Yang Li

Relationship between Secondary Structure and Surface Hydrophobicity of Soybean Protein Isolate Subjected to Heat Treatment

This study investigated relationship between secondary structure and surface hydrophobicity of soy protein isolate (SPI) subjected to a thermal treatment at 70~90°C. Heat denaturation increased the surface hydrophobicity and surface hydrophobicity decreased as aggregate formed. Heat caused an increase in the relative amount of α-helix structures and an overall decrease in the amount of β-sheet structures when compared with nontreated SPI. The relative amounts of secondary structures varied with time, temperature, and intensity of heat treatment applied. The β-sheet structure was most important for its significant role in denaturation of 7S globulin and following formed aggregates and even in denaturation of 11S globulin. The amount of β-sheet structure in SPI had an inverse correlation with the surface hydrophobicity when the temperature was kept below 90°C. Besides, β-turn structure increased as β-7S/B-11S aggregate formated.

Ultrasound-assisted aqueous enzymatic extraction of oil from perilla (Perilla frutescens L.) seeds

In the present study the effects of ultrasonic pretreatment and the types of enzyme on oil yield were investigated. The optimum ultrasonic pretreatment parameters were found to be 250 W of ultrasonic power, 30 min of ultrasonic time, and 50°C of ultrasonic temperature. Five types of enzyme, Cellulase, Viscozyme L, Alcalase 2.4L, Protex 6L, and Protex 7L, were evaluated for their effectiveness in releasing oil from ultrasonic pretreated perilla seeds. The highest oil yield of 81.74% was observed in cellulase treated perilla seed samples. The physicochemical properties of the control, hexane, and enzyme extracted perilla seed oils were compared. No significant (P > 0.05) differences were observed in iodine value, refractive index, unsaponifiable matter, saponification value, peroxide value, and acid value.

Differential scanning calorimetry study--assessing the influence of composition of vegetable oils on oxidation.

The thermal oxidation of eight different vegetable oils was studied using differential scanning calorimetry (DSC) under non-isothermal conditions at five different heating rates (5, 7.5, 10, 12.5, and 15°C/min), in a temperature range of 100-400°C. For all oils, the activation energy (Ea) values at Tp were smaller than that at Ts and Ton. Among all the oils, refined palm oil (RPO) exhibited the highest Ea values, 126.06kJ/mol at Ts, 134.7kJ/mol at Ton, and 91.88kJ/mol at Tp. The Ea and reaction rate constant (k) values at Ts, Ton, and Tp were further correlated with oil compositions (fatty acids and triacylglycerols) using Pearson correlation analysis. The rate constant (k) and Ea of all oils exhibited varying correlations with FAs and TAGs, indicating that the thermal oxidation behaviors were affected by oil compositions.

Relationship Between Surface Hydrophobicity and Structure of Soy Protein Isolate Subjected to Different Ionic Strength

The impact of ionic strength on surface hydrophobicity, solubility, and spatial structure of soy protein isolate were investigated in this article. Surface hydrophobicity was found to be negatively correlated with its solubility as ionic strength increased. The changes in spatial structure of soy protein isolate accounted for the increased surface hydrophobicity caused by ionic strength. Specifically, changes in secondary structures by increased ionic strength were mainly reflected in the increased random coil and decreased α-helices content, which suggested that ionic effects may loosen the protein structures and result in the modification of surface amino acid distribution. This is further verified by the shifted λmax in fluorescence spectra of tryptophan and relative high I850/I830 value in Raman spectra, which was an indicator of the exposure degree of tyrosine residues on the surface of the protein. In addition, the changes in vibration modes of disulfide bonds reflected by Raman spectra also support the impact of saline on the surface hydrophobicity and structure of soy protein isolate. It is believed that these findings could be helpful to understand the impact of salinity on the surface hydrophobicity of soy protein isolate as well as to predict the other functional characteristics of soy protein isolate in system.

HPLC Analysis of Water-Soluble Vitamins (B2, B3, B6, B12, and C) and Fat-Soluble Vitamins (E, K, D, A, and β-Carotene) of Okra (Abelmoschus esculentus)

Okra is consumed as a vegetable by populations in Africa and Asia and particularly in Egypt. In this study, we investigated some nutritional components of okra grown in four different geographical locations of Egypt. A comparative analysis of water-soluble vitamins (B2, B3, B6, B12, and C) and fat-soluble vitamins (E, K, D, A, and β-carotene) in okra pods was carried out. Results of principal component analysis (PCA) showed three clusters of varieties. The first cluster included the Dakahlia (D) and Kafr El-Sheikh (K) varieties. The second and the third clusters separated out the Suez (S) and Mansoura (M) varieties independently. The S pod showed the highest contents of vitamins B6 (49.81 μg/100 g) and E (1.47 mg/100 g) but contained the lowest contents of vitamins B3 (1.42 μg/100 g) and B12 (undetected). The K pod showed the lowest vitamin C content (11.60 mg/100 g). The M pod showed the highest contents of vitamins B3 (22.70 μg/100 g), B12 (91.20 μg/100 g), C (27.14 mg/100 g), and K (0.21 mg/100 g). The D pod showed the lowest contents of vitamins E (0.15 mg/100 g), K (0.05 mg/100 g), and B6 (11.50 μg/100 g). These findings could help develop meal planning at the community level by incorporating okra varieties with high vitamin content.

Effect of several supplemental Chinese herbs additives on rumen fermentation, antioxidant function and nutrient digestibility in sheep

Two experiments were carried out in this study. Experiment 1 was conducted to examine the effects of several supplemental Chinese herbs on antioxidant function and slaughtered body weight in sheep. Results indicated that Fructus Ligustri Lucidi supplementation improved the blood antioxidant function [higher concentration of glutathione reductase (GR), superoxide dismutase and lower concentration of malondialdehyde] and slaughtered body weight in sheep (p < 0.05). Experiment 2 was conducted to investigate the effect of Fructus Ligustri Lucidi extract (FLLE) on rumen fermentation and nutrient digestibility in sheep. Four levels of FLLE treatments, i.e. 0, 100, 300 and 500 mg/kg dry matter (DM), were used in this part. Addition of FLLE at 300 or 500 mg/kg DM increased total volatile fatty acid (VFA) concentration and propionate proportion, decreased ammonia-N concentration in the ruminal fluid, reduced blood urea nitrogen concentration at 2, 4, 6 and 8 h after morning feeding (p < 0.05). Addition of FLLE at all dosages had no effect on ruminal pH value and acetate concentration at all sampling time points in sheep (p > 0.05). Dynamic degradation coefficient c of maize DM was significantly increased by supplementing FLLE at 300 or 500 mg/kg DM (p < 0.05). Fructus Ligustri Lucidi extract addition had no effect on degradation coefficients a, b, c of DM and nitrogen of soybean meal; a, b of maize DM; a, b, c of maize nitrogen; and a, b, c of neutral detergent fibre (NDF) and acid detergent fibre (ADF) of Chinese wildrye (p > 0.05). Addition of FLLE at 300 or 500 mg/kg DM increased DM and organic matter digestibility of diet (p < 0.05). Fructus Ligustri Lucidi extract addition had no effect on digestibility of diets NDF, ADF and crude protein (p > 0.05). From the aforementioned results, it is indicated that FLLE improved antioxidant status and slaughtered body weight. Fructus Ligustri Lucidi extract addition has capability to modulate rumen fermentation, increase the maize degradation rate, total volatile fatty acid concentration and propionate proportion in sheep.

Effect of ultrasound treatment on the wet heating Maillard reaction between mung bean [Vigna radiate (L.)] protein isolates and glucose and on structural and physico‐chemical properties of conjugates

BACKGROUND The objective of this study was to determine the effect of ultrasound treatment on the wet heating Maillard reaction between mung bean protein isolates (MBPIs) and glucose, and on structural and physico-chemical properties of the conjugates. RESULTS The degree of glycosylation of MBPI-glucose conjugates treated by ultrasound treatment and wet heating (MBPI-GUH) was higher than that of MBPI-glucose conjugates only treated by wet heating (MBPI-GH). Solubility, emulsification activity, emulsification stability and surface hydrophobicity of MBPI-GUH were higher than that of MBPI-GH. Grafted MBPIs had a lower content of α-helix and unordered coil, but a higher content of β-sheet and β-turn structure than MBPIs. No significant structural changes were observed in β-turn and random coil structure of MBPI-GUH, while α-helix content increased with ultrasonic time, and decreased at 300 W ultrasonic power with the increase of β-sheet. MBPI-GUH had a less compact tertiary structure compared to MBPI-GH and MBPI. Grafting MBPIs with glucose formed conjugates of higher molecular weight, while no significant changes were observed in electrophoresis profiles of MBPI-GUH. CONCLUSION Ultrasound-assisted wet heating Maillard reaction between MBPIs and glucose could be a promising way to improve functional properties of MBPIs.

Effect of the interaction between myofibrillar protein and heat-induced soy protein isolates on gel properties

The effect of the interaction between myofibrillar protein (MP) and heat-induced soy protein isolates (SPI) on gel properties was examined. To enhance the interaction between MP and SPI, SPI was subjected to thermal treatments at 60, 80, and 95 °C. The results showed that hydrophobic interactions played the most important role in MP-heated SPI (HSPI) gels. Hydrogen bonds played an important role in stabilizing the mixed gels, but this decreased with increasing heat treatment temperature of SPI. Disulfide bonds were not a significant force stabilizing the mixed gels. The gel properties of HSPI-MP were enhanced significantly (P < 0.05) by the inclusion of preheated SPI (95 °C, 30 min), including hardness, springiness, and water-holding capacity (WHC). Dynamic rheological analysis showed that heat treatment decreased the onset temperature of mixed gels and significantly increased the final G’. Notable cross-linked strands formed in MP-HSPI (80 °C) and MP-HSPI (95 °C) gels, while the smoothest and most ordered gel network structure was observed in the MP-HSPI (95 °C) gel.

Functional and conformational changes to soy proteins accompanying anthocyanins: Focus on covalent and non-covalent interactions

The present study was aimed to evaluate the interaction between anthocyanins from black rice and soybean protein isolate (SPI) via non-covalent and covalent bindings and the impact of these interactions on the functional and conformational changes of soybean protein. The conformational changes of the protein structure with different concentrations of anthocyanins (0.05, 0.1%, and 0.2%) were analyzed using three-dimensional fluorescence and Fourier transform infrared spectroscopy. The anthocyanins were more likely to form covalent interactions with SPI instead of non-covalent interactions. The addition of anthocyanins changed the secondary structure of SPI with a decrease in β-sheets and an increase in β-turns and random coils. The emulsifying and foaming properties of SPI were improved after complexation with anthocyanins. This study might be useful for elucidating the mechanisms behind the binding of anthocyanins with SPI and the possible uses of SPI-anthocyanin complexes in food formulations.

Heating Quality and Stability of Aqueous Enzymatic Extraction of Fatty Acid-Balanced Oil in Comparison with Other Blended Oils

The heating performance of enzyme-assisted aqueous processing-extracted blended oil (EAEPO), hexane-extracted blended oil (HEBO), and three kinds of blended oils was investigated by varying the heating times. Oil degradation was monitored by analysis of the acid value (AV), peroxide value (PV), p-anisidine value (p-AV), color, and trans-fatty acid composition. The fatty acid ratios of EAEPO, HEBO, and the three kinds of blended oils were very similar (0.27 : 1.03 : 0.96, 0.27 : 1.08 : 1.16, 0.27 : 0.65 : 0.8, 0.27 : 0.6 : 0.84, and 0.27 : 0.61 : 0.79, resp.). The AV and color increased in proportion to the heating time for all the oils. There was a rapid increase in the PV and p-AV of EAEPO and HEBO after heating for only 1 h, whereas the other three blended oils showed a rapid increase after heating for 2 h or 6 h. Despite the highest trans-fatty acid content found for HEBO, this content was relatively low and remained low up to a heating time of 8 h. It was found that after heating, a fatty acid ratio relatively close to its ideal value (0.27 : 0.48 : 0.49) was maintained by EAEPO, which indicates that EAEPO is tolerant to heat treatment and is suitable for maintaining a healthy diet.