The formation and deformation of protein structures with viscoelastic properties

This study describes the formation of a gluten substitute. Chapter 1 describes the properties that are necessary to obtain a gluten substitute. Chapter 2 describes the formation and properties of protein particle suspensions. Two proteins with different intrinsic properties, gelatin and whey protein, were selected as model materials. Chapter 3 describes the effects of simple shear flow on the formation and properties of gelatin particle suspensions. The application of well-defined simple shear flow during phase separation was used to control the protein particle size in a gelatin–dextran system. Chapter 4 describes the formation and properties of whey protein particle suspensions having different particle sizes and different abilities to form disulphide bonds. Application of shear during their formation was used. Chapter 5 describes a novel concept for making elastic dough through combining a whey protein particle suspension with native wheat starch. Three differently structured whey protein suspensions were evaluated. Chapter 6 discusses the use of the whey protein particle suspensions prepared and used in chapter 5 for baking bread. Chapter 7 describes the role of molecular properties on the final dough and bread that were discussed in chapters 5 and 6. Chapter 8 summarizes the main findings of the project on “The formation and deformation of protein structures with viscoelastic properties”. </p

Koemelk: Effecten van bewerkingen op gezondheid

A small percentage of the milk consumed in the Netherlands is raw, unprocessed milk. All milk distributed through shops and supermarkets are at least standardized and heat treated (e.g. pasteurized), and most of the consumption milk is homogenized. Yet, some consumers prefer to drink unprocessed, raw milk, because of its taste or expected positive health effect. In this report, the results of a literature research are presented. The changes in the milk as a result of processing and the potential effect of these changes on the health of humans are investigated

Loss of muscle mass in hip fracture patients

Hip fractures in the elderly are often the result of low-energy trauma, such as a simple fall at home or on the street. Skeletal muscles are fundamental for mobility and balance. The decrease in muscle mass with increasing age, in combination with a decrease in muscle strength or muscle function, is called sarcopenia. Sarcopenia is considered a syndrome that increases the risk of vulnerability and predicts physical functional decline, loss of independence, poor quality of life and life expectancy. This dissertation shows that hip fracture patients had already experienced a decline in muscle mass before the fall, and that they had to suffer even more muscle mass loss during hospitalization. A deteriorated nutritional status in hip fracture patients is a known problem. This dissertation shows that muscle building with protein-rich nutritional interventions can be stimulated in the elderly with sarcopenia. Whether nutritional interventions actually result in improved clinical outcomes for hip fracture patients is currently unclear. The effectiveness of nutritional intervention strategies on clinically and physiologically relevant outcome measures in hip fracture patients must be further investigated in the future

Eindrapportage BARAWING project (EETK99033) : de ontwikkeling van een competitief proces voor het verlengen van de houdbaarheid van voedselproducten met behulp van ultra-hoge druk : openbare rapportage

Deze rapportage beschrijft de resultaten die geboekt zijn binnen het BaraWing project (EETK99033). Dit project had als doelstelling het ontwikkelen van een proces en een testpilotscale hogedruk-apparaat voor het kosten-effectief produceren van voedingsmiddelen met een verlengde houdbaarheid bij kamertemperatuur met behulp van hogedruktechnologie (HPP). Het project was op te delen in een drietal hoofdactiviteiten, te weten a) technologie, b) veiligheid (microbiologie) en c) productkwalitei

Fokken voor hogere kaasproductie : niet voer maar met name fokkerij beïnvloedt eiwitsamenstelling in melk

De hoeveelheid melkeiwit per lactatie per koe is meer dan verdubbeld: van 148 kilo in 1960 tot 330 kilo in 2009. Er is echter weinig kennis over de samenstelling van het melkeiwit en de mogelijkheden om deze met behulp van fokkerij te verbeteren. Fokken op het aandeel caseïnes in de melk blijkt haalbaar en dat is lucratief voor de kaasproductie

Biochemical and functional characterisation of casein and whey protein hydrolysates : a study on the correlations between biochemical and functional properties using multivariate data analysis

Whey protein and sodium caseinate were hydrolysed with commercially available enzyme preparations. The resulting hydrolysates were characterised using several analytical characterisation methods and by determination of several functional properties. Subsequently, correlations between the biochemical characteristics themselves and between biochemical and functional properties were studied using multivariate regression analysis.Biochemical characteristics of hydrolysates were determined using unifactorial methods like the degree of hydrolysis, and by multifactorial methods, i.e . reversed phase (RPC) and size exclusion chromatography (SEC), and Fourier transform infrared (FTIR) spectroscopy. FTIR spectroscopy appeared to discriminate most effectively between hydrolysates made from different protein sources and classes of proteolytic enzymes, followed by RPC and SEC.Emulsion and foam properties of hydrolysates were similar or inferior to those of the parental proteins. Casein hydrolysates generally showed better emulsion and foam forming ability than whey protein hydrolysates. Foam forming ability of whey protein hydrolysates was correlated to the molecular weight distribution (MWD) of the peptides, showing that especially peptides with MW of 3-5 kDa contributed to foam forming ability.Concerning prevention of emulsion instability due to coalescence it was shown that peptides with a molecular weight larger than 2 kDa are needed. Foam stabilising ability of casein hydrolysates also depended on the MWD of hydrolysates, but higher molecular weight peptides, i.e. larger than 7 kDa, were needed to obtain good foam stability.The ability of the three multifactorial characterisation methods (SEC, RPC, FTIR spectroscopy) to predict functional properties was investigated. It appeared that SEC profiles were able to predict emulsion and foam stability of all hydrolysates, as well as foam forming ability, Angiotensin Converting Enzyme (ACE) inhibiting ability and bitterness of whey hydrolysates. RPC profiles were also able to predict these properties and additionally predicted solubility and bitterness of casein hydrolysates. FTIR spectra were best suited to predict a variety of hydrolysate properties, since apart from the before-mentioned properties, the spectra can also be used to predict emulsion forming ability and to improve prediction of bitterness of hydrolysates.Finally, the influence of hydrolysis process conditions on ACE inhibiting ability of whey hydrolysates was investigated, showing that ACE inhibiting activity could be optimised by using process optimisation techniques like experimental design and response surface optimisation

Casein - whey protein interactions in heated milk

Heating of milk is an essential step in the processing of various dairy products, like for example yoghurt. A major consequence of the heat treatment is the denaturation of whey proteins, which either associate with the casein micelle or form soluble whey protein aggregates. By combination of enzymatic fractionation and capillary electrophoresis we were able to quantitatively determine the distribution of denatured whey proteins after heat treatment. This thesis describes the relation between these quantitative studies and the acid-induced gelation properties and textural gel properties of milk derived products. In chapter 3 it was demonstrated that more severe heat treatment caused more denaturation and that the whey proteins both associate with the casein micelle and form whey protein aggregates. The formation of these aggregates was visualised and the size was estimated. We clearly demonstrated that at the natural pH of milk the ratio of denatured whey proteins associated with the casein micelle and present in aggregates remained constant and that the observed shift in gelation pH of heated milk is linearly correlated with the two fractions of denatured whey proteins. The shift in gelation pH was more thoroughly studied in chapter 6 and was directly related to whey protein denaturation. It was shown that b-lactoglobulin was principally responsible for the shift in gelation pH. a-lactalbumin caused neither alone nor in combination with b-lactoglobulin an effect on the gelation pH. Chapter 4 reports the effect of pH-adjustment of milk (pH range 6.9 to 6.35) prior to heat-treatment (10 min at 80?C) on the distribution of denatured whey proteins and on the homogeneity of the whey proteins coating of the casein micelles. After heat treatment at pH 6.9 most whey proteins are present in soluble whey protein aggregates while heating at pH 6.55 and lower causes association of all whey proteins with the casein micelle. Heating of milk at pH 6.35 causes a clearly more inhomogeneous coating than heating at pH 6.55. This pH-dependent whey protein denaturation is schematically depicted in a model and related to acid and rennet-induced gelation properties. In Chapter 7 we studied the formation of disulfide linked protein structures during the acidification step at ambient temperature. The time dependent formation of these structures attributed significantly to the mechanical properties of acid milk gels, resulting in gels with an increased storage modulus and hardness. The mechanical properties are shown to be the result of the contribution of denatured whey proteins to the protein network as such and the additional formation of disulfide bonds. Surprisingly, the formation of these disulfide bonds take place at ambient temperature and under acidic conditions. Therefore, the disulfide cross-linking is highly relevant also for textural properties of acid-milk products, like yogurt. In conclusion this work showed that seemingly minor variations in milk treatment may lead to considerable changes in the properties of the end product. Quantitative description will allow better control and tuning of the final gel properties