Drying of milk-blackberry pulp mixture in spouted bed

Author(s)

Matheus Boeira Braga

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Química
• Defense date: 2014-10-27

Examining board members

Sandra Cristina dos Santos Rocha; Claudia Regina Fernandes de Souza; Carlos Alberto Severo Felipe; Virginia Aparecida da Silva Moris; Ana Silvia Prata

• Advisor: Sandra Cristina dos Santos Rocha

Abstract

Blackberry is a seasonal fruit, climacteric and highly perishable, whose availability is limited by the periods between crops. Blackberry drying aims at enhancing its conservation, therefore, the development and application of drying techniques such as spray drying, spouted bed drying and freeze drying, which could increase the shelf life of this product is of great interest. The high reducing sugar and water content of pure blackberry pulp may result in low powder production during the drying process. On the other hand, drying of whole milk has shown good powder yields and product quality. A milk-blackberry mix paste becomes an alternative which may improve the process efficiency, reduce post-harvesting waste, and increase the shelf life of the product without significantly altering its nutritional characteristics. The main steps undertaken during the implementation of this project were: (i) analysis of conical-cylindrical spouted bed drying of a paste mixture of milk and blackberry pulp of fixed concentration, using different kinds of inert beads. Atomization and dripping of the paste were compared as feeding modes. The experimental design used atomization feeding to analyze the effects of air temperature (Te), paste feeding flow rate (Wf) and paste atomization pressure (Pat) on the drying performance. The best results were obtained for drip feeding on polystyrene beads using Te= 60 oC and Wf= 2 mL/min, yielding powder production efficiency greater than 60%, low final moisture content of the powder and less than 15 % anthocyanin degradation; (ii) analysis of conical-cylindrical spouted bed drying of milk-blackberry pulp mixture at different ratios (V/V). Afterward, analysis of the effects of addition of adjuvant (maltodextrin 10 DE, casein and palm oil) in the milk-blackberry mixture and maltodextrin in the pure blackberry pulp were made focusing on powder production efficiency.The paste formulated with milk and blackberry at a ratio of 25%: 75% (V/V) was the most appropriate for the drying process in terms of hydrodynamic stability, mass of blackberry pulp used on paste formulation and process performance, and also for the quality of the powder; (iii) analysis of a new spouted bed configuration (rectangular cross-section with air entry through two bottom slots), investigated as a dryer of milk and a paste mixture of milk and blackberry pulp. Drying of milk-blackberry pulp in a slot-rectangular spouted bed using polystyrene beads and the conditions Wf= 6 mL/min, and Te= 60 oC resulted in powder production efficiency greater than 75% and low moisture content. Similar results of drying performance were obtained in the slot-rectangular spouted bed as to and conventional spouted bed for the same inert and the same conditions of inlet air temperature and relative humidity. However, the slot-rectangular spouted bed allowed the paste feeding flow rate to be tripled and the bed to be operated at a lower superficial air velocity compared to the conventional geometry, showing its potential for scale-up (AU)

• FAPESP's process: 11/20031-2 - OBTAINING OF MILK-BLACKBERRY POWDER BY DRYING IN SPOUTED BED
• Grantee: Matheus Boeira Braga
• Support Opportunities: Scholarships in Brazil - Doctorate