Developments in understanding and assessment of egg and egg product quality over the last century

The hen's egg, in the form of table eggs and egg products, forms a staple part of the world's total protein consumption. In the last century, there has been considerable research effort focusing on ways of improving egg production and enhancing the quality of eggs. More recently, and with the development and application of new molecular technologies, our understanding and knowledge of how an egg is formed, what it actually consists of, in terms of its major versus minor components, and what the functional roles of each of these components might be, have been greatly enhanced. For example, new previously unknown molecules with specific activity or functional properties have been discovered in the egg albumen and yolk, some of which have potential uses in pharmaceutical and other food related applications. This review paper, which is the collaborative effort of members of Working Group 4 - Quality of Eggs and Egg Products - of the European Federation of WPSA, describes the scientific research behind a number of these major advances and provides some insight to the focus of current research in this area

Incorporating evolutionary processes into a spatially-explicit model: exploring the consequences of mink-farm closures in Denmark

In this paper, we present an individual-based cellular lattice model, which is based on a real landscape (Denmark). The model predicts the distribution of free-ranging mink from data collated on the geographic locations of fur farms, the number of breeding mink kept per farm, and a range of parameters regarding escape, reproduction, mortality, and dispersal. When evolution was incorporated in the model, the results showed that the degree of adaptation within the free-ranging mink population is likely to vary spatially, with lower adaptation in areas where farm mink density is highest (due to the greater number of escaping mink). We used the model to explore the potential consequences of closing mink farms, or limiting escapes from them, on the evolutionary ecology of the free-ranging population and found that depending upon the paramaterisation of the evolutionary processes, several different outcomes are possible. Closing mink farms may result in a crash of the free-ranging population, or alternatively it may result in the establishment of a better-adapted, truly feral population that may ultimately outnumber the population that was present before farm closures. The main purpose of this paper is to raise awareness of the potential importance of evolutionary processes for the naturalisation of mink in Denmark. and to highlight the need for further work. Future field studies should be targeted to reduce the uncertainty in key parameters, allowing the development of an improved version of this model that can be used to generate management recommendations. More generally, we believe. that further work linking evolutionary and population biology is required particularly in an applied context. There are likely to be many further scenarios where evolutionary processes may hold the key to understanding both population and community dynamics.</p

Plasmin Activity in UHT Milk: Relationship between Proteolysis, Age Gelation, and Bitterness

Plasmin, the major indigenous protease in milk, is linked to quality defects in dairy products. The specificity of plasmin on caseins has previously been studied using purified caseins and in the indigenous peptide profile of milk. We investigated the specificity and proteolytic pathway of plasmin in directly heated UHT milk (>150 degrees C for <0.2 s) during 14 weeks of storage at 20 degrees C in relation to age gelation and bitter peptides. Sixty-six peptides from alpha(s)- and beta-caseins could be attributed to plasmin activity during the storage period, of which 23 were potentially bitter. Plasmin exhibited the highest affinity for the hydrophilic regions in the caseins that most probably were exposed to the serum phase and the least affinity for hydrophobic or phosphorylated regions. The proteolytic pattern observed suggests that plasmin destabilizes the casein micelle by hydrolyzing casein casein and casein calcium phosphate interaction sites, which may subsequently cause age gelation in UHT mil

Plasmin activity as a possible cause for age gelation in UHT milk produced by direct steam infusion

The effect of enzymatic activity in direct steam infusion heat treated milk with ultra-short holding times (>150 degrees C for <0.2 s) on age gelation during storage was investigated. Preheating at either 72 or 95 degrees C for 180 s was performed. Milk pre-heated at 72 degrees C showed extensive proteolysis and exhibited bitter off flavour and contained <40% intact alpha(s)- and beta-caseins after 6 weeks storage at 20 degrees C. No proteolysis of kappa-casein was detected. Plasmin was identified as active protease and activation of plasminogen was observed as an increase in the rate of casein hydrolysis. Proteolysis in the stored samples correlated with a decrease in pH and with changes in colour. Gelation occurred after 10 weeks along with an increase in viscosity and extensive proteolysis of alpha(s)- and beta-caseins. In conclusion, plasmin activity was involved in age gelation and bitterness caused by proteolysis was the shelf-life limiting factor. (C) 2014 Elsevier Ltd. All rights reserved

The determination of plasmin and plasminogen-derived activity in turbid samples from various dairy products using an optimised spectrophotometric method

A spectrophotometric assay for plasmin and plasminogen-derived activity in dairy products was optimised and extended to determine plasmin and plasminogen-derived activity in turbid samples of dairy products. The method was validated by assessing reproducibility, repeatability, level of detection and recovery of plasmin activity in different sample matrices. Plasmin activity in raw milk was not affected by skimming, but decreased by 30% in pasteurised and homogenised whole milk, leading to an underestimation of plasmin activity. The effects of dissociation of plasmin and caseins by epsilon-aminocaproic acid (EACA) plus NaCl on the plasmin activity were investigated. Comparison of pasteurised milk with a micellar casein solution showed that the dissociation of plasmin and caseins on adding EACA and NaCl decreases interference by caseins, but increases inhibition of plasmin with serum-based inhibitory components. The level of detection and repeatability of this method for plasmin activity analysis were improved compared with previous spectrophotometric assays. (C) 2014 Elsevier Ltd. All rights reserved

Improved food functional properties of pea protein isolate in blends and co-precipitates with whey protein isolate

Much attention has been drawn to the utilization of plant proteins as food ingredients because of an increasing demand for protein-rich foods with improved nutritional and functional properties. One method to meet these exigencies is co-precipitation. The aim of this study was to evaluate solubility, foaming and emulsification properties of whey protein isolate (WPI) and pea protein (PPI) blends and understand the impact of co-precipitation. Co-precipitates and protein blends in parallel ratios were compared and functional properties were studied at pH 3, 7 and 11.5. The functional properties increased at higher pH. Overall, PPI hampered the functional properties. Co-precipitation improved the functional properties of PPI, where samples with WPI > PPI showed promising results. Improvements could also be obtained by simply blending of PPI and WPI. In fact, protein blends were superior in solubility and foaming capacity, while no significant difference could be obtained for foam stability and emulsifying properties. Thus, the results demonstrate that co-precipitation is not a necessity to partly replace animal proteins in food formulations with plant protein