Instant coffee foam: An investigation on factors controlling foamability, foam drainage, coalescence, and disproportionation

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.

Evaluation of the Physicochemical and Functional Properties of Aquasoya (Glycine max Merr.) Powder for Vegan Muffin Preparation

“…In addition, the foam structure was analyzed using a Krüss Dynamic Foam Analyzer DFA 100 (Krüss, Germany). The foam was obtained by spraying air in a 40-mm tempered glass column with a filter (12–25 µm) at a set gas flow rate of 0.3 L/min for 15 s [ 16 ]. The foam structure was indicated by the bubble size and count.…”

Experimental study of rheological behavior of foam flow in capillary tubes

“…The mean area of the bubbles (as they appear against the tube wall) was estimated from 2D images taken from above of the tube wall at the 3 cm middle part. The estimations of the mean bubble area are based on the previous studies [53,63]. For instance, Tong et al [63].…”

“…According to this study, the mean bubble area is the average cross-sectional area of bubbles obtained by image analysis over a specific area in a 2D foam. Shankaran and Chinnaswamy [53] determined the size of foam bubbles to study factors controlling foamability, foam drainage, and bubble coalescence of instant coffee. The experiments were carried out in a glass column, which made it possible to capture an image of the two-dimensional structure of the foam.…”

“…The experiments were carried out in a glass column, which made it possible to capture an image of the two-dimensional structure of the foam. As in the study of Tong et al [63]., Shankaran and Chinnaswamy [53] analyzed foam images in ImageJ software to determine the mean foam bubble size.…”

Investigation of the factors affecting foamability and foam stability of cold brew coffee

“…On the other hand, lipids have a negative effect on foamability but contributed to espresso foam stability. 7,13 Coffee foam studies have been mainly focused on the espresso 6,13,[27][28][29][30] and instant 6,[31][32][33] coffee beverages. To our knowledge, research on the foaming properties of cold brew coffee is currently non-existent in the literature.…”