Melanoidins and polyphenols recovery from soluble coffee production wastewater employing non-ionic polymeric resins

Coffee is among the most consumed beverages worldwide, but its processing generates waste and wastewater. These can be seen as valuable resources containing melanoidins and polyphenols, which possess e.g. antioxidant capacity. This work focuses on the recovery of these compounds from soluble coffee production wastewater. Six non-ionic polymeric resins were screened. XAD16, FPX66 and XAD761 presented the highest melanoidin adsorption, while the first two and PAD600 showed the highest adsorption of polyphenols. Adsorption kinetics was also evaluated. Desorption with acidified ethanol was fast and efficient, and desorbed solutions presented an enrichment of melanoidins and polyphenols in relation to carbohydrates, when compared to the original effluent. XAD16 and FPX66 could recover 65%, 60% and 55% of melanoidins, polyphenols and antioxidant capacity of the effluent. XAD761 presented lower recoveries, but higher melanoidin purification in relation to carbohydrates. Rotary evaporation of desorbed solutions was able to preserve and concentrate melanoidins, polyphenols and antioxidant capacity, while recovering ethanol for reuse. Melanoidin adsorption presented a good fit to the Liu isotherm model, indicating a cooperative adsorption effect, while for polyphenols both Liu and Freundlich seemed adequate. The stability of adsorption and desorption ratios after three cycles indicate good regeneration capacity and reusability of the resins. In view of its overall performance and lower cost, FPX66 seems a promising option for the recovery of melanoidins and polyphenols from soluble coffee production wastewater. The recovered products could be applied as antioxidants and/or coloring in food, pharmaceutical and cosmetic products, turning wastewater compounds into valuable resources.