Bioactive Peptides from Dairy Products: A Systematic Review of Advances, Mechanisms, Benefits, and Functional Potential

Abstract

Bioactive peptides (BAPs) from dairy products have garnered increasing attention as natural agents with health-promoting properties, including antihypertensive, antioxidant, antimicrobial, immunomodulatory, opioid, and antidiabetic activities. This systematic review synthesizes research published between 2014 and 2024, retrieved from Scopus and PubMed, and selected according to PRISMA guidelines. A total of 192 studies met the inclusion criteria, collectively reporting over 3200 distinct peptides, with antihypertensive sequences, predominantly angiotensin-converting enzyme (ACE) inhibitors, constituting the largest category (n = 1237). β-casein was the principal precursor across bioactivities, followed by αs1-casein, β-lactoglobulin, and α-lactalbumin. Peptides were primarily produced via enzymatic hydrolysis, microbial fermentation, and gastrointestinal digestion, with peptide profiles influenced by the type of milk, microbial strains, and processing conditions. While cow’s milk remained the dominant source, investigations into goat, sheep, camel, buffalo, and donkey milk revealed species-specific biopeptides. Recent advances in proteomics have enhanced peptide identification and bioactivity prediction, enabling the discovery of novel sequences. These findings underscore the significant potential of dairy-derived BAPs as functional food components and nutraceutical ingredients, while highlighting the need for further in vivo validation, bioavailability studies, and broader exploration of underrepresented milk sources.

1. Introduction

Consumers nowadays are increasingly aware of the connection between health and dietary habits, which has sparked interest in nutraceuticals that provide consumers with both nutritional and health benefits [1]. Although proteins are well known for their biological, functional, and nutritional qualities, they require the process of hydrolysis, whether by fermentation or enzymatic digestion, to fully utilize these qualities [2]. Certain protein fragments known as “bioactive peptides” have positive impacts on human health by influencing the body’s physiological and metabolic processes [3]. Enzymatic hydrolysis of proteins by fermentation, digestive enzymes, and the enzymes of proteolytic microbes activates peptides, which are inactive in the maternal protein sequences [4,5]. After being released from their precursor proteins, these peptides bind to specific receptors on target cells and trigger distinct biological responses [6]. Bioactive peptides are typically found in food ingredients consumed daily [3]. The aforementioned bioactive peptides are typically two to twenty amino acids long with molecular weights (MW) between 300 and 3000 Da [7]. Several studies have shown that the hydrolysis of endogenous proteins produces bioactive peptides, which have a variety of physiological functions [8]. Considering protein hydrolysates contain a variety of bioactive peptides (BAP), they have attracted attention as possible therapeutic alternatives to improve human health. They have been linked to a number of health advantages, including anticancer, antidiabetic, antihypertensive, and antioxidant qualities [9]. The synthesis and sequencing of amino acids determine the potential action of biopeptides [10], and several peptides have been shown to exhibit multifunctional activities [11]. Furthermore, peptides are more accessible than protein molecules or free amino acids from a dietary perspective [12].

Milk’s nutritional benefits have long been established, and more recent research has identified bioactive milk ingredients that may enhance human health [13]. One of the most beneficial and most nutritionally dense foods is milk, which is regarded as a vital source of nutrients for human development, maintenance, and overall health [14]. In the meantime, milk proteins are the primary source of a variety of physiologically active peptides that have attracted particular attention due to their potential to affect a wide range of physiological processes in the body [15,16]. Bioactive peptides produced from milk proteins have drawn a lot of interest due to their potent activity, ease of development, variety of sources, and level of safety [17]. Milk proteins, which are known to be a significant source of peptides with bioactive qualities, are produced by the enzymatic hydrolysis of casein and whey protein fractions. Furthermore, when lactic acid bacteria (LAB) ferment milk, the dairy proteins are hydrolyzed into oligopeptides by intracellular peptidases and cell wall-bound proteinases, which break down into shorter peptide fragments [18,19,20]. Antimicrobial, antioxidant, dipeptidyl peptidase-IV (DPP-IV) and angiotensin-converting enzyme (ACE) inhibition, antihypertensive, and immunomodulatory properties are all exhibited by dairy-based peptides with bioactive functions [21,22]. Milk-derived biopeptides can be regarded as potential components of functional food [23,24]. The majority of peptides appear to be produced during gastrointestinal digestion [25,26], while processing variables including heat treatment, starter cultures, and ripening may have an impact on the dairy’s peptide profiles [27]. Milk protein hydrolysates and fermented dairy products such as cheese, yoghurt, kefir, and others have been found to contain an increasing amount of bioactive peptides [21]. In terms of protein quantity, caseins make up to 70–80% of the total protein in milk, being the most significant protein in most dairy products [28,29]. The four main caseins (αS1-, αS2-, β-, and κ-caseins) are present in milk in various proportions [28]. The whey fraction of milk is mostly composed of water (94–95%, w/v), lactose (3.8–4.0%, w/v), proteins (0.8–1.0%, w/v), and minerals (0.7–0.8%, w/v) [30]. The whey protein pattern, which includes immunoglobulins, lactoferrin, lactoperoxidase, bovine serum albumin, β-lactoglobulin, α-lactalbumin, and glycomacropeptide, has a variety of physiological functions that contribute to both illness prevention and therapy as well as health enhancement [31]. The primary dairy sector by-product, whey, is created after casein coagulation throughout the dairy-making procedure, like cheese, Greek yogurt, etc. [32].

Among different species’ milk, bovine milk is the most studied in terms of biopeptides; however, many Eastern European, African, and Asian nations use many different types of milk coming from different sources, such as camel, goat, and sheep milk, in addition to bovine [28]. Humans are moving away from cow’s milk for a number of reasons, including the perception that milk from alternative sources has various health benefits, for instance, being less allergenic due to the absence of β-lactoglobulin (β-Lg), the primary allergen in ordinary milk [33,34]. The amount of casein varies depending on the type of milk; sheep milk has the largest casein concentration [35]. Additionally, the four main caseins—αS1-, αS2-, β-, and κ-caseins have varying incidences that are correlated with the type of milk [36].

Understanding the nutritional value and potential health benefits of peptides from different milk types and fermented dairy products requires a deeper knowledge of their biological properties [37]. Bioactive peptides appear to function similarly to chemically produced medications in their interactions with the human body’s enzymes and proteins; however, they lack the toxicity and the frequent side effects associated with the latter [38]. The detection of peptides with beneficial properties and the evaluation of the health effects of their consumption is achieved by peptidome analysis of milk and other dairy products [39]. The enzymatic profile and activity of the dairy products, which can vary greatly depending on the production procedure and the source of the milk, result in a high degree of peptide variety.

This systematic review aims to comprehensively evaluate the scientific advancements during the past decade (2014–2024) concerning bioactive peptides derived from dairy products. It focuses on identifying the sources, the production methods, the structural characteristics, and the functional properties of these peptides, and particularly those obtained through enzymatic hydrolysis, fermentation, and gastrointestinal digestion. The review emphasizes especially on their bioactivities and health properties, also explores the influence of different milk types (e.g., cow, goat, sheep, camel) and fermentation microorganisms on peptide diversity and bioactivity. In particular, the structured overview of protein origins, bioactivities, and species-specific biopeptide profiles may serve as a reference framework for researchers seeking to prioritize promising peptide candidates for in vivo validation and clinical translation. By systematically analysing recent research, this review seeks to highlight potential knowledge gaps, technological advances, and possible applications of dairy-derived bioactive peptides in the development of functional foods and nutraceuticals. Additionally, this review aims to highlight the potential nutritional value of traditional dairy products across the globe.

2. Materials and Methods

2.1. Data Search Strategy and Data Sources

For the systematic review, electronic databases Scopus and PubMed were searched for peer-reviewed articles published between 2014 and 2024. The search strategy employed a combination of search terms and Boolean operators to identify relevant studies. The following search terms were used: (“bioactive peptides” AND cheese) OR (“bioactive peptides” AND milk) OR (“bioactive peptides” AND yoghurt) OR (“bioactive peptides” AND dairy) OR (“dairy peptides”) OR (“dairy biopeptides”). This Boolean expression was used to capture literature related to bioactive peptides in various dairy matrices, including cheese, milk, yoghurt, as well as studies that specifically mentioned dairy peptides or dairy biopeptides. After combining studies retrieved from the electronic databases and eliminating duplicates, the titles and abstracts of the remaining publications were screened for relevance to the review topic. Articles deemed potentially eligible were selected for full-text review based on the inclusion criteria.

2.2. Inclusion/Exclusion Criteria and Data Extraction

Studies were included if (1) they were conducted during the decade 2014–2024, (2) they included identification of peptides’ sequences, (3) they were published in English, (4) they did not present results from clinical trials, and (5) they did not study non-dairy synthesized peptides. Review articles were also excluded. The Systematic Review adheres to the PRISMA 2020 statement’s general methodology [40]. After obtaining the records of references deemed possibly relevant, the papers were incorporated using the inclusion criteria. The total number of records retrieved was 2846. Of those, 1024 were duplicates and were removed, and 764 were excluded for other reasons. Of the remaining 1058 papers, 832 were excluded based on the criteria used. The number of studies finally included in this systematic review was 192 (Figure 1). The present systematic review was registered at OSF registries with registration DOI: https://doi.org/10.17605/OSF.IO/79SW2 (accessed on 26 August 2025).

3. Production of Bioactive Peptides in Dairy

The generation of bioactive peptides in dairy products primarily occurs through enzymatic hydrolysis and microbial fermentation, both of which facilitate the proteolytic breakdown of milk proteins. These processes lead to the release of peptides with diverse biological activities, including antihypertensive, antioxidant, immunomodulatory, and antimicrobial effects [21]. Endogenous milk enzymes, coagulant-derived proteases, and enzymes from starter and adjunct cultures all contribute significantly to proteolysis during cheese manufacture and ripening [41]. Likewise, the metabolic activity of lactic acid bacteria and other microorganisms involved in dairy fermentation enhances the production of functional peptides, thereby improving the nutritional and therapeutic value of fermented dairy products. Furthermore, the profile of LAB utilized for dairy product fermentation and the variations in the peptide profile based on the microorganisms have been the subject of much research in recent years [20,42,43,44]. These mechanisms represent promising strategies for the research and development of functional foods with potential health benefits.

3.1. Enzymatic Hydrolysis

About 60 distinct enzymes are found in milk, the majority of which are produced during the production and release of the fat globule from the secretory cells’ cytoplasm into the mammary gland’s lumen [42]. Plasmin, a serine protease found in blood with maximum activity at pH 7.5 and 37 °C, is the main naturally occurring proteolytic enzyme in milk [42]. Coagulation residues, milk-specific enzymes, starting culture enzymes, and secondary microbiota enzymes can all promote proteolysis [45]. Many proteolytic systems involved in the production and ripening of cheese, such as coagulant-derived enzymes, cell-envelope proteinases, and naturally occurring milk enzymes like plasmin and cathepsin D, can release a variety of peptides [46]. Each of these enzymes is essential for the hydrolysis of whey and casein proteins, which releases biologically active peptides into the cheese’s matrix [47] (Table 1). Jeewanth et al. [48] indicated that the hydrolysis products of whey protein concentrates (WPCs) demonstrated enhanced ACE-inhibitory activity by releasing peptides that are inert in unaltered whey proteins under the effect of enzymatic activity. When referring to the hydrolysis of WPCs, they discovered that Protease S had the highest proteolytic activity among the other enzymes. Along with the other enzymes tested, protease S-treated WPHs had the strongest ACE-inhibitory impact, followed by alkalase [48]. Trypsin produced the peptide sequences LAMA and LDAQSAPLR following hydrolysis, while protease S released ACE-inhibitory active peptide LDAQSAPLR [48]. The primary enzyme in calf rennet, chymosin, releases caseinomacropeptide within the casein micelle and causes protein aggregation by cleaving κ-casein between the phenylalanine-126 and methionine-127 residues [49]. A milk protease called plasmin increases the amount of water-soluble peptides in cheese by aiding in the proteolysis process during the course of ripening [50].

Proteolysis during cheese ripening is a multifaceted process involving various enzymes that break down proteins into smaller peptides and amino acids, contributing to flavor and texture development. These enzymes include residual chymosin from the rennet, native milk proteinases like plasmin and cathepsins, and proteolytic enzymes from starter and non-starter microorganisms. Additionally, exogenous proteinases can be added to accelerate the ripening process [51]. Öztürk and Akın discovered that the enzymes that are efficient in the proteolysis of Tulum cheese include microbial proteolytic enzymes (intracellular and extracellular enzymes) that exhibit activity throughout ripening and enzymes identified in milk and coagulant (indigenous enzymes) [41]. The enzymes that aid in the ripening of cheese are derived from starter cultures, coagulation, and milk. Both the coagulants and the milk’s natural enzymes are crucial to initial proteolysis [45]. According to Zhang et al. [52], prolonging the storage time may help raise the distinctive biopeptide content of cheese because lengthy peptides degrade at specific enzymatic hydrolysis sites. Through the enzymatic hydrolysis of Rushan (cow milk) and Naizha (yak milk) cheeses, Shi et al. [53] simulated in vitro gastrointestinal digestion and found that this procedure produced a substantial amount of peptides, some of which had previously demonstrated biological activity and others with predicted immunomodulatory, antibacterial, ACE-inhibition, DPP-IV inhibitor, and antioxidant activities. Additionally, they discovered four new ACE-inhibitor peptides with IC₅₀ values of 109.5, 77.7, 196.6, and 64.30 μM, respectively: YPFPGPIH, LKNWGEGW, RELEEIR, and HPHPHLS [53]. A yeast utilized in the dairy business, Debaryomyces hansenii, exhibits strain-specific caseinolytic mechanisms that produce the antihypertensive sequences HLPLPL and HLPLP from β-casein [54].

3.2. Fermentation

Consuming fermented (dairy) products can mitigate the detrimental effects of contemporary Western-style dietary habits, which can change the composition of the gut microbiota [55]. When milk ferments to produce dairy products like yoghurt, cheese, kefir, etc., starter culture microbes’ proteolytic activity releases biopeptides from the protein contained in milk. Proteolysis is among the most significant processes during cheese ripening, and the interaction of age and cheese bacteria produces a particular peptide profile [56]. Proteolysis can liberate the amino acid sequences that are embedded in whey and casein proteins [55]. Some commercial dairy products, such as fermented milk in Europe, have been marketed for their potential blood pressure-lowering effects; however, these claims were not supported by European Food Safety Authority (EFSA). This case illustrates the translational potential of bioactive peptides; however, further clinical evidence is required to support their broader application. Aguilar-Toala et al. [57] utilized Lactiplantibacillus plantarum strains that had been isolated from semi-soft cheeses and demonstrated the multifunctional activities of peptides generated in fermented milk. In the same context, Pipaliya et al. [58], fermented sheep milk harboring Lactiplantibacillus plantarum KGL3A has the potential of delivering bioactive peptides exhibiting antihypertensive and antidiabetic effects. Martini et al. [59] indicated there is a favorable link between Lacticaseibacillus zeae and the occurrence of bioactive peptides that have anti-hypertensive as well as anti-microbial properties. Each of the species, Lacticaseibacillus rhamnosus, Lacticaseibacillus casei, and Lacticaseibacillus paracasei, had a positive association with one specific bioactive peptide (Lacticaseibacillus casei with the ACE-inhibitory peptide NLHLPLPLL; Lacticaseibacillus rhamnosus with the ACE-inhibitory peptide ENLLRF; Lacticaseibacillus paracasei regarding the ACE-inhibitory peptide LPLP). Eight bioactive peptides were shown to have a positive, substantial connection with Lacticaseibacillus zeae, indicating that Lacticaseibacillus zeae is essential for releasing these bioactive peptides. Two among these peptides exhibited ACE-inhibitory activity, but the majority exhibited antimicrobial properties [59]. Shukla et al. [60] dromedary camel milk’s antidiabetic and ACE inhibitory qualities improved as it was fermented with Lacticaseibacillus paracasei, and the highest levels of these effects were seen in 3 kDa protein fragments as opposed to 10 kDa protein fractions.

The thermophilic bacterium Lactobacillus helveticus, which is a member of the Lactobacillus delbrueckii group, also produces large amounts of lactic acid in milk, is employed as a starter culture in the dairy sector and is particularly popular in the production of cheese because of its excellent proteolytic activity [61]. Isoleucyl-prolyl-proline (IPP) and valyl-prolyl-proline (VPP), two angiotensin-I converting enzyme inhibitory (ACE-I) tripeptides, are produced from the milk-derived casein by the proteolytic processes of Lactobacillus helveticus strains [62]. Furthermore, it has been discovered that some adjunct cultures can generate enzymes that hydrolyze caseins specifically, releasing bioactive peptides in the process. Baptista et al. [63] demonstrated that the production of β-casein peptides, namely the peptide β-casein f(194–209), which is known to have the ability to block the angiotensin-converting enzyme (ACE), was favored when Lactobacillus helveticus LH-B02 was used as an adjunct culture in the production of Prato cheese.

The “kefir” has been the subject of extensive research in recent years. A natural starting culture called kefir grains contains a variety of naturally occurring lactic acid bacteria, acetic acid bacteria, and yeasts in a polysaccharide matrix of semi-hard granules. The ACE-inhibitory and antihypertensive effects of fermented milk generated by Enterococcus faecalis have been determined to be attributed to the antihypertensive peptide LHLPLP [54,64]. In the same context, Cirrincione et al. [65] confirmed that through fermentation, bioactive peptides are produced. According to the findings of another research, κ-casein and β-casein increased the diversity of peptides throughout fermentation and gastrointestinal digestion [66]. Lactic acid bacteria were crucial in hydrolyzing κ-casein, which resulted in the release of biologically active peptides that might enhance the yogurt’s beneficial properties [66]. The possibility of employing probiotic bacteria for the fermentation of cow, camel, goat, and sheep milk to generate bioactive peptides with proteolytic and DPP-IV inhibiting properties was examined by Mudgil et al. [67]. Across different milk types, Lactiplantibacillus pentosus consistently exhibited robust proteolytic activity. Proteolytic patterns were strain-specific and displayed clear milk-type–dependent signatures [67]. These intricate ecosystems can provide unique bioactive peptides from dairy fermented products because microbial diversity has a significant effect on the activity of enzymes [46]. The nature of bioactive peptides generated in the final products is shaped by the inherent characteristics of the food proteins, the specific proteolytic pathways employed, and the peptide-producing genetic traits of the microorganisms [68]. An overview of bioactive peptides occurring after fermentation and enzymatic hydrolysis are provided in Table 1.

Table 1. Peptides from dairy products through fermentation and enzymatic hydrolysis.

Dairy Product	Peptides	Process	Activities	Enzymes/Bacteria	Reference
Skim milk	TPVVVPPF, FFVAPFPGVFGK, YPFPGPIP	Fermentation and enzymatic hydrolysis	ACE-inhibitory (Peptides fraction 95.51% ACE-I bioactivity and IC50 0.01 mg/mL)	Lactobacillus helveticus and Protease	[69]
Buttermilk	VYPFPGPIPN, PFPGPIPN, LHLPLPL, KVLPVPQ, KAVPYPQ	Fermentation and enzymatic hydrolysis	ACE-inhibitory activity after intestinal digestion >60%	LAB, gastrointestinal enzymes	[70]
Buttermilk	VVVPPFLQPEV, KAVPYPQ, VEELKPTPE	Fermentation and enzymatic hydrolysis	Antioxidant (DPPH scavenging activity after intestinal digestion >75%)	LAB, gastrointestinal enzymes	[70]
Skim mik	SLVYPFPGPIH, LLYQEPVLGPVRGPFPIIV, INPSKENLCSTFCKEVVRN, INPSKENLCSTFCKEVVR, KEMPFPKYPVEPF	Fermentation	Antioxidant (DPPH scavenging activity 59.25 ± 1.84%)	Lactiplantibacillus plantarum	[71]
Edam cheese	IPI	Fermentation and enzymatic hydrolysis	DPP-IV-inhibitory IC50 (μmol/L) 3,5	Rennet and starter cultures	[72]
Karish, Domiati, Ras, Gouda, Edam	IPP	Fermentation and enzymatic hydrolysis	ACE-inhibitory activity IC50 (μmol/L) 5	Rennet and/or starter cultures	[72]
Goat milk	LARPKHPINHRGLSPE, NRLNFLK and TTMPLW, PEEIKITVDDKHYQKALNEI, ITVDDKHYQK	Fermentation	ACE-inhibitory activity 52.73% and 65.44%	Limosilactobacillus fermentum and Lacticaseibacillus paracasei	[73]
Goat milk	TQTPVVVPPFLQPEIMGVPKVKE, TLTDVEKL, VLPVPQKAVPQ, REQEELNVVGE, VLPVPQKVVPQ	Fermentation	ACE-inhibitory activity 73.98%	Lactobacillus helveticus	[74]
Goat milk	AFPEHK	Fermentation	ACE-inhibitory activity 25.16  ±  4.849%	Lacticaseibacillus casei	[75]
Milk protein isolate	YPVEPF	Enzymatic hydrolysis	DPP-IV-inhibitory IC50 0.125 (μmol/L)	Trypsin, Pepsin, Corolase PP	[76]

Table 1. Peptides from dairy products through fermentation and enzymatic hydrolysis.

Dairy Product	Peptides	Process	Activities	Enzymes/Bacteria	Reference
Skim milk	TPVVVPPF, FFVAPFPGVFGK, YPFPGPIP	Fermentation and enzymatic hydrolysis	ACE-inhibitory (Peptides fraction 95.51% ACE-I bioactivity and IC50 0.01 mg/mL)	Lactobacillus helveticus and Protease	[69]
Buttermilk	VYPFPGPIPN, PFPGPIPN, LHLPLPL, KVLPVPQ, KAVPYPQ	Fermentation and enzymatic hydrolysis	ACE-inhibitory activity after intestinal digestion >60%	LAB, gastrointestinal enzymes	[70]
Buttermilk	VVVPPFLQPEV, KAVPYPQ, VEELKPTPE	Fermentation and enzymatic hydrolysis	Antioxidant (DPPH scavenging activity after intestinal digestion >75%)	LAB, gastrointestinal enzymes	[70]
Skim mik	SLVYPFPGPIH, LLYQEPVLGPVRGPFPIIV, INPSKENLCSTFCKEVVRN, INPSKENLCSTFCKEVVR, KEMPFPKYPVEPF	Fermentation	Antioxidant (DPPH scavenging activity 59.25 ± 1.84%)	Lactiplantibacillus plantarum	[71]
Edam cheese	IPI	Fermentation and enzymatic hydrolysis	DPP-IV-inhibitory IC50 (μmol/L) 3,5	Rennet and starter cultures	[72]
Karish, Domiati, Ras, Gouda, Edam	IPP	Fermentation and enzymatic hydrolysis	ACE-inhibitory activity IC50 (μmol/L) 5	Rennet and/or starter cultures	[72]
Goat milk	LARPKHPINHRGLSPE, NRLNFLK and TTMPLW, PEEIKITVDDKHYQKALNEI, ITVDDKHYQK	Fermentation	ACE-inhibitory activity 52.73% and 65.44%	Limosilactobacillus fermentum and Lacticaseibacillus paracasei	[73]
Goat milk	TQTPVVVPPFLQPEIMGVPKVKE, TLTDVEKL, VLPVPQKAVPQ, REQEELNVVGE, VLPVPQKVVPQ	Fermentation	ACE-inhibitory activity 73.98%	Lactobacillus helveticus	[74]
Goat milk	AFPEHK	Fermentation	ACE-inhibitory activity 25.16  ±  4.849%	Lacticaseibacillus casei	[75]
Milk protein isolate	YPVEPF	Enzymatic hydrolysis	DPP-IV-inhibitory IC50 0.125 (μmol/L)	Trypsin, Pepsin, Corolase PP	[76]

4. Classification and Functions of Identified Peptides

During the last decade, many studies have focused on the identification and characterization of bioactive peptides originating from milk proteins and dairy products, produced through fermentation or enzymatic hydrolysis. Based on the comprehensive documentation compiled in the present systematic review, more than 3200 bioactive peptides have been reported in the literature over the past decade (2014–2024), exhibiting a diverse range of biological activities.

4.1. Antihypertensive Peptides

Human lives are at risk due to elevated blood pressure, a chronic and severe condition [60]. The ACE (Angiotensin Converting Enzyme) is one of the intricate mechanisms in the human body that regulates blood pressure [77]. It is believed that ACE inhibition is an effective treatment for hypertension [78]. An exopeptidase called ACE (peptidyl peptide hydrolase, EC 3.4.15.1) is essential for controlling blood pressure through the bradykinin and renin-angiotensin pathways. Blood pressure is lowered and an antihypertensive effect is produced by inhibiting ACE [27]. In vitro and in vivo investigations have shown that bioactive peptides generated from different dietary proteins, particularly caseins, block ACE and hence relieve tension [5,6]. In addition to recognized ACE inhibitory peptides, Mihalic cheese is found to contain peptide sequences with P residues at the C-terminal position that are crucial for binding ACE [27]. The antihypertensive peptides HLPLPL and HLPLP can be produced by the dairy Debaryomyces hansenii strains Dh1 and Dh14, which are viable GRAS microorganisms with strain-specific caseinolytic mechanisms. The ACE-inhibitory characteristics of both Debaryomyces hansenii CSHs may be partially or entirely attributed to these two peptides [54]. It is interesting to note that peptides having a Pro residue in both locations, such as VAPFP, DIPNP, VYPFP, FSDIPNP, and GPVRPFP, may be viable candidates to block ACE function in addition to the antihypertensive sequences LHLPLP and HLPLP [54]. The same biopeptide sequences originating from serum amyloid A protein and β-casein, respectively, were also found in donkey milk by Chiozzi et al. [79]. In order to validate the ACE-inhibitory activity of the predicted peptides, Tondo et al. [80], upon testing eleven newly created peptides derived from whey protein hydrolysates, found that only three bioactive peptides (MHI, IAEK, and IPAVF) returned an elevated degree of ACE inhibition, ranging from 63.2 to 72.5% at a dosage of 5 μg/mL.

Kefir digests included eleven biopeptides with ACE-inhibitory potential; the researchers think this high number was brought on by the extensive study of this particular bioactivity in milk peptides [81]. Similarly, in a different study, twelve sequences among the bovine kefir peptides were identified as ACE inhibitors [82]. With three ACE inhibitory peptides, LDAQSAPLR, VLDTDYK, and VGINYWLAHK, found among both Protease M and trypsin hydrolysates, and three peptides DAQSAPLRVY, KGYGGVSLPEW, and DKVGINY, exclusive to Protease M hydrolysates, angiotensin converting enzyme (ACE) inhibition proved to be the most prevalent bioactive function in whey protein hydrolysis products [83]. ACE inhibitory action was demonstrated for the isolated sequences of peptide IAMNPWHHVTPFR from αs2-casein, SPAQTLQWQVLPNAVPAK from κ-casein, and FVVAPFPEVFR from αs2-casein from sheep milk fermented by Lactiplantibacillus plantarum KGL3A [58]. The peptide TKTEEGEFISEGGGVR is one of the discovered peptides for whose bioactivity has previously been described. Four peptides were assigned to the fibrinogen a-chain, one of the precursor protein chains found in this study, to which this fibrinopeptide belongs. Being one of the main constituents of coagulation in the blood, this peptide plays a significant role in hemostasis [84].

Through an extensive and systematic literature review, the results indicated that the majority of the research in the dairy peptides sector focuses on antihypertensive activities, and particularly on ACE-inhibitory peptides. It is noteworthy that of the approximately 3200 peptides recorded, 1237 are antihypertensive biopeptides (1206 ACE-inhibitory peptides). In

Table 2. Protein origin of antihypertensive biopeptides.

Milk Proteins	Number of Antihypertensive Peptides	%
β-casein	675	54.6
αs1-casein	248	20.0
αs2-casein	44	3.6
κ-casein	31	2.5
β-lactoglobulin	39	3.2
α-lactalbumin	18	1.5
Serum albumin	13	1.1
Serum amyloid A protein	5	0.4
Multiple	4	0.3
n.d. *	127	10.3
Caseins	6	0.5
Whey proteins	27	2.2
Total	1237	100.0

* n.d.: Not detected.

the protein origin of antihypertensive peptides is presented. A great number of the antihypertensive peptides are of casein origin, which is probably explained by the fact that casein proteins are abundant in milk and that many studies are focused on dairy products like various cheeses, where the whey is removed. Moreover, as shown in Figure 2, more than 70% of the recorded antihypertensive peptides are of cow milk origin; however, the study of other types of milk, like sheep, camel, goat, buffalo, and donkey milk, has grown over the last decades. References for the tables and figures are provided in Supplementary Materials.

4.2. Antioxidant Peptides

Superoxide anion radicals, hydroxyl radicals, hydrogen peroxide, and nitric oxide free radicals are examples of reactive oxygen species (ROS), which are byproducts of regular cellular metabolism [85]. Although a certain amount of ROS is necessary for physiological functions, a disproportionate amount of those can lead to oxidative stress and harm the human body [86]. Chronic disorders may arise as a consequence of oxidative stress’s harmful effects, including lipid peroxidation, protein cross-linking, and damage to RNA and DNA [85,86]. As unstable by-products of regular cell metabolism, free radicals readily interact with other chemicals and groups throughout the body. The occurrence of conditions including atherosclerosis, diabetes, and cancer is linked to high levels of exposure to free radicals [5,27]. A diet high in antioxidants lowers blood pressure and protects against oxidative stress [27]. Nonetheless, the peptides found in Gruyere have a significant concentration of amino acid residues like Q, P, and L, which are critical for a peptide’s antioxidant function. Additionally, in Erzincan Tulum, there were peptide sequences that contained the hydrophobic and aromatic amino acid residues needed for strong antioxidant action [27].

In kefir digests, the peptides YPEL (from aS1-casein) and VYPFPGPIPN (from β-casein) showed antioxidant qualities that could potentially lessen oxidative stress through digestion [81]. In muscle cells treated with antioxidant peptides, the peptides ALPM, GDLE, VGIN, and AVEGPK (5 mM) decreased cellular oxidation by 34.4% to 53% as compared to the free radical control and had an impact comparable to that of the antioxidant molecule NAC (31.8%). When ALPM (β-LG), GDLE (β-LG), or VGIN (α-LA) (5 mM) were administered to stressed HepG2 cells, the levels of oxidation drastically dropped between 35 and 52.6% [87]. The biopeptide VGIN provided antioxidant protection on both C2C12 and HepG2 cells, but the peptide GDLE (5 mM) strengthened the antioxidant cellular reaction, was bioavailable, and shielded stressed hepatocytes from cellular oxidation [87]. In the study of Jin et al. [66], both bovine yogurt and its simulated yogurt digests were shown to contain the antioxidant peptide QEPVLGPVRGPFPII β-casein f(194–208).

In the present review, a total of 433 antioxidant peptides have been reported from milk and dairy sources, displaying considerable heterogeneity in their protein origins. β-casein is the most prominent precursor, followed by αs1-casein and β-lactoglobulin. Other relevant contributors include κ-casein and αs2-casein, while whey proteins, lactoferrin, α-lactalbumin, serum amyloid A, serum albumin, and other casein fractions are represented in smaller proportions (

Table 3. Protein origin of antioxidant peptides.

Milk Proteins	Number of Antioxidant Peptides	%
β-casein	140	32.3
αs1-casein	87	20.1
β-lactoglobulin	44	10.2
κ-casein	39	9.0
αs2-casein	34	7.9
Whey proteins	23	5.3
n.d. *	18	4.2
Lactoferrin	13	3.0
α-lactalbumin	9	2.1
Serum amyloid A	10	2.3
Multiple	7	1.6
Serum albumin	6	1.4
Caseins	3	0.7
Total	433	100

* n.d.: Not detected.

). The predominance of β-casein and αs1-casein reflects both their high natural abundance and their susceptibility to proteolytic cleavage into peptides capable of mitigating oxidative stress. The distribution of antioxidant peptides by species, presented in Figure 3, indicates that cow’s milk is the principal source of reported sequences.

4.3. Antimicrobial Peptides

Milk and dairy products are rich sources of bioactive peptides originating from various proteins and present antimicrobial properties. Recent studies have identified peptides in kefir, yogurt, cheese, milk, and other dairy products, demonstrating notable inhibitory effects against harmful microorganisms. Kefir digests were shown to include two antimicrobial peptides, casecidin 15 and casecidin 17 YQEPVLGPVRGPFPI (β-casein) and YQEPVLGPVRGPFPIIV (β-casein), respectively, both generated from β-casein and are known to inhibit microbial growth [81]. The results of the peptide analysis of bovine kefir, performed by Ebner et al. [82], concluded that caseicin B, an antimicrobial peptide with the sequence VLNENLLR (αS1-casein 15–22), was present and demonstrated activity against Escherichia (E.) coli DPC6053, with a minimal inhibitory concentration of 0.22 mM. The study of Folliero et al. [88] resulted in the detection of antimicrobial peptides in kashk cheese, which had an antimicrobial effect against Staphylococcus aureus. They identified four immediate precursors and nearly nine full fragments of the already known antimicrobial peptide caseicin C, the αs1-casein fragment (180–193) (SDIPNPIGSENSEK), which is known to be effective against Gram-positive (Gram+) bacteria [88]. In addition to the caseicin C, the researchers also found precursors and fragments of casecidin 15 (YQEPVLGPVRGPFPI) and casecidin 17 (YQEPVLGPVRGPFPIIV), both possessing inhibitory activity against E. coli DPC6053 [88]. Cirrincione et al. studied the fermented donkey milk peptides and identified the sequences DPATQPIVPVHNP, PATQPIVPVHNPV, PATQPIVPVHNPVI, and FDPATQPIVPVHNPV that exhibited 60% similarity with the antimicrobial peptide YPVTQPLAPVHNPIS, and the sequences KVAPFPQPVVPYPQ, SKVAPFPQPVVPYPQ, VAPFPQPVVPYPQ, VAPFPQPVVPYPQR that had also 60% similarity antimicrobial peptide VLPVPQKAVPYPQR from β-casein [65].

The review of the studies identified 292 antimicrobial peptides in milk and dairy products, with αs1-casein emerging as the predominant precursor protein, followed by β-casein and αs2-casein. Smaller, yet notable, contributions arise from β-lactoglobulin, κ-casein, lactoferrin, and α-lactalbumin. A small fraction corresponds to peptides whose precise protein origin was not determined (

Table 4. Protein origin of antimicrobial peptides.

Milk Proteins	Number of Antimicrobial Peptides	%
β-casein	82	28.1
αs1-casein	107	36.6
αs2-casein	37	12.7
β-lactoglobulin	25	8.6
κ-casein	18	6.2
Lactoferrin	9	3.1
α-lactalbumin	3	1.0
n.d. *	11	3.8
Total	292	100

* n.d.: Not detected.

). Species-specific milk origin distribution, depicted in Figure 4, shows that bovine milk remains the primary source of identified antimicrobial peptides in the studies reviewed.

4.4. Immunomodulatory Peptides

Immunomodulatory peptides interact with immune cells, signalling molecules, or receptors to stimulate immune responses. For example, casein-generated immunopeptides, such as αs1-casein and β-casein fragments such as TTMPLW f(209–213) and YQEPVLGPVRGPFPIIV f(208–224) from kefir digests, respectively, promote red blood cell phagocytosis by peritoneal macrophages, cause a marked lymphocyte proliferation, and provide protection against bacterial infection [89]. The effects of these biopeptides may include the enhanced activity of natural killer (NK)or macrophages, the modulation of cytokine production, the maturation progress of immune cells and the alteration in inflammatory responses. The peptides in kefir digests PGPIPN and LYQEPVLGPVRGPFPIIV derived from β-casein were found to possess potential immunomodulatory functions, suggesting a possible involvement in immune response regulation [82]. The immunomodulatory peptide YQEPVLGPVRGPFPII β-casein f(193–209) was found in yogurt and simulated yogurt digests (pancreatic and gastric), while in the same study, the multifunctional (antimicrobial and immunomodulatory) peptide RPKHPIKHQGLPQEVLNENLLRF αs1-casein f(1–23) was detected only in simulated pancreatic digest [66]. A previous study of our team exhibited the presence of immunomodulatory peptides in Tsalafouti cheese, more specifically, the peptide QTPVVVPPF β-casein (94–102), and after bioinformatics analysis, the multifunctional peptide LF (ACE-inhibitory, Immunomodulatory, Anti-inflammatory) with PeptideRanker score 0.9869 [90]. Ki et al. discovered the multifunctional peptides IPP κ-casein (129–131) and VPP β-casein (99–101) (antioxidant, immunomodulatory, and ACE inhibitory) in medium-ripened Gouda cheese extracts [91], claiming that the immunomodulatory peptides produced during Gouda ripening contributed to the change in inflammatory mRNA levels.

In the study of Solieri et al., two multifunctional peptides, including immunomodulatory activity, were found in ripened Parmigiano Reggiano cheese: PGPIPN β-casein (63–68) and YQEPVLGPVRGPFPIIV β-casein (193–209) [92]. In Parmigiano Reggiano, after in vitro simulated digestion, the peptide RPKHPIKHQGLPQEVLNENLLRF αs1-casein f(1–23) was found to possess immunomodulatory and antimicrobial activities [93]. In the same study, the peptide YQEPVLGPVRGPFPIIV mentioned earlier was identified and reported to possess multifunctional activities (immunomodulatory, antithrombotic, antimicrobial and ACE-inhibitory) [93]. Grigorean et al. studied the biopeptides in infant formulas in various forms after 15 min of in vitro digestion and identified ten immunomodulatory peptides HQPHQPLPPTVMFPPQ β-casein (160–175), KVLPVPQ β-casein (184–190), KVLPVPQK β-casein (184–191), LAYFYPEL αs1-casein (157–164), LYQEPVLGPVRGPFPIIV β-casein (207–224), NPWDQ αs2-casein (122–16), QEPVL β-casein (209–213), WMHQPHQPLPPT β-casein (158–169), YQEPVLGPVR β-casein (208–217) and YQEPVLGPVRGPFPIIV β-casein (208–224) [94]. Jiehui et al. studied the immunomodulatory effects of QEPVL and concluded that it possesses significant immunomodulating effects and possible functions of inhibition of the inflammatory responses [95].

Current evidence from the literature highlights a total of 79 immunomodulatory peptides isolated from milk and dairy products. The vast majority originate from β-casein and αs1-casein, while minor sources include αs2-casein, histone H4, serum amyloid A, and GlyCam1 (

Table 5. Protein origin of immunomodulatory peptides.

Milk Protein	Number of Immunomodulatory Peptides	%
β-casein	59	74.7
αs1-casein	15	19.0
αs2-casein	2	2.5
Histone H4	1	1.3
Serum amyloid A	1	1.3
GlyCam1	1	1.3
Total	79	100.0

). The predominance of β-casein–derived peptides likely reflects the high abundance of β-casein in milk and its propensity to release peptides with immunomodulatory activity. Species distribution, shown in Figure 5, indicates that cow’s milk accounts for the largest share of immunomodulatory peptides, followed by buffalo milk and sheep milk. A small proportion corresponds to cases in which the milk source was either not specified or not directly investigated by the researchers because the product studied was a mix of two or more milk types.

4.5. Opioid Peptides

The opioid biopeptides exhibit affinity and interact with opioid receptors in the central and peripheral nervous system in the human body. Through the binding to these receptors, they can modulate the physiological human processes, including pain perception, stress responses, gastrointestinal motility, and mood regulation. Two biopeptides in kefir digests, VYPFPGPIPN (β-casein) and YPVEPF (β-casein), are capable of binding opioid receptors and, thus, may have an impact on food intake and gastrointestinal motility [81]. The biopeptide VYPFPGPIPN was also found in another research where the peptide profile of bovine kefir was analysed [82]. Jin et al. [66] performed simulated gastrointestinal digestion (pancreatic digestion and gastric digestion) and identified 2 opioid peptides, VYPFPGPIPN β-casein f(59–68) present in yoghurt and both digests, and VYPFPGPIPNSL β-casein f(59–70) present only in pancreatic digest. A multifunctional peptide YPVEPF β-casein 114–119 (opioid and DPP-IV-inhibitory) was found in ripened Parmigiano Reggiano cheese [92]. The opioid peptide YPVEPF was also found in Parmigiano Reggiano cheese after in vitro simulated digestion in the research of Castellone et al. [93]. The peptidomic study of Spanish blue cheese (Valdeon) revealed bioactive sequences such as the already known opioid peptides f(60–66) (β-casomorphin 7) and f(114–119) (neocasomorphin YPVEPF) [96]. Qian et al. studied the potential sleep-enhancing effects of bovine milk casein and found that YPVEPF and YFYPEL had a strong sleep-enhancing activity and could significantly prolong the sleep duration [97]. To the best of our knowledge, to date, no studies have established an upper intake level or adverse effects associated with dairy-derived bioactive peptides. Most findings are derived from in vitro experiments, and further clinical trials are required to determine safe and effective dosages for human consumption.

The analysis of existing literature on milk-derived opioid peptides indicates a relatively limited but well-defined dataset, comprising 28 identified sequences. Protein origin analysis demonstrates that β-casein is the predominant precursor, followed by αs1-casein and κ-casein (

Table 6. Protein origin of opioid peptides.

Milk Protein	Number of Opioid Peptides	%
αs1-casein	10	35.7
β-casein	15	53.6
κ-casein	3	10.7
Total	28	100.0

). The structural characteristics and amino acid composition of β-casein likely contribute to its prominence, as this protein readily releases bioactive fragments with affinity for opioid receptors during enzymatic hydrolysis or fermentation. Distribution by species, presented in Figure 6, reveals that bovine milk serves as the primary source of all reported opioid peptides. The detection of opioid sequences in non-bovine milks suggests an underexplored potential for broader diversification of sources. Future research expanding the range of studied species may yield novel opioid peptides with distinctive functional properties.

4.6. Antidiabetic Peptides

When the pancreas lacks the ability to regulate blood sugar levels utilizing its own insulin, it produces insufficient amounts of the hormone, resulting in diabetes, a chronic illness [60]. The prevalence of diabetes has increased significantly, with serious repercussions for life expectancy, health, financial burdens, and susceptibility to other illnesses [67]. There has been much interest in the potential of peptides generated from milk proteins as antidiabetic medicines [98]. Particularly, the inhibition of the metabolic enzyme dipeptidyl peptidase IV (DPP-IV) by different peptides produced from dietary proteins has been studied extensively [99]. A metabolic enzyme called DPP-IV can cleave and deactivate cretins, such as polypeptide YY (PYY), glucagon-like peptide 1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) [100]. By inhibiting DPP-IV, the insulinotropic action of incretins can be maintained for a longer period of time, which can help manage type 2 diabetes [101].

Four possible peptides’ binding characteristics in camel milk were revealed by the in silico study of DPP-IV inhibitory peptides, which also revealed the important binding sites [102]. The authors’ theory that bioactive peptides during camel milk consumption and digestion may mediate the anti-diabetic effects of camel milk was further confirmed by the biological activity of CWP hydrolysates at the molecular and cellular levels [102]. Another study of fermented camel milk by Shukla et al. [60] revealed a peptide including hydroxyl-containing amino acids like Ser, Tyr, Thr, and Phe, as well as a basic amino acid like Arg and Lys, which showed a significant antidiabetic impact. Furthermore, higher antidiabetic activity was linked to the addition of proline to a peptide sequence that had Ala or Met at the c-terminus [60]. Mudgil et al. [67] also examined the antidiabetic activity of fermented milk peptides, where the in silico analysis of the peptides indicated the strong binding affinities of cow, camel, and sheep fermented milk peptides with several DPP-IV crystal structures. Additionally, with binding energies of 9.31, 9.18, and 8.9 kcal/mol, respectively, the probiotic fermented milk peptides RPPPPVAM, CHNLDELKDTR, and VLSLSQPK demonstrated significant binding affinity, indicating their possible function as DPP-IV inhibitors [67].

The findings of Gong et al. indicated that specific bioactive peptides derived from goat’s milk casein hydrolysates reduced insulin resistance and possess antidiabetic activities [103]. Arai et al. [104] demonstrated that tripeptides (IPI, VPN, and VPQ), amino acids (Leu), dipeptides (VP), and tetrapeptides (LPVP), all originated from bovine milk proteins, had an elevated DPP-IV inhibitory function. In the research of Hinnenkamp and Ismail [83], whey protein concentrates containing the distinct peptide sequences LKPTPEGDL and LKGYGGVSLPE with DPP-IV inhibitory activity were yet again produced by protease M hydrolysis. Another research by Arai et al. demonstrated that tripeptides (IPI, VPN, and VPQ), amino acids (Leu), dipeptides (VP), and tetrapeptides (LPVP) had high DPP-IV inhibitory activity [104]. Nongonierma et al. [105] detected five peptides, VPV β-casein (f213–215), VPF β-casein (f86–88), LPVPQ β-casein (f171–175), YPI β-casein (f69–71) and VL motifs that had DPP-IV IC₅₀ values < 100 µM, while of these peptides, VPV β-casein (f213–215) stability to gastric and intestinal digestive enzymes suggests that it may have potential as a bioaccessible antidiabetic agent for humans.

Besides the widely studied DPP-IV inhibitory activity, the antidiabetic activity may also be expressed through α-amylase, α-glucosidase inhibition and lipase inhibition attributed to the bioactive peptides with binding affinity to the sites of these enzymes [106,107]. Su et al. identified the peptide sequences QEPVPD, PVRGL, FQEPVP, DPVRG, FQEPVPDPVR with active binding residues of a-amylase in camel milk protein hydrolysates [17]. Shukla et al. examined the antidiabetic properties of dromedary camel milk fermented with Lacticaseibacillus paracasei M11 and reported that the inhibitory activity of α-amylase, α-glucosidase, and lipase in 3 kDa peptide fractions was rated 80.26%, 61.83%, and 70.45%, respectively [107]. The antidiabetic potential of protein hydrolysates produced by simulated gastrointestinal digestion of camel casein proteins was investigated by Mudgil et al. and described FLWPEYGAL as a potential α-amylase inhibitor peptide [108].

A comprehensive and systematic review of the literature revealed that research on bioactive peptides from dairy products with antidiabetic potential is steadily expanding. In total, 485 antidiabetic peptides have been identified, with a substantial proportion originating from casein proteins and most notably β-casein. Other notable protein sources include β-lactoglobulin, αs1-casein, and a-lactalbumin, with smaller contributions from κ-casein, αs2-casein, whey protein fractions, milk serum albumin, and lactoferrin (

Table 7. Protein origin of antidiabetic peptides.

Milk Protein	Number of Antidiabetic Peptides	%
β-casein	185	38.1
αs1-casein	53	10.9
αs2-casein	20	4.1
κ-casein	24	4.9
β-lactoglobulin	58	12.0
α-lactalbumin	26	5.4
Whey proteins	21	4.3
Others	27	5.6
n.d. *	64	13.2
Milk Serum Albumin	4	0.8
Lactoferrin	3	0.6
Total	485	100.0

* n.d.: Not detected.

). As illustrated in Figure 7, cow’s milk constitutes the principal source of antidiabetic peptides of reported sequences. While cow’s milk remains the dominant focus, there is an observable increasing trend in the investigation of alternative milk sources, reflecting a growing interest in their potential for yielding novel antidiabetic peptides.

5. Novel Bioactive Peptides Discovered in the Last Decade

Recent studies have identified novel peptides with antioxidant, DPP-IV–inhibitory, and ACE-inhibitory activities (Table 7), many of which show promising effects in vitro and in cell-based assays. These findings contribute to a growing body of research focused on exploring the functional potential of peptides derived from various protein sources, underscoring their relevance for future therapeutic and nutritional applications.

Although β-LG’s peptides ALPM and AVEGPK have not been identified as antioxidants before, they share a common trait with other antioxidant peptides: hydrophobic AA at the N or C terminus. In C2C12, both peptides (5 mM) inhibited free radicals. In HepG2 cells, ALPM also had an antioxidant effect [87]. Arai et al., by using an array peptide platform, detected 10 novel DPP-IV inhibitory peptides (LPV, IPT, PPL, PPQ, APL, PPT, APF, PPF, HPI, and APS) [104]. Three novel antioxidant peptides (PKYPVEPF, LEASPEVI, and YPFPGPIHNS) demonstrated noteworthy antioxidant activities in vitro chemical assays performed by Guo et al. [85]. More precisely, they demonstrated a significant cytoprotective effect on HepG2 cells when exposed to H₂O₂-induced oxidative stress, boosting cell survival. Four novel ACEI peptides (YPFPGPIH, LKNWGEGW, RELEEIR, and HPHPHLS) were explored, and exhibited the lowest IC₅₀ value (highest bioactivity) of 109.5, 77.7, 196.6, and 64.30 μM, respectively [53]. Two novel ACE-inhibitory peptides, namely REWFTFLK and MPFLKSPIVPF, were successfully extracted, characterized, identified, and validated from donkey milk [79]. In the same study, two novel endogenous antioxidant peptides, EWFTFLKEAGQGAKDMWR and GQGAKDMWR, were isolated, characterized, identified and validated from donkey milk serum amyloid A protein [79].

Gong et al. [103] identified 4 novel antidiabetic peptides from goat milk caseins that ameliorated insulin resistance: SDIPNPIGSE (αs1-casein, f195–204), NPWDQVKR (αs2-casein, f123–130), SLSSSEESITH (β-casein, f30–40), and QEPVLGPVRGPFP (β-casein, f207–219). Nine unique dipeptidyl peptidase IV (DPP-IV) inhibitory peptides (FQLGASPY, FLQY, ILDKEGIDY, ILELA, SPVVPF, LQALHQGQIV, LPVP, MPVQA and LLQLEAIR) were identified in camel milk proteins hydrolysed with trypsin [101]. Four novel bioactive peptides were screened and identified by Zhang et al. [52] present peptides in buffalo milk cheese, including two antioxidant peptides, AYF and YPFPGPIPK, and two ACE inhibitory peptides, LRF and APFPEVFGK. Mudgil et al. examined the binding and docking of potential ACE inhibitory peptides, suggesting 4 novel sequences CLSPLQFR, TLMPQWW, CLSPLQMR [109].

Table 8. Novel bioactive dairy peptides identified during 2014–2024.

Peptide Sequence	Protein Origin	Bioactivity	Reference
LPV	β-casein	DPP-IV inhibitory	[104]
IPT	κ-casein	DPP-IV inhibitory	[104]
PPL	β-casein	DPP-IV inhibitory	[104]
PPQ	β-casein	DPP-IV inhibitory	[104]
APL	β-lactoglobulin	DPP-IV inhibitory	[104]
PPT	β-casein	DPP-IV inhibitory	[104]
APF	αs1-casein	DPP-IV inhibitory	[104]
PPF	β-casein	DPP-IV inhibitory	[104]
HPI	αs1-casein	DPP-IV inhibitory	[104]
APS	αs1-casein	DPP-IV inhibitory	[104]
ALPM	β-lactoglobulin	Antioxidant	[87]
AVEGPK	β-lactoglobulin	Antioxidant	[87]
PKYPVEPF	Whey protein	Antioxidant	[85]
LEASPEVI	Whey protein	Antioxidant	[85]
YPFPGPIHNS	Whey protein	Antioxidant	[85]
YPFPGPIH	β-casein	ACE-inhibitory	[53]
LKNWGEGW	β-casein	ACE-inhibitory	[53]
RELEEIR	β-casein	ACE-inhibitory	[53]
HPHPHLS	β-casein	ACE-inhibitory	[53]
REWFTFLK	Serum amyloid A protein	ACE-inhibitory	[79]
MPFLKSPIVPF	β-casein	ACE-inhibitory	[79]
EWFTFLKEAGQGAKDMWR	Serum amyloid A protein	Antioxidant	[79]
GQGAKDMWR	Serum amyloid A protein	Antioxidant	[79]
SDIPNPIGSE	αs1-casein	Antidiabetic	[103]
NPWDQVKR	αs2-casein	Antidiabetic	[103]
SLSSSEESITH	β-casein	Antidiabetic	[103]
QEPVLGPVRGPFP	β-casein	Antidiabetic	[103]
FLQY	αs2-casein	Antidiabetic	[101]
FQLGASPY	αs1-casein	Antidiabetic	[101]
MPVQA	β-casein	Antidiabetic	[101]
ILDKEGIDY	α-lactalbumin	Antidiabetic	[101]
ILELA	αs1-casein	Antidiabetic	[101]
LLQLEAIR	αs1-casein	Antidiabetic	[101]
LPVP	β-casein	Antidiabetic	[101]
LQALHQGQIV	αs2-casein	Antidiabetic	[101]
SPVVPF	β-casein	Antidiabetic	[101]
AYF	αs2-casein	Antioxidant	[52]
YPFPGPIPK	β-casein	Antioxidant	[52]
LRF	αS1-casein	ACE-inhibitory	[52]
APFPEVFGK	αS1-casein	ACE-inhibitory	[52]
CLSPLQFR	β-casein	ACE-inhibitory	[109]
CLSPLQMR	α-lactalbumin	ACE-inhibitory	[109]
TLMPQWW	αs1-casein	ACE-inhibitory	[109]
SHSPLAGFR	Not specified *	ACE-inhibitory	[109]
SLVYPFPGPI	β-casein	ACE-inhibitory	[110]
DMPIQAFLLYQEPVLGPVR	β-casein	Anti-inflammatory	[111]
VLSELPEP	Whey protein hydrolysate	ACE-inhibitory	[112]
LEQVLPRD	Whey protein hydrolysate	ACE-inhibitory	[112]
Asn-Leu-Glu-Ile-Ile-Leu-Arg	β-lactoglobulin	DPP-IV inhibitory	[113]
Thr-Gln-Met-Val-Asp-Glu-Glu-Ile-Met-Glu-Lys-Phe-Arg	β-lactoglobulin	DPP-IV inhibitory	[113]
LDQWLCEKL	a-lactalbumin	DPP-IV inhibitory	[114]
SCQDQPTTLAR	Not specified *	Antioxidant	[115]
TIDMESTEVFTKK	Not specified *	Antioxidant	[115]
TIDMESTEVFTKK	Not specified *	Antioxidant	[115]
LVYPFPGPIP	β-casein	ACE-inhibitory	[116]
YPQRDMPIQ	β-casein	ACE-inhibitory	[116]
FVVTPK	Not specified *	Antimicrobial	[43]
RGLVPL	Not specified*	Antimicrobial	[43]
ELLPDMPLNQ	Not specified *	Antimicrobial	[43]
APGPLVVPPVGPPPP	Not specified *	Antimicrobial	[43]
PLPASGLL	Not specified *	Antimicrobial	[43]
VMVSGVAGNPGA	Not specified *	Antimicrobial	[43]
HPPGSGLL	Not specified *	Antimicrobial	[43]
PAGNFLP	Whey protein hydrolysate	ACE-inhibitory	[117]
FCCLGPVPP	Whey protein hydrolysate	ACE-inhibitory	[117]
PAGNFLMNGLMHR	Whey protein hydrolysate	ACE-inhibitory	[117]
PAVACCLPPLPCHM	Whey protein hydrolysate	ACE-inhibitory	[117]
LLILTC	αs1-casein	Antioxidant	[118]
AVALARPK	αs1-casein	Antioxidant	[118]
YPLR	Not specified *	Antioxidant	[118]
LSSHPYLEQLYR	αs1-casein	Antioxidant	[118]
TQDK	Not specified *	Antioxidant	[118]
NEPTE	αs1-casein	Antioxidant	[118]
VSSTTEQK	αs1-casein	Antioxidant	[118]
LAVPIN	κ-casein	Antioxidant	[118]
KPVAIR	κ-casein	Antioxidant	[118]
LDCIRKAYGNI	Lactoferrin	Antimicrobial	[119]
KCFQWQRNMRKVR	Lactoferrin	Antimicrobial	[119]
AIGPVADLHI	κ-casein	ACE-inhibitory	[120]
NTVPAKSCQAQPTTM	κ-casein	Antioxidant	[121]
EDELQDKIHPF	β-casein	Antioxidant	[121]
QGPIVLNPWDQVKR	αS2-casein	Antioxidant	[121]
LQPE	β-casein	Cholesterol-lowering	[122]
VLPVPQ	β-casein	Cholesterol-lowering	[122]
VAPFPE	αs1-casein	Cholesterol-lowering	[122]
APSFSDIPNPIGSEMKETTMPLW	Not specified *	Cholesterol esterase inhibitor	[123]
YLEELHRLNK	αs1-casein	Anti-inflammatory	[60]
YLQELYPHSSLKVRPILK	αs1-casein	Anti-inflammatory	[60]
WPMLQPKVM	Not specified *	Cholesterol esterase inhibitor	[124]
CLSPLQMR	Not specified *	Cholesterol esterase inhibitor	[124]
MYQQWKFL	Not specified *	Cholesterol esterase inhibitor	[124]
CLSPLQFR	Not specified *	Cholesterol esterase inhibitor	[124]
ILDKVGINY	α-lactalbumin	DPP-IV inhibitory	[125]
ELKDLKGY	α-lactalbumin	DPP-IV inhibitory	[125]
YPFPGPIP	β-casein	Antioxidant	[126]
YPFVEP	β-casein	Antioxidant	[126]
YGFL	β-casein	Antioxidant	[126]
YPW	β-hemoglobin	Antioxidant	[126]
QEPVPDPVRGL	β-casein	DPP-IV inhibitory	[17]
YPELF	αs1-casein	Antioxidant	[127]
FPQ,	αs2-casein	ACE-inhibitory	[36]
AVPQ	β-casein	ACE-inhibitory	[36]
NVPQ	αs1-casein	ACE-inhibitory	[36]
PAGNFLP,	Not specified *	Pancreatic lipase inhibitor	[128]
MLPLMLPFTMGY,	Not specified *	Pancreatic lipase inhibitor	[128]
LRFPL	Not specified *	Pancreatic lipase inhibitor	[128]
FCCLGPVPP	Not specified *	Cholesterol esterase inhibitor	[128]
MHI	β-lactoglobulin	ACE-inhibitory	[80]
IAEK	β-lactoglobulin	ACE-inhibitory	[80]

* Not specified: Protein origin not specified by the authors.

summarizes all the novel bioactive peptides identified in the literature during the decade 2014–2024.

6. Conclusions

Over the last decade, research into dairy-derived bioactive peptides has revealed their diverse physiological functions and considerable potential as natural agents for health promotion. This systematic review of 192 studies (2014–2024) documented over 3200 dairy-derived bioactive peptides, with antihypertensive sequences, particularly ACE inhibitors, representing the largest group (n = 1237). β-casein was confirmed as the principal precursor across bioactivities, followed by αs1-casein, β-lactoglobulin, and α-lactalbumin, emphasizing caseins as dominant contributors. While enzymatic hydrolysis and fermentation remain the predominant strategies for generating bioactive peptides, other emerging approaches, including high-pressure processing, ultrasound, microwave-assisted hydrolysis, and chemical modification, have been proposed to enhance protein breakdown and peptide release. These methods are still relatively underexplored in dairy matrices but may provide new opportunities for improving yield, bioactivity, and scalability. The peptide profiles vary according to milk type, mostly originating from bovine milk; however, goat, sheep, camel, buffalo, and donkey milk are also studied in terms of bioactive peptides. Technological advances in proteomics and bioinformatics have enabled the identification of potent new sequences, although research remains heavily skewed toward bovine milk. To fully harness their potential in functional foods and nutraceuticals, future studies should emphasize in vivo validation, bioavailability assessment after gastrointestinal digestion, and the exploration of synergistic effects within complex food systems, thereby translating laboratory findings into safe, effective, and consumer-acceptable health solutions.