What are the properties of interfaces covered with surface active components present in beer ?
Reference: Surface rheology and morphology of beer protein and iso-humulone at air-liquid surface. Y. Lu; B. Choi; T. Nylander; B. Bergenståhl; L. Nilsson; Food Hydrocolloids 108 (2020) 105897.
The formation of foam is very often observed when pouring a beer. However, the behavior of the amphiphilic components contributing to stabilizing this foam is not fully understood. In this paper, the main surface-active components present in beer; protein from barley and iso-humulone from hop are characterized at the air-water interface. The behavior of single components, premixed solutions and sequentially added components are characterized in terms of surface tension and surface rheology using a drop tensiometer (TRACKER™ by TECLIS) and the morphology of the adsorbed layers are probed with Brewster angle microscopy. The combination of the protein and the iso-humulone shows synergistic effects consisting in increasing the interfacial surface pressure and elasticity. Different behaviors have been observed depending on the experimental conditions (premixed solutions or sequentially added molecules) proving that protein/iso-humulone interactions govern the interfacial properties in beers.
TECLIS product: TRACKER™ automatic drop tensiometer with Phase Exchange
Key words: Beer, iso-humulone, protein, surface tension, dilatational rheology, sequential addition, Brewster angle microscopy
What are the parameters governing the generation and the properties of
the “crema” foam ?
Reference: Crema-Formation, Stabilization, and Sensation. B. Folmer; I. Blank; T. Hofmann; The Craft and Science of Coffee; dx.doi.org/10.1016/B978-0-12-803520-7.00017-7.
Espresso represents a large percentage of coffee consumed today. One of its main characteristics is the formation of a dense foam called “crema”. In addition to providing a pleasant consumer’s experience, this foam is used by experts to judge the quality of the coffee extraction (degassing, grinding, tempering and water pressure). From a scientific point of view, the physico-chemical properties aspects of “crema” (foamability, stability) can be studied as a function of the coffee composition. The effect of roasted caffeic acid and sucrose palmitate on crema are hence characterized in this chapter. Foaming experiments showed that the foam volume was significantly increased with increasing levels of roasted caffeic acid (more than 60% increased foam volume was with 0.07% roasted caffeic acid). At a smaller scale, the effect of roasted caffeic acid and sucrose palmitate on the structure of the crema are probed with a foam analyzer (FOAMSCAN™ Foam Analyzer by TECLIS). The images of the foams are analyzed with the Cell Size Analysis software by TECLIS, and the results show that the addition of sucrose palmitate results in an accelerated drainage of the foam.
TECLIS product: FOAMSCAN™ Foam Analyzer & Cell Size Analysis software
Key words: Coffee, crema, foamability, foam stability, physico-chemical properties
How do pH and temperature impact the foaming and interfacial properties of camel and bovine whey proteins ?
Reference: The foaming properties of camel and bovine whey: the impact of pH and heat treatment. R. Lajnaf; L. Picart-Palmade; E. Cases; H. Attia; S. Marchesseau; M. A. Ayadi; Food Chemistry; doi.org/10.1016/j.foodchem.2017.07.064.
The effect of pH value and heat treatment on the foaming properties of bovine and camel milk whey is investigated in this paper. First, foaming experiments showed that acid whey led to the maximum foamability for both milks which has been attributed to the proximity of the isoelectric points of the whey proteins (pH 4-5). While heating increased the foaming properties of camel and bovine whey, stability of foam greatly increase only for the acid camel whey. Then, experiments at the scale of the interface using a drop tensiometer (TRACKER™ by TECLIS) showed that acid camel whey preserved its surface-active properties at air water interface even after heating. This finding allows hence to explain the remarkable foaming properties of acid camel whey.
TECLIS product: TRACKER™ automatic drop tensiometer
Key words: Camel and bovine whey, foaming properties, foam stability, surface tension, dilatational rheology, viscoelastic modulus, pH, heat treatment
How does the drying process control
the properties of mango powder and its reconstituted suspension ?
Reference: Rehydration of mango powders produced by cast-tape drying, freeze drying, and spray drying. M. F. Zotarelli; A. Durigon; V. M. d. Silva; M. D. Hubinger; J. B. Laurindo; Drying Technology 2020.
Food powders are largely used because of their small bulk weight, their chemical stability at ambient temperature, etc. Different drying methods can be used to obtain powders, in this paper mango powder is studied and three drying methods are investigated: CTD (cast-type drying), FD (freeze drying), and SD (spray drying). At the scale of the powder, wetting time experiments, solubility experiments and contact angle measurements using an optical tensiometer (TRACKER™ by TECLIS) have been performed. As shown in the figure where water droplets are placed on a powder layer, powders obtained with CTD showed the smallest contact angle and the presence of Maltodextrin increases the contact angle. These findings have been corroborated with the wetting time experiments. At the scale of the reconstituted suspensions, pseudoplastic behaviors have ben observed thanks to rheology experiments; however, pulps reconstituted from CTD and FD powders presented rheological behavior closer to that of the original mango pulp while SD is more indicated for juice preparations because of its rheological properties.
TECLIS product: TRACKER™ automatic drop tensiometer
Key words: Food powder, drying process, wetting time, contact angle, solubility, rheology