Study on swelling and cleaning of egg yolk deposits at laboratory scale

[摘要] Fouling has always been a major problem in the food processing industry where thermal treatment is involved. Cleaning of food deposit formed from fouling phenomenon is always a tough challenge for food industry as it affects product safety and hygiene, and production cost. Egg yolk was used in this study as a model fouling deposit on stainless steel surface. It mainly contains protein and lipids which makes it difficult to be cleaned once thermally induced on a surface. Experiments were conducted to study the effect of various parameters on swelling and removal of egg yolk deposits during hydration, the influence of chemical and mechanical action on swelling and removal of egg yolk deposit during hydration, and the effect of various parameters on cleaning of egg yolk deposits at laboratory scale and the adhesive and cohesive strength of egg yolk deposits. Sets of experiments were carried out by soaking the egg yolk deposits in different kind of hydrating solutions (water, NaOH, LAS solution and commercial detergent solution) at different concentrations (0.5 and 1% w/v), temperatures (20, 40, 60, 80oC), stirring speeds (200 and 400 rpm), stirring methods (magnetic stirrer and mixing impeller) and sample configurations (horizontal and vertical). Deposit swelling, moisture content and removal were measured during the experiments. Experiments were also conducted to study the effect of different temperatures (40, 60 and 80oC), cleaning agents (NaOH and LAS solution), and chemical concentrations (1 and 5 % w/v) on cleaning of egg yolk deposits by cleaning rig at 0.5 ms-1 flow velocity. Micromanipulation technique were used in this study to measure the apparent adhesive and cohesive strength of egg yolk deposits at different pre-soaking time (15 and 30 minutes), temperatures (20, 40, and 60oC), cleaning fluids (NaOH and LAS solution), and chemical concentrations (1 and 5 % w/v). It was found that temperature plays a major role on swelling and cleaning of egg yolk deposits during hydration. In some cases, swelling and deposit removal occurred simultaneously during hydration. At, 80oC hydration, a complete removal was achieved in all cases. Mechanical and chemical action was also found to affect swelling and deposit removal of egg yolk deposits during hydration. However, the effect of different sample configurations was unclear.Cleaning of egg yolk deposits by cleaning rig can divided into three different phases i.e. lag phase, removal phase and constant phase. No complete deposit removal was achieved after 4 hours of rinsing with water, even at the highest temperature (80oC). At 40oC, no complete removal was obtained after 4 hours of experiment in all cases. Increasing the chemical concentration would increase the deposit removal. At 60 and 80oC, deposits were totally removed in all cases. Increasing the chemical concentration reduced cleaning time of egg yolk deposit and sodium hydroxide solution gave shorter cleaning time than LAS solution. Increase in hydration temperature, hydration time and pre-soaking chemical concentration result in lower adhesive and cohesive strength of egg yolk deposits. The adhesive strength was found to be greater than the cohesive strength in all cases. It can be concluded that temperature dominates the swelling and cleaning of egg yolk deposits while mechanical and chemical action also play an important role in swelling and cleaning of egg yolk deposits.

[发布机构] University:University of Birmingham;Department:School of Chemical Engineering

[关键词] T Technology;TP Chemical technology