Ultrasonic Assisted Drying and its Effect on 3D Printability of Minced Beef and Other Foods

The aim of this master thesis project was to investigate the impact on drying kinetics of ultrasound during air drying by a new ultrasonic transducer, on which a patent application has been filed by CSIRO. Convection drying using hot air is currently the conventional method of drying in the industry due to its simplicity and low cost. To increase product quality, freeze drying utilises a vacuum but is highly energy consuming. The ultrasonic transducer is set to increase the drying speed, thus potentially replacing a need for the energy consuming vacuum. In this work, the effect the ultrasound had on drying kinetics of minced beef in 40°C and -15°C was examined. The aim was also to investigate the 3D printability of meat dried using ultrasound. CSIRO wants to explore the possibility to increase low value food by drying it, potentially using an ultrasound assisted dryer, and then increasing the foods value by printing the long shelf life dried food. This would economically desirable both by increasing the price of the food, but also generating less waste since the dried food keeps substantially longer due the low water activity. To determine the effect ultrasound has on the printability, the formulation and rheological properties of a printable paste needs to be determined. Once completed, the printability of the meat dried with and without ultrasound could be compared. The outcome of the work was that placing the sample on the transducer during drying at 40°C decreased the drying time by 40%. The decrease in drying time at -15°C could not be proved since the transducers cooling media was not flowing fast enough to cool it to -15°C. Viable methods and formulations for creating printable pastes using both xanthan gum and sodium alginate was established, however, the formulation will be affected by the minced beef used as a base in the paste. The meat dried at a colder temperature was more porous, and it was thus easier to reduce its particle size which is necessary for printing. The pastes created using meat dried at -15° also proved to have a slightly higher viscosity, is was thus determined that meat dried using colder temperatures was more favourable for printing. No difference was found in the beef dried with or without using ultrasound. Hence, implication of ultrasound during drying decreases the cost and the environmental impact, without affecting the product.Drying is one of the process steps that requires the most energy in many industries, one of these being the production of food. To dry food is one of the oldest ways of increasing the shelf life of food known to man and the process is still rather straightforward: blow hot air across the food to cause water to evaporate. The hot air though can cause a degradation in several aspects of the foods properties as consistency and flavor. Therefore, when a higher quality is desired, freeze drying is used. To increase the drying speed using freeze drying an expensive vacuum is often implemented. A new ultrasonic transducer on which a patent application has been filed by CSIRO is designed to potentially replace the vacuum during freeze drying, thus reducing the cost and energy required to freeze dry food. The ultrasound emitted from the ultrasonic transducer facilitates the waters movement through the food and thus increasing the drying rate. 3D printing technology has been around and implemented in several areas. The technology of 3D printing food has not come as far though, but it is currently being researched quite heavily. Several potential future uses are tested and developed. One being that consumers can keep track of their nutritional and caloric needs and print meals fitting one’s personal needs. Another closer usage would be drying low grade food, thus increasing its shelf life, and when desired print it into a higher value product. It was chosen that the drying kinetics of ground beef would be investigated. The effect the ultrasonic transducer had during air drying at 40°C and -15°C were investigated. The effect the ultrasound had on the product for 3D printing purposes was also investigated. It was found that at 40°C the ultrasound increased the drying rate by roughly 40%. A higher increase should according to literature be observed at -15°C, but due to problems in the set up some heating occurred in the sample and thus the precis effect the ultrasound had at -15°C was not proved in this study. After a viable method for creating a printable paste were formed, it was found that the addition of ultrasound not affected the meat for 3D printing purposes. This was established both by printing trials and measurements of the viscosity of the created pastes