Effect of Trehalose on the State of Water,Protein Denaturation and Gel-Forming Ability of Weever Surimi

The freshness and gel-forming ability of surimi decreased during frozen storage, while trehalose inhibits biological damage at low temperatures and stabilizing protein structures during freezing and freeze-drying. This study investigated the effect of trehalose at different concentrations (2.5–10 g/100 g wet materials) on the state of water, protein denaturation, and gel-forming ability of weever surimi during frozen storage at ?18°C for 90 days. The addition of trehalose increased the unfrozen water amount, regardless of level of addition differences, resulting decreased inactivation rate of calcium-adenylpyrophosphatase, and increased gel-breaking force and gel deformation of weever surimi throughout the frozen storage. Therefore, the addition of trehalose increased the gel-forming ability of weever surimi.     

Effect of heat treatment on milk protein functionality at emulsion interfaces. A review

Heat treatment affects the molecular structure of milk proteins at the interfaces of oil-in-water emulsions and in aqueous media. Experimental evidence of the impact of thermal processing on milk protein structure is presented and the contribution of whey proteins and caseins at film formation during emulsification is discussed. Recent advances in understanding the effect of heat treatment in milk protein functionality at emulsion interfaces are reviewed with particular emphasis on the emulsifying ability of whey proteins with or without the presence of the casein fraction. The major findings regarding the destabilizing mechanisms of oil-in-water emulsions brought about by heat-induced denaturation of milk proteins are presented. This paper aims to combine recent knowledge on how thermal processing of milk proteins affects their molecular configurations in bulk and particularly at interfaces, which in turn appear to be important with respect to the physico-chemical properties of milk protein-stabilized emulsions.     

Suppression of thermal denaturation of myosin and salt-induced denaturation of actin by sodium citrate in carp (Cyprinus carpio)

The effect of sodium citrate (Na-citrate) on myosin and actin denaturation in myofibrils was investigated. Na-citrate significantly suppressed the thermal inactivation of Ca²⁺-ATPase of carp myosin in a concentration-dependent manner. The effect was greater than that of sorbitol. A similar effect was observed with myofibrils in which myosin is stabilized by F-actin binding. Na-citrate dissolved myofibrils at lower concentration than NaCl. Nevertheless, Na-citrate at 1 M failed to denature F-actin in myofibrils, while 1 M NaCl denatured F-actin almost completely. Na-citrate suppressed the NaCl-induced F-actin denaturation. Sorbitol did not show such protective effect on F-actin denaturation. Moreover, Na-citrate suppressed the freeze denaturation of myofibrils at lower concentration than sorbitol. Thus, Na-citrate was proved to be superior to sorbitol. It was suggested that Na-citrate alone could substitute sorbitol as cryoprotectant in surimi and NaCl as dissolving reagent of myofibril in thermal gel production.     

The antigenic response of<Emphasis Type="Italic"> β</Emphasis>-lactoglobulin is modulated by thermally induced aggregation

The antigenic response of thermally denatured and aggregated -lactoglobulin was determined by an indirect competitive enzyme-linked immunosorbent assay using polyclonal antibodies from the egg yolk of chicken immunized with heat-denatured -lactoglobulin as a measure for the potential antigenicity/allergenicity. The heat denaturation and the aggregation of heated whey protein isolate solutions were followed by reversed-phase high-performance liquid chromatography and photon correlation spectroscopy. Thermally modified whey proteins showed a remarkable increase of antigenicity when heated to 90 °C, possibly as a consequence of the exposure or formerly hidden epitopes. Above 90 °C, the antigenic response decreased owing to the loss of conformational epitopes and masking of sequential epitopes in the course of aggregation to particles. When large and compact particles were formed, the antigenicity was reduced remarkably. Depending the heating conditions applied, the structure and the size of whey protein particles and thus the potential allergenicity may be modulated in a wide range.     

Isolation and characterization of acid and pepsin-solubilized collagens from the skin of balloon fish (Diodon holocanthus)

Acid-solubilized collagen (ASC) and pepsin-solubilized collagen (PSC) were successfully extracted from the skin of balloon fish (Diodon holocanthus) with yields of 4% and 19.5% respectively (based on dry weight). According to the electrophoretic patterns, both the ASC and PSC consisted of two different α chains (α1 and α2), were characterized to be type I, and contained imino acid of 179 and 175 residues/1000 residues, respectively. The PSC had a lower content of high-molecular weight cross-links than the ASC. The ultraviolet (UV) absorption spectrum of collagens showed that the distinct absorption was between 210 and 230 nm. A maximum solubility in 0.5 M acetic acid was observed at pH 1–5, and a sharp decrease in solubility above 4% (w/v) in both the ASC and PSC was observed in the presence of NaCl. The denaturation temperatures (T_d) of the ASC and PSC measured by viscometry were 29.01 °C and 30.01 °C, respectively. The maximum temperatures (T_max) of the ASC and PSC were 29.64 °C and 30.30 °C, respectively.     

Formation of protein nanoparticles by controlled heat treatment of lactoferrin: Factors affecting particle characteristics

Lactoferrin is a globular protein from milk that has considerable potential as a functional ingredient in food, cosmetic and pharmaceutical applications. In this study, we examined the possibility of preparing food-grade bovine lactoferrin (bLf) nanoparticles using a simple thermal processing method. Differential Scanning Calorimetry (DSC), light scattering, and ζ-potential techniques were used to provide information about the conformational changes, aggregation, and electrical charge of bLf in aqueous solutions. DSC studies indicated that the protein had two thermal denaturation temperatures (61 and 93 °C), which were associated with two different lobes of the protein. Protein denaturation was found to be irreversible, which was attributed to the formation of protein nanoparticles, whose size depended on the temperature and duration of the thermal treatment. Higher holding temperatures produced faster protein aggregation and larger protein nanoparticles: 85 > 80 > 75 > 70 °C. The protein nanoparticles produced by thermal treatment were resistant to subsequent changes in pH (from 3 to 11) and to salt addition (0–200 mM NaCl). The lactoferrin nanoparticles produced in this study may be useful as function ingredients in commercial products.     

混合溶剂降低蛋白质醇变性机理的探讨

对醇洗法制备花生浓缩蛋白时，乙醇浓度与产品溶解性的关系进行了研究。采用混合溶剂制备花生浓缩蛋白，可获得蛋白质变性程度低、溶解性好的产品，对其原因进行了理论探讨