Speaker
Description
Frozen foods are a sustainable, cost-effective, and convenient source of food with a global industry worth over USD 300 billion. Freezing food extends self-life, but the growth of large ice crystals can damage the food, impacting texture and taste. The process of freezing consists of two distinct phases: ice nucleation, the formation of an ice nucleus initiating freezing, and ice growth, the propagation of ice from the ice nucleus throughout the sample. Within the frozen food industry, faster freezing methods are generally preferred on the basis that the size of the ice crystals will be limited. However, data supporting this methodology has largely focused on indirect measurements such as food quality after freezing as opposed to the study of the ice itself. Additionally, faster cooling rates and methods can be more energy-inefficient and costly, requiring specialized materials such as liquid nitrogen.
Quantitative measurements of ice formation in whole-food samples are limited, in large part, by the difficulty of study in a complex matrix. This has left large gaps in the knowledge of ice nucleation and ice growth rates in foods, limiting the optimization of efficient freezing processes while preserving food quality. Typical methods for the study of ice nucleation and growth require the target material be in water or other transparent media to allow for appropriate visualization of the ice. We have employed high resolution infrared microthermography for the study of ice behavior in opaque samples, with beef being the primary target of study. The release of latent heat during freezing makes infrared thermography a suitable method for the study of the freezing process as the whole ice crystal can be visualized within the sample. We have studied the nucleation rate of ice in supercooled samples and the growth velocity of ice crystals in beef across a range of temperatures. These studies allow for the correlation of ice growth velocity across the variable structures present in a whole meat sample (e.g. connective tissues, muscle tissue, and fat) as well as nucleation rates of ice within these various structures. Results from these studies will inform improved freezing strategies in industrial settings and support future studies of controlled freezing with interventions including ice nucleating agents and antifreeze proteins.
