Process and plant for maturing meat products, in partular pork products such as ham, coppa, salami, bacon, sausage and the like

Abstract: According to the invention, the product is left in a substantially sealed environment at less than atmospheric pressure, heat being supplied to the product to compensate the heat lost by evaporation of its intrinsic water and to maintain its temperature within a predetermined range of values.

Description: This invention relates to the maturing of meat products, in particular pork products, such as ham, "coppa", bacon, sausage and the like. It has been known from prehistoric times to preserve meat by subjecting it (possibly after salting and/or flavouring) to maturing, ie drying to reduce its intrinsic water. It is currently known, as it has been for a considerable time, to Leave the products to mature in environments in which the microclimate is kept artificially under control, to maintain the temperature and humidity within optimum constant ranges. Said methods ensure that the product does not degrade, however they involve relatively lengthy processing times. For example, ham requires many months of maturing as a minimum. An object of the invention is to considerably accelerate the maturing process. Processes for artificially maturing meat products with microwaves are disclosed in SU-A-1 099 035; SU-A-1 097 252; US-A-4 168 418; DE 39 12 071 A; and in the publication of Brighenti F.; Cavallini A. "use of microwave dryng under vacuum in manufacture of raw ripened meat products" -TECNOLOGIE ALIMENTARI 3/82. Anyway, some drawbacks are present in these processes; for instance, when the pressure is very low for accelerating the process, flash-over are caused which cause burning on the product. A further object of the invention is to improve these processes. The mentioned objects are attained by the invention as characterised in the claims. A further important aspect of the invention is that the heat is supplied to the product by a microwave field which rapidly heats the product from its inside. In particular, said microwaves have a frequency between 500 and 5000 MHz. Preferably, the process is implemented in cycles, each of which comprises a longer phase in which the product is left in an environment under vacuum (the phase during which accelerated evaporation of the intrinsic water occurs) and a shorter phase in which heat is supplied to the product (to compensate the heat loss by evaporation) by a microwave field, while the environment is at substantially atmospheric pressure. The invention is described in detail hereinafter with the aid of the accompanying Figure 1, which shows a section through a non-exclusive embodiment of the plant on a horizontal plane. The illustrated plant comprises an airtight chamber 2, in particular of prismatic shape, having a hermetically sealed door for product introduction and extraction. Within the chamber 2 a conveyor means is provided, defining an endless product conveying track 11 enclosed within the chamber 2. In particular the means 10 is a conveyor belt driven by a geared motor unit 12 and extending in a horizontal plane to form a ring track. Along one branch of the track 11 there are positioned a series of microwave generators 6, arranged to act on the products positioned on the track 11. A vacuum pump 7 is connected to the chamber 2 to draw the air (and the other fluids) from the chamber 2. According to the process of the present invention, the product (ham, "coppa", salami, bacon, sausage or the like) is left in a substantially sealed environment, for example within the described chamber 2, in which the air (by means of the pump 7) is maintained at a relatively low pressure. Recommended values are about 10-40 mm Hg. Hence moisture is transferred from the meat to the chamber 2 by evaporation of the intrinsic water, this occurring continuously and in particular relatively rapidly, it being more rapid the lower the pressure in the chamber. The moisture transferred to the chamber 2 is extracted by the pump 7. The evaporation of the intrinsic water of the meat product is accompanied by heat absorption, hence causing a reduction in product temperature. Heat is therefore supplied to the product to such an extent as to compensate the loss caused by evaporation and to maintain its temperature within a predetermined range of values. For example, a recommended range is 22-25°C. Advantageously the product is supplied with heat by a microwave field, for example by passing the products resting on the conveyor means 10 in front of the microwave generators 6. Preferably, the microwaves have a frequency within the range of 500 to 5000 MHz. This technique simultaneously raises the entire or nearly the entire mass of product substantially to the same temperature very rapidly and without any point of the meat exceeding the maximum scheduled temperature (for example 25°C). Advantageously, if the products are composed of large meat masses, as in the case of hams, the heating phase can be implemented in several time periods (each lasting, one or a few minutes) during which the magnetic field is activated, alternating with rest periods (also of the order of one or. a few minutes). In this manner all internal and surface points of each product, even if of considerable mass, are raised to the required substantially uniform temperature relatively rapidly and without any point of the meat exceeding the maximum scheduled temperature (for example 25°C). In a preferred method of implementing the process, this is effected in successive cycles, each of which comprises a longer phase in which the product is left in an environment under vacuum (during which moisture is transferred by evaporation) and a shorter phase in which heat is supplied to the product by the microwave field, while the environment is at substantially atmospheric pressure. For example the evaporation phase may last for 3-4 hours whereas the heating of the product by microwaves may last for a few minutes. These phases are calculated such that the product temperature always remains within the predetermined temperature range. A typical embodiment of the process using the illustrated plant comprises the following operation. The product is placed on the conveyor 10, after which a fairly high degree of vacuum is produced in the chamber 2 (residual vacuum: 20-30 mm Hg) by extracting the air and moisture from the chamber 2 by means of the pump 7. This causes relatively rapid evaporation of the intrinsic water of the product, with corresponding product cooling to a temperature towards the minimum of the range within which it is maintained (for example 22-25°C). Air is then. again fed into the chamber 2 by opening the air ports 9, so as to restore atmospheric or nearly atmospheric pressure in the chamber 2. This air feed also produces a slight heating of the air already present within the chamber 2. The microwave generators 6 are switched on and the conveyor 10 is driven to rotate the product along its ring track, so subjecting it (when travelling along the branch exposed to the generators 6) to the electromagnetic microwave field, and alternatively to rest periods (when travelling along the remaining part of the conveyor path). This phase comprises a few complete revolutions of the product about the ring and lasts a few minuted. During this phase the product is heated rapidly and substantially regularly throughout its entire mass, to a temperature towards the maximum of the scheduled range. After this, the microwave generators 6 are switched off, the air ports 9 are closed, and the pump 7 is operated to again produce a fairly high vacuum within the chamber 2, with recommencing of the described cycle. The heating phase lasts just a few minutes, while the evaporation phase under vacuum lasts a few (2-5) hours. The entire process can be automatically controlled by a central electronic processor. With the illustrated process, it has been found experimentally that the product usually loses between 2.5 and 12 grams/hour of intrinsic water, depending on its size, its type and its degree of maturing. It has also been found that maturing is accelerated by about 30 times, ie that one day of maturing according to the invention is equivalent to about one month of maturing by the traditional method. Moreover, because of the fact that the process takes place in a sealed environment and mostly in the presence of only a little air, there is no air circulation, hence ensuring that maturing takes place without surface oxidation or drying. In addition, as the process comprises two alternate phases under atmospheric pressure and vacuum respectively, the product undergoes compression cycles alternating with expansion cycles, giving rise to a sort of massaging which improves the escape of the intrinsic water and results in a more uniform internal distribution of any salts and flavouring. As an alternative, instead of alternate phases the described process can comprise superposed or nearly superposed heating and vacuum evaporation phases. Numerous modifications of a practical and applicational nature can be applied to the invention, but without leaving the scope of the inventive idea, as hereinafter claimed.

Claims: A process for maturing meat products characterised in that it comprises cycles each having two alternating phases: processing said meat products in a sealed environment of less than atmospheric pressure to evaporate intrinsic water, and supplying heat to said meat products in an environment of substantially atmospheric pressure to compensate for heat lost through the evaporation of the intrinsic water from the products and to maintain its temperature within a predetermined range, thereby maturing the meat products. A maturing process as claimed in claim 1, characterised in that heat is supplied to the meat product by means of a microwave field. A maturing process as claimed in claim 2, characterised in that said microwave field has a frequency within the range of between 500 and 5000 MHz. A maturing process as claimed in claim 1, characterised in that the heat is supplied to the meat product during a time period followed by a rest period when heat is not provided. A maturing process as claimed in claim 1, characterised in that each cycle comprises a long phase during which the product is left in an environment under vacuum, and a short phase during which heat is supplied to the product by a microwave field while the environment is at substantially atmospheric pressure.

Inventors: RUOZZI GIOVANNI, RUOZZI, GIOVANNI
Applicants: CLASSICA MICROWAVE TECHNOLOGIE, CLASSICA MICROWAVE TECHNOLOGIES, INC.
Application year: 1997
Main classification: A23B4
IPC codes: A23B4