Accelerated mild heating of dry-cured ham by applying power ultrasound in a liquid medium

Abstract

Mild thermal treatments could be considered a feasible technique with which to improve the texture of dry-cured ham. This study explores the feasibility of using power ultrasound (PuS) to intensify heat transfer during the mild thermal treatment of dry-cured ham immersed in a liquid medium. For that purpose, a temperature controlled ultrasonic bath was used to avoid the water temperature rise due to cavitation during ultrasonic application, which could mask the actual effect of ultrasound in heat transport mechanisms. Experiments were carried out using dry-cured ham slices (thickness 2 cm), which were heated at different temperatures (40, 45, 50 ºC) with (PuS) and without (conventional mechanical stirring, CV) ultrasonic assistance. Temperature was monitored in the two main muscles of the ham (Biceps femoris and Semimembranosus) and in different positions of the slice. A model that considered heat transfer entirely controlled by conduction was chosen for describing heating kinetics and quantify the influence of temperature and ultrasonic application in the apparent thermal diffusivity. The heat conduction model proposed was adequate to describe both CV and PuS heating kinetics (VAR >98.6%). Ultrasound application sped up the heat transfer by increasing the apparent thermal diffusivity up to 51%, but the higher the temperature, the lower the ultrasonic intensification. The apparent thermal diffusivities identified for the slices were satisfactorily validated (VAR> 98.4%) in independent experiments with ham cylinders. Therefore, PuS could be considered as an effective technology for the purposes of accelerating the heat transfer, thus shortening the heating time of dry-cured ham slices immersed in a liquid medium.

Correction of defective textures in packaged dry-cured pork ham by applying conventional and ultrasonically-assisted mild thermal treatments

“…Mild thermal treatments were carried out by placing packaged samples into a temperature controlled water bath following the same methodology already described by Contreras et al (2018a). Two different temperatures were tested (40 and 50 ºC) and the treatment time was 5 h in both cases.…”

“…Two different temperatures were tested (40 and 50 ºC) and the treatment time was 5 h in both cases. In conventional thermal treatments (CV), a mechanical stirrer was used to improve the liquid turbulence, while ultrasonically assisted treatments (PuS) were carried out in an ultrasonic bath (600 W, 20 kHz) supplied with a custom temperature control (Contreras et al, 2018a). Ultrasound was only applied during the heating phase, which represents the time needed to reach a temperature of 5 ºC below the temperature of the heating medium in the center of the slice.…”

“…Ultrasound was only applied during the heating phase, which represents the time needed to reach a temperature of 5 ºC below the temperature of the heating medium in the center of the slice. The duration of the heating phase was determined by the mathematical model proposed by Contreras et al (2018a) for dry-cured ham slices. Once the heating phase finished, the ultrasound generator was switched off and samples were held at the preset temperature until completing a total treatment time of 5 h. During this holding phase, the same mechanical stirrer as in CV experiments was used.…”

“…The feasibility of using mild temperatures, from 40 to ºC, and short treatment times has recently been explored in order to bring about texture modifications in dry-cured ham in both air (Contreras, Benedito, Bon, & Garcia-Perez, 2018a) and water medium (Contreras, Benedito, Bon, & Garcia-Perez, 2018b). The mild thermal treatment induced an increase in the sample hardness; thus, the higher the treatment temperature, the harder the ham.…”

“…The mild thermal treatment induced an increase in the sample hardness; thus, the higher the treatment temperature, the harder the ham. Contreras et al (2018a and2018b) used a small number of samples of commercial dry-cured hams without textural defects, since the main aim of both studies was to test the feasibility of power ultrasound (PuS) to accelerate the heating process (Lacivita et al, 2018;Sun et al, 2019). In addition, samples were heated only until they reached a target temperature defined as 5 ºC below the temperature of the heating medium.…”