Effectiveness of Acidic Solutions as an Antimicrobial Agent on Plain Bread


  • Myoori Amirthalingam
  • Alex Chitan
  • Presley Nip
  • Liam O’Keeffe


Bread spoilage leading to food wastage is detrimental to the environment, economy, and consumers alike. Much of this wastage can be attributed to the spoilage of foodstuffs as it moves from farm to table. The aim of our study is to explore natural preservatives as a means of reducing bread spoilage. To do this, we produced five treatments of various pH solutions and observed their effects on ten samples of 5cm x 5cm bread slices placed indoors in plastic bags for an 18-day period. During this timespan, we recorded biweekly measurements of mold coverage. All treatments inhibited growth by day 4. By day 8, only group 2 (pH = 2.73), group 3, and group 4 (pH 5.51) continued to provide inhibitory effects on mold growth (p<0.05). Groups 2 and 3 continued to inhibit growth by day 11, while group 3 was the only group that provided significant growth inhibition after day 15. Lastly, groups 2, 3, and 5 (pH = 5.21) all provided a decrease in mold growth rate which scaled with the treatment’s acidity (p<0.05). These results are consistent with past literature and suggest that increased acidity facilitates the inhibition of enzymes vital for metabolism, as described in the “weak acid theory”. This cytoplasmic acidification increases proportionally to the treatment’s acidity, providing both more substantial and longer-lasting inhibition of microbe and fungi growth. These results have important implications for new technology in food sciences, such as lactic acid bacteria, which show promise in the natural preservation of bread products