Food Emulsifiers and Stabilizers - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 207

TABLE 7.1
Typical Food Colloids

Types of
Emulsion

Method of
Preparation

Mechanism of
Stabilization Food

1 Milk O/W Natural product Protein membrane

2 Cream A + O/W Centrifugation As (1) + particle

stabilization of air

3 Ice cream A + O/W Homogenization As (2) + ice network

4 Butter and margarine W/O Churning and invotator Fat crystal network

5 Sauces O/W High-speed mixing and

homogenization

By protein and
polysaccharide

6 Fabricated meat products O/W Low-speed mixing and

chopping

Gelled protein matrix

7 Bakery products A + O/W Mixing Starch and protein network

Abbreviations: O = oil, A = air, W = aqueous phase.

From Darling, D. F. and Birkett, R. J., Food Colloids in Practice, in Food Emulsions and Foams,
Dickenson, E., Ed., Royal Society of Chemistry, London, 1987, 1. With permission.

processing of food products often results in the formation of cell membrane residues,
which function as food emulsifiers or stabilizers forming interfacial films consisting
of lipoproteins, glycolipids, etc.
There are several reasons why food emulsions are important to the food manu-
facturer. A major consideration is the improvement of palatability, mouthfeel, texture,
and general appearance in systems containing both oil and water. Olive oil on its
own may be too greasy to taste, but is becoming widely acceptable in the emulsified
oil-and-vinegar salad dressing. The two immiscible liquids are both required because
some flavor ingredients are insoluble in the salad oil, whereas others are insoluble
in the vinegar. Food systems and food emulsions have been reviewed in great detail
by many scientists. Many excellent topics on the subject are available, and many
comprehensive review articles have been published. 1-11 The subject has been inves-
tigated from various angles and points of view: mechanistic and theoretical aspects
of emulsion formation (adsorption, surface characteristics, film formation, rupture,
and droplet formation); instability considerations (thermodynamics, kinetics, molec-
ular, surface forces, mechanical statistics, etc.), and the role of the surfactant (chem-
ical and structural requirements). Descriptive (macroscopic and microscopic) char-
acterization and analysis (of components including surfactants) were extensively
documented. 12-15 Systems like baked goods, 15 meat emulsions, 16 and milk and dairy
products 16 were examined in view of the role that emulsifiers and stabilizers play.
More practical aspects of food emulsions have been described by food technologists
in terms of formulations, methods of preparation, palatability, rheology, and stability.
This chapter describes food systems and food emulsions from the food emulsifier
perspective using natural and synthetic emulsifiers.