3.1.4. Optical microscopy
Fig. 3a and b show the raw pumpkin tissue, where the structure of the cells can be seen clearly denoting cell wall integrity, separated by the intercellular fluid. Fig. 3c and d display the pumpkin subjected to blanching with subsequent dry infusion (control system, F3). Here, cell disintegration with a significant loss of intercellular space and intracellular fluid is notorious. Fig. 3e and f show the pumpkin tissue surface coated with starch-based coating where a disintegration of the structure with cell turgor loss is observed, in a similar way with that of the control system. It can be observed in Fig. 3f the interface between the vegetal matrix and the starch coating which seems well adhered. Unlike the starch-coated system, the k-carrageenan system shows a coating with a smooth and even surface that prevented the plant structure to be observed (Fig. 3g). Fig. 3h shows the pumpkin cylinder section where a separation among the vegetable matrix and k-carrageenan coating is clearly observed, suggesting a reduced adherence of the coating to the surface of the pumpkin. This observation also helps to explain the texture profile previously reported for F2.
3.2. Nutritional parameters
3.2.1. L-(+)-ascorbic acid content
The AA content of the different systems was determined during 18 days of storage at 8 °C. This period of time was appropriate to better accomplish the kinetic study. Fig. 4 shows the retention of AA content related to the initial AA content (Table 1) (AA/AA0) during storage. It was observed an AA content reduction for all systems studied. Fortified pumpkin coated with a starch coating containing iron showed the highest (p < 0.05) AA retention. Particularly, at 18 days (432 h) of storage, the AA/AA0 ratio for F1 was twice in comparison with that from F2 and F3.