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

Abstract

There is a rising trend of valorizing fruit by-products for different industries. The pineapple pomace is an interesting ingredient for improving different food properties, or for application as animal feed. However, the majority of the works use fresh fruit by-products, which are high-moist, high perishable and unstable, being this approach questionable from an industrial perspective. Therefore, this work evaluated the drying process of pineapple pomace as an alternative to increase its stability. The emergent pre-treatment with ethanol was studied, evaluating both the process parameters and the quality of the final products. 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%, and convective drying was carried out at 40 and 60 °C and 1 m · s-1. Thermal images were obtained during processing, and the different products were evaluated through total phenolic content, antioxidant capacity, water absorption capacity and oil absorption capacity. The temperature had a great influence on the drying kinetics. On the other hand, ethanol did not affect drying time, but reduced the product temperature during processing. A possible limitation of ethanol as dryer accelerator was discussed in relation to the structure of the food. In addition, drying did not affect the bioactive compounds nor technological properties, demonstrating to be 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.