Sorption Isotherms and Isosteric Heat of Peanut Pods,Kernels and Hulls

Abstract

This study was carried out to evaluate the sorption isotherms of peanut pods, kernels and hulls for several temperature and humidity conditions and to fit different mathematical models to the experimental data, selecting the one best fitting the phenomenon. The dynamic method was applied to obtain the hygroscopic equilibrium moisture content. The environmental conditions were provided by means of an atmospheric conditioning unit, in which removable perforated trays were placed to allow air to pass through peanut mass, each one containing 50 g of the product. The mathematical models frequently used for the representation of hygroscopicity of agricultural products were fit to the experimental data. Based on those results, it was concluded that peanut pods, kernels and hulls presented differentiated hygroscopicity. The equilibrium moisture content for peanut pods, kernels and hulls increased with an increase in the relative humidity at any particular temperature and decreased with increase in temperature at constant relative humidity. At a constant water activity, peanut hulls samples had higher equilibrium moisture content than the pods and kernels samples. Based on statistical parameters, the modified Henderson and Chung-Pfost models were found to adequately describe the sorption characteristics of peanut pods, kernels and hulls. Isosteric heat of desorption were evaluated by applying the Clausius—Clapeyron equation to experimental isotherms and decreased with increasing moisture content. The peanut hulls had higher isosteric heat of sorption than that peanut pods and kernels.

Keywords

equilibrium moisture content Arachis hypogaea mathematical models desorption isosteric heat

Get full access to this article

View all access options for this article.

References

Aguerre R. , Suarez C. and Viollaz P. (1988). The temperature dependence of isosteric heat of sorption of some cereal grains . International Journal of Food Science and Technology 23: 141—145 .

Anderson R.B. (1946). Modifications of the Brunauer, Emmett and Teller equation. Journal of the American Chemical Society 68: 686—691.

Ayranci E. and Duman O. (2005). Moisture sorption isotherms of cowpea (Vigna unguiculata L. Walp) and its protein isolate at 10, 20 and 30°C. Journal of Food Engineering 70: 83—91 .

Brooker D.B. , Bakker-Arkema F.W. and Hall C.W. (1992). Drying and Storage of Grains and Oilseeds. Westport: The AVI Publishing Company .

Chen C. ( 2000a). A rapid method to determine the sorption isotherms of peanuts . Journal Agricultural Engineering Research 75: 401—408 .

Chen C. ( 2000b). Factors which effect equilibrium relative humidity of agricultural products . Transactions of the ASAE 43: 673—683 .

Chen C. ( 2002). Sorption isotherms of sweet potato slices . Biosystems Engineering 83: 85—95 .

Chen C. ( 2003). Moisture sorption isotherms of pea seeds. Journal of Food Engineering 58: 45—51 .

Chen C. and Jayas D.S. (1998). Evaluation of the GAB equation for the isotherms of agricultural products . Transactions of the ASAE 41: 1755—1760 .

10.

Chen C. , and Morey, R.V. (1989). Comparison of four EMC/ERH equations . Transactions of the ASAE 32: 983—990 .

11.

Corrêa P.C. Martins D.S.R. and Melo E.C. (1995). Umigrãos: Programa para o cálculo do teor de umidade de equilíbrio para os principais produtos agrícolas [Umigrãos: Program for the calculation of equilibrium moisture content of the main agricultural products] . Viçosa, MG — Brazil: Centreinar — UFV .

12.

Fan J. , Siebenmorgen T.J. and Marks B.P. (2000). Effects of variety and harvest humidity content on equilibrium humidity contents of rice. Applied Engineering in Agriculture 16: 245—251 .

13.

Iglesias H.A. and Chirife J. (1976a). Isosteric heats of water vapour sorption on dehydrated foods. Part II: hysteresis and heat of sorption comparison with BET theory . Lebensmittel Wissenschaft and Technologie 9: 123—127 .

14.

Iglesias H.A. and Chirife J. (1976b). Prediction of effect of temperature on water sorption isotherms of food materials . Journal of Food Technology 11(a): 107—113 .

15.

Jayas D.S. and Mazza G. (1991). Equilibrium humidity characteristics of safflower seeds. Transaction of the ASAE . 34: 2099—2103.

16.

Kaya S. and Kahyaoglu T. (2006). Influence of dehulling and roasting process on the thermodynamics of moisture adsorption in sesame seed. Journal of Food Engineering 76: 139—147 .

17.

Martinez N.N. and Chiralt A. (1996). Influence of roasting on the water sorption isotherms of nuts . Food Science and Technology International 2: 399—404 .

18.

McMinn W.A.M. and Magee T.R.A. (2003). Thermodynamic properties of moisture sorption of potato . Journal of Food Engineering 60: 155—157 .

19.

Ministério da Agricultura e Reforma Agrária ( 1992). Regra para análise de sementes [Seeds Analysis Standard] . Brasília: Ministério da Agricultura e Reforma Agrária de Brazil, Secretaria Nacional de Defesa Agropecuária .

20.

Mohapatra D. and Rao P.S. (2005). A thin layer drying model of parboiled wheat. Journal of Food Engineering 66: 513—551 .

21.

Mohsenin N. (1986). Physical Properties of Plant and Animal Materials . New York: Gordon and Breach Science Publisher .

22.

Mulet A. , Garcya-Pascual P. , Sanjuán N. and García-Reverter J. (2002). Equilibrium isotherms and isosteric heats of morel (Morchella esculenta). Journal of Food Engineering 53: 75—81 .

23.

Özdemir M. and Devres Y.O. (1999). The thin layer drying characteristics of hazelnuts during roasting. Journal of Food Engineering 42: 225—233 .

24.

Pagano A.M. and Mascheroni R.H. (2005) Sorption isotherms for amaranth grains. Journal of Food Engineering 67: 441—450 .

25.

Palipane K.B. and Driscoll R.H. (1992). Moisture sorption characteristics of inshell macadamia nuts. Journal of Food Engineering 18: 63—76 .

26.

Pfost H.B. , Mourer S.G. , Chung D.S. and Milliken G.A. (1976). Summarizing and Reporting Equilibrium Moisture Data for Grains. ASAE Paper No 76-3520. St Joseph , MI: ASAE .

27.

Sanchez E.S. , Sanjuan R. , Simal S. and Rossello C. (1997). Calorimetric techniques applied to the determination of isosteric heat of desorption for potato. Journal of Science Food and Agriculture 74: 57—63 .

28.

Sanni L.O. , Atere C. and Kuye A. (1997). Moisture sorption isotherms of Fufu and Tapioca at different temperatures. Journal of Food Engineering 34: 203—212 .

29.

Thompson H.L. (1972). Temporary storage of high moisture shelled corn using continuous aeration . Transactions of the ASAE 15: 333—337 .

30.

Van den Berg C. (1984). Description of water activity of foods for engineering purposes by means of the GAB model of sorption. In: McKenna B.M. (ed.), Engineering and Foods. New York: Elsevier , pp. 311—321.

31.

Van den Berg C. and Bruin S. (1981). Water activity and its estimation in food systems . In: Rockland L.B. and Stewart G.F. (eds), Water Activity: Influences on Food Quality. New York: Academic Press , pp. 147—177.

32.

Wang N. and Brennan J.G. (1991). Moisture sorption isotherm characteristics of potatoes at four temperatures. Journal of Food Engineering 14: 269—287 .