The effect of natural and artificial preservatives and storage temperature on the pH and microbial load of freshly produced apple (Malus domestica) juice

Abstract

Apple (Malus domestica) juice was treated with 0.5 g/ml garlic, 0.5 g/ml ginger, 0.25 g/ml mix of ginger and garlic and 0.05% (w/v) of sodium  benzoate respectively where the ginger, garlic and sodium benzoate serves
as natural and artificial preservatives. Their effects on the apple fruit juice  were evaluated during 8 days of storage at 4^oC and at room temperature (28±2^oC). The microbial counts ranged from 4.0×10⁴ to 7.0×10³ cfu/ml and from 1.0×10⁴ to 2.0×10³ cfu/ml for bacteria and fungi, respectively in the samples treated with ginger, garlic and sodium benzoate and from 1.2×10⁴ to 2.2×10⁴ cfu/ml in the apple juice without treatment. Juice treated with sodium benzoate had the least microbial contamination while the untreated juice had the highest. There was marginal decrease in pH values across treatments in stored apple juice with juice stored at 4^oC showing the least change in pH compared to that stored at room  temperature. The results obtained show that the preservatives exhibited antimicrobial effect on the microbial load and that pH has a significant impact on the shelf-life of the fruit juice as the microbial load was least  when stored at low temperature the pH as acidity tends to be inclined towards low pH.

Key words: apple juice, pH, microbial load, sodium benzoate, temperature