Proteolytic and angiotensin‐converting enzyme‐inhibitory activities of selected probiotic bacteria

This study was carried out to examine the proteolytic and angiotensin‐converting enzyme (ACE‐I) activities of probiotic lactic acid bacteria (LAB) as influenced by the type of media, fermentation time, strain type and media supplementation with a proteolytic enzyme (Flavourzyme^®). Lactobacillus casei (Lc210), Bifidobacterium animalis ssp12 (Bb12), Lactobacillus delbrueckii subsp. bulgaricus (Lb11842) and Lactobacillus acidophilus (La2410) were grown in 12% of reconstituted skim milk (RSM) or 4% of whey protein concentrates (WPC‐35) with or without combination (0.14%) of Flavourzyme^® for 12 h at 37 °C. All the strains were able to grow in both media depending on type of strains used and fermentation time. All the strains showed higher proteolytic activity and produced more antihypersensitive peptides when grown in RSM medium at 12 h, when compared to WPC. Combination with Flavourzyme^® also increased LAB growth and proteolytic and ACE‐I activities. Of the four strains used, Bb12 and La2410 outperformed Lc210 and Lb11842. The highest ACE‐I activity and proteolytic activity were found in B. animalis ssp12 combined with Flavourzyme^®. Flavourzyme^® led to an increase in the production of bioactive peptides with ACE‐I activity during 12 h at 37 °C.     

Effects of fermentation conditions on the potential anti‐hypertensive peptides released from yogurt fermented by Lactobacillus helveticus and Flavourzyme®

This study investigates the effects of fermentation conditions on the production of angiotensin‐converting enzyme inhibitory (ACE‐I) peptides in yogurt by Lactobacillus helveticus 881315 (L. helveticus) in the presence or absence of Flavourzyme^®, which is derived from a mould, Aspergillus oryzae and used for protein hydrolysis in various industrial applications. Optimal conditions for peptides with the highest ACE‐I activity were 4% (v/w) inoculum size for 8 h without Flavourzyme^® supplementation, and 1% inoculum size for 12 h when combined with Flavourzyme^®. The yogurt fermented by L. helveticus resulted in IC₅₀ values (concentration of inhibitor required to inhibit 50% of ACE activity under the assayed conditions) of 1.47 ± 0.04 and 16.91 ± 0.25 mg mL^?1 with and without Flavourzyme^® respectively. Seven fractions of ACE‐I peptides from the yogurt incorporated with L. helveticus and Flavourzyme^® were separated using the preparative high‐performance liquid chromatography. Fraction (F3) showed the highest ACE‐I activity with an IC₅₀ of 35.75 ± 5.48 μg mL^?1. This study indicates that yogurt may be a valuable source of ACE‐I peptides, which may explain the outcomes observed in the experimental and clinical studies and foresee the application of fermented milk proteins into functional foods or dietary supplements.     

Protein hydrolysate from tilapia frame: antioxidant and angiotensin I converting enzyme inhibitor properties

The effect of varying the aminopeptidase concentration and hydrolysis time in the production of a protein hydrolysate from tilapia frame (TFPH) was evaluated in terms of the obtained antioxidant and angiotensin I converting enzyme (ACE) inhibitor activities. Minced tilapia frame was subjected to hydrolysis using three concentrations Flavourzyme^® 1000 L [Brenntag Ingredients (Thailand) Company Limited (Public), Bangkok, Thailand] [0%, 1% and 2% (w/w)] and two hydrolysis times (0 and 1 h). The enzyme concentration and hydrolysis time both significantly affected the antioxidant and ACE inhibitor properties. The use of 2% (w/w) Flavourzyme^® 1000 L for 1 h yielded the highest levels of 2,2‐diphenyl‐1‐picrylhydrazil free radical scavenging (90.4%), metal chelating (91.8%), thiobarbituric acid activity ratio (81.9%), and ACE inhibition (83.8%). In addition, this TFPH contained a higher net amount of amino acids and a larger peptide molecular weight distribution compared to the unhydrolysed tilapia frame supernatant. Thus, TFPH may be a suitable supplement to improve the functionality of food products.     

An application in Gouda cheese manufacture for a strain of Lactobacillus helveticus ND01

Gouda cheese was manufactured with Lactococcus lactis ssp. lactis IMAU60010, L. lactis ssp. cremoris IMAU40136 and L. helveticus ND01 isolated from the naturally fermented milk in China. Starter cultures added with L. helveticus ND01 produced Gouda cheese with dramatically more proteolysis than control cheeses. Compared with control cheese, experimental cheese with L. helveticus ND01 adjunct revealed dramatic increase in both Angiotensin I‐converting enzyme (ACE)‐inhibitory activity and γ‐aminobutyric acid content. The ACE‐inhibitory activity of Gouda cheeses with the addition of 1 × 10⁵ CFU/mL L. helveticus ND01 increases from 53.7 to 83.1% at 6 weeks of ripening.     

Angiotensin‐I converting enzyme inhibitory and antioxidant activities of peptide fractions extracted by ultrafiltration of cowpea Vigna unguiculata hydrolysates

BACKGROUND: Enzymatic proteolysis of food proteins is used to produce peptide fractions with the potential to act as physiological modulators. Fractionation of these proteins by ultrafiltration results in fractions rich in small peptides with the potential to act as functional food ingredients. The present study investigated the angiotensin‐I converting enzyme (ACE‐I) inhibitory and antioxidant activities for hydrolysates produced by hydrolyzing Vigna unguiculata protein extract as well as ultrafiltered peptide fractions from these hydrolysates. RESULTS: Alcalase^®, Flavourzyme^® and pepsin–pancreatin were used to produce extensively hydrolyzed V. unguiculata protein extract. Degree of hydrolysis (DH) differed between the enzymatic systems and ranged from 35.7% to 58.8%. Fractionation increased in vitro biological activities in the peptide fractions, with IC₅₀ (hydrolysate concentration in µg protein mL^?1 required to produce 50% ACE inhibition) value ranges of 24.3–123 (Alcalase hydrolysate, AH), 0.04–170.6 (Flavourzyme hydrolysate; FH) and 44.7–112 (pepsin–pancreatin hydrolysate, PPH) µg mL^?1, and TEAC (Trolox equivalent antioxidant coefficient) value ranges of 303.2–1457 (AH), 357.4–10 211 (FH) and 267.1–2830.4 (PPH) mmol L^?1 mg^?1 protein. CONCLUSION: The results indicate the possibility of obtaining bioactive peptides from V. unguiculata proteins by means of a controlled protein hydrolysis using Alcalase^®, Flavourzyme^® and pepsin–pancreatin. The V. unguiculata protein hydrolysates and their corresponding ultrafiltered peptide fractions might be utilized for physiologically functional foods with antihypertensive and antioxidant activities. Copyright © 2010 Society of Chemical Industry     

Multivariate strategy in screening of enzymes to be used for whey protein hydrolysis in an enzymatic membrane reactor

Proteinase activities for Alcalase^® 2.4L (EC 3.4.21.62), Flavourzyme^® (EC 3.4.11.1), Protease A (EC 3.4.24.39) and Protease N (IUB 3.4.24.28) were determined using 2% whey protein isolate (WPI) and 2% casein. The optimum substrate and enzyme concentrations and temperature were determined by the pH-stat method. Residual enzyme activity, hydrolysate molecular weight and free amino acid (FAA) content were determined. Protease N and Alcalase^® 2.4L had the highest proteinase activities on casein and WPI, respectively. Alcalase^® 2.4L was more stable in the presence of WPI while Protease N was inhibited by hydrolysates, and like Protease A which released high FAAs, they produced shorter peptides. Flavourzyme^® hydrolysed WPI poorly and released the highest FAAs. Short peptides were removed by 5% trichloroacetic acid (TCA) and 3.5% 5-sulphosalicylic acid before FAA analysis by reversed phase high-performance liquid chromatography (RP-HPLC) of Flavourzyme^® and Protease A hydrolysates, but were detected in Alcalase^® 2.4L and Protease N hydrolysates. The enzyme activities for WPI hydrolysis in an enzymatic membrane reactor were Flavourzyme^®<Protease A<Alcalase^® 2.4L⩽Protease N.     

Effects of enzymatic hydrolysis treatments on the physicochemical properties of beef bone extract using endo- and exoproteases

This study reported the effects of enzymatic hydrolysis treatments on the physiochemical properties of beef bone extract using endo- and exoproteases. Each enzyme hydrolysis kinetics were studied using Michaelis–Menten model, and the ideal E/S ratio obtained for Protamex^® (P), bromelain (B) and Flavourzyme^® (F) was found to be 1.10%, 1.60% and 4.70% w/w, respectively. Seven hydrolysates were produced from single (P, B, F), simultaneous (P + F, B + F) and sequential (P > F, B > F) treatments, where bone extract hydrolysed by Flavourzyme^® exhibited highest DH and proportion of low molecular weight (Mw) peptides (<5000 Da) in single treatment. When Flavourzyme^® was used with Protamex^® or bromelain in simultaneous or sequential treatments, no significant differences in Mw distribution, exposed SH content, SS content and viscosity were evident compared with Flavourzyme^® only. This indicated that without the addition of other enzymes, Flavourzyme^® was capable of increasing the proportion of low Mw peptides and reduce viscosity.     

A comparative study of physico‐chemical properties and antioxidant activity of freeze‐dried mung bean (Vigna radiata) and adzuki bean (Vigna angularis) sprout hydrolysate powders

Mung bean (MB) and adzuki bean (AZB) sprouts were hydrolysed with Flavourzyme^® at four different concentrations for 6 h. Nongerminated beans subjected to each enzyme concentrations were set as the control. For both bean sprouts, the highest amounts of free amino group, total free amino acids and total phenolic content (TPC) were obtained with 7% (w/w) Flavourzyme^®. Each bean sprout hydrolysate was subjected to freeze‐drying in absence and presence of 5% maltodextrin (w/v). The addition of maltodextrin resulted in a decrease in the free amino group, TPC, surface hydrophobicity and hygroscopicity in resulting freeze‐dried powders. Gallic acid, p‐coumaric acid and vitexin were identified in all freeze‐dried powders, while catechin and rutin were detected only in freeze‐dried AZB hydrolysate powder. Freeze‐dried AZB hydrolysate powder contained higher antioxidant activities. DPPH radical scavenging activity of all samples measured using electron spin resonance spectrometry was higher than that obtained by the colorimetric method.     

ACE-inhibitory activity and gamma-aminobutyric acid content of fermented skim milk by <Emphasis Type="Italic">Lactobacillus helveticus</Emphasis> isolated from Xinjiang koumiss in China

Eighty-one strains of Lactobacillus were isolated from the koumiss collected in Xinjiang, China. The strains were cultivated in skim milk medium, ACE inhibitory activity and GABA concentrations in the culture supernatants were measured. Screening results revealed that ACE inhibitory activity of 16 strains was higher than 50% and two strains produced GABA. The Lactobacillus—ND01 strain produces both the high ACE inhibitory activity and GABA. The sequence of 16S rDNA of the Lactobacillus—ND01 showed 99% homology to L. helveticus. The first identification of the newly isolated Lactobacillus—ND01 strain which produces both high ACE inhibitory activity and GABA revealed differences from reported species in our study. The L. helveticus ND01 was resistant to acidic condition. The results suggest that L. helveticus ND01 showed good potential for application in the management of hypertension.     

Angiotensin I‐converting enzyme inhibitory peptides in skim milk fermented with Lactobacillus helveticus 130B4 from camel milk in Inner Mongolia,China

BACKGROUND: Angiotensin I‐converting enzyme (ACE) is a dipeptidyl carboxypeptidase associated with the regulation of blood pressure. ACE inhibition results in a lowering of blood pressure. Lactic acid bacteria are known to produce ACE inhibitors during fermentation. Fermented camel milk is the main traditionally fermented dairy food for desert nomads. The beneficial effects of fermented camel milk, which include the prevention of such diseases and conditions as gastroenteritis, tuberculosis and hypertension, have been demonstrated experimentally. RESULTS: ACE inhibitory activity was observed in fermented milk containing Lactobacillus helveticus 130B4, a strain isolated from traditionally fermented camel milk. The peptide that inhibited ACE was purified from the fermented milk by reverse‐phase high‐performance liquid chromatography. The amino acid sequence of the peptide was identified as Ala‐Ile‐Pro‐Pro‐Lys‐Lys‐Asn‐Gln‐Asp (IC₅₀ = 19.9 µmol L^?1). The same Ala‐Ile‐Pro‐Pro‐Lys‐Lys‐Asn‐Gln‐Asp sequence was found in κ‐casein (κ‐CN) f107–115 from milk. The inhibitory activity of this nonapeptide (κ‐CN f107–115) was almost preserved even after successive digestion with pepsin, trypsin and chymotrypsin. Furthermore, the inhibitory activity of the purified peptide was completely preserved after heat treatment at 100 °C for 20 min. CONCLUSION: The fermented milk prepared with Lactobacillus helveticus 130B4 contained an ACE inhibitory peptide, κ‐CN 107–115. This fermented milk was expected to have anti‐hypertensive effect after ingestion because the peptide was stable to digestive protease and heat treatment in vitro. Copyright © 2008 Society of Chemical Industry     

Production and characterization of angiotensin converting enzyme (ACE) inhibitory peptides from apricot (Prunus armeniaca L.) kernel protein hydrolysate

Six different proteases (Flavourzyme^®, Neutrase^®, Protamex^®, Alcalase^® 2.4L, Proleather^® FG-F, and papain) were employed to hydrolyze apricot kernel protein (AKP). Alcalase^® is an inexpensive and non-specific protease that has been shown to be useful for the generation of bioactive peptides from AKP. Alcalase^® 2.4L was selected for further study on enzymatic preparation of ACE inhibitory peptide from AKP. After 60-min hydrolysis, the highest ACE inhibition was 82 ± 0.14%. Results of molecular weight distribution revealed that most of ACE inhibition activity was probably attributed to low-molecular weight peptide fraction ranging from 200 to 900 Da. Ultrafiltration on membranes with several molecular weight cutoffs (MWCFs) demonstrated that most of the ACE inhibitory activity was due to peptides with a less than 1,000 Da molecular weight: the IC₅₀ value of the 1-kDa ultrafiltrate was 0.15 ± 0.007 mg mL^?1, while it was 0.378 ± 0.015 mg mL^?1 before ultrafiltration. Additionally, further separation and purification of the ACE inhibitory peptides were carried out using gel filtration and C₁₈ RP-HPLC. The result of research can be used to optimize AKP enzymatic hydrolysis for producing ACE inhibitory peptides which could be used for food industry and nutraceuticals.     

Probiotic Strains as Starter Cultures Improve Angiotensin-converting Enzyme Inhibitory Activity in Soy Yogurt

Suitability of soy yogurt as a system for delivering probiotics and other bioactive compounds was assessed by fermenting soy milk using starter culture containing Lactobacillus delbrueckii ssp. bulgaricus Lb1466, Streptococcus thermophilus St1342, and probiotic organisms (Lactobacillus acidophilus LAFTI® L10, Bifidobacterium lactis LAFTI® B94, and Lactobacillus paracasei LAFTI® L26). Fermentations were terminated at different pH of 4.50, 4.55, and 4.60 and metabolic patterns of cultures (viability, proteolytic activity, organic acids production, angiotensin‐converting enzyme (ACE) inhibitory activity) were investigated during 28 d of storage at 4 °C. The presence of probiotics enhanced the growth of L. delbrueckii ssp. bulgaricus Lb1466 and S. thermophilus St134 in soy yogurt in comparison to the control produced by sole yogurt culture. In general, different termination pH had no effect (P > 0.05) on the viability of probiotic organisms that maintained good viability in soy yogurt during cold storage. Higher levels of essential growth factors in the form of peptides and amino acids in soy yogurts may have promoted the growth of L. acidophilus LAFTI® L10, B. lactis LAFTI® B94, and L. paracasei LAFTI® L26. The use of probiotic strains as a part of starter culture in soy yogurt resulted in a substantial increase in in vitro ACE inhibitory activity compared with the control produced by yogurt culture only. This improvement of ACE inhibition in soy yogurt is partly due to higher proteolytic activity of probiotics.     

Comparison of physicochemical properties,antioxidant and metal‐chelating activities of protein hydrolysates from Phaseolus lunatus and hard‐to‐cook Phaseolus vulgaris

Limited and extensive hydrolysates were obtained from Phaseolus lunatus (LHl and EHl) and hard‐to‐cook Phaseolus vulgaris (LHv and EHv) using the enzymes Flavourzyme^®, Alcalase^®, Pancreatin^® and a sequential Pepsin^®–Pancreatin^® system. Degrees of hydrolysis varied from 8.32% to 31.60%. SDS‐PAGE of extensive hydrolysates showed molecular weights smaller than limited hydrolysates. Differential scanning calorimeter (DSC) analysis of LHl and EHl revealed the presence of two endothermic transitions; LHv and EHv had only one. LHv presented a higher content of hydrophobic amino acids whose surface hydrophobicity was 12.17. Functional properties such as nitrogen solubility, foaming capacity and emulsifying activity index in LHv were better than LHl at different pH evaluated. However, the latter showed better foaming stabilities. Amino acids such as His, Tyr, Trp and Arg were observed in greater amounts in both extensive hydrolysates. 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical‐scavenging and metal‐chelating activities in EHv and EHl increased significantly compared to the source material.     

Effect of milk fat replacement by polyunsaturated fatty acids on the microbiological,rheological and sensorial properties of fermented milks

A modified milk (W3DD) where fat had been replaced by oils enriched in ω‐3 polyunsaturated fatty acids was used for the manufacture of a set‐type fermented product. In order to improve the organoleptic properties of the product, 30 g l^?1 whey protein concentrate (WPC) was added during the manufacturing process. Samples were fermented employing a commercial probiotic starter culture (ABT‐2), which contained Streptococcus thermophilus ST‐20Y, Lactobacillus acidophilus LA‐5 and Bifidobacterium lactis BB‐12. The acidification process was dependent on the WPC addition, which favoured the increase of viable counts, but fermentation was not influenced by the milk fat composition. The highest counts of the probiotic strains, L acidophilus LA‐5 (3.3 × 10⁵ cfu g^?1) and B lactis BB‐12 (5.5 × 10⁷ cfu g^?1), after 21 days of storage at 4 °C, were found in fermented products derived from W3DD supplemented with WPC. Addition of WPC also increased the firmness of the products and reduced syneresis. No apparent colour changes due to fat composition or WPC supplementation were observed in the products. Milk fat replacement by oils rich in ω‐3 polyunsaturated fatty acids had a negative influence on the product texture but did not affect the typical yoghurt flavour. These defects were overcome by the addition of 30 g l^?1 WPC, which improved the appearance, texture and general acceptability scores in the product. Copyright © 2004 Society of Chemical Industry     

Improving antioxidant activity of black bean protein by hydrolysis with protease combinations

This study explored the use of a simplex centroid design to produce protein hydrolysates with antioxidant properties using Alcalase^® 2.4L, Flavourzyme^® 500L and Neutrase^® 0.8L. Proteases kinetic parameters and the ultrafiltration of protein hydrolysates were also investigated. The highest antioxidant activity, in the studied conditions, was reached when the mixture of Alcalase^® 2.4L and Flavourzyme^® 500L was used in the hydrolysates production. The antioxidant power of the black bean proteins, measured by the total antioxidant capacity and reducing power assay, increased after hydrolysis by 31% and 70%, respectively. The black bean proteins hydrolysates fractions (3–30 kDa) showed an antioxidant activity decrease along with a reduction in molecular weight, demonstrating that a set of varied molecular weight peptides was responsible for the antioxidant characteristics of black bean protein hydrolysates.     

Angiotensin‐converting enzyme‐inhibitory activity in protein hydrolysates from normal and anthracnose disease‐damaged Phaseolus vulgaris seeds

BACKGROUND: Bean seeds are an inexpensive source of protein. Anthracnose disease caused by the fungus Colletotrichum lindemuthianum results in serious losses in common bean (Phaseolus vulgaris L.) crops worldwide, affecting any above‐ground plant part, and protein dysfunction, inducing the synthesis of proteins that allow plants to improve their stress tolerance. The aim of this study was to evaluate the use of beans damaged by anthracnose disease as a source of peptides with angiotensin‐converting enzyme (ACE‐I)‐inhibitory activity. RESULTS: Protein concentrates from beans spoiled by anthracnose disease and from regular beans as controls were prepared by alkaline extraction and precipitation at isolelectric pH and hydrolysed using Alcalase 2.4 L. The hydrolysates from spoiled beans had ACE‐I‐inhibitory activity (IC₅₀ 0.0191 mg protein mL^?1) and were very similar to those from control beans in terms of ACE‐I inhibition, peptide electrophoretic profile and kinetics of hydrolysis. Thus preparation of hydrolysates using beans affected by anthracnose disease would allow for revalorisation of this otherwise wasted product. CONCLUSION: The present results suggest the use of spoiled bean seeds, e.g. anthracnose‐damaged beans, as an alternative for the isolation of ACE‐I‐inhibitory peptides to be further introduced as active ingredients in functional foods. © 2012 Society of Chemical Industry     

Multi‐Cereal Beverage Fermented by Lactobacillus Helveticus and Saccharomyces Cerevisiae

A novel multi‐cereal‐based fermented beverage with suitable aroma, flavor, and pH fermented by lactic acid bacteria and Saccharomyces cerevisiae was developed. Twenty‐seven lactobacilli strains were screened for acid production (pH and titratable acidity) in a mixture of malt, rice, and maize substrates. It was found that Lactobacillus helveticus KLDS1.9204 had the greatest acid production among 27 lactobacilli tested. The fermentation performance of L. helveticus KLDS1.9204 was also assayed and the fermentation parameters were optimized using Plackett–Burman design and steepest ascent method. L. helveticus KLDS1.9204 showed good proteolytic capability, however, the strain could not utilize starch. The optimum substrate consisted of 50% malt (25 g/100 mL), 25% rice (20 g/100 mL), and 25% maize (30 g/100 mL). The inoculum was 5% with a ratio of S. cerevisiae to L. helveticus KLDS1.9204 of 2.5:1. The optimum temperature was 37 °C and the time was 22 h. Lastly, the quality of the multi‐cereal‐based fermented beverage was evaluated. This beverage was light yellow, transparent, and it tasted well with a pleasant acid and a unique flavor of cereals. The beverage was rich in free amino acids and organic acids. The pH and titratable acidity of the beverage were 3.5 and 29.86 °T, respectively. The soluble solids content of the beverage was 6.5 °Brix, and the alcohol content was 0.67%.     

Optimization of sour milk fermentation for the production of ACE-inhibitory peptides and purification of a novel peptide from whey protein hydrolysate

The effect of fermentation conditions on the production of angiotensin-I converting enzyme (ACE) inhibitory peptide in sour milk fermented by Lactobacillus helveticus LB10 was investigated using response-surface methodology. Optimal conditions to produce the maximum production of ACE-inhibitory peptides were found to be 4% (v/w) inoculum, 7.5 initial pH of medium and 39.0 °C. The fermented milk resulted in 75.46% inhibition in ACE activity. The cell-envelope proteinase, assisted by X-prolyldipeptidyl aminopeptidase of Lb. helveticus LB10 produced the ACE-inhibitory peptides. A novel ACE-inhibitory peptide from whey protein hydrolysate produced by crude proteinases of Lb. helveticus LB10 was purified. The separations were performed with Sephadex^® G-75 and Sephadex G-15 gel filtration chromatography and reversed-phase, high-performance liquid chromatography. The peptide with the RLSFNP sequence was isolated from β-lactoglobulin hydrolysate and its IC₅₀ while inhibiting ACE activity was 177.39 μm.     

Limited hydrolysis of β‐casein by cell wall proteinase and its effect on hydrolysates's conformational and structural properties

Optimisation of enzymatic hydrolysis of β‐casein with cell envelope proteinase (CEP) from Lactobacillus acidophilus JQ‐1 to produce the angiotensin‐I‐converting enzyme (ACE) inhibitory peptides using response surface methodology (RSM). Under optimal conditions (enzyme‐to‐substrate ([E]/[S]) ratio (w/w) of 0.132 and pH of 8.00 at 38.8 °C), the ACE inhibitory activity of hydrolysates was 72.06% and the total peptides was 11.75 mg mL^?1. Scanning electron microscopy (SEM) micrographs indicated that the tightness of the β‐casein surface structure was gradually weakened and small holes appeared after enzymatic treatment, while Fourier transform infrared spectroscopy (FTIR) spectra indicated remarkable changes in the chemical composition and macromolecular conformation of β‐casein after enzymatic hydrolysis. Differential scanning calorimetry (DSC) analysis indicated that the corresponding hydrolysates had higher thermal stability. The enzymatic hydrolysis also led to an increase in the free sulfhydryl content of β‐casein hydrolysates compared with raw β‐casein, which led to the increase in the antioxidant activity of β‐casein hydrolysates.     

Influence of adjunct cultures on angiotensin‐converting enzyme (ACE)‐inhibitory activity,organic acid content and peptide profile of kefir

The angiotensin‐converting enzyme (ACE)‐inhibitory activities, peptide profiles and organic acid contents in kefir produced by kefir grains plus lactic acid bacteria as adjunct cultures were determined. All the kefir samples showed almost similar peptide profiles as detected by RP‐HPLC, but quantitative differences were observed during storage. The ACE‐inhibitory activities of different lactic cultures did not exhibit a linear tendency during storage period. After 7 days of storage, there was a significant increase in ACE‐inhibitory activity of the sample fermented with Lactobacillus helveticus. However, a kefir sample containing Streptococcus thermophilus, Lactobacillus acidophilus and Bifidobacterium animalis subsp. lactis exhibited a higher ACE‐inhibitory activity (92.23%) compared to the other samples.