Bioflavours and fragrances via fermentation and biocatalysis

A condensed overview is given of the potential offered by bacteria, fungi and yeasts to produce a wide range of bioflavours and fragrances. A few commercialised processes are also discussed. The advantages of microbial processes versus chemical synthesis or extraction are outlined. Both de novo fermentation processes as well as bioconversions based on adding specific precursors/intermediates to microbial cells or enzymes are illustrated via typical examples. Bottlenecks, which currently hinder a wider introduction of this flavour biotechnology, are indicated and some solutions are proposed. © 2002 Society of Chemical Industry     

Supramolecular bionanocomposites 3: Effects of surface functionality on electrical and mechanical percolation

Percolation phenomena in bionanocomposites composed of the bioplastic polylactide and surface decorated supramolecular multiwalled carbon nanotubes (MWCNTs) are investigated. MWCNTs with three distinct surface chemistries—a native surface, a hydroxyl functionalized surface, and a short hydrocarbon functionalized surface—are prepared and studied. Two experimental methods are used to determine percolation thresholds; melt rheology provides a measure of the mechanical percolation threshold and electrical impedance spectroscopy provides values of the electrical percolation threshold. The MWCNT‐loading level required to obtain mechanical percolation is systematically found to be lower than the loading level needed to achieve electrical percolation. Hydroxylated MWCNTs have the highest percolation thresholds of 1.8 (mechanical) and 6.7 wt % (electrical), which is attributed to aggregation caused by hydrogen bonding. Alkane‐grafted MWCNTs have lower percolation thresholds of 0.76 (mechanical) and 2.8 wt % (electrical). However, untreated MWCNTs have the lowest thresholds of 0.16 (mechanical) and 1.5 wt % (electrical). The reduced percolation threshold observed upon conversion of the hydroxylated surface to the alkylated surface is attributed to morphological differences—functionalization disrupts hydrogen bonding and leads to better nanotube dispersion. The combination of higher inherent conductivity and more favorable nanotube‐polylactide interactions implies that unmodified MWCNTs are preferred to produce electrically conductive bionanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Retention of Provitamin A Carotenoids in Staple Crops Targeted for Biofortification in Africa: Cassava,Maize and Sweet Potato

HarvestPlus, part of the Consultative Group on Internation Agriculture research (CGIAR) Program on Agriculture for Nutrition and Health (A4NH) uses conventional plant breeding techniques to develop staple food crops that are rich in micronutrients, a food-based approach to reduce micronutrient malnutrition known as biofortification. The nutritional breeding targets are established based on the food intake of target populations, nutrient losses during storage and processing and bioavailability. This review collates the evidence on the retention of provitamin A carotenoid (pVAC) after processing, cooking, and storing of the staple crops targeted for pVAC biofortification: cassava, maize, and sweet potato. Sun drying was more detrimental to the pVAC levels (27–56% retention) in cassava than shade (59%) or oven (55–91%) drying, while the pVAC retention levels (66–96%) in sweet potato were not significantly different among the various drying methods. Overall, boiling and steaming had higher pVAC retention (80–98%) compared to baking (30–70%) and frying (18–54%). Gari, the most frequently consumed form of cassava in West Africa had the lowest pVAC retention (10–30%). The pVAC retention of maize grain and cassava and sweet potato flour reached levels as low as 20% after 1–4 months of storage and was highly dependent on genotype. Therefore, we recommend that an evaluation of the pVAC degradation rate among different genotypes be performed before a high pVAC crop is promoted.     

Bioactive peptides from nuts: A review

Oxidative stress occurs because of an imbalance in the production of reactive oxygen species. Nuts are rich in bioactive compounds, including phenolic compounds, tannins, and phytosterols. Although nuts are widely consumed because of their beneficial effects on nutrition and health, there is limited information about bioactive peptides from nuts. Pine nut and walnut-derived peptides are the most studied because these nuts contain a higher amount of protein. Different biological activities have been demonstrated for nut peptides; many of them exhibit antioxidant, anticancer, antihypertensive, antidiabetic, immunomodulatory, antiseizure, or neuroprotective activity. Recent studies have focused on increasing the bioactivity of identified bioactive peptides by applying new technologies and chemosynthetic strategies. Research tendency points to the generation of peptides with specific sequences for application in specific diseases. Nut bioactive peptides can become key functional ingredients for food, pharmaceuticals, or cosmetics.     

Effect of dielectric microwave heating on the color and antiradical capacity of betanin

The decomposition of betanin under dielectric heating (microwave irradiation, power: 25–200 W (3–24 kJ g⁻¹)) follows first-order kinetics with a rate constant similar to that obtained during conventional conduction heating (half-life < 2 min at 100 °C). Color coordinate analysis indicates that betanin is bleached upon thermal treatment, whereas beetroot juice and spray-dried beetroot powder tend to form colored decomposition products. The antiradical capacity of betanin decreases upon heating, but is still much higher than that of standard antioxidants such as ascorbic acid and trolox. Betalamic acid, a high capacity antiradical, was detected by mass spectrometry and second-derivative absorption spectroscopy in betanin samples submitted to thermal treatment.     

Alginate/cashew gum floating bead as a matrix for larvicide release

A polymeric floating system composed of Alginate (ALG) and Cashew gum (CG), loaded with an essential oil (Lippia sidoides–Ls) was prepared by ionotropic gelation, characterized regarding its physical-chemistry properties and evaluated on its potential as a controlled release system. The influence of process parameters on the buoyancy, loading, swelling and in vitro and in vivo release kinetics, was investigated. Results showed that beads produced with carbonate and Ls at high level contents exhibit good floatability (up to 5 days) and loading capacity (15.2–23.8%). In vitro release data showed a Fickian diffusion profile and in vivo experiments showed that ALG–CG floating system presented a superior and prolonged larvicide effect, in comparison with non-floating ones, presenting larvae mortality values of 85% and 33%, respectively, after 48 h. These results indicate that ALG–CG floating beads loaded with Ls presented enhanced oil entrapment efficiency, excellent floating ability, and suitable larvicide release pattern.     

Plasma spraying using Ar-He-H2 gas mixtures

In plasma spraying, the properties of the plasma-forming gas largely control the characteristics of the plasma jet and the momentum, heat, and mass transfers to the particles injected in the flow. The objective of this work was to investigate the effect of gas composition on the static and dynamic behaviors of the plasma jet. The latter behaviors were investigated from measurements of arc voltage and plasma jet velocity. Ternary gas mixtures of argon, helium, and hydrogen were used. The results were expressed as correlations between arc voltage and flow velocity, and the operating parameters of the gun for a specific nozzle diameter.