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Instant coffee foam: An investigation on factors controlling foamability, foam drainage, coalescence, and disproportionation
Author(s) -
Shankaran Padma Ishwarya,
Chinnaswamy Anandharamakrishnan
Publication year - 2019
Publication title -
journal of food process engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 45
eISSN - 1745-4530
pISSN - 0145-8876
DOI - 10.1111/jfpe.13173
Subject(s) - coalescence (physics) , sparging , disproportionation , bubble , aeration , volumetric flow rate , materials science , chemistry , thermodynamics , chemical engineering , mechanics , physics , organic chemistry , astrobiology , engineering , catalysis
Abstract Foamability and foam stability mechanisms of instant coffee foam were elucidated by varying the total solid content (10–40% w/w), gas flow rate (0.2–0.5 L/min) and gas sparging time (30–45 s). Maximum foam volume obtained after gas sparging was used as the measure of foamability. Foam stability was estimated from the rates of foam drainage, bubble coalescence, and disproportionation. Foamability was majorly influenced by the gas flow rate. Coffee foam exhibited three patterns of destabilization: (a) coalescence; (b) coalescence followed by disproportionation; and (c) partial coalescence. Differences in the mode of coffee foam destabilization can be attributed to the variations in initial bubble size and the manner in which the bubble size distribution evolves with time. The optimum conditions to obtain maximum foam volume and stability were 10% solid content of coffee solution, 0.4 L/min of gas flow rate, and 33 s of gas sparging time. Practical Applications The results of this study explain the underlying reasons for the metastability of coffee foam. The inferences derived from this research work can be used to improve the stability of coffee foam and produce newer types of aerated coffee‐based beverages.