Impact of thermal blanching and thermosonication treatments on watercress (Nasturtium officinale) quality: thermosonication process optimisation and microstructure evaluation

Rui M.S. Cruz, Margarida C. Vieira, Susana C. Fonseca, Cristina L.M. Silva

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)
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Abstract

The objectives of the present work were to optimise watercress heat and thermosonication blanching conditions, in order to obtain a product with better quality for further freezing, and to evaluate the effects of thermosonication on the microstructure of watercress leaves. In a chart of optimal time-temperature conditions for a 90% peroxidase inactivation (imposed constraint), vitamin C (objective function) and a-value (improvement toward green) were mathematically predicted for both heat and thermosonication blanching treatments. Two optimal thermosonication combinations were selected: 92 °C and 2 s, retaining 95% of vitamin C content and 5% a-value improvement, and a better condition in terms of practical feasibility, 86 °C and 30 s, allowing a 75% vitamin C retention and 8% a-value improvement. The experimental values, for each thermosonication optimal time-temperature zone, were in good agreement with the models' predicted responses. In terms of microstructure, thermosonicated watercress at 86 and 92 °C showed similar loss of turgor and release of chloroplasts. The proposed optimal thermosonication blanching conditions allow the improvement of the blanched watercress quality and consequently contribute for the development of a high-quality new frozen product. However, a suitable scale-up is mandatory for industrial implementation.
Original languageEnglish
Pages (from-to)1197-1204
Number of pages8
JournalFood and Bioprocess Technology
Volume4
Issue number7
DOIs
Publication statusPublished - 1 Oct 2011

Keywords

  • Colour
  • Microstructure
  • Optimisation
  • Peroxidase
  • Thermosonication
  • Vitamin C
  • Watercress

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