Moisture sorption isotherms characteristics for shelf-life prediction of peanuts (Arachis Hypogaea L.)

The spring grown peanut varieties J87 and TG37A are prone to quality deterioration as a result of high temperature and relative humidity during harvesting. Thus, the sorption isotherms of peanut varieties were evaluated at 25, 35 and 45 °C and the water activity (a_w ) range of 0.110-0.975 aiming to predict the suitable storage conditions, packaging material and shelf-life.

The equilibrium moisture content (EMC) increased with increased a_w and isotherms of type II were observed. The monolayer moisture content varied between 3.135% and 4.235% for J87 and between 3.906% and 5.640% for TG37A variety. The experimental data were fitted to seven mathematical models. The variations in correlation coefficients were in the range 0.879-0.992 and in root mean square were in the range 0.055-1.988. On the basis of statistical parameters, Guggenheim Anderson de Boer and Double Log Polynomial were considered to be best fitted models. At a_w of 0.6, critical moisture content (CMC) was 7.59%, 7.060% and 5.89% for J87 and 9.06%, 8.904% and 7.80% for TG37A at 25, 35 and 45 °C, respectively. The shelf-life prediction model provided that the aluminum packages had the maximum predicted shelf-life of around 1779 days for TG37A and 1077 days for J87 variety at 25 °C with an initial moisture content of 5.91% and 4.81%, respectively.

The EMC and CMC evaluated from sorption study provided the basis for determination of package properties and shelf life. Aluminum packages had the minimum water vapor transmission rate and permeability. Hence, peanuts packaged in these bags and stored at 25 °C and 75% relative humidity had the potential to attain the maximum storage life. © 2023 Society of Chemical Industry.