Assessment of the rennet coagulation of skim milk: A comparison of methods

2007 ◽  
Vol 17 (10) ◽  
pp. 1151-1160 ◽  
Author(s):  
A.H. Klandar ◽  
A. Lagaude ◽  
D. Chevalier-Lucia
Keyword(s):  
Skim Milk ◽  
Comparison Of Methods ◽  
Rennet Coagulation

QUALITY OF PROTEIN IN MILK REPLACERS FOR YOUNG CALVES. III. RENNET COAGULATION AND UNDENATURED WHEY PROTEIN NITROGEN CONTENT OF SKIM MILK POWDERS AND COMMERCIAL MILK REPLACERS

1976 ◽  
Vol 56 (2) ◽  
pp. 335-338
Author(s):  
D. B. EMMONS ◽  
E. E. LISTER ◽  
D. L. CAMPBELL
Keyword(s):  
Whey Protein ◽  
Milk Powder ◽  
Skim Milk ◽  
Skim Milk Powder ◽  
Plant Proteins ◽  
Protein Nitrogen ◽  
Rennet Coagulation ◽  
Powder Samples ◽  
Milk Replacers

Reconstituted commercial skim milk powder samples which produced a firm (> 30 g) rennet curd had high levels (> 4 mg N/g) of undenatured whey protein nitrogen (WPN) as measured by the modified Harland–Ashworth test. However, similar samples which also had high levels of WPN (> 6 mg N/g) had low curd firmness or failed to coagulate. Of 24 commercial samples of milk replacers, 2 formed a soft curd; the rest did not coagulate. Five had high levels of WPN (> 6 mg N/g); one sample contained 17.8 mg N/g, well above normal levels of skim milk powder. Plant proteins may have caused high WPN values and interfered with the Harland–Ashworth test. It was concluded that WPN is neither an acceptable index of rennet coagulability of milk replacers, nor a reliable index for selecting commercially produced skim milk powders with good rennet coagulability.

Rennet coagulation of milk in the presence of sucrose

1994 ◽  
Vol 61 (4) ◽  
pp. 473-483 ◽  
Author(s):  
Marie-Hélène Famelart
Keyword(s):  
Milk Powder ◽  
Skim Milk ◽  
Chromatographic Determination ◽  
Atomic Absorption Spectrophotometry ◽  
Skim Milk Powder ◽  
Rennet Coagulation ◽  
Diffusion Controlled ◽  
Micelle Size ◽  
Ionic Calcium ◽  
Milk Coagulation

SummaryThe aim of this work was to test the diffusion-controlled hypothesis of milk coagulation kinetics by reducing the diffusion coefficient of casein micelles. This has been achieved by increasing the solvent viscosity of milk through sucrose addition. Milk was reconstituted from skim milk powder and sucrose added at 100–300 g kg–1. Hydrolysis and coagulation were followed by chromatographic determination of caseinomacropeptide content and optical, thermal and viscoelastic measurements. Soluble and ionic calcium were determined by atomic absorption spectrophotometry and ionometry and micelle size was measured by dynamic light scattering. Addition of sucrose resulted in a substantial retardation of both enzymic and aggregation steps, a re-equilibration of calcium because of water reduction, and a micelle size increase. The enzymic rate constant was inversely proportional to the viscosity, according to a diffusion-controlled model, and the lag or characteristic times for the aggregation reaction were inversely proportional to the viscosity. These results are consistent with the involvement of diffusion-controlled steps in the sequence of reactions.

SOME IN VITRO OBSERVATIONS ON FACTORS AFFECTING RENNET (CHYMOSIN) CLOTTING OF CALF MILK REPLACERS

1981 ◽  
Vol 61 (2) ◽  
pp. 393-401 ◽  
Author(s):  
K. J. JENKINS ◽  
J. R. LESSARD ◽  
D. B. EMMONS
Keyword(s):  
Milk Powder ◽  
Skim Milk ◽  
Total Solid ◽  
Skim Milk Powder ◽  
Factors Affecting ◽  
Total Solids ◽  
Rennet Coagulation ◽  
High Concentrations ◽  
Milk Replacers

The formation of a firm rennet (chymosin) curd in the abomasum appears to have a useful physiological function in the newborn calf. The results of in vitro experiments with calf milk replacers conducted to study the effect of various factors on rennet clot formation demonstrated that low-pressure (L) dispersion of lipid into skim milk powder replacers resulted in markedly higher (P < 0.05) curd firmness values with rennet than homogenization (H) at all total solid (10, 15 and 20%) and lipid (10, 20, 30 and 40% TS) levels tested. At higher total solids levels, curd firmness, clot weight and percentage of replacer lipid in clot were significantly (P < 0.05) increased. The L dispersion method also promoted rennet coagulation and firmer curds than H when skim was partially replaced by mixtures offish protein-whey or Promine D-whey. The results indicate that reconstitution of milk replacers at high total solids levels (e.g., 20%), in conjunction with L dispersion of lipid, would be beneficial for promoting rennet coagulation, curd firmness and high concentrations of protein and lipid in the clot.

scholarly journals Effect of heat treatment at alkaline pH on the rennet coagulation properties of skim milk

2005 ◽  
Vol 85 (6) ◽  
pp. 515-526 ◽  
Author(s):  
Olivia Ménard ◽  
Bénédicte Camier ◽  
Fanny Guyomarc’h
Keyword(s):  
Heat Treatment ◽  
Skim Milk ◽  
Alkaline Ph ◽  
Rennet Coagulation

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.

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