Imaging and image analysis of freeze-dried cellular solids of gellan and agar gels

The fabricated gels are a form of novel structured food made by incorporation of nutritious ingredients. Agar and gellan gels having nutrients like ferrous sulfate, sucrose, mango pulp, whey protein concentrate and flaxseed powder were subjected to freeze-drying followed by image analysis of the cellular structure. The indices analyzed were the maximum/minimum dimensions, area and perimeter of cells, and the thickness of cell walls. Based on these primary data, other derived indices like roundness, equivalent diameter, elongation and compactness were determined. These nutrients affected the gel structure. Cells with smaller sizes were observed for sugar (98-296 μm) and mango pulp (115-433 μm) incorporated gels. The agar gels produced cells with a higher cell wall thickness (2.8-8.8 μm) compared to that of gellan gels (2.4-6.3 μm). The roundness values were between 0.539-0.666 and 0.453-0.728 for nutrient-enriched gellan and agar gels. Freeze-drying offered closed type cellular structure having five non-equal sides.