Influence of the Neutralization Step on the Oxidative and Thermal Stability of Acid Olive Oil

Abstract

This study elucidate the modification on oxidative and thermal stability of acid olive oils during the neutralization step. The neutralization of an acidified olive oil, chosen as model, was carried out by substituting lime (calcium hydroxide) for soda (sodium hydroxide) as the neutralizing agent. Resulting olive oil preserved almost 95% of their a-tocopherol content and had higher temperatures of thermal decomposition than oils neutralized with soda. Oils neutralized with lime had better oxidative stability since the losses of their natural antioxidants, particularly tocopherols, were very limited. The neutralization with soda was accompanied by a passage of epoxides and hydroperoxides (products of first stage of oxidation) to a, b-unsaturated aldehydes and ketones (products of second stage of oxidation). These purposes were confirmed by thermal spectrophotometric analyses and the increase of the carbonyl value after neutralization.

Palm oil mill effluent (POME) precipitation using ammonium-intercalated clay coagulant

“…The reduction of FFA and TSS was analyzed and shown in Figures 6 and 7, respectively. FFA reduction was included as an urgent parameter to avoid generating undesirable odors, hydrolysis, and triggering the oxidation process of the organic content of POME in the water bodies [36,37]. These processes became the reason eutrophication occurred.…”

Refining Vegetable Oils: Chemical and Physical Refining

“…Vegetable oils containing a high percentage of free fatty acids (by hydrolysis and/or oxidation) must be refined to be edible [ 49 ]. The presence of these compounds in crude oils poses many problems for the storage and result in an undesirable color and odor in the final product [ 6 , 25 ].…”

“…Many methods for fatty acids elimination have been developed to improve the value of degraded vegetable oils. Some include chemical refining with caustic soda neutralization and physical refining based on steam distillation [ 49 , 50 ].…”

“…In terms of economic perspective, caustic soda neutralization cannot be applied to oils having a percentage of free fatty acids greater than 15 g/100 g because the loss of neutral oil in soaps becomes very significant [ 49 ].…”