Abstract:
This research was undertaken to test the feasibility of using the foam technology to separate
polyphenols from fruit juices for use as functional food ingredients. The separation performance,
expressed as enrichment ratio, selectivity and percentage recovery, was determined as a function of
operating variables, namely air or N2 flow rate, initial feed concentration, bubble size, solution pH
and the presence of alcohol to modify the surface tension. Measurements were made of the average
bubble size and gas hold-up volume to calculate interfacial area. The bulk phase concentrations
of the polyphenolics in the feed and foam fractions were analysed for total phenolic content by
Folin assay and phenolic composition by reverse phase HPLC. Enrichment factors of up to 6 were
found under optimum conditions of low sugar concentration (6-9 oBrix), low flow rate (0.2-0.6
ml min-1) and acidic pH (3-4). However recoveries were low at around 30% of total phenolics
and selectivity was poor. It was concluded that foam fractionation represents a potential low cost
technology to recover a proportion of the polyphenolic content in an enriched juice concentrate
suitable for use as a functional ingredient.