Plant-based meat alternatives are entering consumer markets on a hitherto unseen scale because of the promise of more sustainable, healthy alternatives to real meat. They are being marketed based on the need to create a modern food supply that is better for humans, animals, and the environment. Adopting a more plant-centric diet in the highest-income nations, even though they account for only 17 percent of the global population, could cut greenhouse gas emissions by around 61 percent, while also increasing carbon sequestration.¹ In 2020, around 13 million metric tons of alternative proteins were consumed globally.² The global market for plant-based alternatives is forecast to reach USD $85 billion by 2030, up from USD $4.6 billion in 2018.³

How are Plant-Based Meats Made?

The awareness of plant-based meat alternatives has grown rapidly in recent years, but they have been produced and consumed for over a thousand years.⁴ In ancient Asian civilizations, a variety of meat analogues were developed, including relatively simple derivatives obtained from soybeans (like tofu and tempeh) or wheat (like seitan).⁵ A few decades ago, texturized vegetable protein (TVP) was developed as a replacement for meat by extruding defatted soy meal, soy protein concentrates, or wheat gluten.⁶  

More recently, a new generation of plant-based meat alternatives has been created for meat lovers. These products are designed to accurately simulate the desirable look, feel, and taste of real meat products. As their popularity increases, questions emerge about the safety and nutritional risks involved in switching from an omnivorous to a more plant-based diet. Several potential challenges are associated with food safety and nutrition, including different kinds of chemical and microbial contaminants in the ingredients used, food adulteration issues, high levels of food additives, the use of genetically modified ingredients, mislabeling, new sources of allergens, vitamin or mineral deficiencies, and changes in protein quality. It is, therefore, critical to consider these issues when developing the next generation of plant-based foods to ensure that they are safe and nutritious, as well as good for the environment.

The production of plant-based meat alternatives consists of four main stages:⁷  

1. Protein isolation and functionalization: The proteins are extracted from plants and purified to produce flours, concentrates, or isolates. In some cases, they may be further processed (e.g., hydrolysis, conjugation, or heating) to enhance their functionality.  
2. Product formulation: The plant proteins are combined with other ingredients (such as carbohydrates, lipids, salts, flavors, and colors) that will be able to create a plant-based meat analogue with the required appearance, texture, chewiness, flavor, and cookability of a real meat product. In addition, nutrients may be added to match or exceed the nutrient profile of real meat.  
3. Processing: The mixture of ingredients undergoes a series of processing operations that promotes the formation of meat-like structures and properties. These operations may include mixing, extrusion, shearing, moulding, and trimming.  
4. Storage: The product, packaging materials, and environmental conditions must be designed so that the plant-based meat alternative remains safe and of high quality during storage, transportation, and distribution. This requires consideration and control of microbiological, chemical, and physical deterioration mechanisms.

The overall aim of this process is to create a final product that accurately mimics the desirable quality attributes of real meat, and is safe and nutritious. Extrusion technologies are presently the most common method of creating plant-based meat analogues, but other technologies are being developed, including shear cells, mycelium cultivation, 3D printing, and recombinant proteins.⁸

The different ingredients and processes used to create plant-based meat compared to real meat products leads to different safety and nutritional concerns, which are considered in the following sections.  

“It is important to select proteins that have a low allergenicity when formulating plant-based foods and to carefully process and label them.”

Protein Isolation and Functionalization

Proteins play a critical role in the technological, physicochemical, and sensory attributes of plant-based food products. For instance, they impact the structure, texture, appearance, chewiness, water-retention, and nutritional attributes of plant-based meat alternatives.⁹ The selection of an appropriate protein is important because plant proteins have versatile functional attributes, such as their ability to thicken, gel, emulsify, structure, foam, and hold fluids.¹⁰

Proteins are usually extracted from plant materials (such as soybeans, peas, or corn) to form flours, concentrates, or isolates. Extraction and purification can be carried out using a wide variety of methods, including conventional methods that employ harsh chemicals (acids, bases, and/or organic solvents), green extraction methods (single or mixed enzymes), and advanced physical extraction methods (ultrasound-, pulse electric field-, microwave- and high pressure-assisted extraction).¹¹ Notably, many of the methods used to extract proteins were not originally designed to optimize their functionality. Instead, they were optimized to extract the oil or starch from plant materials. As a result, protein functionality may be compromised because they are denatured or aggregated.

Allergens

Several food safety and nutrition quality issues can be linked with this stage of plant-based meat creation. For instance, many plant proteins are known allergens, including soy, wheat, pea, and lupin proteins, which may cause health issues in some consumers.¹² Some consumers are also concerned that certain kinds of plant proteins (especially those from soy) are obtained from genetically modified sources.¹³ However, the health and environmental risks associated with consuming genetically modified foods is still contentious.¹⁴ The use of organic solvents (such as hexane) during protein extraction can also cause environmental and health concerns, particularly if relatively high residual amounts remain in the final product.¹⁵ However, no specific information is available on the amounts of hexane used in the production of soy and pea protein isolates for plant-based alternatives, or how much remains in the final product.¹⁶

Potentially, increased consumption of products containing high levels of soy, pea, wheat, and other plant proteins could provoke allergic reactions in people who have not previously experienced issues with these foods. For example, some people with peanut allergies reported post-consumption allergic symptoms, which suggested that the similarity of the pea and peanut proteins triggered a cross-reaction.¹⁷ Wheat proteins are also a common allergen that may cause a life-threatening anaphylaxis reaction or other, less serious (but still undesirable) symptoms. These proteins are used as a binder in several plant-based meat products. Consumers with wheat allergies and celiac disease may also be allergic to gluten, which is a protein found in grains such as wheat, barley, and rye. Consequently, it is important to select proteins that have a low allergenicity when formulating plant-based foods and to carefully process and label them.

Natural Toxins

Natural toxins may be present in several of the ingredients used to formulate plant-based foods. These substances are usually metabolites produced by the plants to defend themselves against various threats such as bacteria, fungi, insects, and predators. Common examples of natural toxins in plants include lectins in green, red, and white kidney beans; cyanogenic glycosides in bitter apricot seed, bamboo shoots, cassava, and flaxseeds; glycoalkaloids in potatoes; 4'-methoxypyridoxine in ginkgo seeds; colchicine in fresh lily flowers; and muscarine in some wild mushrooms.¹⁸ Consequently, it is important that all plant-derived ingredients used to formulate a product are carefully selected and processed to avoid, remove, or deactivate these toxins.

Some researchers have expressed concerns about using carrageenan, which is extracted from seaweed, as a food ingredient. Carrageenan is a polysaccharide sometimes used in meat analogues as a thickening, gelling, or stabilizing ingredient. It has been suggested that carrageenan may promote gastrointestinal inflammation, alterations in intestinal microflora, irritable bowel syndrome, and colon cancer.¹⁹ Additionally, it can accumulate high levels of heavy metals if obtained from contaminated seawater, which could pose a health risk.^20,21 Nevertheless, there is little scientific consensus about the potential health risks of carrageenan at present.

Plant proteins also have different amino acid profiles than meat proteins. Many of them lack one or more essential amino acids that are required for human health but cannot be synthesized within the human body (such as methionine, lysine, and tryptophan).²² In principle, this could lead to health issues, but most vegan or vegetarian diets contain sufficiently high levels of a diverse range of protein sources that this is not an issue.

Product Formulations

In this phase, plant proteins are mixed with various other functional ingredients that are required to obtain the desired look, feel, and taste of the final product, including flavorings, colorings, emulsifiers, texture modifiers, gelling agents, and binding agents.²³ Some consumers have expressed concerns about the large number of additives included in some plant-based meat alternatives and consider them to be ultra-processed foods.²⁴ Several of the ingredients used in these highly formulated food products have raised nutritional concerns, including saturated fats, highly refined flours, and salts.²³  

Some researchers have also expressed concern about the inclusion of leghemoglobin, an iron-containing hemeprotein that can be obtained from soybean root nodules, in some plant-based foods. This protein is used to provide the desirable red color and meaty flavors normally associated with the hemoglobin in real meat.²⁵ Due to the difficulties in obtaining sufficiently large quantities from soybeans, this protein is usually produced by genetically engineered yeast cultures. Some researchers have linked higher intake of heme iron with increased body iron stores and increased risk of developing type 2 diabetes.²⁶ Nevertheless, there is little scientific evidence that the levels of these proteins used in plant-based foods causes health issues.

Concerns have also been expressed about the potential health risks associated with consuming plant-based meat products containing a combination of many different additives, including flavorings, colorings, binding agents, preservatives, and sweeteners, but again there is little evidence that this is a health concern.

Some plant-based meat alternatives are higher in saturated fat than conventional meat products, as well as minimally processed plant-based protein sources, such as beans and lentils.^27,28 Consequently, some concern exists about the potential health effects of increasing the level of saturated fats in the diet. Nevertheless, plant-based meat products can be reformulated to contain less saturated fats,¹⁰ and there is currently much debate among nutrition scientists about the adverse nutritional effects of saturated fats.²⁹

Some plant-based meats contain relatively high amounts of salts, which may also be a health concern because elevated salt levels in the diet can increase the risk of high blood pressure, cardiovascular disease, osteoporosis, kidney disease, and stomach cancer.³⁰ Overall, plant-based meat alternatives appear to have a more beneficial nutritional profile than animal meats, but this could be further improved by a reduction in their salt content.³¹ In general, however, this is likely to depend on the particular type of plant-based food being considered.

Meatless products can be formulated using liquid smoke flavorings, which have been reported to be carcinogenic if consumed regularly at sufficiently high levels.³¹ Plant-based meat alternatives have also been reported to lack certain amino acids and their derivatives—such as creatine, taurine, and anserine—which are believed to be important for human health as they can affect brain and muscle function.³²  

Some researchers believe that the industrial processing of plant-derived ingredients to form meat alternatives is not necessarily undesirable because it can promote positive changes in the human gut microbiome depending on the nutrient profiles of each of its individual ingredients, and that quality assessments should be performed on an individual product basis.³³

Processing Concerns

Like meat products, it is also important to adequately thermally process plant-based meat analogues prior to consumption to ensure that they are microbiologically safe. This processing can be carried out in the factory, restaurant, or home. For consumers, following the manufacturer's food preparation instructions on food labels is important because legumes, grains, and vegetables can become contaminated with pathogenic bacteria. Following good food safety practices ensures that these foods will not cause harm to the consumer when prepared and/or eaten according to their intended use.

Most plant-based meat alternatives are processed using extrusion, a high-temperature and high-pressure method that creates the desired form and texture while simultaneously reducing the microbial load. The time and temperature elements are considered critical control points. Additional investigation of non-protein ingredients and innovation in production technologies for alternative protein products, improvements toward the overall appearance and flavor, biological and chemical safety control, and the selection of protein sources are necessary for answering all food safety and quality issues and to continue the expansion of protein offerings on the market.

“Plant-based meat alternatives are generally not associated with pathogenic disease concerns, but these products can still cause foodborne illness.”

Microbial Food Safety Risk of Plant-Based Foods

The influence of microbial contamination on food safety and the shelf life of plant-based meat products is another issue of concern. Plant-based meat alternatives are generally not associated with pathogenic disease concerns, but these products can still cause foodborne illness. They can become contaminated with pathogens via contact with contaminated sources of animal manure, water, or other foods.³⁴ Plant-based meat alternatives contain near-neutral pH and high protein and moisture content, making them susceptible to microbial growth and spoilage.³⁵

Research has highlighted the need for more research on the microbial contamination and safety of plant-based foods.^36,37 Some of these studies use metagenetics to assess changes in the numbers and types of microorganisms during the storage of plant-based products.³⁸ Some studies have reported the high prevalence of specific microbes at the end of the shelf-life period, such as Latilactobacillus sakei, Enterococcus faecium,³⁹ and Enterobacteriaceae and yeasts proliferation as a post-process contamination of heat-treated plant-based meat alternatives stored at ambient temperature.⁴⁰ Knowledge of the types of microorganisms present is important for ensuring the safety of plant-based meat alternatives.  

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