Journal
FOOD HYDROCOLLOIDS
Volume 112, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.foodhyd.2020.106354
Keywords
Foamability; Foam stability; Surface excess concentration; Antifoam; Bubble shrinkage; Spectroscopy
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Funding
- Science and Engineering Research Board (SERB), Government of India [PDF/2018/000013]
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The study isolated foaming fractions from spent coffee grounds to investigate their foam properties. Results showed that a high molecular weight foaming fraction from defatted robusta spent coffee grounds exhibited higher surface activity, comparable foam stability, and greater foamability than synthetic surfactants. Additionally, coffee oil was found to act as an antifoam agent by retarding the foam-forming and stabilizing activities of both spent coffee grounds-based and synthetic foaming agents.
Development of plant-based foaming agents is of relevance to the food industry. The present study hypothesizes that (1) foaming fractions from spent coffee grounds (SCG) may exhibit equivalent or superior foaming properties than synthetic surfactants and that (2) the coffee oil present in SCG could act as antifoam. Foaming fractions were isolated from the defatted and whole SCG (obtained after the hot water brewing of medium roasted and coarse-ground Arabica and Robusta coffees), after a series of extraction, concentration, and purification steps. The surface activity, foamability, and foam stability of SCG-based foaming fractions were studied in comparison with synthetic surfactants. The foam structure evolution and molecular fingerprint of foaming fractions were elucidated using light microscopy and infrared spectroscopy, respectively. Further, the surface activity of coffee oils was assessed. The high molecular weight foaming fraction obtained from defatted robustaSCG exhibited higher surface activity, comparable foam stability, and greater foamability than synthetic surfactants. The role of coffee oil as antifoam was ascertained by its ability to retard the foam-forming and stabilizing activities of SCG-based and synthetic foaming agents. Bubble breakage and shrinkage were found to be the antifoaming mechanisms of coffee oil. Infrared spectra of the foaming fractions provided insights into their composition.
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