高密度二氧化碳对鸡蛋全蛋液杀菌效果研究

采用高密度二氧化碳(DPCD)处理鸡蛋全蛋液,研究不同温度和不同压力对大肠杆菌和沙门氏菌的杀灭效果。结果表明,杀菌效果随着温度升高、压力的增加而提高;处理条件为压力15MPa、温度35℃、时间15min时,大肠杆菌和沙门氏菌数量分别降低了3.07、1.89个对数值。     

Effect of egg yolk substitution by sweet whey protein isolate on texture,stability and colour of Gelato‐style vanilla ice cream

Gelato samples were made with two levels of egg‐yolk (4.5 and 9%). For each level, samples were prepared with and without whey protein isolate (WPI). Texture and melting rates values were significantly (P < 0.05) higher in 9% egg‐yolk samples over the storage period than in samples containing 4.5%. Increasing WPI led to a significant increase in hardness at both levels of egg‐yolk. Gelato with added WPI in 9% samples had slightly higher whiteness (L) and yellowness (b) values than 4.5% samples. A significant effect of fat content was observed in all physical properties measured. Results suggest that this approach can deliver functionality at a lower cost and can produce a good quality Gelato.     

Comparative resistance of food proteins to adult and infant in vitro digestion models

IgE‐mediated allergy to milk and egg is widespread in industrialised countries and mainly affects infants and young children. It may be connected to an incomplete digestion of dietary proteins causing an inappropriate immune response in the gut. In order to study this, a biochemical model of infant gastroduodenal digestion has been developed, which has reduced levels of protease (eightfold for pepsin and tenfold for trypsin and chymotrypsin), phosphatidylcholine and bile salts, compared with the adult model. This model has been used to study the behaviour of three characterised food‐relevant proteins (bovine β‐lactoglobulin (β‐Lg), β‐casein (β‐CN) and hen's egg ovalbumin), all of which are relevant cows' milk and hens' egg allergens. Digestion products were characterised using electrophoresis, immunochemical techniques and MS. These showed that ovalbumin and β‐CN were digested more slowly using the infant model compared with the adult conditions. Resistant fragments of β‐CN were found in the infant model, which correspond to previously identified IgE epitopes. Surprisingly, β‐Lg was more extensively degraded in the infant model compared with the adult one. This difference was attributed to the tenfold reduction in phosphatidylcholine concentration in the infant model limiting the protective effect of this phospholipid on β‐Lg digestion.     

Transepithelial transport across Caco-2 cell monolayers of antihypertensive egg-derived peptides. PepT1-mediated flux of Tyr-Pro-Ile

This paper examines the in vitro transepithelial transport of antihypertensive peptides derived from egg proteins using Caco-2 cell monolayers. Ovokinin (FRADHPFL) was absorbed intact through the Caco-2 cell epithelium, although it was also susceptible to the action of brush-border aminopeptidases that yielded shorter fragments prior to their transport. The tripeptide YPI was resistant to cellular peptidases and transported through the monolayer, what suggests that the reduction in systemic blood pressure caused by this peptide may be mediated by effects at tissue level. Its pathway for transepithelial absorption was examined using inhibitors of the different mechanisms for oligopeptide transport in the intestinal tract. The main route involved in the transepithelial flux of YPI is probably the peptide H(+)-coupled transporter PepT1. These results highlight the potential of antihypertensive peptides to be used in the formulation of functional foods.     

A market study on the quality characteristics of eggs from different housing systems

To study the differences among commercial eggs from four housing systems i.e. cage, barn, free range and organic, 41 physical and chemical parameters were evaluated on 28 fresh egg samples from the Italian market. The univariate statistic analysis evidenced that organic eggs had the highest whipping capacity and foam consistency but the lowest freshness (the highest air cell height) and albumen quality (the lowest Haugh Unit); cage eggs presented instead the lowest whipping capacity and the highest shell resistance to breaking. The multivariate technique discriminant partial least-squares regression was unable to correctly classify the eggs from the four housing systems but successfully differentiated cage eggs from alternative (organic + barn + free range) eggs. The variables with the most discriminant power were shell breaking resistance, overrun, protein content, and shell thickness.     

Monitoring the Egg Freshness During Storage Under Modified Atmosphere by Fluorescence Spectroscopy

A total of 207 intact brown-shelled eggs of the same flock (29 weeks of age) belonging to two treatment groups were stored in daylight at 12.2 °C and 87% relative humidity (RH): (1) 108 eggs and (2) 99 other eggs were kept in an atmosphere containing 2 and 4.6% of CO₂, respectively. The 18 remaining eggs have also been analysed directly when they were available in our laboratory to check the degree of freshness (aged of 1 day or less). Eggs of the two groups were analysed after 6, 8, 12, 15, 20, 22, 26, 29, 33, 40, 47 and 55 days of storage using front face fluorescence spectroscopy. The emission fluorescence spectra of aromatic amino acids and nucleic acids (AAA+NA; excitation, 250 nm; emission, 280–450 nm), fluorescent Maillard reaction products (excitation, 360 nm; emission, 380–580 nm) and the excitation spectra of vitamin A (emission, 410 nm; excitation, 270–350 nm) were scanned on thick albumen and egg yolk. For each treatment, the principal component analysis applied on the vitamin A fluorescence spectra allowed a good discrimination of eggs according to both their storage time and conditions, while more overlapping between egg samples was observed when the other intrinsic probes were investigated. These results showed that vitamin A fluorescence spectra could be considered as a good indicator of egg freshness kept only in 2% of CO₂.     

UV Inactivation of E. coli in Liquid Egg White

Liquid egg white is currently pasteurized using heat; however, this treatment damages the functional properties of the egg. In this study, a nonthermal ultraviolet light (UV) system was developed to pasteurize liquid egg white. The system consisted of low-pressure mercury bulbs surrounded by UV transparent tubing. Egg white was inoculated with Escherichia coli K12 and pumped through the UV system at a flow rate of 330 ml/min. The effects of treatment time (0 to 160 s), temperature (30 to 50 °C), and egg white pH (7 to 9) on the inactivation of E. coli were investigated. The population of E. coli in egg white was reduced by 4.3 log after being exposed to UV at 50 °C for 160 s. Inactivation was linearly dependent on treatment time and was adequately described using first-order kinetics (r ² of 0.94). The electrical energy of the process was calculated to be 44 J/ml. Inactivation was directly dependent on temperature and inversely dependent on pH. Nonthermal UV processing has the potential to improve the safety and functional properties of liquid egg white. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture.     

Novel peptides derived from egg white protein inhibiting alpha-glucosidase

The aim of this study was to search and identify potential anti-diabetic peptides with α-glucosidase and α-amylase inhibitory activities. After the Alcalase hydrolysis, egg white protein hydrolysates were purified and identified by LC–MS–MS. Eight identified peptides were further synthesized by the Fmoc solid-phase synthesis. The anti-diabetic activities of these synthetic peptides were assessed using enzymatic inhibitory assays against the α-glucosidase and α-amylase. Among the eight peptides, peptide RVPSLM was discovered as a potential α-glucosidase inhibitor with an IC₅₀ value at 23.07 μmol L⁻¹. However, it did not exhibit a visible or detectable inhibitory efficiency on the α-amylase. These studies indicate the potential of using egg white protein hydrolysates as a functional food product with the anti-diabetic activity.     

Fatty acid composition of eggs produced by the Slovenian autochthonous Styrian hen

The fatty acid composition of eggs produced by the autochthonous Styrian hen reared in two rearing systems was determined. Eggs were collected four times during the year. The fatty acid composition was determined by the in situ transesterification method and gas chromatography–flame ionisation detection (GC–FID). Eggs of the Styrian hen from free range contained significantly more α-linolenic, eicosapentaenoic (EPA), docosapentaenoic (DPA) and docosahexaenoic acid (DHA), as well as more total n−3 fatty acids. On the other hand, eggs from caged hens contained significantly more linoleic, arachidonic, as well as total polyunsaturated fatty acids (PUFA) and n−6 PUFA. The n−6/n−3 ratio was better from the nutritional point of view in eggs from free range. The fatty acid content is expressed in wt.%, as well as mg/100 g of yolk and mg/100 g of fresh egg, to better understand how much each of fatty acid is consumed with an edible portion.     

Lake Superior herring gulls benefit from anthropogenic food subsidies in a prey–impoverished aquatic environment

Herring gulls (Larus argentatus) are used as ecological indicators of the coastal Lake Superior ecosystem in Pukaskwa National Park, Ontario, Canada. Their populations have declined by 70 % over the last 40 years, suggesting changes in the park ecosystem. Previous studies highlighted declining prey abundance as a possible contributing factor to population declines. Here, we assess herring gull diets via stable isotope (nitrogen, carbon) and fatty acid indicators to investigate how diet may influence population trends through effects on physiology (stress-related hormones), reproduction (egg size) and behavior (nest attentiveness). Diets were variable among individual herring gulls. Gulls utilizing anthropogenic food sources exhibited reduced levels of stress-associated hormones, increased egg size, and increased nest attentiveness. Anthropogenic food sources are likely buffering the impacts of declines in aquatic food availability; however, populations are still declining. Understanding factors contributing to population trends in ecological indicator species is critical for species management and for identifying stressors that are likely affecting the broader ecosystem. Herring gulls are archetypal examples of the “canary in a coalmine” indicator but in an ecosystem context. Changes in their diets and in variables associated with their physiology, reproduction, and behavior point to very significant changes occurring in the Lake Superior ecosystem. Integrated research across the Great Lakes is required to understand the extent of this change and its implications for the sustainability of wildlife populations.