Formation Of Browning Products Research Articles

Effects of reaction parameters on self-degradation of L-ascorbic acid and self-degradation kinetics.

The degradation behavior of L-ascorbic acid (ASA) was investigated under different parameters of temperature, time, and pH. Higher temperatures and longer times accelerated the ASA degradation. Degradation product distributions changed with different pH values. As solution pH of 4.5 was beneficial for formation of uncolored intermediate products with an absorbance maximum at 294 nm. Formation of brown products was promoted at pH values from 5.8 to 6.8 with an absorbance maximum at 420 nm. Under different pH conditions, volatile products formation varied. Furfural and derivatives of furan were primary products due to the effects of pH. The non-enzymatic selfdegradation behavior of ASA was characteristic of first-order kinetics based on a classic dynamic model. Activation energy values varied under different pH values. An ASA degradation mechanism and pathway are proposed.

Antioxidant and protective effects of black Punica granatum extract on AGEs and UV‐A‐induced damaged human fibroblast (647.28)

One of causes of skin wrinkles may be the nonenzymatic glycation followed formation of browning products called advanced glycation endproducts (AGEs), an irreversible cross‐linked protein. The accumulation of glycated collagen cross‐linked in skin inhibits the formation and function of skin tightening agents such as collagen. Also, the UV effects on AGEs generates reactive oxygen species (ROS) in the extracellular matrix which could lead to additional deleterious effects on skin. Antioxidant, glycation inhibitory activities and anti‐skin aging of Punica granatum were have been founded and it is known that ellagic acid (EA), major compound of Punica granatum, has antioxidant effect. This study analyzed the functional components, antioxidant activities and anti‐skin aging of black Punica granatum extracts (BPE). Previous study reported that significant correlations were found between the red intensity, antioxidant capacity and total phenolic content. And we confirmed that BPE had more antioxidant activity, total polyphenol, total flavonoid and ellagic acid content than Punica granatum. Moreover, we studied photoprotective effect of BPE that attenuated the AGEs and UV‐A‐induced toxicity of human fibroblast. Also, this study examined potent activities of BPE on type 1 collagen synthesis and elastase inhibitory activity. In conclusion, we demonstrated the beneficial effects of black Punica granatum on anti‐wrinkle and the improving effect on damaged skin induced by AGEs and UV‐A.

Microwave superheated water and dilute alkali extraction of brewers’ spent grain arabinoxylans and arabinoxylo-oligosaccharides

Microwave superheated water extractions (MWE) were performed to evaluate the feasibility of this technology for quantitative recovery of the arabinoxylans (AX) or arabinoxylo-oligosaccharides (AXOS) from brewers’ spent grain (BSG). The AX+AXOS yield increased with the increase of the temperature in the range from 140 to 210°C during 2min. The higher temperatures promoted depolymerisation, debranching, and deesterification of the polysaccharides, with formation of brown products. The conditions that promote a compromise between the yield and the structure obtained, minimizing the thermal degradation of the fractions extracted by MWE are the following: (1) 140°C, to remove the residual starch mixed with β-glucans; (2) Suspension of the residue left in water and treated at 180°C; (3) suspension of the residue in 0.1M KOH and treated at 180°C. Using this sequential procedure, it was possible to extract 62% of BSG AX+AXOS, presenting degrees of polymerization ranging between 7 and 24 xylose residues, and a degree of phenolic acids esterification between 5 and 21%. The structural variability obtained by MWE allows defining specific types of compounds for different applications and uses depending on the extraction conditions used.

Influence of air-drying temperature on drying kinetics, colour, firmness and biochemical characteristics of Atlantic salmon (Salmo salar L.) fillets

In this work the drying kinetics of Atlantic salmon (Salmo salar L.) fillets and the influence of air drying temperature on colour, firmness and biochemical characteristics were studied. Experiments were conducted at 40, 50 and 60°C. Effective moisture diffusivity increased with temperature from 1.08×10−10 to 1.90×10−10m2s−1. The colour difference, determined as ΔE values (from 9.3 to 19.3), as well as firmness (from 25 to 75Nmm−1) of dried samples increased with dehydration temperature. The lightness value L∗ and yellowness value b∗ indicated formation of browning products at higher drying temperatures, while redness value a∗ showed dependence on astaxanthin value. Compared with fresh fish samples, palmitic acid and tocopherol content decreased in a 20% and 40%, respectively, with temperature. While eicosapentaenoic acid (EPA) content remained unchanged and docosahexaenoic acid (DHA) content changed slightly. Anisidine and thiobarbituric acid values indicated the formation of secondary lipid oxidation products, which is more relevant for longer drying time than for higher drying temperatures.

Two Types of Radicals in Whole Milk Powder. Effect of Lactose Crystallization, Lipid Oxidation, and Browning Reactions

Whole milk powder was stored in closed vials at 60 degrees C to induce crystallization of lactose within a short time scale. After an induction period of 3-4 days simultaneous crystallization of lactose, increase of water activity, formation of browning products, and increase of radical content took place. Radicals detected before lactose crystallization were characterized by a narrow ESR spectrum (g = 2.006) and could be depleted by removal of oxygen and therefore were assigned to oxidation processes. Late-stage radicals present after crystallization of lactose gave much wider spectra (g = 2.0048) and were independent of oxygen availability and assigned to late-stage Maillard reaction products. The study indicates that the processes of lactose crystallization, browning, and formation of radical species (g = 2.0048) are strongly coupled, while lipid oxidation is less dependent on the other processes.

Nonenzymatic browning reactions of retro-aldol degradation products of carbohydrates

Methylglyoxal and glyceraldehyde were used to demonstrate the involvement of retro-aldol degradation products of carbohydrates in browning (A420), the formation of hydroxymethylfurfural (HMF), and the extent to which the mechanism of browning proceeds by homolytic or heterolytic pathways in the caramelization and Maillard reactions of mono- and disaccharides. The amino component of Maillard systems is required for the retro-aldol cleavage of D-glucose. The short-chain α-dicarbonyl compounds so formed appear to dominate not only the formation of brown products but also the mechanism of the browning of D-glucose under these conditions, even if only small amounts are formed. Evidence is presented to link the formation of free radicals in the browning of glucose to reactions of the retro-aldol products. A novel reaction pathway is suggested for the formation of HMF from glyceraldehyde.

In vitro non-enzymatic glycation and formation of browning products in the bovine lens α-crystallin

Calf lens LMW α-crystallin was glycated by incubating with various sugars (glucose, glucose-6-P and ribose) for 21 days. All sugars induced disulfide formation, but ribose also produced higher molecular weight cross-linked species. The ribocated protein turned yellow in color and had a strong blue fluorescence ( Ex Em = 370 450 nm ) typical for a browning product. The chromophore of the browning product showed a new circular dichroism (CD) band at 320–330 nm. Conformational study indicated that the browning reaction destabilized protein and may play a significant role in protein aggregation and insolubilization.

Untersuchungen zur Maillard-reaktion 18. Mitteilung. radikalische inhibierung der br�unung durch schwefelverbindungen

ESR spectroscopic investigations on the mechanism of Maillard-reactions using the model D-glucose/glycine show radical formation in some of the reaction steps. These are possibly due to competitive reactions against ionic mechanism. The formation of radicals depends on the concentration of reactants and reaches a maximum in thermically induced browning reactions. The addition of L-cysteine leads to a decrease in the radical concentration to about 60%. It can be indirectly proven that the radicals are involved in the formation of browning products. The hyperfine structures of ESR spectra are supposed to be similar to pyrazine cation radicals.