Instant foods, such as soups, have a long shelf life and are easy to handle—they generally require only the addition of hot or cold water to reconstitute them. A common way to produce instant soups is by dehydrating fresh products such as vegetables. After drying and pulverizing, the powders need to be granulated to improve the handling of the final product. For granulation, liquid binders are needed. Water is the most commonly used liquid binder, but oil could enhance the granulation properties.
Andrea Claudio Santomaso, University of Padova, Italy, and colleagues have tested alternative liquid binders for the granulation of different vegetable powders (e.g., spinach, beetroot, and carrot). Instead of water, they tested the sequential addition of oil and water, as well as an oil-in-water emulsion. As expected, the raw, ungranulated powders did not disperse very well during rehydration with hot water and formed unwanted lumps. The more starch they contained, the more lumps were formed. Especially at higher temperatures, the starch swells and creates a gelatinous layer around the dry particles, thereby preventing dispersion.
For the granulated powders, rehydration tests showed better dispersion and fewer lumps for the granules made with an oil-in-water emulsion than for those prepared by the sequential addition of oil and water. The granules prepared with the emulsion were smaller and disintegrated more readily due to the homogeneous distribution of the oil. This, in turn, is advantageous during rehydration and dispersion. The smaller numbers of lumps improved the overall texture quality of the vegetable soup after rehydration. Overall, the work shows that using an oil‐in‐water emulsion for granulation can positively affect the properties of dried food powders.
- Reconstitution of Food Powders Granulated with Oil-in-Water Emulsions,
Anna Rieder, Erica Franceschinis, Martina De Santi, Nicola Realdon, Andrea Claudio Santomaso,
Chem. Eng. Tech. 2020.
The article is part of a Chemical Engineering & Technology Special Issue on Particle and Powder Technology