The chemical diversity of natural antioxidants (AOXs) makes it difficult to
separate, detect, and quantify individual antioxidants from a complex
food/biological matrix. Moreover, the total ...antioxidant power is often more
meaningful to evaluate health beneficial effects because of the cooperative
action of individual antioxidant species. Currently, there is no single
antioxidant assay for food labeling because of the lack of standard
quantification methods. Antioxidant assays may be broadly classified as the
electron transfer (ET)- and hydrogen atom transfer (HAT)-based assays. The
results obtained are hardly comparable because of the different mechanisms,
redox potentials, pH and solvent dependencies, etc. of various assays. This
project will aid the identification and quantification of properties and mutual
effects of antioxidants, bring a more rational basis to the classification of
antioxidant assays with their constraints and challenges, and make the results
more comparable and understandable. In this regard, the task group members
convey their own experiences in various methods of antioxidants measurement.
Antioxidants are among the most studied topics both in the area of food science and nutrition. Antioxidants were firstly used as just a food preservative, then it was realized that they inhibited the ...oxidation processes not only in foods but also in human metabolism. Then, they gained the spotlight with their important roles both in foods and in human body. Consequently, significant number of research articles focusing on the antioxidant content of different foods, analytical methods for better estimation and measurement of the antioxidant capacity of foods have been publishing for years. In addition, there is a growing interest among the food scientists in improving the knowledge on the physiological effects of antioxidants in the human body. This review provides a historical overview about antioxidants covering their occurrence and roles in various foods, analytical methods for the determination of their antioxidant capacity, and their physiological effects.
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•Antioxidants are among the most studied topics in food science.•Antioxidants provide health benefits beyond preservative effects in food.•Several antioxidant compounds have been discovered from natural sources.•In vitro and in vivo assays have been developed to determine antioxidant capacity.•Understanding metabolism and digestion behavior of antioxidants gained spotlight.
Oxygen radical antioxidant capacity (ORAC) and trolox equivalent antioxidant capacity (TEAC) assays were compared to estimate the total antioxidant capacity (TAC) of orange juice, milk, and an orange ...juice-milk beverage. When the TEAC method was used with this beverage, an increase in the concentration of orange juice corresponded to an increase in TAC, but increasing the percentage of milk did not increase the TAC value. When the ORAC method was applied, it was seen that increased concentrations of juice or milk corresponded to greater antioxidant capacity. An evaluation was also made of the influence of certain compounds (ascorbic acid, gallic acid, β-carotene, lutein, zeaxanthin and albumin) with antioxidant capacity that were present in the samples studied.
Although the TEAC method is simpler and cheaper than the ORAC method, it gives an underestimate of the antioxidant capacity of foods or beverages of a more complex nature.
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•Microencapsulated polyphenols from jabuticaba bark were added to dairy drinks.•Bioactive-rich powders contributed to color and functional potential of dairy drinks.•Bioactive powders ...added to dairy drinks present good stability during storage.•Carrier agents influence differently the glycemic response in dairy drinks.•Dairy drinks with Gum arabic powders and extracts reduced postprandial glucose.
This work incorporated bioactives extracted from jabuticaba peel in the form of concentrated extract (JBE) and microencapsulated powders with maltodextrin (MDP) and gum arabic (GAP) in a dairy drink, evaluating its stability, in vitro bioaccessibility, and glycemic response. We evaluated the pH, acidity, colorimetry, total phenolics and anthocyanins, antioxidant capacity, degradation kinetics and half-life of anthocyanins, bioaccessibility, and postprandial glycemic physicochemical characteristics response in healthy individuals. The drinks incorporated with polyphenols (JBE, GAP, and MDP) and the control dairy drink (CDD) maintained stable pH and acidity over 28 days. In color, the parameter a*, the most relevant to the study, was reduced for all formulations due to degradation of anthocyanins. Phenolic and antioxidant content remained constant. In bioaccessibility, we found that after the gastrointestinal simulation, there was a decrease in phenolics and anthocyanins in all formulations. In the glycemic response, we observed that the smallest incremental areas of glucose were obtained for GAP and JBE compared to CDD, demonstrating that polyphenols reduced glucose absorption. Then, the bioactives from jabuticaba peel, incorporated into a dairy drink, showed good storage stability and improved the product’s functional aspects.
It would be desirable to establish and standardize methods that can measure the total antioxidant capacity level directly from vegetable extracts containing phenolics. Antioxidant capacity assays may ...be broadly classified as electron transfer (ET)- and hydrogen atom transfer (HAT)-based assays. The majority of HAT assays are kinetics-based, and involve a competitive reaction scheme in which antioxidant and substrate compete for peroxyl radicals thermally generated through the decomposition of azo compounds. ET-based assays measure the capacity of an antioxidant in the reduction of an oxidant, which changes colour when reduced. ET assays include the ABTS/TEAC, CUPRAC, DPPH, Folin-Ciocalteu and FRAP methods, each using different chromogenic redox reagents with different standard potentials. This review intends to offer a critical evaluation of existing antioxidant assays applied to phenolics, and reports the development by our research group of a simple and low-cost antioxidant capacity assay for dietary polyphenols, vitamins C and E, and human serum antioxidants, utilizing the copper(II)-neocuproine reagent as the chromogenic oxidizing agent, which we haved named the CUPRAC (cupric ion reducing antioxidant capacity) method. This method offers distinct advantages over other ET-based assays, namely the selection of working pH at physiological pH (as opposed to the Folin and FRAP methods, which work at alkaline and acidic pHs, respectively), applicability to both hydrophilic and lipophilic antioxidants (unlike Folin and DPPH), completion of the redox reactions for most common flavonoids (unlike FRAP), selective oxidation of antioxidant compounds without affecting sugars and citric acid commonly contained in foodstuffs and the capability to assay -SH bearing antioxidants (unlike FRAP). Other similar ET-based antioxidant assays that we have developed or modified for phenolics are the Fe(III)- and Ce(IV)-reducing capacity methods.
Copper (Cu) contamination in agricultural soil poses severe threats to living organisms, and possible ecofriendly solutions need to be considered for Cu immobilization, such as using biochar. A pot ...study was conducted to examine the effectiveness of biochar derived from rice straw (RSB) at various application rates (0, 2.5, 5 and 10% w/w) to mitigate possible risks of Cu solubility and its uptake by ramie (Boehmeria nivea L.) as forage. The plant growth parameters as well as soil chemical properties (pH, electrical conductivity and cation exchange capacity) notably improved with the increasing RSB application. Moreover, prominent reduction was observed in soil bioavailable Cu concentration by 96% with RSB application of 10% relative to control. In addition, Cu content in B. nivea roots, leaves and stems decreased by 60, 28 and 22%, respectively, for 10% RSB application. It was noted that chlorophyll content and gas exchange parameters in leaves were significantly higher at 10% RSB application than in control. Furthermore, 10% RSB resulted in a greater reduction in oxidative stress from the Cu in soil. Thus, soil amendment with RSB demonstrated positive results for Cu stabilization in aged Cu-contaminated soil, thereby reducing its accumulation and translocation in B. nivea and mitigating livestock feed security risks.
•The contaminated soil displayed high Cu concentration.•Rice straw biochar (RSB) increased plant growth and soil pH while reduced Cu uptake.•RSB increased photosynthesis and reduced oxidative stress.•RSB was effective in reducing extractable Cu contents.
The influence of four microbial biostimulants containing various strains of Bacillus subtilis and/or Paenibacillus sp. on the quality of raspberries cv. Delniwa, Poemat, and Enrosadira cultivated in ...two consecutive seasons was investigated. The biostimulants influenced the antioxidant level, antioxidant capacity, phenolic acids and flavonoids profiles, enzymatic activity, and the degree of methylation and acetylation of the pectin in the raspberry fruits. The biostimulants had the greatest effect on the antioxidant content (16% - 20% increase) and capacity in the Delniwa raspberry fruits from the first season. A positive correlation was found between the activity of the β-galactosidase enzyme and ferric reducing power. In the second season, a decrease in the activity of pectin esterase and α-L-arabinofuranosidase and an increase in the degree of methylation of pectin were noted. Our results suggest that the changes in raspberry quality were related to the type of biostimulant applied.
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•Three raspberry varieties were cultivated in organic farm in two seasons.•Applied microbiological biostimulants affected the quality of raspberry.•The biostimulants positively influenced on the antioxidant properties of raspberry.•The biostimulants caused reducing the activity of the pectinolytic enzymes.•Applied biostimulants positively shaped the quality of raspberries.
Germination of seeds is known to affect the nutritional composition of cold-pressed oils. This study focused on the effects of germination on the antioxidants and oxidative stability of linseed and ...sunflower seed oil. As hypothesized, germination led to increased antioxidant activities and tocopherol, chlorophyll and carotenoid content. Analysis revealed a 37.2 ± 3.5-fold and 11.6 ± 1.5-fold increase in polyphenol content in linseed and sunflower seed oil from germinated seeds, respectively. Using LC-HRMS/MS, profiles with up to 69 polyphenolic substances were identified in germinated seed oils for the first time. Germination promoted lipid hydrolysis, as evidenced by NMR, with overall significant decreases in triacylglycerol content leading to increased diacylglycerol and free fatty acid values. Rancimat measurements predicted a 4.10 ± 0.52-fold longer shelf-life for germinated linseed oil. This study successfully demonstrated the potential of germination to develop PUFA-rich oils with enhanced antioxidant capacity and oxidative stability.
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•Germination significantly increased antioxidants in linseed and sunflower seed oils.•Up to 69 phenolic substances from germinated seeds oils were identified by LC-MS/MS.•Rancimat predicted 4.10 ± 0.52-fold longer shelf-life in germinated linseed oil.•NMR revealed significant increase in FFA of 13.46 ± 0.6% in germinated linseed oil.
•We discuss conceptual and technical limitations of ABTS+•, DPPH, and ORAC assays.•Steric accessibility to ABTS+• and DPPH radicals controls antioxidant reactions.•Kinetics is more relevant than ...stoichiometry for all antioxidant efficacy assays.•Kinetic patterns plus solvent/pH effects on rates distinguish HAT from SET mechanisms.•Redirection of assays to distinguish radical quenching mechanisms is recommended.
Assays developed to measure radical scavenging ability of natural compounds have been used as a basis for ranking and recommending best foods for consumption. However, assays often were adapted for screening assays with inadequate consideration of reaction chemistry, particularly kinetics. Recent research results raise serious questions about the chemistry, execution, and application of these assays. This paper critically evaluates conceptual and technical issues that limit use and compromise validity of three commonly-used assays – TEAC/ABTS•+, DPPH, and ORAC. Recommendations are made for discontinuing use of ABTS•+ and DPPH radicals for measuring radical quenching, redirecting them instead to distinguishing electron transfer reaction mechanisms. Conditions required for accurate results in ORAC are reviewed, and recommendations are made for redirecting this assay to distinguishing compounds that quench radicals by hydrogen atom transfer. The mechanistic information so gained can be then applied to understanding how natural antioxidants can be used most effectively in foods.
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