Central vacuum cooling plant
Described is a method as well as an apparatus for vacuum cooling of food produce through moisture removal, which method comprising the steps of loading the food produce to be cooled into a vacuum chamber, lowering the pressure inside the vacuum chamber to a predetermined pressure level and maintaining the vacuum chamber at this predetermined pressure level both by removing air through a vacuum pump system for a sufficient of time to allow heat transfer out of the food produce to take place, and condensing water vapor inside the vacuum chamber through a refrigeration system. The method and apparatus is unique in that the step of lowering the pressure inside the vacuum chamber to the predetermined pressure level is carried out using a single stage vacuum pump and the step of maintaining the vacuum chamber at this predetermined pressure level is carried out using a two stage vacuum pump.
1. An apparatus for vacuum cooling of food produce through moisture removal comprising at least one vacuum chamber for containing the food produce to be cooled, a vacuum pump system for, by removing air from the vacuum chamber, lowering the pressure inside the at least one vacuum chamber to a predetermined final pressure level and maintaining the at least one vacuum chamber at this predetermined final pressure level for a sufficient of time to allow heat transfer out of the food produce to take place, wherein the vacuum pump system comprises (i) at least one single stage intermediate pressure vacuum pump for lowering the pressure from atmospheric pressure to a intermediate preselected pressure value, (ii) at least one final pressure vacuum pump for the pressure lowering from the intermediate preselected pressure value to the predetermined final pressure level, and (iii) at least one pressure maintaining vacuum pump to maintain the at least one vacuum chamber at the predetermined final pressure level for a preselected time period.
2. An apparatus for vacuum cooling of food produce through moisture removal as claimed in claim 1 , wherein the vacuum pump system comprises more than one single stage vacuum pumps and/or two stage vacuum pumps for lowering the pressure inside the at least one vacuum chamber to the final pressure level, where each of the vacuum pumps is especially designed for optimum operation within each of their working range.
3. An apparatus for vacuum cooling of food produce through moisture removal as claimed in claim 1 , wherein the apparatus for vacuum cooling of food produce through moisture removal comprises a plurality of vacuum chambers, which are operated simultaneously in any combination.
4. An apparatus for vacuum cooling of food produce through moisture removal as claimed in claim 1 , wherein the apparatus for vacuum cooling of food produce through moisture removal comprises variable speed drives for driving the vacuum pumps at variable speed.
5. An apparatus for vacuum cooling of food produce through moisture removal as claimed in claim 4 , wherein the apparatus for vacuum cooling of food produce through moisture removal comprises means for temporally disconnecting each vacuum pump from its drive.
6. An apparatus for vacuum cooling of food produce through moisture removal as claimed in claim 3 , wherein the plurality of vacuum chambers comprises a first set of vacuum chambers and a second set of vacuum chambers, each set of vacuum chambers containing one or two vacuum chambers, and wherein the apparatus further comprises
(i) means for disconnecting the intermediate pressure vacuum pump from the first set of vacuum chambers after the pressure in the first set of vacuum chambers has reached the preselected intermediate pressure; and
(ii) means for connecting the intermediate pressure vacuum pump to the second set of vacuum chambers to commence lowering the pressure in the second set of vacuum chambers from atmospheric pressure to the preselected intermediate pressure at approximately the same time that the final pressure vacuum pump commences lowering the pressure in the first set of vacuum chambers from the preselected intermediate pressure to the preselected final pressure.
7. An apparatus for vacuum cooling of food produce through moisture removal as claimed in claim 6 , further comprising
(iii) means for disconnecting the final pressure vacuum pump from the first set of vacuum chambers after the pressure in the first set of vacuum chambers has reached the preselected final pressure; and
(iv) means for connecting the final pressure vacuum pump to the second set of vacuum chambers to commence lowering the pressure in the second set of vacuum chambers from the preselected intermediate pressure to the preselected final pressure at approximately the same time that the pressure maintaining vacuum pump commences maintaining the pressure in the first set of vacuum chamber at the predetermined final pressure level.
8. An apparatus for vacuum cooling of food produce through moisture removal as claimed in claim 7 , further comprising
(v) means for disconnecting the pressure maintaining vacuum pump from the first set of vacuum chambers after the pressure in the first set of vacuum chambers has been maintained at the preselected final pressure for a preselected time period; and
(iv) means for connecting the pressure maintaining vacuum pump to the second set of vacuum chambers to commence maintaining the pressure in the second set of vacuum chamber at the predetermined final pressure level.