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Osmotic dehydration of apple was modeled considering the mechanisms involved in the solutes transfer within the plant matrix: impregnation and diffusion. The model mathematical writing includes the impregnation layer thickness, the diffusion thickness, a water bulk flow and the convective resistance. Apple cylinders were dehydrated at 30, 50 ° C and 30, 50 ° Brix and a motion of 0.15 m/s. The Reynolds number was of 250 for 30°C-30°Bx and 500 for 50°C-50°Bx. Schmidt numbers was of 4000 for 30 ° C-30 ° Bx and 4200 for 50 ° C-50 ° Bx.Keywords: transfer; solute; impregnation; osmotic dehydration.

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While various mechanisms have been proposed for the water transfer during osmotic dehydration (OD), little progress has been made to understand the mechanisms of solute transfer during osmotic dehydration. The transfer of solutes has been often described only by the diffusion mechanism; however, numerous evidences suggest the participation of a variety of mechanisms. This review deals with the main issues of solute transfer in the OD of vegetables. In this context, several studies suggest that during OD of fruits and vegetables, the migration of solutes is not influenced by diffusion. Thus, new theories that may explain the solute transport are analyzed, considering the influence of the plant microstructure and its interaction with the physicochemical properties of osmotic liquid media. In particular, the surface adhesion phenomenon is analyzed and discussed, as a possible mechanism present during the transfer of solutes in OD.

Because abiotic stresses pose significant challenges to the growth and productivity of crops, the development of plants with greater survival and growth when exposed to unfavorable situations is an objective of several research groups. Biostimulants are substances or microorganisms that, when applied to crops through the foliar or root pathways, serve to enhance various processes related to growth and development. These processes include nutrient absorption, tolerance to environmental stress, and overall harvest quality. Interestingly, biostimulants can achieve these effects even when they possess a low concentration of nutrient elements in their composition. Among the main and most often used biostimulants are plant hormones, algae extract, mycorrhizal fungi, protein hydrolysates, and humic substances (humic and fulvic acids). This review sheds light on the biostimulant effects of applying humic substances to plants experiencing hydric stress conditions and low rainfed cultivation. Additionally, it aims to identify gaps in the current research and highlights areas that require further investigation. Furthermore, the review provides a concise overview of the origin and progression of research on humic substances (HS), including their extraction and obtaining process, as well as their structural characteristics and the relationship between structure, properties, and functions. The review also presents the research findings that support the potential of humic substances influencing crops affected by abiotic stress. These findings highlight the beneficial effects of humic substances in enhancing the resilience and performance of crops facing challenges such as drought, salinity, temperature extremes, and other non-biological stressors. The evidence underscores the significance of humic substances as a valuable tool in mitigating the detrimental impacts of abiotic stress on crop productivity and overall plant health.