The microbial quality of locally produced soursop juice and the effect of pasteurization, acidification and chemical preservative on the juice were investigated. Soursop juice samples were analyzed according to standard bacteriological and chemical methods. Microbiological quality of the treated juice (pasteurized at 60°C for 1 h, acidified with lime and addition of 0.05% sodium benzoate) was evaluated. Microbial load increased in the sample (without treatments- control), from 4.3 × 106 to 14.6 × 106 cfu ml-1. Pasteurized soursop juice showed a decrease in microbial load from 2.2 × 103 to 4.2 × 101 cfu ml-1. Juice treated with sodium benzoate also decreased in microbial load from 1.2 × 106 to 2.3 × 105 cfu ml-1 while acidified soursop juice decreased from 2.3 × 106 to 4.8 × 103 cfu ml-1. Pasteurized soursop juice increased in pH from 4.89 to 4.98 and a decrease in titrable acidity from 23.25 to 21.92. Soursop juice treated with sodium benzoate increased in pH from 5.94 to 6.23 and a decrease in titrable acidity from 23.62 to 18.10. Acidified soursop juice decreased in pH from 4.03 to 3.95 and an increased but with steady titrable acidity of 37.50. The study reveals that the synergistic effect of pasteurization, acidification and treatment with sodium benzoate can be used to extend the shelf-life of soursop juice for up to two weeks.
Key words: Soursop juice, microbial quality, pasteurization, acidification, benzoate.
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