Chemical and Microbiological Evaluation of Dried Tomato slices for Nigerian System

Effect of two simple drying methods (sun drying and oven drying at 40 °C, 50 °C and 60 °C) on the quality of tomato slices were evaluated. Fresh tomato sample served as the control. Firm and fresh ripe tomatoes were washed and sliced to a uniform thickness of 7mm. 200g each of the sample was dried for12 hours and the moisture loss was monitored at 2-hour interval. The fresh and dried tomato slices were evaluated for changes in moisture content, lycopene, beta-carotene, ascorbic acid, as well as total bacterial and fungi counts.

The moisture content was significantly (at p<0.05) reduced after drying from 88.09% (for fresh samples) to 16.87%. The contents of ascorbic acid in the control sample significantly (at p<0.05) reduced from 17.78mg/100mg (for fresh) to 10.23mg/100mg in the sun-dried samples (lowest value). There was considerable increase in the beta-carotene content from 1.16±0.22% in the control sample to 1.91±0.11%, 1.96±0.22%, 1.78±0.11% and 1.45±0.19% in samples dried at 40 °C, 50 °C, 60 °C and sun-dried samples respectively. Lycopene content also increased with drying. Beta-carotene and lycopene were best retained in samples dried at 50 °C. Tomato slices dried in the oven had lower microbial load compared with sun-dried samples. Microbial load reduced with increase in oven temperature with sun-dried samples having the highest microbial load.

Keywords: Drying; Tomatoes; Shelf life; Chemical components; Microbial load