Effects of different steam injection conditions on cappuccino's nutritional profile.

The quality parameters of cappuccinos prepared with pasteurized milk or ultra-high-temperature milk steam-injected at different temperatures by a professional coffee machine have been assessed. In particular, the protein profile, the content of vitamins and lactose, the lipid peroxidation process, and the involvement of milk proteins in the foam formation were evaluated. The nutritional quality of milk seems not affected by the steam injection treatment carried out at a temperature of 60-65 °C, but at higher temperatures a decrement of lactoperoxidase, vitamin B6 and folic acid was observed. The milk used in cappuccino preparation is very important: pasteurized milk can form a more consistent and lasting foam with respect to ultra-high-temperature milk because of the presence of ß-lactoglobulin and lactoferrin, both playing an important role in the foam formation and stability. This work would provide additional information to the coffee industry for the preparation of high nutritional and organoleptic quality cappuccinos.

Manufacture of Whey Protein Hydrolysates Using Plant Enzymes: Effect of Processing Conditions and Simulated Gastrointestinal Digestion on Angiotensin-I-Converting Enzyme (ACE) Inhibitory Activity.

Hydrolysis of proteins leads to the release of bioactive peptides with positive impact on human health. Peptides exhibiting antihypertensive properties (i.e., inhibition of angiotensin-I-converting enzyme) are commonly found in whey protein hydrolysates made with enzymes of animal, plant or microbial origin. However, bioactive properties can be influenced by processing conditions and gastrointestinal digestion. In this study, we evaluated the impact of three plant enzymes (papain, bromelain and ficin) in the manufacture of whey protein hydrolysates with varying level of pH, enzyme-to-substrate ratio and time of hydrolysis, based on a central composite design, to determine the degree of hydrolysis and antihypertensive properties. Hydrolysates made on laboratory scales showed great variation in the type of enzyme used, their concentrations and the pH level of hydrolysis. However, low degrees of hydrolysis in papain and bromelain treatments were associated with increased antihypertensive properties, when compared to ficin. Simulated gastrointestinal digestion performed for selected hydrolysates showed an increase in antihypertensive properties of hydrolysates made with papain and bromelain, which was probably caused by further release of peptides. Several peptides with reported antihypertensive properties were found in all treatments. These results suggest plant enzymes used in this study can be suitable candidates to develop ingredients with bioactive properties.

Dietary solutions to dyslipidemia: Milk protein-polysaccharide conjugates as liver biochemical enhancers.

Protein-polysaccharide interactions have been a focus of scientific attention. This study aimed to improve the antioxidant and hepatoprotective effects of buffalo total milk proteins and whey protein hydrolysate (WPH) through noncovalent interactions with Psyllium husk (ispaghula) mucilage (PHM) and Nabq mucilage (NabM). Chemical composition, phenolic content, and antioxidant activities of milk protein-mucilage complexes were explored. The effects of resulting complexes on liver function, hyperlipidemia, and histopathology of the liver in rats fed high-fat diet (HFD) were investigated. The results showed that the complexes exerted significant effect on normalizing tested parameters; WPH-NabM had the most significantly decreased level of malondialdehyde content and the liver histopathological examination proved an improvement in all groups fed with these complexes. These complexes can be used as functional protection elements against the nonalcoholic fatty liver disease. PRACTICAL APPLICATIONS: PHM, NabM, and their complexes with milk proteins were proved to improve liver function, enhancing most of its measurable parameters and also diminishing the risk of cardiovascular disease. Mice with HFD achieved better health circumstances by combining these ingredients in their diet. Knowing how much these diseases proliferate in the western world and its correlation with high-fat consumption and modern lifestyle, its conjugation with PHM/NabM-MP complexes may reduce the negative impact of unhealthy food intake and, on some parameters, even improving the whole liver function. For that reason, the present study supports and pushes forward the dissemination and consumption of ispaghula or Nabq (the polysaccharides sources) or supplements originating from them. Although many interactions concerning milk proteins have already been analyzed, our study also proposes the interaction with bioactive polysaccharides as useful, opening a field of research aimed at the better application of milk proteins.

Interfacial and emulsification properties of sono-emulsified grape seed oil emulsions stabilized with milk proteins.

Emulsions were designed under low frequency ultrasound (20 kHz) at energy densities of 11.7-117.0 J/mL using grape seed oil and milk protein solutions containing different casein to whey protein ratios of 80:20, 60:40, 50:50 and 40:60. An increase in energy densities produced emulsions with a smaller droplet size and narrow size distribution at all milk protein ratios. However, the minimum sono-energy density required to produce stable emulsions varied depending on the ratio of caseins (CN) and whey proteins (WP) in the continuous phase. In addition, the composition of the interfacial layer was dependent on the composition of the milk proteins in the continuous phase. The interfacial layer was predominantly covered by the CN and CN-WP aggregates in the presence of equal or greater amounts of caseins than whey proteins (80:20, 60:40 and 50:50), while WP aggregates and CN-WP aggregates were the primary constituents of whey protein-rich emulsions (40:60).

Human Milk Proteins and Their Glycosylation Exhibit Quantitative Dynamic Variations during Lactation.

BACKGROUND: Proteins in human milk are essential and known to support the growth, development, protection, and health of the newborn. These proteins are highly modified by glycans that are currently being recognized as vital to protein structure, stability, function, and health of the intestinal mucosa. Although milk proteins have been studied, the quantitative changes in milk proteins and their respective site-specific glycosylation are unknown. OBJECTIVE: This study expanded the analytical tools for milk proteins and their site-specific glycosylation and applied these tools to a large cohort to determine changes in individual protein concentrations and their site-specific N-glycosylation across lactation. DESIGN: A tandem mass spectrometry method was applied to 231 breast-milk samples from 33 mothers in Davis, California, obtained during 7 different periods of lactation. Dynamic changes in the absolute abundances of milk proteins, as well as variation in site-specific N-glycosylation of individual proteins, were quantified. RESULTS: α-Lactalbumin, ß-casein, k-casein, and α-antitrypsin were significantly increased from colostrum to transitional milk (4.37 ± 1.33 g/L to 6.41 ± 0.72 g/L, 2.25 ± 0.86 g/L to 2.59 ± 0.78 g/L, 1.33 ± 0.44 g/L to 1.60 ± 0.39 g/L, and 0.09 ± 0.10 g/L to 0.11 ± 0.04 g/L, respectively; P < 0.002). α-Lactalbumin (37%), ß-casein (9%), and lysozyme (159%) were higher in mature milk than in colostrum. Glycans exhibited different behavior. Fucosylated glycans of lactoferrin and high-mannose, undecorated, fucosylated, sialylated, and combined fucosylated + sialylated glycans of secretory immunoglobulin A increased during lactation even when the concentrations of the parent proteins decreased. CONCLUSIONS: Proteins in healthy mothers vary dynamically through lactation to support the development of infants. Individual milk proteins carried unique glycan modifications that varied systematically in structure even with site specificity. The role of glycosylation in human milk proteins will be important in understanding the functional components of human milk. This trial was registered at clinicaltrials.gov as NCT01817127.

Hyperimmune Bovine Colostral Anti-CS17 Antibodies Protect Against Enterotoxigenic Escherichia coli Diarrhea in a Randomized, Doubled-Blind, Placebo-Controlled Human Infection Model.

BACKGROUND: Enterotoxigenic Escherichia coli (ETEC) commonly cause diarrhea in children living in developing countries and in travelers to those regions. ETEC are characterized by colonization factors (CFs) that mediate intestinal adherence. We assessed if bovine colostral IgG (bIgG) antibodies against a CF, CS17, or antibodies against CsbD, the minor tip subunit of CS17, would protect subjects against diarrhea following challenge with a CS17-expressing ETEC strain. METHODS: Adult subjects were randomized (1:1:1) to receive oral bIgG against CS17, CsbD, or placebo. Two days prior to challenge, subjects began dosing 3 times daily with the bIgG products (or placebo). On day 3, subjects ingested 5 × 109 cfu ETEC strain LSN03-016011/A in buffer. Subjects were assessed for diarrhea for 120 hours postchallenge. RESULTS: A total of 36 subjects began oral prophylaxis and 35 were challenged with ETEC. While 50.0% of the placebo recipients had watery diarrhea, none of the subjects receiving anti-CS17 had diarrhea (P = .01). In contrast, diarrhea rates between placebo and anti-CsbD recipients (41.7%) were comparable (P = 1.0). CONCLUSIONS: This is the first study to demonstrate anti-CS17 antibodies provide significant protection against ETEC expressing CS17. More research is needed to better understand why anti-CsbD was not comparably efficacious. Clinical Trials Registration. NCT00524004.

Whey protein concentrate limits venous thrombosis in rats.

To study the influence of whey protein concentrate (WPC-80) on the development of thrombosis, rats were supplemented with 2 doses of WPC-80 (0.3 or 0.5 g/kg) for 7, 14, or 21 days. Then, a 1-h venous thrombosis model was performed in half of the animals. Coagulation parameters, platelet count, and thrombus weight were assessed. Thrombus weight was decreased in rats obtaining WPC-80 and that was significant only for 14- and 21-day supplementation. There were slight differences between groups in coagulation parameters and platelet count but without evident direction. Further research is needed to clarify the observed effects.

Antiviral Activity of Curcumin Loaded Milk Proteins Nanoparticles on Potato Virus Y.

BACKGROUND AND OBJECTIVE: Potato is one of the world's leading vegetable crops. Potato viral diseases cause adversely effects on the agricultural sector. Recently there is a growing interest to control plant viruses using spices and herbs (including curcumin). Poor solubility of curcumin in water limited its applications. Therefore, the main objective of the present study was to evaluate the effect of antiviral activity of curcumin-milk proteins nanoparticles against potato virus Y (PVY). MATERIALS AND METHODS: Curcumin-milk proteins nanoparticles were prepared via ionic gelation method. The antiviral activity of the resultant nanoparticles against PVY was evaluated at different concentrations (500, 1000 and 1500 mg/100 mL). Chlorophyll content as well as the activity of peroxidase (POX) and polyphenol oxidase (PPO) was examined. RESULTS: Curcumin-milk proteins nanoparticles showed inhibitory effect on PVY in a concentration dependent manner. CONCLUSION: Curcumin-milk proteins nanoparticles displayed a successful tool to control the PVY under green house conditions.

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.

Antiulcerative and Antinociceptive Activities of Casein and Whey Proteins.

The aim of this study was to evaluate the antiulcerative and antinociceptive activities of milk proteins using the induced gastric ulcer with ethanol rat model and the acetic acid-induced writhing mouse model. Casein (CN), (100, 300, and 1000 mg kg-1) doses presented antiulcerative activity on a dose-dependent manner with values of 30.8%, 41.4%, and 57.0% of inhibition measured using the ulcerative lesions index (ULI), respectively. Whey protein concentrate (WPC), (100, 300, and 1000 mg kg-1) doses presented antiulcerative activity on a dose-dependent manner with values of 48.9%, 65.5%, and 68.22% of ULI inhibition, respectively. CN, casein hydrolysates (CNH), WPC, and whey protein hydrolysates (WPH), (3, 10, and 30 mg kg-1) doses presented antinociceptive activity using the acetic acid-induced writhing in the mouse model. CN (30 mg kg-1) presented a value of 40% of inhibition writhing, and CNH (30 mg kg-1) presented antinociceptive activity with a value up to 46% of writhing inhibition. WPC (30 mg kg-1) presented a value of 52.50%, and WPH (30 mg kg-1) presented antinociceptive activity with a value up to 88.00% of writhing inhibition. In conclusion, CN and WPC demonstrated in vivo antiulcerative properties and represent a promising alternative to be used as protectors of the gastric mucosa. CNH and WPH demonstrated in vivo antiulcerative properties and represent a promising alternative to be used as natural analgesic.

Effects of Milk Proteins Supplementation in Older Adults Undergoing Resistance Training: A Meta-Analysis of Randomized Control Trials.

BACKGROUND: Older adults experience age-related physiological changes that affect body weight and body composition. In general, nutrition and exercise have been identified as potent stimulators of protein synthesis in skeletal muscle. Milk proteins are excellent sources of all the essential amino acids and may represent an ideal protein source to promote muscle anabolism in older adults undergoing resistance training. However, several randomized control trials (RCTs) have yielded mixed results on the effects of milk proteins supplementation in combination with resistance training on body weight and composition. METHODS: PubMed, Web of Science and Cochrane databases were searched for literature that evaluated the effects of milk proteins supplementation on body weight and composition among older adults (age ≥ 60 years) undergoing resistance training up to September 2016. A random-effects model was used to calculate the pooled estimates and 95% confidence intervals (CIs) of effect sizes. RESULTS: The final analysis included 10 RCTs involving 574 participants (mean age range from 60 to 80.8 years). Overall, the combination of milk proteins supplementation and resistance training did not have significant effect on fat mass (0.30, 95% CI -0.25, 0.86 kg) or body weight (1.02, 95% CI: -0.01, 2.04 kg). However, a positive effect of milk proteins supplementation paired with resistance training on fat-free mass was observed (0.74, 95% CI 0.30, 1.17 kg). Greater fat-free mass gains were observed in studies that included more than 55 participants (0.73, 95% CI 0.30, 1.16 kg), and in studies that enrolled participants with aging-related medical conditions (1.60, 95% CI 0.92, 2.28 kg). There was no statistical evidence of publication bias among the studies. CONCLUSION: Our findings provide evidence that supplementation of milk protein, in combination with resistance training, is effective to elicit fat-free mass gain in older adults.

Bodybuilding protein supplements and cow's milk allergy in adult.

Summary: We report a case of a previously healthy 24-year-old man with a 3-month history of gastrointestinal symptoms during exercise and also few minutes after the ingestion of cow's milk (CM) without exercise. He reported the ingestion of a blend of hydrolyzed whey and casein proteins for bodybuilding for the last 2 years. The in vivo tests showed positivity to CM, α-lactalbumin, ß-lactoglobulin and casein extracts, and also to the protein supplement. The serum specific IgE was positive for CM, ß-lactoglobulin and α-lactalbumin. The in vivo and in vitro tests results suggested an IgE-mediated CMA. Adult-onset CMA has been rarely reported, and to our knowledge this is the first case possibly related to bodybuilding supplements. The authors theorize that the presentation of large amounts of proteins in the gastrointestinal tract may favor sensitization.

Comparable effects of breakfast meals varying in protein source on appetite and subsequent energy intake in healthy males.

PURPOSE: The satiating effect of animal vs plant proteins remains unknown. The present study examined the effects of breakfasts containing animal proteins [milk (AP)], a blend of plant proteins [oat, pea and potato (VP)] or 50:50 mixture of the two (MP) compared with a carbohydrate-rich meal (CHO) on appetite, energy intake (EI) and metabolic measures. METHODS: A total of 28 males [mean age 27.4 (±SD 4.2) years, BMI 23.4 (±2.1) kg/m2] consumed three isoenergetic (1674 kJ) rice puddings matched for energy density and macronutrient content as breakfast (25% E from protein) in a single-blind, randomised, cross over design. Appetite ratings and blood samples were collected and assessed at baseline and every 30 and 60 min, respectively, until an ad libitum test meal was served 3.5 h later. Free-living appetite was recorded hourly and EI in weighed food records for the remainder of the day. RESULTS: No differences in subjective appetite ratings were observed after consumption of the AP, VP and MP. Furthermore, there were no differences between the AP, VP, MP and CHO breakfasts in ad libitum EI and self-reported EI during the remainder of the day. Although insulin metabolism was not affected, CHO induced a higher glucose response (P = 0.001) and total amino acids concentration was in the order of AP = MP > VP > CHO breakfast (P = 0.001). CONCLUSION: Manipulating the protein source of foods consumed as breakfast, elicited comparable effects on appetite and EI at both laboratory and free-living environment in healthy men.

Identification of novel dipeptidyl peptidase IV (DPP-IV) inhibitory peptides in camel milk protein hydrolysates.

Nine novel dipeptidyl peptidase IV (DPP-IV) inhibitory peptides (FLQY, FQLGASPY, ILDKEGIDY, ILELA, LLQLEAIR, LPVP, LQALHQGQIV, MPVQA and SPVVPF) were identified in camel milk proteins hydrolysed with trypsin. This was achieved using a sequential approach combining liquid chromatography tandem mass spectrometry (LC-MS/MS), qualitative/quantitative structure activity relationship (QSAR) and confirmatory studies with synthetic peptides. The most potent camel milk protein-derived DPP-IV inhibitory peptides, LPVP and MPVQA, had DPP-IV half maximal inhibitory concentrations (IC50) of 87.0 ±â€¯3.2 and 93.3 ±â€¯8.0 µM, respectively. DPP-IV inhibitory peptide sequences identified within camel and bovine milk protein hydrolysates generated under the same hydrolysis conditions differ. This was linked to differences in enzyme selectivity for peptide bond cleavage of camel and bovine milk proteins as well as dissimilarities in their amino acid sequences. Camel milk proteins contain novel DPP-IV inhibitory peptides which may play a role in the regulation of glycaemia in humans.

Lipid-Based Nutrient Supplements During Pregnancy and Lactation Did Not Affect Human Milk Oligosaccharides and Bioactive Proteins in a Randomized Trial.

BACKGROUND: Human milk oligosaccharides (HMOs) and bioactive proteins are beneficial to infant health. Recent evidence suggests that maternal nutrition may affect the amount of HMOs and proteins in breast milk; however, the effect of nutrient supplementation on HMOs and bioactive proteins has not yet been well studied. OBJECTIVE: We aimed to determine whether lipid-based nutrient supplements (LNSs) affect milk bioactive protein and HMO concentrations at 6 mo postpartum in women in rural Malawi. These are secondary outcomes of a previously published randomized controlled trial. METHODS: Women were randomly assigned to consume either an iron and folic acid capsule (IFA) daily from ≤20 wk gestation until delivery, followed by placebo daily from delivery to 6 mo postpartum, or a multiple micronutrient (MMN) capsule or LNS daily from ≤20 wk gestation to 6 mo postpartum. Breast milk concentrations of total HMOs, sialylated HMOs, fucosylated HMOs, lactoferrin, lactalbumin, lysozymes, antitrypsin, immunoglobulin A, and osteopontin were analyzed at 6 mo postpartum (n = 647). Between-group differences in concentrations and in proportions of women classified as having low concentrations were tested. RESULTS: HMO and bioactive protein concentrations did not differ between groups (P > 0.10 for all comparisons). At 6 mo postpartum, the proportions of women with low HMOs or bioactive proteins were not different between groups except for osteopontin. A lower proportion of women in the IFA group had low osteopontin compared with the LNS group after adjusting for covariates (OR: 0.5; 95% CI: 0.3, 0.9; P = 0.016). CONCLUSION: The study findings do not support the hypothesis that supplementation with an LNS or MMN capsule during pregnancy and postpartum would increase HMO or bioactive milk proteins at 6 mo postpartum among Malawian women. This trial was registered at clinicaltrials.gov as NCT01239693.

Fast digestive, leucine-rich, soluble milk proteins improve muscle protein anabolism, and mitochondrial function in undernourished old rats.

SCOPE: One strategy to manage malnutrition in older patients is to increase protein and energy intake. Here, we evaluate the influence of protein quality during refeeding on improvement in muscle protein and energy metabolism. METHODS AND RESULTS: Twenty-month-old male rats (n = 40) were fed 50% of their spontaneous intake for 12 weeks to induce malnutrition, then refed ad libitum with a standard diet enriched with casein or soluble milk proteins (22%) for 4 weeks. A 13C-valine was infused to measure muscle protein synthesis and expression of MuRF1, and MAFbx was measured to evaluate muscle proteolysis. mTOR pathway activation and mitochondrial function were assessed in muscle. Malnutrition was associated with a decrease in body weight, fat mass, and lean mass, particularly muscle mass. Malnutrition decreased muscle mTOR pathway activation and protein FSR associated with increased MuRF1 mRNA levels, and decreased mitochondrial function. The refeeding period partially restored fat mass and lean mass. Unlike the casein diet, the soluble milk protein diet improved muscle protein metabolism and mitochondrial function in old malnourished rats. CONCLUSIONS: These results suggest that providing better-quality proteins during refeeding may improve efficacy of renutrition in malnourished older patients.

Potential of Casein as a Carrier for Biologically Active Agents.

Casein is the collective name for a family of milk proteins. In bovine milk, casein comprises four peptides: αS1, αS2, ß, and κ, differing in their amino acid, phosphorus and carbohydrate content but similar in their amphiphilic character. Hydrophilic and hydrophobic regions of casein show block distribution in the protein chain. Casein peptides carry negative charge on their surface as a result of phosphorylation and tend to bind nanoclusters of amorphous calcium phosphate. Due to these properties, in suitable conditions, casein molecules agglomerate into spherical micelles. The high content of casein in milk (2.75 %) has made it one of the most popular proteins. Novel research techniques have improved understanding of its properties, opening up new applications. However, casein is not just a dietary protein. Its properties promise new and unexpected applications in science and the pharmaceutical and functional food industries. One example is an encapsulation of health-related substances in casein matrices. This review discusses gelation, coacervation, self-assembly and reassembly of casein peptides as means of encapsulation. We highlight information on encapsulation of health-related substances such as drugs and dietary supplements inside casein micro- and nanoparticles.

Milk-derived bioactive peptides and their health promoting effects: a potential role in atherosclerosis.

Bioactive peptides derived from milk proteins are food components that, in addition to their nutritional value, retain many biological properties and have therapeutic effects in several health disorders, including cardiovascular disease. Amongst these, atherosclerosis is the underlying cause of heart attack and strokes. It is a progressive dyslipidaemic and inflammatory disease where accumulation of oxidized lipids and inflammatory cells leads to the formation of an atherosclerotic plaque in the vessel wall. Milk-derived bioactive peptides can be released during gastrointestinal digestion, food processing or by enzymatic and bacterial fermentation and are considered to promote diverse beneficial effects such as lipid lowering, antihypertensive, immnomodulating, anti-inflammatory and antithrombotic effects. In this review, an overview of the diverse biological effects of these compounds is given, particularly focusing on their beneficial properties on cardiovascular disease and proposing novel mechanisms of action responsible for their bioactivity. Attempts to prevent cardiovascular diseases target modifications of several risk factors such as high blood pressure, obesity, high blood concentrations of lipids or insulin resistance. Milk-derived bioactive peptides are a source of health-enhancing components and the potential health benefit of these compounds has a growing commercial potential. Consequently, they have been incorporated as ingredients in functional foods, as dietary supplements and as pharmaceuticals to promote health and reduce risk of chronic diseases.

Effects of a diet containing dried grape pomace on blood metabolites and milk composition of dairy cows.

BACKGROUND: The effect of a diet containing 15% grape pomace (GP) on the general health status and milk quality of dairy cows was assessed by plasma biochemistry and total polyphenol (TP) content, milk polyphenols, milk composition and milk protein fractions. RESULTS: Among the polyphenols measured by liquid chromatography-mass spectroscopy in GP, in feed containing GP (GP+) or not containing GP (GP-), gallic acid and epicatechin were present in the highest concentrations (67.58 and 19.23 µg mL-1 , respectively). Higher amounts of TP were also detected in the blood plasma of GP+ cows (114.06 and 83.93 mg GAE L-1 , respectively) but not in their milk (233.17 and 245.75 mg GAE L-1 , respectively). Also a significant increase was found for lactose and ß-lactoglobulin, although there was no effect on α-lactalbumin, albumin, secretory components and caseins. CONCLUSION: Inclusion of 15% GP in the diets of dairy cows is beneficial for overall normal blood constituent metabolism and helps to maintain cow health. The milk of cows fed with a GP diet preserves the normal levels of fat, protein and caseins, and has increased levels of components that make this milk a versatile ingredient material for the food industry (e.g. model whey powders, stability of lactose-rich powders). © 2016 Society of Chemical Industry.

Addition of milk to tea infusions: Helpful or harmful? Evidence from in vitro and in vivo studies on antioxidant properties.

Tea consumption is practised as a tradition, and has shown potential to improve human health. Maximal uptake of tea antioxidants and milk proteins without a negative impact on tea flavor is highly desired by consumers. There is a conflicting evidence of the effect of milk addition to tea on antioxidant activity. Differences in the type of tea, the composition, type and amount of milk, preparation method of tea-milk infusions, the assays used to measure antioxidant activity, and sampling size likely account for different findings. Interactions between tea polyphenols and milk proteins, especially between catechins and caseins, could account for a decrease in antioxidant activity, although other mechanisms are also possible, given the similar effects between soy and bovine milk. The role of milk fat globules and the milk fat globule membrane surface is also important when considering interactions and loss of polyphenolic antioxidant activity, which has not been addressed in the literature.