Effect of chemical preservation on the shelf-life of bottled intermediate moisture tomato paste stored at ambient temperature

Abstract

Six samples of bottled intermediate moisture tomato paste were stored at ambient conditions (33-38°C). Four of the samples were preserved with chemicals. One of the last two samples which was bottled with no chemical preservatives added had palm oil filled onto its headspace. Shelf-like studies conducted for forty weeks showed no appreciable changes in chemical properties of samples mixed with sodium metabisulphite and sodium benzoate. The samples with vinegar and palm oil filled headspace showed changes in chemical properties from the 13th week of storage. Chemical changes were noticed on the 10th and 4th week respectively for sodium chloride treated and untreated control paste samples. There was no significant difference in organileptic properties of all the samples in the first 8 weeks of studies with the exception of untreated control sample, which was rated lower (p<0.05) in overall acceptability. However, from the 16th week of storage, the untreated control sample became inferior in all the organoleptic attributes measured when compared to the samples mixed with sodium metabisulphite and sodium benzoate as well as palm oil filled headspace sample. Fungi and yeasts were absent in the samples. The identified bacteria isolates were Bacillus (identified in all the samples). Lactobacillus and Staphylococcus were identified in some samples.

Keywords: preservation, shelf-life, intermediate moisture, tomato paste, ambient temperature

Nigerian Food Journal Vol. 23 2005: 183-192