Study on Maillard-reaction driven transformations and increase of antioxidant activity in lysine fortified biscuits

Phenolic acid content and in vitro antioxidant capacity of einkorn water biscuits as affected by baking time

Aim of this research was to study the evolution of heat damage, phenolic acid content and in vitro antioxidant capacity of whole meal einkorn water biscuits baked at 205 °C for increasing times (10 min steps) from 25 to 75 min. The heat damage was gauged by determining furosine, hydroxymethylfurfural (HMF), furfural and glucosylisomaltol (GLI) contents. Furosine increased up to 50 min baking, when HMF started to form; furfural augmented only after 65 min treatment, whereas GLI did not change. An unknown compound, apparently related to the severity of the heat load, aroses through the aldolic condensation of HMF with the acetone used for the extraction of phenolic acids; hence the use of acetone-based solvents in thermally processed cereal products should be avoided. The conjugated phenolic acids ferulic, vanillic, syringic, p-coumaric, p-hydroxybenzoic and syringaldehyde and the bound phenolic acids ferulic, p-coumaric, syringic, and p-hydroxybenzoic were identified in water biscuits. The stronger heating treatments led to an increase of the soluble conjugated compounds, but did not influence the bound fraction. The in vitro antioxidant capacity of water biscuits augmented significantly as baking time increased, likely for the formation of antioxidant compounds as a consequence of heat damage.

Speciation and transformation of nitrogen for spirulina hydrothermal carbonization

Nitrogen conversion (N-conversion) mechanism of spirulina (SP) in hydrothermal carbonization (HTC) was investigated under medium-low temperature (180-280 °C). N-conversion in bio-char, liquid and bio-oil were studied by FTIR, XPS, GC-MS and other analytical methods. Results indicated that the temperature could significantly affect the evolution of nitrogen. At 180-200 °C, the content of protein-N and pyridine-N in bio-char fell 23.01% and 9.51% respectively. In contrast, the contents of inorganic-N and quaternary-N increased by 16.99% and 16% respectively. Protein-N hydrolysis and Maillard reaction produced the key intermediate compounds, including amines, amides and N-heterocyclic compounds during the HTC. At 200-280 °C, the inorganic-N was obviously converted from solid to liquid. With the increased of temperature, it would enhance the polymerization of pyrrole-N and pyridine-N, which could cause the significant increase of aromatic N-heterocyclic compounds (e.g., nitriles and indole derivatives) in bio-oil. A N-conversion mechanism of SP HTC was proposed in this study.

Antioxidant Activity In Vitro of N-(1-deoxy-α-d-xylulos-1-yl)-Phenylalanine: Comparison Among Maillard Reaction Intermediate, End-Products and Xylose-Phenylalanine

The Maillard reaction end-products (MRPs) and intermediate (MRI, N-(1-deoxy-α-D-xylulos-1-yl)-phenylalanine) derived from xylose (Xyl) and phenylalanine (Phe) model system were synthesized in an aqueous medium, and their antioxidant activity was evaluated. Both the MRPs and N-(1-deoxy-α-d-xylulos-1-yl)-phenylalanine exhibited the Fe²⁺ chelating activity at their addition concentration of 2 to 12 mg/mL. While their reducing power, free radical scavenging activity, and inhibition effect on lipid peroxidation were observed at a lower addition concentration of only 0.2 to 1.2 mg/mL. The free radical scavenging activity was improved with the increase in their concentration, and a time-dependent scavenging effect of the MRI was also shown in the results. However, a weak chelating activity of Xyl-Phe on Fe²⁺ in a concentration-dependent manner was observed, but no significant free radical scavenging activity or reducing power of Xyl-Phe was found. Based on these results, possible free radical scavenging pathway of the MRI was proposed. As the MRI showed lower antioxidant activity than MRPs, the application of the MRI in combination with MRPs as an antioxidant was proposed in cooked or semi-processed foods to avoid the deterioration induced by oxidation. PRACTICAL APPLICATION: The Maillard reaction intermediates (MRIs) showed antioxidant activity and could be applied in foods as both antioxidants and flavor enhancer. The MRIs will probably extend the shelf-life of lipid rich foods and could be the substitute of artificial antioxidants.

Antioxidative, Antibacterial, and Food Functional Properties of the Half-Fin Anchovy Hydrolysates-Glucose Conjugates Formed via Maillard Reaction

The antioxidative, antibacterial, and food functional properties of the half-fin anchovy hydrolysates (HAHp)-glucose conjugates formed by Maillard reaction (MR) were investigated, respectively. Results of sugar and amino acid contents loss rates, browning index, and molecular weight distribution indicated that the initial pH of HAHp played an important role in the process of MR between HAHp and glucose. HAHp-glucose Maillard reaction products (HAHp-G MRPs) demonstrated enhanced antioxidative activities of reducing power and scavenging DPPH radicals compared to control groups. HAHp-G MRPs produced from the condition of pH 9.6 displayed the strongest reducing power. The excellent scavenging activity on DPPH radicals was found for HAHp(5.6)-G MRPs which was produced at pH 5.6. Additionally, HAHp(5.6)-G MRPs showed variable antibacterial activities against Escherichia coli, Pseudomonas fluorescens, Proteus vulgaris, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Bacillus megaterium, and Sarcina lutea, with the MIC values ranging from 8.3 to 16.7 μg/mL. Result of scanning electron microscopy (SEM) on E. coli suggested that HAHp(5.6)-G MRPs exhibited antibacterial activity by destroying the cell integrity through membrane permeabilization. Moreover, HAHp(5.6)-G MRPs had excellent foaming ability and stability at alkaline conditions of pH 8.0, and showed emulsion properties at acidic pH 4.0. These results suggested that specific HAHp-G MRPs should be promising functional ingredients used in foods.

Effect of selected spices on chemical and sensory markers in fortified rye-buckwheat cakes

The aim of this study was to find out the effect of selected spices on chemical and sensorial markers in cakes formulated on rye and light buckwheat flour fortified with spices. Among collection of spices, rye-buckwheat cakes fortified individually with cloves, nutmeg, allspice, cinnamon, vanilla, and spice mix revealed the highest sensory characteristics and overall quality. Cakes fortified with cloves, allspice, and spice mix showed the highest antioxidant capacity, total phenolics, rutin, and almost threefold higher available lysine contents. The reduced furosine content as well as free and total fluorescent intermediatory compounds were observed as compared to nonfortified cakes. The FAST index was significantly lowered in all cakes enriched with spices, especially with cloves, allspice, and mix. In contrast, browning index increased in compare to cakes without spices. It can be suggested that clove, allspice, vanilla, and spice mix should be used for production of safety and good quality cakes.

Influence of water biscuit processing and kernel puffing on the phenolic acid content and the antioxidant activity of einkorn and bread wheat

The whole meal flour of wheat is rich in phenolic acids, which provide a relevant antioxidant activity to food products. Aim of this research was to assess the influence of processing on phenolic acid content and antioxidant activity of whole meal flour water biscuits and puffed kernels of einkorn and bread wheat. To this end, the evolution of syringaldehyde, ferulic, vanillic, syringic, p-coumaric, p-hydroxybenzoic, and caffeic acids was studied during manufacturing. Overall, from flour to water biscuit, the total soluble conjugated phenolic acids increased slightly in einkorn, while the insoluble bound phenolic acids decreased in all the accessions as a consequence of losses during the mixing step. In the puffed kernels, instead, the total soluble conjugated phenolic acids increased markedly, while the bound phenolics did not show any clear change, evidencing their high thermal stability. The antioxidant activity, measured by FRAP and ABTS, increased during processing and was highest under the most drastic puffing conditions.

N-Doped biochar derived from co-hydrothermal carbonization of rice husk and Chlorella pyrenoidosa for enhancing copper ion adsorption

Biochar derived from rice husk was modified by microalgae Chlorella pyrenoidosa as a natural nitrogen-rich precursor in a hydrothermal environment for copper ion (Cu(ii)) adsorption.

Characterization of aqueous phase from the hydrothermal liquefaction of Chlorella pyrenoidosa

This study investigated the characteristics of aqueous phase from hydrothermal liquefaction of low-lipid microalgae Chlorella pyrenoidosa. The interactions of operating conditions, including reaction temperature, retention time and total solid ratio were evaluated by response surface methodology. The chemical oxygen demand, total nitrogen and total phosphorus were selected as indicators of the property of AP. Results indicated that total solid ratio was found to be the dominant factor affecting the nutrient recovery efficiencies of AP. Based on energy recovery, GC-MS indicated that the AP at two optimized operating conditions (280 °C, 60 min, 35 wt.% and 300 °C, 60 min, 25 wt.%) were observed to have a higher concentration of organic acids (10.35% and 8.34%) while the sample (260 °C, 30 min, 35 wt.%) was observed to have the highest concentration of N&O-heterocyclic compounds (36.16%).

Study on Sensory Quality, Antioxidant Properties, and Maillard Reaction Products Formation in Rye-Buckwheat Cakes Enhanced with Selected Spices

The effect of selected spices included in the recipe of rye-buckwheat cakes on sensory quality, nutritional value, and Maillard reaction (MR) products formation was addressed in this study. The cakes with cloves, nutmeg, allspice, cinnamon, vanilla, and spice mix addition revealed the highest overall quality values. Cakes enriched with cloves, allspice, and spice mix showed the highest rutin content and almost threefold higher available lysine contents whereas cakes enhanced with mix, cloves, and cinnamon were the richest source of phenolic compounds. The highest antioxidant capacity showed cakes with cloves and spice mix. The furosine, a marker of early stage of MR, was decreased in cakes with cloves, allspice, spice mix, and vanilla whereas fluorescent intermediatory compounds were reduced in cakes enhanced with cloves, allspice, and cinnamon. In contrast, browning index was increased as compared to cakes without spices. The FAST index was significantly lowered in all cakes enriched with spices, especially with cloves, allspice, and mix addition. The presence of cloves, allspice, and vanilla in cake formula was the most efficient in acrylamide strategy. It can be suggested that cloves, allspice, and vanilla might be used for production of safety and good quality cakes.