Cider apple pomace as a source of nutrients: Evaluation of the polyphenolic profile, antioxidant and fiber properties after drying process at different temperatures.

Apple pomace, the by-product of the cider industry, contains a high content of antioxidant compounds and dietary fiber. Drying would allow its preservation for a later use. The aim of this study was to evaluate the effect of the drying temperature on the drying kinetics, antioxidant properties and the fiber characteristics. For this, drying experiments were performed at different temperatures (40-120 °C). The increase in temperature enhanced the drying rate, as was shown by the effective diffusivity and mass transfer coefficient identified by modelling. The influence of temperature was quantified through the activation energy (38.21 kJ/mol). Regarding the retention of antioxidant properties, the best results were found at 80-100 °C while 40-60 °C was the best temperature range for the fiber characteristics. Therefore, 80 °C could be an adequate temperature for drying of cider apple pomace, as it represents a good balance between kinetics, and antioxidant and fiber properties.

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.

High intensity ultrasound effects on meat brining.

Pork loin (longissimus dorsi) samples of two different geometries, cylinders and slabs, were immersed in saturated NaCl brine for 45min under different conditions: without brine agitation (STAT), with brine agitation (AG) and with ultrasound application (US) at eight levels of ultrasonic intensity. Moisture content change and NaCl gain were considered in order to evaluate the difference in the brining treatments. No significant differences were found in moisture and NaCl content of samples treated under STAT conditions and AG conditions, while the influence of ultrasound on the mass transfer process during meat brining depended on the intensity applied. There was an ultrasonic intensity threshold above which the influence of ultrasound appeared. At the highest level of intensity studied, the water content of samples was significantly higher than the initial water content of meat. As regards NaCl transfer, once above the intensity threshold, the increase in the NaCl content was proportional to the applied ultrasonic intensity. Not statistically significant differences were found for sample geometry.

Ultrasonic drying of foodstuff in a fluidized bed: Parametric study.

The application of high power ultrasound for dehydration of porous materials may be very effective in processes in which heat-sensitive materials such as foodstuffs have to be treated. In fact, high-intensity ultrasonic vibrations are capable of increasing heat and mass transfer processes in materials. The application of ultrasonic energy can be made alone or in combination with other kind of energy such as hot-air. In this case, ultrasound helps in reducing temperature or treatment time. The aim of this work is to study the effect of air flow rate, ultrasonic power and mass loading on hot-air drying assisted by a new power ultrasonic system. The drying chamber is an aluminium vibrating cylinder, which is able to create a high intensity ultrasonic field in the gas medium. To that purpose the chamber is driven at its centre by a power ultrasonic vibrator at 21.8 kHz. Drying kinetics of carrot cubes and lemon peel cylinders were carried out at 40 degrees C for different air velocities, with and without ultrasound. The results show that the effect of ultrasound on drying rate is affected by air flow rate, ultrasonic power and mass loading. In fact, at high air velocities the acoustic field inside the chamber is disturbed and the effect of ultrasound on drying kinetics diminishes.

Application of low intensity ultrasonics to cheese manufacturing processes.

Ultrasound has been used to non-destructively assess the quality of many foods such as meat, fish, vegetables and dairy products. This paper addresses the applications of low intensity ultrasonics in the cheese manufacturing processes and highlights the areas where ultrasonics could be successfully implemented in the future. The decrease of ultrasonic attenuation during the renneting process can be used to determine the optimum cut time for cheese making. The ultrasonic velocity increases during maturation for those types of cheese that become harder during this manufacturing stage, thus being an indicator of the maturity degree. Moreover, ultrasonic measurements could be linked to sensory parameters. From the ultrasonic velocity measurements at two different temperatures, it is possible to assess cheese composition, thus allowing an improvement in the quality and uniformity of cheese commercialization. In addition, in pulse-echo mode it is possible to detect cracked pieces due to abnormal fermentations and also to assess the distance of the crack from the surface.

Composition assessment of raw meat mixtures using ultrasonics.

The use of ultrasonic velocity measurements to determine the composition of dry fermented sausages was assessed. Mixtures of ground lean and fatty tissues were prepared to cover a wide range of fat (2-90 wt.%), moisture (7-76 wt.%), and protein (2-21 wt.%) contents. The ultrasonic velocity in fat decreased on average 5.6 ms(-1) per °C increase in temperature, due to the negative temperature coefficient for fat and the fat melting, which is observed in (DSC) differential scanning calorimetry analysis. The ultrasonic velocity temperature dependence allowed the determining of the fat, moisture and protein+others content, by measuring the ultrasonic velocity in the mixtures at 4 and 25°C and using a semi-empirical equation. The explained variance was 99.6% for fat, 98.7% for moisture and 85.4% for protein+others. The results obtained show the feasibility of using ultrasonic velocity measurement to assess the composition of meat products such as dry fermented sausages, rapidly and non-destructively.

Use of ultrasound to assess Cheddar cheese characteristics.

Blocks of Cheddar cheese were matured in temperature-controlled chambers at 5 and 12 degrees C. The ultrasonic velocity increased during maturation ranging from 1657 to 1677 ms-1 at 12 degrees C and from 1684 to 1693 ms-1 at 5 degrees C. The ultrasonic velocity was related to the square root of the deformability modulus and the slope in puncture. The increase of velocity during maturation shows the feasibility of using an ultrasonic device to non-destructively monitor Cheddar cheese maturity. Ultrasound velocity was measured at different temperatures. The velocity decreased with increasing temperature, and from the slope of the first part of the temperature-velocity curves it was possible to non-destructively assess the moisture content of different types of cheese.