Production of food

Details Production of food Production of food

1996-08-20

1998-04-14

Ketter, James

Chemistry: molecular biology and microbiology

Micro-organism, per se ; compositions thereof; proces of...

Fungi

C12N 114

Patent

active

057390304

DESCRIPTION:

BRIEF SUMMARY
This application claims benefit of international application PCT/GB9500368, filed Feb. 22, 1995.
THIS INVENTION relates to the production of food.
It is known to produce food suitable for consumption by humans by culturing fungi. Suitable fungi are microfungi of the class Fungi Imperfectio A process of this type is described in British Patents Nos. 1,210,356 and 1,346,062 and strains of Fusarium for use in food production are described in British Patent 1,346,061 and in U.S. Pat. No. 4,347.
In order to render such products more suitable for consumption by humans it is considered desirable to reduce their nucleic acid content. British Patent No 1,440,642 discloses a process in which this is achieved by subjecting Fungi Imperfecti to a temperature of 55.degree. to 72.degree. C. for a period of at least 60 seconds at a pH of 4.7 to 7.0. This temperature was apparently selected because ribonuclease survives such conditions whereas protease is destroyed; thus the protein content of the fungus would not be degraded by protease but the ribonucleic acid would be degraded by the ribonuclease. The process is disclosed as producing a final RNA content of 1 to 4% from organisms originally containing 7 to 12%. In certain instances RNA contents of the product of less than 1% were disclosed. In the experiments described fungi were generally separated from their growth media and heated in the presence of water or aqueous solutions of NaCl or NH.sub.4 Cl under various conditions. In example J however the fungi were heated in the presence of their growth medium to a temperature of 64.degree. C., filtered, washed, reslurried in water and spray dried.
The effect of temperature and duration of heat treatment is shown in Example A of British Patent No 1,440,642. In no case of treatment above 66.degree. C. was the final RNA content below the 2% by weight level, which figure was not corrected for biomass loss. The figure based on the final product after biomass loss would have been higher.
The above process suffers considerable loss of proteinaceous material however.
We have now devised a process in which any loss of ribonuclease activity does not prevent a satisfactory reduction in nucleic acid content.
We have now found that it is possible to carry out effective removal of RNA with less loss of protein by operating at higher temperatures in the range of over 68.degree. C. to 80.degree. C., preferably 69.degree. to 75.degree. C. and more preferably 70.degree. to 74.degree. C. for example above 72.degree. up to 74.degree. C. providing that the fungus is raised to such temperatures in the presence of its growth medium.
It is not known why this phenomenon occurs, but it may be that the fungus in its growing state is more susceptible to RNA loss on heating and that maintaining it in contact with its growth medium to the treatment temperature maintains it in its susceptible state.
The invention comprises a process in which the nucleic acid content of Fungi Imperfecti is reduced which comprises growing it in the presence of a growth medium, raising its temperature in the presence of the growth medium to above 68.degree. C. and preferably at most 80.degree. C. for example 69.degree. to 75.degree. C., preferably 70.degree. to 74.degree. C. and more preferably above 72.degree. C. to 74.degree. C. and separating at least part of the growth medium from the fungus. Nucleic acid passes from the fungus to the growth medium and the treated fungus has a reduced nucleic acid content.
The process permits a high retention of fungal components of nutritional value especially protein. It is believed that protein is retained more readily because during nucleic acid removal it is in a substantially coagulated state. At temperatures higher than 80.degree. C. the coagulation of proteinaceous material can occur sufficiently rapidly to impede adequate loss of nucleic acids and at temperatures lower than 68.degree. C. it is generally insufficient to prevent a substantial loss of protein.
The nucleic acid content of the treated fungus is preferably at most

REFERENCES:
patent: 4163692 (1979-08-01), Yates
patent: 4501765 (1985-02-01), Towersey et al.
patent: 4555485 (1985-11-01), Marsh
Ohta, S. et al. 1971 Applied Microbiology 22(3): 415-421.
Maul, S.B. et al. 1970 Nature 228 (181).

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