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Shredded cabbage (50 % v/v) and Daikon radish cubes (57 % v/v) with different salt concentrations (0.15, 0.5, 1, 1.5, and 1.85 %) were heated from 30 to 70 °C in a static ohmic heating cell at different voltages (65, 80, 100, 120, and 135 V) and frequencies (60, 2070, 5030, 7990, and 10,000 Hz) to evaluate their ohmic heating behaviour. Radish heated under 1.5 % salt, 120 V and 7990 Hz or 1 % salt, 135 V and 5030 Hz conditions gave the shortest heating time of 6 min from 30 to 70 °C, and cabbage gave the longest time of 128 min at 0.15 % salt, 100 V, and 5030 Hz. Regression models of heating rate as a quadratic function of the sample temperature gave R2 >0.98. The general trend observed was that the magnitude of the heating rate increased with frequency at high voltage but decreased at low voltage for cabbage, while the opposite trend was observed for radish. Heating was more efficient at higher salt concentration and applied voltage. Radish heated more rapidly than cabbage. A slight slope change was observed in all cases between 50 and 60 °C. The response surface models revealed linear, cross products and quadratic effects to be significant with R 2 over 0.98.

Hurdle technology combining mild acidification (4.6 < pH < 5.0) and reduced thermal treatment could be a potential preservation technique for the production of high-quality processed canned vegetables once it has been microbiologically validated. Freshly harvested green beans were acidified in pre-prepared brine using one of three acidulants (lactic acid [LA], glucono-delta-lactone [GDL], or fermented dextrose containing organic acids), hermetically sealed in cans, and thermally processed in a pilot-scale water-immersion retort. Eight levels of acidulant concentration (0.01–19.5 g/kg) and five levels of desired lethality (0.01–2.74 min) were applied through uniform shell experimental design (Doehlert network method). The color and texture properties of blanched green beans (control samples) and thermally processed green beans with and without prior acidification were evaluated. Statistical analysis showed that acid concentration had a significant effect on color characteristics, and that lethality had a s...

The electrical conductivity (EC) of food systems is a key parameter of the ohmic heating process. Ohmic heating experiments were conducted using a Teflon cylindrical cell. Electrical conductivity values were evaluated for the ohmic processing (25–125 °C) of blanched, 2-cm cubic particles (carrot, potato, radish, beef muscle, pork muscle and commercial ham) dispersed in carrier fluid (5% w/w starch–water solution with 0.15–1.5% w/w salt concentrations). Assuming an analogy between thermal conductivity (TC) and EC five existing TC theoretical models (series, parallel, two forms of Maxwell–Eucken models and effective medium theory) were applied and evaluated for EC of various solid–fluid structural systems. Parallel and Series models are not practically applicable in real food system, however they can indicate the useful limit values of highest and lowest EC among all two-phase structures. The first Maxwell–Eucken model, which describes solid particles dispersed in continuous liquid, showed the best agreement between predicted EC values and experimental data. This model provided a useful and relatively simple new approach to predict the effective EC for mixtures of different types of solid food particles immersed in liquid food.

Traditional cooking-cooling of processed meat and poultry products is industrially carried out in smokehouses or autoclaves. A mathematical model was developed to simulate these operations. Equations, describing heat transfer and thermal destruction of micro-organisms and quality characteristics, were solved numerically. The model was validated experimentally for heat transfer and energy consumption and was used to perform a sensitivity analysis. Input variables were: process time (PT), smokehouse temperature (T SH ), bologna size (diameter, D and height, H), surface heat transfer coefficients (h heat and h cool ), product thermal diffusivity (α heat and α cool ). Output variables were: product core temperature (T c ), core and volume-average lethality (P cm and P vm ) and cook (C c and C v ) values as well as surface (Q s ) and volume-average (Q v ) quality retention, total specific energy consumption (En) and energy efficiency (Ce). Multiple linear regression models were developed to predict C c and C v from five inputs and used to obtain acceptable deviation ranges.

Blueberries and cranberries were dried using a hybrid technology consisting of pretreatment, osmotic dehydration, and convective drying. The performance of this hybrid technology was evaluated in terms of quality attributes such as color, taste, rehydration ratio, water activity, as well as sugar and anthocyanins content. Of thirteen different pretreatment methods tested for cranberries, cutting the berries in halves was the simplest and the best one. No pretreatment was needed for blueberries. Osmotic dehydration was performed in batch and continuous modes using sugar solution of 67.5–70°Brix. Convective drying was then carried out in a fluidized bed, a pulsed fluidized bed, or a vibrated fluidized bed. Quality profiles for both berries were determined after each step of such a hybrid technology and compared with quality of berries dried in the vibrated fluidized bed and freeze dryer. Recommendations for full-scale processing are given.

Foods acidified to pH levels below 4.5 can be thermally treated at lower temperatures under pasteurization conditions offering reduced thermal damage to product quality. Considering practical criterion, the main objective of this study was to investigate the proper acidification procedures of solid food particles immersed in liquid solutions. This was performed by testing a variety of factors, including particle type and size, temperature, and type and concentration of acids. Furthermore, the minimum acidification time of food particles was also determined. A standard model for mass transfer (e.g. Fick’s second law) was applied. Mass diffusion coefficients (DAB) were calculated based on experimental data. Average values of DAB were in the range of 10-8 to 10-10 m2/s and in agreement with existing literature data. Minimum acidification times varied depending on the type of acid, food, and treatment temperature, and ranged between 7 to 26 min. Meat particles were slowest to acidify, and acetic acid and tomato juice acidified by citric acid were the strongest acidifying agents.

Combined effects of mild temperatures, acidification and nisin on the thermal resistance of Clostridium sporogenes ATCC 11437 spores were assessed. Inoculated carrot-alginate particles were used as a solid-food model for the validation of the spore inactivation during the flow of a solid-liquid food system through the holding tube of an aseptic processing unit. Inactivation kinetics was studied in a water bath with the spores inoculated into carrot-alginate particles and in Sorensen's phosphate buffer. For temperatures of 70-90 degrees C, D-values in the buffer were 24.9-5.7 min, much lower than those evaluated for the particles (115.1-22.2 min). Statistical analyses showed significant synergistic effects of temperature and pH on spore inactivation for both media. Acidification reduced the heat resistance of the spores by reducing the D-values. Nisin was not significantly effective at the lower concentrations (up to 750 IU/g). The combination of 90 degrees C, pH: 4.5 and 500IU/g nisin resulted in a ten-fold decrease of the D-value for spores inoculated in the particles (from 111.1 to 10.6 min). Microbial validation tests were conducted using a pilot-scale aseptic processing unit with a mixture of carrot cubes (10%) and carrier liquid of 2%-carboxymethylcellulose solution (90%). Spore-inoculated carrot-alginate particles (initial counts of 106 CFU/g, obtained after come-up-time pre-heat) with pH 3.5 and 2000 IU/g nisin were processed at 90 degrees C in the aseptic processing unit. Microbial analysis showed no spore survivors in the particles after passing through the holding tube (5.2-6.0 min of residence time). The proposed combination of these hurdles significantly enhanced the spore inactivation rate (D(90)=1.17 min) as compared to that for thermal treatment only (D(90)=19.6 min).

Shredded cabbage (50% v/v) and Daikon radish cubes (57% v/v) were mixed with different salt solutions (0.15, 0.5, 1, 1.5 and 1.85%), poured into a Teflon-coated static Ohmic cell and heated from 30 to 70°C at different alternating current voltages (65, 80, 100, 120 or 135 V) and frequencies (60, 2,070, 5,030, 7,990 or 10,000 Hz). Voltage, current, time and temperature were measured to calculate electrical conductivities at different temperatures. For the modeling part, 750 g of a blended crude puree (particle size 0.98. The Maxwell–Eucken model, which describes solid particles dispersed in continuous liquid, showed good fit for the electrical conductivity data. Practical Applications Ohmic heating can be an alternative to conventional heat processing of food, reducing treatment time and improving quality. Ohmic heating has been generally recognized to provide uniform and rapid heating conditions. The electrical conductivity (EC) of food components is the key property in the Ohmic heating process and is dependent on many product and system-dependent properties, especially the salt content. It is also the primary property needed for modeling the Ohmic heating effects of a system or product. This manuscript details the gathered data on electrical conductivity of cabbage and radish, and an appropriate modeling approach to describe their dependence on product and system properties. The study generates new data EC for the vegetables and how the EC is influenced by the two vegetables that differ significantly in structure.