Heat penetration and quality analysis of retort processed vegetables for home meal replacement foods

Heat penetration characteristics of different vegetable products were investigated during retort processing. A custom-developed variable temperature retort-sterilizer allowed us to test the following target retort-temperatures; 120, 130, 140, and 150 °C, combined with the following holding times: 1, 3, 5, 7 min. Radish showed the highest heating rate (9.56 ± 0.21 °C/min) among the tested vegetables, including radish, carrot, and potato. Textural qualities of retort-processed vegetables showed a close correlation with thermal dose. Hardness of potato was 3.07 ± 0.07 N after retort processing at 120 °C for 7 min, with a thermal dose of 127 ± 7 k °C s. Better hardness (3.72 ± 0.06 N) was obtained after retort processing at 150 °C for 3 min, with a thermal dose of 122 ± 6 k °C s. The data reported herein indicate that retort temperature should be appropriately controlled for different vegetable products based on their specific heat-penetration characteristics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01247-8.

Effect of changes in salt content and food thickness on electromagnetic heating of rice, mashed potatoes and peas in 915 MHz single mode microwave cavity

A mathematical model for predicting electromagnetic power dissipation within a rectangular dielectric slab heated by equal intensity 915 MHz plane waves from top and bottom was developed. A dimensionless parameter (J-T number) which is a combination of the loss factor (εr″), dielectric constant (εr') and food thickness (L) was proposed. This unique number provided direct insight into the relationship between food dielectric properties, thickness, product temperature, and thermal lethality. For the validation tests, mashed potatoes, peas and rice samples with 0-2% salt content were processed in a pilot scale microwave assisted thermal sterilization (MATS) system. In each food, the combination of dielectric properties and thickness which gave J-T number of 1.8-2.2 at 100-121°C, provided the highest lethalities. MATS is a novel commercial technology being adapted in the food industry. A qualitative assessment of the combined effect of food properties on lethalities using this model will be helpful in process development for MATS systems.

Selective laser broiling of Atlantic salmon

Selective laser broiling is a novel food processing technique that utilizes a 2-axis mirror galvanometer system to direct laser power to cook raw food. Unlike conventional cooking processes, laser cooking benefits from the high spatial and temporal precision of power delivery. In this investigation, we use a trochoidal scanning pattern to optimize the cooking of Atlantic salmon (Salmo salar), which is used as a model food system. We vary geometry of the trochoidal cooking pattern (circle diameter, circle density, and period) as well as the heat flux (2.71 MW/m² and 0.73 MW/m²) and power (2 W and 5 W) of the blue laser and measure the internal temperature and depth of heat penetration via color analysis. Heat generated by blue laser operating at 445 nm has a thermal penetration depth nearing 2 mm in salmon and provide sufficient protein denaturation for cooking thin food layers. We achieve food safe cooking temperatures (>62.8 °C) in the salmon fillets and desirable color and textural changes through the use of high speeds and repetitive exposure. Ultimately, the goal of this study is to explore laser cooking of meat with an eye to applications both in food printing as well as an augmentation of conventional oven cooking.

Heat Penetration Rates of Natural Convection Heating Liquids in Metal Containers

Heat penetration (HP) test data have been obtained for water in 13 sizes of metal cans and for 16 fluids with different physical properties in 211 × 400 metal cans. Data were collected until the slowest heating zone was less than 0.1 C° below the heating medium temperature. When conventional HP graphs were plotted, these natural convection heating liquids formed curves instead of straight lines. A straight line was fitted by least squares regression to the data between (T₁ - T) values from 40.0 to 4.0, 10.0 to 1.0, 4.0 to 0.4, and 1.0 to 0.2 C° and the f-values determined. The results show that the f-value of fluids that heat by convection increase with heating time, indicating that the true shape of the heat penetration data on a semilogarithmic graph is a curve.

Heat Penetration Rates of Natural Convection Heating Liquids in Metal Containers

Heat penetration (HP) test data have been obtained for water in 13 sizes of metal cans and for 16 fluids with different physical properties in 211 × 400 metal cans. Data were collected until the slowest heating zone was less than 0.1 C° below the heating medium temperature. When conventional HP graphs were plotted, these natural convection heating liquids formed curves instead of straight lines. A straight line was fitted by least squares regression to the data between (T₁ - T) values from 40.0 to 4.0, 10.0 to 1.0, 4.0 to 0.4, and 1.0 to 0.2 C° and the f-values determined. The results show that the f-value of fluids that heat by convection increase with heating time, indicating that the true shape of the heat penetration data on a semilogarithmic graph is a curve.