Characterization of Apple Juice Foams for Foam-mat Drying Prepared with Egg White Protein and Methylcellulose

Authors

  • Narindra Raharitsifa,

    1. Authors Raharitsifa and Ratti are with Dept. des Sols et de Génie Agroalimentaire, Faculté des Sciences de l'Agriculture et de l'Alimentation, Univ. Laval, Quebec, Canada. Author Genovese is with Planta Piloto deIngeniería Química, Camino “La Carrindanga” Km 7, CC 717, (8000) Bahía Blanca, Argentina. Direct inquiries to author Genovese (E-mail: dgenovese@plapiqui.edu.ar).
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  • Diego B. Genovese,

    1. Authors Raharitsifa and Ratti are with Dept. des Sols et de Génie Agroalimentaire, Faculté des Sciences de l'Agriculture et de l'Alimentation, Univ. Laval, Quebec, Canada. Author Genovese is with Planta Piloto deIngeniería Química, Camino “La Carrindanga” Km 7, CC 717, (8000) Bahía Blanca, Argentina. Direct inquiries to author Genovese (E-mail: dgenovese@plapiqui.edu.ar).
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  • Cristina Ratti

    1. Authors Raharitsifa and Ratti are with Dept. des Sols et de Génie Agroalimentaire, Faculté des Sciences de l'Agriculture et de l'Alimentation, Univ. Laval, Quebec, Canada. Author Genovese is with Planta Piloto deIngeniería Química, Camino “La Carrindanga” Km 7, CC 717, (8000) Bahía Blanca, Argentina. Direct inquiries to author Genovese (E-mail: dgenovese@plapiqui.edu.ar).
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  • This work has been financially supported by FQRNT (Fonds québecois de la recherche sur la nature et les technologies). Author Genovese is grateful for financial support from CONICET, Argentina, and the Ministère de l'Éducation du Québec, Canada. We thank MS. Mónica Araya for her help with experimental work and valuable discussions.

Abstract

ABSTRACT: Intrinsic stability and rheological properties of apple juice foams for foam mat drying were studied. Foams were prepared from clarified apple juice by adding various concentrations of 2 foaming agents of different nature: a protein (egg white at 0.5%, 1%, 2%, and 3% w/w) and a polysaccharide (methylcellulose at 0.1%, 0.2%, 0.5%, 1%, and 2% w/w), and whipping at different times (3, 5, and 7 min). In general, egg white foams were less stable but showed a higher degree of solidity (stronger structures), higher foaming capacity, and smaller bubble average diameter than methylcellulose foams. Foam stability increased with increasing concentrations of either methylcellulose or egg white. Increasing whipping times increased the stability of egg white foams only. Stability parameters (maximum drainage and drainage half-time) were correlated in terms of rheological parameters of the continuous phase (consistency index and apparent viscosity at 30/s, respectively). The correlations (R2= 0.766 and 0.951, respectively) were considered acceptable because they were independent of whipping time and foaming agent nature and concentration. Results on foam rheology obtained by dynamic and vane tests were in agreement, but the latter method was more sensitive. Optimal concentrations to obtain the most solid foams (0.2% methylcellulose and 2% to 3% egg white, respectively) were the same concentrations required for maximum foaming capacity. Based on this observation and previous models, an empirical expression was proposed to predict the degree of solidity (in terms of inverse phase angle and yield stress) only as a function of foam structural properties (air volume fraction and average bubble size). The model proved to be satisfactory to fit experimental results (R2= 0.848 and 0.975, respectively), independently of whipping time, foaming agent nature and concentration.

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