Effects of acidic treatment on the physicochemical, microstructural, and microbiological properties of fresh-cut lotus root during storage.

Abstract

Freshly cut slices of lotus root are a popular food item in various countries; however, problems such as enzymatic browning affect the storage stability of these products. In the present work, we evaluated for the first time the effect of low pH treatments on the overall quality of fresh-cut lotus root (physicochemical, microbiological, and morphological properties) during storage. The effect of acidic treatment, using citric acid solution at pH 2 or pH 4 at 2% w/w and 0.002% w/w, respectively, will help to improve our understanding of the mechanism of browning and the role of polyphenol oxidase in catalysing browning reactions. Treatments were prepared using citric acid and were applied to 5 mm thick fresh-cut lotus for 2 min. Samples were then stored for 16 days at 5°C. We found that the whiteness values (L*) of pH 2 (68.76) and pH 4 (65.77) treated samples were significantly higher than the control (57.37), suggesting an enhancement of colour quality during storage. We also observed reduced polyphenol oxidase (PPO) enzyme activity for the treated samples as compared to the control (12.5, 16.5, and 17.13 U/min-mL, respectively), as well as reduced total phenolic content (46.5, 44.3, and 57.8 mg/100 g sample) and microbial counts. Despite these promising results, we also observed undesirable effects as a result of the pH treatments 2 and 4, including tissue softening and microstructural changes. However, we believe that our findings will be significant in the development of an optimised formulation for dipping treatments of fresh-cut lotus root products.

Keywords: catechol oxidase, citric acid ,effects ,enzyme activity , enzymes ,foods ,microbiology , morphology , oxidoreductases,phenolic compounds ,polyphenols