In vitro digestibility of goat milk and kefir with a new standardised static digestion method (INFOGEST cost action) and bioactivities of the resultant peptides

Protein-added kefir: biochemical changes in in vitro digestion stages

BACKGROUND

While yogurt is the leading fermented milk product, kefir is at the top of the beverage scale. Milk proteins, on the other hand, show specific functions that positively affect healthy nutrition due to the bioactive components, that they provide the necessary amino acids for growth and development.

RESULTS

In our study, kefir, a functional product enriched with whey proteins, casein and skimmed milk powder, which are the natural components of milk, was produced. Added-protein kefir samples were applied the in vitro digestion protocol, static method. In order to observe different protein behaviors, samples were taken pre-digestion, at 120th minute and at 240th minute of digestion protocol. ACE and Antioxidant capacity determination analyzes were carried out. While ACE inhibition values were in the range of 78.63-90.30% pre-digestion, they changed in the range of 86.97-96.38% after gastrointestinal digestion. It was determined that the ACE inhibition values of the control sample remained at the lowest level at all stages of digestion and that the difference between all of samples was significant (P < 0.05). Antioxidant activity value ranging from 0.3615-0.5512 meq Ascorbic acid/μg before digestion was determined as 1.3796-1.9313 meq Ascorbic acid/μg after gastrointestinal digestion (P < 0.05).

CONCLUSION

Kefir samples containing whey protein stand out with their high potential in terms of both antioxidant activity capacity and ACE inhibition activity at all stages of digestion. Considering their therapeutic effects in fermented products, it is thought that whey proteins among milk proteins will be important alternative sources to enrich the protein content in kefir production. © 2024 Society of Chemical Industry.

Sweet tea extract encapsulated by different wall material combinations with improved physicochemical properties and bioactivity stability

Aim: To prepare sweet tea extract microcapsules (STEMs) via a spray-drying by applying different wall material formulations with maltodextrin (MD), inulin (IN), and gum arabic (GA). Methods: The microcapsules were characterised by yield, encapsulation efficiency (EE), particle size, sensory evaluation, morphology, attenuated total reflectance-Fourier transform infra-red spectroscopy and in vitro digestion studies. Results: The encapsulation improved the physicochemical properties and bioactivity stability of sweet tea extract (STE). MD5IN5 had the highest yield (56.33 ± 0.06% w/w) and the best EE (e.g. 88.84 ± 0.36% w/w of total flavonoids). MD9GA1 obtained the smallest particle size (642.13 ± 4.12 nm). MD9GA1 exhibited the highest retention of bioactive components, inhibition of α-glucosidase (96.85 ± 0.55%), α-amylase (57.58 ± 0.99%), angiotensin-converting enzyme (56.88 ± 2.20%), and the best antioxidant activity during in vitro gastrointestinal digestion. Conclusion: The encapsulation of STE can be an appropriate way for the valorisation of STE with improved properties.

Application of In Vitro Digestion Models in the Evaluation of Dietary Supplements

Nowadays, dietary supplements are a permanent part of our diet. Using various simulated in vitro digestive models, the bioavailability of dietary supplement ingredients has also been investigated. In most cases, static models are used instead of dynamic ones. This article focuses on the division of applications of in vitro methods, such as assessing the quality of dietary supplements (in chemical and pharmaceutical form), the impact of diet on the assessment of the bioavailability of product ingredients, the impact of supplement ingredients on the state of intestinal microflora, and the development of new products using various encapsulation methods. The review included publications from 2000 to 2024 showing the use of in vitro methods in dietary supplements containing polysaccharides, proteins, elements, vitamins, and bioactive substances, as well as probiotic and prebiotic products. The impact of components in dietary supplements on the human digestive tract and their degree of bioaccessibility were determined through the use of in vitro methods. The application of in vitro methods has also become an effective tool for designing new forms of dietary supplements in order to increase the availability and durability of labile ingredients in these products.

Solubility, (micro)structure, and in vitro digestion of pea protein dispersions as affected by high pressure homogenization and environmental conditions

In this work, dispersions were prepared with commercial pea protein isolate (PPI) and subjected to different (i) high pressure homogenization (HPH) intensities (0 - 200 MPa) (room temperature, pH 7) or (ii) environmental conditions (60 °C, pH 7 or pH 12) to generate dispersions with distinct protein molecular and microstructural characteristics, impacting protein solubility. Besides, protein digestion was analyzed following the static INFOGEST in vitro digestion protocol. Generally, increasing pressure of the homogenization treatment was linked with decreasing particle sizes and enhanced protein digestion. More specifically, the dispersion that did not undergo HPH (0 MPa) as well as the dispersion treated at 60 °C, pH 7, had highly similar microstructures, consisting of large irregular particles (10 - 500 µm) with shell-like structures, and exhibited low solubility (around 15 % and 28 %, respectively), which resulted in limited proteolysis (35 % and 42 %, respectively). In contrast, the dispersion subjected to HPH at 100 MPa and the dispersion treated at 60 °C, pH 12 also had similar microstructures with small and homogeneous particles (<1 µm), and exhibited relatively good solubility (54 % and 31 %, respectively), which led to enhanced protein digestion levels (87 % and 74 %, respectively). This study highlights the potential of food processing on macronutrient (micro)structure and further gastrointestinal stability and functionality.

Structure and in vitro digestion characteristics of skim goat milk protein during processing: effects of fat separation

BACKGROUND

Although nonfat milk has been used worldwide in the industrial dairy process, little is known about the effects of fat separation during the manufacturing process on skim milk's structural and digestive properties. This study investigated the effects of the manufacturing process on the structure and in vitro digestion properties of skim goat milk, particularly emphasizing fat separation.

RESULTS

Changes in the surface charge and hydrophobicity of milk proteins caused by fat separation resulted in oxidation and aggregation in the subsequent homogenization, heat and spray-drying processing, which affected its digestibility. Compared with separation by dish separator (DS), skim milk after tubular centrifugal separation (CS) showed a higher initial and final digestibility. The CS samples also had a lower surface hydrophobicity level and higher free sulfhydryl content, ζ-potential, and average particle size (P < 0.05). Goat milk protein after CS was more readily oxidized and aggregated during the subsequent homogenization and heat treatment, as evidenced by the higher carbonyl content and particle size. Centrifugal separation also converted more β-sheets to α-helices, thus promoting the aggregation of oxidized skim milk protein.

CONCLUSION

The skim milk after CS and DS demonstrated different structural and digestive properties. Skim goat milk products after CS were more susceptible to oxidant-induced protein structural changes, resulting in higher protein digestibility. These findings provide insights into the mechanism involved in the control of gastric digestion of skim milk during manufacturing process. © 2023 Society of Chemical Industry.

Impact of thermal treatments and simulated gastrointestinal digestion on the α-amylase inhibitory activity of different legumes

Legumes are excellent sources of proteins that can be hydrolysed to generate antidiabetic peptides, which inhibit carbohydrate digestive enzymes. The degree of protein hydrolysis depends on the thermal treatment applied and how it impacts protein denaturation and thus accessibility to enzymes. In this study, α-amylase inhibitory activities of cooked (conventional, pressure, and microwave cooking) and digested (simulated gastrointestinal digestion, GID) green pea, chickpea, and navy beans were evaluated, together with the impact of thermal treatments on peptide profiles after GID. All peptides extracts inhibited α-amylase after cooking and GID, and the peptide fraction <3 kDa was responsible for main activity. In green peas and navy beans, microwave cooking showed the highest impact whereas none thermal treatment highlighted in chickpeas. The peptidomics analysis of the fractions <3 kDa identified a total of 205 peptides, 43 of which were found to be potentially bioactive according to in silico analysis. Also quantitative results evidenced differences in the peptide profile between the type of legume and thermal treatment.

Current trends and perspectives on bioaccessibility and bioavailability of food bioactive peptides: in vitro and ex vivo studies

The bioaccessibility and bioavailability of food-derived bioactive compounds are important issues when assessing their in vivo physiological health-promoting effects. Food components such as proteins and peptides are exposed to different proteases and peptidases during gastrointestinal digestion and absorption. Different in vitro approaches have therefore been developed to evaluate the bioaccessibility and stability of bioactive peptides. The static simulated gastrointestinal digestion model (SGD) was widely reported to assess the bioaccessibility of bioactive peptides. On the other hand, although the dynamic SGD model may better simulate human digestion, it has rarely been explored in bioaccessibility studies of food bioactive peptides due to its high cost and lack of standardization. For bioavailability studies, the Caco-2 cell monolayer model has been used extensively for the assessment of food bioactive peptides. In fact, very few reports using alternative methods for determining transepithelial transport of bioactive peptides have been employed. In this sense, ex vivo tissue-based models such as the Ussing chamber and the everted sac gut have been used. Current evidence supports the fact that using SGD with cell-based models for evaluating the bioaccessibility, absorption, and bioavailability of food-derived bioactive peptides, is the most commonly used approach. Nevertheless, SGD with ex vivo tissue-based models such as the everted sac, remains to be further explored because it seems to be the model that better mimics the physiological process - it is also fast and inexpensive, and several compounds may be tested simultaneously. In the present review, we discuss information available on the different in vitro approaches for the determination of bioaccessibility and bioavailability of food-derived bioactive peptides with special emphasis on ex vivo tissue-based models such as the everted sac and the Ussing chamber models. © 2022 Society of Chemical Industry.

Bioaccessibility of Phenolic Compounds and Antioxidant Properties of Goat-Milk Powder Fortified with Grape-Pomace-Seed Extract after In Vitro Gastrointestinal Digestion

This study deals with the evaluation of the bioaccessibility and antioxidant properties of phenolic compounds from heat-treated skim goat-milk powder fortified with grape-pomace-seed extract, after in vitro gastrointestinal digestion. Ultra-high performance liquid chromatography coupled to diode array detection and mass spectrometry (UHPLC-DAD MS/MS) analysis confirmed the abundant presence of phenolic acids and flavan-3-ols in the grape-pomace-seed extract (SE) and heat-treated skim goat-milk/seed-extract powder (TME). After in vitro digestion of TME powder and recovery of total quantified phenolics, flavan-3-ols and phenolic acids were 18.11%, 24.54%, and 1.17%, respectively. Low recovery of grape-pomace-seed phenolics indicated strong milk protein-phenolic interactions. Electrophoretic analysis of a soluble fraction of digested heat-treated skim goat milk (TM) and TME samples showed the absence of bands originating from milk proteins, indicating their hydrolysis during in vitro gastrointestinal digestion. The digested TME sample had better antioxidant properties in comparison to the digested TM sample (except for the ferrous ion-chelating capacity, FCC), due to the presence of bioaccessible phenolics. Taking into account the contribution of the digestive cocktail, digested TME sample had lower values of total phenolic content (TPC), in vitro phosphomolybdenum reducing capacity (TAC) and ferric reducing power (FRP), compared to the undigested TME sample. These results could be attributed to low recovery of phenolic compounds. TME powder could be a good carrier of phenolics to the colon; thus, TME powder could be a promising ingredient in the formulation of functional food.

Resin glycosides in aerial parts of Ipomoea batatas are potent lipase inhibitors: potential upcycling of sweet potato by-products to combat obesity

Sweet potato (Ipomoea batatas) is a staple food crop that is cultivated globally. While the tubers are widely utilised in the food industry, 95-98% of sweet potato leaves (SPL) are disposed during harvesting. Hence, there is great potential to convert SPL into high-value food products through various processing techniques. In this regard, different varieties of Ipomoea batatas (Blackie, Blackheart, and Margarita) that were grown in Singapore were tested for their pancreatic lipase (PL) inhibitory activity using a high-throughput screening assay. Among them, the Margarita variety showed the highest PL inhibitory activity with an Orlistat Equivalent (OE) value of 3.83 ± 0.36 × 10^-4. The kinetic study of the Margarita extract revealed a non-competitive inhibition mechanism. Overall, a series of resin glycosides (RG), responsible for the PL inhibitory activity, was characterised in Margarita Ipomoea batatas. To evaluate the effectiveness of RG under gastrointestinal conditions with high-fat food, in vitro digestion with salad dressing was performed. The in vitro digestion model showed that the consumption of RG with salad dressing was effective in delaying enzymatic fat digestion in a dose-dependent manner. The findings strongly suggested that the aerial parts of Ipomoea batatas have great potential to be upcycled into functional food to combat obesity.

Two Liberibacter Proteins Combine to Suppress Critical Innate Immune Defenses in Citrus

We adopted a systems-based approach to determine the role of two Candidatus Liberibacter asiaticus (CLas) proteins, LasP ₂₃₅ and Effector 3, in Huanglongbing (HLB) pathogenesis. While a published work suggests the involvement of these CLas proteins HLB pathogenesis, the exact structure-based mechanism of their action has not been elucidated. We conducted the following experiments to determine the structure-based mechanisms of action. First, we immunoprecipitated the interacting citrus protein partners of LasP ₂₃₅ and Effector 3 from the healthy and CLas-infected Hamlin extracts and identified them by Liquid Chromatography with tandem mass spectrometry (LC-MS/MS). Second, we performed a split green fluorescent protein (GFP) assay in tobacco to validate that the interactions observed in vitro are also retained in planta. The notable in planta citrus targets of LasP ₂₃₅ and Effector 3 include citrus innate immune proteins. Third, in vitro and in planta studies were performed to show that LasP ₂₃₅ and Effector 3 interact with and inhibit the functions of multiple citrus proteins belonging to the innate immune pathways. These inhibitory interactions led to a high level of reactive oxygen species, blocking of bactericidal lipid transfer protein (LTP), and induction of premature programed cell death (PCD), all of which are beneficial to CLas lifecycle and HLB pathogenesis. Finally, we performed molecular dynamics simulations to visualize the interactions of LasP ₂₃₅ and Effector 3, respectively, with LTP and Kunitz protease inhibitor. This led to the design of an LTP mimic, which sequestered and blocked LasP ₂₃₅ and rescued the bactericidal activity of LTP thereby proving that LasP ₂₃₅ , indeed, participates in HLB pathogenesis.

Comparative effects of high pressure processing and heat treatment on in vitro digestibility of pea protein and starch

The effects of high-pressure processing (HPP) and heat treatment on the digestibility of protein and starch in pea protein concentrate (PPC) were investigated. Samples of PPC with 5% (5 P) and 15% (15 P) protein were treated by HPP (600 MPa/5 °C/4 min) or heat (95 °C/15 min) and their in vitro static and dynamic digestibility were compared to untreated controls. HPP-treated PPC underwent a greater degree of proteolysis and showed different peptide patterns after static gastric digestion compared to untreated and heat-treated PPC. Differences in protein digestibility among treatments during dynamic digestion were only significant (p < 0.05) during the first 20 min of jejunal, ileal, and total digestion for 5 P, and during the first 60 min of ileal digestion for 15 P. Neither static nor dynamic starch digestibility were dependent on treatment. HPP did not reduce trypsin inhibitor activity, whereas heat treatment reduced it by ~70%. HPP-induced structural modifications of proteins and starch did not affect their overall in vitro digestibility but enhanced gastric proteolysis.

Advances in static in vitro digestion models after the COST action Infogest consensus protocol

In vitro digestion models are essential to predictively evaluate the bioaccessibility and bioactivity of food molecules or natural products. Dynamic models better simulate the gastrointestinal conditions as they reproduce similar physiological environments. Despite this, static methods, also known as biochemical methods, represent a simple and useful approach for the study of different types of molecules, with a broad applicability in the nutritional, pharmaceutical, and toxicological fields. In addition, static models can be validated, avoiding the disadvantage of a difficult reproducibility of dynamic in vitro systems and inter-individual variations of in vivo experiments. A crucial point in the standardization of static models was the COST Action Infogest in 2014, which elaborated an international consensus static digestion method to harmonize experimental conditions and has general guidelines, thus allowing the comparison of studies and data. The aim of our review is to underline the impact of the Infogest consensus method and the development and evolution of in vitro static methods in the following years, with a focus on food applications.

In Vitro Bioaccessibility Protocol for Chlorophylls

The daily ingestion of chlorophylls has been estimated at 50 g, but the knowledge about their bioaccessibility is limited. Different in vitro models have been utilized to estimate their potential bioavailability, but among other factors, the diversity of structures, chemical properties, and lability of chlorophylls hamper the investigations. By the first time, three extreme food matrices, one rich in fiber (vegetable puree), one rich in fat (virgin olive oil), and one liquid (fruit juice), have been assayed for chlorophyll bioaccessibility, controlling crucial variables. Chlorophyll polarity and food matrix were the determining factors, but surprisingly, chlorophyll bioaccessibility was affected during the application of the in vitro standardized protocol. Therefore, the present research has identified the reactions that can be biased during the estimation of chlorophyll bioaccessibility, defining a specific protocol in the function of chlorophyll structures.

Skimmed Goat's Milk Powder Enriched with Grape Pomace Seed Extract: Phenolics and Protein Characterization and Antioxidant Properties

The aim of this research was phenolics and protein characterization and antioxidant properties evaluation of skimmed thermally treated goat's milk powder enriched with different concentration of grape pomace seed extract (SE). The dominant phenolics in SE were phenolic acids, flavan-3-ols and procyanidins. Different electrophoretic techniques together with UHPLC-MS/MS analysis revealed the presence of phenolics-protein interactions in the samples, mainly procyanidins with whey protein/caseins complexes. Addition of SE into thermally treated goat's milk significantly improved antioxidant properties of goat's milk such as TAC, FRP, DPPH^• and ABTS^•+ scavenging activity. Gallic acid, catechin, and procyanidins mostly contributed to these activities. The schematic representation of phenolics-casein micelles interactions in thermally treated goat's milk enriched with SE was given. The addition of SE into thermally treated goat's milk can be a promising strategy in food waste recovery and to enhance the beneficial health effects of goat's milk-based functional foods.

Probiotic survival, biological functionality and untargeted metabolomics of the bioaccessible compounds in fermented camel and bovine milk after in vitro digestion

This study investigated probiotic survival and biological functionality of the bioaccessible fraction of fermented camel milk (FCM) and fermented bovine milk (FBM) after in vitro digestion. Furthermore, untargeted metabolomic analysis was performed to identify the bioaccessible compounds in FCM and FBM, which were produced using starter bacteria (SC), a potential probiotic (Pro) or a combination thereof (SC + Pro), followed by storage (21 d). Survival of Pro and SC + Pro bacteria in FCM was higher than in FBM throughout in vitro digestion. The antioxidant activities of the bioaccessible fractions differed slightly between culture types, whereas the antiproliferative activity of SC was highest, followed by SC + Pro. Antiproliferative activity of the bioaccessible fractions of FCM was greater than for FBM. Untargeted metabolomics of FCM demonstrated discrimination between cultures and from FBM. FCM produced with SC + Pro and Pro had closer clustering than with SC. The bioaccessible fraction of FCM exhibited higher biological functionality compared to FBM.

Invited review: Characterization of new probiotics from dairy and nondairy products-Insights into acid tolerance, bile metabolism and tolerance, and adhesion capability

The selection of potential probiotic strains that possess the physiological capacity of performing successfully in the gastrointestinal tract (GIT) is a critical challenge. Probiotic microorganisms must tolerate the deleterious effects of various stresses to survive passage and function in the human GIT. Adhesion to the intestinal mucosa is also an important aspect. Recently, numerous studies have been performed concerning the selection and evaluation of novel probiotic microorganisms, mainly probiotic bacteria isolated from dairy and nondairy products. Therefore, it would be crucial to critically review the assessment methods employed to select the potential probiotics. This article aims to review and discuss the recent approaches, methods used for the selection, and outcomes of the evaluation of novel probiotic strains with the main purpose of supporting future probiotic microbial assessment studies. The findings and approaches used for assessing acid tolerance, bile metabolism and tolerance, and adhesion capability are the focus of this review. In addition, probiotic bile deconjugation and bile salt hydrolysis are explored. The selection of a new probiotic strain has mainly been based on the in vitro tolerance of physiologically related stresses including low pH and bile, to ensure that the potential probiotic microorganism can survive the harsh conditions of the GIT. However, the varied experimental conditions used in these studies (different types of media, bile, pH, and incubation time) hamper the comparison of the results of these investigations. Therefore, standardization of experimental conditions for characterizing and selecting probiotics is warranted.

Improved estimation of in vitro protein digestibility of different foods using size exclusion chromatography

While the harmonized INFOGEST model provides a physiologically relevant platform for simulated digestion, it needs to be combined with adequate analytical methods to enable quantification and comparison of protein digestibility in different food matrices. We have shown that size exclusion chromatography (SEC) can be used to estimate the proportion of small peptides potentially available for uptake. Combined with determination of total dissolved protein, the % of small peptides per total protein was calculated as a physiologically relevant estimate of protein digestibility (D_SEC). Values for D_SEC differed for casein (87.6%), chicken mince (72.6%), heated pea protein concentrate (67.8%), bread (63%), beef entrecote (57.7%) and pea protein concentrate (57.8%). In contrast to existing methods (TCA soluble protein, free NH₂-groups), the proposed SEC based method gives separate insight into the two fundamental processes during protein digestion (solubilization and break-down), while maintaining the ability to rank digestibility of very different food proteins.

Gastric Digestion of Milk Proteins in Adult and Elderly: Effect of High-Pressure Processing

Reduced physiological capability of the human gastrointestinal tract with increasing age has recently attracted considerable attention to the potential of novel technologies to modify food digestion. Thus, the aim of this study was to investigate gastric digestion of milk proteins after application of high-pressure processing (HPP) at 400 MPa 15 min, 600 MPa 5 min and 600 MPa 15 min using two static in vitro models of adults (INFOGEST) and the elderly in comparison to a fresh untreated raw milk. Peptides distribution classified based on the number of amino acids (AA) (<10, 11-15, 16-20, 21-30, >30 AA) were investigated after 0, 5, 10 and 30 min of digestion using LC-MS and multivariate data analysis. Our results show significantly less efficient protein digestion of all investigated milks in the elderly model indicated by higher percentages of longer peptides during digestion, except for the HPP milk 400 MPa 15 min, which indicated an improved and comparable digestion in the elderly as in the adult model. Furthermore, increasing the pressurization time at 600 MPa did not have a significant effect on the peptides profile during the digestion. More efficient digestion of whey proteins in HPP milks, with the majority of peptides in the 16-20 AA range, compared to fresh milk was also noticed. According to the findings of this study, HPP at 400 MPa 15 min showed the most efficient digestion of major milk proteins and thus may be considered a suitable process to improve bioaccessibility of milk proteins, especially in products intended for the elderly.

Simulated gastrointestinal digestion of camel and bovine casein hydrolysates: Identification and characterization of novel anti-diabetic bioactive peptides

Camel milk proteins are an important substrate for bioactive peptides generation. This study investigates in-vitro antidiabetic effect (via inhibition of α-amylase (AA), α-glucosidase (AG) and dipeptidyl peptidase IV (DPP-IV)) of bovine (BC) and camel casein (CC) hydrolysates. Further, effect of simulated gastrointestinal digestion (SGID) on inhibitory potential of generated hydrolysates was also explored. Both BC and CC hydrolysates displayed potent inhibitory properties against AA (IC₅₀ value- 0.58 & 0.59 mg/mL), AG (IC₅₀ value- 1.04 & 0.59 mg/mL) and DPP-IV (IC₅₀ value- 0.62 & 0.66 mg/mL), respectively. Among different peptides identified in BC and CC hydrolysates, it was observed that FLWPEYGAL was predicted to be most potent inhibitory peptide against AA. While LPTGWLM, MFE and GPAHCLL as most active inhibitor of AG and HLPGRG, QNVLPLH and PLMLP were predicted to be active against DPP-IV. Overall, BC and CC hydrolysates can be proposed to be used in different food formulations as functional antidiabetic agents.

Polyphenol bioaccessibility and antioxidant properties of in vitro digested spray-dried thermally-treated skimmed goat milk enriched with pollen

The aim of research was to determine polyphenols bioaccessibility and antioxidant properties of thermally-treated skimmed goat milk enriched with sunflower bee-collected pollen through in vitro digestion. HPLC analysis confirmed that pollen-enriched milk contained flavonols as the main phenolic fraction (80.7-76.2%) followed by phenolic acids (14.2-17.4%). Among individual compounds quercetin-3-O-glucoside (155.1-197.2 μg/L) and p-coumaric acid (29.5-30.7 μg/L) were the main quantified flavonols and phenolic acids, respectively. After digestion of milk/pollen sample, total polyphenols recovery was 30.71% with higher phenolic acids recovery (40.1%) compared to flavonols (28.3%) indicating strong interactions between caprine milk casein micelles and pollen polyphenols. Applied antioxidant assays (phosphomolybdenum, ABTS•⁺scavenging activity and ferrous-ion-chelating capacity) have confirmed complexity of prepared product- it had high ability to quench ABTS•⁺ radicals and to form chelating complexes with Fe²⁺ ions. Digestion provoked 20% reduction in total antioxidant capacity compared to the initial sample. TTSG milk/pollen powder could be good functional ingredient.

Bioactive peptides in the management of lifestyle-related diseases: Current trends and future perspectives

Lifestyle-related diseases constitute a major concern in the twenty-first century, with millions dying worldwide each year due to chosen lifestyles and associated complications such as obesity, type 2 diabetes, hypertension, and hypercholesterolemia. Although synthetic drugs have been shown to be quite effective in the treatment of these conditions, safety of these compounds remains a concern. Natural alternatives to drugs include food-derived peptides are now being explored for the prevention and treatment of lifestyle-related complications. Peptides are fragments nascent in the primary protein sequences and could impart health benefits beyond basic nutritional advantages. Evidence suggests that by controlling adipocyte differentiation and lipase activities, bioactive peptides may be able to prevent obesity. Bioactive peptides act as agents against type 2 diabetes because of their ability to inhibit enzymatic activities of DPP-IV, α-amylase, and α-glucosidase. Moreover, bioactive peptides can act as competitive inhibitors of angiotensin-converting enzyme, thus eliciting an antihypertensive effect. Bioactive peptides may have a hypocholesterolemic effect by inhibiting cholesterol metabolism pathways and cholesterol synthesis. This review addresses current knowledge of the impact of food-derived bioactive peptides on lifestyle diseases. In addition, future insights on the clinical trials, allergenicity, cytotoxicity, gastrointestinal stability, and regulatory approvals have also been considered.

Compared digestibility of plant protein isolates by using the INFOGEST digestion protocol

The use of ingredients based on plant protein isolates is being promoted due to sustainability and health reasons. However, it is necessary to explore the behaviour of plant protein isolates during gastrointestinal digestion including the profile of released free amino acids and the characterization of resistant domains to gastrointestinal digestion. The aim of the present study was to monitor protein degradation of four legume protein isolates: garden pea, grass pea, soybean and lentil, using the harmonized Infogest in vitro digestion protocol. In vitro digests were characterized regarding protein, peptide and free amino acid content. Soybean was the protein isolate with the highest percentage of insoluble nitrogen at the end of the digestion (12%), being this fraction rich in hydrophobic amino acids. Free amino acids were mainly released during the intestinal digestion, comprising 21-24% of the total nitrogen content, while the percentage of nitrogen corresponding to peptides ranged from 66 to 76%. Legume globulins were resistant to gastric digestion whereas they were hydrolysed into peptides and amino acids during the intestinal phase. However, the molecular weight (MW) distribution demonstrated that all intestinal digests, except those from soybean, contained peptides with MW > 4 kDa at the end of gastrointestinal digestion. The profile of free amino acids released during digestion supports legume protein isolates as an excellent source of essential amino acids to be used in protein-rich food products. Peptides released during digestion matched with previously reported epitopes from the same plant species or others, explaining the ability to induce allergic reactions and cross-linked reactivity.

Cheese as a functional food for older adults: comparing the bioactive properties of different cheese matrices following simulated gastrointestinal in vitro digestion

Age-related changes to the gastrointestinal tract (GIT) can impact how food is digested. Studying the effects of these changes can help identify functional foods for older adults. Cheese was digested using two simulated gastrointestinal in vitro digestion (SGID) models representing adult and elderly gastro-intestinal conditions. Antioxidant capacity was measured using DPPH, FRAP and TPC assays. The ability of cheese to inhibit digestive enzymes was determined by the α-glucosidase and lipase inhibition assays. Digestive aging influenced the bioactivity of cheese, as elderly digestates had significantly lower (p < 0.05) antioxidant, α-glucosidase and lipase inhibitory properties compared to adult digestates. However, soft cheese (feta, goats', brie) demonstrated greatest potential with comparable radical scavenging properties and lipase inhibition, greatest FRAP and α-glucosidase inhibitory potential. Despite age-related changes, the bioactive properties of cheese were evident following digestion with an older adult SGID model, suggesting cheese has potential as a functional food for older adults.

Influence of Pasteurization and Storage on Dynamic In Vitro Gastric Digestion of Milk Proteins: Quantitative Insights Based on Peptidomics

It is important to evaluate the nutritional quality of milk during the shelf-life, especially during home storage, from a consumer viewpoint. In this study, we investigated the impact of pasteurization (85 °C/15 s) and subsequent storage (at 4 °C for 7 days) on the coagulation behavior of milk and protein digestibility in a dynamic in vitro gastric digestion test. A high level of hydration in curd formed in pasteurized milk upon 7-day cold storage compared to raw and pasteurized milk, indicating fast pepsin diffusion in the interior of curds, increasing the hydrolysis rate. The digesta collected at various time points throughout the gastric digestion were studied using o-phthaldialdehyde (OPA), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), liquid chromatography tandem mass spectrometry (LC-MS/MS), and amino acid analysis. These results showed that milk proteins were hydrolyzed quickly upon a long period of cold storage. Additionally, qualitative and quantitative results obtained using LC-MS/MS exhibited significant differences between samples, especially in pasteurized milk upon cold storage. Processing and storage played a decisive role in bioactive peptide generation. Such knowledge could provide insights into and directions for the storage of pasteurized milk for further clinical studies on protein bioavailability and the generation of bioactive peptides for desired health outcomes.

A novel kefir product (PFT) inhibits Ehrlich ascites carcinoma in mice via induction of apoptosis and immunomodulation

BACKGROUND

The popularity of fermented foods such as kefir, kuniss, and tofu has been greatly increasing over the past several decades, and the ability of probiotic bacteria to exert anticancer effects has recently become the focus of research. While we have recently demonstrated the ability of the novel kefir product PFT (Probiotics Fermentation Technology) to exert anticancer effects in vitro, here we demonstrate its ability to inhibit Ehrlich ascites carcinoma (EAC) in mice.

METHODS

Mice were inoculated intramuscularly with EAC cells to develop solid tumors. PFT was administered orally (2 g/kg/day) to mice 6 days/week, either 2 days before tumor cell inoculation or 9 days after inoculation to mice bearing solid tumors. Tumor growth, blood lymphocyte levels, cell cycle progression, apoptosis, apoptotic regulator expression, TNF-α expression, changes in mitochondrial membrane potential (MMP), PCNA, and CD4+ and CD8+ T cells in tumor cells were quantitatively evaluated by flow cytometry or RT-PCR. Further studies in vitro were carried out where EAC cells along with several other human cancer cell lines were cultured in the presence of PFT (0-5 mg/mL). Percent cell viability and IC₅₀ was estimated by MTT assay.

RESULTS

Our data shows that PFT exerts the following: 1) inhibition of tumor incidence and tumor growth; 2) inhibition of cellular proliferation via a marked decrease in the expression of tumor marker PCNA; 3) arrest of the tumor cell cycle in the sub-G0/G1 phase, signifying apoptosis; 4) induction of apoptosis in cancer cells via a mitochondrial-dependent pathway as indicated by the up-regulation of p53 expression, increased Bax/Bcl-2 ratio, decrease in the polarization of MMP, and caspase-3 activation; and 5) immunomodulation with an increase in the number of infiltrating CD4⁺ and CD8⁺ T cells and an enhancement of TNF-α expression within the tumor.

CONCLUSIONS

PFT reduces tumor incidence and tumor growth in mice with EAC by inducing apoptosis in EAC cells via the mitochondrial-dependent pathway, suppressing cancer cell proliferation, and stimulating the immune system. PFT may be a useful agent for cancer prevention.

Protein digestion properties of Xinong Saanen goat colostrum and mature milk using in vitro digestion model

BACKGROUND

Xinong Saanen goat milk is a raw material for goat milk-based infant formula production. This study aims to analyze digestion properties of Xinong Saanen goat colostrum and mature milk by simulating infant gastrointestinal digestion. Zeta potential, particles size, protein profile and peptides composition of these two kinds of milk during the digestion process were studied.

RESULTS

Zeta-potential values of the digested colostrum were lower than those of mature milk through the whole digestion. Absolute zeta potential of colostrum duodenal digestion samples showed a decrease from 16.63 ± 2.08 to 11.80 ± 2.03 mV while that of mature milk decreased sharply and then increased (P < 0.05). Colostrum had a larger particle size than mature milk and both milks showed decreased particle size with increasing digestion time but an increase for the last 30 min. Colostrum showed more high molecular weight (MW) proteins which cannot be hydrolyzed completely compared with mature milk. Digested peptides (< 10 kDa) were characterized using liquid chromatography combined with tandem mass spectrometry (LC-MS/MS). The casein-derived peptides identified in digested colostrum and mature milk accounted for 76.67% and 59.53%, respectively. β-Casein was the most abundant in colostrum while that in mature milk was α_s1 -casein. Enterotoxin-binding glycoprotein PP20K, butyrophilin subfamily 1 member A1 (BTN1A1) and perilipin (PLIN) were only detected in digested mature milk.

CONCLUSION

Differences in digestion properties between goat colostrum and mature milk were mainly shown in duodenal digestion phase. Data may provide useful information about utilization of goat milk for infant formula formulation. © 2019 Society of Chemical Industry.

Profiling of Multiphosphorylated Peptides in Kefir and Their Release During Simulated Gastrointestinal Digestion

Casein phosphopeptides are multiphosphorylated milk peptides, which can have anticariogenic activity and improve mineral absorption by binding bivalent metal ions. The present study investigated phosphopeptides in kefir because fermentation may lead to their enhanced release from milk proteins. After selective enrichment by hydroxyapatite extraction, phosphopeptides and their phosphorylation degree were identified by matrix-assisted desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) before and after enzymatic dephosphorylation. Peptide structures were determined by ultrahigh-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) revealing 27 phosphopeptides in kefir, including nine peptides containing the motif pSpSpSEE, which binds minerals most efficiently. The majority (18) of phosphopeptides were derived from β-casein, but only three were derived from the most abundant milk protein α_s1-casein. After simulated gastrointestinal digestion, MALDI-TOF-MS analysis detected eight putative phosphopeptides in kefir, four of which were assigned by UHPLC-ESI-MS/MS to α_s2-casein_124-133, α_s2-casein_137-146, β-casein_30-40, and κ-casein_147-161. These results indicate that kefir is a good dietary source of multiphosphorylated peptides.

INFOGEST static in vitro simulation of gastrointestinal food digestion

Developing a mechanistic understanding of the impact of food structure and composition on human health has increasingly involved simulating digestion in the upper gastrointestinal tract. These simulations have used a wide range of different conditions that often have very little physiological relevance, and this impedes the meaningful comparison of results. The standardized protocol presented here is based on an international consensus developed by the COST INFOGEST network. The method is designed to be used with standard laboratory equipment and requires limited experience to encourage a wide range of researchers to adopt it. It is a static digestion method that uses constant ratios of meal to digestive fluids and a constant pH for each step of digestion. This makes the method simple to use but not suitable for simulating digestion kinetics. Using this method, food samples are subjected to sequential oral, gastric and intestinal digestion while parameters such as electrolytes, enzymes, bile, dilution, pH and time of digestion are based on available physiological data. This amended and improved digestion method (INFOGEST 2.0) avoids challenges associated with the original method, such as the inclusion of the oral phase and the use of gastric lipase. The method can be used to assess the endpoints resulting from digestion of foods by analyzing the digestion products (e.g., peptides/amino acids, fatty acids, simple sugars) and evaluating the release of micronutrients from the food matrix. The whole protocol can be completed in ~7 d, including ~5 d required for the determination of enzyme activities.

Establishing the impact of food matrix effects on the bioaccessibility of nutraceuticals and pesticides using a standardized food model

It is important to establish the impact of food matrix effects on the bioaccessibility of co-ingested substances, such as nutraceuticals, engineered nanomaterials, pharmaceuticals, and pesticides.

Characterization and identification of novel antidiabetic and anti-obesity peptides from camel milk protein hydrolysates

In-vitro inhibitory properties of peptides released from camel milk proteins against dipeptidyl peptidase-IV (DPP-IV), porcine pancreatic α-amylase (PPA), and porcine pancreatic lipase (PPL) were studied. Results revealed that upon hydrolysis by different enzymes, camel milk proteins displayed dramatic increase in inhibition of DPP-IV and PPL, but slight improvement in PPA inhibition was noticed. Peptide sequencing revealed a total of 20 and 3 peptides for A9 and B9 hydrolysates respectively, obtained the score of 0.8 or more on peptide ranker and were categorized as potential DPP-IV inhibitory peptides. KDLWDDFKGL in A9 and MPSKPPLL in B9 were identified as most potent PPA inhibitory peptide. For PPL inhibition only 7 and 2 peptides qualified as PPL inhibitory peptides from hydrolysates A9 and B9, respectively. The present study report for the first time PPA and PPL inhibitory and only second for DPP-IV inhibitory potential of protein hydrolysates from camel milk.

In vitro bioaccessibility of proteins and lipids of pH-shift processed Nannochloropsis oculata microalga

The pH-shift process fractionates biomass into soluble proteins and insoluble fractions, followed by precipitation and recovery of the solubilized proteins. Nannochloropsis oculata in seawater was subjected to the pH-shift process, followed by digestion of various intermediates and product fractions of the process, using the Infogest in vitro digestion model (Minekus et al., 2014) with added gastric lipase. As measures for protein and lipid accessibility, degrees of protein hydrolysis and fatty acid liberation were assessed post-digestion and compared to the amounts of peptide bonds and total fatty acids present in the raw materials. Results showed that neither proteins nor lipids of intact Nannochloropsis cells were accessible to the mammalian digestive enzymes used in the digestion model. Cell disruption, and to a lesser extent, further pH-shift processing with protein solubilisation at pH 7 or pH 10, increased the accessibility of lipids. For proteins, differences amongst the pH-shift processed materials were non-significant, though pre-freezing the product prior to digestion increased the accessibility from 32% to 47%. For fatty acids, pH-shift process-products gave rise to 43% to 52% lipolysis, with higher lipolysis for products solubilised at pH 10 as opposed to pH 7. Our results indicate the importance of processing to produce an algal product that has beneficial nutritional properties when applied as food or feed.