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.
Highlights
INTRODUCTIONFruit and vegetables are both major food products and key ingredients in many processed foods (Jongen, 2007)
Fruit and vegetables are both major food products and key ingredients in many processed foods (Jongen, 2007).They contain many essential vitamins, minerals, fibre and phytochemicals such as phenolic compounds andAfr
Fresh mature ripe fruit and vegetable samples were washed, peeled and sliced to 5 mm thick and each sample divided into three portions that were subjected in equal loading density of 2.91 kg of fresh produce/m2 of solar aperture to either cabinet direct dryer (CDD) with temperature ranging from 30-55°C for about 3 days, cabinet mixed dryer (CMD) with temperature ranging from 25-49° C for about three days and tunnel dryer (TD) with temperature ranging from 60-73°C, for about two days
Summary
Fruit and vegetables are both major food products and key ingredients in many processed foods (Jongen, 2007). Drying of fruits and vegetables remains an important method of food preservation It reduces the moisture content of food to a level, which allows safe storage over an extended period, and prevents the growth of mould and fungi and minimizing microbial degradation (Chong and Law, 2010; Doymaz, 2011). The quality of sun dried products may adversely be affected, failing to meet the required local and international standards (Ivanova and Andonov, 2001) To overcome these problems, it is necessary to use alternative drying methods. Information on the effect of solar drying methods on total phenolic and antioxidant activities of dried mango, banana, pineapple, and tomatoes is limited.
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