Cleaning studies of coconut milk foulants formed during heat treatment process

Abstract

To elucidate cleaning of coconut milk foulants, swelling and dissolution of model coconut milk foulants found in batch and continuous heat treatment processes were investigated. The model coconut milk foulants were immersed in aqueous sodium hydroxide (NaOH) solutions at pH range of 7–12. Both model deposits showed little swelling at pH less than 10; increasing pH beyond 10 resulted in a rise of extent of swelling. Proteins and fats in the deposits were removed by NaOH solution. Although some components in the deposits could not be removed by soaking the deposit in NaOH, swollen deposits were less cohesive. Strength of swollen deposits was measured using fluid dynamic gauging (FDG) technique and it was found that the strength decreased with increasing pH of NaOH solution (shear stresses reduced from ∼5 to ∼3.5Pa). Hence, using NaOH solution at appropriate pHs could improve the cleaning efficiency of coconut milk foulants. However, the strength of the deposit formed from a continuous heat treatment process, which was stronger than that obtained from a batch process, could not be measured using FDG (normal stress ∼800Pa, shear stress ∼30Pa). This suggests that other cleaning agents or cleaning conditions should be adopted in cleaning of the deposit formed during continuous heat treatment.