Secagem e caracterização da grama de trigo (Triticum aestivum L.) por cast-tape drying e liofilização

Abstract

Wheatgrass (Triticum aestivum L.) is a food derived from the common wheat grain's germination, popularly consumed as juice and known for its nutritional properties, such as high vitamins, minerals, amino acids, enzymes, and chlorophyll. Because it has a limited harvest period and is very perishable, there is a need to develop processes that can increase its useful life for the consumer, with drying being one of the processes that can be used. However, dehydration of foods can cause nutritional damage, and it is essential to define the drying methods, processes, and parameters. Given the above, this work's objective was to study the drying of wheatgrass by cast-tape drying (CTD) and freeze-drying and characterize the dry material by these processes in terms of physical-chemical and biocomposite characteristics. Different methods were used to reduce the size and obtain the pulp of the wheatgrass for drying. The one considered most suitable for the drying processes was cutting with a knife every 1 cm, deep freezing the chopped grass, and processing in a blender. The operational conditions (temperature, material thickness, time, etc.) in drying by CTD were also evaluated. Wheatgrass has proven to be a material that adapts well to drying by CTD and also by freeze-drying. The condition of drying by CTD that showed the best preservation results of the wheatgrass's characteristics and components was using circulating water temperature of 80 ° C and 2 mm of material thickness. In this condition, the final moisture of the product was close to 7%, with drying time around 60 minutes, the hygroscopicity of 16.73 ± 0.56%, the overall color variation concerning the wheatgrass pulp was 5.242, phenolic compounds content of 1551.209 ± 27.638 (mg EAG / 100g of sample (dry basis - bs). Freeze-drying for 48 h resulted in moisture below 5%, hygroscopicity statistically equivalent to the dry product by CTD at 80 °C, 12% reduction in the concentration of phenolic compounds concerning the fresh samples. However, color was the parameter most affected by freeze-drying, presenting an overall color difference of 8.763 concerning fresh pulp. Thus, it is noteworthy that it was possible to determine the most suitable methodology for drying wheatgrass by CTD and freeze-drying through this study. It was also possible to identify the condition of drying by CTD that produced powders with good physical and chemical properties and considerable concentrations of phenolic compounds.