Impact of Thermal Blanching and Thermosonication Treatments on Watercress (Nasturtium officinale) Quality: Thermosonication Process Optimisation and Microstructure Evaluation |
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Authors: | Rui M S Cruz Margarida C Vieira Susana C Fonseca Cristina L M Silva |
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Affiliation: | (1) CBQF/Escola Superior de Biotecnologia, Universidade Cat?lica Portuguesa, Rua Dr. Ant?nio Bernardino de Almeida, Porto, 4200-072, Portugal;(2) Instituto Superior de Engenharia, Universidade do Algarve, Campus da Penha, Faro, 8005-139, Portugal |
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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. |
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