Fat and moisture encapsulation for alternative protein products

Current challenge

The juiciness, tenderness, and palatability of conventional meat depends on the product’s fat and water holding capacities and stabilities. Additionally, the taste, shelf-life, and texture of products like milk, yogurt, and egg yolk depend on the stability of mixed fat and water phases.

Two types of animal fats that are difficult to replicate are:

1. Animal adipose tissue, which is composed of fat droplets surrounded by a collagen matrix that prevents the release of fat molecules during cooking. 
2. Colloidal fat globules, which are homogenized suspensions of emulsified fats and proteins in water.

Generally, animal fats contain more saturated fatty acids with longer, more hydrophobic carbon chains than plant lipids. As a result, animal fat is typically solid at ambient temperatures and will gradually melt with heat. On the other hand, plant lipids, which are mostly composed of shorter, unsaturated fatty acids, are liquid oils at ambient or cooking temperatures. Because unencapsulated liquids are prone to leaching and unsaturated fatty acids are susceptible to oxidation, native plant oils are easily lost or damaged during manufacturing, storage, and cooking. While modifications to plant lipids, like hydrogenation, can increase their degree of saturation, these transformations lower the end product’s nutritional benefits by introducing trans and saturated fatty acids. However,  fermentation-derived fats and cultivated fats provide alternate methods for producing fats that are identical to or that behave similarly to animal fats.

Water retention similarly plays an important role in the organoleptic properties and stability of meat analogs. Water holding capacity and retention are also profoundly influenced by a variety of environmental factors, such as pH, ionic strength, and temperature, as well as product intrinsic characteristics, like porosity and hydrophilicity.

Encapsulation techniques have demonstrated promise for absorption, retention, and stabilization of lipids and water. These methods should be tested for alternative meat products that mimic the natural adipose tissue matrices of animal fats, the colloidal systems produced by milk proteins and fats, or the high percent of water in animal muscle tissues.

Proposed solution

Encapsulation of fat and moisture can be achieved using cultivated, fermentation-derived, and plant-based meat technologies. 

Cellular agriculture technology allows researchers to directly cultivate animal fat cells, but there is room for optimization through development of immortal adipose cell lines that can be grown in low-cost, serum-free culture media. The challenges associated with growing these cells are examined further in Fish et al. 2020. Cultivated fat can then be encapsulated within a matrix to create adipose tissue. Potential food-safe extracellular matrix materials to be tested include animal-free collagen, alginate, fungi-derived chitosan, texturized vegetable protein, tofu, synthetic polymers, or other biomaterial 3D scaffolds from animal-free sources. With advances in 3D tissue engineering, adipose tissue could be made entirely in vitro with cell-cultured ingredients. Further research needs include tuning of optimal fat cell attachment, proliferation, and differentiation. This process tends to be easier using native animal cell scaffolds, which naturally contain necessary cell growth and structuring pathways, rather than using other biomaterials, so more animal-free biomaterial research is needed.

One fermentation-derived solution would be to produce and encapsulate fats within oleaginous yeast, which is discussed in detail in another GFI solution.

When choosing formulation strategies to encapsulate lipids, the desired end product properties are important. End products like emulsion-based meats or colloidal systems (e.g., milk) require encapsulating and stabilizing fats in a mostly hydrophilic/aqueous environment. Some novel strategies that could be further explored for alternative meat, egg, and dairy emulsion products focus on improving oil-in-water or water-in-oil-in-water emulsion systems with superior emulsifiers, binders, and emulgel/biogel formation (i.e., cross-linked emulsions with improved strength and stability). Many plant proteins have good emulsification properties and could be explored for thier ability to incorporate fats into alternative protein products.

End products that differentiate heterogeneous mixtures of distinct fat- and muscle-like areas of the product require semi-solid matrices that increase lipid melting temperatures and prevent leaching of lipids from the end products as they are stored, cooked, or consumed. These matrices can serve to stabilize regions of marbling. Oleogels are an emerging technology involving the incorporation of native plant lipids into lipophilic matrices (e.g., synthetic cellulose derivatives or waxes), producing a stable semi-solid similar to animal adipose tissue. Likewise, oleopastes and oil-filled aerogels/xerogels are variations on oleogels that could be optimized for fat encapsulation.

Moisture encapsulation solutions mostly focus on optimizing an end product’s preparation conditions (pH and ionic strength) and increasing an end product’s intrinsic water holding capacity and retention with gelling agents and other hydrophilic formulation components. Biopolymers (e.g., proteins and polysaccharides) tend to have high water holding capacities and can be optimized for end product moisture retention. These ingredients could be derived from crop fractionation or precision fermentation.

Anticipated impact

Encapsulation strategies for fats and water in alternative protein products provide opportunities to improve end product palatability, juiciness, texture, and flavor. Enhancing liquid retention can further improve product storage and cooking stability, and therefore prolong shelf life and reduce food waste. Additionally, in vitro cultivation of adipocytes could be finely tuned for specific lipid profiles with optimal organoleptic, nutritional, and sensory properties. Semi-solid matrices of lipids, such as oleogels, allow for the inclusion and stabilization of healthier unsaturated plant oils while improving their functional properties. Moreover, fat- and water- soluble flavors, nutrients, and aromas can be co-encapsulated in a marinade to improve ingredient stability and end product flavor and nutrition.

Related efforts

• Paragon Pure sustainable fats for plant-based meat upcycling rice bran oil and wax to create oleogels.
• Lypid is creating a plant-based biomimic fat with good consistency and melting properties using physics and fluid dynamics.
• Peace of Meat/Meatech is creating a cultivated fat and offers samples for plant-based meat companies.
• Enhancing the water holding capacity of model meat analogues through marinade composition (Cornet et al. 2021).

GFI resources

Formulating with animal-free ingredients

GFI scientists explain how ingredients derived from plants and fermentation can be used to create animal-free meat, egg, and dairy alternatives.