1
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Holt C, Carver JA. Invited review: Modeling milk stability. J Dairy Sci 2024; 107:5259-5279. [PMID: 38522835 DOI: 10.3168/jds.2024-24779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Accepted: 02/15/2024] [Indexed: 03/26/2024]
Abstract
Novel insights into the stability of milk and milk products during storage and processing result from describing caseins near neutral pH as hydrophilic, intrinsically disordered, proteins. Casein solubility is strongly influenced by pH and multivalent ion binding. Solubility is high at a neutral pH or above, but decreases as the casein net charge approaches zero, allowing a condensed casein phase or gel to form, then increases at lower pH. Of particular importance for casein micelle stability near neutral pH is the proportion of free caseins in the micelle (i.e., caseins not bound directly to nanoclusters of calcium phosphate). Free caseins are more soluble and better able to act as molecular chaperones (to prevent casein and whey protein aggregation) than bound caseins. Some free caseins are highly phosphorylated and can also act as mineral chaperones to inhibit the growth of calcium phosphate phases and prevent mineralized deposits from forming on membranes or heat exchangers. Thus, casein micelle stability is reduced when free caseins bind to amyloid fibrils, destabilized whey proteins or calcium phosphate. The multivalent-binding model of the casein micelle quantitatively describes these and other factors affecting the stability of milk and milk protein products during manufacture and storage.
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Affiliation(s)
- C Holt
- School of Biomolecular Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
| | - J A Carver
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
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2
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Liu W, Feng Y, Delaplace G, André C, Chen XD. Effect of calcium on the reversible and irreversible thermal denaturation pathway of β-lactoglobulin. Food Hydrocoll 2022. [DOI: 10.1016/j.foodhyd.2022.107943] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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3
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Liu W, Feng Y, Pan F, Jeantet R, André C, Chen XD, Delaplace G. Effect of calcium on the thermal denaturation of whey proteins and subsequent fouling in a benchtop fouling device: An experimental and numerical approach. FOOD AND BIOPRODUCTS PROCESSING 2022. [DOI: 10.1016/j.fbp.2022.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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4
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Heat-induced changes in milk fat and milk fat globules and its derived effects on acid dairy gelation – A review. Int Dairy J 2022. [DOI: 10.1016/j.idairyj.2021.105213] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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5
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Anema SG. Heat-induced changes in caseins and casein micelles, including interactions with denatured whey proteins. Int Dairy J 2021. [DOI: 10.1016/j.idairyj.2021.105136] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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6
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Halabi A, Deglaire A, Hennetier M, Violleau F, Burel A, Bouhallab S, Dupont D, Croguennec T. Structural characterization of heat-induced protein aggregates in model infant milk formulas. Food Hydrocoll 2020. [DOI: 10.1016/j.foodhyd.2020.105928] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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7
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Production of Liquid Milk Protein Concentrate with Antioxidant Capacity, Angiotensin Converting Enzyme Inhibitory Activity, Antibacterial Activity, and Hypoallergenic Property by Membrane Filtration and Enzymatic Modification of Proteins. Processes (Basel) 2020. [DOI: 10.3390/pr8070871] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Liquid milk protein concentrate with different beneficial values was prepared by membrane filtration and enzymatic modification of proteins in a sequential way. In the first step, milk protein concentrate was produced from ultra-heat-treated skimmed milk by removing milk serum as permeate. A tubular ceramic-made membrane with filtration area 5 × 10−3 m2 and pore size 5 nm, placed in a cross-flow membrane house, was adopted. Superior operational strategy in filtration process was herein: trans-membrane pressure 3 bar, retention flow rate 100 L·h−1, and implementation of a static turbulence promoter within the tubular membrane. Milk with concentrated proteins from retentate side was treated with the different concentrations of trypsin, ranging from 0.008–0.064 g·L−1 in individual batch-mode operations at temperature 40 °C for 10 min. Subsequently, inactivation of trypsin in reaction was done at a temperature of 70 °C for 30 min of incubation. Antioxidant capacity in enzyme-treated liquid milk protein concentrate was measured with the Ferric reducing ability of plasma assay. The reduction of angiotensin converting enzyme activity by enzyme-treated liquid milk protein concentrate was measured with substrate (Abz-FRK(Dnp)-P) and recombinant angiotensin converting enzyme. The antibacterial activity of enzyme-treated liquid milk protein concentrate towards Bacillus cereus and Staphylococcus aureus was tested. Antioxidant capacity, anti-angiotensin converting enzyme activity, and antibacterial activity were increased with the increase of trypsin concentration in proteolytic reaction. Immune-reactive proteins in enzyme-treated liquid milk protein concentrate were identified with clinically proved milk positive pooled human serum and peroxidase-labelled anti-human Immunoglobulin E. The reduction of allergenicity in milk protein concentrate was enzyme dose-dependent.
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8
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Yang B, Zhang S, Pang X, Lu J, Wu Z, Yue Y, Wang T, Jiang Z, Lv J. Separation of serum proteins and micellar casein from skim goat milk by pilot‐scale 0.05‐μm pore‐sized ceramic membrane at 50°C. J FOOD PROCESS ENG 2019. [DOI: 10.1111/jfpe.13334] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Baoyu Yang
- Institute of Food Science and TechnologyChinese Academy of Agricultural Sciences Beijing China
- College of Life ScienceYantai University Yantai China
| | - Shuwen Zhang
- Institute of Food Science and TechnologyChinese Academy of Agricultural Sciences Beijing China
| | - Xiaoyang Pang
- Institute of Food Science and TechnologyChinese Academy of Agricultural Sciences Beijing China
| | - Jing Lu
- Institute of Food Science and TechnologyChinese Academy of Agricultural Sciences Beijing China
| | - Zheng Wu
- Institute of Food Science and TechnologyChinese Academy of Agricultural Sciences Beijing China
| | - Yuanchun Yue
- Institute of Food Science and TechnologyChinese Academy of Agricultural Sciences Beijing China
| | - Tong Wang
- Institute of Food Science and TechnologyChinese Academy of Agricultural Sciences Beijing China
| | - Zhumao Jiang
- College of Life ScienceYantai University Yantai China
| | - Jiaping Lv
- Institute of Food Science and TechnologyChinese Academy of Agricultural Sciences Beijing China
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9
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Jo Y, Carter B, Barbano D, Drake M. Identification of the source of volatile sulfur compounds produced in milk during thermal processing. J Dairy Sci 2019; 102:8658-8669. [DOI: 10.3168/jds.2019-16607] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 05/16/2019] [Indexed: 11/19/2022]
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10
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Kumar R, Mishra D, Sutariya H, Chaudhary MB, Rao KJ. Effect of different coagulants on the yield, sensory, instrumental colour and textural characteristics of cow's milk Paneer. INT J DAIRY TECHNOL 2019. [DOI: 10.1111/1471-0307.12615] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Ranjan Kumar
- Dairy Technology Section ICAR‐National Dairy Research Institute (Southern Regional Station) Adugodi Bengaluru 560 030 India
| | - Diwakar Mishra
- Dairy Technology Section ICAR‐National Dairy Research Institute (Southern Regional Station) Adugodi Bengaluru 560 030 India
| | - Harinkumar Sutariya
- Dairy Technology Section ICAR‐National Dairy Research Institute (Southern Regional Station) Adugodi Bengaluru 560 030 India
| | - Madhabhai B Chaudhary
- Dairy Technology Section ICAR‐National Dairy Research Institute (Southern Regional Station) Adugodi Bengaluru 560 030 India
| | - Kulkarni J Rao
- Dairy Technology Section ICAR‐National Dairy Research Institute (Southern Regional Station) Adugodi Bengaluru 560 030 India
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Loiseleux T, Rolland-Sabaté A, Garnier C, Croguennec T, Guilois S, Anton M, Riaublanc A. Determination of hydro-colloidal characteristics of milk protein aggregates using Asymmetrical Flow Field-Flow Fractionation coupled with Multiangle Laser Light Scattering and Differential Refractometer (AF4-MALLS-DRi). Food Hydrocoll 2018. [DOI: 10.1016/j.foodhyd.2017.08.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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12
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Smith JR, Carr AJ, Golding M, Reid D. Mozzarella Cheese – A Review of the Structural Development During Processing. FOOD BIOPHYS 2017. [DOI: 10.1007/s11483-017-9511-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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13
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Raynes JK, Day L, Crepin P, Horrocks MH, Carver JA. Coaggregation of κ-Casein and β-Lactoglobulin Produces Morphologically Distinct Amyloid Fibrils. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2017; 13:1603591. [PMID: 28146312 DOI: 10.1002/smll.201603591] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 12/20/2016] [Indexed: 06/06/2023]
Abstract
The unfolding, misfolding, and aggregation of proteins lead to a variety of structural species. One form is the amyloid fibril, a highly aligned, stable, nanofibrillar structure composed of β-sheets running perpendicular to the fibril axis. β-Lactoglobulin (β-Lg) and κ-casein (κ-CN) are two milk proteins that not only individually form amyloid fibrillar aggregates, but can also coaggregate under environmental stress conditions such as elevated temperature. The aggregation between β-Lg and κ-CN is proposed to proceed via disulfide bond formation leading to amorphous aggregates, although the exact mechanism is not known. Herein, using a range of biophysical techniques, it is shown that β-Lg and κ-CN coaggregate to form morphologically distinct co-amyloid fibrillar structures, a phenomenon previously limited to protein isoforms from different species or different peptide sequences from an individual protein. A new mechanism of aggregation is proposed whereby β-Lg and κ-CN not only form disulfide-linked aggregates, but also amyloid fibrillar coaggregates. The coaggregation of two structurally unrelated proteins into cofibrils suggests that the mechanism can be a generic feature of protein aggregation as long as the prerequisites for sequence similarity are met.
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Affiliation(s)
- Jared K Raynes
- CSIRO Agriculture and Food, Werribee, Victoria, 3031, Australia
| | - Li Day
- AgResearch Limited, Grasslands Research Centre, Tennent Drive, Palmerston North, 4442, New Zealand
| | - Pauline Crepin
- École Nationale Supérieure de Chimie, Biologie et Physique, Bordeaux, 33607, France
| | - Mathew H Horrocks
- Proteostasis and Disease Research Centre, School of Biological Sciences, University of Wollongong, Wollongong, New South Wales, 2522, Australia
| | - John A Carver
- Research School of Chemistry, The Australian National University, Acton, Australian Capital Territory, 2601, Australia
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14
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Cheison SC, Kulozik U. Impact of the environmental conditions and substrate pre-treatment on whey protein hydrolysis: A review. Crit Rev Food Sci Nutr 2017; 57:418-453. [PMID: 25976220 DOI: 10.1080/10408398.2014.959115] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Proteins in solution are subject to myriad forces stemming from interactions with each other as well as with the solvent media. The role of the environmental conditions, namely pH, temperature, ionic strength remains under-estimated yet it impacts protein conformations and consequently its interaction with, and susceptibility to, the enzyme. Enzymes, being proteins are also amenable to the environmental conditions because they are either activated or denatured depending on the choice of the conditions. Furthermore, enzyme specificity is restricted to a narrow regime of optimal conditions while opportunities outside the optimum conditions remain untapped. In addition, the composition of protein substrate (whether mixed or single purified) have been underestimated in previous studies. In addition, protein pre-treatment methods like heat denaturation prior to hydrolysis is a complex phenomenon whose progression is influenced by the environmental conditions including the presence or absence of sugars like lactose, ionic strength, purity of the protein, and the molecular structure of the mixed proteins particularly presence of free thiol groups. In this review, we revisit protein hydrolysis with a focus on the impact of the hydrolysis environment and show that preference of peptide bonds and/or one protein over another during hydrolysis is driven by the environmental conditions. Likewise, heat-denaturing is a process which is dependent on not only the environment but the presence or absence of other proteins.
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Affiliation(s)
| | - Ulrich Kulozik
- b Chair for Food Process Engineering and Dairy Technology Department , ZIEL Technology Section, Technische Universität München , Weihenstephaner Berg 1, Freising , Germany
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15
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Ha WK, Lee J, Kim KE. Development and properties of hypoallergenic infant formula. ALLERGY ASTHMA & RESPIRATORY DISEASE 2017. [DOI: 10.4168/aard.2017.5.2.63] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Woel-Kyu Ha
- Research and Development Center, Maeil Dairies Co., Ltd., Pyeongtaek, Korea
| | - Jeongmin Lee
- Research and Development Center, Maeil Dairies Co., Ltd., Pyeongtaek, Korea
| | - Kyu-Earn Kim
- Development of Pediatrics, Yonsei University College of Medicine, Seoul, Korea
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16
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17
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Anionic and zwitterionic phospholipids differently affect the heat coagulation of recombined concentrated milk emulsions. Int Dairy J 2014. [DOI: 10.1016/j.idairyj.2014.05.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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18
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Wijayanti HB, Bansal N, Deeth HC. Stability of Whey Proteins during Thermal Processing: A Review. Compr Rev Food Sci Food Saf 2014. [DOI: 10.1111/1541-4337.12105] [Citation(s) in RCA: 215] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Heni B. Wijayanti
- School of Agriculture and Food Sciences; Univ. of Queensland; Brisbane QLD 4072 Australia
| | - Nidhi Bansal
- School of Agriculture and Food Sciences; Univ. of Queensland; Brisbane QLD 4072 Australia
| | - Hilton C. Deeth
- School of Agriculture and Food Sciences; Univ. of Queensland; Brisbane QLD 4072 Australia
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19
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Ryan KN, Zhong Q, Foegeding EA. Use of whey protein soluble aggregates for thermal stability-a hypothesis paper. J Food Sci 2014; 78:R1105-15. [PMID: 23957418 DOI: 10.1111/1750-3841.12207] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 06/05/2013] [Indexed: 11/27/2022]
Abstract
Forming whey proteins into soluble aggregates is a modification shown to improve or expand the applications in foaming, emulsification, gelation, film-formation, and encapsulation. Whey protein soluble aggregates are defined as aggregates that are intermediates between monomer proteins and an insoluble gel network or precipitate. The conditions under which whey proteins denature and aggregate have been extensively studied and can be used as guiding principles of producing soluble aggregates. These conditions are reviewed for pH, ion type and concentration, cosolutes, and protein concentration, along with heating temperature and duration. Combinations of these conditions can be used to design soluble aggregates with desired physicochemical properties including surface charge, surface hydrophobicity, size, and shape. These properties in turn can be used to obtain target macroscopic properties, such as viscosity, clarity, and stability, of the final product. A proposed approach to designing soluble aggregates with improved thermal stability for beverage applications is presented.
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Affiliation(s)
- Kelsey N Ryan
- Donald Danforth Plant Science Center, Washington Univ. School of Medicine, St. Louis, MO 63110, USA
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20
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Beckman S, Barbano D. Effect of microfiltration concentration factor on serum protein removal from skim milk using spiral-wound polymeric membranes. J Dairy Sci 2013; 96:6199-212. [DOI: 10.3168/jds.2013-6655] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Accepted: 05/23/2013] [Indexed: 11/19/2022]
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21
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Kumar S, Rai DC, Niranjan K, Bhat ZF. Paneer-An Indian soft cheese variant: a review. Journal of Food Science and Technology 2011; 51:821-31. [PMID: 24803688 DOI: 10.1007/s13197-011-0567-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Revised: 09/02/2011] [Accepted: 10/10/2011] [Indexed: 11/28/2022]
Abstract
Paneer, a popular indigenous dairy product of India, is similar to an unripened variety of soft cheese which is used in the preparation of a variety of culinary dishes and snacks. It is obtained by heat and acid coagulation of milk, entrapping almost all the fat, casein complexed with denatured whey proteins and a portion of salts and lactose. Paneer is marble white in appearance, having firm, cohesive and spongy body with a close-knit texture and a sweetish-acidic-nutty flavour. Preparation of paneer using different types of milk and varied techniques results in wide variation in physico-chemical, microbiological and sensory quality of the product. Paneer blocks of required size are packaged in laminated plastic pouches, preferably vacuum packaged, heat sealed and stored under refrigeration. Paneer keeps well for about a day at ambient temperature and for about a week under refrigeration (7 °C). The spoilage of paneer is mainly due to bacterial action. Successful attempts have been made to enhance the shelf life of paneer. This review deals with the history, method of manufacture, factors affecting the quality, physico-chemical changes during manufacture, chemical composition and nutritional profile, packaging and shelf life of paneer.
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Affiliation(s)
- Sunil Kumar
- Division of Livestock Products Technology, Faculty of Veterinary Science and Animal Husbandry, Sher-e-kashmir University of Agriculture & Technology, R.S. Pura, Jammu, 181102 India
| | - D C Rai
- Department of Animal Husbandry and Dairying, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, 221005 India
| | - K Niranjan
- Food Bioprocessing, Department of Food and Nutritional Sciences, University of Reading, Reading, UK
| | - Zuhaib F Bhat
- Division of Livestock Products Technology, Faculty of Veterinary Science and Animal Husbandry, Sher-e-kashmir University of Agriculture & Technology, R.S. Pura, Jammu, 181102 India
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22
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Chavan RS, Chavan SR, Khedkar CD, Jana AH. UHT Milk Processing and Effect of Plasmin Activity on Shelf Life: A Review. Compr Rev Food Sci Food Saf 2011. [DOI: 10.1111/j.1541-4337.2011.00157.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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23
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Barbiroli A, Bonomi F, Ferranti P, Fessas D, Nasi A, Rasmussen P, Iametti S. Bound fatty acids modulate the sensitivity of bovine β-lactoglobulin to chemical and physical denaturation. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:5729-5737. [PMID: 21506515 DOI: 10.1021/jf200463u] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Fatty acids are the natural ligands associated with the bovine milk lipocalin, β-lactoglobulin (BLG), and were identified by means of mass spectrometry. The naturally bound ligands were found to contribute to the stability of the proteins toward denaturation by both temperature and chaotropes. To assess the nature of the structural regions involved in this stabilization, the thermodynamic and kinetic aspects of the stability of various structural regions of the proteins were studied in the presence of bound palmitate, which is the most abundant natural ligand. Binding of a single palmitate molecule was found to affect not only the stability of the calyx region, where palmitate is bound, but also that of the region at the hydrophobic interface between the barrel itself and the long helix in the protein structure, where the thiol group of Cys121 is buried. This region is known to be essential for the stability of the BLG dimer and is relevant to the generation of "reactive monomers" that are involved in covalent and noncovalent polymerization of BLG and in the formation of covalent adducts with other milk proteins.
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Affiliation(s)
- Alberto Barbiroli
- Section of Biochemistry, DISMA, Università degli Studi di Milano, Milan, Italy
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24
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25
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Chelulei Cheison S, Brand J, Leeb E, Kulozik U. Analysis of the effect of temperature changes combined with different alkaline pH on the β-lactoglobulin trypsin hydrolysis pattern using MALDI-TOF-MS/MS. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:1572-1581. [PMID: 21319805 DOI: 10.1021/jf1039876] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Temperature and pH influence the conformation of the whey protein β-lactoglobulin (β-Lg) monomer, dimer, and octamer formation, its denaturation, and solubility. Most hydrolyses have been reported at trypsin (EC 3.4.21.4) optimum conditions (pH 7.8 and 37 °C), while the hydrolysate mass spectrometry was largely limited to peptides with <4 kDa. There are few reports on trypsin peptide release patterns away from optimum. This work investigated the influence of alkaline (8.65 and 9.5) and optimum (7.8) pH at different temperatures (25, 37.5, and 50 °C) on β-Lg (7.5%, w/v) hydrolysis. Sample aliquots were drawn out before the addition of trypsin (blank sample) and at various time intervals (15 s to 10 min) thereafter. Matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF-MS/MS) was used to monitor peptide evolution over time with the use of two matrixes: α-cyano-4-hydroxycinnamic acid (HCCA) and 2.5-dihydroxyacetophenone (DHAP). Mass analysis showed that the N- and C-terminals (Lys(8)-Gly(9), Lys(100)-Lys(101), Arg(124)-Thr(125), Lys(141)-Ala(142), and Arg(148)-Leu(149)) of β-Lg were cleaved early (15 s) implying the ease of trypsinolysis at the exposed terminals. Hydrolyses at 25 °C and pH 7.8 as well as at 50 °C and pH 9.5 were slowed down and ordered. Nonspecific chymotrypsin-like behavior occurred more at higher temperatures (50 °C) than at lower ones (25 and 37.5 °C). In addition to our earlier work in the acid pH region, it can be concluded that there is potential for controlled hydrolysis outside the trypsin optimum, where different target peptides with predictable biofunctionalities could be produced.
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Affiliation(s)
- Seronei Chelulei Cheison
- Zentralinstitut für Ernährungs- und Lebensmittelforschung (ZIEL)-Junior Research Group: Bioactive Peptides and Protein Technology, Technische Universität München , Weihenstephaner Berg 1, D-85354 Freising, Germany.
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26
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Meyer B, Al-Diab D, Vollmer G, Pischetsrieder M. Mapping the glycoxidation product N
ε
-carboxymethyllysine in the milk proteome. Proteomics 2011; 11:420-8. [DOI: 10.1002/pmic.201000233] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 10/29/2010] [Accepted: 11/10/2010] [Indexed: 11/10/2022]
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27
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Hurt E, Barbano D. Processing factors that influence casein and serum protein separation by microfiltration. J Dairy Sci 2010; 93:4928-41. [DOI: 10.3168/jds.2010-3121] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2010] [Accepted: 06/01/2010] [Indexed: 11/19/2022]
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28
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Zisu B, Bhaskaracharya R, Kentish S, Ashokkumar M. Ultrasonic processing of dairy systems in large scale reactors. ULTRASONICS SONOCHEMISTRY 2010; 17:1075-81. [PMID: 19948420 DOI: 10.1016/j.ultsonch.2009.10.014] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Revised: 10/09/2009] [Accepted: 10/22/2009] [Indexed: 05/23/2023]
Abstract
High intensity low frequency ultrasound was used to process dairy ingredients to improve functional properties. Based on a number of lab-scale experiments, several experimental parameters were optimised for processing large volumes of whey and casein-based dairy systems in pilot scale ultrasonic reactors. A continuous sonication process at 20 kHz capable of delivering up to 4 kW of power with a flow-through reactor design was used to treat dairy ingredients at flow rates ranging from 200 to 6000 mL/min. Dairy ingredients treated by ultrasound included reconstituted whey protein concentrate (WPC), whey protein and milk protein retentates and calcium caseinate. The sonication of solutions with a contact time of less than 1 min and up to 2.4 min led to a significant reduction in the viscosity of materials containing 18% to 54% (w/w) solids. The viscosity of aqueous dairy ingredients treated with ultrasound was reduced by between 6% and 50% depending greatly on the composition, processing history, acoustic power and contact time. A notable improvement in the gel strength of sonicated and heat coagulated dairy systems was also observed. When sonication was combined with a pre-heat treatment of 80 degrees C for 1 min or 85 degrees C for 30s, the heat stability of the dairy ingredients containing whey proteins was significantly improved. The effect of sonication was attributed mainly to physical forces generated through acoustic cavitation as supported by particle size reduction in response to sonication. As a result, the gelling properties and heat stability aspects of sonicated dairy ingredients were maintained after spray drying and reconstitution. Overall, the sonication procedure for processing dairy systems may be used to improve process efficiency, improve throughput and develop value added ingredients with the potential to deliver economical benefits to the dairy industry.
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Affiliation(s)
- Bogdan Zisu
- Dairy Innovation Australia Ltd., Werribee, VIC, Australia
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29
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Chevalier F, Kelly AL. Proteomic quantification of disulfide-linked polymers in raw and heated bovine milk. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2010; 58:7437-7444. [PMID: 20504025 DOI: 10.1021/jf1010879] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Disulfide bond formation between milk protein molecules was quantified in raw and heated bovine milk using reducing and nonreducing two-dimensional electrophoresis. Analysis of protein profiles in raw milk indicated that 18% of alpha(S2)-casein, 25% of beta-lactoglobulin, and 46% of kappa-casein molecules were involved in disulfide-linked complexes (calculated through differences in spot volumes on two-dimensional electrophoretograms under reducing and nonreducing conditions), whereas levels of alpha(S1)- and beta-caseins were similar under both conditions. Following heat treatment at 90 degrees C for 30 min, spot volumes of serum albumin, beta-lactoglobulin, and kappa-casein decreased by 85%, 75%, and 75%, respectively, with the formation of several spots on nonreducing gels corresponding to polymers. Homopolymers and heteropolymers of kappa-casein and alpha(S2)-casein were identified by mass spectrometry in raw milk samples; polymers involving only alpha(S2)-casein or only kappa-casein accounted for 43% and 12% of the total polymers present, respectively. In addition, 45% of polymers in raw milk involved alpha(S2)-casein in association with other proteins as heteropolymers, indicating the key role of this protein in intermolecular disulfide bridging between proteins in raw milk. The intensity of monomeric kappa-casein spots decreased progressively with heating time at 90 degrees C, with greatest changes in spots with acidic isoelectric points. Interactions and association of milk proteins via disulfide bridges are discussed in relation to the proteins involved and their potential protective function against formation of fibril aggregates.
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Affiliation(s)
- François Chevalier
- School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
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MOUNSEY JOHNS, O’KENNEDY BRENDANT. Stability of β-lactoglobulin/micellar casein mixtures on heating in simulated milk ultrafiltrate at pH 6.0. INT J DAIRY TECHNOL 2009. [DOI: 10.1111/j.1471-0307.2009.00522.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Jeong SG, Ham JS, Kim DH, Ahn CN, Chae HS, You YM, Jang AR, Kwon IK, Lee SG. Research on the Quality Characteristics of Domestic Colostrum according to the Processing Methods Employed. Korean J Food Sci Anim Resour 2009. [DOI: 10.5851/kosfa.2009.29.4.457] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Chevalier F, Hirtz C, Sommerer N, Kelly AL. Use of reducing/nonreducing two-dimensional electrophoresis for the study of disulfide-mediated interactions between proteins in raw and heated bovine milk. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2009; 57:5948-5955. [PMID: 19526987 DOI: 10.1021/jf900518n] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The composition and interactions of proteins in bovine milk, and modifications resulting from milk storage and processing, are complex and incompletely understood. Analysis of the milk proteome can elucidate milk protein expression, structure, interaction, and modifications. Raw milk was analyzed by two-dimensional electrophoresis (isolelectric focusing followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) under reducing and nonreducing, or combined, conditions, followed by mass spectrometry of separated protein spots; a small number of high-abundance proteins, that is, caseins (alpha(S1)-, alpha(S2)-, beta-, kappa-, and gamma-), beta-lactoglobulin, alpha-lactalbumin, and serum albumin, represented the vast majority of protein spots on the two-dimensional electrophoretograms of raw milk samples, but some cross-linked protein complexes (mainly homopolymers of kappa-casein and alpha(S2)-casein but also some heteropolymeric complexes) were resolved under native/unheated conditions. When skim milk was heated to 90 degrees C for up to 10 min, the level of native whey proteins decreased in parallel with an increase in disulfide-linked complexes, including very complex heteropolymers, for example, casein/whey protein polymers containing multiple species. The analysis strategy used in this study reveals numerous disulfide-mediated interactions and can be proposed to analyze reduction/oxidation of milk and dairy product proteins following processing treatments applied for processing and storage.
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Affiliation(s)
- François Chevalier
- Department of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
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Abstract
SummaryThe action of rennin in milk subjected to the ultra-high-temperature heat sterilization process has been studied. The primary phase of rennin action, as determined by the release of peptides soluble in trichloroacetic acid, was partially inhibited as a result of the heat treatment. This was largely due to a reduction in the release of non-carbohydrate-containing peptides from κ-casein. It is suggested that when whole milk is heated the formation of a complex between β-lactoglobulin and κ-casein proceeds more readily with the species of κ-casein which lacks carbohydrate. Evidence is presented which shows that there may be more than one type of carbohydrate moiety attached to κ-casein.
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Abstract
SummaryThe heat denaturation of α-lactalbumin (α-la) in NaCl and KCl solutions, milk ultrafiltrate and milk was studied using the method of micro complement fixation. It was established that this protein was very resistant to heat denaturation and that it was more stable in milk ultrafiltrate than in the other media studied at temperatures up to 70 °C. Of the various milk proteins added to α-la, only β-lactoglobulin (β-lg) formed a heat-induced complex with this protein. This complex was identical in milk ultrafiltrate or in milk and depended on the molar ratio between both proteins; it was not modified by any other milk proteins. The binding of a-la to β-lg changed the ability of the latter protein to bind κ-casein.
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Reviews of the progress of Dairy Science: The bacteriological, chemical, biochemical and physical changes that occur in milk at temperatures of 100–150 °C. J DAIRY RES 2009. [DOI: 10.1017/s002202990002361x] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Heat-induced changes in sulphydryl and disulphide levels of β-lactoglobulin A and the formation of polymers. J DAIRY RES 2009. [DOI: 10.1017/s0022029900015995] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
SummaryThe effects of heat and pH on sulphydryl (–SH) and disulphide (–SS–) groups of β-lactoglobulin (β-lg) A have been studied by heating at different temperatures and pH values in air and at pH 6·9 in the absence of air. At pH 6·9 under aerobic conditions a decrease of –SH groups and an increase of –SS– groups was observed with increasing time and temperature. Only small changes were found under anaerobic conditions. At pH from 3·0 to 9·8 the –SH level decreased while the –SS– level increased up to pH 6·9 and then dropped rapidly. In addition to –SH/–SS– interchange there were reactions to other sulphur-containing compounds as seen from the losses in the total amount of –SH plus –SS– sulphur. The results of gelchromatographic investigations suggest that –SH-initiated –SS– exchange-reactions play an important role in the formation of high molecular weight polymers of β-lg A during heat treatment, and that the formation of intermediates depends on the presence of air.
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Heat stability of milk: pH-dependent dissociation of micellar κ-casein on heating milk at ultra high temperatures. J DAIRY RES 2009. [DOI: 10.1017/s0022029900024481] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
SUMMARYPreheating milk at 140 °C for 1 min at pH 6·6, 6·8, 7·0 or 7·2 shifted the heat coagulation time (HCT)/pH profile to acidic values without significantly affecting the maximum stability. Whey proteins (both β-lactoglobulin and α-lactalbumin) co-sedimented with the casein micelles after heating milk at pH < 6·9 and the whey protein-coated micelles, dispersed in milk ultrafiltrate, showed characteristic maxima–minima in their HCT/pH profile. Heating milk at higher pH values (> 6·9) resulted in the dissociation of whey proteins and κ-casein-rich protein from the micelles and the residual micelles were unstable, without a maximum–minimum in the HCT/pH profile. Preformed whey protein–casein micelle complexes formed by preheating (140 °C for 1 min) milk at pH 6·7 dissociated from the micelles on reheating (140 °C for 1 min) at pH > 6·9. The dissociation of micellar-κ-casein, perhaps complexed with whey proteins, may reduce the micellar zeta potential at pH ≃ 6·9 sufficiently to cause a minimum in the HCT/pH profile of milk.
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Effects of iodate, hydrogen peroxide and dichromate on the denaturation of whey proteins in heated milk. J DAIRY RES 2009. [DOI: 10.1017/s0022029900024699] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
SUMMARYThe effect of heating raw milk at 75 °C for 30 min and at 95 °C for 15 s in the presence of varying concentrations of three oxidizing agents on the denaturation of total and individual whey proteins was measured. At 75 °C, ±-lactalbumin could be protected against denaturation by both iodate and H202 and ²-Lactoglobulins A and B by H202 and dichromate. However, at concentrations above ∼ 15 MM, the oxidizing agents tended to increase denaturation. At 95 °C, where the extent of whey protein denaturation was much reduced in the absence of oxidizing agents, little or no protective effect was observed. It is suggested that H202 may prove a suitable alternative to iodate in reducing deposits in ultra high temperature plants.
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Structural changes in whole milk during the production of sterile concentrates: an electron microscope study. J DAIRY RES 2009. [DOI: 10.1017/s0022029900013558] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
SummaryElectron microscopy was used to study the effect of addition of NaOH, forewarming, homogenization, concentration, and heat sterilization on the structure of whole milk during the production of 4 heat-sterilized concentrates that showed different degrees of physical stability. The samples were prepared for electron microscopy by adding fixative either to liquid or freeze-dried material, and then embedding for sectioning.Noticeable structural changes occurred during forewarming of samples containing added NaOH, during homogenization, and during heat sterilization. Addition of NaOH and forewarming decreased the closeness of packing of the subunits in the casein micelles. Homogenization reduced the average size of the fat globules, and protein became attached to their surfaces. Heat sterilization caused coalescence of protein. In non-homogenized sterilized concentrate with added NaOH, protein bodies of about 100 times the volume of the original casein micelles were formed; these were free-floating and the concentrate was stable. In non-homogenized sterilized concentrate with no added NaOH the protein bodies were about 15 times the size of the casein micelles and bridged to each other, thereby forming a sediment consisting of large irregular particles. Very large protein bodies containing fat globules formed during heat sterilization of the homogenized samples, both in the presence and in the absence of NaOH, and were responsible for the formation of sediment in these 2 products.Needle crystals observed in most samples were identifed as CaCO3. H2O by selected area diffraction; KC1 crystals were also detected.
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Abstract
SummaryThe heat stability of a standard reconstituted skim-milk preparation has been investigated as a function of pH, temperature of coagulation, and forewarming treatment. Apparent activation energies have been calculated from the temperature dependence of coagulation time, and a constant value of 144 kJ/mole has been found for milks between pH 6·6 and 6·9. The effect of forewarming resulted in a decrease in stability at the most acid pH values, a slight increase at higher pH but below the pH maximum, and a decrease in the region of the pH minimum. A working hypothesis is proposed for the mechanisms leading to the coagulation of milk at elevated temperatures, based upon Ca induced precipitation of casein, protein polymerization, β-lactoglobulin: κ-casein interaction, and precipitation of insoluble Ca phosphates.
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Ultrafiltration with a microfiltration membrane of acid skimmed and fat-enriched milk coagula: hydrodynamic, microscopic and rheological approaches. J DAIRY RES 2009. [DOI: 10.1017/s0022029900027485] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
SummaryThe effect of acidification method (microbiological with or without renneting, HCl addition) on mass transfer, fouling structure and the rheology of the retentate was studied in the ultrafiltration of skim milk coagula using a mineral microfiltration membrane. The increase in fouling with time appeared to determine permeate flow rates, which were higher in biological coagula, and the protein retention rates which were higher in chemical coagula. Fouling was investigated using scanning electron microscopy. The rheological study showed that at the same total solids, biological coagula were more viscous than chemical coagula. The initial coagula (total solids 97 g/kg) all displayed pseudoplastic behaviour at low shear velocities and Newtonian behaviour at high velocities. Ultrafiltration of fat-enriched milk coagulum to a dry weight corresponding to a soft cheese (total solids 334 g/kg; fat in total solids 60%) gave satisfactory permeate flow rates and protein retention rates. Performance was related to the composition of the product, the hydrodynamic parameters used and the resulting fouling. The rheological study showed that the initial coagulum behaved as a pseudoplastic body at low shear rate and for higher velocities as a Newtonian liquid. The concentrated retenate behaved as an ideal viscoplastic body (Bingham body).
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Heat stability of recombined milk: influence of lecithins on the heat coagulation time-pH profile. J DAIRY RES 2009. [DOI: 10.1017/s0022029900030429] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
SummaryTwo types of lecithin, namely egg and soya lecithin, were investigated as potential stabilizers of recombined milk. They were incorporated into recombined milk both before and after homogenization (20·7 MPa; 60 °C). Their presence at homogenization changed neither mineral equilibria nor homogenization efficiency. However, heat stability varied significantly irrespective of batch of low-heat skim milk powder used in recombined milk. The variation in heat stability depended on type of lecithin. Soya lecithin proved to be a very effective stabilizer. It improved heat stability over a wide pH range (6·3–7·1) and the effect occurred even when the lecithin was added after homogenization. In contrast, egg lecithin destabilized the system to heat at pH < 6·7 by converting a Type A into a Type B heat coagulation time-pH profile if it was incorporated before homogenization; after homogenization it had no effect. The effects of both egg and soya lecithin on the heat stability of recombined milk strongly suggest that interactions occur between phospholipids and milk protein.
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Effect of sulphydryl-blocking agents on the primary phase of chymosin action on heated casein micelles and heated milk. J DAIRY RES 2009. [DOI: 10.1017/s002202990002029x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Interactions between the bovine milk fat globule membrane and skim milk components on heating whole milk. J DAIRY RES 2009. [DOI: 10.1017/s0022029900030430] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
SummaryHeating raw milk at 80 °C for 2·5–20 min was found to result in compositional changes in the milk fat globule membrane (MFGM). The yield of protein material increased with the duration of heating, owing to incorporation of skim milk proteins, predominantly β-lactoglobulin, into the membrane. Lipid components of the MFGM were also affected, with losses of triacylglycerols on heating.
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Abstract
SummaryThe effect of temperature and time of heating whole milk on the renninclotting time, the primary phase of rennin action and the protein (mainly β-lactoglobulin) soluble in 2% trichloroacetic acid (TCA), have been studied. Considerable changes in these parameters occurred above 60°C. The primary phase was inhibited (the degree of inhibition being both temperature and time-dependent), the clotting time was increased, and the protein soluble in 2% TCA decreased considerably.It is suggested that the inhibition of the primary phase was due to complex formation between κ-casein and β-lactoglobulin, the increase in clotting time to a combination of complex formation and a change in the distribution of Ca, and the decrease in β-lactoglobulin to both its interaction with κ-casein and its heat denaturation. The relevance of such changes to the heat stability of milk is discussed.
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Abstract
SUMMARYThe effect of preheating skim milk and artificial micelle milk on curd syneresis was studied. The inhibition of syneresis caused by heat was dependent on the presence of β-lactoglobulin (β-lg) and to a lesser extent α-lactalbumin. The degree of inhibition increased with increasing amounts of added β-lg and preheating temperature. This agrees with the hypothesis that the detrimental effect of preheating on syneresis is due to complex formation between β-lg and κ-casein. This complex appeared to be mediated via thiol–disulphide exchange and its formation appeared to interfere with the micelle–micelle interactions responsible for syneresis.
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Abstract
SummaryThe interaction of β-lactoglobulin and κ-casein at high temperature was studied polarimetrically. The rate of interaction was related to the genetic variant of β-lactoglobulin present. β-Lactoglobulin B, whose thermodenaturation was faster than that of A variant, interacted more rapidly with κ-casein than did the A variant. Velocity sedimentation studies indicated that characteristics of the complex were determined more by the β-lactoglobulin than by the κ-casein. The presence of κ-casein during the thermodenaturation of β-lactoglobulin appeared to prevent the aggregation of β-lactoglobulin from proceeding to completion, the κ-casein complexing with intermediate species and restricting the aggregation process.
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Abstract
SummaryHeating milk at 140 °C caused an initial increase in the percentage of total casein sedimented at 10000 g for 1 h and in the relative viscosity, but as heating continued both parameters decreased before increasing again just before the onset of visible coagulation. This suggests that heating milk at high temperatures caused an initial aggregation of casein micelles with a concomitant increase in particle size and weight, followed by dissociation of these aggregates with reaggregation just before coagulation. Chromatography of heated milk on controlled pore glass confirmed the above suggestion. Calcium appeared to play a major role in the initial association of casein micelles which was also influenced by the initial pH and total solids concentration but whey protein had no effect.
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Abstract
SummaryThe rennet coagulation times of infant milk formulae or fresh skim milk (milk) samples heated at temperatures in the range 70–140 °C for 1–10 min decreased on acidification, usually to pH < 6·0. Heated milk samples acidified to pH 5·5 and reneutralized to pH 6·6 retained good rennet coagulability. Acidification of such milk samples before heating also reduced the adverse effect of severe heat treatment (95 °C for 1 min) on rennet coagulation. Addition of low concentrations of CaCl2to heated milks offset the adverse effects of heating. Acidification of heated milks increased the [Ca2+], and reneutralization of acidified milk only partly restored the [Ca2+], i.e. acidified/reneutralized milk had a higher [Ca2+] than normal milk, suggesting this as the mechanism via which acidification/neutralization improves the rennet coagulability of heated milk. Approximately 50% of the whey protein can be incorporated into rennet gels in heated milks while retaining good coagulability and curd tension; this may be a useful technique for increasing cheese yield.
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Abstract
SummaryThe composition and weight of deposit formed in all sections of an ultra-high-temperature milk sterilization plant were determined. Deposits formed in the preheating, heating and cooling sections during sterilization of pasteurized whole milk were analysed for dry matter, protein, fat and mineral contents. The weight and composition of components of the deposit varied in different sections of the plant and with the heating temperature. Two categories of deposit could be distinguished: one in the preheating section consisting of (w/w) protein 50%, minerals 40% and fat 1% and another in the heating section consisting of minerals 75%, proteins 15% and fat 3%. Concerning the rate of formation of these deposits, a comparison of the results with those obtained for pasteurization shows that fouling was more rapid during pasteurization of raw milk than during sterilization of previously pasteurized milk. Hypotheses concerning mechanisms of formation of protein deposition are discussed.
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