Water Sorption Behaviors of Cottonseed Meal, Washed Cottonseed Meal, and Cottonseed Protein Isolate

Due to their hygroscopic characteristics, equilibrium moisture contents of agricultural products and byproducts are very important for their quality. Defatted cottonseed meal (CSM), washed cottonseed meal (WCSM), and cottonseed protein isolate (CSPI) can be used as an energy and protein source of animal feedstuff or industrial raw materials. Information on their moisture adsorption behaviors is needed for their storage conditions and quality control. Thus, this work measured the equilibrium moisture sorption isotherms of CSM, WCSM and CSPI, at 15, 25, 35 and 45 0C. When the moisture contents of the samples were compared at a constant temperature, the general trend of decreasing moisture content was in the order of CSPI < WCSM < CSM at the water activity < 0.6, but the trend reversed to the order of CSM < WCSM < CSPI at the water activity > 0.6. Relevant 13 sorption isotherm equations were tested for goodness-of-fit of these moisture adsorption data. Modelling results indicated that the G.A.B. model was a consistently good fit for the data among all sample types and all temperatures. This work provides some insight on designing or selecting appropriate procedures for the handling, aeration, storing and processing of these cottonseed meal products