B.T. O'Kennedy's research while affiliated with University of Limerick and other places

Publications (69)

Article
Oxidative analysis of omega-3-enriched fat spreads (oil-in-water-in-oil, O/W/O emulsions) was carried out using conventional lipid oxidation methods (lipid hydroperoxide and p-Anisidine values) and compared with volatile compound analysis using SPME-GC/MS and sensory evaluation. Fat spreads were produced using novel double-emulsion technology. More...
Article
Full-text available
Oil-in-water (O/W) emulsions were prepared using different concentrations of camelina or sunflower oil. Sodium caseinate was used as the emulsifier and dried glucose syrup as the wall material. Emulsions were subsequently spray dried to yield high-fat powders (71.7-85.0%). Emulsification and microencapsulation of bulk oils decreased their level of...
Article
Full-text available
This study examined the effectiveness of fat and water soluble antioxidants on the oxidative stability of omega (ω)-3 rich table spreads, produced using novel multiple emulsion technology. Table spreads were produced by dispersing an oil-in-water (O/W) emulsion (500 g/kg 85 camelina/15 fish oil blend) in a hardstock/rapeseed oil blend, using sodium...
Article
Full-text available
The intake of sodium in modern western diet is excessive, with potentially harmful effects on health. Consequently, there is a drive to reduce the sodium content of foods. A major source of sodium in processed cheeses (PCs) is the added emulsifying salts (sodium phosphates or citrates) which play a key role in product formation and stabilisation. T...
Article
The effects of milk protein type, formulation and storage were investigated in model bar systems to gain improved insight into deteriorative, textural changes. Texture analysis, water activity measurements, confocal laser scanning microscopy and Fourier transform infrared (FT-IR) spectroscopy were used to monitor interactive physical and chemical c...
Article
This chapter discusses the commercial methods used to separate and concentrate the casein from the other components in bovine milk. The family of casein ingredients produced are discussed in terms of casein structural and physico-chemical properties which resulted in both the production of the ingredient and functionality of the ingredient in vario...
Article
The formation of Cu–alginate complexes and the impact of free or bound copper on the oxidative stability of model water/oil mixtures containing edible sunflower or corn oil were examined. Equilibrium dialysis showed that copper binding capacity of alginate increased proportionally with copper concentration and the binding was rapid. The results ind...
Article
The effect of κ-carrageenan concentration (0-7.5gkg−1) on the rheology, microstructure, texture and oxidative stability of water-in-oil (W/O) spreads (600gfatkg−1 emulsion) was examined over 60 days storage time. Results showed that increasing the κ-carrageenan concentration to 7.5gkg−1 significantly increased the viscosity of the aqueous phase (to...
Article
The stability to heat treatment (85°C, 10 min) at pH 6.0 of β-lactoglobulin (β-lg; 0.5%) when combined with 0.5% sodium caseinate was examined in increasing levels of simulated milk ultrafiltrate (SMUF). Sodium caseinate had a stabilising influence on β-lg resulting in particle size reductions on heating (size reduced from 406 to 151 nm in SMUF ×0....
Article
This chapter includes a brief introduction to the dairy ingredients available for incorporation into a wide range of food products, their functionality in isolation and their resultant functionality in food systems.
Article
The stability of β-lactoglobulin (β-lg)/micellar casein (MC) mixtures was examined on heating at pH 6.0 in increasing levels of lactose-free simulated milk ultrafiltrate (SMUF). Heated β-lg associated with MC to form stable particles (up to 771 nm in size in SMUF × 0.5). Higher levels of SMUF induced reductions in the charge on particles, resulting...
Article
Full-text available
Calcium content of natural cheese has a major impact on its physical properties. The objective of this study was to investigate how the calcium content of natural cheese affects the functionality of processed cheese (PC). The PCs were made from Cheddar cheese with an intact casein content of 89 g·100 g−1 total casein and with calcium/casein ratios...
Article
The aim of this research was to investigate the effect of mineral fortification on the textural and oxidative stability of reduced-fat spreads produced using κ-carrageenan. Model systems were prepared containing varying amounts of zinc, copper, and iron. The hardness of the spreads stored at 5°C and 25°C was assessed over time using a penetrometer...
Article
The denaturation/aggregation behaviour of heated (78 °C, 10 min) β-lactoglobulin (1%, w/w) was examined as a function of heating pH (5.0–7.0), in the presence of different salts. Heating β-lactoglobulin in the presence of calcium (5 mm) significantly increased the level of aggregated protein at most heating pH values, compared to heating in water o...
Article
Work was undertaken to investigate the effect of copper and Iron fortification (up to 15 mM) on the rheology and firmness of water-in-oil spreads (60 % fat) produced using 0.25 % κ-carrageenan. The apparent viscosity of the aqueous phase (10.9 mPa s) was significantly reduced by fortification with 15mM copper (4 mPa s) or iron (3.2 mPa s) at 60°C....
Article
The viscosity, heat stability, acid and rennet gelling properties of model milk systems containing 0-100% replacement of the fat with microparticulated whey protein (MWP; LeanCreme™) were examined. The viscosity of milk (∼1.7 mPa.s) before and after heating was unchanged by the addition of MWP. The control milk had peak heat stability (12 min at 14...
Article
The aim of this study was to investigate the response of κ-carrageenan to the ionic environment which prevails in milk protein-containing food systems.The effect of ionic strength in the form of calcium chloride, sodium chloride, potassium chloride, sodium citrate or simulated milk ultrafiltrate (SMUF) was examined on the relative viscosity, zeta p...
Article
Gluten substitution in the production of bread suitable for celiacs is challenging due to the unique viscoelastic properties of gluten. Caseinates are widely used for their functional properties, and in this study a production protocol for an aggregated casein-based ingredient fortified with Ca was developed. It was envisaged that the S-S bonds tha...
Article
Work was undertaken to investigate the effect of zinc fortification (up to 15mM) on the rheology, firmness and microstructure of water-in-oil spreads (60% fat) produced using 0.25% κ-carrageenan. Increasing levels of zinc from 0 to 15mM caused a significant reduction in the apparent viscosity of the aqueous phase from 10.9 to 7mPas at 60°C but resu...
Chapter
The science and technology of hydrocolloids used in food and related systems has seen many new developments and advances over recent years. This book presents the latest research from leading experts in the field. Some of the topics covered within this book include biochemical characterisation, the use of antibodies, immunostaining and enzyme hydro...
Article
Work was undertaken to examine the effect of pH, ionic strength and temperature on the protein–polysaccharide complexation between the milk protein 1% (w/w) β-lactoglobulin (β-lg) and 0.1% (w/w) chitosan (mw=75–150 kDa). The zeta potential of mixtures of β-lg and chitosan changed from +34.5 mV at pH 4.0 to a point of zero charge at pH 7.4. At pH 5....
Article
A production protocol for an aggregated casein mass has been developed and the effect of NaCl concentration on the yield, texture, and rheology has been evaluated. Concentrations of NaCl up to 20mM lead to greater yield however, higher concentrations were detrimental. A similar pattern was observed for adhesiveness, one of the texture profile param...
Article
The effects of calcium and N-ethylmaleimide addition on the heat-induced denaturation/aggregation of β-lactoglobulin at neutral pH were examined. Aggregation of unfolded β-lactoglobulin was found to be rate limiting on heating aqueous protein solutions, while stoichiometric additions of calcium indicated that the unfolding reaction was limiting. In...
Article
Imitation creamer formulations were spray dried and agglomerated on a pilot scale tall-form drier in order to evaluate the stability of the resulting powders when added to hot aqueous coffee solutions. The study explored the effects of different protein ingredients (sodium caseinate; milk protein concentrate; whey protein concentrate; milk proteina...
Article
The effects of various processing parameters on the rennet coagulation properties of milk were assessed. Using low amplitude oscillation rheometry, the coagulation properties were monitored by measurement of the elastic shear modulus, G', as a function of time, t, from rennet addition; Gapos; was taken as a measure of curd firmness. The Scott-Blair...
Article
Fourteen processed cheeses varying in emulsifying salt and moisture contents were evaluated by three-point bending and texture profile analysis (TPA) based on two-bite compression testing. Sensory texture analysis was also carried out by a trained panel. Partial least squares regression was used to predict the sensory parameters from both three-poi...
Article
Textural characteristics of process cheeses varying in emulsifying salt (disodium phosphate), protein and moisture contents were evaluated by rheological compression using texture profile analysis and by sensory evaluation. The primary objective of this study was to predict sensory textural parameters using instrumental rheological parameters. All...
Article
The gelation characteristics of β-lactoglobulin, whey protein isolate and whey protein concentrate at varying levels of protein (6–11%), sodium chloride (25–400 mM), calcium chloride (10–40 mM) and pH (4.0–8.0) were studied in a multifactorial design. Small scale deformation of the gels was measured by dynamic rheology to give the gel point (°C), c...
Chapter
Food macromolecules play a crucial role in the formulation of a wide range of food products such as beverages, bread, cheese, dressings, desserts, ice-cream, and spreads. This book presents the very latest research in the area and is unique in covering both proteins and polysaccharides in the same volume. Specifically it describes recent experiment...
Article
Acid gelation, turbidity and particle size development of dispersions of sodium caseinate and other protein fractions were studied. Sodium caseinate dispersions became particulate prior to the onset of gelation. Casein particles had enhanced stability to gelation in the presence of sodium chloride. Removal of the hydrophilic part of the κ-casein mo...
Article
The ability of alphas1/beta-casein and micellar casein to protect whey proteins from heat-induced aggregation/precipitation reactions and therefore control their functional behavior was examined. Complete suppression (>99%) of heat-induced aggregation of 0.5% (w/w) whey protein isolate (pH 6.0, 85 degrees C, 10 min) was achieved at a ratio of 1:0.1...
Article
Two sets of Cheddar cheese were made in which the milk protein level (%, wt/wt) was increased from 3.3 (Control A, CA) to 3.6 (set A) or from 3.3 (control B, CB) to 4.0 (set B) by the addition of phosphocasein (PC), milk protein concentrate (MPC), or freshly prepared ultrafiltered milk retentate (UFR). The cheeses were denoted CA, PCA, MPCA, and UF...
Article
The heat-induced denaturation behaviour of 1% (w/w) β-lactoglobulin (β-lg) in water in the pH range 5.0-7.0 was examined using reversed-phase high performance liquid chromatography. The two variants β-lg A and β-lg B existed in the unheated solution at pH 7.0 in the ratio of 0.83 β-lg A/B. At low pH (5.0 - 5.5) the A variant was preferentially dena...
Article
This work investigated the effect of transglutaminase on (1) micellar casein (phosphocasein) suspensions at pH 6.7; (2) gel formation at pH 4.6; and (3) viscosity of the subsequently produced sodium caseinates. Micellar casein (25 g protein·kg-1 in simulated milk ultrafiltrate, pH 6.7) was incubated with and without 1% microbial transglutaminase (T...
Article
Re-micellised casein was prepared by adding various calcium and phosphate salts to acid casein followed by heating and dispersing in distilled water or simulated milk ultrafiltrate (SMUF). The rheological properties, solubility, particle size, ethanol stability and heat stability of the re-micellised acid casein were examined in water or SMUF and c...
Article
The microstructural and rheological properties of glucono-delta-lactone induced acid casein gels made from micellar casein dispersed in water and in lactose-free simulated milk ultrafiltrate (SMUF) containing 40, 70, 100 and 200% of the salts normally present in milk were studied. Confocal scanning laser microscopy (CSLM) and low amplitude oscillat...
Article
The heat-induced denaturation/aggregation of bovine β-lactoglobulin (β-lg) A and B, dispersed at pH 6.6 in various salt conditions (NaCl and CaCl2), was studied at 85°C by High-performance Gel Permeation Chromatography. Results confirmed earlier studies (Croguennec, Bouhallab, Mollé, O’Kennedy, & Mehra (Biochem. Biophys. Res. Commun. 301 (2003) 465...
Article
The effects of shearing milk, blending with early lactation milk and increasing the immunoglobulin content of creams with subsequent heating on the whipping properties of creams were quantified. As the stirring time of the milks increased, the free fat content of the creams increased, the whip time and firmness decreased and the over-run increased...
Article
The objective was to produce spray-dried milk powders for assessment subsequently in chocolate. Milks were ultrafiltered to increase their protein content (3.08–5.33g100g−1), concentrated to different solids levels (42.8–52.3g100g−1) and spray-dried to produce powders (26–59g100g−1 fat). The relationships between the milk protein content, concentra...
Article
The effects of selected properties of spray-dried milk fat powders on chocolate were determined. Milk powders produced from control or ultrafiltered (UF) milks with various levels of fat were blended with skim milk powder to give a standard 26 g fat 100 g−1 powder. Particle size of the chocolate mixes after refining decreased as the fat content and...
Article
The role of the free sulfhydryl group of beta-lactoglobulin in the formation of a stable non-native monomer during heat-treatment of beta-lactoglobulin solutions was investigated. Two concomitant events occurred at the earlier stage of heating: unfolding of native globular monomer and intramolecular sulfhydryl/disulfide exchange reaction. Thus, two...
Article
High-fat and skim-milk powders were produced under constant processing conditions from Spring and Autumn herd milks. The influence of the seasonal variation in protein and solid-fat contents at 10 °C of these milks on some properties of the milk powders was determined. The free-fat content and the median particle size of high-fat milk powders were...
Article
The relationships between some spray-dried high-fat milk powder properties and the rheology of milk chocolate at the end of conching, and its final hardness were determined. Eleven spray-dried high-fat milk powders with free-fat concentrations of 40 to 96 g/100 g fat, solid fat concentrations at 10 °C of 39 to 56 g/100 g, powder median particle siz...
Article
The composition and rennet coagulation characteristics of milk from conventional dairy cattle breeds (Irish Friesian, IF; US Holstein, USH) and dual-purpose breeds (Montebeliarde, M; Normande, N) were assessed under Irish pasture-grazing conditions. Milk samples were collected from 10 cows of each breed approximately 100 days after calving. Milk fr...
Article
The application of high pressure as an alternative to heat treatment in the acid-set gelling of milk proteins was studied using a "simulated yogurt milk" (SYM) system, containing phosphocasein and whey protein isolate (WPI) in a ratio of 4:1. Gels were made by acidification of SYM with glucono-δ-lactone (GDL) at 40 °C to pH 4.6 and their properties...
Article
An objective of the present study was to determine the effects of protein interactions on acid gelation behaviour at the higher concentrations encountered in fresh cheeses. A fresh cheese model was created by means of chemical acidification (glucono-δ-lactone) of 120 g L−1 protein solutions prepared from native phosphocasein, sodium caseinate and w...
Article
Full-text available
Microencapsulation of fish oil was achieved by spray-drying homogenized emulsions of fish oil using 3 different types of casein as emulsifier and lactose as filler. As the degree of aggregation of the casein emulsifier increased, the vacuole volume of the microencapsulated powders decreased. The shelf life of the powders increased as the degree of...
Article
Full-text available
A manufacturing process for the preparation of a novel casein-type product milk proteinate, incorporating casein and whey protein was developed and patented. A contrasting novel ingredient, based on recovery of casein in its native form (phosphocasein) from milk, was demonstrated using a microfiltration process.This ingredient excelled in terms of...
Article
Calcium and phosphate (10-30 mM) were stabilised to precipitation using pre-denatured whey protein (3% w/w, 90°C for 30 min). As the calcium phosphate/protein ratio increased there was a corresponding increase in the turbidity of the system, which was correlated with an increase in average particle size of the protein-calcium phosphate aggregates....
Article
The exceptionally high stability of sodium caseinate dispersions to ethanol was compromised by the presence of NaCI as evident from turbidity increases and precipitation at ethanol concentrations of 30% and 53% (v/v), respectively. Apparent pH values of 7.31 and 7.7 were obtained in the presence and absence, respectively, of NaCI at 53% (v/v) ethan...
Article
Milk powders (10 kg of high-fat and 60 kg of skim-milk powder) were produced under constant processing conditions from spring and autumn milks. The influence of seasonal variation in protein and solid-fat contents at 10 °C of these milks on selected properties of milk powders was determined. The free-fat content and the median particle size of high...
Article
Caseins and denatured whey proteins exhibit acid gelation behaviour when examined individually. In a typical dairy acid gel such as yoghurt, heat-induced interaction between the 2 major protein groups is also taking place. The extent to which such interactions affect acid gelation was investigated using a model yoghurt milk system which combined na...
Article
Denatured whey proteins (3% w/w) were shown to stabilise 30 mM calcium and phosphate. Subsequent stability to heat was dependent on the initial pH of the calcium phosphate/whey protein mixture. At 6.4 < pH < 6.7, stand-up gels were formed on heating to 90 °C for 30 min. At pH > 6.7 no gelation was evident. The degree of unfolding/aggregation of whe...
Article
Numerous opportunities for the separation and fractionation of milk and whey components are presented as a result of continuing developments in filtration membranes modules and processes. The preparation of sufficient quantities of selected protein groups for functionality studies and food application tests requires considerable amounts of starting...
Article
The effects of homogenisation conditions (pressure and number of passes) and emulsion composition (fat, whey protein, lactose, salts and water) on the properties of emulsions and microencapsulated milk fat powders were measured. The emulsions were assessed by fat globule diameter and size stability over time. The properties of the powders measured...
Article
The rheological characterisation of thermally-induced caseinate-gelatin gels was carried out on a multicomponent system containing Na caseinate (2.8 to 14.8 g/100 g), gelatin (1.2 to 3.0 g/100 g), NaCl (0.0 to 1.5 g/100 g) and CaCl2 (0 to 7 mg Ca/g Na caseinate) at pH values in the range 6.1 to 6.8. Gelatin increased the gel point, gel consistency...
Article
Cheddar cheese was manufactured on three separate occasions over a two week period from milk collected from two mid-lactation, spring-calving, Holstein–Friesian herds (n=11) containing similar casein levels, having phenotype AA or BB for κ-casein genetic variant. κ-Casein variant did not significantly (P>0.05) influence the casein content or gross...
Article
Reduced fat milks were pasteurized, for 15 s, at temperatures ranging from 72 to 88°C to give levels of whey protein denaturation varying from ˜ 3 to 35%. The milks were converted into reduced fat cheddar cheese (16–18% fat) in 500 litre cheese vats; the resultant cheese curds were milled at pH values of 5.75 and 5.35. Raising the milk pasteurizati...
Article
The rheological characterization of stirred yogurt with added milk fat, Na caseinate (or micellar casein) and gelatin (4 Bloom strengths), starch or a xanthan gum/LBG 50:50 mixture was carried out. Dynamic and shear values were measured at 8°C and syneresis at 4°C. Consistency (k* and k) and syneresis were more frequently influenced by the composit...
Article
Full-text available
In order to extend our knowledge of factors important in the surface activity of melittin, cysteine was substituted for lysine-21 and lysine-21/glutamine-25 in a pair of synthetic peptide analogues. The first of these changes resulted in only modest effects on secondary structure (determined in 50% trifluoroethanol), emulsification and surface tens...

Citations

... Burgess and Carless (1985) pointed out to the potential use of gelatin/gelatin complex for microcapsules preparation. Keogh, Galazka, O'Kennedy, and O'Callaghan (1998) investigated rheological properties of thermally-induced caseinate-gelatin gels. ...
... In addition, when increasing the CAS content in the copolymers (from 30 to 50, and 70%), a decrease on the DCR plateau was observed, suggesting that the thermally-induced assembly process could be hindered by this hydrophilic macromolecule, which is negatively charged at pH 7.4 (the isoelectric point of CAS is 4.6-4.8) [40]. Similar results were observed for each graft copolymer in simulated endo/lysosomal conditions (see Fig. S5 of the SI). ...
Citing article
... As a result of the research, it was reported that severe heating causing protein denaturation, lowering the pH or the use of k-carrageenan instead of icarrageenan caused excessive gelation. Alexa et al. (2009) examined the ionic responses of k-carrageenan in media containing milk protein. In the study, the effects of ionic strength on the properties of k-carrageenan in the presence of calcium chloride, sodium chloride, potassium chloride, sodium citrate or simulated milk ultrafiltrate were investigated. ...
... The total surface of large particles is smaller, which makes it easier to cover them, thereby allowing for better results with roller-dried milk. These results are supported by the research of Twomey et al. [17] An interesting combined effect of milk powder and emulsifiers is observed when the application of lecithin-PGPR blend is compared to that of CITREM 2in1. Namely, the lecithin-PGPR action is similar to that of CITREM 2in1-in that it reduces both µ CA and τ CA . ...
... Milk proteins are highly functional ingredients characterized by a significant nutritional value. They swell in a high level and are able to build up a network [11,12]. Next to the functional benefits, gluten-free products with milk proteins are affluent in calcium and proteins, and, thus, enriched in essential amino acids like lysine, methionine and tryptophan [13]. ...
... In dairy science and technology, aggregation is probably the more important phenomenon, as uncontrolled aggregation can lead to destabilisation. αS-, β-and κ-casein have been shown to exhibit chaperone activity against aggregation [199]. The presence of caseins provided stabilization of whey protein aggregates during heating. ...
... Another approach to improving the heat stability of various high-protein dairy products containing whey proteins is microparticulation (Çakır-Fuller, 2015;Ipsen, 2017;Mounsey, O'Kennedy, Corrigan, Kelly, & O'Callaghan, 2009;Saglam, 2011). The microparticulates are whey protein aggregates with particle sizes ranging from 1 to 10 μm. ...
... Milk protein concentrate (MPC) refers to a partially delactosed, total milk protein powder that retains a casein-to-whey protein ratio similar to that of skim milk (Mistry and Hassan, 1991). MPCs are classified based on their protein concentration, which may range from 42% to 85% protein (O'Kennedy, 2009). For example, MPC50 refers to an MPC with $50% dry matter being protein, and MPC80 has a protein concentration of $80% dry matter. ...
... Guinee and O'Kennedy [27] reported discrepancies among studies that tested consumer liking for different salt replacement ratios. According to these authors, less than 50% of NaCl could be substituted with KCl, without negative effect on sensorial acceptability of cheeses. ...
... Instead, the rise in signal for calcium in the skim milk fouling layer further from the surface in Fig. 10 indicates that initial adhesion by proteins can occur when they have a strong interaction with the membrane polymer, while calcium is involved in bridging proteins to assemble the complete fouling layer. Also, it is worth pointing out that the calcium phosphate signal by IR was stronger in the whey fouling layer supporting the concept that whey proteins form aggregates at the membrane that may have increased ability to bind calcium phosphate due to the exposure of free carboxyl groups [43,44]. These interactions then result in a protein/calcium phosphate complex. ...