Effect of the phenol antioxidant type on the kinetics and mechanism of inhibited lipid oxidation in the presence of fatty alcohols

A kinetic analysis of inhibited lipid autoxidation in the presence of a phenol antioxidant and a hydroxy compound is proposed. It is based on studies of the dependence of the W^ROH/W_inh ratio (between the inhibited oxidation rates in presence and absence of a hydroxy compound) on the hydroxy compound concentration. This analysis permits establishing the mechanism of action of the hydroxy compound in the presence of different types of phenol antioxidants during inhibited lipid oxidation. The kinetic analysis has been applied to the oxidation at 80°C of triacylglycerols of sunflower oil (TGSO) inhibited by 0.1 mM hydroquinone, butylated hydroxytoluene (BHT) or α-tocopherol in the presence of different concentrations of 1-tetradecanol (1-TD) and 1-octadecanol (1-OD). A linear character of this dependence is established during hydroquinone-inhibited oxidation of triacylglycerols of sunflower oil in presence of 1-TD. In the case of α-tocopherol this dependence is linear for both 1-TD and 1-OD. The equilibrium constant of interaction between the phenol antioxidant and the fatty alcohols is determined by the angle coefficient of the linear dependence. The hydroquinone-inhibited autoxidation of TGSO in the presence of 1-OD has shown a non-linear character of the dependence under consideration. A kinetic model describing simultaneous participation of 1-OD in reaction with both the phenol antioxidant and the lipid hydroperoxides is deduced. Studying the kinetics of BHT-inhibited autoxidation of TGSO in the presence of 1-OD, it has been shown that due to steric reasons there is no interaction between 1-OD and BHT, 1-OD participating in the process only by accelerating the decomposition of the lipid hydroperoxides.     

Multiple Exothermic Oxidation Behaviour of Polyethylene

The change of shape patterns of the oxidation peak on differential thermal analysis curves of a series of formulations of polyethylene has been investigated. The unstabilised sample exhibits two oxidation peaks. When a chain-terminating antioxidant and dilaurylthiodipropionate were added to polyethylene, it was found that as the concentration of dilaurylthiodipropionate increases, the second oxidation peak reduces in size. In many instances when the amount of dilaurylthiodipropionate reaches 0.3% (by weight), the second oxidation peak disappears. The influences of processing method and outdoor exposure on the peak shape have also been examined. The effectiveness and consumption of antioxidants during weathering is clearly shown by the shape change of the oxidation peak on the differential thermal analysis curves.     

恒温超声辅助提取诃子FRAP类抗氧化活性物质的研究

为了探索恒温超声辅助提取诃子FRAP类抗氧化活性物质提取效果,本文采用该技术首先对提取工艺进行优化,进而通过比较实验和扫描电镜分析该技术提取高效的原因。结果表明,诃子FRAP类抗氧化活性物质恒温超声辅助提取最佳工艺条件为:采用60%乙醇、超声功率180 W、超声频率80 k Hz、超声温度70℃;比较分析发现,该工艺提取效率显著高于水浴振荡提取工艺(p<0.001);扫描电镜分析发现,恒温超声辅助提取对诃子原料细胞结构破坏更严重,从而增强了提取效率。恒温超声辅助提取技术对诃子抗氧化活性物质提取效率高,本文可为诃子产业化开发提供依据。      

Antioxidant and Anti-diabetic Properties of Caryota Urens (Kithul) Flour

Starch extracted from pith of Caryota urens L. (Family: Arecaceae) palm is known as “Kithul flour” and is claimed to have health benefits according to folklore and Ayurveda. Antioxidants are believed to possess numerous health benefits. However, as yet, health benefits of C. urens flour have not been scientifically investigated. Antioxidant properties of C. urens flour were tested using different in vitro assays namely, 2,2-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS⁺), ferric reducing antioxidant power, oxygen radical absorbance capacity and ferrous ion chelating assays. Total Phenolic Content (TPC) and Total Flavonoid Content (TFC) were also evaluated. Anti-diabetic properties were estimated using alpha amylase and alpha glucosidase enzyme inhibition assays. Dried methanolic extracts of both boiled and raw samples were used in all assays. Results of the study showed that C. urens flour possess free radical scavenging activity(raw 0.02± 0.01 and boiled 0.04±0.01 mg trolox equivalent (TE)/ g flour), electron donating reducing power (raw 0.10±0.03 and boiled 0.36±0.11 mg TE/g flour), oxygen radical absorbance capacity (raw 2.29± 0.71 and boiled 192.3 ± 57.71 mg TE/1 g flour) and metal ion chelating capacity (raw 0.03±0.01 and boiled 0.14±0.04 mg EDTA equivalents /g flour) exhibiting its antioxidant potential. TPC (raw 1.1±0.3 and boiled 5.12 ± 1.89 mg GAE/g flour) and TFC (raw 1.65 ± 0.47 and boiled 6.69 ± 1.27 μg QE/g flour) which are said to be contributed to antioxidant activities were also found. In addition, boiled flour which is generally consumed as a food has shown higher antioxidant activity. Caryota urens flour did not contain marked anti-diabetic properties. It is evident from results that Caryota urens flour has moderate antioxidant property which may associate with its traditional health claims.     

Oxidative and microbial stability of poultry meatballs added with coriander extracts and packed in cold modified atmosphere

The aim of the study was to determine the effects of adding of coriander extracts to turkey meatballs. Meat samples were stored in modified atmosphere at 4°C ± 1°C for 9 days. The addition of coriander extract at 500 ppm level delayed the process of lipid oxidation for the period of 6 days of storage and growth inhibition of aerobic microorganisms for the period of 9 days of storage. The usage of a dose of 500 ppm as well as a dose of 200 ppm had no significant effect on the sensory features, but had an impact on colour parameters of the meatballs. In the groups with coriander extract, volatile terpenes were identified.     

A comprehensive review on polarity,partitioning, and interactions of phenolic antioxidants at oil–water interface of food emulsions

There has been a growing interest in developing effective strategies to inhibit lipid oxidation in emulsified food products by utilization of natural phenolic antioxidants owing to their growing popularity over the past decades. However, due to the complexity of emulsified systems, the inhibition mechanism of phenolic antioxidants against lipid oxidation is rather complicated and not yet fully understood. In order to highlight the importance of polarity of phenolic antioxidants in emulsified systems according to the polar paradox, this review covers the recent progress on chemical, enzymatic, and chemoenzymatic lipophilization techniques used to modify the polarity of antioxidants. The partitioning behavior of phenolic antioxidants at the oil–water interface, which can be influenced by the presence of synthetic surfactants and/or antioxidant emulsifiers (e.g., polysaccharides, proteins, and phospholipids), is discussed. In addition, the emerging phenolic antioxidants among phenolic acids, flavonoids, tocopherols, and stilbenes applied in food emulsions are elaborated. As well, the interactions of polar–nonpolar antioxidants are stressed as a promising strategy to induce synergistic interactions at oil–water interface for improved oxidative stability of emulsions.     

Acrylamide formation and antioxidant level in biscuits related to recipe and baking

Heated plant foods may contain compounds with adverse health effects (e.g. acrylamide). On the other hand, health-promoting compounds (e.g. antioxidants) have also been identified in such foods. Therefore, a baking experiment with biscuits was carried out to study the potential impact of both acrylamide and antioxidants in that food. Two different wheat flour types – wholemeal (WMF) and white flour type 550 (T550; 0.55% mineral content) – as well as recipe (fat and leavening agent) and thermal input (temperature?×?time) were changed. Furthermore, the effect of an enzymatic asparagine hydrolysation was tested. Antioxidants were determined with two independent procedures ABTS – (2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate)) and FRAP-assay (ferric reducing ability of plasma). WMF samples resulted in an unchanged acrylamide level, but in a significantly higher antioxidant concentration when compared with T550 samples (149 and 141?µg?kg^?1 acrylamide and 9.1 and 5.1?mmol?TE?kg^?1 FW ABTS for WMF and T550, respectively). A reduced fat content yielded in an increased volume. Raising agents had no effect on acrylamide levels, but antioxidants were higher in samples with sodium bicarbonate (SBC) than with ammonium bicarbonate (ABC). Thermal input (temperature?×?time; 150°C?×?25?min to 240°C?×?9?min) indicated an exponential acrylamide increase especially at higher temperatures (from 75 to 236?µg?kg^?1), whereas antioxidant increase was linear (from 7.0 to 7.7?mmol?TE?kg^?1 FW, ABTS). FRAP and ABTS values were correlated on a low level, whereas acrylamide content of biscuits was correlated with FRAP and lightness (R ^2?=?0.62 and 0.47, and 0.71 and 0.85 for WMF and T550, respectively). The enzyme asparaginase reduced acrylamide formation by about 50% for both raising agents (SBC and ABC, respectively), whereas antioxidant levels were not affected. An evaluation of recipe variants with low acrylamide and high antioxidants indicated the advantage of wholemeal biscuits.     

天然抗氧化剂对玉米油稳定性的影响

分别将生育酚、β-胡萝卜素和迷迭香提取物天然抗氧化剂添加到纯化后的玉米油中,采用schaal烘箱加速氧化法,对比纯化玉米油,研究天然抗氧化剂对玉米油稳定性的影响,建立氧化反应动力学方程。结果表明,3?种抗氧化剂抗氧化能力为迷迭香提取物＞β-胡萝卜素＞生育酚。当每100 g玉米油添加天然抗氧化剂0.02?g时,玉米油添加生育酚、β-胡萝卜素和迷迭香提取物后的动力学模型分别为、和,而纯化玉米油的动力学模型为,并推测出纯化玉米油与添加过3?种天然抗氧化剂后,一级玉米油的货架期分别为15、19、24、27?个月。所以以迷迭香提取物为抗氧化剂添加到玉米油中,可明显提高玉米油的货架期。