Strategies to Improve the Quality of Foods

Strategies to Improve the Quality of Foods, Volume One in the Developments in Food Quality and Safety series explores salt, sugar and fat reduction, while also discussing natural alternatives and nitrate and nitrate salts. Enrichment of foods with prebiotics, probiotics and pos-biotics in food development is also explored. This series is the most up-to-date resource covering trend topics such as Advances in the analysis of toxic compounds and control of food poisoning; Food fraud, traceability and authenticity; Revalorization of agrifood industry; Natural antimicrobial compounds and application to improve the preservation of food; Non-thermal processing technologies in the food industry, and more.

Edited by Dr. José Manuel Lorenzo and authored by a team of global experts in the fields of Food Quality and Safety, this series provides comprehensive knowledge to food industry personals and scientists.

• Provides latest information regarding the production of food products with modified composition (reformulation)
• Brings modern strategies adopted by the food industry to obtain healthier foods without giving up the highest
quality standards.
• Presents salt, sugar, and fat reduction strategies in food products

• Language: English
• Publisher: Academic Press
• Release date: Oct 25, 2023
• ISBN: 9780443153471

Book preview

Chapter 1

Sustainability and functional foods: challenges and opportunities

Rubén Agregán¹, Paulo Cezar Bastianello Campagnol², Rubén Domínguez¹, Noemí Echegaray¹, Julián Andrés Gómez Salazar³ and Jose Angel Perez-Alvarez⁴,    ¹Centro Tecnológico de la Carne de Galicia, Ourense, Spain,    ²Department of Technology and Food Science, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul, Brazil,    ³Food Department, Life Sciences Division, University of Guanajuato, Irapuato, Guanajuato, Mexico,    ⁴IPOA Research Group, Agro-food and Agro-environmental Research and Innovation Center, Miguel Hernández University (CIAGRO-UMH), Orihuela, Spain

Abstract

The overexploitation of ecosystems due to the incessant increase in food demand is depleting natural resources. At this point, the market segment for functional foods is aligned with the new sustainable practices that attempt to reverse this situation through research and development of alternative production strategies. These include exploring the still little-known marine ecosystem as a source of novel nutraceuticals, the use of agrifood waste generated in food processing, and the promotion of energy efficient crops capable of resisting environmental stress conditions. In addition, the classic production protocols, together with the associated technologies, are being replaced by more efficient and environmentally friendly ones. Therefore the future of functional foods will revolve around development protocols with a lower environmental impact and the use of available resources in order to reduce the carbon footprint.

Keywords

Functional food; bioactive compounds; marine ecosystem; waste revaluation; sustainable crops; green extraction technologies

1.1 Introduction

It has been well known for a long time that good nutrition, based on a sufficient and balanced diet, combined with regular physical exercise, promotes a good state of health. On the contrary, an inadequate intake of nutrients and a sedentary lifestyle have been related to a predisposition to the development of cardiovascular disease (CVD), reduced immunity, and poor physical and mental growth. Unfortunately, the hectic pace of modern man’s life has promoted unhealthy habits such as those described above. Nevertheless, a recently adopted attitude toward caring for our bodies and the environment is gradually permeating society and positively modifying eating habits.

The interest of consumers for healthier and more natural foods has led the industry to reformulate a wide range of products. Specifically, the development of dietary supplements, such as cod liver oil, iron tablets, or multivitamins, has helped to counteract certain deficiencies of our diet in the pass, improve health, or reduce the risk of contracting specific diseases (Webb, 2011). However, over time, the consumer has preferred a more holistic solution to this issue, demanding the integration of the drug or active agent in the food, as a whole, which has led to the emergence of a new market segment of special products called functional foods, which has not stopped growing year after year (Birch & Bonwick, 2019).

This term came to light in the 1980s, more specifically in 1984, in Japan. The government of this country defined a new category for these products, Food for Specific Health Uses (FOSHU), as food containing an ingredient with functions for health and officially approved to claim their physiological effects on the human body. The same path was followed by the United States one decade later, but without providing a formal definition of what is considered a functional food. The European Union also joined this new market trend, introducing the regulation on nutritional and health claims (Reg. (EU) n. 1924/2006). In the same way, neither on this occasion a definition on what the term functional food means was included (Alongi & Anese, 2021). There is no global consensus on what a functional food should be, since despite being regulated in many countries, they lack of legal recognition, resulting in no statutory definition (Ye et al., 2018). Nevertheless, experts in the field generally agree that these foods credited with health benefits beyond those provided by the basic nutritional compounds (Baker et al., 2022).

At present and due to the rate of production to supply food to a world population in continuous growth, the pressure on natural resources has made it necessary to review and modify the processes and practices carried out in the production chain. At this point, obtaining functional foods must also be analyzed in order to control its possible impact on the environment (Sibbel, 2007). In this vain, different strategies are being explored to attempt to reduce the carbon footprint in the functional food production chain.

The bioactive compounds are primarily recovered from terrestrial plant sources while other potential sources remain underexploited. Thus, for example, the extraordinary biodiversity of the marine ecosystem has recently been found to offer chemical compounds with great biological capabilities such as phorotanins, unique polyphenols from brown algae, which have been reported to possess high antioxidant activity (Rubén Agregán et al., 2018). Microalgae are also organisms that have a significant content of high-value molecules, such as astaxanthin, β-carotene, phycocyanin, and eicosapentaenoic (EPA) (C20:5n−3) and docosoexaenoic (DHA) (C22:6n−3) acids (Vigani et al., 2015). Similarly, the tissues of marine animals can provide interesting bioactive compounds. Shrimp and crab shells are mainly used to obtain chitin and derivatives (Kim & Pallela, 2012), natural biopolymers with reported antimicrobial, immunological, and antioxidant activities (Hamed et al., 2016). Mollusks have also been found to provide compounds with interesting biological properties such as 2H-chromene-3-methyl carboxylate, recovered from the marine gastropod Babylonia spirata and with proven antioxidant and anti-inflammatory activities (Chakraborty & Salas, 2020). In general, therapeutic effects against chronic diseases, such as cancer, CVD, and obesity, among others, have been linked to compounds found in fish as varied as sardines, salmon, mackerel, tuna, or shark (Awuchi et al., 2022).

On the other hand, the development of functional foods should also be based on the recovery of agricultural residues for the extraction of biologically active substances. Agricultural by-products are currently considered as a source of ingredients with high-added value for the food industry, including polyphenols, enzymes, organic acids, and fibers (Lai et al., 2017).

The use of sustainable crops with high amounts of bioactive compounds is another scenario that might boost the growth of the functional food sector, while limiting the impact of land and water overuse on the environment. There are numerous examples of underexploited plants rich in compounds of this nature, including minor cereals, such as sorghum, millet, and teff; pseudocereals, such as quinoa, amaranth, and buckwheat (Agregán et al., 2022a,b); and legumes, such as the Cajanus cajan L. and the Lablab purpureus (L.) Sweet or those of the genera Vigna and Lathyrus (Conti et al., 2021). Therefore, these crops may offer a viable solution to the problem of overexploitation of resources, guaranteeing the production of safe foods with good nutritional quality and rich in biologically active compounds.

On the other hand, the establishment of processing and manufacturing protocols capable of minimizing the environmental impact of industrial activities aimed at the production of functional foods will help the sustainability of the sector. At this point, the use of green extraction technologies, such as microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), high-pressure assisted extraction (HPAE), pulsed electric fields (PEFs), or supercritical fluid extraction (SFE), can be instrumental in achieving this target (Putnik et al., 2018).

Throughout the following paragraphs, different alternatives are discussed to satisfy the market requirements of functional foods while meeting the need to reduce the environmental impact generated during the production chain.

1.2 Management of environmental impact in obtaining functional foods

1.2.1 Use of underexploited natural resources: marine ecosystem

The current exponential growth of the Earth’s population, which has doubled since the last half century, has ended up exhausting the regeneration capacity of the planet’s resources (Valoppi et al., 2021). In 2050, world demography is expected to increase to almost 10 billion inhabitants, exceeding this figure by 2100 (United Nations, 2015). Therefore, the natural resources exploited by human being are no longer enough to fulfil the purpose of covering the minimum nutritional needs of the entire world population. For this reason, food sources beyond those from the terrestrial ecosystem have been explored as a strategy to fight against the scarcity of food resources. The marine environment is the clearest example of this, since most of the planet is occupied by oceans and seas, covering approximately 70% of the surface, which is home to a wide variety of species rich in chemical compounds (Choudhary et al., 2021). More than 20,000 have already been isolated, although only a small proportion have been studied in depth, comprising proteins and peptides, polysaccharides, omega-3 polyunsaturated fatty acids (PUFAs), polyphenolic compounds, and pigments, among others (Šimat et al., 2020). Health beneficial properties of these unique chemical compounds have been reported (Fig. 1.1), demonstrating good potential to be used in the formulation of functional foods (Biris-Dorhoi et al., 2020). Table 1.1 shows some examples of the marine bioactive compound incorporation in varied foods.

Figure 1.1 Potential benefits of incorporation nutraceuticals from the marine environment into food. PUFA, polyunsaturated fatty acid.

Table 1.1

The spread of macroalgae by the seas and oceans and the wide variety of compounds with biological activity found in their tissues offer a good opportunity for their use as nutraceuticals in pharmaceutical and food applications. Among the compounds present in seaweeds, polyphenols stand out, more specifically those known as phlorotannins. These molecules have been linked to multiple health benefits, including antihypertensive, anti-inflammatory, and antidiabetic properties (Agregán et al., 2019), which has led to a growing interest in their extraction and characterization to be used as ingredients in the pharmaceutical and food industries. Nevertheless, there are still few metabolomics studies and clinical trials confirming these health benefits (Erpel et al., 2020). Cassani et al. (2020) analyzed the suitability of phlorotannins as biologically active compounds and reported possible problems related to their intestinal absorption, since the proportion that reaches the bloodstream seems to be low. In this sense, it was observed that these polyphenols are fermented by the intestinal microbiota, which undoubtedly contributes to this theoretical malabsorption. On the other hand, the absence of commercial standards for phlorotannins makes it difficult to correctly assess their bioavailability. Moreover, tannins are classified as astringent and bitter compounds, so that effective doses of phlorotannins in food products might negatively affect their acceptance (Cassani et al., 2020).

Macroalgal pigments are another class of chemical compounds of great interest due to their potential biological properties (e.g., antioxidant, antimicrobial, antidiabetic, anti-inflammatory, anticancer) and can be classified into three main categories: carotenoids, chlorophylls, and phycobiliproteins (Šimat et al., 2020). Carotenoids have been traditionally used in human and animal feed due to their colorant properties, especially β-carotene, which is frequently added to food products, including beverages, such as fruit juices and soft drinks (Pangestuti & Siahaan, 2018). This strong orange-colored pigment is a precursor and inactive form of vitamin A (Hamidi et al., 2020) and was recovered from a wide variety of seaweeds, including genera of green algae (Chlorophyta), such as Bryopsis, Ulva, and Caulerpa; red algae (Rhodophyta), such as Gracilaria, Grateloupia, and Eucheuma; and brown algae (Phaeophyceae), such as Bifurcaria, Laminaria, and Sargassum (Balasubramaniam et al., 2020; Bhat et al., 2021; Garcia-Perez et al., 2022). Similarly, fucoxanthin is another ubiquitous carotenoid in the plantar marine kingdom, representative of brown algae and with outstanding antioxidant capacities due to the allenic bond of its molecular structure, a characteristic element of carotenoid compounds and responsible for their high antioxidant potential (Pangestuti & Siahaan, 2018). Beneficial effects on human health have been given to this carotenoid, including anti-inflammatory, anticancer, anti-obesity, antidiabetic, and hepatoprotective effects. Nevertheless, clinical trials are still needed to guarantee the safety of this compound in humans (Bae et al., 2020).

Chlorophylls are another group of pigments present in seaweeds that are characterized by their green color and the varied number of biologically positive activities for the proper functioning of the human organism. These compounds are not strange in human food either, since they can also be found in different types of terrestrial vegetables commonly used in the diet. Their incorporation as functional ingredients could positively influence in the elimination of free radicals (Sharma et al., 2021), as well as cancer prevention by capturing mutagens, modeling xenobiotic metabolism, and inducing apoptosis (Queiroz Zepka et al., 2019).

Phycobiliproteins are algae pigments also used as natural colorants in the food industry, providing color in chewing gums and dairy products (Kraan, 2013). They are highly fluorescent compounds synthetized by cyanobacteria and red algae that have an important role in medical applications, such as the diagnosis and treatment of diseases (Li et al., 2019). In addition, as in the case of carotenoids and chlorophylls, the intake of phycobiliproteins could positively intervene in important physiological processes. Thus, for example, protein hydrolysates from the cyanobacteria Arhrospira platensis were found to inhibit angiotensin-converting enzyme (ACE) activity, indicating the presence of potential antihypertensive peptides (Liu et al., 2022). Similarly, Kim et al. (2018) obtained phycobiliprotein-derived peptides of the red alga Pyropia yezoensis, capable of inhibiting the generation of reactive oxygen species (ROS), suggesting a potential antiaging property. Other reported possible benefits of the action of phycobiliproteins include the mitigation of pathologies such as renal dysfunction (Rojas-Franco et al., 2018), preeclampsia (Castro-García et al., 2018), or cancer (Viana Carlos et al., 2021), and the regulation of immune responses such as those produced in allergic asthma (Chang et al., 2011).

Seaweed polysaccharides have been widely used in food applications due to their biochemical properties (e.g., stabilizer, emulsifier, gelling agent). In fact, most of the marine algae harvested today are intended for the extraction of polysaccharides to be used as hydrocolloids, with agar, agroses, alginate, and carrageenan being the most frequently recovered (Pandey et al., 2020). In addition to this more purely technological attribute, bioactive properties have also been associated with these components of seaweeds. The so-called sulfated polysaccharides, absent in terrestrial plants, can represent more than 50% of the algae in dry weight (DW) (7%–75%) and they are recognized for the high number of beneficial properties. Some of these polysaccharides, such as alginate, laminarin, fucans, and fucoidans, are found in green algae, while others, such as carrageenan and agar, are found in red algae, and all of them were reported to possess antioxidant, antimicrobial, antitumor, anticoagulant, antihyperlipidemic, and anti-inflammatory activities (Otero et al., 2021).

Microalgae are another interesting source of bioactive compounds recently explored for the development of functional foods. These microscopic photosynthetic organisms have evolved over time to thrive in the planet’s harshest environments by producing a remarkable array of protective and nourishing compounds, including carotenoids, flavonoids, and fatty acids, such as EPA and DHA, which play an important role in human metabolism as previously mentioned (Matos et al., 2017). As in the case of macroalgae, they have a very high potential to serve as nutraceuticals in food applications. Thus, for instance, a wide range of biologically active compounds can be found in the biomass of microalgae in the form of proteins, PUFAs, pigments, vitamins, and minerals. Even extracellular compounds such as oligosaccharides have been reported to exhibit beneficial health effects. In this regard, anticancer, anti-inflammatory, antioxidant, anti-obesity, and antimicrobial capacities have been attributed to these microalgae compounds, suggesting their usability as ingredients in the formulation of functional foods and increasing their market value in the food industry (Camacho et al., 2019).

It is important to note that under normal conditions, microalgae will not produce biologically valuable metabolites or the yield will be very low. Thus, the biosynthesis of these compounds has to be induced by their exposure to stress conditions, such as high salinity, strong light, nitrogen deprivation, high temperature, short-term UV radiation, or a mixture of these different conditions (Hamidi et al., 2020). This means that for adequate production these microorganisms need to be cultivated in a controlled manner.

The animals that inhabit the singular marine ecosystem can also be considered as a potential source of biocompounds with possible and interesting food applications. A good example of this is chitin, a polymer naturally found in marine invertebrates with well-documented biological properties. On the other hand, chitosan, also associated with outstanding biological activities, is obtained by deacetylation of the chitin molecule (Varlamov et al., 2020). The chemical structures of both compounds consist mainly of N-acetyl-D-glucosamine and a small amount of D-glucosamine (Šimat et al., 2020). Chitin is usually and exclusively found in the extracellular space of the shell of mollusks, although it can also be found in the cell wall of fungi or in the cuticle of arthropods, acting as a protective and supporting component of these organisms (Moussian, 2019).

The reuse of these structures from waste materials in the fishing industry is not frequent, but the demand for alternative materials in fields such as the development of new products is attracting the attention of researchers. Thus the massive amount of crustacean shells generated might be used for the production of chitin and chitosan. Obtaining the latter is much cheaper than other biopolymers since many energy efficient methods can be used (Santos et al., 2020). Chitosan has been extensively studied as a food preservative. Derivatives of this polymer obtained by Maillard reaction have been positively tested in order to inhibit microbial spoilage, reduce lipid oxidation, and extend the shelf life and quality of fresh food products (Hafsa et al., 2021). Technological applications as an emulsifier and flocculant have also been successfully studied. In addition of its potential use in food formulation, chitosan may also be used as a carrier for encapsulating and controlled delivery of probiotics in functional foods (Kabanov & Novinyuk, 2020).

Fish oil is another compound of significant nutritional relevance that has recently been highlighted due to the multiple beneficial effects associated with its consumption, contributing to a better state of health by treating certain disorders and preventing the progression of chronic diseases (Šimat et al., 2020). Especially relevant are the omega-3 fatty acids, present in high amounts in fatty fish, whose potential functional properties have been widely assessed (Agregán et al., 2022a,b). Protection against diseases and conditions, such as arterial hypertension, myocardial infarction, or cerebrovascular disease, is linked to the ability of EPA and DHA, important and representative omega-3 fatty acids of fish fat, to alter physiological pathways and cardiovascular risk factors, such as blood pressure, cardiac function, arterial compliance, vascular reactivity, and lipids. Other beneficial properties of these compounds include antiplatelet, anti-inflammatory, proresolving, and antioxidant activities (Mori, 2017).

1.2.2 Use of waste from agroindustrial activities as a source of biocompounds

As already mentioned in the previous section, the incessant growth of the world population has forced the scientific community to search for production alternatives able to satisfy the minimum demand for food. For this reason, promoting the sustainability of production systems is an essential task in order to alleviate the pressure on natural resources and thus achieve this target. The functional food sector, which has experienced rapid growth in recent years, should be aware of this problem and adopt strategies that allow a sustainable development of these products. To comply with this requirement, the food industry has begun to use organic materials discarded throughout the production chain in order to recover valuable substances. This strategy will reduce the environmental impact associated with the loss of resources and companies might mitigate the economic losses derived from the management of this waste, and at the same time generate additional income by obtaining a product with added value, such as those depicted in Table 1.2.

Table 1.2

Agricultural residues are generally made up of peels, skins, leaves, seeds, pulps, rinds, other parts of food species, and the entire product when it does not meet specific quality criteria (Fernández-Ochoa et al., 2021). All these elements derived from fruits and vegetables contain significant amounts of health-promoting compounds, such as carotenoids, polyphenols, fibers, vitamins, and oils, among others, which can be incorporated into food (Fig. 1.2). Wastes from winemaking, especially red grape skins and also seeds, are organic materials with an incalculable wealth of biologically active compounds, such as phenolic acids and anthocyanins, as well as fiber. For this reason, several studies have assessed their use in the reformulation of food products, such as tomato and beetroot purees, cheese, and bakery products, all of them acquiring a new and improved bioactive profile (Gaceu et al., 2020; Gaglio et al., 2021; Lavelli et al., 2014; Pagliarini et al., 2022). Plant residues from other fruits or vegetables have also been considered as potential ingredients or raw materials for the extraction of useful components in the preparation of new food products. Therefore, many works on the addition of fruit peels or some of their bioactive constituents in products such as cookies (passion fruit, pomegranate, banana, and apple) (Garcia et al., 2020; Kaderides et al., 2019; Rahman et al., 2020), pasta (mango) (Jalgaonkar et al., 2018), yogurt (pomegranate) (Ahmed et al., 2022), and crackers (prickly pear) (Elhassaneen, 2016) have been recently published. There are also studies on the incorporation of other discarded parts of vegetables, such as jambolan and pumpking pulp, which were added to pasta and ice cream, respectively (Hassan & Barakat, 2018; Panghal et al., 2019), or leaves as those of moringa, which were used in pasta, and those of cabbage in sponge cakes (Jalgaonkar et al., 2018; Prokopov et al., 2015).

Figure 1.2 Some of the most important bioactive compounds from agro-industrial by-products. ¹Galactooligosaccharides; PUFA, polyunsaturated fatty acid; EPA, eicosapentaenoic acid; DHA, docosoexaenoic acid.

Seeds of certain crops, which are used as a source of oil, may serve as raw material for the preparation of food products. The remaining cake after the recovery of the oil from the seed is rich in polyphenols and fatty acids of high nutritional value. In addition, the protein content is also high, with values ranging between 35% and 60% DW (Moure et al., 2006). This fact is very important considering the need for cheap and high-quality sources of this macroelement. Based on this composition, oilseed cakes serve as substrates for production of bioactive molecules for the improvement of food products. Borchani et al. (2021) highlighted the ability to scavenge free radicals of the glutelin and albumin proteins extracted from a prickly pear seed cake. Likewise, these authors reported the possibility that amino acids from these two proteins may function as electron donors, reacting with free radicals to form more stable products and thus terminate the radical chain reaction. Similarly, Xu et al., (2020) recovered a polysaccharide with antioxidant activity from the seed cake of Tengjiao, a kind of prickly ash native to China. On the other hand, as previously commented, the unextracted fatty acids constitute an important part of these oil cakes. Regarding this, Petraru et al. (2021) found a remainder of approximately 15% oil in the sunflower seed cake after extraction, of which more than 90% were unsaturated, with oleic acid and linoleic acid being the major fatty acids. A favorable fatty acid profile was also found in a partially deoiled chia flour, increasing the ω−3/ω−6 ratio when added to wheat pasta, as well as the polyphenol content (Aranibar et al., 2018). Therefore these organic residues from the extraction of seed oil could serve for the improved redesign of food products.

Another plant residue with a potential nutritional and functional value for the development of new food products is cereal bran. This element is arranged in the form of successive layers, also called pericarp, and covers the outside of the cereal grain, protecting the endosperm and germ. During the processing of cereals to obtain flour, it is usually discarded and left for animal feed. Bran is an important source of dietary fiber that includes such health-promoting compounds such as polysaccharides, oligosaccharides, lignins, proteins, fatty acids, and other minor health-promoting substances (e.g., vitamins, minerals, tocopherols, tocotrienols, sterols, polyphenols) (Carpentieri et al., 2022; Luithui et al., 2019). Nevertheless, it has been reported to possess anti-nutritional effects due to the presence of phytic acid in significant amounts, a natural compound responsible for the bind of minerals, proteins, and starch, modifying their solubility, functionality, and bioavailability (Levent et al., 2020). Therefore, despite the positive health properties of cereal bran, a prior pretreatment to eliminate phytic acid would be advisable. For example, soaking cereal grains activates the phytase enzyme that catalyzes the hydrolysis of phytic acid (R. Agregán et al., 2022a,b). Similarly, the endogenous activity of this enzyme can be increased by promoting grain germination (Hendek Ertop & Bektaş, 2018).

The addition of rice bran to a traditional fermented soup from Turkey made from cereals produced an increase in the content of minerals, protein, fat, and phenolic compounds, but also phytic acid. In addition, the resulting product turned out to be sensorially unpleasant (Aktaş & Akın, 2020). To avoid high phytic acid contents without the need to pretreat the grain, brans with a low content of this antinutritional factor can be used, such as that of bulgur, a product made from whole wheat grain. Saka et al. (2020) found that adding this type of bran to a cookie dough significantly improves the percentage of dietary fiber, only slightly increasing phytic acid levels. Therefore, this bran would be indicated as an alternative to other cereals for the development of functional foods.

The meat industry is another sector that also discards an important amount of organic materials with nutritional value throughout the production chain, such as bones, skin, blood, and viscera, estimating a production of more than 20 tons per year of these by-products only in Europe. Despite being an interesting source of protein, the market value of these residues is considered low, being used as fertilizers and animal feed. Otherwise, they are simply discarded, generating a negative impact on the environment (Cao et al., 2022).

Fortunately, there has been recently an interest in revaluing these by-products through the hydrolysis of their protein for the production of bioactive peptides. Collagen, which is the main protein component of bones, cartilage, and skin, has proven to be an important source of peptides with physiological properties, being widely used as a drug by exhibiting beneficial effects on bone metabolism when they are administered orally (Mora et al., 2014). Hong et al. (2019) investigated the antioxidant potential of this animal protein obtained from pig skin through the production of hydrolysates. The obtained protein fractions showed excellent antiaging properties, demonstrating potential for use as antioxidants in foods. Similarly, Bezerra et al. (2020) optimized an enzymatic method for the production of bioactive peptides from the combs and wattles discarded during the slaughter of chickens. Protein hydrolysates with a variety of bioactivities including antioxidant and Fe²+ chelating capacities were produced. It should be noted that peptides generated from collagen have proven to be biocompatible and safe due to their unique biological and structural characteristics (Fu et al., 2019).

Elastin and keratin are other important fibrous structural proteins that make up connective tissues, ligaments, skin, hair, and feathers of animals (Ferraro et al., 2016), from which bioactive peptides can also be obtained by hydrolysis. Taraszkiewicz et al. (2022) found that keratins from chicken feather and pig hair are a potential source of biopeptides, including dipeptidyl peptidase IV, angiotensin converting enzyme, and prolyl endopeptidase inhibitory.

Fishing activity also generates high amounts of discards that cause economic losses and considerable environmental impact. Therefore it is essential to manage a sustainable use of resources trying to take advantage of by-products, such as the head, eyes, fins, tail, skin, liver, or viscera, which account for approximately one-third of the fish (Jaiswal et al., 2014). Recent studies have shown the presence of value-added compounds, which has led to be considered as sustainable sources of bioactive molecules for the development of novel food products, among other applications, including pharmacology. These residues can be considered as sustainable sources of biocompounds for the development of functional foods, among other applications, according to the results reported by recent investigations that have evidenced the presence of value-added molecules in their matrices. Franco et al. (2020) obtained extracts with antioxidant capacity from gills, bones, and heads of sea bream and sea bass after applying PEFs. Wang et al. (2021) found a similar result when using the same emerging extraction technology on head, skin, and viscera of rainbow trout and sole.

In the same way as in meat and its by-products, hydrolysis plays a prominent role in obtaining bioactive protein fractions from fish waste materials. Nam et al. (2020) obtained hydrolysates from various catfish discards with high antioxidant activity and rich in essential amino acids. On the other hand, the lipid fraction recovered from hydrolysis showed a significant content of vitamin A, as well as unsaturated fatty acids, highlighting the presence of EPA and DHA. Linolenic acid (C18:3n−3) was the second most abundant fatty acid with 18.32 mg/g, only behind stearic acid (C18:0) (41.51 mg/g). Enzymatic strategies for protein hydrolysis can provide peptides with biological activities similar to those of meat, positioning themselves as potential ingredients to produce functional foods. When acid-soluble collagens derived from by-products, which included skin, heads, and skeletons of different fish species, such as sharks, mullet, guitarfish, weakfish, squid, and seabass, among others, were hydrolyzed, the peptides obtained exhibited both antioxidant and antimicrobial activities. Moreover, the existence of technological properties, such as the ability to form emulsions and foams, was also observed, demonstrating adequate solubility at neutral pH (Zamorano-Apodaca et al., 2020).

Fish species captured by fishing fleets and with low market value can also be used as raw material to obtain bioactive compounds, as has recently been shown with fish species from the Northwest of Spain and usually discarded for consumption. Thus hydrolysates obtained from the flesh and by-products of gurnard, Atlantic horse mackerel, blue whiting, and pouting, among others, have revealed antioxidant and ACE inhibitory activities (Henriques et al., 2021).

Milk whey from cheese making and casein-based products represents another noteworthy source of biocompounds, which, however, has gone unnoticed and underappreciated for years. The clean disposal of this liquid residue resulting from the coagulation of milk is a headache for the dairy industry due to the high amount produced, which can be around 9 kg per kilogram of processed product (Pastukh & Zhukova, 2021). Traditionally, whey has been used for animal feed, the manufacture of fertilizers, or as an additive in beverages (Sáenz-Hidalgo et al., 2021). On the other hand, its disposal as wastewater requires prior decontamination treatment due to the high chemical and biochemical oxygen demands, which could put the environment, aquatic life, and human health at risk by depleting oxygen levels dissolved in natural water sources (Pires et al., 2021).

Lactose and proteins are especially abundant nutrients in whey that have been found to exhibit a number of interesting functional features for diverse technological applications. Thus the galactooligosaccharides resulting from the hydrolysis of β-d-lactose by the lactase enzyme could serve as functional ingredients for the preparation of prebiotics. In relation to this, oxidation reactions resulting from the enzymatic treatment of lactose may produce a wide spectrum of metabolites such as lactobionic acid, a compound with declared antioxidant capacity. On the other hand, the isomerization reaction of α-lactose has been found to produce lactulose, a bifidogenic factor with prebiotic properties (Rocha & Guerra, 2020).

Similarly to lactose, biologically active metabolites can be obtained from whey proteins. Specific hydrolysis reactions are used to release and activate fragments of these molecules for further evaluation as potential bioactive ingredients in food and drug applications. Some of the beneficial attributes exerted by whey peptides include the reduction of cholesterol levels and blood pressure in the treatment of CVD and protective action on the gastrointestinal system by exhibiting antioxidant and antiulcerative properties. In addition, relaxing properties and positive effects on glucose control and appetite have also been reported (Mehra et al., 2021).

Small steps toward the effective incorporation of these hydrolysates into food matrices have recently been taken. Barrón-Ayala et al. (2020) reported the feasibility of incorporating peptides from whey with antihypertensive activity into pork frankfurters in order to develop a functional meat product. On the other hand, Gómez-Mascaraque et al. (2016) studied the microencapsulation of these biocompounds to preserve their bioavailability during chemically aggressive processes, such as human digestion or fermentation, with conflicting results.

1.2.3 Promote the use of sustainable crops to obtain bioactive compounds

In addition to the previously discussed strategies, which advocate discovering new pathways or natural sources of bioactive compounds, another different trend is focused on using the natural resources available to grow plants more efficiently by promoting undemanding species capable of providing an acceptable production yield. Until recently, the advances made in terms of productivity were oriented toward improving plant architecture and light capture, producing more energy-efficient varieties. Unfortunately, over the years, the yields of the main crops have plateaued and new technological solutions must be explored. At present, there is hardly any fertile farmland left to exploit. This situation forces the search for alternatives capable of improving productivity without increasing the use of soil nutrients and freshwater, thus relieving pressure on natural ecosystems (Simkin et al., 2019).

In this context, Food and Agriculture Organization has identified many underutilized plants, which can significantly contribute to improve nutrition and health, food security, and sustainable development (Pirzadah & Malik, 2020). Small millet can be included in this class of crops due to its low need for nutrients and its ability to adapt to different climatic conditions and locations. In addition, this minor cereal has been reported to possess excellent nutritional properties and possible health-promoting bioactive compounds. Carbohydrates, dietary fibers, fats, proteins, essential vitamins, minerals, essential amino acids, and antioxidant compounds can be abundantly found in the grain of small millet (Banerjee & Maitra, 2020). Other little-consumed cereals, such as sorghum or teff, are also a good source of macro- and micronutrients, as well as phytochemicals (Agregán et al., 2022a,b). Sorghum may thrive under changing weather conditions and water and nutritional stress (Hossain et al., 2022). Similarly, teff survives in harsh weather conditions, being also resistant to periods of drought and floods, as well as pest and diseases (Barretto et al., 2021). These characteristics make them sustainable crops, especially indicated for the development of functional foods.

Pseudocereals are another type of little-used crops that mimic cereals, although they do not belong to the grass family. Nevertheless, they provide high-quality nutrients and a wide range of bioactive compounds, including phenolic acids, flavonoids, and phytosterols (Agregán et al., 2022a,b). The grains of these plants can also yield bioactive peptides with possible applications in the treatment of diseases such as hypertension (Chirinos et al., 2020; Ontiveros et al., 2020), cancer (Taniya et al., 2020), and CVD (Fisayo Ajayi et al., 2021; Shi et al., 2019).

In general terms, the plant kingdom provides diverse and varied crops rich in bioactive compounds and genetically suitable for sustainable exploitation. Barracosa et al. (2019) pointed out the polyvalence and versatility of cardoon, a little-known crop but with special aptitude for the sustainable production of biocompounds. This herbaceous species from the Mediterranean basin is adapted to climate change and offers a high content of phytochemicals, such as oligofructose, inulin, caffeoylquinic acids, flavonoids, anthocyanins, sesquiterpene lactones, triterpenes, fatty acids, and aspartic proteases, with possible food and pharmaceutical