No abstract

BACKGROUND Duckweed has been considered as an alternative future food material as a result of its high nutritional values, although it also has a high moisture content resulting in a short shelf life. Moisture sorption isotherms are used to design dehydration and storage conditions to prolong the shelf life food products. To date, information regarding the sorption isotherm of duckweed has not been reported. Scanning electron microscopy (SEM) is frequently used to study food microstructure. However, this technique has to be performed under high‐vacuum conditions and takes a long time. In the present study, two‐photon imaging microscopy was selected to investigate the microstructure of dried duckweed instead of SEM. RESULTS Among five sorption isotherm models, the Peleg model gave the highest goodness of fit. The monolayer moisture content (M0) of duckweed was in the range 7.43–7.92% dry basis (d.b.) and 8.87–8.86% d.b. for the GAB and BET multilayer kinetic models, respectively. The moisture changing behavior at each relative humidity step could be described by two exponential and reaction order kinetics. A clear cell structure (hexagonal shape) and stomata, as well as structural images (both 2D and 3D), were obtained using the two‐photon microscopy technique. CONCLUSION The Peleg model best described the moisture sorption behaviors of dried duckweed and the shape of sorption isotherms were classified as type III isotherm. The M0 of dried duckweed ranged from 7.43 to 8.86% d.b. Two‐photon microscopy was a potent tool for investigating the microstructure and composition of dried duckweed. © 2021 Society of Chemical Industry.

No abstract

This research aimed to investigate the effects of atmospheric storage condition (at 0.33 and 0.75 water activity, aw) and storage time on the qualities of Khnom La. The sorption isotherm also was studied. The moisture content of Khanom La was adjusted using the saturated salt solution at different relative humidity levels. The sorption isotherm, hardness, color and peroxide values of Khanom La were then evaluated. The sorption isotherm data of Khanom La was fitted to BET and GAB models. The experimental result showed that monolayer values of the sample were in the range of 3.15 to 3.39 g water/ 100 g dry solids when its water activity was in the range of 0.11 to 0.84. Khanom La samples were stored in closed containers at an ambient temperature either at 0.33 and 0.75 aw for 35 days. Lightness and hardness of Khanom La decreased, while the redness yellowness and peroxide value of those desserts increased with storage time. The effects were more pronounced when samples were stored at 0.75 aw. The results indicated that crispy Khanom La might retain the desirable attributions during days of storage in a sealed container at low water activity. HIGHLIGHTS The major factors affecting the qualities and water sorption isotherm of Khanom La after frying are storage conditions (such as water activity of atmospheric storage environment and storage time) The problem of fried products is the deterioration of oil over time during storage, involving a complex pattern of the peroxide and oxidation reactions which are related to their water activity The hardness of Khanom La reduced, while the peroxide and chromatic values increased with an increase of water content more than the monolayer value of GAB fitting, indicating the degradation of products progressively during storage GRAPHICAL ABSTRACT