African Journal of
Food Science

  • Abbreviation: Afr. J. Food Sci.
  • Language: English
  • ISSN: 1996-0794
  • DOI: 10.5897/AJFS
  • Start Year: 2007
  • Published Articles: 816

Full Length Research Paper

Effect of solar drying methods on total phenolic contents and antioxidant activity of commonly consumed fruits and vegetable (mango, banana, pineapple and tomato) in Tanzania

Richard J. Mongi
  • Richard J. Mongi
  • Department of Food Science and Technology, Sokoine University of Agriculture, P. O. Box 3006, Morogoro, Tanzania. Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, N-1432 Aas, Norway.
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Bernadette K. Ndabikunze
  • Bernadette K. Ndabikunze
  • Department of Food Science and Technology, Sokoine University of Agriculture, P. O. Box 3006, Morogoro, Tanzania.
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Trude Wicklund
  • Trude Wicklund
  • Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, N-1432 Aas, Norway.
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Lucy M. Chove
  • Lucy M. Chove
  • Department of Food Science and Technology, Sokoine University of Agriculture, P. O. Box 3006, Morogoro, Tanzania.
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Bernard E. Chove
  • Bernard E. Chove
  • Department of Food Science and Technology, Sokoine University of Agriculture, P. O. Box 3006, Morogoro, Tanzania.
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  •  Received: 10 November 2014
  •  Accepted: 12 May 2015
  •  Published: 27 May 2015

Abstract

The effects of solar drying methods [Cabinet direct (CDD), cabinet mixed mode (CMD) and tunnel (TD) drying] on total phenolic content (TPC) and antioxidant capacities of commonly consumed fruits and vegetable in Tanzania were investigated. The TPC and FRAP in mangoes (Mangifera indica cv. Dodo, Viringe and Kent), bananas (Musa acuminata, cv. Kisukari, Kimalindi and Mtwike), pineapples (Ananas comosuss cv Smooth cayenne) and tomatoes (Lycopersicum esculentum cv. Tanya, Cal J and Onyx) were evaluated using Folin-Ciocalteu reagent and ferric reducing antioxidant power (FRAP) methods, respectively. There were significant (p<0.05) variations in TPC (mg GAE/100 g DM) and FRAP (µmol/100 g DM) among the fresh fruit and vegetable samples. The highest TPC was in tomato (476.6±8.6 - 538.9± 1.4) and lowest in banana (139.3±2.3 - 189.2±2.7). Drying methods had significant (p<0.05) effect on TPC and antioxidant values of the samples. All fresh samples had higher TPC levels but declined significantly in dried samples with the exception of tunnel dried tomatoes. Among the dried samples, the tunnel dried samples had less TPC loss (6-16%) than the cabinet dried samples (17-42%). The cabinet direct and mixed mode samples were not statistically different (p>0.05) from each other. However, tunnel dried samples had less FRAP loss (6-13%) which were statistically different (p<0.05) from the cabinet dried samples (14-56%). Percentage TPC and FRAP recoveries (%) differed significantly (P<0.05) between the varieties within the fruits/vegetable for both drying methods. A strong correlations between TPC and FRAP in both fresh (R2= 0.970) and dried samples (R2=0.8636) suggests that solar drying methods have significant effects on total phenolic contents and antioxidant activities of fruits and vegetables with tunnel drying method giving significantly less effects.
 
Key words: Mango, banana, pineapple, tomato, solar drying, total phenolic content (TPC), antioxidant activity, FRAP.