The microstructure of potato was studied by different microscopic techniques. The methods used were bright field (BFM), fluorescence (FM), confocal laser scanning (CLSM), scanning electron (SEM), and transmission electron (TEM) microscopy. The focus was on starch and structure of cells before and after cooking. Also components such as cell walls, protein, and pectin were identified by using different staining procedures. The use of different methods improved the interpretation of results and facilitated the identification of possible artifacts. The distribution of starch and proteins differed between tuber parts but also between adjacent cells. The amount of starch in individual cells clearly affected the shape of cells in cooked potatoes. Starch and cell shape were clearly visualised by all methods but TEM, which due to the high magnifications was better suited for studying cell walls and heat promoted separation of cells. CLSM was the preferred method for studying starch with minimal impact on the cell structure since artificial effects could be induced during preparation.

Cooking, microstructural and textural characteristics from four New Zealand potato cultivars (Agria, Nadine, Moonlight, and Red Rascal) were studied. Potatoes from the waxy cultivar, Nadine, showed lowest dry matter and starch content and also had highest cooking time compared to the other cultivars. The total colour difference, ΔE, indicative of browning and darkening during storage (for 1 h) of the peeled potatoes was observed to be highest for Red Rascal, followed by Nadine and was lowest for Agria. Light (LM) and confocal scanning electron (CSLM) micrographs revealed Moonlight and Red Rascal raw potato parenchyma cellular structure to be well integrated, showing compact hexagonal cells. Raw tubers from these cultivars also exhibited higher hardness and cohesiveness, as observed using texture profile analysis (TPA). Moonlight potato parenchyma retained cell wall outline after cooking and its cells were observed to be completely filled with gelatinised starch matrix, whereas the cellular structure of Nadine potato parenchyma was completely disintegrated after cooking. TPA results of cooked potatoes agreed well with these microstructural observations, with Moonlight cooked potatoes showing highest cohesiveness and hardness. The cell wall of parenchyma cells was observed to degrade partially upon cooking of potatoes, resulting in loosening of the cell wall microfibrils, as observed using transmission electron microscopy (TEM) of a selected potato cultivar. Also, the cell wall decreased in thickness after cooking. The remains of the primary cell wall along with some electron dense granular structures were observed floating in the cytoplasmic starchy matrix in potato tuber parenchyma cells.

The presented work is continuation of researches on cellular structure of potato tuber parenchyma tissue. It concerns changes of the potato tuber cellular structure parameters during storage. Tubers of two varieties: Andromeda and Pasat were tested, 5 tubers for each variety and storage period. Cylindrical samples 10 mm in diameter and 1 mm thick were taken out of two types of tissues − potato pith and internal parenchyma from each tuber. Images of the tissues in natural state were taken with optical confocal microscope. Technique elaborated earlier by the author was used to obtain images containing number of cells sufficient for statistical analysis. As the result of analysis performed following mean values parameters of cell size and shape were used: surface area of plane section of the cell A (μm2) and cell elongation E. The results show differences between cell size for potato pith and internal parenchyma Andromeda variety and storage period. For this smaller values of the area ...