Food surface characterization by scanning electron microscopy and fractal analysis: A review

Surface characterization of food products is critical for understanding their physical, chemical, and biological properties, which have a direct impact on quality, safety, and consumer acceptability. Scanning electron microscopy (SEM) paired with "fractal analysis" has developed as an effective method for studying food surfaces at the micro- and nanoscales. This review investigated the use of SEM to examine the topographical features of various food items, such as fruits, vegetables, grains, and processed foods, emphasizing the importance of surface morphology in determining texture, moisture retention, and overall product quality during consumption and storage. Fractal analysis, together with SEM, is a quantitative approach for describing the complexity of foods surface structures. Fractal and multifractal analysis using SEM images yields a numerical description of surface roughness, complexity, and heterogenicity. The combination of SEM with fractal analysis not only allows for a more in-depth study of food surface characteristics, but it also helps to optimize food processing procedures. Positive correlations between processing (drying, frying, freezing) time, fractal dimension, and surface openings have been established. Fractal dimension of various food items (fruit, vegetable, crispy product, powder, extrudate product, puffed food, frozen product, fish, etc.) and their characteristics quality attributes have been found expressively interlined. The outcomes of multifractal analysis (Singularity and Rényi spectra) successfully characterized heterogenicity in foods surface micro-structure. SEM image-based fractal analysis, which reveals the subtle links between surface morphology and food attributes, showed potential to significantly expand food science and technology, paving the door for advances in food processing and quality management.