Effects of caseinate, whey and milk powders on the texture and microstructure of emulsified chicken meat batters

The effects of adding dry caseinate, whole milk, skim milk, regular, and modified whey protein powders, at a level of 2 g/100 g, to meat batters were studied. All dairy additives, except for the regular whey, significantly reduced cook loss (30-50% reduction). Caseinate and modified whey formed distinct dairy protein gel regions within the meat batters, as revealed by light microscopy. Both also contributed more to enhancing the textural properties of the meat batters compared to the other dairy proteins; i.e., increasing texture profile analysis fracturability, and hardness, respectively. Overall, the most cost-effective ingredient appeared to be the modified whey, which also provided the best moisture retention.     

Effect of regular and hydrolysed dairy proteins on texture,microstructure and colour of lean poultry meat batters

The use of 2% milk protein isolate (MPI), and some of its fractions which included caseinate, whey protein isolate (WPI), two whey protein hydrolysates (5.2% and 8.5%; WPH‐I and WPH‐II respectively) and β‐lactoglobulin (β‐lac) was evaluated in lean chicken breast meat batters. Adding caseinate and MPI resulted in the highest fracture force values, and caseinate also provided higher yield compared with the control. Both proteins were observed to form distinct protein islands embedded within the meat protein matrix, which appeared to enhance the gel structure. The two hydrolysates provided the highest yield compared with all other treatments. However, adding WPH‐II also resulted in the lowest fracture force and hardness values, while WPH‐I provided similar values to the control. The low hardness value could be explained by the light micrograph which showed WPH‐II interfering with the binding of the meat proteins. The WPI and β‐lac provided similar yield, fracture and hardness values as the control. The colour of the products was most affected by the WHP‐I and WHP‐II; both resulted in lower lightness, yellowness and overall spectra reflectance curves. A cost analysis revealed that caseinate addition was the most economical in this lean meat system.     

Maillard Reaction Products as Encapsulants for Fish Oil Powders

The use of Maillard reaction products for encapsulation of fish oil was investigated. Fish oil was emulsified with heated aqueous mixtures comprising a protein source (Na caseinate, whey protein isolate, soy protein isolate, or skim milk powder) and carbohydrates (glucose, dried glucose syrup, oligosaccharide) and spray‐dried for the production of 50% oil powders. The extent of the Maillard reaction was monitored using L*, a*, b* values and absorbance at 465 nm. Encapsulation efficiency was gauged by measurement of solvent‐extractable fat and the oxidative stability of the fish oil powder, which was determined by assessment of headspace propanal after storage of powders at 35 °C for 4 wk. Increasing the heat treatment (60 °C to 100 °C for 30 to 90 min) of sodium caseinate‐glucose‐glucose syrup mixtures increased Maillard browning but did not change their encapsulation efficiency. The encapsulation efficiency of all heated sodium caseinate‐glucose‐glucose syrup mixtures was high, as indicated by the low solvent‐extractable fat in powder (<2% powder, w/w). However, increasing the severity of the heat treatment of the sodium caseinate‐glucose‐glucose syrup mixtures reduced the susceptibility of the fish oil powder to oxidation. The increased protection afforded to fish oil in powders by increasing the temperature‐time treatment of protein‐carbohydrate mixtures before emulsification and drying was observed irrespective of the protein (sodium caseinate, whey protein isolate, soy protein isolate, or skim milk powder) and carbohydrate (glucose, glucose/dried glucose syrup, or oligosaccharide/dried glucose syrup) sources used in the formulation. Maillard reaction products produced by heat treatment of aqueous protein‐carbohydrate mixtures were effective for protecting microencapsulated fish oil and other oils (evening primrose oil, milk fat) from oxidation.     

Manufactore of Ras cheese from ultrafiltered milk supplemented with caseinates

Whole cow's milk was ultrafiltered (conc. Factor 5), sodium and calcium caseinate were added to the milk retentate at the rate of 0.5 and 0.75% (w/w) of the milk. Ras cheese was made from milk retentate supplemented with different levels of caseinate salts, as well as unsupplemented retentates, and compared with Ras cheese made by the traditional method. Retentate supplemented with 0.5% Na and Ca caseinate was suitable for Ras cheese-making with limited whey drainage, supplementation of retentate with 0.75% Ca caseinate gave defective cheese at the end of ripening, while Na caseinate increased soluble N and free fatty acids in the cheese. Organoleptic scoring showed that supplementation with Na caseinate enhanced cheese ripening.     

Preliminary observations on the effects of milk fortification and heating on microstructure and physical properties of stirred yogurt

The aim of this work was to study how milk fortification and heating affect yogurt microstructure (micellar characteristics, protein network) and physical properties (viscosity, water-holding capacity (WHC), and graininess). Milk was fortified with skim milk powder (control), whey protein concentrate (WPC), caseinate, or a mixture of caseinate and whey protein. Two heat treatments were applied, giving average whey protein denaturation levels of 58% and 77%. For caseinate-enriched yogurts, the heating effect was negligible. When milk was enriched with WPC, heating led to a high level of cross-linking within the gel network. Heating increased yogurt viscosity and WHC, but also graininess. When milk was fortified with a blend of WPC and caseinate giving a whey protein-to-casein ratio of 0.20, the yogurt viscosity was greatly improved, while graininess was kept low. The results show a relationship between micelle solvation and yogurt microstructure, as well as micelle size in milk base and yogurt graininess.     

Effect of Transglutaminase on Physicochemical Properties of Set-style Yogurt

In this study, the effect of some ingredients such as skimmed milk powder, whey, sodium caseinate, calcium caseinate, whey protein concentrate (35, 60 kg/100 kg dry solids), whole milk powder, condensed milk and transglutaminase (TGase) on the properties of set-style yogurt was investigated. These protein and dry matter sources (2%) and TGase (1 U/g milk protein) were added into pasteurized milk and incubated prior to fermentation for 2 h at 40°C. After fermentation, enzyme action was stopped by heating for 1 min at 80°C. The control groups were conducted with addition of these materials into milk without TGase. All of the milk samples were inoculated with yogurt cultures at 45°C, until the pH was dropped to 4.4. Syneresis, gel-strength, acetaldehyde amounts, and the degree of TGase reaction were determined. As a result, yogurt products made from enzyme-treated milk showed increased gel strength and less syneresis. SDS-PAGE results showed that the enzyme TGase produced crosslink formation between different protein fractions of milk. In addition, it was also determined that TGase application caused a decrease in acetaldehyde amounts.     

Incorporation of dairy ingredients into wheat bread: effects on dough rheology and bread quality

 Dairy ingredients are used in breadmaking for their nutritional benefits and functional properties. The effects of the traditionally-used whole and skimmed milk powder, sodium caseinate, casein hydrolysate and three whey protein concentrates on dough rheology and bread quality were studied. Whole and skimmed milk powders improved sensory characteristics. Sodium caseinate and hydrolysed casein displayed beneficial functional properties in breadmaking including low proof time, high volume and low firmness. Both ingredients increased dough height measured with the rheofermentometer. Bread with 2% or 4% sodium caseinate added was rated highly in sensory evaluation. Incorporation of whey protein concentrates generally increased proof time, decreased loaf volume and decreased dough height measured with the rheofermentometer. Received: 6 April 1999 / Revised version: 13 July 1999     

Rheological properties of emulsions containing milk proteins mixed with xanthan gum

Oil in water emulsions (30% w/w) containing mixtures of milk proteins with xanthan gum were rheologically characterized at ambient temperature and the evolution of their properties was measured during a month under cold storage. The milk proteins used were sodium caseinate and whey concentrate at 2% mixed with xanthan gum at 0.3% or 0.5%. Emulsions properties were compared to those of respective aqueous systems and in general showed same rheological behaviour as their respective aqueous system, however, emulsions presented higher consistency index, due to oil droplets concentration. The flow behaviour index showed a small variation, increasing its value slightly. The consistency of emulsions with xanthan was similar, independently of the milk protein used, confirming that xanthan rheology predominates on emulsion rheology.     

The thermostability of spray dried imitation coffee whiteners

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 proteinate; soluble wheat protein) in combination with non-protein emulsifiers and disodium hydrogen orthophosphate. Adaptation of coffee stability test methodology was necessary to take account of the presence of significantly more 'floaters' in the case of imitation coffee whiteners which did not sediment during centrifugation. A new non-dairy protein, soluble wheat protein, proved to have exceptional stabilizing ability compared to all other protein ingredients evaluated. Sodium caseinate performed the best out of the dairy proteins, while formulations incorporating milk protein concentrate tended to be the least stable. When working with whey protein concentrate as the principal ingredient source, an emulsifier system based on mono/diglycerides was inadequate, and it was necessary to use a combination of polysorbate and sodium stearoyl lactylate in its place.     

Survival of Bifidobacterium longum 1941 microencapsulated with proteins and sugars after freezing and freeze drying

Five types of proteins and three types of sugars were examined for their effectiveness in protecting B. longum after freeze drying, including their acid and bile tolerance, surface hydrophobicity, retention of β-glucosidase, lactate dehydrogenase and adenosine triphosphatase. Sodium caseinate 12%, whey protein concentrate 12%, sodium caseinate:whey protein concentrate 6%:6%, skim milk 12%, or soy protein isolate 12% was combined with glycerol (3% w/v), mannitol (3% w/v) or maltodextrin (3% w/v). Fifteen emulsion systems containing sugars were obtained. Concentrated B. longum 1941 was incorporated into each emulsion system at a ratio of 1:4 (bacteria:emulsion). All the mixtures were then freeze dried. Water activity (a_w) of freeze dried microcapsules was in the range of 0.30 to 0.35. WPC–CAS GLY provided high stability of bacteria (99.2%) during freezing, while high stability of cells after freeze drying and during exposure to acid and bile environment was achieved when CAS–MAN was applied (97.4%, 81.6% and 99.3%, respectively). High retention of β-glu of freeze-dried bacteria was achieved using SM–MAN as protectant (94.6%). ATPase and LDH were successfully retained by SM–GLY (94.9 and 83.6%, respectively) but there was no significant difference in protection effect using CAS–MAN (93.8 and 82.6%, respectively). Overall, milk proteins were superior to SPI and sugar alcohols provided more protection than MD.     

Small and large deformation rheology and microstructure of κ-carrageenan gels containing commercial milk protein products

The rheological behaviour of commercial milk protein/κ-carrageenan mixtures in aqueous solutions was studied at neutral pH. Four milk protein ingredients; skim milk powder, milk protein concentrate, sodium caseinate, and whey protein isolate were considered. As seen by confocal laser microscopy, mixtures of κ-carrageenan with skim milk powder, milk protein concentrate, and sodium caseinate showed phase separation, but no phase separation was observed in mixtures containing whey protein isolate. For κ-carrageenan concentrations up to 0.5 wt%, the viscosity of the mixtures at low shear rates increased markedly in the case of skim milk powder and milk protein concentrate addition, but did not change by the addition of sodium caseinate or whey protein isolate. For κ-carrageenan concentrations from 1 to 2.5 wt%, small and large deformation rheological measurements, performed on the milk protein/κ-carrageenan gels, showed that skim milk powder, milk protein concentrate or sodium caseinate markedly improved the strength of the resulting gels, but whey protein isolate had no effect on the gel stength.     

EFFECT OF MILK PROTEINS AND STABILIZER ON ICE MILK QUALITY

Ice milk mixes were made with and without stabilizer/emulsifier as well as with and without milk protein isolate (sodium caseinate or whey protein isolate). The mixes were evaluated for rheological, freezing, melting, and sensory properties. Adding a stabilizer/emulsifier blend to ice milk changed its physical properties more than adding milk protein isolates. The mixes with stabilizer/emulsifier exhibited increased viscosity and chewiness and decreased drainage rate, iciness, and vanilla flavor intensity. The mixes with added caseinate exhibited increased viscosity compared with those with added whey protein isolate. Overall, the quality of ice milk mix was more dependent on stabilizer/emulsifier addition than on milk protein isolate addition.     

Milk Proteins Affect Yield and Sensory Quality of Cooked Sausages

Sausages were produced with seven different mixtures with skim milk powder, sodium caseinate and whey protein (1.5, 3, 5%) according to a simplex-centroid design, where the proportion of each ingredient varied from 0 to 100%. Principal component analysis (PCA) identified that sausages with 1.5% milk protein were most similar in sensory quality to the controls and had minimum cooking loss. PCA was effective to reduce the number of attributes to five to describe the main variation among the 1.5% milk protein sausages. A mixture of 1:1 blend of skim milk powder and whey protein resulted in the product with lowest cooking loss.     

Effects of branched-chain amino acids and sodium caseinate on milk protein concentration and yield from dairy cows

Our study investigated the separate and combined effects of branched-chain amino acids (AA) and sodium caseinate on milk protein concentration and yield. Four Holstein cows (112 d in milk) were abomasally infused with water, branched-chain AA (150 g/d), sodium caseinate (600 g/d), or branched-chain AA plus sodium caseinate (44 and 600 g/d, respectively) according to a 4 x 4 Latin square design with 8-d treatment periods. Cows were fed a dry diet based on alfalfa hay and concentrates for ad libitum intake. The ration was formulated to exceed requirements for metabolizable energy and protein using the Cornell Net Carbohydrate and Protein System. Neither daily dry matter intake (24.2 +/- 0.4 kg/d; X +/- SEM) nor milk yield (32.9 +/-; 0.4 kg/d) was affected by any of the infusion treatments. Infusion of branched-chain AA had no effect on any milk production parameters, despite a 50% increase in their concentrations. Modest increases in milk protein concentration (0.1%) and milk protein yield (62 g/d) resulted from the infusion of sodium caseinate or branched-chain AA plus sodium caseinate. True protein and whey protein concentrations in milk were also marginally increased by infusion of sodium caseinate and branched-chain AA plus sodium caseinate, and infusion of branched-chain AA, sodium caseinate, or both elevated milk nonprotein N content. Plasma urea N concentrations were elevated by the sodium caseinate and branched-chain AA plus sodium caseinate treatments. No treatment effects on other plasma metabolites or hormones were observed. Our results show no benefit of supplementation with branched-chain AA and only modest effects of sodium caseinate on milk protein concentration and yield in well-fed cows.     

Effect of milk fat concentration and gel firmness on syneresis during curd stirring in cheese-making

An experiment was undertaken to investigate the effect of milk fat level (0%, 2.5% and 5.0% w/w) and gel firmness level at cutting (5, 35 and 65 Pa) on indices of syneresis, while curd was undergoing stirring. The curd moisture content, yield of whey, fat in whey and casein fines in whey were measured at fixed intervals between 5 and 75 min after cutting the gel. The casein level in milk and clotting conditions was kept constant in all trials. The trials were carried out using recombined whole milk in an 11 L cheese vat. The fat level in milk had a large negative effect on the yield of whey. A clear effect of gel firmness on casein fines was observed. The best overall prediction, in terms of coefficient of determination, was for curd moisture content using milk fat concentration, time after gel cutting and set-to-cut time (R² = 0.95).     

Heat-induced changes in the calcium sensitivity of caseins

The calcium sensitivity of Na caseinate prepared from a serum protein-free casein micelle dispersion in synthetic milk ultrafiltrate, containing 4.8%, w/v, lactose and 5 mmol L⁻¹ urea and heated at 130°C for 0–25 min decreased with heating. It is proposed that an increase in the net negative charge of the caseinates, due to heat-induced degradation of lysine and arginine, is responsible for the enhanced calcium stability of heated caseins. The Maillard reaction and urea–protein interactions appear to play an important role in the increased stability of heated caseinate towards calcium. The effect of protein charge on the heat stability of milk protein systems (Na caseinate 2.5%, w/v, protein in milk ultrafiltrate) at 140°C was investigated by chemical modification of the caseinate prior to assessment of heat stability. Heat stability increased with the modification of lysine, arginine and carboxyl residues. The increased heat stability of Na caseinate with modified lysine and arginine residues may be due to an increase in the net negative charge on the caseinate, while the increased stability of caseinate with modified carboxyl residues may be related to a reduction in heat-induced crosslinking of protein.     

Influence of fortification with sodium–calcium caseinate and whey protein concentrate on microbiological,textural and sensory properties of set‐type yoghurt

The effect of fortification of yoghurt with sodium–calcium caseinate (SCC) and whey protein concentrate (WPC) on some properties of set‐type yoghurt were investigated. The addition of WPC enhanced the viability of Lactobacillus delbrueckii subsp. bulgaricus more than SCC. The highest firmness values were obtained from SCC‐fortified yoghurts, whereas yoghurts fortified with WPC had the highest water‐holding capacity during storage. The yoghurts fortified with 4% w/w SCC or 4% w/w WPC had the highest viscosity. Yoghurts fortified with 2% w/w SMP, SCC or WPC showed similar taste and overall acceptability scores; however, samples containing 4% w/w SCC or 4% w/w WPC had the lowest scores.     

Optimization of enzymatic oligomerization reaction conditions for three milk protein products via ceteris-paribus approach

Via a ceteris-paribus approach, optimum reaction conditions for an oxidoreductase- (lactoperoxidase; laccase; glucose oxidase) induced oligomerization of milk proteins were assessed for three different milk protein products (sodium caseinate; whey protein isolate; skim milk powder).Optimum protein monomer modification conditions were enzyme- and substrate-specifically identified, yielding protein monomer modification levels of, e.g., 58% in case of lactoperoxidase-induced (w/w = 5% protein; 1.8 μmol hydrogen peroxide/mg protein; 4.8 U lactoperoxidase/mg protein; 50 °C; 1 h; pH 7.0), 92% in case of laccase-induced (w/w = 5% protein; 0.02 μmol chlorogenic acid/mg protein; 0.01 U laccase/mg protein; 40 °C; 1 h; pH 7.0) and 86% in case of glucose oxidase-induced (w/w = 1% protein; 0.5 U glucose oxidase/mg protein; 40 °C; 16 h; pH 7.0) modification of total milk proteins from skim milk powder.The study for the first time provides a comprehensive overview over reaction conditions facilitating high degrees of milk protein monomer modification upon oxidoreductase-induced oligomerization in regard to food protein tailoring via application of less substrate- and reaction-specific enzymes than transglutaminase.     

Transglutaminase-mediated incorporation of whey protein as fat replacer into the formulation of reduced-fat Iranian white cheese: physicochemical,rheological and microstructural characterization

The effects of transglutaminase treatment (0–2 units/g milk protein) on the chemical composition, textural characteristics, proteolysis and yield of reduced-fat Iranian white cheese (milk fat: 0.4–1.4% w/w) incorporated with whey proteins (0–6 g/L milk) were investigated. Enzyme-mediated inclusion of whey proteins in the reduced-fat cheese caused a noticeable increase in moisture to protein (M:P) ratio with concomitant decease in the hardness rheological parameters of fracture stress and Young’s and storage (G’) moduli. However, increase in concentrations of whey proteins or/and transglutaminase enzyme above a critical level led to formation of a cheese matrix with lower moisture content and greater values of hardness indices. Whey protein addition and transglutaminase treatment resulted in the same trends of changes in proteolysis rate and cheese yield as in cheese softness. Response surface method (RSM) suggested that the enzymatic incorporation of 4.2 g deliberately added whey proteins to 1 L of milk (1.04% w/w fat) into the cheese matrix using 0.833 unit transglutaminase per gram milk protein would provide a reduced-fat product with the softest texture and the highest yield. The scanning electron micrographs showed formation of honeycomb structures in the protein matrix of the reduced-fat sample with optimum formulation.     

Viscosity,microstructure and phase behavior of aqueous mixtures of commercial milk protein products and xanthan gum

The behavior of commercial milk protein/xanthan mixtures was studied at neutral pH. Four milk protein ingredients; skim milk powder, milk protein concentrate, sodium caseinate and whey protein isolate were considered. For the xanthan concentrations used, up to 1wt%, the viscosity of the mixtures was dominated by the viscosity of xanthan. Mixtures of xanthan with skim milk powder or milk protein concentrate showed phase separation, as seen by confocal micrographs, and phase diagrams have been established for these two systems. No visible phase separation was observed in the case of mixtures of sodium caseinate or whey protein isolate systems. However, mixtures of sodium caseinate and xanthan, under certain conditions, showed formation of ‘thread-like’ xanthan-rich regions by confocal microscopy. We believe that the phase separation occurring in milk protein concentrate/xanthan or skim milk powder/xanthan mixtures was a result of depletion flocculation of casein micelles by the xanthan macromolecules, but thermodynamic incompatibility was likely to occur in sodium caseinate/xanthan mixtures.