CS266794B1 - Mutant strain for the production of curd cheese Brevibacterium linens - Google Patents

Abstract

The mutant strain Brevibacterium linens, collection no. Laktoflora 201 with increased aminopeptidase activity is intended for the production of cottage cheese and cheeses ripened under fat.

Description

The invention relates to a mutant strain of Brevibacterium linens used in dairy production in the technology of cheesecakes and cheeses ripened under fat in order to improve their organoleptic properties and to accelerate ripening.

Brevibacterium linens Breed (syn. Bacterium linens Weigmann) is commonly found in nature and has been isolated from a variety of natural materials. The increased incidence of Brevibacterium linens in certain areas, such as Olomouc, has been used since the 15th century to produce cottage cheese ripened from the surface inwards under a layer of orange oil formed by oxidative and proteolytic microflora, an important component of which is Brevibacterium linens. The transfer of ripened microflora to new cheeses took place by air, by transfer from the production facility and, last but not least, by the production workers themselves. Since the 1950s, when production conditions gradually changed, production was centralized, and machines were introduced, the professional literature (Olšanský Č .: Všeobecná a mlékařská mikrobiologie, SNP, Prague 1958) spoke about the need to treat cheeses with clean dairy cultures.

Due to the deteriorating quality of milk and the resulting reduced quality of industrial cottage cheese - the main raw material for the production of Olomouc cottage cheese - it is necessary to use cultures with the most suitable properties for maturing cheeses, so as not to prolong the ripening process. Brevibacterium linens acts mainly in the secondary phase of maturation and with its intensive proteolytic activity cleaves the milk protein casein into shorter protein grafts - peptides, from which individual amino acids are further cleaved by exogenous proteinases, which according to Pala et al. (Other results of the Taste Study of Olomoucké tvarožkov V; Proceedings of the 3rd Symposium on Aromatic Substances in Foodstuffs, Banská Bystrica 1977), apart from volatile fatty acids and volatile sulfur compounds, they mainly contribute to the typical aroma of cheeses.

Three strains of Brevibacterium linens sb are currently stored in the collection of microbiological cultures of the Dairy Industry Development Plant in Prague - Vokovice. No. Laktoflora 200, sb. No. Laktoflora 980 and sb. No. Laktoflora 1010. Until recently, strain 200 was supplied as part of the so-called sebum culture to almost all dairy plants producing cheeses matured under sebum. However, with its proteolytic properties, it no longer fully met the current needs of dairies. Of the ten evaluated strains of Brevibacterium linens, the sb strain appeared to be the most suitable from the point of view of the production of proteolytic enzymes. No. Laktoflora 980. Nevertheless, its production of proteolytic enzymes was not at the desired level.

These disadvantages are eliminated by a mutant strain of Brevibacterium linens, Laktoflora 201 with increased aminopeptidase activity, stored in the Collection of Microbiological Cultures of the Development Plant of the Dairy Industry Laktoflora, Prague-Vokovice, Ke dvoru 12.

The mutant strain of Brevibacterium linens, Laktoflora 201 according to the invention was obtained from the strain Brevibacterium linens, sb. No. Lactoflora 980 using UV radiation. The mutagenic effect of UV radiation consists in the formation of covalent bonds between adjacent thymines in the DNA molecule to form pyrimidine dimers (Cudlín J .: Selected Methods in Microbiology, Academia, Prague 1981). A bactericidal lamp, 15 W power, from Philips, the Netherlands, was used for the mutation. - Centrifuged and washed Brevibacterium linens cells, sb. No. Lactoflora 980 were suspended in 50 mmol.I ^- · ' ^- sterile phosphate buffer pH 7.0 and irradiated with UV light from a distance of 30 cm. The cells were irradiated in petri dishes for 30, 60 and 90 seconds, shaking the suspension continuously. After irradiation, the individual suspensions were undiluted in saline and inoculated into complete agar petri dishes. To prevent photoreparation, cultivation was performed for the first 24 hours in the dark. Out of 135 mutant grafts, 8 mutant strains were selected and further monitored. The best proteolytic properties were shown by the mutant strain M2 (irradiation 60 s). The mutation was made in January 1986. It showed 14 days after the mutation

266794.

strain M2 160% of the extracellular aminopeptidase activity of the original parent strain. After 8.5 months it was 185%, after 11.5 months 160%, after 2? months 135% aminopeptidase activity of the original strain, ie 2.1 nkat..mg ^-1 (expressed in aminopeptidase activity related to the content of proteins produced in the medium). A method based on the spectrophotometric determination of yellow 4-nitroaniline at 425 nm, which aminopeptidases release from L-leucyl-4-nitroanilide, was used to determine aminopeptidase activity (Lorand L .: Methods of Enzymology, vol. XIX, Proteolytic enzymes. Academic Preas, New York 1976). The proteinase activity of the mutant strain is comparable to the activity of the original strain 980. Cell morphology and other biochemical features of the culture are identical to the parental strain 980. The mutant strain was deposited on June 8, 1988 in the Vokovice, under the name Brevibacterium linens, sb. No. Laktoflora 201.

Method of using the obtained strain of Brevibacterium linens, sb. No. Laktoflora 201 can be further illustrated by several examples.

Example 1

Application for Olomouc cottage cheese

An appropriate amount of ripening salts, depending on the titratable acidity, sodium chloride and drinking water according to the curd's dry matter, was metered into the kneader together with 500 kg of curd, to which 10 ml of a Candida valida yeast containing ΙΟ ^ θ to 10 ^ cells in 1 ml was added. .The first phase of maturation took place in an oven at a temperature of 23 ° C to 24 ° C. On the third day after molding, the curds were bathed in drinking water and sprayed with a pneumatic gun with 120 ml of a diluted Brev suspension on a drip belt. linens, sb. No. Lactoflora 201 containing $ 10 to $ 10 cells in 1 ml. Dilution was performed with 0.9% saline in a ratio of 1: 5 · Next, the curds matured in ripening rooms in boxes at 21 ° C and were packed 7 days after molding. Simultaneously with these cottage cheeses, cottage cheeses were made in exactly the same way using the original Brev strain. linens, sb. No. Laktoflora 980. A significant difference between these types of Olomouc cottage cheese was sensory. Cottage cheese made with the experimental strain Brev. linene, sb. No. Laktoflora 201 were evaluated in a preferential test as demonstrably tastier than cottage cheese made with the Brev strain. linens, sb. No. Laktoflora 980.

Example 2

Dessert cheese applications'

South Bohemian soft ripening cheese was produced according to the directional technological procedure (Directional technological procedures, Mlékárenský průmysl koncern Praha, 1987). After salting, the cheeses were treated with a suspension of the yeast Candida valida and matured for 2 days at a temperature of 19 to 20 ° C and a relative humidity of 90%. On the third day after salting, the cheeses were treated by mist spray with brine, concentration 9% by weight. NaCl with the addition of Brev culture suspension. linens, sb. No. Lactoflora 201 in an amount of 10 ml of concentrate containing ΙΟ ^ θ to 10 ^ cells in 1 ml per 100 l of saline. The cheeses thus treated matured at a temperature of 14 to 16 ° C and a relative humidity of 95% for 12 days. During this time, they were treated twice more with Brev culture. linens. In the case of manual treatment of cheeses, the Brev. linens is diluted 1: 200, ie 50 ml of suspension per 10 liters of saline. Sensory analysis revealed a high degree of ingestion of the experimental cheeses. The experimental cheese evaluated the experimental cheeses as cheaper better than the deaer cheeses made with the Brev strain. linens, sb. No. Laktoflora 980.

Claims (1)

266794 OBJECT OF THE INVENTION Mutant strain for the production of Brevibacterium linens cheesecakes, Laktoflora 201 with increased aminopeptidase activity.