Impact of sodium citrate on structural properties of gluten.

The effect of sodium citrate on gluten-starch separation and physicochemical properties of gluten was studied. The results showed that the addition of sodium citrate to the dough caused to an improvement in the aggregation of gluten and increased gluten yield in comparison to the control by augmentation pH and approaching to the isoelectric point of glutenin and gliadin. Also, sodium citrate led a shift to larger particle size distribution of glutenin macropolymer (GMP). These observations demonstrated that under the influence of sodium citrate more thiol groups were oxidized and formed disulfide bonds, which increased the storage modulus and resistance to extension. Furthermore, in this sample the GMP gel was more elastic and stiffer.

Stability of astaxanthin-loaded nanostructured lipid carriers in beverage systems.

BACKGROUND: Nanostructured lipid carriers (NLCs) offer many potential benefits for incorporating lipophilic molecules into clear to opaque food systems. This study examined the stability of astaxanthin-loaded NLCs (Ax-NLCs) in model (solutions with 0 or 12% sucrose; pH 3, 7), semi-actual (whey) and actual (non-alcoholic beer) beverages during 30-60 days storage at 6 or 20 °C. RESULTS: Ax-NLCs (Z-average size: 94 nm), containing α-tocopherol and EDTA as antioxidants, were stabilised with Tween 80 and lecithin, and mixed with the aforementioned beverages at the volume ratio of 3:97. The presence of sucrose, improved the physical stability of Ax-NLCs in acidic model beverage. No astaxanthin loss and particle size growth were observed for Ax-NLCs-added whey. Carbonation and/or thermal pasteurisation of NLCs-added beer led to a major increase in its particles size and astaxanthin loss. Stability of Ax-NLCs in non-pasteurised CO2 -free beer improved at low storage temperature. The organoleptic quality of NLCs-added beers was still acceptable. CONCLUSION: These results indicate that NLCs containing hydrophobic nutraceuticals have potential to be used for functional beverages/foods development. © 2017 Society of Chemical Industry.

Stability of astaxanthin-loaded nanostructured lipid carriers as affected by pH, ionic strength, heat treatment, simulated gastric juice and freeze-thawing.

Nanostructured lipid carriers (NLCs) offer many potential benefits for incorporating lipophilic molecules into clear/opaque food systems. In this study, the influence of pH, ionic strength, thermal treatment, simulated gastric juice (SGJ), and freeze-thawing on the stability of astaxanthin-loaded NLCs (Ax-NLCs) was examined. Ax-NLCs (containing α-tocopherol and ethylenediaminetetraacetic acid as antioxidants) were stabilized with Tween 80 and lecithin (Z-average size: 94 nm), and studied for the above mentioned purpose. The size of Ax-NLCs increased at low pH values (≤5), high NaCl concentrations (≥50 mM), and slightly at SGJ, mainly because of decreasing the ζ-potential. Moreover, thermal treatment at 80/90 °C led to an increase in Ax-NLCs size. Glycerol was found as an appropriate cryoprotectant for preventing aggregation of Ax-NLCs during freeze-thawing. pH, ionic strength, heat and SGJ had no drastic effects on the chemical stability of astaxanthin in NLCs. These results have valuable implications for the utilization of food-grade NLCs.

Fabrication of whey proteins aggregates by controlled heat treatment and pH: Factors affecting aggregate size.

Protein aggregates can be formed by heating globular proteins above the thermal denaturation of the proteins. These aggregates can be used as delivery systems or to modulate the physicochemical and sensory properties of food products. In this study, the effects of heat treatment (15 min at 80 °C), pH adjustment (between 4 and 9), aging at different temperatures (between 10 and 60 °C) and the rate of acidification (pH decreased from 6.25 to 4 at 5 different rates) on whey proteins aggregates were studied. The results indicated that these treatments led to creation of aggregates with different sizes (0.72-5.1 µm). Heat treatment and reducing the pH down to nearly 4 led to an increase in the size of aggregates. At pH < 7, by increasing the aging temperature, the size of aggregates increased (without heat treatment). In the heat treated samples with pH < 9, increasing the aging temperature led to an increase in the size of aggregates. Also larger aggregates were formed by increasing acidification rate. The amount of insoluble whey proteins aggregates increased as a result of applying heat treatment, decreasing pH and increasing aging temperature. The results of this study can be used for fabrication of whey proteins aggregates with specific size and functionality.

Iron microencapsulation in gum tragacanth using solvent evaporation method.

In this study iron salt (FeSO4·7H2O) was microencapsulated in gum tragacanth hydrogel using solvent evaporation method. Three significant parameters (ferrous sulfate content, content of gum tragacanth, and alcohol to mixture ratio) were optimized by response surface methodology to obtain maximum encapsulation efficiency. Ferrous sulfate content, 5%, content of gum tragacanth, 22%, and alcohol to mixture ratio, 11:1 was determined to be the optimum condition to reach maximum encapsulation efficiency. Microstructure of iron microcapsules was thoroughly monitored using scanning electron microscopy (SEM). The microphotographs indicated two distinct crystalline and amorphous structures in the microcapsules. This structure was confirmed by X-ray diffraction (XRD) pattern of microcapsules. Fourier transform infrared (FTIR) spectra of iron microcapsules identified the presence of iron in the tragacanth microcapsules. The average size of microcapsules was determined by particle size analyzer. Release assessment of iron in simulated gastric fluid showed its complete release in stomach which is necessary for its absorption in duodenum. However, the use of encapsulated iron in gum tragacanth in watery foods is rather recommended due to the fast release of iron in water.

Reduction of acrylamide in whole-wheat bread by combining lactobacilli and yeast fermentation.

This study mainly focuses on a strategy for reducing acrylamide content in whole-wheat bread by combining lactobacilli and yeast in sourdough breadmaking. Combinations of sourdough (fermented dough using different Lactobacillus strains including Lactobacillus plantarum PTCC 1896 [probiotic], L. sakei DSM 20,017, L. rhamnosus DSM 20,021, and L. delbrueckii DSM 20,081) and yeast, in comparison with yeast alone, were used for breadmaking. The results showed that acrylamide levels in breads fermented using sourdough+yeast were in all cases much lower (6.9-20 µg/kg on a dry weight basis [d.b.]) than those in the yeast-only fermented bread (47.6 µg/kg d.b.). Significant (p < 0.05) correlations were also found between pH, total titratable acids (TTA) and lactic acid, and acrylamide content. Furthermore, the obtained results showed that the moisture content of dough directly influenced the formation of acrylamide in bread (r = 0.925, p < 0.0001). In addition, no significant correlations were observed between acrylamide content in breads and either the reducing sugar or free amino acid contents in dough samples. According to the different effects of Lactobacillus strains, it could be concluded that the acrylamide reducing potential of lactobacilli was strain-specific, with L. rhamnosus being the most effective. This suggests that sourdough fermentation with appropriate Lactobacillus strains can be used as an advantageous technology to reduce the acrylamide content of whole-wheat breads.

Thermomechanical and morphological properties of nanocomposite films from wheat gluten matrix and cellulose nanofibrils.

The aim of this investigation was the optimization of preparing gluten film containing cellulose nanofibrils (CNF). An optimization procedure using central composite design (CCD) with three factors (CNF, glycerol, and sodium dodecyl sulfate (SDS) concentrations) was used in order to investigate the effect of these parameters on the mechanical (tensile strength--TS, elongation at break--ε(b)) and thermal properties of gluten films and to establish a formulation to depict the relationship between the mentioned factors and mechanical properties. Through regression analysis, it was found that TS and ε(b) well fitted by quadratic polynomial equations (R² = 0.99 and 0.98, respectively) and the glycerol concentration was the most significant factor influencing them. The optimization was based on maximizing TS and ε(b). The optimum conditions determined using response surface methodology (RSM) were defined as: CNF concentration, 11.129 g/100 g, glycerol concentration, 35.440 g/100 g and SDS concentration, 6.259 g/100 g. The predicted responses for these film preparation conditions were a TS of 3.630 MPa and ε(b) of 86.033%. The verification experiments were conducted under optimal conditions to compare predicted and actual values of dependent variables. This experiment indicated that both predicted and actual values (TS of 3.721 MPa and ε(b) of 88.935%) almost coincide each other and therefore the estimated models were reasonable and of high accuracy to predict dependent variables values. The scanning electron microscopy (SEM) images showed non-agglomerated and well dispersed CNF in the gluten matrix. Differential scanning calorimetry (DSC) results indicated that there is not any significant difference (P > 0.05) between the glass transition temperature (T(g)) of optimum nanocomposite (-29.12 °C) and control film (-29.64 °C) and their thermogravimetric analysis (TGA) thermograms showed similar degradation behavior.

Effect of Consuming Zinc-fortified Bread on Serum Zinc and Iron Status of Zinc-deficient Women: A Double Blind, Randomized Clinical Trial.

After iron deficiency, zinc deficiency is the major micronutrient deficiency in developing countries, and staple food fortification is an effective strategy to prevent and improve it among at-risk-populations. No action has been taken to reduce zinc deficiency via flour fortification so far in Iran, and little is known about the influence of zinc fortification of flour on serum zinc and the iron status, and also about the optimum and effective amount of zinc compound that is used in food fortification. The objective of this study is to evaluate the influence of consuming zinc-fortified breads on the zinc and iron status in the blood serum. In this study, three types of bread were prepared from non-fortified and fortified flours, with 50 and 100 ppm elemental zinc in the form of sulfate. Eighty zinc-deficient women aged 19 to 49 years were randomly assigned to three groups; The volunteers received, daily, (1) a non-fortified bread, (2) a high-zinc bread, and (3) a low-zinc bread for one month. Serum zinc and iron were measured by Atomic Absorption before and after the study. Results showed a significant increase in serum zinc and iron levels in all groups (p < 0.001) except in the control (p > 0.05). Absorption of zinc and iron in the group that consumed high-zinc bread was significantly greater than that in the group that received low-zinc bread (p < 0.01). It was concluded that fortification of flour with 50-100 ppm zinc was an effective way to achieve adequate zinc intake and absorption in zinc-deficient people. It also appeared that consuming zinc-fortified bread improved iron absorption.