Emerging Food Processing Technologies

Abstract

Heat treatment is commonly used to inactivate microorganisms and produce shelf-stable foods. These processes, when properly designed and operated, can ensure a high level of food safety. However, these processes often involve high-temperature long-time heating that causes deteriorations in food quality such as degradations in color, texture, and flavor and loss of vitamins and antioxidant capacities. Considerable effort has been made to develop new technologies that are able to effectively inactivate microbial while reducing the negative impact on quality attributes. A number of different processes have been studied extensively as alternatives to the conventional thermal processing. These methods can be categorized into thermal and nonthermal processing technologies, depending on their mechanism of the microbial inactivation. In this chapter, some of these emerging technologies are covered including thermal processing (microwave and radio-frequency heating) and nonthermal processing methods (high-pressure and pulsed electric field processing). The fundamentals of these technologies, some technical aspects, and research and application status are briefly introduced.

Problems

• 15.1. Meat balls in tomato sauce are heated in a microwave. Dielectric loss factor, density, and specific heat capacity of meat ball and tomato sauce are 16.75 and 48.2, 1108 and 1022 kg/m³, and 3.35 and 3.68 kJ/kg K, respectively. When tomato sauce reaches 60 °C from 20 °C, what will be the temperature of the meatballs? Are there any ways you can use to increase heating uniformity?

• 15.2. A slice of smoked bacon with 100-g weight is being heated in a 2450-MHz microwave with a rated output of 800 W. Dielectric constant and loss factor are 31.1 and 10.3, respectively. Density is 1004 kg/m³ and specific heat 2.7 kJ/kg K. The temperature rises to 60 °C from 4 °C in 30 min. Assume it is heated at the rate determined by the power output of the oven; calculate the electric field strength inside the oven.

• 15.3. A company has developed a new microwave-ready product in 24-oz tray with mashed potato as the major component. The dielectric constant and loss factor are measured to be 55.5 and 16.1, respectively. What is the maximum thickness of the tray you recommend?

• 15.4. Inactivation kinetics for L. innocua at 330 atm, 20 °C follows the linear equation. Log n = 7.171–0.155 t

  Calculate the D value at this condition.

• 15.5. HHP is used to inactivate orange pectin methylesterase (PME). At 18 °C, inactivation rate constants of PME are 0.024, 0.107, and 0.478 min⁻¹, at 400, 500, and 600 MPa, respectively, taking atmospheric pressure as reference. Assuming the inactivation follows a first-order model, what is the activation volume for PME in the experiment condition?

• 15.6. Z value model is used to describe the sensitivity of microbial to pressure inactivation. During HHP treatment of orange juice at constant temperature 25 °C, S. cerevisiae ascospores showed D values at different pressure, which are 0.18, 0.97, and 5.23 min for 500, 400, and 300 MPa, respectively. What is z_p value of S. cerevisiae at 25 °C?

• 15.7. Orange juice is treated by PEF processing. A voltage of 40 kV is applied to the treatment chamber with a gap of 15 mm. Calculate the electric field in the treatment chamber.

• 15.8. During PEF treatment of apple juice, a voltage of 50 kV is applied in square wave to a treatment chamber with volume of 0.95 L, gap of 10 mm, and surface area of 25 cm². If resistance of the treatment chamber, pulse duration, and the number of pulses are 50 Ω, 20 μs, and 6, respectively, the electrical conductivity of the apple juice is 0.2200 S m⁻¹ at the processing temperature. Calculate the temperature increase in the product.