Andrés Moure

Natural antioxidants from residual sources

The growing interest in the substitution of synthetic food antioxidants by natural ones has fostered research on vegetable sources and the screening of raw materials for identifying new antioxidants. Oxidation reactions are not an exclusive concern for the food industry, and antioxidants are widely needed to prevent deterioration of other oxidisable goods, such as cosmetics, pharmaceuticals and plastics. Polyphenols are the major plant compounds with antioxidant activity, although they are not the only ones. In addition, other biological properties such as anticarcinogenicity, antimutagenicity, antiallergenicity and antiaging activity have been reported for natural and synthetic antioxidants. Special attention is focussed on their extraction from inexpensive or residual sources from agricultural industries. The aim of this review, after presenting general aspects about natural antioxidants, is to focus on the extraction of antioxidant compounds (mainly polyphenols) from agricultural and industrial wastes, as well as to summarize available data on the factors affecting their antioxidant activity and stability, and, in some cases, the reported major active compounds identified.

In vitro antioxidant properties of crude extracts and compounds from brown algae

Research on the bioactives from seaweeds has increased in recent years. Antioxidant activity is one of the most studied, due to the interest of these compounds both as preservatives and protectors against oxidation in food and cosmetics and also due to their health implications, mainly in relation to their potential as functional ingredients. Brown algae present higher antioxidant potential in comparison with red and green families and contain compounds not found in terrestrial sources. In vitro antioxidant chemical methods, used as a first approach to evaluate potential agents to protect from lipid oxidation in foods, confirmed that the brown algae crude extracts, fractions and pure components are comparatively similar or superior to synthetic antioxidants. Particular emphasis on the fucoidan and phlorotannin polymeric fractions is given, considering variations associated with the species, collection area, season, and extraction and purification technologies.

Antioxidant activity of extracts from Gevuina avellana and Rosa rubiginosa defatted seeds

Abstract Chilean hazelnuts (Gevuina avellana Mol) and mosqueta rose (Rosa aff. Rubiginosa L.) meals were extracted with methanol, ethanol, acidified water, acetone, butanol, diethyl ether and ethyl acetate. Ethanol and methanol extracted the highest amount of soluble substances from both seed meals. The highest concentration of total polyphenols was found in the ethanolic extracts, although that of acetone from R. rubiginosa presented similar values. The antioxidant activity of the extracts evaluated by the β-carotene assay and with as hydrogen radical scavenging ability showed that the activity of the butanol and methanol extracts from G. avellana was comparable to those of synthetic antioxidants butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). The 2,2,-diphenyl-1-picrylhydrazyl radical (DPPH) radical scavenging activity of the G. avellana methanol, ethanol and water extracts was 2–3 times lower than those of BHT and BHA, respectively. The activity of R. rubiginosa extracts ranged from that of BHT for the water extracts to 80% inhibition in respect to control achieved with the ethanol extracts.

Fractionation of Antioxidants from Autohydrolysis of Barley Husks

The liquid phase from nonisothermal autohydrolysis of barley husks was extracted with ethyl acetate and redissolved in ethanol to yield a crude extract (denoted BHEAE), which was subjected to further processing to enhance the antioxidant activity. A fractionation method, carried out for characterization purposes, consisted of the extraction of BHEAE with organic solvents of increasing polarity and further fractionation in Sephadex LH-20. Among the tested solvents, ethyl acetate allowed the highest yield, phenolic content, and antioxidant activity. Upon elution with methanol, products with high DPPH radical scavenging capacity (IC50 = 0.22 g/L) were obtained. The major compounds in the isolate were benzoic and cinnamic acids. Adsorption-desorption in commercial polymeric resins was carried out as an alternative strategy for BHEAE refining. This method is more suited for possible scale-up and provided a concentrate with a Trolox equivalent antioxidant capacity of 9 mM, which was obtained at a yield of 18 g/kg of barley husks.

Hydrothermal fractionation of Sargassum muticum biomass

Sargassum muticum is an invasive brown alga which could be regarded as a renewable resource susceptible to fractionation and integral valorization. S. muticum biomass was processed according to a scheme consisting of conventional alkaline extraction of alginate, ultrafiltration to concentrate antioxidant compounds lost in the waste streams and autohydrolysis of the solid residue remaining after alginate extraction. The effect of temperature during non isothermal autohydrolysis was optimized to maximize yields and antioxidant activity of the solubilized fraction. The overall solubilization yield reached 88% of the initial material and the solubilization yield from the alginate-exhausted solid up to 82%. The waste fraction concentrated by membrane technology and that solubilized during autohydrolysis showed radical scavenging and reducing activities comparable to commercial antioxidants. The solid insoluble by-product from the autohydrolysis stage could be potentially useful for agricultural purposes.

Simultaneous Extraction and Depolymerization of Fucoidan from Sargassum muticum in Aqueous Media

The biomass components of the invasive seaweed Sargassum muticum were fractionated to allow their separate valorization. S. muticum (Sm) and the solid residue remaining after alginate extraction of this seaweed (AESm) were processed with hot, compressed water (hydrothermal processing) to assess the effects of temperature on fucoidan solubilization. Fucose-containing oligosaccharides were identified as reaction products. Operating under optimal conditions (170 °C), up to 62 and 85 wt% of the dry mass of Sm and AESm were solubilized, respectively. The reaction media were subjected to precipitation, nanofiltration and freeze-drying. The dried products contained 50% and 85% of the fucoidan present in Sm and AESm, respectively; together with other components such as phenolics and inorganic components. The saccharidic fraction, accounting for up to 35% of the dried extracts, contained fucose as the main sugar, and also galactose, xylose, glucose and mannose. The concentrates were characterized for antioxidant activity using the TEAC assay.

Recovery and Concentration of Antioxidants from Winery Wastes

: Grape and wine byproducts have been extensively studied for the recovery of phenolic compounds with antioxidant activity and a variety of biological actions. The selective recovery and concentration of the phenolic compounds from the liquid phase separated from further diluted winery wastes has been proposed. Adsorption onto non ionic polymeric resins and further desorption with ethanolic solutions was studied. Several commercial food grade resins were screened with the aim of selecting the most suited for the practical recovery of phenolic compounds with radical scavenging activity. Under the optimized desorption conditions (using Sepabeads SP207 or Diaion HP20 as adsorbents and eluting with 96% ethanol at 50 °C) a powdered yellow-light brown product with 50% phenolic content, expressed as gallic acid equivalents, was obtained. The radical scavenging capacity of one gram of product was equivalent to 2–3 g of Trolox.

Purified Phenolics from Hydrothermal Treatments of Biomass: Ability To Protect Sunflower Bulk Oil and Model Food Emulsions from Oxidation

The phenolic fractions released during hydrothermal treatment of selected feedstocks (corn cobs, eucalypt wood chips, almond shells, chestnut burs, and white grape pomace) were selectively recovered by extraction with ethyl acetate and washed with ethanol/water solutions. The crude extracts were purified by a relatively simple adsorption technique using a commercial polymeric, nonionic resin. Utilization of 96% ethanol as eluting agent resulted in 47.0-72.6% phenolic desorption, yielding refined products containing 49-60% w/w phenolics (corresponding to 30-58% enrichment with respect to the crude extracts). The refined extracts produced from grape pomace and from chestnut burs were suitable for protecting bulk oil and oil-in-water and water-in-oil emulsions. A synergistic action with bovine serum albumin in the emulsions was observed.

Characterisation of protein concentrates from pressed cakes of Guevina avellana (Chilean hazelnut)

Protein concentrates, produced by aqueous extraction and membrane filtration from Guevina avellana pressing cakes, were characterized with regard to nutritional and functional properties. The effect of a previous enzymatic treatment, carried out with the aim of enhancing oil extractability during pressing, was also evaluated. Thermal conditioning of the seeds, before pressing, influenced oil and protein extractability, as well as the nutritional quality and functional properties. The protein concentrates contained up to 65% protein with an in vitro apparent digestibility coefficient in the range 75–80%. They presented a reduced ability to bind water, but they retained almost up to ten times their weight of oil.

Valorization of Sargassum muticum Biomass According to the Biorefinery Concept.

The biorefinery concept integrates processes and technologies for an efficient biomass conversion using all components of a feedstock. Sargassum muticum is an invasive brown algae which could be regarded as a renewable resource susceptible of individual valorization of the constituent fractions into high added-value compounds. Microwave drying technology can be proposed before conventional ethanol extraction of algal biomass, and supercritical fluid extraction with CO2 was useful to extract fucoxanthin and for the fractionation of crude ethanol extracts. Hydrothermal processing is proposed to fractionate the algal biomass and to solubilize the fucoidan and phlorotannin fractions. Membrane technology was proposed to concentrate these fractions and obtain salt- and arsenic-free saccharidic fractions. Based on these technologies, this study presents a multipurpose process to obtain six different products with potential applications for nutraceutical, cosmetic and pharmaceutical industries.