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Forget cooking"¦

September 24, 2002

There are some preferences among the consumers that establish the tendency in the development of new formulations and technologies of food preserving. Those preferences are toward food of easy and rapid preparation, less severely processed (preserving vitamins and nutrients), natural (without preservatives and other artificial additives), fresh, healthy (functional food, low fat, less salt), more secure and with longer preserving.

According to the characteristics searched in the final product, the effort in research and development has been directed in two main directions: towards non-thermal treatments, such as high pressures, pulsed light, electric pulses, irradiation, use of modified atmospheres and biopreservatives, and towards improved thermal treatments, such as ohmic warming or microwaves.

At the present AZTI is working on two methods: pulsed light and vacuum cooking.

Light pulses

This method involves applying white light "pulses" or flashes of high intensity (approximately 20,000 times more intense than the solar light on the earth surface, between 0,001 and 50 J/cm2) and very short duration (less than a millisecond) on the food surface.

In AZTI this technology has been tested in fresh hake fillets (Merluccius merluccius). As a result a reduction in the recount of aerobics, mesophilics and psicotrophics has been observed, as the number of flashes increases, obtaining the destruction of the 90 % from 25 flashes on, that is, a total energy of 38 J/cm2, and no sensorial alteration has been observed in the treatments.   

This technology is a very versatile technology. It is applied in lipids, such as in water, juices or translucent liquid products that allow the passing of the light. In other solid products many experiences have been done. Now, there are various groups testing such technology in France and Belgium.

Vacuum cooking

This technology consist in the vacuum packing of the precook product and its cooking within the package. The thermal treatment is usually under 100 ºC (equivalent to a pasteurisation) and then follows a fast cooling phase until it reaches an adequate temperature to be kept in the refrigerator. This technique presents a clear advantage from the organoleptic and nutritional point of view comparing to conventional thermal treatments, as well as other commercial advantages: the commercial life is increased (20-21 days), cooking techniques are reduced (in fishing products up to 10 %) and it allows to elaborate a major variety of menus simultaneously (as they are packed, they can be warmed in the same oven without mixing the smells). The soft treatment of vacuum cooking is enough to solve the problem of non-sporulated psicotrophic pathogens, such as Listeria monocytogenes. In addition, the cooking of the previously packaged food avoids the possible repollution.

AZTI has obtained very good results with refrigerated precooked dishes of fishing products with 15 and 20 days of duration, such as refrigerated cooked seafood, mackerel and jack mackerel in different sauces. The precooking process of fish improves the its appearance and avoids the later exudation of the final product. The independent processing and subsequent addition of sauce and fish before the pasteurisation improves significantly the taste and the global impression.

Nevertheless the use-by date of the vacuum cooked products is limited to 28 days due to the possible presence of resistant pathogen microorganisms, mainly C. Botulinum, and to eventual breaking of the cold chain that is sometimes produced in the distribution and sale.

Elhuyar Fundazioa