Investigation of the low-temperature exposure effect on the water activity of food products

Introduction: The activity of water is an integral characteristic of the moisture condition in a product, by which one can assess the correctness of various technological processes, as well as predict the shelf life of the product. Existing studies on the activity of water in food products were conducted mostly for the positive temperature range. Little attention was paid to the study of the effects of low-temperature exposure on water activity.

Purpose: The article is devoted to the study of water activity in food products at various temperatures. Such an approach will allow predicting the shelf life of food products and optimizing the development of methods for controlling the functional and technological characteristics of food raw materials.

Materials and Methods: The objects of research were: beef chilled according to GOST R 52427-2005, chilled pork, chilled mutton, fresh cucumbers, fresh carrots, fresh tomatoes, fresh parsley greens, dill greens, green onion greens. Two installations were used to analyze the water activity in the research objects: designed at the Kuzbass State Agricultural Academy, and the LabSwift-aw water activity analyzer. Experiments were conducted for fresh, chilled, and frozen products at various temperatures.

Results: A design of a homemade installation that can be used to measure water activity is presented. The accuracy of this installation's measurements is experimentally proven. An analysis of water activity in fresh, chilled, and frozen products has been conducted. The water activity of fresh products was within the range of 0.954-0.995. It was found that with the same moisture content, the water activity can vary slightly, which is due to the difference in the chemical composition of the product and the salt content. It was established that chilling products from 22 to 6°C leads to a decrease in water activity by an average of 2%. Freezing to a temperature of -5°C results in a further reduction of water activity by an average of 0.03 units. Lowering the freezing temperature from -5°C to -10°C, -20°C, -30°C, and -40°C results in a reduction of water activity by an average of 0.04, 0.07, 0.06, and 0.05 units, respectively. Based on experimental data, mathematical dependencies of water activity on the freezing temperature for all studied products were derived.

Conclusion: Water activity has important theoretical and practical significance, and the results of the research can be useful in predicting the shelf life of food products and developing methods to control the functional and technological characteristics of food raw materials.

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