FIELD OF THE INVENTION

This invention relates to the manufacture of chee with a substantially reduced fat content.

DESCRIPTION OF THE PRIOR ART

Cheese made from milk with substantially reduced fat (skim milk cheese, low fat cheese) presents problems in manufacture in that it is difficult to ensure that sufficien moisture is retained in the substance and the flavour develo ment in this product, largely devoid of fat, is extremely sl Consequently, cheese made from substantially fat reduced mil tends to be hard, has little flavour, and therefore has a lo consumer appeal. In order to overcome the disadvantages of prior known processes, it ^~ s ^" an-oixject of the present invention to provide a method of manufacturing cheese with a substantiall reduced fat content including the incorporation of higher moisture content, more pliable body and the development of more flavour.

It is known in cheese making processes that the c or coagulum shrinks in response to heat, the level of which i termed the cooking temperature, and in response to a drop in Also it is understood that Calcium ions associated with the casein act as bridges or links in the shrinking processes so the higher the calcium content, the more severe will be the shrinkage and the more extensive will be the expulsion of moisture from the coagulum.

Normally, cheese is made with lactic bacteria whic ferment lactose to lactic acid. There are among the lactic bacteria some species which, besides producing lactic acid, can also develop other flavour compounds. Such cultures are for instance used in Yogurt manufacture. They consist of strains of Lactobacillus buigaricus and Streptococcus thermophilus.

U.S. Patent No. 1464617 (Leprino) describes a process of making a pasta filata cheese, comprising the steps of:

(a) inoculating a batch of pasteurized cow's milk with a pasta filata starter culture providing an effective amount of Streptococcus thermophilus and at least one Lactobacillus capable of growing at a temperature in the range of from 110 to 120

(b) converting the milk batch to a mixture of cur and whey;

(c) cooking the curd-whey mixture at a temperatur favoring the growth of said Streptococcus thermophilus and Lactobacillus;

(d) separating the resulting warm granular curd from the whey, the curd having an internal pH in the range .of from 5.6 to 6.2;

(e) washing and cooling the separated granular curd by contacting it with water having a lower temperature than the curd; and (f) holding the washed and cooled granular curd at a temperature in the range of from 33 to 65 F until the internal pH of the curd has decreased to a pH below 5.5 suitable for mixing and stretching the curd to obtain pasta filata stringiness. U.S. Patent No. 4085228 (assigned to Leprino) describes manufacturing of low-moisture Mozzarella cheese including the steps of inoculating a batch of pasteurized cow's milk with a starter culture comprising f-rom 1 to 3% based on the weight of the milk batch of Streptococcus thermophilus together with Lactobacillus selected from

Lactobacillus buigaricus , Lactobacillus helveticus, or both Lactobacillus buigaricus and Lactobacillus helveticus, makin cheese curd from the thus-inoculated milk including cooking the curd at 100° to 125°F, mixing and stretching the curd in water at a temperature above 130 F to impart a stringy textu to the cheese, molding the mixed curd into bodies, and salti the molded bodies, wherein the improvement comprises: inoculating said milk batch before making the cheese curd,

with from 0.5 to 3.0% based on the weight of the milk batch of an additional viable culture selected from cultures of Pediococcus cerevisiae, Lactobacillus plantarum, Streptococcus faecalis, Streptococcus durans and Lacto- bacillus casei, and at the conclusion of said process holdin the salted cheese bodies at a non-freezing temperature below 55 F for 5 to 30 days while reducing the residual lactose sugar content of the cheese, said holding being continued until said cheese bodies have an average lactose sugar conte below 0.3%. The same disclosure is made in French publicati 2 361 182.

French specification 2161766 (Marchand) describes manufacturing process generally the same as that for ordinar yoghurt and cheese. German specification 26 57418 describes a manu¬ facturing method using prolonged incubation and as cultures Lactobacillus casei together with ordinary cultures.

SUMMARY OF THE INVENTION

It is an object of the present invention to provid a manufacturing process for a natural cheese which is of substantially reduced fat contant.

A further object is to develop a natural cheese of substantially reduced kilojoule value. Yet another object is to provide a cheese of texture and flavour such that it is suitable for direct consumption by consumers as a "table" cheese (rather than cheese for manufacturing purposes) as a substitute for hard and semi-hard varieties such as Cheddar, Edam, Gouda, Colby, Cheedam, Cheshire, Monterey, Port de Salu and others. Thus broadly this invention provides a method of manufacturing cheese with a substantially reduced fat content including the steps of inoculating a batch of milk of a fat content of 0.3 to 1.5% with a normal cheese starter culture together with a culture of Lactobacillus buigaricus and Streptococcus thermophilus to produce the required flavour and to obtain rapid fermentation of lactose and a culture of

Lactobacillus casei to assist in hydrolysis of protein.

In the method of manufacture of the present invention we use in addition to the normal cheese starters, amounts of Lactobacillus buigaricus and Streptococcus thermophilus selected for their specific -flavour producing spectra (properties ^* ) . In addition, in the present inventio an inoculum is added of Lactobacillus casei.

Also a monovalent cation such as Sodium is added to the curd/whey mixture to impede syneresis of the curd.

DETAILED DESCRIPTION According to one embodiment of this invention, the following method of manufacture is provided:

Milk is standardised to a low fat content in the range of 0.3 to 1.5%, preferably 0.4 to 0.5%, depending on the desired fat content of the cheese. The milk is then pasteurised at temperatures in the range of about 72 C to

80 C maintained for 12 to 20 seconds. The milk is then cool down to a temperature of about 29 C to 32 C and the followin bacteriological cultures are then added to the milk in specified amounts and stirred in: ^' 0.5% to 3.0% normal cheese starter culture

0.1% to 1.0% selected strains of Lactobacillus buigaricus

0.1% to 1.0% selected strains of Streptococcus thermophilus 0.05% to 0.3% of selected strains of Lactobacillus casei.

Next, about 19 grams to 31 grams of liquid rennet per 100 litres of milk, or other coagulating enzymes are added and stirred in. The purpose of this step is to coagulate the milk within less than one hour.

The temperature of the milk is maintained at approximately the same level (29°C to 32°C) and the milk is allowed to coagulate. The coagulating process takes between 30 and 45 minutes. When the milk is firmly coagulated, ^" the curd is cut by mechanical means into cubes not exceeding 1.2 cm in either direction. When free whey

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appears, a sample is taken for acid determination. Usually at this stage, the acidity in terms of lactic acid is within the limits of 0.10% to 0.12%. This is accepted as a startin guideline for determination of acid development. The curd and whey are now subjected to agitation t aid moisture expulsion, and when the curd is sufficiently firm as judged by visual or other sensory tests such as squeezing in hand, the agitation is stopped and an amount of whey is drained off and replaced with hot water, its quantity and temperature depending on the desirable ultimate acidity and degree of shrinkage or syneresis of the curd required. This in turn determines the ultimate moisture content and mineral and acid equilibria in the finished cheese. For instance, it may be necessary to add water at up to about 54 C temperature to raise the curd/whey mixture to about 35 C. At the same time between 0.3% to 1.5% of salt (NaCl) by weight of the initial milk quantity is added, either directly to the curd and whey or dissolved in hot water. This step retards further shrinkage of the curd. Because of .the addition of water the lactic acid already produced is diluted and so is the lactose content. Acid development is therefore reduced and the ultimate pH level of the cheese is thus controlled, so that it does not fall below the value of 5.1. The ultimate pH of the cheese refers to its value three weeks after manufacture. This is an important factor in our method. If the pH at three weeks is less than 5.1, the product has a tough body, a tendency to have a paler/bleached appearance and an undesirable sour taste. Our method of manufacture here differs from other methods of manufacture of- cheeses mainly because the addition fat in other cheeses has the tendency to buffer the adverse effects mentioned above. For our low fat cheese, we effect tighter control of the relevant variables than for most other cheeses varieties. The maximum pH which is acceptable for ou product (at three weeks after manufacture) is 5.5. Typically we have 5.3 to 5.4. By way of comparison, the minimum/maximu pH figures acceptable for cheddar cheese are 4.9 and 5.5 with

a typical of 5 . 2 or 5. 3.

It is probably worth explaining that when the cur is initially in the whey, there is a development of acid.

When the whey is drained off and water added instead, there a dilution of this acidity but acid development continues so that, once again, acidity begins to rise. As soon as th curd has reached the desired temperature, say, within 30 mi from the addition of the hot water, all the free liquid

(whey/water mixture) is drained off. At this stage it is essential that the acidity of the whey/water mixture does n exceed significantly the acidity of the whey immediately af cutting. Otherwise the cheese may become too acid. From then onwards the separated curd is fused, subdivided, and either dry salted, hooped and pressed or hooped, pressed an salted by immersion in brine.

The finished cheese can be either waxed or packed in plastic film and then stored until it reaches the desire maturity.

A typical manufacturing schedule is as follows : 9000 litres skim milk containing 0.5% fat is inocculated with

109 litres Normal Starter 1.21%

23 litres selected strains of Streptococcus thermophilus 0.25% 23 litres selected strains of Lactobacillus buigaricus 0.25%

9 litres Lactobacillus casei 0.1%

Add 114 grams colour (Anattao) in 10 parts water

Set Vat with 2 Kilograms Rennett Allow to coagulate in 35 to 50 minutes

Cut curd gently

Let stand for 5 minutes

Slowly stir for about 10 minutes

Stop stirring and allow curd to settle Pump half whey off

Add 45 kg salt

Stir for 10 minutes

Add water at 37°C - bring level to 10,000 litres Stir for about 10 minutes Pump out and drain free whey from curd Cheddar for 20 minutes Mill and Salt

It is reiterated that an essential feature of thi invention is the use of a culture of Lactobacillus casei, which, because of its ability to* break the casein micelle down into its components, alters the consistency (body) of the cheese from rubbery hard to pliable soft.

It may be desirable in the case of some consumers to provide cheese with a stronger flavour of the type en¬ countered in Parmesan or Romano cheese varieties. To meet such a demand a lipolytic activity in the cheese can be ensured by the addition of about 1.5 grams to 6 grams of a lipase enzyme preparation obtained from lamb or kid salivary glands per 100 litres of milk. Enzyme preparations of this kind are already used in cheese manufacture.

An embodiment of the invention described above applies to cheese varieties of the cheddar type. In the cas of other varieties such as Gouda, Edam, Port du Salut and Bel Paese, instead of separating the curd from the whey/wate mixture, the curd is compressed under this whey/water mixtur into a solid mass. The consolidated fused curd mass is then cut into portions suitable for moulding, pressing, and then salting in brine as individual cheeses.

In the case of other varieties for example, Tilsit the curd is separated from the whey/water mixture and is thereafter treated as appropriate for such variety. In the method of manufacture of the present invention we allow for very little acid development to take place. We also treat the curd at relatively low temperature (not exceeding 38 C) and we replace some calcium ions by monovalent ions (e.g. sodium) which, being monovalent chemically, have no bridging (shrinking) properties of the curd.

In the process of manufacturing cheese, it is normal to add salt (NaCl) for purposes of flavour. There are several techniques for adding salt including brine salti dry salting, etc. However, it is important to note that in our manufacturing method, the reason for adding salt to the curd in the whey is not for purposes of flavour but to obtai the required ion exchange. The purpose of this ion exchange is to disrupt bridges between casein micelles, thereby limiting the contraction of the casein network and, thus, the contraction of the curd.

It should be noted that it is not necessary to add salt in the form of NaCl. Indeed, it is possible at this stage to add any monovalent ion (obviously it must be a permissible food additive)which will displace the divalent calcium cation associated with the casein of the milk.

We pre er to use NaCl because:

- It is a monovalent ion.

- It is a permitted food additive.

- It is readily available. - It is inexpensive.

- It has some affect in reducing the amount of salt which is required to be added later for flavour purposes.