Hydrocolloids have an essential and irreplaceable role in the food industry, particularly in improving the quality of dairy products. Due to their diverse chemical structure, they are used in food formulations for various purposes, such as thickening, gelling, emulsifying, stabilizing, and fat replacement. Nevertheless, their mechanisms in the production process and their health benefits are still not fully understood.
Hydrocolloids are typically water-soluble polysaccharides or proteins with gelling ability. These compounds are used in the food industry for edible film formation, flavor encapsulation, increasing dietary fiber in gluten-free products, and extending shelf life. Thus, in numerous studies, researchers have referred to them as essential components of the food industry.
History of Hydrocolloids
The term “colloid” was first used in 1861 by Thomas Graham to describe substances that form gel-like structures. The term “hydrocolloid” was first introduced in 1916 for compounds that form jelly-like textures upon contact with water.
Definition and Classification
Hydrocolloids can be defined narrowly or broadly. In the narrow sense, they are polysaccharides and proteins used in the food industry to create texture, stabilize emulsions, and encapsulate bioactive compounds. In the broader sense, hydrocolloids include biopolymer systems such as emulsions, foams, hydrogels, liposomes, oleogels, and nanoparticles.
Sources of Hydrocolloids
Hydrocolloids can be derived from: plant sources (such as gum arabic, tragacanth, guar gum, locust bean gum, and starch), algal sources (such as agar, alginate, and carrageenan), microbial sources (such as xanthan gum, dextran, and pullulan), and animal sources (such as gelatin, proteins from dairy and eggs, and chitosan).
Additionally, modified and industrially produced hydrocolloids such as modified starches, microcrystalline cellulose, amidated pectin, methylcellulose, hydroxypropyl methylcellulose (HPMC), and carboxymethyl cellulose (CMC) are available on the market.
Structure of Hydrocolloids
Polysaccharides are long chains of monosaccharides connected by O-glycosidic bonds. Proteins are biopolymers made up of amino acids joined by covalent (peptide or amide) bonds.
Hydrocolloid Market
Due to increased awareness about the relationship between food and health, changes in lifestyle, and the growth of food processing technology, demand for healthy ready-to-eat foods is rising. This trend has led to significant growth in the use of hydrocolloids in food products.
The global hydrocolloid market was valued at USD 8.8 billion in 2018 and is projected to reach USD 11.4 billion by 2023. Innovation in hydrocolloid products, multifunctionality, and investment in research and development are key growth factors. However, strict food regulations and fluctuations in raw material prices are among the main challenges in this industry.
Safety of Hydrocolloids
Many hydrocolloids such as pectin, agar, starch, and gelatin have a long history of use in food products and are classified as GRAS (Generally Recognized as Safe). However, some hydrocolloids, such as degraded carrageenan (poligeenan), can be harmful, highlighting the importance of evaluating the safety of hydrocolloids.
Legal Requirements for Food Additives
Almost all hydrocolloids (except gelatin) are legally considered food additives, and their use in foods must be authorized by law. Chemical modifications are allowed in some cases, such as cellulose derivatives or propylene glycol alginate, but in most cases, only physical or enzymatic modifications (e.g., physically modified pectin) are permitted.
International Standards for Hydrocolloids
To ensure food safety, the Codex Alimentarius Commission (CAC) was formed in 1962 by the FAO and WHO. Before that, in 1956, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) was established and is still active today. It plays a key role in evaluating the safety of food additives, determining their maximum permitted levels, and issuing usage guidelines.
Consumer Acceptance of Hydrocolloids
Labeling of food additives is one of the most important factors in gaining consumer trust and acceptance. For instance, in the U.S., “methylcellulose” may be labeled as “carbohydrate gum,” and “HPMC” as “plant gum.” In the EU, “carboxymethyl cellulose” may appear on labels as “cellulose gum.”
Use of Genetically Modified Sources
One of the main concerns regarding hydrocolloids is the use of genetically modified organisms (GMOs) to increase yield. For example, researchers have tried to genetically engineer algae to boost alginate production and have worked on gum-producing trees with shorter growth cycles. However, the safety of these methods remains under investigation.
Functions and Main Applications of Hydrocolloids
Hydrocolloids perform multiple functional roles in the food industry, including acting as thickeners and gelling agents, stabilizers of emulsions and foams, and carriers for bioactive compounds. They can also be engineered into nanomaterials for advanced applications in the food and medical industries. Moreover, some hydrocolloid derivatives possess health-promoting properties and are recognized as bioactive compounds.
- Structural Agents: Thickeners and Gelling Agents
1.1. Thickeners:
Hydrocolloids increase the viscosity of food products by forming entanglements among their polymer chains. This property is useful in products such as soups, sauces, salad dressings, and various desserts. Factors such as molecular weight, molecular structure, pH, temperature, and the type of food matrix influence their thickening ability. Common thickening hydrocolloids include gum arabic, xanthan gum, CMC (carboxymethyl cellulose), tragacanth gum, modified starches, and galactomannans.
1.2. Gelling Agents:
Gels are three-dimensional structures that trap water and exhibit both solid-like and liquid-like properties. Depending on the type of bonds between polymer chains, gels are categorized as either physical or chemical. The gelling process can be influenced by factors such as temperature, pH, ions, enzymes, or the type and concentration of the hydrocolloid used. By controlling these factors, various gels can be produced, including hydrophilic or lipophilic gels, thermoreversible gels, and transparent or opaque gels.
- Stabilizers of Emulsions and Foams
2.1. Emulsions:
Many hydrocolloids can function as stabilizers for oil-in-water emulsions. Some also exhibit emulsifying abilities by adsorbing at the oil–water interface, thus preventing system instability. Widely used hydrocolloids in this regard include gum arabic, sugar beet pectin, modified starches, and hydrophobic celluloses. Proteins such as casein, whey, gelatin, and plant-based proteins (soy, pea, lupin) are also used as emulsifiers.
2.2. Foams:
In food foams, gas is dispersed within a liquid phase. The stability of this structure requires an interfacial barrier—usually a protein layer at the air–water interface. Foaming capacity and foam stability depend on the structural and surface properties of the hydrocolloid as well as factors such as pH, temperature, and concentration. Proteins such as casein, whey, and gelatin, along with polysaccharides like pectin, chitosan, and cellulose, are widely used to stabilize foams.
- Bioactive Compound Delivery Systems Based on Polysaccharides and Proteins
Proteins and polysaccharides, as the two main types of biopolymers, play a key role in designing delivery systems for bioactive compounds in food, medical, and pharmaceutical industries. Their biocompatibility, biodegradability, and non-toxicity make them ideal candidates for food-grade carriers. Their structural diversity—including molecular weight, linear or branched structure, charge, polarity, amphiphilicity, size, and reactivity—enables the design of carriers with specific desired properties.
Proteins and polysaccharides used in such systems are generally categorized as either water-soluble or water-insoluble:
- Water-soluble: casein, whey protein, agar, gelatin, carrageenan, alginate, pectin, guar gum, xanthan gum
- Water-insoluble: zein, chitosan, gliadin, starch, cellulose
These biopolymers can form various structures, including nanoparticles, films, fibers, hollow microcapsules, emulsions, and hydrogel particles. These structures are used to deliver compounds such as polyphenols, vitamins, carotenoids, unsaturated fatty acids, fish oil, and essential oils.
Bioactive Compounds and Health-Promoting Properties
In addition to their functional roles, many food hydrocolloids also offer health-promoting benefits. For example, whey protein and its derivatives possess several properties, including antibacterial and antiviral effects, immune system enhancement, bone health support, protection against cancer and cardiovascular diseases, reduction of oxidative stress, increased glutathione levels, lowering blood pressure, cholesterol, and LDL, improved blood sugar control, increased insulin sensitivity, reduced inflammation, positive effects on inflammatory bowel diseases, appetite suppression, and increased satiety. Many of these effects are attributed to bioactive peptides produced during the digestive breakdown of whey proteins, such as antibacterial peptides, ACE inhibitors, antioxidants, and blood sugar regulators.
Polysaccharides also offer a wide range of health benefits. One of the most important is their role as dietary fiber. Fibers can relieve constipation, stimulate bowel movement, increase short-chain fatty acid (SCFA) production, act as prebiotics and antimicrobials, inhibit the growth of pathogenic bacteria, and reduce fat absorption.
Dietary fibers include both soluble and insoluble types. This classification varies among nutritionists and chemists. For instance, konjac glucomannan (KGM) is nutritionally considered a soluble fiber, yet it does not dissolve well in water unless acetyl groups are added. Insoluble fibers such as cellulose and hemicellulose increase stool bulk but are non-fermentable, while soluble fibers are fermented by gut microbiota and release beneficial metabolites such as SCFAs.
Moreover, non-starch soluble polysaccharides such as guar gum, pectin, beta-glucans, and psyllium can form gels in the intestine, thereby slowing the absorption of glucose and fat. Another important class of polysaccharides includes sulfated compounds derived from seaweeds, which exhibit anticoagulant, antiviral, antioxidant, immune-regulating, osteoblast-differentiating, gastric mucosa-protecting, skin enzyme-inhibiting, and cholesterol- and triglyceride-lowering effects. These properties are associated with the molecular structure of the compounds, including molecular weight.
From an epidemiological perspective, many studies have reported an inverse association between fiber intake and the risk of colorectal cancers. Although definitive evidence is lacking, reduced fiber intake has been linked to an increased risk of such diseases.
- Functional Materials
Beyond their traditional uses, food hydrocolloids can be converted into various functional materials for use in food and medical industries. Examples include food packaging materials, artificial joint prostheses, and scaffolds for bone and cartilage tissue engineering.
5.1. Food Packaging Materials
Packaging materials are used to extend shelf life and provide consumers with information on product composition and nutritional value. In recent years, environmental and food safety concerns have driven interest in renewable and biodegradable packaging materials, typically derived from natural polymers.
Polysaccharides:
- Starch: Moderate oxygen barrier properties, but poor moisture resistance and low mechanical strength.
- Modified cellulose: Suitable for bakery goods, meats, fish, and confectionery.
- Chitin/Chitosan: Good oxygen barrier properties but limited long-term stability.
- Pectin: High water vapor permeability.
Proteins:
- Gluten: Good oxygen barrier, but weak CO₂ barrier.
- Soy protein: Brittle with poor water resistance.
- Gelatin: Low mechanical strength.
- Zein: Tensile strength similar to gluten but more permeable to oxygen.
Nanocomposites: Combining polysaccharides and proteins with other materials improves strength, stability, and oxygen absorption.
5.2. Biomedical Materials
While inorganic nanomaterials may pose cytotoxic risks, natural biopolymers such as polysaccharides and proteins are highly biocompatible and biodegradable, making them suitable for medical applications. Examples include chitin/chitosan, nanocrystalline cellulose, hyaluronan, silk proteins, and whey proteins, which can be used in the production of nanoelectrolytes, scaffolds, nanosponges, and selective membranes.
5.3. Templates for Synthesizing Inorganic Nanoparticles
Certain hydrocolloids, such as cellulose nanocrystals, can serve as templates for synthesizing inorganic nanoparticles. These nanocrystals enable the production of nanoparticles such as gold, silver, uranium, platinum, and titanium dioxide. This process results in stable nanoparticles with controlled sizes and improved chemical properties.
5.4. Other Types of Functional Materials
Food hydrocolloids can also be transformed into advanced functional materials such as:
- Porous biomimetic nanophotonic materials, whose reflective wavelengths can be tuned from the visible to near-infrared spectrum through simple modifications.
- Nature-inspired adaptive nanomechanical materials, used in flexible platforms for brain microelectrodes.
- Nanostructured membranes with selective permeability to different electric charges, useful for separating specific compounds.
- Enhanced polymer electrolytes with high ionic conductivity and suitable stability.
- Cleansing materials designed to remove organic pollutants or toxic heavy metals from the environment or food sources.
Future Trends
Over the past five decades, rapid developments in the food industry have led to significant progress in the science and technology of food hydrocolloids. These compounds play vital roles in flavor delivery, texture, processing properties, nutritional value, and health benefits of foods.
As consumer interest in healthy lifestyles continues to grow, attention to the biological and nutritional functions of hydrocolloids has also increased. While many health-promoting properties of natural polysaccharides and proteins have been uncovered, the physiological functions of some emerging compounds remain to be fully understood.
Moreover, hydrocolloids’ remarkable ability to form targeted food structures enables the design of future foods—such as products tailored for the elderly, specialized options for diabetic patients, low-sodium foods, or products with controlled textures and flavors for individuals with dysphagia.
Thanks to their mechanical flexibility and compatibility, these compounds are also finding applications in a wide range of areas such as targeted carriers for bioactive compounds or drugs, meat alternatives, artificial muscles and joints, and even bioelectronic components. Overall, the food hydrocolloids market is on a strong growth trajectory, with a promising future full of opportunities.
Conclusion
In recent years, food hydrocolloids have moved beyond their traditional roles and emerged as multifunctional materials in the food, medical, and environmental sectors. From biodegradable packaging and specialized food design to the development of advanced materials such as nanomembranes, enhanced electrolytes, and even artificial muscles, these compounds have demonstrated significant potential for innovation and future development. The continued expansion of this field highlights the key role hydrocolloids play not only in improving food quality but also in offering sustainable and intelligent solutions to current and future industrial challenges.
Source:
Fang, Y., Zhang, H. and Nishinari, K. (Eds.), 2021. Food Hydrocolloids: Functionalities and Applications. Springer Nature. DOI: 10.1007/978-981-16-0320-4
