Producción de concentrados de acilglicéridos ricos en ácidos grasos omega-3

Résumé

The production of omega-3 concentrates is of great interest in food, pharmaceutical and cosmetic industries. Many scientific papers about the proven benefits of these fatty acids in human health have been published. Numerous epidemiological and clinical studies show that regular consumption of EPA and DHA reduces the risk of cardiovascular disease, helps the good neuronal function and cerebral and retinal development, and it has been even attributed a decrease in the risk of colon and breast cancer. However, the sustainable production of concentrates oxidatively stable and highly bioavailable by humans is still under development. Fish oils, particularly from species which live in cold and deep waters, are one of the richest sources of EPA and DHA. Fish species with little commercial value or byproducts from processed fishes are attractive materials to obtain omega-3 concentrates. The fatty acids are not usually presented as free forms; they are naturally esterified to glycerol molecule, forming the triglycerides. The concentration of omega-3 as triglyceride form is very complex, since they are more or less randomly distributed on the glycerol skeleton. Combined techniques of enzyme reaction (hydrolysis, glycerolysis or ethanolysis) followed by fractionation method to separate and concentrate lipid derivatives of interest are generally used. The stability and bioavailability of omega-3 concentrates depend on the chemical form in which they are. They can be presented as free fatty acids, ethyl or methyl esters, acylglycerides (monoglycerides and diglycerides) or phospholipids, depending on the reaction used in their production. Some studies have showed that the oxidative stability of omega-3 in acylglyceride form is higher than omega-3 in ethyl ester form. Furthermore, the acylglycerides present the highest bioavailability since they are direct substrates of pancreatic lipase. Therefore, monoglycerides (MG) and diglycerides (DG) containing omega-3 fatty acids have important applications in functional foods and dietary supplements. Furthermore these molecules, especially MG, have excellent emulsifying properties, in fact they represent the 70% of synthetic emulsifiers currently produced. MG and DG are usually produced by chemical or enzymatic reaction. The enzymatic catalysis is preferable to the chemical one because of using mild temperatures and short reaction times. The glycerolysis reaction produces the highest amount of MG and DG. When this reaction is carried out, it should be taken into account that the substrates, oil and glycerol, are immiscible; this is a two-phase system. Consequently, there is a reduced contact between the substrates and the enzyme and hence low conversion products. To solve this problem, organic solvents or surfactants are often used to homogenize the system. Damstrup et al. concluded that tertiary alcohols (tert-butanol and tert-pentanol), due to their polarity, are one of the best ways to carry out this reaction. They are able to produce a homogeneous mixture and therefore, lead high reaction yields. In conclusion, in this work MG and DG production by enzymatic glycerolysis of sardine oil with two commercial lipases and tert-butanol and tert-pentanol as reaction media have been studied. Before to kinetic study, the liquid-liquid equilibrium of the ternary mixtures: tert-alcohol + sardine oil + glycerol were studied to determine the minimum amount of solvent should be employed to ensure that the system is homogeneous, depending on the reaction conditions (temperature and substrate mole ratio).