Physicochemical, microstructure and bioactive characterization of gels made from crayfish protein

Study on the Mechanism of Modified Cellulose Improve the Properties of Egg Yolk gel

Natural fiber is not suitable for modifying yolk gel as a modifier because of its large size and high compactness. In this study, two kinds of modified cellulose were selected to improve the thermal gel properties of yolk. The results showed that the two kinds of cellulose promoted the formation of ordered structure in yolk gel. The ordered gel network not only improved the texture properties and rheological properties, but also improved the water retention of yolk gel significantly. CMC and CNFC at the same concentration, the modification effect of CMC on yolk gel was better than CNFC because of its excellent dispersion. However, high concentration of CNFC (1.20-1.60%) disrupted the cross-linking and ordered structure formation of yolk protein, and the quality of gel was significantly reduced.

Combined effects of isolation temperature and pH on functionality and beany flavor of pea protein isolates for meat analogue applications

The combined effects of isolation temperature (20, 30 and 40 °C) and pH (2.0-12.0) on yield, techno-functional properties, and beany flavor of pea protein isolates were investigated. Increasing pH from 2.0 to 9.5 and 11.0 increased yields from 37 % to 75 % and 79 %, respectively, at 20 °C. At a constant pH, increasing temperature from 20 to 40 °C did not increase protein recovery; rather, negatively affected the techno-functional properties such as protein solubility, foaming and gelation. Protein isolated at pH 11.0 (20 °C) provided a higher fat absorption, gelation capacity, gel hardness, cohesiveness, chewiness, and gumminess than at pH 9.5, due to higher protein denaturation as supported by their higher surface hydrophobicity. Volatile beany flavor marker hexanal was predominant in all isolates than the starting material, irrespective of isolation temperature, probably due to lipid oxidation. The results provide a basis for tuning the isolation process for producing pea protein isolates with desired techno-functional properties for meat analogue applications.

Characterization of four thermogelled egg yolk varieties based on moisture and protein content

There are obvious differences between egg yolks of different varieties. Additionally, boiled eggs, which are widely liked and consumed globally, are nutrient rich. However, they absorb water in the esophagus during swallowing, and this result in an uncomfortable sensation. Here, we determined the moisture content and distribution as well as the protein contents and properties of 4 varieties of thermogelled egg yolks. Among the varieties, Green Shelled thermogelled egg yolk showed the highest protein content and solubility. Additionally, the ionic, hydrogen, and disulfide bonds corresponding to Rhode Island Red thermogelled egg yolk samples were the weakest, while the hydrophobic interaction force corresponding to the Hetian Dahei (HD) egg yolk samples was the weakest. Further, the distribution of the moisture contents of the 4 varieties was significantly different (P < 0.05). HD egg yolk showed the highest moisture content, and its bound and immobile moisture contents were significantly higher than those of the other 3 varieties. Egg yolk moisture content also affected free amino acid content, which was the highest for HD egg yolk. Therefore, owing to its high moisture content, HD egg yolk was conducive for chewing and swallowing and given its high free amino acid content, it also had a more suitable taste and flavor. The results of this study provide a theoretical basis for the application of egg yolks in food processing.

Functionalization Routes for Keratin from Poultry Industry Side-Streams-Towards Bio-Based Absorbent Polymers

Keratin is a largely available protein that can be obtained from the ca. 3 million tons of feathers that the European poultry industry produces as a side-stream. Here, the functionalization of keratin from poultry feathers was evaluated using a one- versus two-stage process using two functionalization agents (succinic anhydride-SA and ethylene dianhydride-EDTAD). The functionalization resulted in the keratin having improved liquid swelling capacities, reaching up to 400%, 300%, and 85% increase in water, saline, and blood, respectively, compared to non-functionalized keratin. The highest swelling was obtained for samples functionalized with EDTAD (one-stage process), while the highest saline uptake was noted for samples processed with 25 wt% SA (two-stage process). Swelling kinetics modeling indicated that the water uptake by the functionalized samples takes place in two steps, and the EDTAD samples showed the highest diffusivity. It is demonstrated that the one-stage functionalization of keratin utilizing EDTAD results in better performance than two-stages, which allows for resource-saving and, thereby, protecting the environment. The results show some potential for the keratin to be utilized as liquid absorbent materials in water, saline, and blood uptake applications. Using keratin from side-streams is an advantage from a sustainability perspective over biomacromolecules that need to be extracted from virgin biomass.

Detection of Zoonotic Bacteria and Paragonimus kellicotti in Red Swamp Crayfish (Procambarus clarkii) and the Assessment of Traditional Crayfish Boils

ABSTRACT

Studies of red swamp crayfish (Procambarus clarkii) outside of the United States confirm the presence of a variety of zoonotic pathogens, but it is unknown whether these same pathogens occur in P. clarkii in the United States. The U.S. commercial crayfish industry generates $200 million yearly, underscoring the need to evaluate this consumer commodity. The study objectives were to evaluate specific zoonotic pathogens present on P. clarkii from Alabama and Louisiana, states in the southeastern United States, and to determine the effectiveness of traditional food preparation methods to reduce pathogens. Experiment A evaluated the presence of Escherichia coli, Salmonella, Staphylococcus aureus, and Vibrio spp. in crayfish and environmental samples over a 2-month collection period (May to June 2021). Crayfish sampling consisted of swabbing the cephalothorax region; 15 samples were tested for E. coli, Salmonella, and S. aureus, and an additional 15 samples for Vibrio spp. Additionally, crayfish shipping materials were sampled. In experiment B, 92 crayfish were evaluated for Paragonimus kellicotti. Experiment C compared live and boiled crayfish for the presence of Vibrio spp. In experiments A and B, all 60 (100%) crayfish samples and 13 (81.25%) of 16 environmental samples showed growth characteristic of Vibrio spp. Three (5%) of 60 samples showed E. coli growth, with no statistical difference (P = 0.5536) between farms. P. kellicotti, Salmonella, and S. aureus were not recovered from any samples. In experiment C, all 10 (100%) of the live preboiled crayfish samples showed characteristic growth, whereas 1 (10%) of 10 samples of crayfish boiled in unseasoned water showed Vibrio growth (P < 0.0001). These results confirm that Vibrio spp. and E. coli may be present on U.S. commercial crayfish and that care should be taken when handling any materials that come into contact with live crayfish because they can potentially be contaminated.

HIGHLIGHTS

Acidic and Heat Processing of Egg Yolk Dispersions

Egg yolk is a multifunctional ingredient widely used in many food products, wherein proteins are the dominant component contributing to this functionality. However, the potential risk of foodborne illness associated with egg use forces us to ensure that foodstuffs based on egg yolk are managed in a safe and sanitary manner. Lowering the pH under a certain value by adding acids could serve this purpose, but it can also greatly modify the rheological and functional properties of egg yolk. This research aims to assess the influence of citric acid on the rheological properties and microstructure of chicken egg yolk dispersions and their heat-set gels. The dispersions were prepared from fresh hen’s eggs yolks by adding water or citric acid to obtain a technical yolk (45 wt.% in solids) at the desired pH value. Viscoelastic measurements were carried out using a control stress rheometer, and microstructure was evaluated by cryo-scanning electronic microscopy (CryoSEM). An evolution of the viscoelastic properties of egg yolk dispersions from fluid to gel behavior was observed as the pH decreased until 2 but showing a predominantly fluid behavior at pH 3. The profile of viscoelastic properties along the thermal cycle applied is modified to a great extent, also showing a strong dependence on pH. Thus, the sol–gel transition can be modulated by the pH value.

Gelation behavior of egg yolk under physical and chemical induction: A review

Gelation is one of the most important functional properties of egg yolk. High content and rich variety of protein and lipid in egg yolk are the material basis of gel formation. The natural structure of proteins in egg yolk is unfolded under treatments such as heat, alkali, salt, etc., thus causing the interactions between protein-protein and protein-lipid and forming the gel. Under different methods of induction, egg yolk is solidified to form different three-dimensional network structures. Different inducing methods exhibit different gel formation mechanisms. In this paper, the gelation behavior of egg yolk and its internal molecular agglomeration mechanism induced by heat, alkali, salt, freezing, high pressure, and salt-heating synergy were reviewed to provide a reference for further studies on the formation mechanisms and product development of egg yolk gel.

Spiny-Cheek Crayfish, Faxonius limosus (Rafinesque, 1817), as an Alternative Food Source

The aim of the study was to present a comprehensive characterisation of crayfish meat, which is crucial to assess its potential usefulness in the food industry. To this end, we assessed the yield, basic chemical composition (protein, fat, minerals), nutritional value (amino acid and fatty acid profiles, essential amino acid index (EAAI), chemical score of essential amino acids (CS), hypocholesterolaemic/hypercholesterolaemic ratio (h/H), atherogenicity (AI) and thrombogenicity (TI) indices), as well as culinary value (lab colour, texture, sensory characteristics, structure) of the meat of spiny-cheek crayfish (Faxonius limosus) (n = 226) from Lake Sominko (Poland) harvested in May-September 2017. Crayfish meat, especially that from the abdomen, was shown to have high nutritional parameters. It is lean (0.26% of fat), with a favourable fatty acid profile and a very high quality of fat (PUFA (sum of polyunsaturated fatty acids):SFA (sum of saturated fatty acids), n-6/n-3, h/H, AI, TI) and protein (high CS and EAAI). It is also a better source of Ca, K, Mg, Na, P, and Cu than meat from slaughter animals. Hence, crayfish meat can be an alternative to livestock meat in the human diet. Owing to its culinary value (delicateness, weak game flavour, and odour), it meets the requirements of the most demanding consumers, i.e., children and older people.

Effects of temperature on quality of preserved eggs during storage

The effects of storage temperature (4°C, 25°C, and 35°C) on sensory quality, physicochemical properties, texture, molecular forces, flavor, and microbial indexes of preserved eggs were studied. The results showed that the sensory quality, weight loss rate, pH, and color of preserved eggs were significantly different at different storage temperatures (P < 0.05). Compared with high temperature and normal temperature storage, low temperature storage reduced weight loss rate by 55.15 and 64.1%, respectively, improved the sensory score (P < 0.05), inhibited the reduction of pH and the increase of total volatile base nitrogen (P < 0.05), and decreased the change of color (P < 0.05). During storage, there was no difference in the springiness of preserved egg white stored at different temperatures (P > 0.05). Hardness and chewiness at 3 different temperatures increased first and then decreased, and low temperature significantly inhibited the progress of these changes to a certain extent (P < 0.05). The content of ionic bond in egg white first decreased and then increased, and content of disulfide bond increased first and then decreased. Content of ionic bond in yolk decreased all the time, and high temperature could promote this change. Whatever the temperature was, the content of free amino acids in preserved egg white and yolk increased first and then decreased, and the total content of amino acids stored at different temperatures was significantly different (P < 0.05). The content of free fatty acids in yolk decreased. At the end of storage, no microorganisms were detected in 3 temperatures during the storage period of 84 D. The results showed that low temperature storage is more conducive for preservation of preserved eggs.

Purification and identification of an antioxidative peptide from peony (Paeonia suffruticosa Andr.) seed dreg

The present study demonstrated the hydrolysis of peony seed protein isolate (PSPI) by using alcalase and resulted in the generation of an anti-oxidative peptide. In brief, a model was used to illustrate the enzymolysis of PSPI with the determination of kinetic factors as per investigation information. The model proved suitable to explain the PSPI hydrolysis by alcalase. A novel anti-oxidative peptide was obtained successfully by ultrafiltration and a series of chromatography techniques. Subsequently, a purified fragment was identified with the amino acid sequence of SMRKPPG followed by its synthesis and evaluation of its anti-oxidative activities. After hydrolysis, the peony seed protein hydrolysate (PSPH) with the degree of hydrolysis of 18% displayed the most significant antioxidant action which was further used to isolate the anti-oxidative peptide.