Molecular gastronomy is the study of the chemical and physical processes that occur during food preparation. In view of this, new methods and techniques can be created or improved.
Microencapsulation is a process in which tiny particles or droplets are surrounded by a coating, or embedded in a homogeneous or heterogeneous matrix, to form small capsules.
Most edible oils are chemically unstable and susceptible to oxidative deterioration, especially when exposed to oxygen, light, moisture and high temperatures. Oxidative degradation leads to a loss of nutritional quality and the development of undesirable flavors, with consequences on the shelf stability and sensorial properties of the oil. Therefore, encapsulation by freeze-drying of salad dressing, composed of olive oil and lemon juice, aims to increase the stability of this food thanks to the decrease in water activity, contributing to the reduction of the weight and density of the product and reducing transportation and storage costs. Freeze drying is done using a simple physical principle called sublimation. Sublimation is the transition of a substance from the solid state to that of vapor, without first passing through an intermediate liquid phase.
The freeze-drying process consists of freezing the food so that the water it contains becomes ice, under vacuum, sublimating the ice directly into water vapor and sucking in the water vapor. Once the ice has sublimated, the foods are freeze-dried and can be removed from the machine. Emulsions, such as salad dressings, can quickly lose stability, unlike dry presentation which allows for an increase in shelf life, retaining functional and nutritional compounds for a longer time; Furthermore, it is easier to market. Food emulsions have a complex composition; their droplets are stabilized to varying degrees by proteins, small molecule surfactants (emulsifiers), and polysaccharides.
Alginates are natural polymers widely considered biocompatible and non-toxic (Thevenet, 1988). Carboxymethylcellulose (CMC), a typical hydrocolloid, has no direct influence on the taste and flavor of foods, but at the same time has a significant effect on gel formation, water retention, emulsification and aroma retention . In the food industry, CMC is used as a stabilizer, binder, thickener, suspending and water retaining agent, in ice creams and other frozen desserts, sauces and creams.
Maltodextrins are widely used in food emulsions as stabilizers and their addition is mainly carried out in difficult-to-dry materials.
Gum arabic is a complex heteropolysaccharide with a highly branched structure, with the main chain formed by d-galactopyranose units. It has been used as an encapsulating agent in microencapsulation by spray drying due to its good emulsifying ability and low viscosity in aqueous solution.
The microencapsulation process transforms oils into easily handleable solids and protects them from oxidation through a solid wall that acts as a physical barrier limiting the diffusion of oxygen.
Brazilian researchers have formulated an instant food emulsion containing olive oil and lemon juice using combinations of polymers, such as alginate (ALG), gum arabic (AG), maltodextrin (MD) and carboxymethyl cellulose (CMC) and freeze-dried, with the aim to develop a new microencapsulated product.
Particle size characterization, surface analysis by scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry were performed with the emulsions that showed good oil encapsulation.
Maltodextrin and gum arabic mixtures showed the lowest average particle size values. Furthermore, these samples exhibited rounded shapes and some depressions highlighted by scanning electron microscopy and were shown to be an amorphous material by X-ray diffraction.
The characterization of the samples indicated the suitability of gum arabic in combination with maltodextrin as the best mixture for microencapsulating the emulsion with 50% v/v olive oil and lemon juice, by freeze-drying. The size of the particles was smaller and their surface was homogeneous. Furthermore, X-ray diffraction showed that these samples were amorphous.
The glass transition temperatures of samples C (12.5 g/100 g of MD and 7.5 g/100 g of AG), 146.60 °C, and D (10 g/100 g of MD and 8.5 g/100 g of AG), 147.54 °C, were similar, since the type of polymers was similar.
It is therefore possible to microencapsulate an oil-in-water emulsion (1:1) by freeze-drying to instantly dress a salad.
