Moisture adsorption isotherm of cassava-based custard powder

Abstract

Like most powdery foods, cassava-based custard powder (CbCP) and its recipes (yellow-fleshed cassava root starch-YfCRS and whole egg powder-WEP) are hygroscopic, and the storage environmental conditions such as temperature and relative humidity could adversely affect its quality. Thus, this study investigates the moisture adsorption isotherm (MAI) of the CbCP. The CbCP was produced by blending YfCRS (90-98%) with WEP (2- 10%) as the major recipes. The CbCP was subjected to MAI using the static gravimetric method at temperatures of 27, 37 and 42 º C and water activity levels between 0.10 and 0.80. Data obtained were fitted to four sorption models-Peleg, Guggenheim, Anderson, and de Boer (GAB), Oswin and Langmuir. The model fit was evaluated using the coefficient of determination (R2 ), root means square error (RMSE), and means percentage deviation (%E). The result showed that the Peleg model best fit the CbCP MAI data (0.98 ≤ R2 ≤ 1.00). The monolayer moisture content (Mo ) was significantly higher (p < 0.05) in the YfCRS compared to that of the WEP, which was lower. The highest Mo (8.09 g H2 O/100 g) was obtained in CbCP containing 94% YfCRS and 11.66% WEP, and the lowest monolayer moisture content (6.35 g H2 O/100 g) was obtained in CbCP containing 98% YfCRS and 10% WEP. However, all the CbCP might be stored for extended periods at all temperatures since their monolayer moisture content falls within the acceptable limit for storage stability.