European Food Research and Technology

, Volume 220, Issue 3, pp 421–430

Blanching effects on chemistry, quality and structure of green beans (cv. Moncayo)

  • Wenceslao Canet
  • María Dolores Alvarez
  • Pilar Luna
  • Cristina Fernández
  • María Estrella Tortosa
Original Paper

DOI: 10.1007/s00217-004-1051-x

Cite this article as:
Canet, W., Alvarez, M.D., Luna, P. et al. Eur Food Res Technol (2005) 220: 421. doi:10.1007/s00217-004-1051-x

Abstract

Green beans (cv. Moncayo) were blanched at 65, 70, 75, 80, 85, 90 and 97 °C for 2.5, 5, 10, 20 and 40 min. Pectinesterase (PE) activity was highest in cell-wall-bound extracts of beans blanched at 70 °C/10 min. The lowest water-soluble pectin fraction, the highest EDTA-soluble pectin fraction and the lowest degree of esterification of the EDTA-soluble fraction were all recorded for the same temperature/time combination; these effects can therefore be attributed to PE activity. Chemical changes did not affect initial firmness of the beans, which was practically constant after blanching at 65, 70, 75 and 80 °C. Simple first-order models were adequate to establish softening kinetics for beans blanched at 85, 90 and 97 °C. In this temperature range, Kramer maximum force was the mechanical parameter that best characterised bean softening by blanching. For all temperatures, short-time blanching increased the coloration and total chlorophyll content of the samples with respect to fresh control, thus precluding the use of simple models. In the treated beans, the ascorbic acid content was consistently lower than in the control and decreased continuously with increasing time. Microphotographs showed no appreciable differences in morphology between fresh and blanched beans at 65, 70 and 75 °C, which would explain the similarity of mechanical behaviour in these samples. Blanching at 85, 90 and 97 °C caused loosening and swelling of the cell walls owing to breakdown of the pectic material, which again helps to explain the observed loss of firmness.

Keywords

Phaseolus vulgaris Pectinesterase Pectic material Firmness Softening kinetics Structure 

Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • Wenceslao Canet
    • 1
  • María Dolores Alvarez
    • 1
  • Pilar Luna
    • 1
  • Cristina Fernández
    • 1
  • María Estrella Tortosa
    • 2
  1. 1.Department of Plant Foods Science and TechnologyInstituto del Frío-CSICMadridSpain
  2. 2.Department of Plant Biology, Escuela Técnica Superior de Ingenieros AgrónomosU.P.M. Ciudad UniversitariaMadridSpain

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