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Because of the health benefits provided by the consumption of yacon and its perishability, the foam mat drying (FMD) was applied in order to increase its shelf life. Yacon juice foams formed by the addition of two different foaming agents (emulsifier and egg albumin) and incorporation of air were subjected to dehydration, with different air temperatures (50, 60 and 70C) and layer thicknesses (0.5, 1.0 and 1.5 cm). The drying rate and effective diffusivity increase with the rise in temperature and the thickness of foam, being higher for the foam formed with egg albumin rather than emulsifier. The experimental data were fitted to several thinlayer models, among which the logarithmic model was the most suitable to represent the process. The effect of temperature, thickness and foaming agent on the drying kinetics has not been studied previously; hence, this research can aid the design of optimized FMD processes. PRACTICAL APPLICATIONSYacon is a food with great potential for research because of its beneficial properties to human health, especially the prebiotic activity, which is ascribed to the high concentration of inulin and fructooligosaccharides in its composition. However, the high percentage of water renders this tuber extremely perishable, hindering transporting and processing. The foam layer drying reduces drying time and energy demand with respect to other drying techniques and allows the formation of products with excellent physicochemical and sensorial characteristics. The assessment of the process kinetics and application of mathematical models to predict it provides information for the process design, increasing the use of yacon in the agro industry.

The objective of this study was the development and optimization of a probiotic apple beverage as well as the establishment of a sensory profile by using chemical, microbiological, and quantitative descriptive analysis (sensory profiling). For this purpose, both Lactobacillus casei and L. acidophilus were tested in two different media ‐ Fuji and Gala apple juices ‐ at different pH values. The optimal conditions to develop the apple probiotic beverage were obtained by response surface methodology. They were found to be 10 h of fermentation at 37oC in Gala apple juice. Sensorially, the clarified Gala apple juice was characterized by a caramel color, apple aroma, and an acidic apple taste. The fresh fermented probiotic apple beverage was characterized by a thick texture and sweet taste. The probiotic apple beverage stored for 28 days at 7oC presented a thick texture and acidic taste. Finally, when the fermented probiotic beverage was tested by potential consumers, it presented an acceptance index of 96%.