Texture and mouthfeel are attributes many consumers do not think about unless they are off, such as when a high-protein milk is gritty or ice cream lacks aeration. Visual appeal is important, too. Not just at the time of purchase, but through shelf life. A puddle of liquid on the top of a multi-serve container of plain yogurt the day after opening is unacceptable.

This is why product designers include ingredients with emulsifying and stabilizing properties into formulations.

Historically, they relied on highly effective chemical emulsifiers, such as monoglycerides and diglycerides, as well as sucrose esters. For stabilization, modified starch was an economical go-to ingredient, along with other hydrocolloids, some of which have been targeted by the food police. In this day and age of label scrutinization, formulators are turning to cleaner ingredients that provide desirable functionality.

Keeping it all together

Cows’ milk in the US is said to be 87.7% water, 4.9% lactose (carbohydrate), 3.4% fat, 3.3% protein and 0.7% minerals. The latter is referred to as ash. While composition varies by breed, feed, the stage of lactation and more, the milk from different cows is typically stored in bulk tanks and averages out to these numbers.

If you let a glass of direct-from-the-farm milk sit long enough, the fat rises to the top, while most of the other solids set on the bottom. To overcome this, fluid milk is homogenized. This physical process creates an emulsion, which is a heterogeneous suspension whereby microscopic droplets of one type of immiscible liquid are dispersed in another immiscible liquid. In the case of cows’ milk, it’s fat dispersed in the water. The same is true of plant-based products that contain fat.

It’s not enough to create the emulsion. The emulsion must remain intact through shelf life. That’s where emulsifiers come into play. Emulsifiers have a hydrophilic (water attracting) head and a hydrophobic (water repelling) tail. They prevent the emulsion from reverting back to separate phases through interactions that encourage droplet dispersion.

Low molecular weight emulsifiers are used for a number of functions in dairy products and dairy substitutes, explained Stephen Euston, professor, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, Scotland, UK, and an author of Food Emulsifiers and Their Applications. This includes interactivity with molecular surfaces, promoting fat crystallization and interacting with proteins.

Lecithin is one such emulsifier. It is naturally present in soybeans and egg yolks, making both functional ingredients in dairy and alt-dairy products. Lecithin is also commercially available as a stand-alone ingredient. It is generally recognized as safe (GRAS) by the US Food and Drug Administration.

In ice cream and whipped dairy emulsions, for example, the surface activity of such emulsifiers allows them to adsorb to the surface of air bubbles in foams, or to the surface of oil droplets in emulsions, thus facilitating formation of smaller bubbles and droplets and helping to control the stability, according to Euston.  

Product stability

Then there’s texture over shelf life. This is referred to as product stability.

“We want the texture to look and perform on the last day of product shelf life the same as it did on the first day it hit the stores. We do not want drastic changes to the texture over time,” said Ivan Gonzales, marketing director for plant-based dairy and dairy, Ingredion Inc., Westchester, Ill. “Typical problems to avoid are syneresis, hardening, losing viscosity and developing graininess. Changes to texture most likely will impact appearance and flavor release in the final product.”

When it comes to dairy products, consumers typically expect them to be smooth, creamy and void of standing moisture. They don’t want starchy or gummy lumps in sour cream, protein or mineral sedimentation in drinkable yogurt, or frozen crystals in ice cream. Such visual cues are indicators of product texture, which in turn influences how the product feels in the mouth, also known as mouthfeel. This is why texture needs to be a focal point during the early stages of product development and effectively managed throughout shelf life.

This is especially true for many refrigerated dairy and alt-dairy products. If not properly stabilized, viscosity may thicken or thin over a given period of time. Proteins may flocculate and cause grittiness. Gels may expel water (syneresis).

Hydrocolloids are a category of ingredients that help stabilize the emulsion. They are a group of long-chain polymers — carbohydrates and proteins — and are characterized by the ability to form viscous dispersions or gels by binding water. This function is alluded to in the name, where the prefix “hydro” means water and “colloid” means a gelatinous substance.

Some hydrocolloids have additional functional properties, including emulsification, aeration, suspension and encapsulation. These functions vary by application and by hydrocolloid.

Hydrocolloids work in combination with carbohydrate, protein and fat components in the dairy system. Blends are common, as they work synergistically to achieve texture and stability goals with lower total addition levels. Thus, hydrocolloid blends may reduce formulation costs.

Economics are always a product development consideration. Hydrocolloids have proven to have a positive impact on the bottom line — remember, their primary function is to keep water in the system. This improves yields and profits.

Hydrocolloids also play an important role in keeping ingredients stable in dairy product systems. This includes identifiable pieces such as nuts, superfruits and cereals (think oats in yogurt), as well as vitamins, minerals and other nutrients, including fiber and protein.

Some hydrocolloids form thermoreversible gels, where gelation occurs after the hydrocolloid dissolves in solution and is cooled. When heat is applied, the gel melts or dissolves. Gelation temperature and melting point varies by hydrocolloid.

This is exemplified by gelatin dessert, which melts in the mouth at body temperature. Gelatin can absorb five to 10 times its weight in cold water. In yogurt, gelatin prevents whey from being expelled from the casein gel. This is because the gelatin molecules form a lattice in the casein gel during the gelling process that gets stabilized by hydrogen bonding.

Hydrated gelatin contributes lubricity to a system. Together with the melt-in-the-mouth attribute, gelatin makes a choice fat replacer in dairy foods. Due to its foam-building properties, gelatin can be used to replace some of the fat content of foamed milk-based desserts, such as mousse.

Other hydrocolloids form non-thermoreversible gels, also called thermally irreversible gels, and will not liquefy when heated. They may soften or shrink, which is also referred to as retrograde. In other words, the gel remains mostly intact once formed. When they retrograde, syneresis takes place. That puddle of liquid forms on the surface.

Native starches typically form non-thermoreversible gels and will retrograde over time. Hence, historically chemically modified food starches have been used to bind moisture in dairy products, as modification adds stability and resistance to retrogradation and syneresis. With the trend towards cleaner labeling, formulators are revisiting the use of native starches, in particular those that have been physically modified for improved functionality.

There are also some hydrocolloids that do not form any type of gel on their own, but will do so in the presence of other compounds. The challenge lies in finding the right balance between the different gelling characteristics. This allows for products with superior moisture retention and desirable mouthfeel and texture.

Xanthan gum, for example, is produced by microbial fermentation. It is a non-gelling hydrocolloid that hydrates rapidly in cold water to give a reliable viscosity, with a little going a long way. Its consistent water holding ability makes it a very effective tool for controlling syneresis. When used in combination with carrageenan, xanthan contributes synergistically to the formation of a thermoreversible gel, meaning that less carrageenan is required to form the gel.

Guar gum is also commonly used in cultured dairy applications to prevent the development of standing water. Guar gum is obtained from plant seeds. The powdered ingredient disperses and swells almost completely in cold water to form a highly viscous solution. Like xanthan, it is not self-gelling, and has an extremely high water-binding capacity.

Pectin gaining traction

Pectin is a carbohydrate hydrocolloid that is gaining traction as a stabilizer in dairy. This polysaccharide has many functions. It also is an upcycled ingredient, thereby coming with a sustainability story.

“Pectin is made from the byproducts of juice production, citrus peels and apple pomace,” said Christine Addington, enterprise customer technical lead, Cargill, Minneapolis. “Rather than discard these leftovers, Cargill relies on them to produce pectin, a time-tested ingredient known for its thickening, gelling and protein stabilization properties.”

Citrus fiber ingredients have also long relied on these fruit juice processing waste streams. Ingredion entered this space with what one might call a “double upcycled” ingredient, as the company uses the waste streams from the pectin industry. Ingredion said that its new citrus fibers help manufacturers replace undesirable and high-cost ingredients while providing unique textures and sensory experiences.

“As consumers continue to demand new products with naturally sourced, authentic ingredients, better nutrition and appealing packaging claims, we recognized the need for cost-effective, highly accepted ingredient options that can do more in terms of functionality and consumer preference,” said Deepa Sethi, global senior manager and innovation business lead, texture solutions, Ingredion.

The minimally processed, upcycled citrus fibers support on-pack claims, including “derived from natural sources,” non-GMO, “fruit-based” and “source of/high in dietary fiber.”

“These new citrus fibers are an ideal solution for brands to utilize naturally sourced, consumer preferred ingredients that support simple labels, desired packaging claims and sustainability goals without compromising the eating experience or their margins,” Sethi said.

Citrus fibers continue to grow in popularity as an ingredient option among consumers, with 85% claiming they accept and like them on their label, according to Ingredion’s 2023 ATLAS proprietary consumer research. The same study indicates that what’s on the label is also growing in importance, with 79% of global consumers stating they want to recognize a product’s ingredients and 50% claiming they are checking food ingredients more than last year.

Inulin as texture enhancer

Inulin is another fiber with hydrocolloid attributes. When used in dairy products, inulin acts as a texture enhancer and a fat replacer, all while mimicking the mouthfeel and creaminess of fat. It is also a soluble fiber that will help increase the fiber content of the final product.

A blend of hydrocolloids is often necessary when formulating alt-dairy products, as they rely on multiple ingredients to replace cows’ milk. This is especially true in high-protein formulations.

“The combination of different plant-based proteins has to harmonize in terms of flavor, and have a smooth, pleasant mouthfeel,” said Linda Eitelberger, product manager, Planteneers, Hamburg, Germany. “This is often a challenge with protein-rich products.”

The company recently rolled out a functional hydrocolloid system specific for fermented oat dessert.

“This creamy dessert can be mixed with many different fruit preparations to get a final product with 11% fat, 10% sugar and 3% protein,” said Eitelberger. “In taste and texture, this plant-based dessert is comparable to fruity cream yogurts and quark desserts. The system consists of plant protein, modified starch and emulsifier. It can be processed into a dessert easily on the standard equipment used in yogurt production.”

Planteneers also developed a solution for a plant-based mascarpone. This functional system of starch, plant protein, plant fiber, pectin and emulsifier is worked into a smooth base with water and fat. It features a rich mouthfeel and neutral taste. Manufacturers can bring it to market as a pure product in its own right, or work it into vegan tiramisu or similar layered desserts. Solutions for alternatives to cream cheese or quark provide further inspiration. Both products are very well suited to making plant-based cheesecake versions or corresponding desserts.

Through careful blending with emulsifying and stabilizing properties, products can maintain a desirable shelf life. Ensuring quality through the expiration date helps reduce food waste and helps consumers on their sustainability journey.