Viscoelastic properties of caseinmacropeptide isolated from cow,ewe and goat cheese whey

Caseinmacropeptide (CMP) is a C‐terminal glycopeptide released from κ‐casein by the action of chymosin during cheese‐making. It is recognised as a bioactive peptide and is thought to be an ingredient with a potential use in functional foods. CMP occurs in sweet cheese whey and whey protein concentrate (WPC). Its composition is variable and depends on the particular whey source and the fractionation technology employed in the isolation. There were no significant (P < 0.05) differences in the relative apparent viscosities between species of CMPs (cow, ewe and goat). Analyses at different pH (2, 4, 7, 10), ionic strength (0, 0.2, 0.4 and 0.7 as NaCl molarity) and protein concentration (50, 100 and 200 g kg^?1) at temperatures from 10 to 90 °C carried out found pH 7 and high protein concentration (200 g kg^?1) conditions to be the best for CMP solutions to keep low and constant relative viscosity values with increasing temperature up to 75 °C. The viscoelastic properties–storage modulus, loss modulus and phase angle–of the different CMPs and WPC solutions were determined. Heat‐induced rheological changes in CMP solutions occurred at moderate temperatures (40–50 °C) with no appreciable differences in viscosity. Gelation took place significantly (P < 0.05) earlier in goat CMP (41 °C), followed by cow CMP (44 °C), ewe CMP (47 °C) and WPC (56 °C). Heating at 90 °C showed that WPC required significantly (P < 0.05) longer times to form gels (>5 min) than the CMPs (<5 min). WPC gels had higher (>20°) phase angle than CMP (<20°), which could be associated with untidy structures, limiting elastic properties of the gel. Copyright © 2006 Society of Chemical Industry     

Inhibition of adhesion of <Emphasis Type="Italic">Streptococcus mutans</Emphasis> to hydroxylapatite by commercial dairy powders and individual milk proteins

The aim of this study was to investigate the inhibitory effect of various dairy powders and milk constituents on the adhesion of a clinical isolate of Streptococcus mutans to hydroxylapatite (HA), an analogue of tooth enamel. Adhesion of a microorganism to a cell surface such as epithelial cells or tooth enamel is considered to be the first step in pathogenesis. Inhibiting this process may have therapeutic effects in vivo. The adherence assays were performed by incubating S. mutans with HA in the presence of each test material for 45 min, followed by centrifugal separation of the HA. Unbound bacteria were then quantified using a fluorescent dye. Sweet and Acid WPC80, buttermilk powder and cream powder were found to very effectively inhibit adherence of S. mutans to phosphate-buffered saline coated HA (PBS-HA). Sodium caseinate and the casein fractions α-,β- and κ-casein were also found to show high levels of anti-adhesive activity. A selection of test materials were assessed using saliva-coated HA (S-HA), and similar trends were observed. The results suggest commercial dairy powders, and certain milk proteins, can inhibit adhesion of S. mutans to HA and may have potential to control dental caries.     

The effect of untreated and enzyme-treated commercial dairy powders on the growth and adhesion of Streptococcus mutans

Dental caries is a common bacterial infection, but the progression of this disease can be delayed by preventing initial attachment of cariogenic bacteria such as Streptococcus mutans to tooth surfaces. This study firstly compares the effect of untreated (UT) and enzyme-treated (ET) dairy powders on the adherence of S. mutans to hydroxylapatite (HA), an analogue of tooth enamel. A fluorescence-based method was used to quantify adherence of S. mutans to HA both in the presence (S-HA) and absence (PBS-HA) of saliva. Secondly, binding of proteins present in the test materials to HA was quantified using bicinchonic acid assays and SDS-PAGE. In addition, the effect of UT and ET dairy powders on growth of S. mutans was examined using an optical-density based assay. UT acid whey protein concentrate (WPC) 80, sweet WPC80, buttermilk powder (BMP) and cream powder (CP) significantly (P < 0.05) inhibited adhesion of S. mutans at ≥31.25 μg mL⁻¹ in the presence and absence of saliva. ET dairy powders were less effective inhibitors of adhesion, but ET sweet WPC80 significantly (P < 0.05) inhibited growth of S. mutans at ≥0.6 mg mL⁻¹. Therefore, due to their adherence- and growth-inhibitory properties, dairy powders may be beneficial in the treatment of dental caries.     

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     

Comparison of functional properties of 34% and 80% whey protein and milk serum protein concentrates

This study compared the functional properties of serum protein concentrate (SPC) with whey protein concentrate (WPC) made from the same milk and with commercial WPC. The experimental SPC and WPC were produced at 34% or 80% protein from the same lot of milk. Protein contents of WPC and SPC were comparable; however, fat content was much lower in SPC compared with WPC and commercial WPC. The effect of drying methods (freeze vs. spray drying) was studied for 34% WPC and SPC. Few differences due to drying method were found in turbidity and gelation; however, drying method made a large difference in foam formation for WPC but not SPC. Between pH 3 and 7, SPC was found to have lower turbidity than WPC; however, protein solubility was similar between SPC and WPC. Foaming and gelation properties of SPC were better than those of WPC. Differences in functional properties may be explained by differences in composition and extent of denaturation or aggregation.     

Rennet coagulation of buffalo milk as affected by some factors

Thrombelastograph was used to measure the rennet coagulation properties of buffalo milk. The combined effect of pH with temperature fat and protein contents, addition of whey protein concentrat (WPC) and sodium chloride on rennet coagulation (r) and clot forming (K₂₀) times were evaluated. The fat content had little effect on r or K₂₀ compared to pH. Increasing temperature from 30 to 40 °C or the protein content of UF milk retentate from 3 to 12% decreased K₂₀ and K₂₀ of buffalo milk. The K₂₀ was greatly affected by the replacement of casein with 10, 20, 30 and 40% WPC while r was less affected. Addition of sodium chloride (2–10%) increased and K₂₀ and the effect was more pronounced at low pH. The relations between the studied factors and r and K₂₀ of buffalo milk were calculated and discussed.     

Physiochemical Properties,Microstructure, and Probiotic Survivability of Nonfat Goats’ Milk Yogurt Using Heat‐Treated Whey Protein Concentrate as Fat Replacer

There is a market demand for nonfat fermented goats’ milk products. A nonfat goats’ milk yogurt containing probiotics (Lactobacillus acidophilus, and Bifidobacterium spp.) was developed using heat‐treated whey protein concentrate (HWPC) as a fat replacer and pectin as a thickening agent. Yogurts containing untreated whey protein concentrate (WPC) and pectin, and the one with only pectin were also prepared. Skim cows’ milk yogurt with pectin was also made as a control. The yogurts were analyzed for chemical composition, water holding capacity (syneresis), microstructure, changes in pH and viscosity, mold, yeast and coliform counts, and probiotic survivability during storage at 4 °C for 10 wk. The results showed that the nonfat goats’ milk yogurt made with 1.2% HWPC (WPC solution heated at 85 °C for 30 min at pH 8.5) and 0.35% pectin had significantly higher viscosity (P < 0.01) than any of the other yogurts and lower syneresis than the goats’ yogurt with only pectin (P < 0.01). Viscosity and pH of all the yogurt samples did not change much throughout storage. Bifidobacterium spp. remained stable and was above 10⁶CFU g^‐1 during the 10‐wk storage. However, the population of Lactobacillus acidophilus dropped to below 10⁶CFU g^‐1 after 2 wk of storage. Microstructure analysis of the nonfat goats’ milk yogurt by scanning electron microscopy revealed that HWPC interacted with casein micelles to form a relatively compact network in the yogurt gel. The results indicated that HWPC could be used as a fat replacer for improving the consistency of nonfat goats’ milk yogurt and other similar products.     

The effect of supplementing goats milk with whey protein concentrate on textural properties of set-type yoghurt

Yoghurt was manufactured from goat's milk and supplemented with 30 g L^?1 of whey protein concentrate (WPC). The textural properties of the yoghurt were evaluated during the shelf‐life of the product and the textural characteristics of yoghurt made from cow's milk were used as a reference. The instrumental analyses used were the puncture test, stress relaxation test and texture profile analysis. The addition of WPC to goat's milk enhanced the textural characteristics of yoghurt. These advantageous attributes included increased firmness, hardness and adhesiveness. These attributes were quantitatively similar (P > 0.05) to those obtained from yoghurt made from cow's milk. In addition, the textural properties were maintained constant throughout the shelf‐life of the product.     

Development of antimicrobial whey protein-based film containing silver nanoparticles biosynthesised by Aspergillus Niger

Applications of whey protein concentrate (WPC)-based films have been limited in the food industry due to their poor mechanical properties. This research aims to evaluate the effect of silver nanoparticles (AgNPs) synthesised by Aspergillus niger on the mechanical and antimicrobial properties of WPC-based films. The biosynthesised AgNPs solution was added into the WPC film formula at the concentration of 0, 0.25 and 1.25 mm . The film samples containing AgNPs inhibited the growth of Staphylococcus aureus, Escherichia coli O157:H7, Salmonella Enteritidis, Listeria monocytogenes, Williopsis saturnus or Aspergillus sydowii with zones of inhibition ranging from 13 to 19.7 mm. Incorporation of AgNPs improved tensile strength and water barrier properties of the films by 84% and 67%, respectively. However, per cent elongation at the break of the film decreased from 37% to 11% by the addition of 1.25 mm AgNPs. This work provides a protocol for preparing improved antimicrobial WPC films with AgNPs.     

Effect of low lactose dairy powder addition on the properties of gluten-free batters and bread quality

Different low lactose dairy ingredients including sodium caseinate (SC), milk protein isolate (MPI), whey protein isolates (WPIS and WPIM) and whey protein concentrate (WPC) were tested in a gluten-free bread formulation and compared to controls with the addition of no dairy ingredient (C) and one dairy ingredient containing lactose, skim milk powder. Rheological characterisation (frequency sweep and creep-recovery) of the batters at 90% water level (WL) suggested that the addition of WPIS, WPIM and WPC significantly decreased G′ and G″ values. SC and MPI had the opposite effect with a significant increase in both these parameters being found (p < 0.05). The WL of the batters was adjusted in order to obtain the same consistency of the batter C at 90% WL. A Power Law model was used to predict the new WL based on single frequency measurements of G* for each sample. The baking analysis demonstrated that the correction of the WL did not show a strong impact in the quality of the breads. Nevertheless, whey proteins demonstrated the ability to increase significantly the specific volume of the breads and decrease the hardness over time (p < 0.05). SC had a negative impact on the specific volume, which led to an increase in crumb hardness (p < 0.05).     

Effects of Ca++, Mg++ and Na+ on Heat Aggregation of Whey Protein Concentrates

Effect of Ca⁺⁺ on the heat aggregation of whey protein concentrates (WPC) was compared with that of Na⁺ and Mg⁺⁺. On the alkaline side of the isoelectric zone, aggregation of WPC was increased by the addition of CaCl₂, MgCl₂ or NaCl, among which CaCl₂ showed the greatest effect. The denaturation temperature of WPC determined by differential scanning calorimetry significantly decreased in the presence of CaCl₂ or MgCl₂, but increased slightly in the presence of NaCl. In the electrophoretic patterns of heated WPC, the most sensitive protein to Ca⁺⁺ was β-lactoglobulin.     

Interfacial dynamic properties of whey protein concentrate/polysaccharide mixtures at neutral pH

The effect of two non-surface active polysaccharides (sodium alginate, SA, and λ-carrageenan, λ-C) in the aqueous phase on the surface dynamic properties (dynamic surface pressure and surface dilatational properties) of a commercial milk whey protein concentrate (WPC) adsorbed film at the air–water interface has been studied. A whey protein isolate (WPI) was used as reference. The WPC and WPI concentration (at 1.0% wt), temperature (at 20 °C), pH (7), and ionic strength (at 0.05 M) were maintained constant, while the effect of polysaccharide (PS) was evaluated within the concentration range 0.0–1.0% wt. The surface dynamic properties of the adsorbed films were measured in an automatic pendant drop tensiometer. At short adsorption time and in the presence of PS, the rate of diffusion of WPC to the interface was affected by the interactions with PS in the aqueous phase, which could limit protein availability for the adsorption. On the other hand, at long-term adsorption, the magnitudes of the molecular penetration and configurational rearrangement rates of WPC in mixed systems (WPC/PS) reflected the viscoelastic characteristics of the adsorbed films. The attractive interactions between WPC and PS and/or the WPC aggregation in the presence of PS, which depend on the proper polysaccharide and its concentration in the aqueous phase, have an effect on the adsorption kinetic parameters, the amount of WPC adsorbed at the air–water interface, and the dilatational viscoelastic characteristics of WPC/PS mixed systems.     

Development of a fermented goat's milk containing probiotic bacteria

A set-type fermented milk manufactured from goat's milk was developed. Optimal curd tension was achieved by supplementation of milk with skim milk powder and whey protein concentrate (WPC). Milk was fermented employing a commercial probiotic starter culture (ABT-2), which contained Streptococcus thermophilus ST-20Y, Lactobacillus acidophilus LA-5, and Bifidobacterium BB-12. Supplementation of milk with 3% WPC reduced fermentation time by 2 h due to the increase in viable counts of S. thermophilus and Bifidobacterium by 0.3 and 0.7 log units, respectively. Addition of WPC increased the protein content (1%) as well as potassium and magnesium content (0.3 and 0.02 g kg⁻¹, respectively). Increase of the protein content led to an increase in the apparent viscosity and gel firmness of the product, and at the same time whey syneresis was reduced. As a consequence, the product received a high score for appearance, taste, aroma, texture and overall acceptance.     

ENZYMATIC HYDROLYSIS OF WHEY PROTEINS BY TWO DIFFERENT PROTEASES AND THEIR EFFECT ON THE FUNCTIONAL PROPERTIES OF RESULTING PROTEIN HYDROLYSATES

Whey protein concentrate (WPC 80) was hydrolyzed by Alcalase 2.4 L and Protamex to 5, 10, 15 and 20% degree of hydrolysis (DH). WPC 80 and its hydrolysates were analyzed, compared and used for measuring some functional properties. All hydrolysates were different from WPC 80 in protein, moisture and ash content. Free amino groups and protein solubility increased with increasing DH. The peptides produced by hydrolysis had smaller molecular sizes, and their average molecular weight decreased as the DH increased. Except hydrolysates generated by Alcalase 2.4 L at 5% DH, all others showed poor emulsifying and foaming properties compared with unhydrolyzed WPC 80. Gelation properties of WPC 80 and its hydrolysates were different. The global amino acid compositions did not differ significantly between the different hydrolysates, and they were very close among WPC 80 and its hydrolysates except for Methionine, Glycine, Histidine and Valine.     

Microstructure and texture of white fresh cheese made with canola oil and whey protein concentrate in partial or total replacement of milk fat

A control white fresh cheese was prepared from milk containing 24 g milk fat (MF) L⁻¹, and nine white fresh cheese-like products were made by partial or complete substitution of milk fat by whey protein concentrate (WPC) and/or canola oil (CO) emulsified with an emulsifiers blend (EB) made of polyoxyethylene sorbitan monostearate (P), sorbitan monostearate (S) and glycerol monostearate (G) in 0.5:0.2:0.3 ratio. The textural characteristics and microstructure of the cheeses were assessed by Instrumental Texture Profile Analysis and Scanning Electron Microscopy. Polynomial models were obtained that estimated the composition and texture characteristics of the cheeses as function of the MF, EB (indirectly CO) and WPC concentrations in the cheese milk. CO incorporation promoted an open microstructure in the cheese, while WPC favoured a close and compact network made of short linking strands of milk proteins.MF, EB and WPC contributed positively to all the textural characteristics of the cheeses.     

Determination of the effect of dairy powders on adherence of Streptococcus sobrinus and Streptococcus salivarius to hydroxylapatite and growth of these bacteria

Dental caries is a highly prevalent disease caused by colonisation of tooth surfaces by cariogenic bacteria, such as Streptococcus sobrinus and Streptococcus salivarius. Reducing initial adherence of such bacteria to teeth may delay onset of caries. Many foods, such as milk, can inhibit microbial adherence. In this investigation, the effect of untreated (UT) and enzyme-treated (ET) dairy powders on adherence of S. sobrinus and S. salivarius to hydroxylapatite (HA), an analogue of tooth enamel, was examined. Untreated (UT) acid whey protein concentrate (AWPC) 80 inhibited streptococcal adherence to phosphate-buffered saline-coated HA (PBS-HA) and saliva-coated HA (S-HA) by >80% at ?31.25 μg mL⁻¹. UT sweet WPC80, buttermilk powder and cream powder also significantly reduced adherence (P < 0.05). Enzyme-treatment of all dairy powders reduced their anti-adhesion activity. However, ET sweet WPC80 significantly inhibited growth of these streptococci (P < 0.05) at ?0.6 mg mL⁻¹. Therefore, dairy powders may reduce progression of dental caries by their anti-adhesion and/or antibacterial activity.     

Effect of incorporating whey protein concentrate into stevia‐sweetened Kulfi on physicochemical and sensory properties

In 50% sugar replaced with 0.05% stevia‐added Kulfi, whey protein concentrate (WPC) at 0, 2, 3 and 4% levels were separately incorporated. Increase in WPC level resulted in significant (P < 0.05) decrease in freezing point, melting rate, hardness and moisture percentage and significant (P < 0.05) increase in specific gravity, protein percentage and total calorie content in the product. Among 0, 2, 3 and 4% WPC‐added Kulfi, 3% WPC‐added Kulfi was adjudged as best by a panel of judges. Above 3% WPC addition, the product was very soft and possessed undesirable whey flavour.     

Effect of Flavourzyme® on Angiotensin‐Converting Enzyme Inhibitory Peptides Formed in Skim Milk and Whey Protein Concentrate during Fermentation by Lactobacillus helveticus

Angiotensin‐converting enzyme inhibitory (ACE‐I) activity as affected by Lactobacillus helveticus strains (881315, 881188, 880474, and 880953), and supplementation with a proteolytic enzyme was studied. Reconstituted skim milk (12% RSM) or whey protein concentrate (4% WPC), with and without Flavourzyme^® (0.14% w/w), were fermented with 4 different L. helveticus strains at 37 °C for 0, 4, 8, and 12 h. Proteolytic and in vitro ACE‐I activities, and growth were significantly affected (P < 0.05) by strains, media, and with enzyme supplementation. RSM supported higher growth and produced higher proteolysis and ACE‐I compared to WPC without enzyme supplementation. The strains L. helveticus 881315 and 881188 were able to increase ACE‐I to >80% after 8 h of fermentation when combined with Flavourzyme^® in RSM compared to the same strains without enzyme supplementation. Supplementation of media by Flavourzyme^® was beneficial in increasing ACE‐I peptides in both media. The best media to release more ACE‐I peptides was RSM with enzyme supplementation. The L. helveticus 881315 outperformed all strains as indicated by highest proteolytic and ACE‐I activities.     

Immunoreactive properties of peptide fractions of cow whey milk proteins after enzymatic hydrolysis

Commercial whey protein concentrate (WPC) was hydrolysed with either Alcalase 2.4 FG (Novo Nordisk), or papain (Sigma) (in one‐step process) or with two enzymes (in two‐step process) to determine the changes in the immunoreactivity of α‐lactalbumin and β‐lactoglobulin. Enzymatic hydrolysis of WPC was performed by pH‐stat method. Hydrolysates were analysed using sodium dodecyl sulphate‐polyacrylamide gel electrophoresis, immunoblotting and size‐exclusion chromatography (SE‐HPLC). Immunoreactive properties of peptide fractions separated from the hydrolysates by fast protein liquid chromatography (FPLC) were determined using dot‐immunobinding and enzyme‐linked immunosorbent assay (ELISA) methods. Finally the sensory analysis was used to confirm organoleptic changes resulting from the application of different enzymes. The ‘two‐step’ process was observed to be the most effective however allergenic epitopes were still present, as it was found by ELISA with anti‐α‐la and anti‐β‐lg antibodies. The addition of papain as the second enzyme in the hydrolysis process contributed to the improvement of the sensory properties of WPC hydrolysate as compared with the Alcalase hydrolysate. Alcalase‐papain partially hydrolysated WPC can be found a promising base for production of the tolerogenic formula.     

EXTRUDED CORN MEAL AND WHEY PROTEIN CONCENTRATE: EFFECT OF PARTICLE SIZE

Blends of whey protein concentrate (WPC) and corn meal, which were separated into four particle fractions (residual on a #30 screen, #40 screen, #60 screen and through a #60 screen), were extruded at two moisture conditions (23 and 28%) to determine the effects of particle size on the extrudate properties. Smaller particle size fractions exhibited increased solubility and significantly higher viscosity both with and without added protein. When WPC was added to the corn meal, a large reduction in paste viscosity was observed regardless of the particle size. The blend with similar particle size distributions of corn meal and WPC had a significantly higher viscosity than the other blends. The expansion ratio, porosity and breaking strength of this blend, when extruded at the lower moisture content, were improved to the extent that they behaved similarly to extrudate made from corn meal alone.