Ultrafiltration of coconut milk emulsion "gata" using cellulose acetate and polyamide membranes

Cellulose acetate (CA) membranes were prepared from 25% CA in N,N-dimethylformamide (DMF) and were used in the ultrafiltration (UF) of coconut milk emulsion (CME) with and without emulsifier, namely sodium caseinate or, carrageenan. All UF fractions were analyzed for protein, carbohydrate, oil and phosphate. High values of the membrane rejection coefficient (sigma(r)) for protein and carbohydrate were obtained, especially with added emulsifier; the sigma(r) values for phosphate and oil decreased in the presence of emulsifier. The retentates after ultrafiltration of CME, with and without added sodium caseinate or carrageenan, were tested for stability After 3 min of immersing the samples in a hot water bath (80 degrees C), the retentate without added emulsifier separated into two distinct liquid layers. No change was observed in the retentate with added emulsifier, which shows that ultrafiltration of CME in the presence of added emulsifier, either sodium caseinate or carrageenan, enhanced the stability of CME. Two sets of polyamide membranes were also prepared from 30% polyamide (nylon-6) and were used in the ultrafiltration of CME. Membrane rejection of coconut oil was 100% while sigma(r) values were 94.7% and 88.4% for membranes prepared from dope mixtures containing H2SO4 and HCl, respectively. The results were interpreted in terms of the effectiveness of UF in facilitating the separation of the oil-rich and aqueous phases, i.e. creaming, of CME. Addition of either sodium caseinate or carrageenan to CME during ultrafiltration resulted in dehydration and concentration of the oil and most soluble components of CME in the retentate without significant creaming.