Layering of Sodium Caseinate Submicelles in Thin Liquid Films— A New Stability Mechanism for Food Dispersions

✍ Scribed by K. Koczo; A.D. Nikolov; D.T. Wasan; R.P. Borwankar; A. Gonsalves

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 327 KB
• Volume: 178
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1996.0167

✦ Synopsis

adsorption of various proteins (3, 5) and the competition Drainage and stability mechanisms of thin foam and emulsion between proteins and small molecule surfactants (5,8). films containing aqueous sodium caseinate solutions were investi- Clark et al. (9) studied the stability of foam lamellae congated. We found that the films thin stepwise by stratification. The taining b-lactoglobulin and Tween 20 and found that the heights of the film step-transitions were in the same range as the film stability depends on the surface viscosity and the film effective size of the casein-aggregates, the so-called submicelles became unstable when the surface was mobile.

(about 20 nm). This showed that microlayering of submicelles

In dairy products (ice cream, whipped toppings, etc.), takes place in the stratifying film and, at a step-transition, a layer milk proteins, such as casein, play the stabilizing role along leaves the film. The number of steps increased with increasing with nonionic surfactants. The various casein molecules have caseinate concentration. Increase of temperature accelerated the step-transitions. At a lower temperature the drainage was not only a relatively high hydrophobicity (10, 11) and therefore they slower but the last transition was inhibited and a final film conaggregate in aqueous solution. In milk, so-called casein mitaining a layer of submicelles formed. The stepwise film thinning celles can be found, which are large (about 100-300 nm) process could also be stopped at high film thicknesses by decreasaggregates. The casein micelles consist of many, small caing the film size, i.e., by forming smaller drops or bubbles. The sein aggregates, so-called submicelles, which are bound tostepwise thickness transition results could be explained by the gether by calcium and phosphate ions (11, 12). Sodiumtheory of ''vacancy'' mechanism. It was found that the film and caseinate is generally prepared from milk casein either by the emulsion are very stable if the drained emulsion film contains dialysis (11, 13) or by precipitation at pH 4.6, which is layer(s) of submicelles. This new mechanism of microlayering in followed by washing and then adjusting the pH to 6.7 by foam and emulsion films can be important in the stability of food NaOH addition (11, 12). In these processes, most of the systems because the concentration (0.1-4 wt%) and temperature calcium and magnesium are removed from the casein and (25-80ЊC) ranges where the phenomenon was observed are similar to those found in practical applications.