Estudo das etapas de degomagem e neutralização do óleo de farelo de arroz

Abstract

Rice oil is defined as edible oil obtained from rice bran (Oryza Sativa) through appropriate technological processes. The oil must pass through a refining process so it is able for the consumption. The chemical refining is composed by degumming, neutralization, bleaching, dewaxing and deodorizing stages. The degumming aims the removal of phospholipids present in the oil, and it may be done by chemistry (using acids) or aqueous (water). The advantage of degumming with water is the obtaining of pure lecithin (phospholipids), which has commercial appeal. The neutralization stage aims the removal of free fat acids present in the oil and it may be done by chemistry (addition of NaOH solution) or physics (distillation). The chemical neutralization is considered the most difficult stage for the oil refining, due to the formation of neutralization grounds that drags with it part of the neutral oil and great part of the antioxidant γ-oryzanol. This paper presents as main goal the study of degumming and neutralization stages of rice oil refining in order to obtain a greater reduction on the level of phosphorus and lower losses of γ-oryzanol. The quality of the crude, degummed and neutralized oils was evaluated, in relation to the relative density, refractive, saponification, iodine, peroxide, acidity indexes, phosphorus level and γ-oryzanol level. The study of the degumming stage was performed through Rotation Central Composite Design, where the variables of the study were the quantity of water added and the process temperature, and the phosphorus level was the response variable. The best work region for the degumming stage, in other words, the greater reduction of phosphorus level, was determined on the condition of 5% of water and temperature of 58°C. The study of the neutralization stage was performed through factorial experimental plan (2k), being the study variables the quantity of excess of NaOH solution 30% p/p added and temperature, and acidity and γ-orizanol as response variable. From the obtained results it was possible to define condition of 20% of NaOH excess and temperature of 60 ºC as the conditions to obtain better results, in other words, lower reduction of γ-oryzanol level and acidity within the standards required by law. On the degumming stage, the oil phosphorus level was 4.10 mg/100g, showing that the goals were accomplished, since the phosphorus level was reduced below the level required by law. In relation to the neutralization stage it can be said that the goals were achieved, since an acidity of 0.41% was obtained, maintaining below the level required by Anvisa (0.80%) and the loss of γ-oriyanol was of 30%, lower than 90% of loss described on the literature.