Extraction of organic acids from kiwifruit juice using a supported liquid membrane process

In order to extract or remove organic acids from kiwifruit juice, we evaluated their separation and transport rates through supported liquid membranes (SLMs). The liquid membrane consisted of an organic solution composed of a carrier (Aliquat 336/Alamine 336) and a linear alcohol (oleyl alcohol) and was loaded on a microporous polypropylene support (commercial grade Celgard 2500/2400). These SLMs were evaluated (i) in a batch cell to determine the permeability and (ii) in a continuous spiral membrane module to study the effects of various process parameters - flow of feed and strip solutions, membrane composition, recycling mode of operation and kiwifruit juice at natural pH. It was observed that there exists an optimum for each system: pH 2.5-3.0 for Alamine 336/oleyl alcohol and pH 4.5 for Aliquat 336/oleyl alcohol. At this pH the flux rates of citric acid and malic acid was greater (6-8 times) than that of quinic acid. The flux rates decreased (greatly for citric acid) with the flow rate of feed and strip solutions and increased (considerably for citric acid) with the SLM composition. The recycling of feed and strip solutions significantly improved the removal efficiency. The SLM system retained its performance over a period of a few days. The SLM process allowed extraction of the above three organic acids (ascorbic acid was removed in trace amounts) from kiwifruit juice at a rate of a few percent (5%) in a single-pass processing.