Process for the preparation of raw milk cheese

Abstract: Process for the preparation of cheese, using milk, which may or may not be partly or wholly skimmed, that has undergone no heat treatment or only a non-pasteurizing heat treatment. According to the invention, the milk is separated into a permeate and a retentate using a microfiltering treatment, whereafter the retentate is subjected to a mild heat treatment, such that the phosphatase reaction therein has just become negative. Then the thus treated retentate is mixed with the permeate. Optionally, for setting the fat content, cream which may or may not be pasteurized is added. Finally, cheese is prepared in an otherwise conventional manner.

Description: This invention relates to a process for the preparation of raw milk cheese, using milk, which may or may not be partly or wholly skimmed, that has undergone no heat treatment or only one non-pasteurizing heat treatment. Cheese which is prepared using milk so obtained, is generally referred to as raw milk cheese. Raw milk cheese is distinguished from cheese prepared from pasteurized milk by a fuller flavour and a more aromatic character, owing to the fact that the substances in the milk that are essential to the cheese making process have not been exposed to higher temperatures and therefore have substantially retained their natural character. A problem in preparing such cheese is that both in the production of the milk and in the subsequent processing thereof, particular steps must be taken to prevent undesired bacterial growth. In practice, however, it appears that in spite of all care taken when the milk-producing animal is fed, the milk is obtained and processed further, it is difficult to prepare cheese of constant quality or ripen the cheese formed while maintaining a desired quality. In this connection, it is in particular the presence of bacteria of the coli-aerogenes group that has a direct and adverse influence on the cheese. These bacteria can ferment lactose while forming carbon dioxide and hydrogen, and the formation of this gas has an extremely adverse influence on the quality of the cheese. Another problem is the possible presence in the milk of non-sporing pathogenic bacteria, such as the tubercle and typhoid bacilli, Brucella abortus , pathogenic streptococci and staphylococci. These bacteria are killed only with a proper pasteurization. Pasteurization, however, is a treatment which cannot be used in the preparation of raw milk cheese. As a consequence, it happens regularly that quantities of milk for the preparation of cheese of the type referred to must be rejected, which gives rise to production loss. The object of the invention is to provide a process for the preparation of cheese of the raw milk type, in which the cheese milk is so treated that it retains its natural character, whilst the risk of the presence of harmful pathogenic bacteria therein is not greater than in milk which has been pasteurized in the conventional manner. According to the invention, the milk is separated into a permeate and a retentate using a microfiltering treatment, whereafter the retentate is subjected to a mild pasteurisation, such that the phosphatase reaction therein has just become negative, whereafter the retentate so treated is mixed with the permeate, optionally, for setting the fat content, cream which may or may not be pasteurized is added, and cheese is prepared in an otherwise conventional manner. Surprisingly, it has been found that cheese prepared by the process according to the invention does not contain any pathogenic bacteria at all, nor do any bacteria appear to be present that have a negative influence on the quality of the cheese in any other respect. Organoleptically, cheese thus obtained proves to have the characteristic taste that is typical of cheese which has been prepared from milk which has not been subjected to any treatment at all. According to the invention, it has further been found that when prior to the cheese preparation mesophilic lactobacilli are added to the treated milk, the aroma of the cheese obtained can be varied, depending on the specific choice of lactobacilli. According to Dutch government regulations, milk from which raw milk cheese is prepared must possess a phosphatase activity that is normal for raw material. The milk obtained by the process according to the invention satisfies this criterion. This phosphatase activity, as well as the absence thereof in the retentate treated in accordance with the invention, can be determined in a simple manner, for instance in a mannner as described in IDF Standard 82A: 1987. It is noted that European patent specification 0 194 286 discloses a process in which milk is subjected to a microfiltration treatment and the retentate obtained is sterilized and added to the permeate. The preparation of raw milk cheese is neither described nor suggested in this publication. The invention is illustrated in and by the following examples. Example 1 Cooled raw bulk milk was heated to 49°C and skimmed. The cream was pasteurized at 74°C for 10 seconds and then cooled. The skim milk was cooled to 2°C and subsequently microfiltered. This occurred in a continuous process in a filtration unit with a ceramic membrane (Ceraver) of 0.2 m 2 having an average pore size of 0.8 µm. 200 liters of skim milk were heated to 48-50°C and via a buffer vat the milk was pumped into the filtration unit. The retentate outlet was kept closed until the desired concentration factor had been achieved. Then the retentate discharge was initiated. The concentration factor (Kf) was controlled by regulating the discharge of the retentate. The Kf was 7. During microfiltration, the temperature was maintained at 48°C. The circulation flow was 6.5 m 3 /h and the output transmembrane pressure was 0.3 bar. The discharged permeate and retentate were cooled in line to approximately 5°C. The retentate was pasteurized at 74°C for 10 seconds and cooled to 4°C. For the benefit of the cheese preparation, the permeate and pasteurized retentate were put together in the original proportion and pasteurized cream was added to adjust to a fat content equal to the protein content of the milk. 200 liters of this standardized milk were pumped into the cheese vessel and adjusted to renneting temperature using warm water in the double wall of the cheese vessel. After addition of 1.6 liter of starter, 80 g of a 33% CaCl 2 solution, 150 g of 41% NaNO 3 solution and 46 g of rennet, cheese was prepared in the conventional manner in 10 kg moulds. The cheese was salted for 3 days and then ripened at 14°C for 3 months. The cheese was tested with regard to odour and flavour by a panel of five cheese tasters comparing it with a cheese which had been prepared from raw milk in the traditional manner. The test cheese had the characteristic taste that is typical of cheese prepared from raw milk. Example 2 Raw milk was skimmed and the cream was pasteurized as in Example 1. 800 liters of raw skim milk were then microfiltered in a filtration unit equipped with a ceramic membrane (Ceraver) having an average pore size of 0.8 µm and a membrane surface area of 3.8 m 2 . Microfiltration occurrred at a temperature of 48°C. The circulation flow was 110 m 3 /h at a constant transmembrane pressure up to Kf = 7. The retentate was pasteurized at 74°C for 10 seconds. The permeate and retentate were mixed in the original proportion and pasteurized cream was added until a concentration equal to that of the protein in the milk was achieved. With this standardized milk, cheese was made in an 800-liter cheese vessel as in Example 1. The cheese was ripened and tested in a similar manner. The test results were equal to those in Example 1. Example 3 Raw skim milk was microfiltered as in Example 2 and standardized in the manner specified there. Prior to the preparation of the cheese, a mixed culture of mesophilic lactobacilli was added to the milk. This mixed culture of mesophilic lactobacilli was obtained in the following manner: From ripened raw milk cheese of a very good flavour, lactobacilli strains were isolated by seeding dilutions of the cheese in a specific nutrient medium for mesophilic lactobacilli (Rogosa agar) and, after incubation, inoculating loose colonies and culturing them purely in a conventional manner. Full-grown pure cultures were put together in proportional amounts, diluted with a tenfold amount of sterilized milk and stored until use at -40°C. After defrosting, an amount of mixed culture was added to the cheese milk, such that a concentration of 50-500 lactobacilli per ml of milk cheese was obtained. The cheese was prepared, ripened and turned as in Example 2. The cheese prepared and ripened in this manner possessed, in addition to the flavour that is typical of cheese prepared from raw milk, a pungent taste which is appreciated by consumers of raw milk cheese.

Claims: A process for the preparation of cheese, using milk, which may or may not be partly or wholly skimmed, that has undergone no heat treatment or only one non-pasteurizing heat treatment, wherein the milk is separated into a permeate and a retentate using a microfiltering treatment, whereafter the retentate is subjected to a mild pasteurisation, such that the phosphatase reaction therein has just become negative, whereafter the retentate so treated is mixed with the permeate, optionally, for setting the fat content, cream which may or may not be pasteurized is added, and cheese is prepared in an otherwise conventional manner. A process according to claim 1 wherein prior to the preparation of cheese, mesophilic lactobacilli are added to the treated milk.

Inventors: HUP GERHARD, ZOON PETRONELLA, HUP, GERHARD, ZOON, PETRONELLA
Applicants: FRIESLAND FRICO DOMO COOP, FRIESLAND (FRICO-DOMO) COOPERATIEVE B.A.
Application year: 1992
Main classification: A23C19
IPC codes: A23C9, A23C19