The impact of high hydrostatic pressure treatment on anthocyanins, colour, microorganisms, and enzyme activity of mulberry (Morus nigra) juice
2020
Ma, Y. K. | Engmann, F. N. | Sanful, R.
The effects of high hydrostatic pressure (HHP) treatments at 200, 400, and 600 MPa, for 10, 20, and 30 min on residual activities of polyphenol oxidase (PPO) and peroxidase (POD), colour properties, and microbial populations of total viable count, yeasts, and moulds of mulberry juice were determined with reference to untreated mulberry juice. Lower pressure levels were found to significantly inactivate PPO activity than higher pressure level. A strong positive relationship (R = 0.947) existed between PPO activity and increases in pressure and time. Also, a moderately positive relationship existed (R = 0.358) between POD activity and increases in pressure and time, but the relationship was not statistically significant. Anthocyanin content was better retained at lower pressure levels than at higher levels, with sample treated at 200 MPa/10 min retaining 96.50 ± 0.74%. An inverse relationship was observed between anthocyanin retained and residual PPO (R = -0.425) and POD (-0.075) activities, but the relationships were not statistically significant. Total viable count as well as yeast and mould count of all HHP treated mulberry juice samples were < 10 CFU/mL with log10 4.86, 4.45, and 4.83 CFU/mL reductions, respectively. Also, colour parameters of brightness, hue angle, chroma, and total colour difference were differently affected. Treatment at 200 MPa/10 min gave a better inactivation of PPO and POD, better retention of anthocyanin, and preserved the colour of the mulberry juice to almost the same extent as the control, making it the best treatment to be adopted.
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