pH Dependence of the Formation of Malondialdehyde (MDA) in the Reaction of 2-Thiobarbituric Acid (2-TBA) with Local Yoghurt (Nunu)

Abstract

The study investigates the pH dependence of malondialdehyde (MDA) formation in local yoghurt (Nunu) through its reaction with 2-thiobarbituric acid (2-TBA), using the Thiobarbituric Acid Reactive Substances (TBARS) assay. A total of 10 experimental setups were conducted across seven pH levels (5.6 to 9.0) and ten graded 2-TBA volumes (10 μL to 100 μL). Samples were allowed to equilibrate for up to 12 h before UV-Visible spectrophotometric measurements were taken at 532 nm. Descriptive statistics and comparative analyses were used to evaluate mean MDA concentrations across conditions. The results showed no clear linear relationship between pH and MDA levels; however, a consistent spike in MDA concentrations was observed at alkaline pH, notably at pH 8.6. The highest MDA concentration (1.0600 ± 0.0011 mg/L) was recorded at this pH, while the lowest was at pH 5.6 (0.241 ± 0.010 L), indicating enhanced lipid peroxidation or increased TBA-MDA complex stability in alkaline environments. This research highlights the complex pH sensitivity of lipid peroxidation in fermented dairy products and underscores the need to consider environmental factors such as pH when assessing oxidative stress markers like MDA. Future studies may benefit from refining the pH gradient intervals, extending incubation times, incorporating centrifugation steps, examining the effect of IHP (inositolhexakisphosphate) on the affinity of local yoghurt for 2-Thiobarbituric acid, and validating MDA levels through more specific techniques like HPLC. The findings hold implications for food quality monitoring, oxidative stress assessment, and health risk evaluations associated with lipid peroxidation products in traditional dairy foods.