Rheological properties at small (dynamic) and large (yield) deformations of acid gels made from heated milk

1997 ◽  
Vol 64 (4) ◽  
pp. 591-600 ◽  
Author(s):  
JOHN A. LUCEY ◽  
CHENG TET TEO ◽  
PETER A. MUNRO ◽  
HARJINDER SINGH
Keyword(s):  
Rheological Properties ◽  
Whey Proteins ◽  
Milk Powder ◽  
Skim Milk ◽  
High Heat ◽  
Skim Milk Powder ◽  
Heat Treatments ◽  
Heated Milk ◽  
Large Yield ◽  
Powder Manufacture

The effect of a range of milk heat treatments on the rheological properties, at small and large deformations, of acid skim milk gels was investigated. Gels were made from reconstituted skim milk heated at 75, 80, 85 and 90°C for 15 or 30 min by acidification with glucono-δ-lactone at 30°C. Gels were also made from skim milk powder (SMP) samples that had been given a range of preheat treatments during powder manufacture. Heating milks at temperatures [ges ]80°C for 15 min increased the storage moduli (G′) compared with unheated milk and produced gels with G′ in the range 300–450 Pa. Acid gels made from high-heat or medium-heat SMP had higher G′ than gels made from low-heat or ultra-low-heat SMP. Cooling gels to low temperatures resulted in an increase in G′. The yield stress of gels slightly decreased with mild heat treatments of milk, and then increased again to a maximum, finally decreasing slightly with very high heat treatments of milk. The strain at yielding decreased markedly with increasing heat treatment of milk, making these gels brittle and easier to fracture. We propose that denatured whey proteins aggregated with casein particles during the acidification of heated milk and were responsible for most of the effects observed in this study.

QUALITY OF PROTEIN IN MILK REPLACERS FOR YOUNG CALVES. IV. RENNET (CHYMOSIN, RENNIN) COAGULATION OF RECONSTITUTED SKIM MILK POWDER CONTAINING ADDED PROTEINS, FAT, CALCIUM, PHOSPHATE AND CITRATE

1976 ◽  
Vol 56 (2) ◽  
pp. 339-345 ◽  
Author(s):  
D. B. EMMONS ◽  
J. D. JONES ◽  
E. E. LISTER
Keyword(s):  
Soy Protein Isolate ◽  
Milk Powder ◽  
Skim Milk ◽  
High Heat ◽  
Skim Milk Powder ◽  
Protein Isolate ◽  
Active Principle ◽  
Total Solids ◽  
Ph Values ◽  
Milk Replacers

The effects of added nutrient sources on curd firmness of reconstituted skim milk powder (10% total solids) were studied. Defatted rapeseed flour (4%) had little effect whereas whey powder (4%) and fish protein concentrate (2%) decreased gel strength of the reconstituted skim milk by approximately 30%. Soybean meal (4%) and soy protein isolate (2%) markedly reduced curd firmness; addition of CaCl2 restored coagulability and curd firmness. However, addition of CaCl2 did not restore gel firmness in reconstituted, severely heated skim milk powder to that of a low-temperature product. Addition of 0.1% CaCl2 slightly increased firmness of reconstituted low- and high-heat powder at pH 6.1; further addition to 0.4% CaCl2 decreased firmness slightly. It appears that when there is sufficient available Ca, further additions have no effect on curd firmness. The results indicate that milk replacers which coagulate with rennet (containing chymosin or rennin as active principle) can probably be produced even when some of the skim milk protein is replaced by other less expensive proteins. Addition of citrate (14 mM), followed by adjustment of the pH, prevented coagulation at pH 6.1 and markedly reduced firmness at pH 5.6 and 5.2. Addition of citrate at 5.7 mM did not prevent coagulation at those pH values. Addition of phosphate had little effect on curd firmness at these pH values. Addition of fat to skim milk containing 15 or 20% total solids, followed by homogenization, had little effect on curd firmness at pH 6.1. Fat additions, however, decreased curd firmness of skim milk containing 10% total solids and nearly prevented coagulation in skim milk containing 5% total solids.

Kinematic viscosities of New Zealand skim-milk

1978 ◽  
Vol 45 (1) ◽  
pp. 25-35 ◽  
Author(s):  
J. H. Buckingham
Keyword(s):  
New Zealand ◽  
Seasonal Variations ◽  
Kinematic Viscosity ◽  
Milk Powder ◽  
Skim Milk ◽  
Skim Milk Powder ◽  
Total Solids ◽  
Solids Concentration ◽  
Powder Manufacture ◽  
Single Batch

SummaryThe variation in kinematic viscosity (ν) with solids concentration and temperature has been determined for native skim-milk concentrates and reconstituted New Zealand skim-milk. Below 40% (w/v) total solids, samples reconstituted from a single batch of skim-milk powder model the behaviour of native concentrates obtained from an evaporation plant at all times of the year. Above 40% (w/v) agethickening and seasonal variations in the viscosity of native concentrates become significant. Age-thickening can be reduced by cooling the concentrate. These results are discussed in relation to milk powder manufacture.

Effect of interactions between denatured whey proteins and casein micelles on the formation and rheological properties of acid skim milk gels

1998 ◽  
Vol 65 (4) ◽  
pp. 555-567 ◽  
Author(s):  
JOHN A. LUCEY ◽  
MICHELLE TAMEHANA ◽  
HARJINDER SINGH ◽  
PETER A. MUNRO
Keyword(s):  
Heat Treatment ◽  
Rheological Properties ◽  
Loss Tangent ◽  
Whey Proteins ◽  
Skim Milk ◽  
Casein Micelles ◽  
Heated Milk ◽  
Tan Δ ◽  
Reconstituted Milk ◽  
Acid Milk Gels

The effect of interactions of denatured whey proteins with casein micelles on the rheological properties of acid milk gels was investigated. Gels were made by acidification of skim milk with glucono-δ-lactone at 30°C using reconstituted skim milk powders (SMP; both low- and ultra-low-heat) and fresh skim milk (FSM). The final pH of the gels was ∼4·6. Milks containing associated or ‘bound’ denatured whey proteins (BDWP) with casein micelles were made by resuspending the ultracentrifugal pellet of heated milk in ultrafiltration permeate. Milks containing ‘soluble’ denatured whey protein (SDWP) aggregates were formed by heat treatment of an ultracentrifugal supernatant which was then resuspended with the pellet. Acid gels made from unheated milks had low storage moduli, G′, of <20 Pa. Heating milks at 80°C for 30 min resulted in acid gels with G′ in the range 390–430 Pa. The loss tangent (tan δ) of gels made from heated milk increased after gelation to attain a maximum at pH ∼5·1, but no maximum was observed in gels made from unheated milk. Acid gels made from milks containing BDWP that were made from low-heat SMP, ultra-low-heat SMP and FSM had G′ of about 250, 270 and 310 Pa respectively. Acid gels made from milks containing SDWP that were made from ultra-low-heat SMP or FSM had G′ values in the range 17–30 Pa, but gels made from low-heat SMP had G′ of ∼140 Pa. It was concluded that BDWP were important for the increased G′ of acid gels made from heated milk. Addition of N-ethylmaleimide (NEM) to low-heat reconstituted milk, to block the —SH groups, resulted in a reduction of the G′ of gels formed from heated milk but did not reduce G′ to the value of unheated milk. Addition of 20 mm-NEM to FSM, prior to heat treatment, resulted in gels with a lower G′ value than gels made from reconstituted low-heat SMP. It was suggested that small amounts of denatured whey proteins associated with casein micelles during low-heat SMP manufacture were probably responsible for the higher G′ of gels made from milk containing SDWP and from milk heated in the presence of 20 mm-NEM, compared with gels made from FSM.

Rheological properties of milk gels formed by a combination of rennet and glucono-δ-lactone

2000 ◽  
Vol 67 (3) ◽  
pp. 415-427 ◽  
Author(s):  
JOHN A. LUCEY ◽  
MICHELLE TAMEHANA ◽  
HARJINDER SINGH ◽  
PETER A. MUNRO
Keyword(s):  
Heat Treatment ◽  
Rheological Properties ◽  
Large Scale ◽  
Whey Proteins ◽  
Skim Milk ◽  
Rheological Behaviour ◽  
Intermolecular Forces ◽  
Heated Milk ◽  
Rennet Coagulation ◽  
Tan Δ

The effects of heat treatment of milk, and a range of rennet and glucono-δ-lactone (GDL) concentrations on the rheological properties, at small and large deformation, of milk gels were investigated. Gels were made from reconstituted skim milk at 30 °C, with two levels each of rennet and GDL. Together with controls this gave a total of sixteen gelation conditions, eight for unheated and eight for heated milk. Acid gels made from unheated milks had low storage moduli (G′) of < 20 Pa. Heating milks at 80 °C for 30 min resulted in a large increase in the G′ value of acid gels. Rennet-induced gels made from unheated milk had G′ values in the range ∼ 80–190 Pa. However, heat treatment severely impaired rennet coagulation: no gel was formed at low rennet levels and only a very weak gel was formed at high levels. In gels made with a combination of rennet and GDL unusual rheological behaviour was observed. After gelation, G′ initially increased rapidly but then remained steady or even decreased, and at long ageing times G′ values increased moderately or remained low. The loss tangent (tan δ) of acid gels made from heated milk increased after gelation to attain a maximum at pH ∼ 5·1 but no maximum was observed in gels made from unheated milk. Gels made by a combination of rennet and GDL also exhibited a maximum in tan δ, indicating increased relaxation behaviour of the protein–protein bonds. We suggest that this maximum in tan δ was caused by a loosening of the intermolecular forces in casein particles caused by solubilization of colloidal calcium phosphate. We also suggest that in combination gels made from unheated milk a low value for the fracture stress and a high tan δ during gelation indicated an increased susceptibility of the network to excessive large scale rearrangements. In contrast, combination gels made from heated milk formed firmer gels crosslinked by denatured whey proteins and underwent fewer large scale rearrangements.

EDTA-induced dissociation of casein micelles and its effect on foaming properties of milk

1997 ◽  
Vol 64 (4) ◽  
pp. 495-504 ◽  
Author(s):  
BRENT R. WARD ◽  
SIMON J. GODDARD ◽  
MARY-ANN AUGUSTIN ◽  
IAN R. McKINNON
Keyword(s):  
Heat Treatment ◽  
Foam Stability ◽  
Whey Proteins ◽  
Skim Milk ◽  
High Heat ◽  
Foaming Properties ◽  
Water Interface ◽  
Casein Micelles ◽  
Air Water Interface ◽  
Powder Manufacture

The effects of addition of EDTA on the dissociation of caseins and foaming properties of milks (100 g solids/l) reconstituted from skim milk powders given a low-heat (72°C for 30 s) or high-heat (85°C for 30 min) treatment during powder manufacture were determined. The EDTA-induced dissociation of caseins was independent of heat treatment but in high-heat milk was accompanied by release of denatured whey proteins. EDTA changed the proportions of individual caseins in the supernatant. EDTA addition improved both foam overrun and foam stability of low- and high-heat milks. The increase in serum protein on addition of EDTA contributed to the improvement in foaming properties of milks by increasing the availability of the proteins for formation of the air–water interface.

Character Impact Odorants of High-Heat Skim Milk Powder Isolated by Simultaneous Distillation−Extraction

2008 ◽  
Vol 56 (7) ◽  
pp. 2469-2476 ◽  
Author(s):  
Noriaki Kobayashi ◽  
Yasumichi Mizota ◽  
Kenji Kumazawa ◽  
Osamu Nishimura
Keyword(s):  
Milk Powder ◽  
Skim Milk ◽  
High Heat ◽  
Skim Milk Powder ◽  
Simultaneous Distillation Extraction ◽  
Character Impact

Ultrafiltration of reconstituted skim milk

1989 ◽  
Vol 56 (1) ◽  
pp. 147-149 ◽  
Author(s):  
Mohamed H. Abd El-Salam ◽  
Nadia Shahein
Keyword(s):  
Milk Production ◽  
Milk Powder ◽  
Skim Milk ◽  
Skim Milk Powder ◽  
Heat Treatments ◽  
Variable Heat

The manufacture of Domiati cheese by ultrafiltration (UF) processing of recombined milk bas been described in several reports (El-Shibinyet al.1982; Bogaard, 1986). This method has several potential advantages in areas short in milk production. In Egypt, a new plant has been established recently for the manufacture of Domiati cheese on the basis of this technology.The behaviour of fresh pasteurized skim milk during UF has been described (Glover, 1971; Setti & Peri, 1976; Patel & Reuter, 1985; Chiang & Cheryan, 1986). Similar studies are lacking for reconstituted skim milk or recombined milk. Skim milk powder is usually subjected to variable heat treatments during processing which are known to affect its properties. These heat treatments have been used as a basis for classification of skim milk powders. Therefore, studies on UF of reconstituted milks previously subjected to different heat treatments would be important in the adaptation of this technology to cheese manufacture.We describe here results obtained for permeation rates of reconstituted skim milk during UF compared with fresh pasteurized skim milk.

Production, composition, and manufacturing properties of milk from grazing cows fed on a formaldehyde-treated sunflower seed supplement

1976 ◽  
Vol 27 (6) ◽  
pp. 917 ◽  
Author(s):  
BD Bartsch ◽  
NJS Ellis ◽  
DM McLean ◽  
JC Radcliffe
Keyword(s):  
Milk Fat ◽  
Sunflower Seed ◽  
Energy Content ◽  
Plasma Cholesterol ◽  
Milk Powder ◽  
Skim Milk ◽  
Heat Stability ◽  
Skim Milk Powder ◽  
Powder Manufacture ◽  
The Stability

Eight cows in each of four treatment groups grazed regulated areas of green oats and consumed either 0, 1.3, 2.5 or 3.1 kg of a formaldehyde-treated sunflower seed supplement (FSS) per head per day. The digestible energy content of the rations was balanced with hammer-milled barley. Milk fat percentages and milk fat yields were higher from cows fed on FSS, responses being in proportion to the amount of FSS eaten. Protein percentages were significantly lower in milk from cows fed on FSS. Milk and protein yields did not differ significantly between treatments. The linoleic acid (C18:2) content of milk fat was three to five times as high in cows fed on FSS as in those not fed on FSS. The stability to oxidation and the rennet curd firmness of the milk decreased as the percentage of C18:2 in milk fat increased. Changes in the heat stability of milk were associated with the introduction of FSS feeding. Plasma cholesterol levels increased with increasing intakes of FSS. Milk of high C18:2 content can be produced by dairy cows fed on FSS and grazed on green oats. The milk readily oxidizes and its properties for cheese and skim milk powder manufacture are altered.

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