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ARS Home » Southeast Area » Dawson, Georgia » National Peanut Research Laboratory » Research » Publications at this Location » Publication #258851
Title: Sorption isotherm modeling of different peanut types

Author
item Sundaram, Jaya
item Kandala, Chari
item Butts, Christopher - Chris

Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 12/5/2009
Publication Date: 6/20/2010
Citation: Sundaram, J., Kandala, C., Butts, C.L. 2010. Sorption isotherm modeling of different peanut types. Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE).

Interpretive Summary: Peanuts are becoming more important food product and in recent years its production is increasing rapidly. In North America most of the peanuts are grown in southeastern states. Peanuts from there are processed and exported to other parts of the country and abroad. Peanuts are stored after they dried to 10.5% moisture content or less than that to increase the shelf life. Sorption of moisture content from the storage environment would increase the moisture content of the dried peanuts. If the moisture content of the peanuts at which it is in equilibrium with the storage environment relative humidity is called equilibrium moisture content (EMC) at that storage condition. Therefore it is important to determine the EMC of the peanuts for its safe storage and as well as for drying. Plotting a curve using EMC values at a given temperature against the relative humidity is called sorption isotherms. Adsorption and desorption isotherms are obtained by measuring EMC by wetting and drying the peanuts respectively. Different relative humidity was obtained in a closed air tight desiccator using saturated salt solutions. By exposing the peanut samples to this conditioned air, they attained equilibrium with the relative humidity of the environment. EMC and relative humidity data were fitted to different sorption isotherm models namely BET, GAB, modified Oswin, modified Henderson and modified Halsey. This study described accurately the sorption data for whole peanuts, hulls and kernels. Since the hulls and kernels were varied in their composition they showed significantly different sorption data.

Technical Abstract: Peanuts are becoming more important food product and in recent years its production is increasing rapidly. In North America most of the peanuts are grown in southeastern states. Peanuts from there are processed and exported to other parts of the country. Peanuts are harvested at high moisture levels and dried to 10.5 % (w.b) or less for its safe storage. Shelf life of the peanuts is increased by reducing the moisture content to the safe level and storing them in a well designed storage systems. To design a storage system accurate prediction of relationships between equilibrium moisture content (EMC), equilibrium relative humidity (ERH) and the storage temperature are very important. Whole peanut is composed of kernels, hulls and some air enclosed inside the hull around the kernels. Quite limited data available on literature for sorption isotherm curves of peanuts. In this study two different market types of peanuts were selected namely Valencia and Georgia green. Both the types were divided in three parts such as whole peanuts, hulls and kernels. All were conditioned to get same moisture contents. After that each part was equilibrated to 10 different relative humidity environments varying from 8 to 94% using different saturated salt solutions in an air tight desiccator. Once they reached a constant weight the equilibrium moisture contents (EMC) were measured using standard air oven method at 130oC. Similarly EMC of all three parts were calculated by varying the temperature from 5 to 45oC with 10oC increments to get sorption and desorption EMC values. EMC, ERH and temperature data were fitted to different sorption isotherm models namely BET, GAB, modified Oswin, modified Henderson and modified Halsey. This study described accurately the sorption data for whole peanuts, hulls and kernels. Since the hulls and kernels were varied in their composition they showed significantly different sorption data.