk density of freeze-dried apples and pears was approximately 0.14 and 0.18 g/ml, respectively, while HAD apples and pears averaged 0.54 g/ml and 1.12–1.29 g/ml. Particle densities measured by MIP and pycnometry were similar, but micro-CT produced different values. For HAD apples, porosity values were 62.3% (pycnometry), 59.6% (MIP), and 54.6% (micro-CT). For FDN pears, the values were 83.5%, 83.3%, and 70.9%, respectively, while for BFD pears, they were 86.1%, 86.0%, and 72.1%. The discrepancies in micro-CT results may stem from resolution limitations or image processing techniques. The findings of this study suggest that care should be taken when selecting and applying micro-CT to characterize dried food porous microstructures. To ensure the comprehensive characterization of dried food porosity, micro-CT should be combined with pycnometry or MIP. This combination provides a more accurate quantification of pore volume and size and a deeper and more reliable understanding of porous structures, leading to improved food quality, efficiency in production, and innovation in food processing technologies. • Various measurement techniques were used to characterize sample porous structure. • Different drying technologies have produced various porous properties. • Different fruits exhibited varying porous properties before and after drying. • Application of each measurement techniques brings benefit(s) and limitation(s). • Combining measurement techniques provides a comprehensive pore structures analysis.