Ultrasound intensification of Ferrochelatase extraction from pork liver as a strategy to improve ZINC-protoporphyrin formation

The enzyme Ferrochelatase (FeCH), which is naturally present in pork liver, catalyses the formation of Zinc-protoporphyrin (ZnPP), a natural pigment responsible for the typical color of dry-cured Italian Parma ham. The aim of this study was to evaluate the feasibility of using high power ultrasound in continuous and pulsed modes to intensify the extraction of the enzyme FeCH from pork liver. US application during FeCH extraction led to an improved enzymatic activity and further increase in the formation of ZnPP. The optimal condition tested was that of 1 min in continuous US application, in which time the enzymatic activity increased by 33.3 % compared to conventional extraction (30 min). Pulsed US application required 5 min treatments to observe a significant intensification effect. Therefore, ultrasound is a potentially feasible technique as it increases the catalytic activity of FeCH and saves time compared to the conventional extraction method.

Ultrasonic characterization of salt, moisture and texture modifications in dry-cured ham during post-salting

For the first time, this study addresses the use of non-destructive ultrasound to monitor ham post-salting. For that purpose, the ultrasonic velocity (1 MHz) and the weight loss of hams were measured regularly every 2 days up to 8 weeks after salting. Additionally, for different post-salting times, internal salt and moisture content and hardness were measured at different locations from the ham surface. The experimental results reflected that the ultrasonic velocity increased as the ham weight decreased (26.1 m/s per kg), showing a satisfactory correlation between both variables (r = 0.95). The ultrasonic velocity was also correlated with the salt and moisture content. However, ham hardness remained fairly constant during post-salting, which confirmed that characteristic textural changes mainly occur during the salting and drying-maturation stages. Thus, the ultrasonic velocity could be a reliable parameter with which to monitor not only overall modifications in ham weight, but also internal changes of moisture and salt content during post-salting in a non-destructive way.

Proteomic footprint of ultrasound intensification on sliced dry-cured ham subjected to mild thermal conditions

Ultrasound can intensify the heating process used to correct texture defects in dry-cured hams. The effect of ultrasound-assisted heating on the proteome of sliced dry-cured ham was evaluated. Dry-cured hams with high proteolysis index (PI > 36) were sliced, vacuum packed and subjected to conventional (CV) and ultrasound-assisted (US) thermal treatments. Comparative proteome profiling between sample groups was assessed by two-dimensional electrophoresis (2-DE) coupled to tandem mass spectrometry. It was found that protein fragmentation increased markedly after US thermal treatment. Specifically, fragments of the major myofibrillar protein, actin, were abundantly over-represented following US heating. In addition, five unfragmented sarcoplasmic proteins (i.e. fatty acid-binding protein, peroxiredoxin-6, superoxide dismutase, carbonyl reductase and aminoacylase) showed increased abundance in the US sample group. These results suggest candidate biomarkers to monitor proteolysis intensity and proteolysis-independent effects linked to cured ham quality by ultrasound application. SIGNIFICANCE: The present proteome profiling study of treated dry-cured ham demonstrates the impact of ultrasound action on proteins. Moreover, negative organoleptic effects can be appearing with ultrasound treatment due to proteolysis increase. Therefore, the proteolysis monitoring could help to control these effects. In this regards, our results suggest that actin can be a candidate biomarker to monitor proteolysis intensity.

Intensification of heat transfer during mild thermal treatment of dry-cured ham by using airborne ultrasound

The application of power ultrasound (PuS) could be used as a novel technology with which to intensify thermal treatments using hot air. Mild thermal treatments have been applied to improve the soft texture of dry-cured ham caused by defective processing. In this regard, the aim of this study was to assess the kinetic intensification linked to the application of airborne PuS in the mild thermal treatment using hot air of dry-cured ham. For this purpose, vacuum packed cylindrical samples (2.52±0.11cm in diameter and 1.90±0.14cm in height) of dry-cured ham were heated using hot air at different temperatures (40, 45, 50°C) and air velocities (1, 2, 3, 4, 6m/s) with (22.3kHz, 50W) and without PuS application. Heat transfer was analyzed by considering that it was entirely controlled by conduction and the apparent thermal diffusivity was identified by fitting the model to the heating kinetics. The obtained results revealed that PuS application sped up the heat transfer, showing an increase in the apparent thermal diffusivity (up to 37%). The improvement in the apparent thermal diffusivity produced by PuS application was greater at high temperatures (50°C) but negligible at high air velocities (6m/s). Heating caused an increase in the hardness and elasticity of dry-cured ham, which would correct ham pastiness defects, while the influence of PuS on such textural parameters was negligible.

Impact of applied ultrasonic power on the low temperature drying of apple

Low temperature drying (LTD) allows high-quality dried products to be obtained, preserving the nutritional properties of fresh foods better than conventional drying, but it is a time-consuming operation. Power ultrasound (US) could be used to intensify LTD, but it should be taken into account that process variables, such as the level of applied power, have an influence on the magnitude and extension of the ultrasonic effects. Therefore, the aim of this work was to assess the influence of the level of applied ultrasonic power on the LTD of apple, analyzing the drying kinetics and the quality of the dried product. For that purpose, apple (Malus domestica cv. Granny Smith) cubes (8.8mm side) were dried (2m/s) at two different temperatures (10 and -10°C), without and with (25, 50 and 75 W) US application. In the dried apple, the rehydration kinetics, hardness, total phenolic content, antioxidant capacity and microstructure were analyzed to evaluate the impact of the level of applied ultrasonic power. At both temperatures, 10 and -10°C, the higher the ultrasonic power level, the shorter the drying time; the maximum shortening of the drying time achieved was 80.3% (at -10°C and 75 W). The ultrasonic power level did not significantly (p<0.05) affect the quality parameters analyzed. Therefore, US could be considered a non-thermal method of intensifying the LTD of fruits, like apple, with only a mild impact on the quality of the dried product.