Comparison of heat and pressure treatments of skim milk, fortified with whey protein concentrate, for set yogurt preparation: effects on milk proteins and gel structure

2000 ◽  
Vol 67 (3) ◽  
pp. 329-348 ◽  
Author(s):  
ERIC C. NEEDS ◽  
MARTA CAPELLAS ◽  
A. PATRICIA BLAND ◽  
PRETIMA MANOJ ◽  
DOUGLAS MACDOUGAL ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Whey Protein ◽  
Skim Milk ◽  
Milk Proteins ◽  
Whey Protein Concentrate ◽  
Protein Concentrate ◽  
Casein Micelles ◽  
Micelle Structure ◽  
Dynamic Structures ◽  
Β Lactoglobulin

Heat (85 °C for 20 min) and pressure (600 MPa for 15 min) treatments were applied to skim milk fortified by addition of whey protein concentrate. Both treatments caused > 90% denaturation of β-lactoglobulin. During heat treatment this denaturation took place in the presence of intact casein micelles; during pressure treatment it occurred while the micelles were in a highly dissociated state. As a result micelle structure and the distribution of β-lactoglobulin were different in the two milks. Electron microscopy and immunolabelling techniques were used to examine the milks after processing and during their transition to yogurt gels. The disruption of micelles by high pressure caused a significant change in the appearance of the milk which was quantified by measurement of the colour values L*, a* and b*. Heat treatment also affected these characteristics. Casein micelles are dynamic structures, influenced by changes to their environment. This was clearly demonstrated by the transition from the clusters of small irregularly shaped micelle fragments present in cold pressure-treated milk to round, separate and compact micelles formed on warming the milk to 43 °C. The effect of this transition was observed as significant changes in the colour indicators. During yogurt gel formation, further changes in micelle structure, occurring in both pressure and heat-treated samples, resulted in a convergence of colour values. However, the microstructure of the gels and their rheological properties were very different. Pressure-treated milk yogurt had a much higher storage modulus but yielded more readily to large deformation than the heated milk yogurt. These changes in micelle structure during processing and yogurt preparation are discussed in terms of a recently published micelle model.

A fluorimetric method for determination ofPseudomonas fluorescensAR11 lipase in skim milk powder, whey powder and whey protein concentrate

1984 ◽  
Vol 51 (4) ◽  
pp. 623-628 ◽  
Author(s):  
Donald Stead
Keyword(s):  
Whey Protein ◽  
Lipolytic Activity ◽  
Sodium Taurocholate ◽  
Milk Powder ◽  
Skim Milk ◽  
Milk Proteins ◽  
Skim Milk Powder ◽  
Whey Protein Concentrate ◽  
Protein Concentrate ◽  
Whey Powder

SummaryA method which was developed for assaying the extracellular lipases of psychrotrophic bacteria in milk (Stead, 1983, 1984) and which uses the fluorogenic substrate 4-methylumbelliferyl oleate has been adapted for use with skim milk powder (SMP), whey powder (WP) and whey protein concentrate (WPC). A five-fold increase in the concentration of sodium taurocholate (NaTC), in the mixture of NaTC and cetyltrimethylammonium bromide needed to dissociate lipase from milk proteins, removed the excessive sensitivity of the assay to variations in the concentrations of SMP, WP or WPC incorporated. Commercially available pancreatic lipase provided a suitable standard of lipolytic activity and as little as 1–2 μ could be detected in each assay system.

scholarly journals Mutu Keju Putih Rendah Lemak Diproduksi Dengan Bahan Baku Susu Modifikasi

2016 ◽  
Vol 40 (2) ◽  
pp. 144 ◽  
Author(s):  
Abubakar Abubakar
Keyword(s):  
Whey Protein ◽  
Milk Fat ◽  
Dry Matter ◽  
Corn Oil ◽  
Skim Milk ◽  
Raw Material ◽  
Whey Protein Concentrate ◽  
Protein Concentrate ◽  
Water Emulsion ◽  
White Cheese

This research was conducted to investigate the quality of low-fat white cheese produced using raw material of modified milk. Five treatments applied were (A1) Using reduced fat (60%) milk, (A2) Using emulsion of corn oil in skim milk (replacing milk fat with corn oil), (A3) Using emulsion of corn oil in skim milk and addition of whey protein concentrate (replacing milk fat with corn oil and the addition of whey protein concentrate=WPC), (A4) Using skim milk and water emulsion oil in water, and (A5) replacing milk fat with corn oil and the addition of probiotic (Lactobacillus casei). Each treatment was replicated three times. The selected that skim milk in corn oil emulsion with the addition of probiotics, the results showed had cheese quality characteristics as follow: yield 12.94±0.16%, hardnes 48.07±10.12 g, softness 8.51±0.54 kg/s, moisture content 50.37±1.60%, ash content 7.38±1.75% (dry matter), fat content 41.06±6.07% (dry matter), protein content 37.85±3.25% (dry matter), phosphorus content 346.62±25.61 mg/100g (dry matter), calcium content 860.78±87.91 mg/100g (dry matter), white color, regular texture, not flavorfull, salty taste, soft texture, elastic, ordinary preference acceptance.

Determination of Aflatoxin M1 in Liquid Milk, Cheese, and Selected Milk Proteins by Automated Online Immunoaffinity Cleanup with Liquid Chromatography‒Fluorescence Detection

2020 ◽  
Author(s):  
Jackie E Wood ◽  
Brendon D Gill ◽  
Harvey E Indyk ◽  
Ria Rhemrev ◽  
Monika Pazdanska ◽  
...  
Keyword(s):  
Whey Protein ◽  
High Throughput ◽  
Milk Proteins ◽  
Whey Protein Concentrate ◽  
Aflatoxin M1 ◽  
Protein Concentrate ◽  
Compliance Testing ◽  
Liquid Milk ◽  
Hydroxylated Metabolite ◽  
Single Laboratory

Abstract Background Aflatoxins are secondary metabolites produced by a number of species of Aspergillus fungi. Aflatoxin M1 (AFM1) is a hydroxylated metabolite of aflatoxin B1 and is found in the milk of cows fed with feed spoilt by Aspergillus species. AFM1 is carcinogenic, especially in the liver and kidneys, and mutagenic, and is also an immunosuppressant in humans. Objective A high-throughput method for the quantitative analysis of AFM1 that is applicable to liquid milk, cheese, milk protein concentrate (MPC), whey protein concentrate (WPC), whey protein isolate (WPI), and whey powder (WP) was developed and validated. Method AFM1 in cheese, milk, and protein products is extracted using 1% acetic acid in acetonitrile with citrate salts. The AFM1 in the resulting extract is concentrated using RIDA®CREST/IMMUNOPREP® ONLINE cartridges followed by quantification by HPLC‒fluorescence. Results The method was shown to be accurate for WP, WPC, WPI, MPC, liquid milk, and cheese, with acceptable recovery (81–112%) from spiked samples. Acceptable precision for WP, WPC, WPI, MPC, liquid milk, and cheese was confirmed, with repeatabilities of 4–12% RSD and intermediate precisions of 5–13% RSD. Method detection limit and ruggedness experiments further demonstrated the suitability of this method for routine compliance testing. An international proficiency scheme (FAPAS) cheese sample showed that this method gave results that were comparable with those from other methods. Conclusions A method for high-throughput, routine testing of AFM1 is described. The method was subjected to single-laboratory validation and was found to be accurate, precise, and fit-for-purpose. Highlights An automated online immunoaffinity cleanup HPLC‒fluorescence method for milk proteins, cheese, and milk was developed and single-laboratory validated. It allows for high-throughput analysis of AFM1 and can be used for the analysis of AFM1 in whey protein products.

High-pressure treatment of milk: effects on casein micelle structure and on enzymic coagulation

2000 ◽  
Vol 67 (1) ◽  
pp. 31-42 ◽  
Author(s):  
ERIC C. NEEDS ◽  
ROBERT A. STENNING ◽  
ALISON L. GILL ◽  
VICTORIA FERRAGUT ◽  
GILLIAN T. RICH
Keyword(s):  
Whey Proteins ◽  
Skim Milk ◽  
Casein Micelle ◽  
Casein Micelles ◽  
Dense Networks ◽  
Protein Levels ◽  
Micelle Structure ◽  
Milk Casein ◽  
Β Lactoglobulin ◽  
Gel Network

High isostatic pressures up to 600 MPa were applied to samples of skim milk before addition of rennet and preparation of cheese curds. Electron microscopy revealed the structure of rennet gels produced from pressure-treated milks. These contained dense networks of fine strands, which were continuous over much bigger distances than in gels produced from untreated milk, where the strands were coarser with large interstitial spaces. Alterations in gel network structure gave rise to differences in rheology with much higher values for the storage moduli in the pressure-treated milk gels. The rate of gel formation and the water retention within the gel matrix were also affected by the processing of the milk. Casein micelles were disrupted by pressure and disruption appeared to be complete at treatments of 400 MPa and above. Whey proteins, particularly β-lactoglobulin, were progressively denatured as increasing pressure was applied, and the denatured β-lactoglobulin was incorporated into the rennet gels. Pressure-treated micelles were coagulated rapidly by rennet, but the presence of denatured β-lactoglobulin interfered with the secondary aggregation phase and reduced the overall rate of coagulation. Syneresis from the curds was significantly reduced following treatment of the milk at 600 MPa, probably owing to the effects of a finer gel network and increased inclusion of whey protein. Levels of syneresis were more similar to control samples when the milk was treated at 400 MPa or less.

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