Heat and Fermentation Effects on Total Nonprotein Nitrogen and Urea in Milk

Saidi, Bouchta; Warthesen, J. J.

doi:10.1111/j.1365-2621.1993.tb04321.x

Cited by 10 publications

(5 citation statements)

References 18 publications

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“…34 The increased concenration of extractable gluten proteins as a result of heat treatment at 130 °C appeared to follow zeroorder kinetics. Hustinx et al 35 noted a linear increase in the levels of soluble sodium caseinate peptides during heating at pH 7.0 and 140 °C, whereas Saidi et al 36 noted a linear increase in total non-protein nitrogen content in milk during heating at 80, 100, and 120 °C. The lowest extractability (17%) of isolated gluten was observed after 15 min of heating at pH 8.0 and 130 °C.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Heat-Induced Cross-Linking and Degradation of Wheat Gluten, Serum Albumin, and Mixtures Thereof

Rombouts

Lagrain

Delcour

2012

J. Agric. Food Chem.

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Some wheat-based food systems, such as cakes, cookies, and egg noodles, contain mixtures of animal and plant (gluten) proteins and are processed under (mildly) alkaline conditions. Although changes in these proteins during processing can affect end product quality, they have seldom been studied. This study investigated protein cross-linking and degradation during heating (0-120 min, pH 8.0, 50-130 °C) of (mixtures of) wheat gluten and bovine serum albumin (BSA). The decrease in protein extractabilities in sodium dodecyl sulfate containing buffer under (non)reducing conditions and the levels of (cross-linked) amino acids were measured. No indications for polymerization at 50 °C were found. Below 100 °C, BSA polymerized more readily than wheat gluten. Above 100 °C, the opposite was observed. The kinetics of heat-induced polymerization of a 1:1 gluten-BSA mixture were similar to that of isolated gluten, implying that gluten decelerated BSA denaturation. Severe heating (130 °C, >15 min) induced degradation reactions in gluten but not in BSA. At all conditions used in this study, disulfide (SS) bonds contributed to the extractability loss. In addition, above 110 °C, β-elimination of cystine led to non-SS cross-links. Intramolecular SS bonds more often transformed in intermolecular non-SS bonds in BSA than in gluten.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Heat-Induced Cross-Linking and Degradation of Wheat Gluten, Serum Albumin, and Mixtures Thereof

Rombouts

Lagrain

Delcour

2012

J. Agric. Food Chem.

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“…eonil, 1999). Saidi and Warthesen (1993) described that sterilisation conditions (120 C for 20 min) also cause an increase in non-protein nitrogen content (ca. 18%).…”

Section: Introductionmentioning

confidence: 98%

The effect of sterilisation on amino acid contents in processed cheese

Buňka

Hrabě

Kráčmar

2004

International Dairy Journal

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“…Other observed effects of heat treatment include proteolysis, which was observed when sterilizing milk at 120°C for 30 min (Saidi and Warthesen, 1993) and protein dissociation, reported during heating of serum protein-free casein dispersions at temperatures above 110°C (Aoki et al, 1974). Heat-induced polymerization has also been reported in UHT-treated serum protein-free micellar casein dispersions (Zin El-Din and Aoki, 1993).…”

Section: Introductionmentioning

confidence: 99%

The effect of commercial sterilization regimens on micellar casein concentrates

Beliciu

Sauer

Moraru

2012

Journal of Dairy Science

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This work focused on evaluating the effects of UHT sterilization and in-container retorting on the stability and physical properties of micellar casein concentrates (MCC). The study was performed on MCC obtained by membrane separation, with casein concentrations between 5 and 10%. The UHT and retorting regimens were designed to achieve the same microbial inactivation effect. Ultra-high temperature treatment was performed in a pilot-scale MicroThermics heating system (MicroThermics Inc., Raleigh, NC), and retorting in an FMC multipurpose laboratory retort (Steritort; FMC Corp., San Jose, CA). The heat-treated and the non-heat-treated MCC controls were evaluated for pH, mineral profile, ζ-potential, particle size, and rheological properties for up to 24h after heat treatment. The treatments were performed in triplicate, and differences among samples were evaluated using statistical analyses. Retorting resulted in slight aggregation in the MCC, whereas UHT caused the formation of visible aggregates and coagulation. The UHT-treated MCC had higher viscosity than retorted MCC, and displayed predominantly solid-like rheological behavior, indicative of structure formation. These effects were, at least in part, attributed to a change in mineral equilibrium, which affected the stability of the casein micelles, but additional mechanisms such as κ-casein dissociation may also play a significant role in these heat-induced changes. Drying of MCC accentuated the observed instabilities, as dried and reconstituted micellar casein concentrates (R-MCC) were more unstable to UHT sterilization than the MCC that had not undergone drying. The results of this study provide valuable information about the sterilization behavior and physical properties of MCC, which can be useful to processors in the development and manufacture of shelf-stable casein-based products and beverages.

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Heat and Fermentation Effects on Total Nonprotein Nitrogen and Urea in Milk

Cited by 10 publications

References 18 publications

Heat-Induced Cross-Linking and Degradation of Wheat Gluten, Serum Albumin, and Mixtures Thereof

Heat-Induced Cross-Linking and Degradation of Wheat Gluten, Serum Albumin, and Mixtures Thereof

The effect of sterilisation on amino acid contents in processed cheese

The effect of commercial sterilization regimens on micellar casein concentrates

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