Moisture sorption isotherms of Mesquite seed (Prosopis africana)

Abstract

Moisture profoundly influences product attributes such as quality and safety. The knowledge of moisture sorption isotherm is essential to determine products stability, and needed for design of storage, packaging and drying systems for extension of shelf lives. This study is to develop sorption isotherms of Prosopis africana.
The moisture sorption isotherms of the seed were determined at temperatures of 20ºC, 25ºC and 30ºC, over a relative humidity range of 11%-100% using the static gravimetric technique. A linear regression programme was used to fit five isotherm models; GAB, Oswin, Halsey, Henderson, and Chung Pfost to the experimental data and compared using the root mean standard error, regression coefficient, standard error of estimate, and randomness of residuals.
The adsorption and desorption isotherms of the seed followed the type II isotherm which exhibited a sigmoidal curve and also resulted in a hysteresis effect. At 20oC, Chung Pfost gave the best for the Prosopis africana in the adsorptive mode while at 25oC, the GAB, Henderson and Chung Pfost models gave the best fit. At 30oC, the Henderson and Chung Pfost had a good fit. Through all the temperatures for the prosopis Africana in the adsorptive mode, the Chung Pfost model has the best fit all through. In the desorption mode of Prosopis africana at 20oC and 25oC, the r2 for Chung Pfost, Henderson, GAB, Halsey, and Oswin range from 0.854 to 0.956 and 0.896 - 0.966 respectively. All the five models gave a good fit. At 30oC, the Chung Pfost, GAB and Henderson gave the best fit.