Adhesion in Foods
Adhesion in Foods
An adhesive is most simply described as a substance that causes one body to stick or adhere to another. The oldest adhesives were almost certainly fish or bone glues and these have been in use for many thousands of years. Due to the importance of glues and adhesion, the libraries are full of excellent books on the topic, covering: adhesion; adhesion molecules; adhesion of pathogens and bacteria; adhesion technology; fundamentals of adhesion; adhesion related to medicine and in health and disease; surface treatment and adhesion; adhesion of cells, viruses, and nanoparticles; adhesion and adhesives; adhesion promotion techniques; adhesion measurement methods; adhesion of dust and powder; adhesion and bonding in composites; and adhesion measurements of films and coatings, to name but a few.
Adhesion is a very important feature in food throughout its manufacturing, packaging, and storage. Nevertheless, to the best of our knowledge, there is not even one published manuscript that is fully devoted to food adhesion. During many years of research and development at the Hebrew University of Jerusalem and in the industry, I have been involved in studying hydrocolloid wet glues, adhesion related to edible coatings, adhesion in the manufacturing of multilayered food products, pressure-sensitive adhesives, and tests to check adhesion in foods. Furthermore, I have written several chapters on adhesion related to hydrocolloids, foods, and specialized adhered textures in both my previous books and those of others. The following proposed manuscript outline consists of chapters that are all devoted to the fascinating topic of adhesion in foods.
Chapter 1: Adhesion: Definition and Nomenclature
To the layman, adhesion is a simple matter of how well two different materials stick together, and adhesion measurements provide some indication of the force required to separate them. This chapter will steer the reader to a more scientific definition of adhesion that can be useful for a variety of purposes. Also included are comments on nomenclature and usage and a short review of the history of adhesion.
Chapter 2: Adhesion Mechanisms and Measurements
Mechanisms involved in materials' adhesive processes are related to many fields, including mechanics, thermodynamics, and chemistry. Many theories have been developed to explain adhesion. These include mechanical interlocking, wetting and thermodynamic adsorption, electrostatic adhesion, diffusion, chemical adhesion, and weak boundary layers, and they are all briefly reviewed in this chapter. An overview of useful adhesion-evaluation methods is also provided, among them weighing, UV absorbance measurements, and adhesive loss measurements. In addition, adhesion strength measurements are reviewed, as well as destructive and non-destructive methods related to mechanical testing of adhesive joints by tensile test, shear test, and peel test. These tests can be regarded as static tests. Other adhesive tests are also described, including dynamic loading, creep, impact, and fatigue.
Chapter 3: Stickiness of Foods and its Relation to Technological Processes
Stickiness is a common characteristic of foods. This chapter gives examples of stickiness in different food types. These include, but are not limited to, stickiness of dough and rice, sticky sweets, stickiness in sugar-rich foods-soft cookies, toffees, and dried fruit-and in some dishes, such as sticky toffee pudding, stickiness of pasta through cooking, stickiness of semi-solid foods and food powders, stickiness of non-fat processed cheeses, jams, food powders, and jaggery granules. This chapter also provides a general introduction to other chapters in which various types of food stickiness/adhesion are discussed in more depth. The relationships between technological processes and stickiness are also described, for example, in spray-drying and freeze-thawing processes