Application of Citrus Bioadsorbents as Wine Clarifiers

The Spanish law 24/2003 of the Vine and the wine (BOE of 11 july2003), defines the wine as the natural food obtained exclusively by the alcoholic fermentation, total or partial, of fresh grapes, crushed or not, or of grape must. One of the biggest problems in the manufacture of wine is the residues of grapes, microorganisms and fermentation remains that are deposited in the bottom of the bottle.

Limpidity and stability are achieved both by physical procedures (cold, filtering, centrifugation, racking) and chemical (clarification). While the physical procedures allow to extractor eliminate the particles that cause the turbidity and sedimented microorganisms, thus obtaining the biological stability, the chemists allow to achieve the desired physicochemical stability.

Artificial (or provoked) clarification consists of introducing certain colloidal substances to the wine, which, flocculating, increase their size and deposit themselves in the bottom of the vessels, dragging with them (by adsorption and partly by action Mechanical) the particles scattered in the wine (Hidalgo 2003).

The clarifying agents are selected depending on the item you want to remove. If an excess of astringent and/or drying polyphenolic compounds is detected in the wine, it is advisable to add high molecular weight proteins (such as long-chain gelatines or egg albumin). These will adsorb unwanted compounds and Eliminated by getting a smooth effect on the final wine. On the contrary, if the wine has a protein instability accused it is advisable to add inorganic compounds (such as bentonite or silica gel) so that during the process drag this excess protein and achieve the stability sought (Ribéreau-Gaiusn et al., 1982).

The use of clarifying agents is regulated by Regulation (EC) No 606/2009, which determines the substances that can be used. Currently, they are allowed: food gelatine, protein materials of vegetable origin from wheat, pea and potato; Casein; Fish tail; Potassium caseínatos; Egg albumin; Bentonite; Silicon dioxide in the form of a gel or colloidal solution; Kaolin; Tannins Pectolytic enzymes and enzyme preparations of betaglucanase.

On the other hand, there is a wide variety of materials available in large quantities that have been proposed as adsorbents: natural products, agricultural waste of food industries, among others. In many cases, these residues have been processed to obtain active charcoal, for example, coconut residues (Selomuya et al., 1999) or sugarcane (Mohan and Singh, 2002). The current trend is the use of agro-industrial waste as an alternative for the preparation of biosorbent materials, since they are cheap and effective in the elimination of heavy metal ions (Fuand Wang, 2011).When processed by physicochemical methods (Vijayaraghavan and Balasubramanian, 2015), cation exchange is the mechanism accepted in the case of the removal of metal ions.

Another area of use of bioadsorption as an alternative process (economic and with acceptable environmental impact) is that of wastewater from the textile industry. Traditionally, these wastewaters have been treated with physical and chemical processes that are costly to eliminate the colorants present. These processes incur operating and maintenance expenses that most small industries are unable to absorb (Lu et al., 2010) (Simphiwe et al., 2012). It should be noted that synthetic dyes are widely used indifferent types of industries: textiles, paper, pharmaceutical, food, cosmetics, etc., using, approximately 10,000 dyes and pigments of which almost 70% are type azo dyes.

The structural complexity of these xenobiotics compounds translates into alow percentage of elimination of the same in conventional treatment plants, which is why they are discharged without being treated (Gupta and Sahas, 2009). In this way, they provoke different impacts on the environment, producing variations in the waters in terms of suspended solids, ionic load, toxicity, dissolved oxygen concentration, color.

Adsorption is a new treatment option (Wang and Li, 2007) (Afsin, 2007) because it is a substance separation operation, which is done by putting in contact a fluid with a solid adsorbent. This is a surface phenomenon by which the sorbate is retained on the outer surface and the inner pores of the solid (Wang and Zhu, 2007). The superficial retention of these organic molecules is explained by a four-stage mechanism: diffusion of the dye towards the surface of the bioadsorbent; diffusion of the dye through the pore of the bioadsorbent; start of the dye bioadsorption process and final dye bioadsorption process. (Sivakumar and Palanisamy, 2010).

For its part, the chemical procedure of clarification is a process of attraction between the positive loads of the clarifying agents and the negatives of the impurities of the wine so that, by attraction, conglomerates are formed that precipitate at the bottom of the deposits in the form of flocs. This process is carried out after the malolactic fermentation, when the wine presents the highest concentration of solid materials in suspension. The doses used depend on the clarifying agent used and the type of wine treated.