A METHOD OF ACCELERATING THE RIPENING OF CHEESE AND AN APPARATUS FOR CARRYING OUT THE METHOD

Abstract: The ripening of cheese is accelerated by subjecting the cheese to an electric field the direction of which is changed at constant or varying frequency. An apparatus for carrying out the method includes inter alia two electrodes between which the cheese body may be placed, said two electrodes being connected to a direct-current source the pole direction of which may be changed.

Description: A Method of Accelerating the Ripening of Gheese and An Apparatus for Carrying out the Method This invention relates to a method of acceler¬ ating the ripening of cheese and an apparatus to be used in that respect. As regards conventional cheese ripening carried out at temperatures of from 10 to 20°C the ripening pe¬ riod is from a few weeks to several months dependent on the type of cheese. Long ripening periods imply that cheese producers must invest huge economical resources in the cheese products, large and expensive storage ca- pacity is required and the cheese products necessitate protracted care. The longer the ripening period is, the more the costs of cheese production increase, entailing that there are internationally big economical interests in reducing the ripening period when producing cheese. Therefore, extensive researches are today being instituted into cheese ripening acceleration. Such re¬ search concentrates primarily on the increase of the ripening temperature or on the selection and production of protease systems which, when added to the curd, are capable of increasing the rate of the proteolytic decom¬ position of casein, thereby increasing the ripening rate. The ripening temperature of a certain type of cheese is decisive for the characteristics of the com- pleted cheese, in that a constant temperature offers the best ripening quality and, consequently, an increase of the ripening temperature of such a type of cheese in¬ volves the risk that the ripened cheese has character¬ istics differing from those desired. The increase of the protease concentration in the curd results in the following disadvantages: the added proteases have a tendency to impart un- desired flavours to the cheese, such as bitter peptides, the cheese ripening controlling becomes more dif¬ ficult, and due to the high content of protease the ripened cheese products get soon overripe, i.e. the period during which the cheese can be consumed is shortened and the cheese products should therefore be distributed, sold and consumed within a very short period compared to conventionally ripened cheese. Moreover, DE patent No. 950,104 discloses a me- thod of accelerating cheese ripening, according to which the cheese is subjected to ultra-sound. This method is inter alia said to effect that the ultra-sound cause the cell membranes of bacteria to be destructed so as to li¬ berate inter alia endoenzymes which increase the rate of ripening. An increased concentration of enzymes is thus obtained which involves the same drawbacks as described above. Thus, there is a large demand on a method of ac¬ celerating the cheese ripening, according to which me- thod the ripe cheese possesses the same properties and characteristics as a cheese product of the same type ri¬ pened in a conventional manner and it is therefore the object of the invention to provide such a method. It has now proved that this is obtained by the method according to the invention which is characterized in that the cheese product at least during part of the ripening process is placed in an electric field the di¬ rection of which is being changed at a constant or vary¬ ing frequency during the entire course of this part of the ripening process. The accelerating effect of the method according to the invention is supposed to be due to the fact that the charged proteases and product peptides of the cheese move differently in comparison with the stationary inte- gral casein network in the electric field. The proteases thus get rapidly into contact with new areas of the ca¬ sein network and the generated product peptides acting inhibiting on the proteases are quickly removed there¬ from, in contradiction to what happens under normal ri- pening conditions without electric field, in which case the peptide products are only removed from the proteases by diffusion, thereby creating a gradient of product peptides around the proteases. When this processing in an electric field is in- terrupted the migration of the proteases and the product peptides will again take place by pure diffusion and the ripening rate and thus the period of distribution, sales and consuming will then be the same as with the same type of cheese ripened without being placed in an elec- trie field having varying direction. In view of the fact that the remaining ripening conditions, such as temperature, moisture of the atmo¬ sphere, the composition of the curd, care, and so on, may be the same during ripening accelerated by the me- thod according to the invention as during ripening under conventional conditions, cheese products are thus obtai¬ ned that are identical with corresponding cheese pro¬ ducts ripened in the ordinary way. Neither does any dif¬ ference appear between the product peptides generated during ripening, accelerated according to the invention and under conventional conditions, respectively. The accelerating effect of the method according to the invention is a function of the electric field strength, the type of cheese and the frequency of changing the direction of the field. The field strength may be in the range from 0.05 Volt/cm to 10 Volt/cm dependent on the type of cheese and the desired accele¬ rating effect etc. Generally, a greater accelerating ef- feet is obtained, the greater the field strength is. The ZKZ Olϊ 1987 - r- 4 maximum field strength depends on whether it is possible to eliminate the heat generated in the cheese body, thereby avoiding an undesired temperature increase. The frequency of changing the direction of the field may range from one change of direction every 0.1 sec. to 24 hours. By changing the direction of the field it is obtained that no peptides, no amino acids, no pro¬ teases, no salts or any other charged particles at the electrodes are lost and that no uneven distribution of said substances is effected in the cheese body. The limits for the frequency are settled by the circumstance that, on one hand, it must be so high that no losses are provoked at the electrodes and no inhomo- geneity occurs and, on the other hand, so low that pro- duct peptides and proteases are in a position to migrate away from each other. The higher the field strength is, the higher the frequency may thus be. By ensuring that the field strength is constant in any plane perpendicular to the electric field through the cheese body, the same acceleration of the cheese ripening throughout the cheese is to the largest pos¬ sible extent obtained. The optimum conditions with respect to field strength and the frequency of changing the direction of the field may be determind by simple experiments with the individual cheese products and further by given con¬ ditions relating to experiments. The field strength is provided by means of two oppositely located electrodes on either side of the cheese body and in communication with part of or with the entire surface of each individual side of the cheese body, a potential difference being applied across the electrodes. The direction of the field is changed by changing the potentials of the electrodes. The temperature may be in the range from 5 to 30°C, preferably the temperature to be used in conven¬ tional ripening of the same cheese. SUBSTITUTE SHEET The temperature of the cheese body may be regu¬ lated according to any method, but it is preferred to control it by means of the electrodes used to provide the electric field by air- or water-cooling thereof, for instace in combination with controlling the room tempe¬ rature. In a preferred embodiment of the method according to the invention of accelerating the ripening of cheese bodies having at least two substantially parallel late- ral surfaces, the electric field is provided by dis¬ posing the two electrodes oppositely so as tc be in con¬ tact with substantially the entire surface of either of the two sides, and by applying an electric potential difference across said two electrodes by connecting them to a direct current source comprising a pole changer. The preferred embodiment may for instance imply that a number of cheese bodies be superposed and that alterna¬ tely positive and negative electrodes be inserted be¬ tween the cheese bodies. This embodiment provides for obtaining a substantially homogeneous electric field throughout the cheese bodies and thereby a cheese ripen¬ ing as homogeneously as possible. The electrodes used in the method according to the invention may be produced from any conventional electrode material, but it is preferred to make use of such electrodes that do not release metallic ions or me¬ tal on alternative curd moulds, since such a generation may influence the flavour of the cheese and since such metals frequently are toxic. In view of the above it is preferred to produce the practised electrodes from non-metalic conductive materials, such as conductive ceramic materials, carbon and conductive materials made from charged organic poly¬ mers or metallic conductors coated with such a non-me- talllc conductive material preventing metallic ions from being imparted to the curd. 1987 -07- 29 6 It has now proven that by arranging ion-selective membranes (e.g. of the type HR98, trade of DE DANSKE SUKKERFABRIKKER, DDS-RO Division, Denmark) between steel electrodes and cheese bodies, it is effectively avoided 5 that metal be imparted to the cheese. The acceleration of the cheese ripening may for instance be effected in an apparatus comprising two oppositely located elec¬ trodes which may for instance be subjected to water- or air-cooling and have a surface that does not impart me- 10 tal ions or metal in any other form, and a direct cur¬ rent source adapted so that the direction of the elec¬ tric field provided across the electrodes may be changed at constant or varying frequency and so that the numeric value of the field strength may be varied. 15 Electrical processing has previously been practised in respect of cheese production. US patent No. 1,774,610, issued 2 September 1930, discloses a process of pasteurizing cheese, according to which an electric field is passed for a while through 20 the cheese in solid, plastic condition, thereby heating the cheese. The potential difference is stated to range from 30 to 220 volts and the average current density va¬ ries from one-half to 10 amperes per cm 2 . US patent No. 2,848,400, issued on 19 August 25 1958, discloses a process of preventing cheese from ad¬ hering to a cheese mould made from stainless steel, in which a negative potential in relation to the electrical potential of the milk is applied to the container, en¬ tailing alkaline reactions to occur at the container 30 wall (cathode) and, consequently, no solidification is then effected. Said two processes differ totally from the method according to the invention and have quite other pur¬ poses. 35 In contradiction to the process according to US patent No. 1,774,610 it is, as mentioned above, i por- SUBSTITUTE SHE: ISA/Sc tant in the method according to the invention that the temperature is kept at the usual temperature of a cor¬ responding cheese conventionally ripened, if necessary by cooling by means of the electrodes. The practised field strength is moreover considerably lower than that used in the method according to the invention. Alcaline reactions at the electrodes are as well undesired in the method according to the invention, as described above. The purpose of changing the field and of ensuring that the electrodes do not release metal is to avoid reactions at the electrodes. The method according to the invention may be used in the preparation of any general kind of cheese, apart from moulded cheese, since protease added exogenously to the curd (cheese ripening enzymes) may further be added to the cheese beyond the rennet enzymes added in the conventional cheese production. By a suitable choice of temperature, field strength and the frequency at which the electric field changes, a rapid ripening without deteriorated quality of the final cheese product is thus obtained by the pro¬ cess according to the invention. The invention will be elucidated in detail by the following examples. EXAMPLE 1 A newly salted cheese product of the type 45* Danbo having the following dimensions, 8 cm x 30 cm x 30 cm, is horizontally placed between two water-cooled, stainless steel electrodes. During a four-week ripening period a constant coolant temperature of 15°C is prac¬ tised, a constant current density of 50 mA and a con- stant pole changer frequency of eight direction changes per 24 hours. After a four-week ripening period the cheese product was obtained that at a visual and organo- leptic assessment showed a ripening degree exceeding that of a corresponding cheese conventionally ripened at 15°C for twelve weeks. EXAMPLE 2 10 fresh cheese bodies of 5 kg having a cross- sectional area of 900 cm 2 and a height of 8 cm is ripe¬ ned under the influence of a constant potential diffe¬ rence of 1.5 V at a temperature ranging from 17 to 18°C for three weeks at 95* relative humidity (RF) , then at a temperature ranging from 13 to 14°C and 85* RF for two weeks and finally at a temperature of 10°C and 70* RF for five weeks. Two plates of stainless steel were used as electrodes. The current intensity was in the range from 25 to 40 mA during the entire ripening period, and the current direction was changed by means of a pole changer once every four hours. Samples were weekly taken for chemical analysis and bacteriological analyses were carried out after week 0 and 10. 5 fresh cheese bodies of the same time we used as control cheese, they were subjected to the same process- ing as mentioned above, however, without the impression of a potential difference. As far as each individual sample is concerned the percentage of solids, the percentage of total-nitrogen, free N-terminal groups, the pH-value, the protein con- tent and the content of soluble protein were measured after 1, 2, 3, 4, 5, 6, 8 and 10 weeks. After ten weeks the content of lactose, ashes and amino-N was measured. The results of the analyses appear from Figs. 1 to 4, in which Fig. 1 illustrates the ratio between soluble N and total N as a funtion of the elapsed ripening period, Fig. 2 illustrates the content of soluble N as a function of the elapsed ripening period, Fig. 3 illustrates the ratio between free N- terminal groups and total N as a function of the elapsed ripening period, and Fig. 4 illustrates the development of the pH- value during the ripening period. It appears from these figures that the processing by the method according to the invention offers a consi- derable accelerating of the ripening process, in parti¬ cular during the first weeks thereof. The results are resumed in Fig. 5 illustrating the ripening period Vp of the experimental cheese products as a function of the ripening period, Vg, of the control cheese. This curve has been drafted by reading, for a given ripening period VJJ of the control cheese, the attained value in any one of the figures 1 to 3, subsequently reading the time it takes before the experimental cheese products attain said value. It will be seen that within the first five weeks Vp - 0.75 Vg, following which the difference grows progressively, so that Vp * 0.6 x V j after ten weeks.

Claims: P A T E N T C L A I M S 1. A method of accelerating the ripening of cheese, caracterized in that the cheese product at least during part of the ripening process is placed in an electric field the direction of which is being changed at a constant or varying frequency during the entire course of this part of the ripening process. 2. A method as claimed in claim 1, characterized in that the numerical value of the field strength is in the range from 0.05 volt/cm to 10 volt/cm. 3. A method as claimed in claim 1 or 2, charac¬ terized in that the frequency changing the direction of the field is in the range from one change of direction every 0.1 sec. to 24 hours. 4. A method as claimed in any of claims 1 to 3, characterized in that the temperature of the cheese body is kept in the range from about 5 to about 30°C. 5. A method as claimed in any of the preceding claims, characterized in that the field strength is sub¬ stantially constant throughout any cut through the cheese perpendicular to the direction of the electric field. 6. A method as claimed in any of the preceding claims, characterized in that the temperature of the cheese body is controlled by liquid- or air-cooled elec¬ trodes. 7. A method as claimed in any of the preceding claims of accelerating the ripening of cheese products having at least two substantially parallel lateral sur¬ faces, characterized in that the electric field is pro¬ vided by oppositely arranging the two electrodes, so that they are in communication with substantially the entire surface of either of the two parallel sides, and by applying a potential difference across said two elec¬ trodes by connecting them to a direct-current source SUBSTITUTE 3 iSA/sε provided with a pole changer, and that the direction of the field is changed at constant or varying frequency by changing the direction of the current by means of the pole changer. 8. A method as claimed in any of the preceding claims, characterized in that a ion-selective membrane is inserted between the surface of the electrodes and the curd. 9. A method as claimed in any of the preceding claims, characterized in that beyond the bacteria and fungus cultures and rennet enzymes added in conven¬ tional cheese production, addditional micro organisms and/or proteases which owing to their casein-decomposing properties accelerate further the cheese ripening are added to the curd. 10. An apparatus for accelerating the cheese ri¬ pening in the method as claimed in claim 1, character¬ ized in that it includes two oppositely positioned elec¬ trodes which may for instance be subjected to water- or air-cooling and have a surface that does not under the working conditions release metal ions or metal in any other form, and a direct-current source adapted so that the direction of the electric field provided via the electrodes may be changed at constant or varying fre- quency, and so that the numerical value of the field strength may be varied.

Inventors: HAU JANN, POULSEN OTTO MELCHIOR, HAU, JANN, POULSEN, OTTO, MELCHIOR
Applicants: HAU JANN, POULSEN OTTO MELCHIOR, HAU, JANN, POULSEN, OTTO, MELCHIOR
Application year: 1987
Main classification: A23C19
IPC codes: A01J25, A23C19