Jianlian Huang

Determining the effects of microwave heating on the ordered structures of rice starch by NMR

The effects of microwave heating on the double helices, single helix and amorphous structures and the relative crystallinity of rice starch were studied by (13)C CP/MAS NMR method, with rapid heating in an oil bath and conventional slow heating as controls. The results indicated that compared with rapid heating, microwave heating did not significantly change the ordered and disordered structures. All of the heating methods exhibited similar content changes to the double helices, V-type single helix and amorphous structures with rising temperature. The rapid heating effects caused by microwave and oil bath accelerated the destruction of the V-type single helix in the starch granules. The electromagnetic effect of microwave heating did not affect the decrease of the double helices or the amorphous content of the starch.

Structural variation of rice starch in response to temperature during microwave heating before gelatinisation

Although it is well known that structural variations occur in starch during gelatinisation, little is known about how the structure of starch changes at subgelatinisation levels. The objective of this study was to investigate structural variations of rice starch ascribed to the temperature during microwave heating. Rapid conduction heating was used to imitate the high microwave heating rate through oil bath, which was then compared with traditional conduction heating. Structural changes due to temperature increases were investigated using thermogravimetry and differential scanning calorimetry while the distinct lamellar organisation of starch was obtained through small-angle X-ray scattering. The results showed that the structure of starch responds non-monotonically to temperature rising before gelatinisation, which was also affected by heating rates. The samples treated by microwave and rapid conduction heating essentially underwent the same thermal property changes and the molecular vibration of the microwaves did influence the submicroscopic lamellar structure.

Enhancement of the Gelation Properties of Surimi from Yellowtail Seabream (Parargyrops edita, Sparidae) with Chinese Oak Silkworm Pupa, Antheraea pernyi

In this study, the textural properties and micromechanism of yellowtail seabream (Parargyrops edita, Sparidae) surimi, with and without Chinese oak silkworm pupa homogenate (SPH), were investigated at different levels. The fresh, freeze-dried, and oven-dried SPH all showed a gel-enhancing ability in suwari (40/90 °C) and modori (67/90 °C) gels, in a concentration-dependent manner. Though the drying treatments can improve the storability of SPH, compared with fresh, the effect of the active substance was weakened. Suwari and modori gels added with 5%(w/w, whole product) fresh SPH had the increase in breaking force and deformation by 37.39% and 47.98%, and 85.14% and 78.49%, respectively, compared with the control gel (without SPH addition). The major myofibrillar protein, especially myosin heavy chain (MHC), was better retained by the addition of SPH. Compared the control group, a finer, denser, and more ordered 3-dimensional gel network microstructure was obtained, and different Df (Fractal dimension) was analyzed by using the box count method. This was found in all samples from 2.838 to 2.864 for suwari gels and 2.795 to 2.857 for modori gels, respectively. Therefore, the modori of yellowtail seabream surimi, linked with endogenous proteases, could be retarded in the presence of SPH, leading to an increase in gel strength.

Colloidal Gold Probe-Based Immunochromatographic Strip Assay for the Rapid Detection of Microbial Transglutaminase in Frozen Surimi

Adding microbial transglutaminase (MTGase) to frozen surimi to enable the surimi to be sold as a higher-grade product at a higher price defrauds surimi product manufacturers and undercuts legitimate industry prices. Therefore, it is important to develop an accurate method of detecting the presence of MTGase in surimi. In this study, an immunochromatographic strip assay with a colloidal gold antibody probe was successfully developed and used to rapidly and qualitatively detect MTGase in surimi samples. The results were obtained in less than 10 min. The limit for the qualitative detection of MTGase using the immunochromatographic strip assay was identified as 1.0 μg/mL. The results of the immunochromatographic strip analysis of frozen surimi samples were verified by comparison with the results of a sandwich enzyme-linked immunosorbent assay. The colloidal gold probe-based immunochromatographic strip assay was thus found to be a rapid, economical, and user friendly method of detecting MTGase in surimi.

Protein structural development of threadfin bream (Nemipterus spp.) surimi gels induced by glucose oxidase

This study investigated the effect of glucose oxidase on the gel properties of threadfin bream surimi. The gel strength of surimi increased with the addition of 0.5‰ glucose oxidase after two-step heating. Based on the results of the chemical interactions, the hydrophobic interaction and disulfide bond of glucose oxidase-treated surimi samples increased compared with the control samples at the gelation temperature and gel modori temperature. The surface hydrophobicity of samples with glucose oxidase and glucose increased significantly (p < 0.05) and total sulfhydryl groups decreased significantly (p < 0.05). The analysis of Raman spectroscopy shows that the addition of glucose oxidase induced more α-helixes to turn into a more elongated random and flocculent structure. Glucose oxidase changes the secondary structure of the surimi protein, making more proteins depolarize and stretch and causing actomyosin to accumulate to each other, resulting in the formation of surimi gel.

Intervention of transglutaminase in surimi gel under microwave irradiation

Transglutaminase (TGase) was selected as model enzyme to investigate the effects of microwave (MW) heating on its activity and structure compared to water bath (WB) heating. MW heating can enhance the activity of TGase and reach the maximum at 20 min, whereas conduction heating has little effect on the activity of TGase. The difference of dielectric properties between MW heating and WB heating were not obvious, but MW heating had higher conductivity than WB heating. The results of ultraviolet and fluorescence spectra show that MW heating can change the enzyme activity by changing the conformation of TGase. The decrease of α-helix and an increase of β-sheet and β-turn investigated by circular dichroism (CD) indicated the secondary structures of TGase were changed when treated by MW heating. Further gel properties test confirmed that TGase treated by MW could improve the functional and mechanical properties of surimi gel.

Concentration-related microwave heating processes: electromagnetic interference of Maillard reaction substrates (glucose and lysine)

Glucose and lysine are important substrates involved in the Maillard reaction. The lack of studies on their electromagnetic properties has made it impossible to understand the influence of electromagnetic properties on the microwave heating process, and has hindered the application of the Maillard reaction in the microwave field. In this study, the electromagnetic properties of glucose, lysine solution and their 1 : 1 mixture were determined at frequencies of 1.7–2.6 GHz. The results show that the dielectric loss factors gradually increased. Reflection loss gradually decreased with concentration in the order of glucose > mixture > lysine. The heating rates gradually increased at low concentrations (≤5%) and slowly changed at high concentrations (≥10%). These results indicate that the effect of electromagnetic properties on the heating rate is related to concentration. The heating rates depended on the dielectric properties at low concentrations (≤5%), whereas microwave-absorption properties dominated at high concentrations (≥10%).

Improvement of the Quality of Surimi Products with Overdrying Potato Starches

This study investigated the effect of overdrying potato starches on surimi products. The chemical composition of protein and chemical interactions, gel solubility, and protein conformation of the mixture of surimi gel protein, respectively, with 8% native potato starch and with 8% overdrying potato starch were investigated. The results show that the starch increased the insoluble protein content. In terms of the chemical interactions, the overdrying potato starch increased the amount of hydrogen bond and nondisulfide covalent bond and decreased the amount of ionic bond, which might stabilize the network structure of protein gel. The analysis of Raman Spectroscopy shows that more α-helices turn into random coin structure after the starch was added, which is conducive to higher strength and a better water retention ability of the surimi product.

Effect of glucono-δ-lactone on the structural characteristics of red seabream (Pagrosomus major) surimi

The influences of glucono-δ-lactone (GDL) on the structural characteristics of red seabream (Pagrosomus major) surimi gel were studied in terms of protein components, secondary structure and aggregation of protein under pasteurisation conditions. The results showed that most of the salt-soluble protein form a gel, and a small amount of water-soluble protein plays a role in the addition of GDL under low-temperature heating conditions during surimi gel formation. The active sulfhydryl content of actomyosin increased but the total sulfhydryl content decreased as the content of GDL increased. The percentage of β-folds increase and that of α-helices decreased as the content of the GDL increased. SDS-PAGE results suggest that adding GDL can induce more MHC cross-linking and that the degree of cross-linking is higher than that in the high-temperature treatment samples.