Drying Characteristics Of Pretreated Pulp of Triploid and Tetraploid Plantain Varieties
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Date
2011-07-14
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Abstract
The influence of blanching, citric acid and sodium metabisulphite pretreatment, and temperature on the air drying characteristics and selected functional properties such as water binding capacity, solubility, swelling power, bulk density, pH and rehydration ratio of French Horn, False Horn and FHIA-21 were investigated. Air temperature had the greatest influence on the drying rate as increase in temperature from 50oC to 80oC resulted in an increase in drying rate. The effect of sodium meta bisulphite and citric acid pretreatments increased as the drying temperature decreased and this was evident as citric acid and sodium meta bisulphite in the three plantain varieties at 50oC saved 33% and 25% of drying time respectively for French Horn, 16% and 6.5% for False horn, and 37.5% and 31% for FHIA-21. Meanwhile blanching pretreatment slowed the drying process among all three varieties. Drying occurred in the falling rate period. Two thin layer drying models namely Logarithmic and Page model were evaluated by fitting to experimental moisture ratio data. The Page model satisfactorily described the drying behaviour for the three plantain varieties. Effective moisture diffusivity increased with increasing in drying air temperature. Temperature dependency of moisture on diffusivity was illustrated by the Arrhenius relationship. Over the range of temperature, effective moisture diffusivity varied from 7.54 x 10-10 to 2.37 x 10-9, 5.17 x 10-10 to 3.11 x 10-9 , 3.98 x 10-9 to 5.40 x 10-10 for French Horn, False Horn and FHIA-21 respectively. Activation energy for drying ranged from 11.88 to 33.10, 26.76 to 44.50, 27.24 to 56.61kJ/mol for French Horn, False Horn and FHIA-21 respectively. The effect of variety and pretreatment were significant (p<0.05) on activation energy. Comparison of the proximate analysis of the three varieties indicated marked variations in the nutritional status of the three plantain varieties. The results of the study further indicated that temperature and pretreatment significantly (p<0.05) affected solubility, swelling power, water binding capacity and pH.
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A Thesis Submitted To The Department Of Biochemistry And Biotechnology, Kwame Nkrumah University Of Science And Technology In Partial Fulfillment Of The Requiremnt For The Degree Of Master Of Food Science And Technology