Fengfeng Wu

Improved stability and controlled release of ω3/ω6 polyunsaturated fatty acids by spring dextrin encapsulation

Food grade biopolymers, such as dextrin, have been suggested as a technological solution for the controlled delivery of health promoting substances. The main focus of this work is to improve the stability of poly-unsaturated fatty acids (PUFAs) and controlled release by encapsulating with helical spring dextrin (SD). The encapsulation was formed between SD with a DP¯ of 62 and α-linolenic acid (ALA) or linoleic acid (LA) at 60 °C and characterized by WXRD, DSC, TGA and SEM. Under conditions which simulated the human environment of the gastrointestinal system, 21.7% and 18.5% of SD-ALA and SD-LA were released, respectively. A molecular dynamics simulation indicated that the space of helix cavity for ALA-SD complex was larger than that for LA-SD complex. This research work supports the idea that these complexes not only can improve the stability of ALA and LA, but also can achieve the targeted delivery of functional lipids or other bioactive components to the small intestine.

Naturally Occurring Angiotensin I-Converting Enzyme Inhibitory Peptide from a Fertilized Egg and Its Inhibitory Mechanism

This study was performed to investigate the angiotensin I-converting enzyme (ACE) inhibitory activity of peptides derived from fertilized eggs and elucidate the inhibition mechanism of these peptides. During incubation, ACE inhibitory activity of the peptides remained stable before day 12 and then increased markedly on day 15. Two ACE inhibitory peptides, VGVIKAVDKKAGGAGKVT and HLFGPPGKKDPV, were purified from peptides on day 15 by consecutive chromatography. Because HLFGPPGKKDPV possessed a higher ACE inhibitory activity (IC50 = 125 μM), an antihypertensive effect of this peptide was further evaluated in vivo. The result showed that this peptide had an antihypertensive effect in spontaneously hypertensive rats (SHRs) at a dosage of 10 mg/kg. Furthermore, Lineweaver-Burk plots suggested that HLFGPPGKKDPV played as a non-competitive inhibitor against ACE, as supported by docking simulation. These data indicated that a fertilized egg has potential as antihypertensive components in functional foods and nutraceuticals.

Effect of frozen storage on the foaming properties of wheat gliadin

In this study, the effect of frozen storage on the foaming properties of wheat gliadin was investigated and further elucidated by evaluating its physicochemical changes. The foaming volumes of gliadin solution decreased while the foaming stability increased during the frozen storage. This was directly attributed to decreased gliadin content and increased foam density and protein concentration involved in the foams. A more rigid conformation was observed when the frozen storage time increased: the α-helix structure increased at the cost of β-sheet and unordered structure with the decreased surface hydrophobicity and increased surface tension of gliadin aqueous solutions. The percentage of γ-gliadin within gliadin foams gradually decreased, indicating that γ-gliadin was the most sensitive to freezing and the main contributor to the weakened foaming properties during the frozen storage. This study extended the knowledge of gliadin deterioration upon frozen storage and might contribute to the better understanding of frozen dough quality loss.

Fractionation and reconstitution experiments provide insight into the role of wheat starch in frozen dough

The wheat dough was subjected to freezing/thawing treatment for 0, 3, 7, and 10 cycles and fractionated into non-gluten proteins and starch. High-performance liquid chromatography revealed changes in molecular mass distribution occurred for the extracted non-gluten proteins. As for the residual starch, it reflected a loss of chemical components such as amylose, proteins and lipids induced by freezing treatment. X-ray diffraction revealed increased crystallinity in separated starch as the freezing cycle was repeated. Rapid visco-analyser exhibited different pasting behaviors on starch pellets, especially on the breakdown and setback viscosities. In the reconstituted dough, an increase was observed in storage and loss modulus, corresponding to the presence of freezing/thawing-treated starches, which was changed as a result of higher water absorption. These results extended the knowledge of starch granules in dough deterioration upon freezing process and might contribute to the better understanding of frozen dough quality loss.

Particle size distribution of wheat starch granules in relation to baking properties of frozen dough

The impact of freezing on the wheat starches with different particle size was studied using a range of characterization methods including X-ray diffraction, differential scanning calorimetry, the Rapid Visco Analyser and a reconstitution dough system. Wheat starches were fractionated into A- and B-type granules, and then subjected to freezing/thawing treatment for 3 cycles. The freezing treatment did not cause apparent damage on A-type granular surface but induced cracked structure on B-type granules. It facilitated materials such as amylose, proteins, and lipids leaching from starch granule and an increase in gelatinization temperatures, melting enthalpy, and pasting viscosities. A smaller bread specific volume was obtained from freezing-treated B-granules while the crumb firmness significantly increased (p>0.05). No marked differences were observed in the counterparts of A-granules after freezing treatment. It seemed that the B-type granules were more sensitive to the freezing/thawing treatment, thus facilitating structural transformations from dough to bread. Results indicated that the deterioration in frozen bread quality derived from starch could be minimized by increasing the A-granules content.

Preparation of phosvitin-dextran conjugates under high temperature in a liquid system.

The conjugation reaction between phosvitin (Pv) and dextran (Dex) in an aqueous solution at the initial stage of Maillard reaction was investigated in this study. The formation of Pv-Dex conjugates was indirectly traced by measuring the absorbance at 200 nm in the UV-vis spectrophotometer. The content of free amino groups in the glycosylated Pv decreased to 77.4% after reaction for 6 h. The new band near the loading end of SDS-PAGE gel also suggested the high molecular weight products developed after conjugation. The shift of the main peak of Pv in size exclusion-high performance liquid chromatography from 9.16 min to 8.87 min and the minor peak from 6.56 min to 6.13 min confirmed the formation of covalent conjugates. Circular dichroism (CD) spectra demonstrated that significant changes of the secondary structure occurred to the grafted Pv. The optimum conjugation condition chosen was per Pv (5 mg/ml) glycosylated with 4-fold dextran (Mw, 40 kDa) at 100 °C for 6 h.

Effect of Germination on Flavor Volatiles of Cooked Brown Rice

ABSTRACT The effect of germination on flavor volatiles of cooked brown rice among three different rice cultivars was investigated using the headspace solid-phase microextraction method combined with gas chromatography-mass spectrometry. The results showed that some flavor compounds varied significantly throughout the germination process and others did not show distinct changes. The amount of total volatiles, most lipid-oxidation products, and phenolic compounds decreased in the initial stage of germination but increased significantly at a later stage. The amounts of ethanol and ethyl acetate increased significantly in the initial stage of germination and maintained almost the same levels during further germination. The amount of dimethyl sulfide increased significantly during germination; it showed the most significant change among all volatile compounds.

Postfertilization changes in nutritional composition and protein conformation of hen egg.

Fertilized hen egg is traditionally considered as a dietary supplement in many Asian countries. This work aimed to obtain information on the effect of fertilization on total nutritional composition of egg contents and protein conformation. Chemical analysis showed that the lipid level in fertilized egg began to decrease after day 9. Fertilized egg before day 9 was higher in essential free amino acids (EFAA) and monounsaturated fatty acids (MUFA) contents but lower in cholesterol and polyunsaturated fatty acids (PUFA) than unfertilized counterparts. Fertilized egg proteins were characterized by an increase in hydrophobicity and a decrease in electrostatic interaction. Circular dichroism analysis showed that β-sheet decreased with increasing incubation time, whereas unordered structure increased. The findings observed in this work provide a crucial basis for understanding nutritional composition and protein conformation of fertilized egg, with the potential of being utilized as an EFAA/MUFA-rich, low-cholesterol dietary supplement.

Tuneable surface enhanced Raman spectroscopy hyphenated to chemically derivatized thin-layer chromatography plates for screening histamine in fish

Reliable screening of histamine in fish was of urgent importance for food safety. This work presented a highly selective surface enhanced Raman spectroscopy (SERS) method mediated by thin-layer chromatography (TLC), which was tailored for identification and quantitation of histamine. Following separation and derivatization with fluram, plates were assayed with SERS, jointly using silver nanoparticle and NaCl. The latter dramatically suppressed the masking effect caused by excessive fluram throughout the plate, thus offering clear baseline and intensive Raman fingerprints specific to the analyte. Under optimized conditions, the usability of this method was validated by identifying the structural fingerprints of both targeted and unknown compounds in fish samples. Meanwhile, the quantitative results of this method agreed with those by an HPLC method officially suggested by EU for histamine determination. Showing remarkable cost-efficiency and user-friendliness, this facile TLC-SERS method was indeed screening-oriented and may be more attractive to controlling laboratories of limited resource.

Impact of germination on nutritional and physicochemical properties of adlay seed (Coixlachryma-jobi L.)

Adlay has garnered a great deal of research attentions in recent years as a highly nutritious food material and herbal medicine. This study characterized the changes of nutritional and physicochemical properties of adlay seeds during a 60-h germination. The results showed that the 60-h germination brought about a 3.4-fold increase in γ-aminobutyric acid (GABA) and 3.6-fold increase in coixol compared to ungerminated adlay seeds, while the triolein content slightly decreased. Some high molecular proteins were hydrolyzed into smaller proteins, peptides and amino acids after germination. Scanning electron micrographs (SEM) showed that the germination process destroyed the continuous matrix structure of adlay flour and created pits and holes on the surface of some starch granules. Germination resulted to changes in the pasting and gelatinization properties of adlay flour. The results of present study suggest that germination efficiently enhances the nutritional compounds while altering the physicochemical characteristics of adlay seeds.