Valorization of pineapple pomace for food or feed: effects of pre-treatment with ethanol on convective drying and quality properties

Abstract

This work studied ethanol as a pre-treatment to the convective drying of pineapple pomace, also evaluating the product main bioactive and technological quality properties. The pineapple pomace was obtained as a residue of juice extraction, being characterized as high moisture and fibrous nature, with little structural organization. The pre-treatment consisted of spraying ethanol on the samples in concentrations of 5 and 10% (w/w, ethanol/pomace), and convective drying was carried out at 40 and 60 °C at 1 m s−1. Thermal images were obtained during processing. The different treatments were evaluated through total phenolic content, antioxidant capacity, water absorption capacity and oil absorption capacity. Temperature strongly influenced the drying kinetics. On the other hand, ethanol did not affect drying time, but reduced the product temperature during processing. This result highlights a possible limitation of ethanol as a drying accelerator since the microstructure of pineapple pomace results in lower internal resistance to mass transfer. In addition, drying did not affect the bioactive compounds nor technological properties of the dried pomace. Therefore, this work demonstrated drying is a good alternative to increase the stability of pineapple pomace, without compromising its quality, being thus an interesting ingredient for application in food formulations or as animal feed.