Modification Of Milk Proteins Research Articles

The Effects of Microbial Transglutaminase (MTG) Enzyme Usage on Sensory Properties of Hatay Cheese

Hatay Cheese is a kind of cheese produced in and around Hatay with its own shapes and sizes. In this study, the use of microbial transglutaminase enzyme was tried to improve the textural structure of Hatay cheese which is in fresh cheese class. Enzymatic modification of milk proteins by microbial transglutaminase enzyme has been applied in the production of half-fat Hatay cheese with different pre-ripening time applications and some sensory properties of the cheeses have been investigated such as external appearance, internal appearance, texture, odor and taste during 60 days of storage. In this study, four different Hatay cheese were produced as control sample (A), 30 minutes pre-ripening with enzyme (B), 45 minutes pre-ripening with enzyme (C) and 60 minutes pre-ripening with enzyme (D). When the sensory properties of the cheeses were examined, it was observed that the application of different pre-ripening time significantly affected the external appearance, internal appearance, texture and taste scores on the 60th day of storage (p 0.05). The effects of different pre-ripening periods and storage time on the odor scores of the cheeses were not significant (p>0.05). Taste scores of cheese D were significantly affected by storage time (p<0.05). As a result of all sensory analyzes, it was found that the cheeses supplemented with MTG enzyme were more liked and the scores given to the cheeses increased as the pre-ripening period increased. As a result, the most admired cheese was D cheese.

Untargeted Proteomics-Based Profiling for the Identification of Novel Processing-Induced Protein Modifications in Milk.

Nonenzymatic post-translational protein modifications (nePTMs) affect the nutritional, physiological, and technological properties of proteins in food and in vivo. In contrast to the usual targeted analyses, the present study determined nePTMs in processed milk in a truly untargeted proteomic approach. Thus, it was possible to determine to which extent known nePTM structures explain protein modifications in processed milk and to detect and identify novel products. The method combined ultrahigh-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry with bioinformatic data analysis by the software XCMS. The nePTMs detected by untargeted profiling of a β-lactoglobulin-lactose model were incorporated in a sensitive scheduled multiple reaction monitoring method to analyze these modifications in milk samples and to monitor their reaction kinetics during thermal treatment. Additionally, we identified the structures of unknown modifications. Lactosylation, carboxymethylation, formylation of lysine and N-terminus, glycation of arginine, oxidation of methionine, tryptophan, and cysteine, oxidative deamination of N-terminus, and deamidation of asparagine and glutamine were the most important reactions of β-lactoglobulin during milk processing. The isomerization of aspartic acid was observed for the first time in milk products, and N-terminal 4-imidazolidinone was identified as a novel nePTM.

The effect of transglutaminase on colloidal stability of milk proteins

Food industry is on constant search for improved, enzymatically modified forms of proteins, which are the most important functional food ingredients, capable of either introducing or modifying texture, appearance, and flavour. One of the key aspects of food design is creating new functional properties and novel food macro- and microstructures in order to provide tailored food characteristics expected by consumers. Milk proteins are among the most thoroughly studied protein complexes occurring in foods and having a wide range of functionalities. The common usage of milk proteins has also contributed to the development of techniques designed to modify and improve functional properties of milk proteins. The aim of this study was to investigate the impact of enzymatic modification induced by microbial transglutaminase (TGM) in milk proteins on the range of cross-linking as well as heat and ethanol stability of these proteins. Milk used in the study was subjected to various technological processes and then incubated with the enzyme added at an amount of 2 Units g−1 protein for 2 h at 40 °C. Modification of milk proteins by transglutaminase leads to their partial cross-linking and formation of high molecular weight polymers in the range of 55–200 kDa. The changes of cross-links between milk proteins occur most dynamically in the first hour of incubation at 40 °C. Enzymatic modification of milk proteins significantly increases the ethanol stability of raw as well as pasteurized milk and UF concentrate. Addition of transglutaminase does not change the heat stability of milk measured as the time of heat coagulation at 140 °C.Graphical abstract

Oxidative modification of milk proteins at pasteurization

Oxidative modification of milk proteins at pasteurization

Influence of milk protein cross-linking by transglutaminase on the rennet coagulation time and the gel properties.

Transglutaminase (TGase) modifies milk proteins by cross-linking of caseins, with increased cheese yield being the main technological benefit. In the present work the influence of TGase addition in different concentrations (0, 1, 2 and 3 U g(-1) protein in the system) and under different incubation conditions (0 h, 40 °C/2 h, 25 °C/4 h and 5 °C/16 h) on the rennet coagulation time (RCT) and the comprehensive rennet gel properties were investigated. Modification of milk proteins by TGase in a concentration-dependent manner caused longer RCT and lower gel firmness. The highest TGase concentration and incubation at 40 °C for 2 h resulted in the longest RCT and the lowest gel firmness. Rennet gels obtained from TGase modified milk were characterised by significantly lower values of texture parameters, lower syneresis and were composed of smaller casein micelles, thinner chains and smaller clusters than those obtained from the control milk. The content of whey proteins in the gel from modified milk was higher and the content of individual casein fractions in the milk samples and rennet gels decreased upon TGase modification. Rennet cheese with modified textural and nutritional properties and improved yield can be obtained upon TGase modification but simultaneous addition of rennet and TGase is recommended. © 2015 Society of Chemical Industry.

Formation and Gelation Role of Serum Protein Aggregates during the Manufacture of Milk Powder

AbstractThe aim of the present study was to investigate the effects of heat‐related processes during the production of milk powder on aggregation of milk proteins and consequent impacts on the coagulation properties. Compared with raw milk, preheating as well as concentration and subsequent dehydration greatly changed serum protein aggregates, sizes of casein micelles and calcium ion activity, and consequently influenced the textural properties of rennet and acid gels. Moreover, the diversities of these physicochemical and gelling properties were also observed among reconstituted milk powder due to the different preheating or concentration. However, the difference in spray‐drying parameters only affected the intensity of some protein aggregates. It was indicated that all these heat‐related processes should be paid attention during milk powder manufacture in order to control acid or rennet coagulation of reconstituted milk powder.Practical ApplicationsThis study demonstrated the differences in the gelling properties due to the heat‐related processes, i.e., preheating, concentration and spray drying, in the production of milk powder. The information on milk proteins and calcium ion activity would help in understanding their influences on rennet or acid coagulation. The research on the gelling properties of reconstituted milk powder would shed light on the technological application of milk powder such as modification of milk proteins, processing control of milk powder production and suitability of final yogurt or cheese products.

Grasa y proteína de la leche de vaca: componentes, síntesis y modificación

El objetivo de este trabajo fue realizar una revisión de los componentes lipídicos y proteicos de la leche de vaca, ya que los ácidos grasos, las caseínas, y las proteínas del lactosuero, entre otros, poseen una importancia significativa dentro de la nutrición humana. En este ámbito, el consumidor elige entre uno u otro componente, influyendo de manera directa sobre la oferta y la demanda de productos lácteos. Esta dependencia del mercado hacia el consumidor, exige al profesionista involucrado en la producción lechera, una mayor comprensión del suministro de nutrientes a la glándula mamaria, con el fin de adquirir herramientas que le permitan modificar la composición de la leche conforme a las exigencias de la industria láctea. Por lo tanto, se presenta una revisión que enfatiza la utilidad de modelos esquemáticos en procesos metabólicos, para incrementar nuestro conocimiento científico sobre factores como la elongación y desaturación de los ácidos grasos, la transcripción y traducción proteica, y la formación de glóbulos grasos y micelas de caseína, elementos teóricos de vital importancia si se busca alterar la grasa y la proteína láctea. Cabe señalar, que este documento se ha desarrollado con un enfoque bioquímico, lo que le otorga originalidad y lo distingue de otras revisiones enfocadas exclusivamente en la modificación de aspectos nutricionales, y su efecto sobre los componentes de la leche. Adicionalmente, son muy escasas las revisiones actualizadas que abordan esta temática para estudiantes y profesionistas de habla hispana. Finalmente, se analizan reportes científicos y técnicos que consideran la manipulación nutricional, el efecto de la raza, la modificación del ambiente ruminal, y la variabilidad genética, sobre el contenido y la composición química de los lípidos y proteínas de la leche de vaca.

Next issue (April 2007): Milk Processing

AbstractEdited by Prof. Knut Heller, Karlsruhe, Germany.Highlight articles:– Bacteriophages in dairy products: Pros and cons– Liberation of bioactive peptides from milk proteins– Lactobacillus delbrueckii subsp. bulgaricus for yoghurt with mild taste– Prebiotic galacto‐oligosaccharides production using Lactobacillus reuteri– Lactobacillus kefiri biotransformation of pentoxifylline– Modification of milk proteins by microbial transglutaminase... and much more: Read the next issue of BTJ!

Influence of processing on the molecular modifications of milk proteins in the course of enzymic coagulation

SummaryThe formation of hydrophobic sites on the surface of casein micelles as a consequence of enzymic coagulation of industrially heat-treated milk was studied by following the distribution of a fluorescent hydrophobic probe between a free and an aggregated protein fraction. Results were compared with those obtained when coagulation of the same milk samples was followed rheologically in a Gelograph apparatus and by tristimulus colorimetry. Thermal treatment of milk appeared to affect the accessibility of casein to enzyme action, while homogenization influenced the rate of cooperative aggregation of casein subjected to proteolysis.

The Current Status of Genetic Engineering in Domestic Animals

The introduction of foreign genes into domestic animals is now established as a viable technique. Transgenic sheep containing a metallothionein and somatotropin fusion gene have been produced. In these animals, growth rates were always equal to or less than nontransgenic controls, and the animals all died before 12 mo of age. The total fat of the transgenic animals was reduced to about 5 to 7% compared with 26 to 33% in normal ewes, and heat production was substantially elevated in the transgenic animals, apparently because they had a basal metabolic rate about 30% higher than normal. Gross abnormalities were noted in the fore and hind limbs, and the animals developed diabetes immediately prior to death. Our results indicate that precise control over somatotropin expression is required in order for transgenic sheep containing somatotropin fusion genes to be useful in a practical farm situation.Possible areas of future research include further work toward the manipulation of circulating hormones, the modification of milk proteins, and the introduction of new biochemical pathways to domestic animals. The latter area offers considerable potential for improving productivity but requires more knowledge of many of the basic physiological processes that are involved in domestic animal production.

Modification of Milk Proteins by Psychrotrophic Bacteria

Skim milk and casein were inoculated with psychrotrophic bacteria and held 5 days at 7C. Samples then were removed and examined by anion exchange chromatography with diethylaminoethylcellulose in Tris-citrate-urea or phosphate buffer and stepwise addition of sodium chloride. Results of tests on cultured skim milk and casein, when compared to controls, revealed an increase in number of nitrogenous compounds that were eluted from the column before casein and a decrease in the amount of β- and αs-casein. Chromatograms of control and cultured whey proteins were similar, indicating that these proteins were unaffected by the psychrotrophic bacteria.