Dried berry pomace as a source of high value-added bioproduct: drying kinetics and bioactive quality indices

Developing berry pomace into a potential value added product for the food and other industries: Pomace is the major waste product of fruit processing operations such as juicing and winemaking. However, fruit pomaces contain many functionally important bioactive molecules, such as proteins, vitamins, minerals, and phenolic compounds. Phenolic compounds are of particular importance due to their health benefits, antioxidant activity, application as flavour and colour food ingredients, and antimicrobial activity. As the agriculture and agri-food sector is facing the increasing problems of waste and cost reduction of industrial processes, there is opportunity to position pomace as a high value product. Fruit pomace is a highly perishable material subject to spoilage due to its high moisture content. Therefore drying is an important processing step in ensuring product stability in terms of shelf life and maintaining quality for utilization as a value added product. Freeze drying is an effective drying method as materials undergoing freeze drying are not exposed to high temperatures, so destruction of any bioactive compounds present is minimized. However, freeze drying is not the ideal drying option for processing cost competitive products due to long processing times and high operating costs. Convective air drying is an industrially relevant technology for the production of stabilized materials with optimal quality. The focus of this work was to identify suitable operating parameters, such as drying temperature and product load, in the convection air drying process to minimize drying time and ensure optimal product quality of different berry pomace types (Merlot grape, cranberry, highbush blueberry, and wild lowbush blueberry). This work showed that levels of phenolic compounds and antioxidant activity in pomace subjected to cabinet convection air drying were generally comparable to levels in freeze dried pomace. Results indicated that subjecting the berry pomace to shorter processing times upon cabinet convection air drying (half load density at 70 C) exhibited better bioactive quality retention. This work indicated that cabinet convection air dried berry pomace could be a source of bioactive compounds with potential use as an additive for the food industry or other industries.