Effect of High Pressure Treatment on Rheological Characteristics of Egg Components

Effect of processing technologies on the digestibility of egg proteins

Egg and egg products are a rich source of highly bioavailable animal proteins. Several processing technologies can affect the structural and functional properties of these proteins differently and can influence their fate inside the gastrointestinal tract. The present review examines some of the processing technologies for improving egg protein digestibility and discusses how different processing conditions affect the digestibility of egg proteins under gastrointestinal digestion environments. To provide up-to-date information, most of the studies included in this review have been published in the last 5 years on different aspects of egg protein digestibility. Digestibility of egg proteins can be improved by employing some processing technologies that are able to improve the susceptibility of egg proteins to gastrointestinal proteases. Processing technologies, such as pulsed electric field, high-pressure, and ultrasound, can induce conformational and microstructural changes that lead to unfolding of the polypeptides and expose active sites for further interactions. These changes can enhance the accessibility of digestive proteases to cleavage sites. Some of these technologies may inactivate some egg proteins that are enzyme inhibitors, such as trypsin inhibitors. The underlying mechanisms of how different technologies mediate the egg protein digestibility have been discussed in detail. The proteolysis patterns and digestibility of the processed egg proteins are not always predictable and depends on the processing conditions. Empirical input is required to tailor the optimization of processing conditions for favorable effects on protein digestibility.

Mechanism of enhancing foaming properties of egg white by super critical carbon dioxide treatment

The effect of supercritical carbon dioxide (SCCD) treatment at varying processing time (30-90 min) on foaming and structure properties of egg white protein (EWP) were studied in this paper. The highest foaming ability (107.7%) was obtained after 60 min SCCD treatment, which was 3.6-fold to the control group. Foaming stability kept stable under the processing time of 75 min. Results of surface tension, surface hydrophobicity, rheological properties and particle size indicated that protein was easier to spread to the gas-liquid interface and generate molecular rearrangement. Circular dichroism (CD) and Endogenous fluorescence spectrum showed that there were slight changes on the secondary structure of EWP. The α-helical structure of the protein was destroyed and the particle size became uneven, which indicated that the protein structure became more flexible and loose. The results of this study indicate that SCCD treatment had a potential to be implemented to enhance foaming properties of EWP.

Modifying the Functional Properties of Egg Proteins Using Novel Processing Techniques: A Review

Egg proteins can be used in a wide range of food products, owing to their excellent foaming, emulsifying, and gelling properties. Another important functional property is the susceptibility of egg proteins to enzymatic hydrolysis, as protein digestion is closely related to its nutritional value. These functional properties of egg proteins are likely to be changed during food processing. Conventional thermal processing can easily induce protein denaturation and aggregation and consequently reduce the functionality of egg proteins due to the presence of heat-labile proteins. Accordingly, there is interest from the food industry in seeking novel nonthermal or low-thermal techniques that sustain protein functionality. To understand how novel processing techniques, including high hydrostatic pressure, pulsed electric fields, ionizing radiation, ultraviolet light, pulsed light, ultrasound, ozone, and high pressure homogenization, affect protein functionality, this review introduces the mechanisms involved in protein structure modification and describes the structure-functionality relationships. Novel techniques differ in their mechanisms of protein structure modification and some have been shown to improve protein functionality for particular treatment conditions and product forms. Although there is considerable industrial potential for the use of novel techniques, further studies are required to make them a practical reality, as the processing of egg proteins often involves other influencing factors, such as different pH and the presence of other food additives (for example, salts, sugar, and polysaccharides).

Can acceptable quality angel food cakes be made using pasteurized shell eggs? The effects of mixing factors on functional properties of angel food cakes

Due to recent Salmonella outbreaks, the pasteurized shell egg market is rapidly growing. One objection to using pasteurized eggs is the belief that they will produce unacceptable angel food cakes. Eggs were pasteurized using a hot water immersion process (56.7°C for 60 min) similar to that used by industry. Angel food cakes were made from the pasteurized egg white (PEW) as well as from raw egg white (REW) for comparison. Meringues were made using three mixer speed settings (low, medium, and high) and three durations for each speed. Functional qualities such as egg foaming were evaluated. Angel food cakes were compared in terms of cake volume, texture profile, and color values. When the optimal processing factors used for REW were applied to PEW, an inferior meringue was formed. However, by increasing the mixing time for PEW by 200% at the highest speed, an acceptable meringue was formed. The best angel food cake prepared from PEW had a volume only 6.8% less than that of the best cake prepared from REW. Texture profile analyses showed that the best angel food cake made from PEW was 13% firmer, 7.4% less springy, and 62% chewier than that from REW. Color analyses showed that PEW made a slightly darker colored cake crust than REW, although there were no significant differences in the crumb color. Modifying the mixing conditions for PEW resulted in angel food cakes with quality similar to that of cakes made with REW, thus overcoming an objection to using safer pasteurized shell eggs.

Preparation of konjac glucomannan/casein blending gels optimized by response surface methodology and assessment of the effects of high-pressure processing on their gel properties and structure

BACKGROUND

In order to improve the compatibility of polysaccharide-protein mixtures and enhance their performance, a response surface methodology was used to optimize the preparation conditions of konjac glucomannan/casein blend gel. Moreover, the effects of high-pressure processing (HPP) on the gel properties and structure were also investigated.

RESULTS

The optimal preparation parameters were a temperature of 60 °C, a total concentration 40 g kg^-1 , and a dietary alkali concentration 5 g kg^-1 . Under these conditions, the experimental value of hardness was 38.7 g, which was close to the predicted value. HPP increased gel hardness by 161-223% and led to a more compact structure at 200-600 MPa/10 min, while a hardness increase of ∼120% and damaged structure were observed at 600 MPa/30 min. Fourier transform infrared spectroscopy showed that noncovalent interactions are likely the most important factor in the modification of gel hardness; indeed, hydrogen bonding interactions in the gels are enhanced when subjected to HPP, but are weakened at 600 MPa/30 min.

COUCLUSION

Protein-polysaccharide complexes with excellent properties could be obtained through this method, with broad application prospects in the food industry. © 2018 Society of Chemical Industry.