Drying technology of mesquite pods (Prosopis laevigata) and microstructural insights

Abstract

PurposeMesquite pods offer a high nutritional content; A flour can be produced from them; nevertheless, the moisture content makes the milling process difficult. Then, before the milling operation a drying process must be implemented, but drying technology must be studied in order to characterise the process and identify the effect of drying temperature on the magnitude of drying rate.Design/methodology/approachProsopis Laevigata pods were collected in Oaxaca (Southern of Mexico) and they were dried. Three stages of maturity were identified and pods in the stage three of maturity were dried by forced convection. The internal structure of the pods was analyzed by scanning electron microscopy (SEM). The pods were dried in a tunnel dryer at 40, 50, 60 and 70° C, 10% relative humidity and air velocity of 2.6 m/s. From experimental data, a lumped analysis was conducted for drying.FindingsWe found that the internal microstructure of this material is a limiting factor for moisture migration. In order to reduce the moisture content in the pods, a minimum air temperature of 60° C must be applied. The characteristic drying curve shows a good agreement with the experimental drying kinetics. The nutritional composition (carbohydrates, sugar and protein) of pods reveals important applications for the food industry.Practical implicationsThe mesquite pods are important ethnic foods. In order to obtain flour, the drying of pods is mandatory. Drying must be applied in stage three of maturity which can be identified based on color changes and moisture content. The moisture content affects the performance of milling operation, then a minimum drying temperature of 60° C and low relative humidity must be applied. SEM images show the complex microstructure of the pods which hinders the moisture diffusion. The drying characteristic curve was deduced for the first time; it helps to understand the drying behavior of pods. The chemical composition of mesquite pods reveals interesting applications for the food industry. The methodology for drying is useful for researchers and producers.Originality/valueMezquite pods is an interesting ethnic food for people with celiac disease. This is the first time a research paper describes the drying process at detail. The SEM images, the convective drying operation and the characteristic curve are presented for the first time. The information will be useful for the industry and academia.