Enzymatic Esterification for Acidity Reduction of Poultry Fat

Abstract

This work studies the acidity reduction of poultry fat through enzymatic esterification with ethanol to convert free fatty acids to ethyl-esters. Poultry fat samples were collected in a Portuguese company and characterized for their acid value (3.3-6.3 mg KOH/g fat), iodine value (73-109 g iodine/100 g fat), density (0.918-0.924 g/cm3 at 15 °C), kinematic viscosity (36.67-39.87 mm2/s at 40 °C) and moisture content (0.2-0.4 wt%). For the esterification, four commercial enzymes were tested as catalyst (Novozym 435, Lipozyme CALB L, Lipozyme RM IM, Palatase 20000 L, all from Novozymes). It was selected the one that contributed to the highest acidity reduction of poultry fat, in this case Novozym® 435, a CALB lipase immobilized in a hydrophobic carrier or acrylic resin. Different operating conditions were studied: reaction temperature (35, 45 and 55 °C), reaction time (from 0 to 5 h), enzyme/fat mass ratio (0.0012 and 0.0024 wt/wt) and ethanol/FFA mass ratio (1.5, 1.6 and 3.1 wt/wt). Results show that at the best operating conditions (2 h of reaction time, 55 °C of temperature, enzyme/fat mass ratio of 0.0024 and ethanol/FFA mass ratio of 1.6 wt/wt) at least 57 % reduction of free fatty acids can be achieved in just one reaction step. The reaction conditions can be further optimized, or a second esterification step can be performed for further reducing the free fatty acids content.