Enzymatic Cleaning of Milk Pasteurizers

Abstract

The use of cleaning agents containing enzymes to reduce the (non-biodegradable) chemical loading of cleaning effluents from milk pasteurizer heat exchangers was investigated on the laboratory and plant scale. In the laboratory trials, an acid treatment (15 min, 0.5% nitric acid, 60°C) was followed by a short rinse with fresh water and then enzymatic treatment (45 min). Temperature and pH ranges were adjusted to the optimum conditions specified by the enzyme manufacturer. Deposit-free metal surfaces were obtained with three enzymes (Savinase ® , Properase 1600 L ® and Esperase ® ). The Savinase ® agent was subsequently used in a field test featuring a milk pasteurizer (ZE 23 WP1, 25,000 l h –1 , Alfa-Laval). Process conditions were matched to the laboratory conditions. After a short final rinse, the heater was opened and visual examination indicated that all surfaces in contact with the product were clean. After one week's fouling/cleaning cycles the surfaces, including the separator, were still clean. These studies indicate that enzyme-based cleaning of milk heaters can be effective. The considerable environmental benefits offered by enzyme cleaners can be realized if some of the remaining difficulties concerning enzyme dosage, process control and economics can be overcome.