M.J. Núñez

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.

Enzymatic pretreatment to enhance oil extraction from fruits and oilseeds : a review

Abstract Enzymatic treatment to enhance oil recovery from olive, avocado or coconut pastes has been used with excellent results both on a laboratory and industrial scale (olive) obtaining the oil in shorter times and increasing the capacity of the equipment. This treatment was tried for the extraction of oil and protein from oilseeds on a laboratory scale (peanut, rapeseed — also in a pilot plant — sunflower and soybean). Considering that two thirds of the total fat and oil production is supplied by oilseeds (soybean, sunflower, rape and palm accounting for more than 70% of vegetable oils) this is a promising field for biotechnological applications. In the present work the different processes, as well as the factors affecting their efficiency, are discussed.

Enzyme-assisted hexane extraction of soya bean oil

Abstract An enzymatic treatment with carbohydrases was performed either simultaneously with or prior to the hexane extraction of oil from soya grits. The enzymatic treatment increased the oil extractability by 5% of the extractable oil when it was carried out simultaneously with the oil extraction and 8–10% if the treatment was carried out prior to the solvent extraction. For this latter case, the fraction ‘easily’ extractable increased up to 7.5%. With regard to the products, the in-vitro apparent digestibility of the meal was slightly improved by 3%, and the enzyme assisted extracted oil contained higher free fatty acids and phosphorus contents than the oil from untreated samples ( P

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.

Enzymatic saccharification of alkali-treated sunflower hulls

The treatment with NaOH and subsequent enzymatic hydrolysis of sunflower hulls was evaluated. Maximum saccharification values for sunflower hulls were reached after treatments with 0·5% alkali solutions for 1·5 h at 121°C using a solid: liquid ratio of 0·1 g/ml. The hydrolysis yield increased with enzyme concentrations up to 50 FPU/g, the additional enhancement with higher concentrations being hardly noticeable. In spite of dramatic alterations in the structure caused by the alkaline treatment, structural features seemed to remain as major hindrances to enzymatic hydrolysis.

Oil extractability from enzymatically treated soybean and sunflower: range of operational variables

Abstract An evaluation of the feasibility of enzymatically treating oil seeds (soya beans and sunflower kernels) to improve the extractability of oil is presented. The effects of each variable affecting the process (mechanical treatment, moisture percentage, enzyme concentration and time of hydrolysis) were studied to define the optimum range of operation for each of them as a function of the extractability of samples treated with different enzyme formulations. Size reduction of the seeds favours the efficiency of the enzymatic treatment related to oil extractability. For a fixed particle size, moisture contents of 60 and 40% selected for soybean and sunflower respectively, regardless of the kind of enzyme, are suitable to efficiently increase the extractability of the seed. The enzyme/seed ratio is dependent on the formulation. Time of hydrolysis must also be optimized to avoid long reaction times which do not result in notable increases in the amount of recovered oil.

Enzymatic treatment of sunflower kernels before oil extraction

Sunflower kernels were enzymatically treated before pressing, with the aim of enhancing oil extractability. Following the response surface methodology, the combined effects of moisture, enzyme/kernel ratio and treatment time were examined. The effect of these variables on the pressing efficiency, the protein digestibility, the fiber content and the meal color was assessed. In a wide range of conditions, it was found that the pressing efficiency was higher for treated kernels, obtaining 13% additional oil compared with untreated samples. Also, the in vitro apparent digestibility coefficient of the meal was improved and the total fiber content was reduced. A slight darkening of the meal was observed as a result of the operational conditions during the treatment. The solvent extractability of the enzymatically treated pressed cakes was enhanced compared with that of the untreated sample.

Oxalic acid production by Aspergillus niger

Aspergillus niger is able to produce a quite high concentration of oxalic acid using sucrose as carbon and energy source. Operating at pH higher than 6 and an enriched N and P medium is necessary in order to conduct the fermentation towards oxalic acid production. A pH shift technique, operating at acid pH in the first two days and then setting pH to 6, allowed the productivity to slightly increase in shaking flasks cultures up to 3.0 kg/m 3 . d, with a final oxalic acid concentration of 29 kg/m 3 . When operating at more controlled conditions, in a stirred tank, both productivity and oxalic acid concentration were improved (4.1 kg/m 3 . d and 33.8 kg/m 3 , respectively). However the main drawback of this fermentation is the low yield attained (about 0.3 kg oxalic acid/kg sucrose) because most of glucose, resulting from the hydrolysis of sucrose by the extracellular enzymes secreted at the beginning of the fermentation, is very quickly oxidised to gluconic acid, a process which is favoured at a pH close to 6. Milk whey was proved to be a very good substrate as it allows oxalic acid to be produced with a similar productivity (2.5 kg/m 3 . d in shaking flasks) giving excellent yields of almost 0.6 kg oxalic acid/ kg lactose.

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.

Ethanol extraction of polyphenols in an immersion extractor. Effect of pulsing flow

A comparative study on polyphenol extraction from sunflower press cake in a semicontinuous pulsed-flow immersion extractor and in a conventional laboratory immersion extractor was developed. The solvent was 96% (vol/vol) ethanol. No difference in the residual polyphenol content in the cake was observed at short times, but after 10 h, the pulsed extractor showed a higher polyphenol concentration in the outlet miscella. In addition, the effective diffusivity of polyphenols in sunflower press cake was estimated.