Freeze microwave-assisted

Microwave-assisted (0.1 or 0.2 Wg-1) convection drying was also applied to osmotically dehydrated blueberries, leading to dried berries that were comparable to freeze-dried ones in much shorter time (Venkatachalapathy and Raghavan, 1998). Frozen blueberries were also dried in a microwave and spouted bed combined dryer (MWSB) after a pretreatment using ethyl oleate and a NaOH dipping solution followed by sucrose osmotic treatment (Feng et al., 1999). Osmotic dehydration prevented the blueberries from... 

In order to accelerate sample preparation, new extraction methodologies such as accelerated solvent extraction (ASE) and MAE, based on the use of elevated temperature and pressure to heat the mixture sample-solvent, have been recently developed and applied for PAH extraction from meat [695] and vegetables [696-698]. Garda Falcon et al. [699] used microwave treatment with hexane to accelerate PAH extraction from freeze-dried foods. The fat extracted in this way underwent microwave assisted saponification with ethanolic KOH. Hernandez-Borges et al. [700] combined microwave-assisted hydrolysis and extraction to isolate organic pollutants from mussels, while... 

J. Kirby, W. A. Maher, Measurement of water-soluble arsenic species in freeze-dried marine animal tissues by microwave-assisted extraction and HPLC-ICP-MS, J. Anal. Atom. Spectrom., 17 (2002), 838-843. 

Heavy metals, boron (B(V)), arsenic and total phosphorus were determined in the fraction < 20 pm to improve the comparability of the results. This fraction was separated from the freeze-dried and non-milled samples by ultrasonic sieving (Ackermann 1980). Metals were analysed after microwave-assisted digestion with aqua regia at 180 °C in closed vessels by inductively coupled plasma optical emission spectroscopy, atomic fluorescence spectroscopy (mercury) and hydride atomic absorption spectroscopy (arsenic). 

Microwave-assisted atmospheric freeze drying of green peas A case study. Drying Technd. 30(14) 1592-1599. 

Fig. 9.9 Laboratory-scale microwave-assisted freeze-drying equipment. 1, MWFD chamber 2, Fiber-optical temperature sensor 3, Vacuum breakage valve, for MWFD 4, Sample supporting plate ...

A typical schematic diagram of microwave-assisted freeze-drying equipment is shown in Fig. 9.9. During drying, the pressure was maintained at 100 Pa by a vacuum pump, and the temperature of the cold trap (—40 to —45 °C) was sufficiently low to condense the vapor. The microwave frequency was 2450 MHz and the power could be regulated continually from 0 to 2000 W. 

Figure 9.14 presents typical temperature curves of microwave-assisted drying for food. Here, the shape of the temperature curve of microwave-assisted freeze-drying can be seen to differ from that of the three other types of microwave-assisted drying, due to different drying mechanisms. Temperature changes are heavily dependent on the microwave power, microwave emission mode, type of dryer used, and the presence or absence of a temperature control unit. 

R., 2010a. Trends in microwave-assisted freeze drying of foods. Drying Technol. 28 1-10. 

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