Exploring the Nutritional Potential and Functionality of Hemp and Rapeseed Proteins: A Review on Unveiling Anti-nutritional Factors, Bioactive Compounds, and Functional Attributes

1. Introduction

The escalating demand for supplementary products, especially among the younger and middle-aged population, a surge in lactose intolerance and gluten sensitivity, a rise in the adoption of vegan or vegetarian diets, and an increasing demand for sustainable and environmentally friendly protein sources are drivers that move plant based protein products on a new level and make them clearly an important source of nutrients for the human diet. In the realm of food product development, conditioned by the exploration of alternative protein sources, the use of rapeseed and hemp proteins has gained significant traction, fueled by the increasing demand for sustainable and nutritious options, but also relatively cheap alternatives for human diet.

Among nowadays food trends and modern consumer requirement, hemp and rapeseed proteins stand out as promising contenders, offering a plenty of nutritional benefits and functional properties conducive to innovative food formulations [1]. Hemp and rapeseed proteins are renowned for their complete amino acid profiles [2], boasting a rich array of essential nutrients essential for the human diet, overall health and well-being. These plant-based proteins are not only abundant in protein content but also provide valuable dietary fiber, vitamins, minerals, and antioxidants, rendering them invaluable assets in promoting balanced diets and meeting daily nutritional requirements [3,4].

Of note, both hemp and rapeseed are oil seed crops, meaning they are grown in many parts of the world in order to produce biofuels, animal livestock and oil for the food use, although the amount of protein these sources provide among other oilseed crops should be taking into consideration as they can be successfully implemented into high protein products recipes, with an enhanced texture and flavor [5,6]. According to USDA data [7] (Figure 1), the most protein rich oil seed crop is soybean (36.4g protein/100g ), followed by hemp (31.6g protein/100g) and mustard (26 g protein/100 g). Rapeseed, however contains only 18,6 g protein/100g.

Beyond their nutritional prowess, hemp and rapeseed proteins harbor an array of bioactive compounds with potential health-promoting effects. These compounds, ranging from polyphenols to phytosterols, contribute to the holistic health benefits associated with consuming these plant-based protein sources [8,9].

However, despite their nutritional virtues, hemp and rapeseed proteins also contain anti-nutritional factors that may impede optimal nutrient absorption and utilization. Understanding the presence and impact of these anti-nutritional factors is crucial for mitigating their effects and maximizing the nutritional benefits of hemp and rapeseed proteins [10,11].

Moreover, the digestibility and protein quality of hemp and rapeseed proteins play pivotal roles in determining their suitability for various food applications (Figure 2). Assessing factors such as amino acid composition, protein solubility, and protein digestibility is essential for elucidating the functional attributes and potential limitations of these plant-based protein sources in food product development.

In light of these considerations, this review paper aims to provide a comprehensive analysis of hemp and rapeseed proteins as viable options for food product development. By examining their nutritional value, bioactive compounds, anti-nutritional factors, digestibility, and protein quality, this study seeks to uncover the potential of hemp and rapeseed proteins as versatile ingredients in the creation of innovative and nutritious food products. Through rigorous exploration and analysis, this research endeavors to contribute valuable insights to the burgeoning field of plant-based food science and pave the way for the development of novel and health-enhancing food formulations.

2. Evaluating hemp and rapeseed protein quality

Protein quality is measured using various methods that assess the amino acid composition and digestibility of the protein. Some of the most effective and commonly used methods include calculating 2 scores: PDCAAS and/or DIAAS. PDCAAS stands for Protein Digestibility Corrected Amino Acid Score while DIAAS stands for Digestible Indispensable Amino Acid Score [12].

PDCAAS evaluates protein quality by comparing the amino acid profile of a protein to a reference protein pattern established by the Food and Agriculture Organization (FAO) and the World Health Organization (WHO) [13]. PDCAAS takes into account both the amino acid content and digestibility of the protein, whereas DIAAS is a newer method developed by the FAO that considers only the digestibility of the protein, specifically the digestible indispensable amino acid content [14].It provides a more accurate assessment of protein quality compared to PDCAAS, especially for proteins that are less well-digested. Both PDCAAS and DIAAS methods may be useful to evaluate the nutritional quality of an animal or plant-based proteins and guide food formulation and dietary recommendations. Each method has its strengths and limitations, and researchers often use multiple approaches to assess protein quality comprehensively.

As hemp most predominant amino acids are edestin and 2S albumin, which are two highly digestible globular proteins [15] the PDCAAS score for the industrial hemp and hemp by products is ranged between 48% for hemp seed meal and 66% for dehulled hemp seeds respectively. Comparing to casein’s 100% PDCAAS or beef with a PDCAAS of 92%, hemp protein has a relatively low digestibility. However, it has been scientifically proved that a lower digestibility of plant based proteins, such as grains or legumes including hemp are strictly correlated with the presence of anti-nutritional factors, such as phytic acid and trypsin inhibitors identified in hemp seed. [16] [17] In comparison with other plant based sources of protein, hemp has a similar PDCAAS score with black and pinto beans, as well as lentils [18].

While both hemp and rapeseed are considered complete sources of protein, meaning they contain all essential amino acids, the specific PDCAAS values vary depending in different researches based on factors such as crop, protein concentration, extraction method, processing method and digestibility.

To improve hemp’s protein digestibility score, various modern treatment techniques were applied. Ultrasonication and Ph shifting were proven to have a positive effect on the hemp’s protein structure by increasing the solubility, emulsifying activity and foam capacity [19] [20] [21] [22] [23] [24] [25] [26], as well as to increase the amphipathic property of the proteins by altering their globular structure [25] [27] [28]. There is also another method named supercritical CO₂ extraction that allows a gentle extraction of all important bioactive compounds and minimize the use of solvents, making it a safer alternative to traditional extraction methods [29]. Moreover, in order to provide suitable amounts of all 9 amino acids hemp protein can be paired with pea, soy, oat, and/or microalgae. These combinations enable formulators to develop new products with a high protein quality chemically close to those of animal origin [30].

The nutritional quality of rapeseed protein, in terms of PDCAAS score, is higher than hemp protein and it is comparable to that of soy protein (Table 1). Although, the amounts of sulfur-containing amino acids, methionine and cysteine in canola protein exceeds the nutritional requirements for both children and adults, while soy protein and casein both fall short of the requirements for infant nutrition and only casein meets the requirements for higher age categories [31]. As well as hemp protein, rapeseed protein contains anti-nutritional factors such as erucic and phytic acid, glucosinolates, and some protease inhibitors. Different extraction techniques, including heat treatment [29], ultrafiltration [30], nanofiltration [31], alkali extraction combined with membrane processing [32], and protein micellar mass processing [33], are employed to decrease the levels of these compounds, thereby enhancing the PDCAAS score.

The DIAAS score place hemp at the same range with cooked kidney beans, lentils, wheat and whey. These protein sources are classified in the no quality claim category (DIAAS <75). However, by associating hemp protein with rapeseed or soy, the nutritional requirements of different ages can be met. The increased DIAAS values obtained from mixtures show the potential to achieve a protein nutritional efficiency with sustainable protein sources. Nutritional efficiency lies in meeting physiological requirements with minimal intake of high-quality protein, as opposed to higher protein intake of low-quality protein [19].

To be noted that besides digestibility, the amino acid profile of cooked proteins food can differ greatly from the raw form due to a potential loss of soluble protein fractions into the boiling liquid and through the formation of amino acid derivatives,[32],[33];,[34]). With an altered amino acid composition, the DIAAS value of the cooked protein, and possibly its limiting amino acid, may differ strongly. Animal-based proteins are also subjected to protein quality variation as a result of processing.

The understanding of DIAAS method offers an opportunity to enhance no quality sources of plant based proteins such as hemp, fava bean, oat, pea, lentils with high quality ones, such as rapeseed or soy, therefore to create mixtures with an enhanced nutritional value and improved functionality.

Table 1. PDCAAS and DIAAS evaluation of plant-based and animal proteins.

Food source	PDCAAS(%)	Food source	DIAAS(%)
Casein	100	Milk protein concentrate	118
Egg white	100	Egg	101
Soy protein concentrate	99	Soy protein concentrate	91.5
Dehulled hemp seed	66	Defatted hemp hearts [35]	45
Rapeseed protein concentrate	93	Rapeseed protein isolate[36], heat-treated	100-110
Soy protein isolate	92	Soy protein isolate	83-97
Beef	92	Beef	111.6
Rapeseed protein isolate	83	Rapeseed protein isolate [29]	76-83
Hemp seed	51	Hemp seed [37]	54
Hemp seed meal	48	Hemp seed meal	-
Pea protein concentrate	73	Pea protein concentrate	82
Kidney beans	68	Cooked kidney beans	58.8
Peas	61-68	Peas	64.7
Pinto beans	57-63	Cooked pinto beans [38]	83
Rolled oats	57	Cooked rolled oats	54.2
Black beans	53	Black beans [39]	49
Peanuts	52	Roasted peanuts [40]	43.34
Lentils	51-52	Split red lentils	50
Whole wheat	40	Wheat	40-48

¹ PDCAAS - Protein Digestibility Corrected Amino Acid Score, %; DIAAS- Digestible Indispensable Amino Acid Score, %.

Table 1. PDCAAS and DIAAS evaluation of plant-based and animal proteins.

Food source	PDCAAS(%)	Food source	DIAAS(%)
Casein	100	Milk protein concentrate	118
Egg white	100	Egg	101
Soy protein concentrate	99	Soy protein concentrate	91.5
Dehulled hemp seed	66	Defatted hemp hearts [35]	45
Rapeseed protein concentrate	93	Rapeseed protein isolate[36], heat-treated	100-110
Soy protein isolate	92	Soy protein isolate	83-97
Beef	92	Beef	111.6
Rapeseed protein isolate	83	Rapeseed protein isolate [29]	76-83
Hemp seed	51	Hemp seed [37]	54
Hemp seed meal	48	Hemp seed meal	-
Pea protein concentrate	73	Pea protein concentrate	82
Kidney beans	68	Cooked kidney beans	58.8
Peas	61-68	Peas	64.7
Pinto beans	57-63	Cooked pinto beans [38]	83
Rolled oats	57	Cooked rolled oats	54.2
Black beans	53	Black beans [39]	49
Peanuts	52	Roasted peanuts [40]	43.34
Lentils	51-52	Split red lentils	50
Whole wheat	40	Wheat	40-48

¹ PDCAAS - Protein Digestibility Corrected Amino Acid Score, %; DIAAS- Digestible Indispensable Amino Acid Score, %.

3. Amino acid profile

Both rapeseed and hemp proteins are considered complete proteins, meaning they provide all essential amino acids required by the human body. However, the composition and quantity of amino acids vary between the two.

As indicated by Sobhy Ahmed El-Sohaimy et al. [43], hemp contains a substantial quantity of edestin, which is the predominant protein type in hemp seeds, followed by a significant proportion of globulin (67% - 75%) and globular albumin, ranging between 25% and 37% [44].

Overall, several researches discovered that hemp seeds contain about 181 different proteins, which makes hemp a valuable source of biological active compounds, polyunsaturated fatty acids, enzymes and micronutrients benefic for the human body. Moreover, some of the enzymes found in the hemp seeds can be used to produce hydrolyzed proteins that can be successfully used in nutraceutics or as a con ingredient is various functional foods, as potential hypotensive agents and antioxidants [41] [42,43,44,45]. From the chemical point of view, edestin, which is a hexameric 11S protein, easily digestible, contains significant amounts of all essential amino acids, especially sulfur amino acids and arginine [46]. Foods formulated with addition of arginine contained in the hemp seeds has proven to prevent or help treating cardiovascular diseases, by regulating the blood pressure [47]. Despite high quality storage proteins, hemp seeds also contain other health-promoting amino acids, such as sulphur-containing methionine and cysteine (3,5%-5,9%). When it comes to valuable/important amounts of fatty acids hempseed oil contains over 80% polyunsaturated fatty acids (PUFAs), making it a valuable source of essential fatty acids (EFAs), specifically linoleic acid (18:2 omega-6) and alpha-linolenic acid (18:3 omega-3). The omega-6 to omega-3 ratio (n6/n3) in hempseed oil typically falls between 2:1 and 3:1, considered optimal for human health. Additionally, hempseed oil contains the biological metabolites gamma-linolenic acid (18:3 omega-6; 'GLA') and stearidonic acid (18:4 omega-3; 'SDA') [48].

Nevertheless, hemp seed oil comprises a substantial quantity of tocopherols and tocotrienols (ranging from 100 to 150 mg per 100 g of oil), along with phytosterols, phospholipids, carotenes, and minerals [49] [50].

In summary, the well-balanced and diverse amino acid profile of hemp protein makes it an excellent and nutritionally-rich choice to support the human health and diet and meet essential needs of the health conscious modern consumers.

According to both amino acid profiles, hemp protein stands out for its well-balanced profile, rich in essential fatty acids, and contains a higher concentration of arginine, an amino acid with potential cardiovascular benefits. Rapeseed protein, on the other hand, has a more favorable lysine-to-arginine ratio.

Comparing to hemp protein, rapeseed protein profile consists of over 45 different proteins, which is way less than hemp: 20 weakly acidic, approximately 20 neutral, and 5 basic and has a distinct profile among other plant based sources of protein. Rapeseed proteins are known to have structural, catalytic and storage functions.[51]. The major storage proteins contained in rapeseed seeds are the 12S globulin (cruciferin) and the 2S albumin (napin), making up more than 70% of total rapeseed proteins [52].

Napins, characterized by their small molecular weight albumins (15–17 kDa), exhibit solubility across a broad pH range and possess remarkable heat stability (with a denaturation temperature Td ≥ 100 °C) [50]. The hydrophobic regions of napins are concentrated on a single side of the protein, resembling a Janus particle [51].

On the other hand, cruciferins are globulins with a higher molecular weight (300 kDa) and adopt a hexamer structure composed of two trimers [52]. The hydrophobic domains of cruciferins are distributed extensively over the protein's surface and are also nestled within the trimeric units of cruciferins [53]. Compared to napins, the hexameric structure of cruciferins is more susceptible to undergoing structural alterations and unfolding in response to changes in temperature and pH [49,50].

Oleosin is a minor protein (1–4% by weight) present in canola seed, which functions as a stabilizer at the surface of the oil bodies so that the oil remains in the form of discrete droplets in the oil seed [53]. Nevertheless, rapeseed also consists of lipid transfer proteins and other minor proteins of non-storage nature [52].

Overall, rapeseed contains high glutamine, glutamic acid, arginine and leucine contents and low amounts of sulfur-containing amino acids, which are relatively altered during the industrial oil extraction process. Indeed, the amino acid composition depends on the process used for protein extraction from the canola meal residue. Usually, up to 30% of the total [54].

Although there are well established techniques to separate the soy protein or flax seeds protein, there is a lack of well-studied extractions methods for rapeseed protein, therefore alternative technologies and conditions are needed due to the differences in seed chemistry and protein profile. Details of rapeseed as a protein source in human diet, based on research data, are also rare to find.

Although not enough studied, the viability of incorporating rapeseed meal proteins into food processing is proved by the well-balanced amino-acid profile. Moreover, rapeseed/canola protein outperforms lentils, beans and hemp protein and meets the amino acid requirements recommended by FAO/WHO/UNU for both adults and children [55].

A widely acknowledged correlation already exists between the incorporation of plant proteins into functional foods, nutraceuticals, and various natural health products, due to their amino acid profile and nutritional value, contributing to health promotion and the positive effect it has on preventing various diseases. Plant proteins play a significant role in the food industry, and among them, rapeseed and hemp are recognized as promising co-ingredient suitable for human nutrition/diet.

4. The anti-nutritional factors of hemp and rapeseed proteins

Hemp, as well as rapeseed contain a list of off-flavor, allergenic and anti-nutritional factors. These compounds affect directly the global acceptability of the oilseeds and their by-products used in the human nutrition; however the taste and chemical behavior can be improved by protein modification. Processing techniques, such as heat treatment, are often employed to mitigate these undesirable compounds [56].

Brassica oilseeds, grains and legumes such as hemp and rapeseed but also mustard, Brussels sprouts, cabbage, cauliflower, horseradish, kale and other crops contain a series of anti-nutritive elements, which can behave both: beneficial or harmless (differently) for the animal and human food use, depending on processing conditions [57]. Anti-nutritional factors mainly refer to the glucosinolates and their derived forms isothiocyanates, naturally produced by Brassica plants as a self-defense mechanism through various metabolic processes or mechanisms in order to avoid to be eaten.

However, for the food product development, other anti-nutritional elements must be considered, such as: low molecular weight phenolic compounds, polyphenolic tannins, enzyme inhibitors, phytates and phytic acid as they influence the nutritional and sensory characteristics of the new products [58].

The development of new products using hemp meal requires careful consideration due to the potential presence of anti-nutritional components. One primary reason for the limited large-scale manufacturing of hemp products is the inherent risk of contamination in the final product. Hemp naturally contains variable amounts of condensed tannins, trypsin inhibitors, phytic acid, and saponins, which significantly diminish protein availability either by precipitating it or by inhibiting digestive enzymes [59,60,61,62,63] Processes such as chelation or complex formation (involving phytic acid, condensed tannins, and saponins) can further decrease the absorption of mineral elements and vitamins [15,59,61,64].

Condensed tannins found both in hemp and rapeseed are considered anti nutritional factors due to their ability to form undesirable complexes with proteins and other macromolecules such as starch, thus reducing the nutritional value of the product [65].. Although, as condensed tannins are generically phenolic compounds and can have benefic effect on human health due to their antioxidant capacity associated with phenolic rings presented in their structure [66].

Another important anti nutritional factor found predominantly in nuts, legumes and seeds such as hemp is phytic acid, the stored form of phosphorus, that works in the human body as a mineral inhibitor promoting mineral deficiency by chelating bivalent minerals like calcium, iron, zinc, and copper, as well as starch, protein, and enzymes [67]. As well as condensed tannins, ingested in low amounts may provide several beneficial effects, proven by several recent studies due to antitumor and antioxidant capacities. It is also known that phytates can interact with proteins due to the affinity of phosphate groups for cationic amino acids. This interaction can be harmful, disrupting protein digestion, but it can also protect the human body from harmful effects of specific proteins, such as oxidases and pathogenic proteins and several diseases like diabetes [68,69].

Third group of anti-nutritional factor called saponins, biologically represent surfactants with lipophilic aglycone and hydrophilic glycosyl groups sursad. Saponins have been shown to affect protein digestibility of hemp by binding the activity of certain metabolic catalysts such as trypsin and chymotrypsin, thus decreasing the physiological availability of nutrients and enzymes [69].

It's important to note that the presence and levels of these antinutritional factors can vary among different varieties of hemp and may be influenced by factors such as growing conditions and processing methods. Researchers and nutritionists assess these factors to understand their impact on the nutritional quality of hemp products and to develop strategies to mitigate their effects. Processing techniques such as heat treatment or fermentation can sometimes help reduce the levels of anti-nutritional factors in hemp products. Additionally, proper preparation methods, such as soaking and cooking, can contribute to minimizing the impact of these factors when incorporating hemp into diets.

Main anti nutritional factors contained in rapeseed are glucosinolates, sinapine, sinapic acid, tannin, phytic acid and mucilage [70].

Glucosinolates, which are glycosides of β-d-thioglucose, and myrosinase activity continues to be the most serious factor influencing the quality of rapeseed oil and meal and limiting the increased utilization of these products.

Rapeseed meals which contain intact glucosinolates cannot be used as a protein source for human nutrition due to the possibility of hydrolysis during digestion or the presence of myrosinase in other foods. Recently, several procedures have been devised for the complete aqueous extraction of glucosinolates from rapeseed meal (Ballester et al., 1970), ground rapeseed and, by diffusion, from the intact rapeseed [71,72,73].

Common rapeseed meal contains significant amounts of glucosinolates, with the main five types being 3-butenylglucosinolates, 4-pentenylglucosinolates, 2-hydroxy-3-butenylglucosinolates, 2-hydroxy-4-pentenylglucosinolates, and 2-allylglucosinolates. Brassica napus meal typically contains 3-butenylglucosinolates and 2-hydroxy-3-butenylglucosinolates, while Brassica rapa meal includes 3-butenylglucosinolates. It's essential to limit the total glucosinolate content in rapeseed meal for animal feed to 2.5 μmol/g, as elevated levels of these antinutritional compounds can lead to physiological disorders in animals, including hemorrhagic liver. Prolonged consumption of glucosinolate-rich foods may result in liver, kidney, and thyroid gland enlargement in humans [66].

Moreover, the bitterness associated with certain glucosinolates in rapeseed meal can impact the acceptability of the final product. Nevertheless, glucosinolates are recognized for their natural antimicrobial and anti-carcinogenic properties [67].

Sinapine, another anti nutritional factor presented in 70-80% of rapeseed polyphenols, is an acetylcholinesterase inhibitor [74]. Sinapic acid (SA, 4-hydroxy-3,5-dimethoxy-cinnamic acid) is the predominant free phenolic acid found in rapeseed [75]. Sinapine, also known as sinapoylcholine, is a compound found in various plants, including mustard seeds, rapeseeds, and certain other cruciferous vegetables. It is a type of alkaloid and is commonly present in the seed coats of these plants. While sinapine is not typically considered highly toxic for humans, it's important to note that excessive consumption or exposure to high levels of any compound can potentially lead to adverse effects.

Erucic acid, a monounsaturated omega-9 fatty acid, mainly common for rapeseed and mustard seeds can constitute about 30 – 60% of the total fatty acids of natural rapeseed. The toxic effect of erucic acid was studied on animals as the exposure to diets with oils containing excessive erucic acid may lead to adverse health effects, with the heart as the principal target organ. The most common effect in the experimental animals is myocardial lipidosis, an accumulation of lipids in heart muscle fibres that may reduce the contractile force of heart muscles. So far, no evidence that dietary exposure of erucic acid is correlated to myocardial lipidosis has been established yet in humans nevertheless [76]. However there is no data to prove any heart disease associated effects associated with the human diet. Also the crops that are used for food product development are cultivates specifically with low erucic acid content. Although natural forms of rapeseed and mustard contain high levels of erucic acid (over 40% of total fatty acids), levels in rapeseed cultivated for food use are typically below 0.5%. Erucic acid is regulated by the European Food Safety Authority (EFSA) and the US Food and Drug Administration (FDA). In the EU, it is limited to a maximum of 5% of the total fatty acid content in food products [77]. However, exists special crops of rapeseed named High erucic acid rapeseed (HEAR) is a specialty rapeseed selected for its high erucic content. It has over 50% erucic acid and is grown as a key ingredient for plastics, personal care products and pharmaceuticals [78].

It's important to mentioned that nowadays the advancements in breeding and processing techniques have been employed to reduce the levels of these anti-nutritional factors in rapeseed and its products, making them safer for consumption. Canola oil, for example, is derived from low erucic acid rapeseed varieties and has a favorable nutritional profile.

5. Bio active compounds

The rising number of health conscious consumers and the significant growth of modern consumers seeking with enthusiasm for functional foods have led to an increased demand for plant-based products that provide natural remedies for various diseases. Both hemp and rapeseed has to offer important bioactive compounds with nutraceutical properties.

Hemp seeds are notably rich in polyphenols (mainly flavonoids, stilbenoids, and lignanamides), alkaloids, cannabinoids, and terpenoids [79]. Flavonoids represent secondary plant metabolites composed of polyphenolic compounds with antioxidant properties that directly contribute to the hemp’s color, flavor, and potential health benefits. Hemp seeds contain unique type of flavonoids that cannot be found in any other plants, such as cannflavin A, cannflavin B, and cannflavin C [80,81]. Other kinds of flavonoids contained in hemp include quercetin, apigenin, and kaempferol. Quercetin is studied due to its anti-inflammatory properties preventing Chronic inflammation linked to various health conditions, including heart disease, diabetes, and certain types of cancer [82]. Several studies also suggest that quercetin may have positive effects on cardiovascular health. It may help lower blood pressure, reduce cholesterol levels, and improve overall heart function [83]. Moreover, the flavonoids present in hemp act in a synergistic action with other compounds such as the cannabinoids and terpenes to produce antioxidant, antidepressant, anti-inflammatory, and disease fighting properties [84].

Cannabinoids are a class of chemical compounds found in the cannabis plant, including hemp (Cannabis sativa). Hemp is known for its relatively high levels of certain cannabinoids, with a particular focus on cannabidiol (CBD) and Tetrahydrocannabinol (THC) [85]. The effect of administrating Cannabidiol is currently investigated in mood disorders such as anxiety, control for chronic pain, anti-inflammatory diseases, neurodegenerative diseases such as Alzheimer and Parkinson disease, and antitumorigenic properties. Of note, Canabidiol is successfully used as a medicine against the seizure disorders Lennox-Gastaut syndrome and Dravet syndrome [86]. Industrial hemp contains no more than 0.3% concentration (on a dry weight basis) of the psychoactive compound delta-9-tetrahydrocannabinol (THC), due to Applicable European and Federal law.

It's important to note that the therapeutic effects and potential health benefits of cannabinoids are an active area of research, and more studies are needed to fully understand their mechanisms and applications.

In addition to phytocannabinoids, hemp also contains terpenes, aromatic compounds found in many varieties of plants, including hemp. They contribute to the plant's flavor and aroma profile [87,88]. Terpenes in hemp may also have potential therapeutic effects and can work synergistically with cannabinoids in what is known as the "entourage effect. So far, almost 120 different terpenes were found in hemp, but most Common are myrcene, pinene, limonene, and linalool [89].

Another source of bioactive compounds identified in hemp are phytosterols. They currently present high interest for pharmaceutical companies due to a wide range of benefic actions. One of the primary uses of phytosterols is in managing cholesterol levels. By reducing LDL cholesterol levels, phytosterols contribute to overall cardiovascular health [90]. Some research suggests that phytosterols may have anti-inflammatory effects and also can modulate the immune system [91]. Of note, Hemp is a nutritious plant that contains a variety of vitamins and minerals, such as Vitamin E, particularly gamma-tocopherol, Magnesium , Phosphorus, Potassium, Zinc, Iron, Cooper, Manganese and B Vitamins making it a valuable addition to a balanced diet [92].

Over the years, in the rapeseed has been identified various health-promoting compounds such as: polyphenols phytosterols, carotenoids, Omega-3 Fatty Acids, vitamin E and Squalene. However, it’s worth noting that the composition and the amount of bioactive compounds contained in rapeseed can vary based on several key-factors: crop/species, growing conditions, and processing methods.

Phenolic acids and their derivatives, along with both soluble and insoluble tannins, constitute the primary phenolic bioactive compounds present rapeseed. Reports indicate that rapeseed meal can contain as much as 6% tannins. Hence, utilizing hulls, post-dehulling, as a source of natural antioxidants offers a potential avenue for their practical utilization [64].

Research indicates that rapeseed possesses a higher phenolic component content in comparison to other seeds within the oilseed category. The phenolic compounds extracted from rapeseed have proven efficacy as potent antioxidants, finding successful applications in the realms of food, cosmetics, and pharmaceuticals [93].

From the chemical point of view, there is a total of approximately 400 mg per kg of concentration of all identified phenolic compounds in rapeseed meal. Sinapic acid stands out as the predominant phenolic compound, constituting over 85% of all quantified phenolic compounds, with an average concentration of 357 ± 13 mg/kg and a range of 339–379 mg/kg. Among hydroxycinnamic acid derivatives, sinapine emerges as the most abundant bioactive compound in rapeseed. Its noteworthy properties, including antitumor, neuroprotective, antioxidant, and hepatoprotective attributes, underscore its significance for promoting health [94]. Remarkably, polyphenolic compounds, which have attracted considerable interest in recent years, are thought to confer numerous health benefits by modulating metabolic disorders, potentially through interactions with the gut microbiota [90], [91]. Among the most active antioxidant components discovered in the polar fraction of rapeseed extracts is canolol (4-vinylsyringol or 2,6-dimethoxy-4-vinylphenol). Canolol is formed through the decarboxylation of sinapic acid during the roasting process of rapeseed [92]–[94].

Furthermore, nutraceutical companies are keen on substituting synthetic antioxidants like butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG), and tert-butylhydroquinone (TBHQ) with natural plant alternatives, as the synthetic counterparts have been shown to be carcinogenic. Several previous studies have illustrated that the unsaturated fatty acids and phytosterols present in rapeseed oil can effectively reduce both total cholesterol and "bad" cholesterol (such as low-density lipoprotein, LDL), while simultaneously maintaining the levels of "good" cholesterol (e.g., high-density lipoprotein, HDL). This dual action not only decreases the susceptibility to cardiovascular diseases but also acts as a preventive measure against clotting and the proliferation of vascular smooth muscle. The positive outcomes are often attributed to the optimal ratio of omega-6 to omega-3 polyunsaturated fatty acids (PUFAs), which is approximately 2:1, as supported by research studies [95], [96].

Beyond their lipid solubility, these micronutrients showcase a broad spectrum of biological properties, encompassing antioxidant, anti-inflammatory, and anticancer activities [95,96].

Omega-6 fatty acids, particularly linoleic acid and its derivatives such as γ-linolenic acid, are well-known for their beneficial effects on health and are abundant in rapeseed oil. Research indicates that a diet rich in γ-linolenic acid can effectively reduce elevated levels of blood lipids, lower high blood pressure, and regulate skin perspiration [97,98]. Moreover, γ-linolenic acid demonstrates various physiological roles, including anti-cancer properties, anti-thrombotic effects on the cardio-cerebrovascular system, and advantages in managing diabetes [99] [100]. Conversely, α-linolenic acid is linked to physiological functions such as anti-atherosclerotic effects, facilitation of weight loss, reduction of blood lipid levels, and prevention of cardiovascular and cerebrovascular diseases. The distinctive fatty acid composition found in rapeseed oil contributes to a spectrum of biological functions that support human health [101].

Carotenoids and Vitamin E presented in rapeseed protein and meal has also health promoting benefits. Main type of carotenoid found in rapeseed is (all-E)-lutein, but studied carried by blab la also determined in cold pressed rapeseed oil a minor amount of (all-E)-zeaxanthin [102]. Lutein and zeaxanthin work by protecting the retina of the eye from the effects of aging. These carotenoids may prevent macular degeneration. Clinical studies have also shown that lutein's anti-oxidative and anti-inflammatory properties provide benefits by protecting and alleviating other ocular diseases like cataracts, diabetic retinopathy, myopic, and retinopathy of prematurity [103]. Rapeseed oil contains relatively high levels of tocopherols (Vitamin E) and moderate levels of vitamin K comparing to other plant oils [101].

Overall, these bioactive compounds collectively contribute to the nutritional value and health-promoting properties of rapeseed and its derived products. Research suggests that the bioactive components in rapeseed, such as phytosterols with cholesterol-lowering effects and omega fatty acids with cardiovascular benefits, may have positive implications for human health. Furthermore, the antioxidant, anti-inflammatory, and potentially anticancer properties associated with polyphenolic compounds in rapeseed oil add to its overall health-promoting profile. As our understanding of these bioactive compounds continues to grow, incorporating rapeseed and its oil into a balanced diet may offer a range of potential health benefits.

6. Food applications

The use of industrial hemp in the human diet has been a subject of debate for decades, primarily due to its chemical composition and the presence of cannabinoids, known for their potential psychotropic effects in larger quantities. In the United States, the Agriculture Improvement Act of 2018, commonly known as the 2018 Farm Bill, legalized the cultivation of industrial hemp. According to the bill, industrial hemp is defined as cannabis sativa plants containing 0.3% THC or less on a dry weight basis [104]. Similarly, the European Union, regulations regarding industrial hemp and THC content are established by individual member states; however the THC levels did not exceed 0.3% [105]. Compliance with this THC threshold is crucial for hemp cultivation and the production of hemp-derived products.

Hemp protein, meal, and seed-based products (Figure 3) are readily available in various combinations on the global market. Thanks to its versatility, hemp can be consumed raw as hemp hearts (seeds) or in a processed form as powder, meal, oil, and flour. However, the most significant impact lies in serving hemp as a co-ingredient in various food products, elevating their nutritional value and asserting a compelling functional potential [106,107,108]. For the functional foods segment, hemp stands out as an exceptionally fitting food ingredient. This is attributed to its noteworthy nutritional content and the array of health benefits it offers. Nowadays, manufacturers use industrial hemp in yogurt, snack bars, cookies, bread, pasta, milk, butter, ice cream, beyond meat, tofu and other innovative/ functionally improved products [109].

Seed processing techniques such as germination have been reported to promote changes in the phytochemical profile of seeds and have drawn interest in the commercial development of sprouts enriched in specific phytochemicals [110].

A study reported an increased polyphenol, flavonoid contents, antioxidant activity, and protein concentration of hemp sprouts produced under blue (B) light-led emitting diode compared to raw seed [111]. Additionally it has been proven that hemp sprouts possess no hallucinogenic effects, do not contain high delta-9-tetrahydrocannabinol, and thus can be safely consumed without any concerns of negative health impact [112].

Hemp seed can be also processed and manufactured into high-moisture meat analogues and hemp milk.

A high-quality and nutritious hemp milk was developed from seeds. Such milk contains about 25–30% protein and 35% fatty acids with an optimum essential omega-3 and omega-6 fatty acid content [113],[114].

Collectively, these findings demonstrate that hemp can be an excellent nutritional source of important bioactive compounds and can be successfully used for the new food product development, based on known knowledge and new experiments.

Same to hemp, rapeseed, available in various forms on the marker, as protein powder, meal, cake, flour or oil (Figure 3) may also be incorporated into some food products, particularly those designed to boost nutritional content.

Rapeseed has been consumed by humans as a condiment for about 3000 years. The original use of rapeseed-mustard was to mask the taste of degraded perishables. The spiciness of rapeseed-mustard is caused by a group of compounds called isothiocyanates [8].

The most used rapeseed product is rapeseed oil, also known as canola oil, a popular choice worldwide for cooking oils due to its neutral flavor, high smoke point, and healthy fat profile. It is commonly used for frying, sautéing, baking, and salad dressings.

Rapeseed oil is also used as a key ingredient in the production of margarine and spreads, providing a plant-based alternative to butter [115]. Another plant based alternative based on rapeseed oil is mayonnaise, as rapeseed oil contributes to its creamy texture and rich flavor. When it comes to the preparation of salad dressing, marinades and sauced adding rapeseed oil gives a smooth texture and mild flavor.

Rapeseed cake, protein, and oil are gaining popularity as co-ingredients for the baking goods, such as cakes, bread, biscuits and gluten free pasta. The use of rapeseed-based products is proven to enhance moisture retention and texture, extending the shelf life of the product but also improving the nutritional value of the final products.

Another study suggests that rapeseed flour, made from ground rapeseed meal, can be used as a gluten-free alternative in baking and cooking. Functional foods made with rapeseed flour are suitable for individuals with celiac disease or gluten intolerance. Several patents are proposed to patent the use of rapeseed protein for the production of diary-free-alternatives such as plant-based milks, yogurts, and cheeses, to provide protein and improve mouthfeel [116].

With a biorefinery approach, rapeseed proteins may be extracted and recovered for high-end uses to fully exploit their nutritional and functional properties. Several studies have been carried out in recent years on the applications of rapeseed/canola proteins in food products as a partial or total replacement of animal proteins. Depending on the food application tested, rapeseed proteins have been proposed as a thickener ingredient or as an emulsifier, binder, foaming, or gelling agent able to modify texture or simply to fortify the protein content of a product. The range of possible food applications for rapeseed/canola proteins include bakery and dairy products, meat, confectionery and beverages, as well as dressings, sauces, snacks or flavorings [117,118,119,120].

Meat alternatives incorporating rapeseed protein have been deemed acceptable based on their nutritional composition, deemed sufficient to fulfill human requirements for essential amino acids [121]. However, the taste of rapeseed protein is reported to be unfavorable due to the presence of free and esterified phenolic acids [54]. Nonetheless, enhancements in taste can be achieved by steaming the protein concentrate and incorporating it into sausage formulations, resulting in improved taste, texture, and a distinctive aroma, thus rendering it comparable to soy-based alternatives [116], [122],[123].

Another study highlights the potential of using rapeseed protein isolate as a food supplement for elderly people with mastication and dysphagia problems. The obtained results show that the texture modification of food combined with rapeseed protein isolate supplementation may have a positive impact on the nutritional and sensory profile of the products [118].

Thus, hemp and rapeseed proteins offer a versatile and nutritious option for food product development, contributing to a wide range of culinary applications and meeting the needs of consumers seeking plant-based alternatives with enhanced health benefits.

7. Conclusions

Both rapeseed and hemp protein offer promising protein quality, with hemp showcasing a rich content of edestin and rapeseed demonstrating a high PCDAAS score. Further research is needed to comprehensively evaluate their protein digestibility and amino acid bioavailability on a specific functional food product, applying various processing methods and treatments that will meet in the final instance the market needs.

The presence of anti-nutritional factors in rapeseed and hemp, such as condensed tannins, trypsin inhibitors, and phytic acid, underscores the importance of careful processing techniques to mitigate their effects. Advances in extraction and processing methods offer opportunities to minimize these compounds while retaining nutritional integrity.

Both rapeseed and hemp contain bioactive compounds with potential health benefits, including polyphenols, phytosterols, and omega fatty acids. Harnessing these compounds in food formulations could contribute to functional foods targeting specific health outcomes, such as cardiovascular health and inflammation management.

Rapeseed and hemp proteins hold promise for a wide range of food applications, including plant-based meat substitutes, dairy alternatives, and baked goods. Their functional properties, such as emulsification and foaming capabilities, make them suitable for various formulations, catering to the growing demand for alternative protein sources.

The future perspective of utilizing rapeseed and hemp proteins in food product development hinges on continued research and innovation. Addressing challenges related to taste, texture, and consumer acceptance will be crucial for mainstream adoption. Additionally, exploring novel processing techniques and genetic modifications could unlock further potential for enhancing nutritional quality and functionality.

In conclusion, rapeseed and hemp proteins offer exciting opportunities for the development of innovative and sustainable food products. With careful consideration of protein quality, anti-nutritional factors, bioactive compounds, and food applications, these plant-based protein sources hold immense promise for meeting the evolving demands of the modern food industry and promoting human health and well-being.