Currently, there is an uptick in adoption of plant-based diets, as correlated by the rising trends of vegetarianism, veganism and flexitarianism.9 A variety of reasons – health, environmental concerns, animal welfare issues and religious beliefs – are mentioned in connection with the adoption and practice of plant-based diets (Cramer et al., 2017; Sabaté and Soret, 2014; Willett et al., 2019).
A plant-based diet, generally, focuses on the primary consumption of foods derived from plants (fruits, vegetables, nuts, seeds, legumes and whole grains). But it can also include small amounts of foods of animal origin – dairy, eggs, meat and fish. Therefore, the term “plant-based diet” is quite broad in its connotation.
The growing trend in adopting plant-based diets is propelling advancements (Box 4) in the plant-based alternatives industry (McClements and Grossmann, 2021). While consumers are reducing their consumption of animal-based products due to various reasons, many still desire the specific flavour, texture, mouthfeel and feeling of satiety associated with various animal-derived products. This has led to the development of various plant-based alternatives that mimic the taste and consuming experience of animal-based products (McDermott, 2021). Plant-based dairy alternatives, referred to in this report as beverages,10 and meat alternatives are quite popular and widespread in various regions globally, with plant-based alternatives for eggs and seafood trailing only somewhat behind in development and market penetration. The global retail sales for plant-based foods (primarily those of plant-based meat alternatives and beverages) are expected to reach USD 162 billion by 2030, up from USD 29.4 billion in 2020 (Elkin, 2021).
Among the various factors that are driving the growth of the plant-based alternatives sector, environmental and nutritional aspects are two of the major reasons behind the trend. Some of the opportunities and challenges associated with the two factors are discussed below.
However, the comparison of environmental impacts between livestock and plant-based alternatives may not always be as straightforward as are often portrayed. For instance, life cycle analysis suggests that plant-based meat alternatives can have a lower environmental footprint when compared to feedlot-finished beef, but higher than beef raised in well-managed pastures (van Vliet, Kronberg and Provenza, 2020).
However, from a public health perspective there has been limited research on the nutritional aspects of plant-based alternatives. van Vliet et al. (2021) suggests caution while categorizing plant-based alternatives as equivalent to the corresponding animal-based products. From a metabolomics study, they concluded that the animal-based product (beef) and the plant-based alternative for meat are more likely to be complementary, rather than interchangeable, in terms of provided nutrients.
Certain plant-based beverages do not make suitable substitutes for animal-derived dairy due to limited nutrient diversity (Drewnowski, 2021; Ranga and Raghavan, 2018; Rizzo et al., 2016). This incongruity must be taken into account for vulnerable populations, for instance, the emerging trend of plant-based formula and nutrition products for infants and toddlers. In addition, essential minerals like iron, zinc, magnesium and calcium may be less bioavailable in some of the plant-based ingredients found in the alternatives (Antoine et al., 2021; Gibson, Heath and Szymlek-Gay, 2014). Food processing may also lead to the loss of certain nutrients and phytochemicals found in plant-based foods. These factors necessitate more research into the nutritional aspects of such food products.
Certain plant-based meat alternatives contain more salt than the meat products that they are formulated to replace (Curtain and Grafenauer, 2019; Sha and Xiong, 2020). High sodium content is considered to be nutritionally undesirable and may predispose individuals, over time, to greater risk for cardiovascular issues (WHO, 2020a).
An estimated 931 million tonnes of food, or 17 percent of total food available for consumption in 2019, was wasted at the retail, food service and household levels (UNEP, 2021). With a staggering 3 billion people unable to afford a healthy diet (FAO, IFAD, UNICEF, WFP and WHO, 2020), it is important to tackle the issue of food waste. Some companies, especially within the plant-food sector, are trying to reduce food waste by “upcycling” low-valued foods or food-processing by-products, that would otherwise not be used for human consumption, to new food products.
Foods that are considered for upcycling tend to be those that are surplus, both at an institutional level or at a household consumption level, do not meet the standards of grocery stores in terms of appearance and are by-products formed during production of other foods, among others. Some of these food items are usually destined for either the compost pile or used as animal feed (Zaraska, 2021). Instead, depending on the type of food waste collected for upcycling, they can get converted into different end-products – protein powders, vitamins, jams and jellies, bakery products and beverages (Holcomb and Bellmer, 2021; Kateman, 2021). Certain economically viable upcycled food products are already on the market – whey protein, from cheese production, is used in protein powders and health bars, and wheat middlings that are left over from milling are added to breakfast cereals to bulk up fiber and other nutritional content, among others.
Upcycling is an emerging area in the food industry. In order to develop appropriate guidelines and standards for this sector, it is important to understand the food safety implications that come with it
The protein sources typically used in plant-based alternatives range from legumes to nuts, seeds, cereals and tubers (Sha and Xiong, 2020). Another growing segment within the plant-based protein industry is mycoproteins, which are derived from filamentous fungi like Fusarium venenatum (Hashempour-Baltork et al., 2020; Ritala et al., 2017). The dietary fats in plant-based alternative products are usually derived from a variety of plant products (such as canola oils, cocoa butter, coconut oil and sunflower oil) often used in mixtures to achieve desired physico-chemical and nutritional parameters. In plant-based meat alternatives, the plant proteins are bound together by methylcellulose (used as thickener and emulsifier is many foods) (Sha and Xiong, 2020).
One of the major advantages of plant-based alternatives is the opportunity to use a larger variety of ingredients to adjust the composition of the product to meet the technological, nutritional, functional needs and consumer preferences alike. Therefore, in addition to bulk ingredients and additives used to impart colour, form and texture, a number of these products also tend to be fortified with vitamins and minerals to enhance nutritional content and in some cases to account for nutritional differences between the plant-based ingredients and the animal-derived products they are intended to replace.
Food safety implications for food derived from plants depend on the soil, the agricultural inputs used where the source plants are grown, how the plants are harvested, stored, transported, and processed to obtain the protein isolates, handling of products post-processing and at the retail level as well as implementation of appropriate food safety management practices.
Certain plant-based food products tend to have a higher diversity of ingredients in them than animal-based products, potentially providing a variety of sources from where hazards may arise. Therefore, food safety can be a varied challenge for plant-based alternatives with multiple entry points for different contaminants – biological and chemical. Some key food safety implications for plant-based alternatives are discussed below.
Contamination of plant-based food products with pathogens can occur through contact with sources like animal manure or contaminated water (Rubio, Xiang and Kaplan, 2020). These factors are however not unique to plant-based food products. The high-moisture content and neutral pH of plant-based meat alternatives can provide a suitable environment for the growth of foodborne pathogens (Wild et al., 2014). A study by Geeraerts, De Vuyst and Leroy (2020) found high bacterial counts of spoilage microorganisms, such as Lactobacillus sakei and Enterococcus faecium, in plant-based meat alternative products (but lower than what was found on uncooked animal-based meat products) bought commercially in Belgium. The addition of non-sterile food ingredients post extrusion (McHugh, 2019),11 unsanitary handling and cross contamination may introduce microbial contamination necessitating further treatments. In terms of storage, to prevent proliferation of microbial activity Wild et al. (2014) had suggested that the system for storage and handling of plant-based meat alternatives should be similar to that of raw meat. Research is needed to determine if heat-resistant, endospore-forming bacteria like Bacillus spp. and Clostridium spp. survive the extrusion process or any other methods used in processing plant-based alternatives.
Plant-based ingredients have different components and concentrations of macronutrients (carbohydrates, fats, proteins) than animal-based products, which leads to variation in the types and resulting levels of microbial contamination that can occur (Floris, 2021). Various proteins found in plant-based beverages show differences in solubility and reaction to heat (Floris, 2021; Nasrabadi, Doost and Mezzenga, 2021; Sethi, Tyagi and Anurag, 2016), creating additional hurdles with regards to options available to maintain adequate food safety standards. At temperatures traditionally used to destroy harmful pathogens and reduce microorganisms associated with spoilage in animal-based products, many plant proteins denature, which affects the taste, texture and nutritional value of plantbased alternatives. This necessitates an exploration of different processing techniques to achieve food safety, while keeping the taste and texture of plant-based products intact (Floris, 2021).
Mycotoxins: There are many known mycotoxins that can be present in food derived from plants (Bennett and Kilch, 2003). Mycotoxins present in the raw ingredients – cereals (oat, rice), nuts (almond, walnut), legumes (soy) – may get carried over to end products, like plant-based beverages. Miró-Abella et al. (2017) analysed several plant-based beverages (soy, oat and rice) for the presence of certain mycotoxins (deoxynivalenol, aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2, ochratoxin A, T-2 toxins and zearalenone). They found that all the plant-based beverages were susceptible to the mycotoxins considered, albeit at varying levels (quantification ranged between 0.1 µg L-1 to 19 µg L-1). In another study, Hamed et al. (2017) explored the presence of Fusarium toxins (fumonisin B1 and B2, HT-2 and T-2 toxins, zearalenone, deoxynivalenol and fusarenon-X) in oat, rice and soy used for plant-based beverages and found that oat-based beverages were most susceptible to contamination with deoxynivalenol (191 – 270 µg L-1). Oat-based beverages have also been found to be susceptible to contamination with enniatins and beauvericin by Arroyo-Manzanares et al. (2019) who studied the presence of certain emerging mycotoxins in some plant-based beverages (soy, rice and oat).
Antinutrients: Certain compounds naturally present in legumes – phytic acid, protease inhibitors, lectins, saponins, among others – may reduce bioavailability of key nutrients and interfere in mineral absorption when present in diet at moderate to high quantities (Joshi and Kumar, 2015; Petroski and Minich, 2020; Rousseau et al., 2019). Phytoestrogens,12 like isoflavones, lignans and coumestan found in various plant-based foods may affect the endocrine system (Thompson et al., 2006), potentially leading to adverse health implications. The most studied phytoestrogens are isoflavones (daidzein, genistein, glycitein) found mainly in soy (Divi, Chang and Doerge, 1997; Patisaul, 2017). There are several processing techniques that can be used to inactivate or reduce the levels of these antinutrient factors (Rousseau et al., 2019; Samtiya, Aluko and Dhewa, 2020).
Allergenic potential: One of the major protein components of plant-based alternatives is soy. While soy-based alternatives to dairy products may be preferred by those who are allergic to cow’s milk, research shows that soy proteins may trigger allergic reactions in cow’s milk allergic individuals (Sicherer, 2005). A study by Rozenfeld et al. (2002) suggested that this was due to cross-reactivity between caseins from cow’s milk and the B3 polypeptide from the 11S globulin of soy. Other components of plant-based alternatives that can cause severe allergic reactions are tree nuts, legumes (peanuts) and gluten-containing cereals.
Some other allergens are also gaining attention, such as buckwheat and sesame. While the former has become increasingly more common outside of Asia, where it is widely consumed, the latter is gaining international attention and is set to be the ninth major allergen that is required to be labelled on food packaging (Beach, 2021; FAO and WHO, 2021; Heffler et al., 2014). Though sesame is not considered as a significant protein source, efforts are underway to produce a high-protein content variety of the seed (Ferrer, 2021) making it important to monitor this emerging space. Celiac disease is a disorder that is characterized by an intolerance to gluten, a major protein found in some cereals (e.g. wheat, barley, rye) (Joshi and Kumar, 2015).
A major source of plant-based protein is legumes (green peas, soy, peanut, lupin, green beans and pulses such as chickpeas, lentils, kidney beans and other dried beans) and the allergenic potential of several legumes has been identified and characterized so far (Cabanillas, Jappe and Novak, 2017; Verma et al., 2013; Villa, Costa and Mafra, 2020). There is a high rate of cross-reactivity among different legumes with individuals allergic to one showing sensitivity to others, but not necessarily to all (Kakleas et al., 2020). The recent trend of adding plant-based sources, such as pea protein concentrates and pea protein isolates, into a variety of foods to add bulk and increase protein levels may induce allergic reactions in some upon consumption (Abrams and Gerstner, 2015; Fearn, 2021). Individuals who are allergic to peanuts may also be vulnerable to peas and vice versa (Morrison, 2020; Wensing et al., 2003). The Codex Alimentarius Commission includes a priority allergen list as part of its General Standards for the Labelling of Prepackaged foods that is based on predetermined criteria, including global prevalence (FAO and WHO, 2018; FAO and WHO, 2021). Countries are encouraged to consider the inclusion of other food allergens on regional priority lists based on individual (or country-specific) consumption patterns and data.
While limited literature is available on allergenic potential of mycoproteins, Jacobson and DePorter (2018) analysed self-reported allergic reactions to mycoproteins and found that some reactions occurred on an individual’s first exposure to a mycoprotein-based food product. Research by Hoff et al. (2003) suggests that individuals sensitized to mould aeroallergens (Fusarium culmorum allergen Fus c 1) through respiration can experience allergic reactions upon consumption of mycoprotein-based food products due to cross-reactivity with allergen protein P2 from Fusarium venenatum.
Chemical hazards arising from processing: Based on how compounds like heterocyclic aromatic amines, nitrosamines and polycyclic aromatic hydrocarbons are formed in meat products, He et al. (2020) proposed that during the manufacturing and processing of plant-based meat alternatives these compounds may also emerge. However, production of toxic compounds due to the high-temperature processing of plant-based meat alternatives have yet to be investigated; for instance, the potential for the occurrence of glycidyl fatty acid esters, 2-monochloropropanediol (2-MCPD) and 3-monochloropropanediol (3-MCPD), which are heat-induced contaminants in food (FAO and WHO, 2017; GAO et al., 2019). Possible occurrence of trans-fatty acids, that are formed during partial hydrogenation of vegetable oil, in certain plant-based alternatives will also need to be determined. Several countries already have legislation in place to ban industrially produced trans-fatty acids from their food products (WHO, 2020b).
Other chemical hazards: Agriculturally important plants can absorb and accumulate heavy metals from soil (Galai et al., 2021; Zhao and Wang, 2019), which can lead to contamination of the end products with such chemical hazards. In addition, concentrations of potentially toxic rare earth elements, like thallium and tellurium, are increasing in our environment due to their applications in agriculture and various industries. These elements have also been detected in several plant-based foods (legumes, cereals, vegetables, among others) necessitating the need for hazard evaluation and risk assessment (National Food Institute – Technical University of Denmark, Doulgeridou et al., 2020). Research is also needed to evaluate other chemical hazards, such as residues of pesticides and antimicrobial agents, that can be associated with plant-based ingredients (Lopez et al., 2020).
Food safety concerns from the addition of soy leghemoglobin to plant-based meat alternatives, which is added to enhance the product’s “meat”-like flavour (Sha and Xiong, 2020) are currently being explored. Correlations are being made between high intake of heme iron, which can be sourced from both plant and animal-based products, and an increase in body iron stores with a greater risk for type 2 diabetes mellitus (Bao et al., 2012).
While understanding that the ecological impacts of human diets as well as the broader socioeconomic implications are not as simplistic as most discussions around plant versus animal would seem to indicate, a brief on plant-based alternatives is presented to showcase the potential benefits and challenges, focusing on the various food safety issues.
The food safety considerations for plant-based alternatives to animal-derived products can be quite different from the ones necessary to produce animal-based products, and hence any transition will require a careful retooling for food safety management processes. Some companies are trying to incorporate predictive modelling approaches in early product design stages (Floris, 2021). This process involves carrying out initial microbial risk assessments in silico based on processing conditions, intrinsic properties of the product, and intended storage and consumption conditions (Floris, 2021). The presence of mycotoxins and other chemical hazards necessitates putting in place proper controls to reduce exposure to chemical contaminants through this new food source. As plant-based diets expand, more awareness about introducing allergens from foods not commonly consumed before is needed prior to entering our diets. While most plant-based alternatives contain ingredients that have been previously approved for human consumption, ambiguities around the nomenclature of plant-based alternatives can create obstacles in developing guidelines relevant for the labelling of plant-based foods (Sha and Xiong, 2020).
Apart from food safety, price-point and cultural appeal of plant-based alternatives are other challenges to consider. The cost of plant-based alternatives is expected to reduce as consumer demand increases (Specht, 2019). Currently, plant-based meat alternatives are tailored for a more Western-type diet (burgers, nuggets, sausages), with insufficient foray into more traditional foods in different regions, thereby limiting consumer base and acceptance.
There are some potential trends on the horizon in the plant-based alternatives space, for instance, hybrid milk (combination of animal dairy and plant-based beverages), mixture of animal-based products and plant-based ingredients (such as animal-based meat combined with mushrooms).
While all or some of these plant-based alternatives could potentially represent a significant opportunity to reduce environmental impact of food production, they can also represent a disruption in agrifood systems, which could have important public health, environmental, and regulatory implications. Progress in this area will therefore depend on taking an integrated multidisciplinary approach to consider and overcome the various challenges