Abstract
Tomato pulp was concentrated by boiling at 90°C for 1 h. A mixture of 0.1% citric acid and 25 ml of vegetable oil were added to 100 g of the paste and packaged in aluminum foil (AF), low density polyethylene (LDP), plastic containers (PC) and stored under ambient temperature (30±0.1°C). Chemical analyses were carried out to determine pH, total solids, total acidity and refractive index as well as viscosity. Microbial analyses were also carried out after 8 weeks of storage. Results obtained showed significant (p<0.05) decreased in the pH value and increase in the titrable acidity (TTA) with storage time in all the packaging materials and samples treated with oil and citric acid (WOC) and those with no oil and citric acid (NOC). However, the decrease in pH and increase in TTA was more rapid in NOC than WOC. The total solid, vitamin A and C decreased significantly (p<0.05) with storage time following the trend as pH. Yeast and total viable count increased significantly (p<0.05) as the storage time increased. Tomato paste stored using AF had lower total plate count, ranging from 1.25 × 105 to 4.51 × 105 as compared to LDP (1.21 × 105-4.41 × 105) and PC (1.21 × 105-6.02 × 105). Generally, tomato paste in AF retained higher quality after 8 weeks of storage as compared to samples stored in LDP and PC. Also, NOC samples were more prone to spoilage than WOC. These findings can be applied for better preservation of tomato paste in rural communities where there is no electricity for cold storage.
Key words: Packaging materials, tomato paste, citric acid, vegetable oil, storage period.
